Image forming apparatus

Abstract

To adjust an image forming position with high accuracy.SOLUTION: An image forming apparatus comprises: image forming means that forms an image on a sheet on the basis of an image forming condition; conveying means that conveys the sheet in a conveyance direction; measuring means that measures a length of the sheet in the conveyance direction; reading means that reads the sheet; and control means that causes the image forming means to form an adjustment pattern on the sheet, and generates the image forming condition on the basis of a result of reading of the adjustment pattern performed by the reading means, a first target value of a first distance in the conveyance direction from a leading end in the conveyance direction of the sheet on which the adjustment pattern is formed to an image forming area, and a second target value of a second distance in the conveyance direction from a rear end in the conveyance direction of the sheet on which the adjustment pattern is formed to the image forming area. The control means determines at least one of the first target value and the second target value on the basis of a measured value of the sheet on which the adjustment pattern is formed from the measuring means.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a technique for adjusting the image formation position on a sheet.

Background Art

[0002] In an image forming apparatus, it may be required to accurately control the image formation position (printing position) on a sheet. Further, when printing images on both sides of a sheet, it may be required to control so that there is no deviation in the image formation positions on the front surface (first surface) and the back surface (second surface) of the sheet. Controlling so that there is no deviation in the image formation positions on the front and back surfaces of the sheet is also called "front-back registration".

[0003] Patent Document 1 discloses a configuration in which a specific pattern is formed on a sheet and the image formation position on the sheet is controlled based on the reading result of the specific pattern formed on the sheet. Further, Patent Document 2 discloses a configuration in which an image formed on a sheet is read by an image sensor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, when using a cut sheet, the size of the cut sheet may vary from the target value (nominal value) depending on the cutting accuracy. Further, the size of the sheet may also vary depending on the fixing process of the image on the sheet. When the size of the sheet on which a specific pattern for adjusting the image formation position is formed is different from its nominal value, the image formation position cannot be adjusted with high accuracy.

[0006] The object of the present invention is to accurately adjust the image forming position.

Means for Solving the Problem

[0007] According to one aspect of the present invention, an image forming apparatus includes: an image forming unit that forms an image on a sheet based on image forming conditions; a conveyance unit that conveys the sheet along a conveyance direction; a measurement unit that measures the length of the sheet in the conveyance direction; a reading unit that reads the sheet; a control unit that forms an adjustment pattern on the sheet by the image forming unit, and generates the image forming conditions based on a reading result of the adjustment pattern by the reading unit, a first target value of a first distance in the conveyance direction from a leading end of the sheet on which the adjustment pattern is formed to an image forming area where an image is formed on the sheet by the image forming unit, and a second target value of a second distance in the conveyance direction from a trailing end of the sheet on which the adjustment pattern is formed to the image forming area, wherein the control unit determines at least one of the first target value and the second target value based on a measurement value obtained by the measurement unit of the sheet on which the adjustment pattern is formed.

Advantages of the Invention

[0008] According to the present invention, the image forming position can be accurately adjusted.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0011] Note that, hereinafter, embodiments will be described using an electrophotographic image forming apparatus, but the disclosed content is also applicable to other types of image forming apparatuses such as an inkjet system.

[0012] FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 includes a printer unit 101, an operation unit 180, an adjustment unit 200, and a post-processing unit 600. Although not shown in FIG. 1, the image forming apparatus 100 has a controller 103 (FIG. 6) that controls the entire image forming apparatus 100, and an engine control unit 312 (FIG. 6) that controls each member shown in FIG. 1 under the control of the controller 103 to control image formation on a sheet. The operation unit 180 has a key button, a touch panel, etc., and provides a user interface.

[0013] The printer unit 101 forms an image on a sheet based on image data. The printer unit 101 has four image forming units 120, 121, 122, and 123 that form images for each color component. The image forming units 120 to 123 form yellow, magenta, cyan, and black images, respectively. Since the image forming units 120 to 123 have the same configuration except for the color of the toner used for image formation, the configuration of the image forming unit 120 that forms a yellow image will be described below as a representative.

[0014] The photosensitive drum 105 is rotationally driven in the counterclockwise direction in the figure during image formation. The charger 111 charges the photosensitive drum 105. The scanning unit 107 forms an electrostatic latent image on the photosensitive drum 105 by scanning the photosensitive drum 105 with laser light based on the image data. The scanning unit 107 includes a light source 108 that emits laser light and a polygon mirror 109 that reflects the laser light emitted by the light source 108 toward the photosensitive drum 105 and moves the laser light in the main scanning direction on the photosensitive drum 105. The main scanning direction is a direction parallel to the rotation axis of the photosensitive drum 105. Also, the circumferential direction of the photosensitive drum 105 is referred to as the sub-scanning direction. The sub-scanning direction is a direction orthogonal to the main scanning direction. The developing unit 112 develops the electrostatic latent image on the photosensitive drum 105 with yellow toner to form an image of yellow toner on the photosensitive drum 105. The image formed on the photosensitive drum 105 is transferred to the intermediate transfer belt 106. By overlapping and transferring the yellow, magenta, cyan, and black images formed on the photosensitive drums 105 of the four image forming units 120 to 123 to the intermediate transfer belt 106, colors different from yellow, magenta, cyan, and black can be reproduced.

[0015] The intermediate transfer belt 106 is rotationally driven in the clockwise direction in the figure during image formation. Therefore, the image transferred to the intermediate transfer belt 106 is conveyed to the position opposite to the secondary transfer roller 114. The secondary transfer roller 114 transfers the image of the intermediate transfer belt 106 to the sheet 300 fed into the conveyance path from the cassette 113A or 113B and conveyed along the conveyance path. The detection result of the sheet 300 by the registration sensor 116 is used to adjust the timing of feeding the sheet 300 to the position opposite to the secondary transfer roller 114.

[0016] The sheet 300 with the image transferred thereon is conveyed to the fixing devices 150 and 160. The fixing devices 150 and 160 fix the image on the sheet 300 by heating and pressing the sheet 300 with the image transferred thereon. The fixing device 150 includes a fixing roller 151 provided with a heater and a pressure belt 152 that presses the sheet 300 against the fixing roller 151. The fixing device 160 is disposed downstream of the fixing device 150 in the conveyance direction of the sheet 300. The fixing device 160 includes a fixing roller 161 provided with a heater and a pressure roller 162 that presses the sheet 300 against the fixing roller 161. Depending on the type of the sheet 300, etc., the fixing process by the fixing device 160 may not be necessary. When the fixing process by the fixing device 160 is not necessary, the sheet 300 that has passed through the fixing device 150 is guided to the conveyance path 130 by the flapper 131.

[0017] The flapper 132 is a guiding member that switches between guiding the sheet 300 to the conveyance path 135 and guiding it to the conveyance path 139. When discharging the sheet 300 with an image formed on one side face-up or when forming images on both sides and the sheet 300 with images formed on both sides, the sheet 300 is guided to the conveyance path 139. On the other hand, when discharging the sheet 300 with an image formed on one side face-down or when forming images on both sides and the sheet 300 with an image formed on one side, the sheet 300 is guided to the conveyance path 135. The sheet 300 guided to the conveyance path 135 is conveyed to the inversion unit 136, and when the inversion sensor 137 detects the trailing edge of the sheet 300, the conveyance direction of the sheet 300 is reversed.

[0018] The flapper 133 is a guiding member that switches to guide the sheet 300 conveyed to the reversing portion 136 either to the conveyance path 138 or to the conveyance path 135. When discharging face down, the sheet 300 is conveyed back to the conveyance path 135 and is guided to the conveyance path 139 by the flapper 134. On the other hand, when forming images on both sides, the sheet 300 on which image formation on one side has been performed is conveyed along the conveyance path 138 to the position opposite the secondary transfer roller 114 again, and image formation on the other side of the sheet 300 is performed.

[0019] The sheet 300 guided to the conveyance path 139 is conveyed to the adjustment unit 200. FIG. 2 is a schematic cross-sectional view of the adjustment unit 200. The sheet 300 conveyed to the adjustment unit 200 first passes through a measurement unit 500 that measures the length LP in the conveyance direction of the sheet 300. The sheet 300 that has passed through the measurement unit 500 is guided by the flapper 221 to the through path 230 or the measurement path 231. In the present embodiment, when the position adjustment process described later is not performed, the sheet 300 is guided to the through path 230, and when the position adjustment process is performed, the sheet 300 is guided to the measurement path 231. The sheet 300 guided to the measurement path 231 is optically read by the reading unit 700. The sheet 300 that has passed through the through path 230 or the measurement path 231 is conveyed to the post-processing unit 600 via the discharge path 232. Note that the measurement unit 500 measures the length LP in the conveyance direction of the sheet 300 when performing the position adjustment process. A plurality of rollers are provided along the through path 230, the measurement path 231, and the discharge path 232 for conveying the sheet 300. In the post-processing unit 600, post-processing such as alignment processing, stapling processing, and cutting processing is performed as necessary, and then the sheet 300 is discharged to the outside of the image forming apparatus 100.

[0020] Next, the measurement unit 500 will be described. FIG. 3 is a configuration example of the measurement unit 500 and an explanatory diagram of its operation. The sheet 300 is conveyed in the conveyance direction by conveyance rollers 511 and 512 as conveyance means. In FIG. 3, the conveyance direction is the direction from the right side to the left side. The measurement unit 500 has an optical sensor 501 provided between the conveyance rollers 511 and 512 in the conveyance direction, that is, a non-contact sensor. The optical sensor 501 has a light source that emits light toward the conveyance path of the sheet and a light receiving element that receives the light.

[0021] When the sheet 300 is at the detection position 502 of the optical sensor 501, the optical sensor 501 is configured such that the reflected light of the light emitted by the light source of the optical sensor 501 enters the light receiving element of the optical sensor 501. On the other hand, when the sheet 300 is not at the detection position 502 of the optical sensor 501, the optical sensor 501 is configured such that the light incident on the light receiving element of the optical sensor 501 is at least a predetermined amount less than when the sheet 300 is at the detection position of the optical sensor 501. Therefore, the optical sensor 501 can determine whether or not the sheet 300 is at the detection position 502 based on the amount of light received by the light receiving element. The measurement unit 500 outputs a detection result of the sheet 300, that is, a signal indicating whether or not the sheet 300 is being detected, to the controller 103.

[0022] FIGS. 3(A) to 3(C) show states in which the leading end, the center, and the trailing end in the conveyance direction of the sheet 300 being conveyed at the conveyance speed S have reached the detection position 502, respectively. By measuring the period (time) T during which the optical sensor 501 detects the reflected light from the sheet 300, that is, the period T from the state of FIG. 3(A) to the state of FIG. 3(C), the controller 103 can determine the length LP in the conveyance direction of the sheet 300 as T×S. Note that a configuration may also be adopted in which the light source and the light receiving element are provided at positions opposite to each other with respect to the sheet 300, and it is determined whether or not the sheet 300 is at the detection position 502 based on whether or not the light receiving element receives the light from the light source.

[0023] Also, in FIG. 3, a non-contact sensor is used to detect the length LP in the sheet conveyance direction, but a configuration using a contact sensor to detect the length LP in the sheet conveyance direction may also be employed. Specifically, instead of the optical sensor 501 in FIG. 3, a flag is provided such that when the sheet 300 is at the detection position 502, it is in the first position, and when the sheet 300 is not at the detection position 502, it is in the second position. Then, by measuring the period T during which the flag is in the first position, the controller 103 can obtain the length LP in the conveyance direction of the sheet 300 as T×S.

[0024] FIG. 4 shows another configuration example of the measurement unit 500. In the configuration of FIG. 3, the position of the optical sensor 501 was fixed, and the length LP in the conveyance direction of the sheet 300 was measured by conveying the sheet 300. In the configuration example of FIG. 4, the optical sensor 501 is configured to be movable in the conveyance direction. In the configuration example of FIG. 4, when measuring the length LP in the conveyance direction of the sheet 300, the optical sensor 501 is moved at a predetermined moving speed S in the moving direction opposite to the conveyance direction of the sheet 300. Also, in the configuration example of FIG. 4, when measuring the length LP in the conveyance direction of the sheet 300, the conveyance of the sheet 300 is stopped. FIG. 4(A) shows a state where the detection position 502 of the optical sensor 501 has reached the leading end in the conveyance direction of the sheet 300, and FIG. 4(B) shows a state where the detection position 502 of the optical sensor 501 has reached the trailing end in the conveyance direction of the sheet 300. By measuring the period T from the state of FIG. 4(A) to the state of FIG. 4(B), the controller 103 can obtain the length LP in the conveyance direction of the sheet 300 as T×S.

[0025] In the width direction orthogonal to the conveyance direction of the sheet 300, since the positions where the conveyance rollers 511 and 512 are provided are different from the position where the optical sensor 501 is provided, the optical sensor 501 does not interfere with the conveyance rollers 511 and 512 even if the optical sensor 501 is moved in the moving direction. Also, in FIG. 4, when measuring the length LP in the conveyance direction of the sheet 300, the moving direction of the optical sensor 501 is opposite to the conveyance direction of the sheet, but the moving direction of the optical sensor 501 may be the same as the conveyance direction of the sheet. Further, in FIG. 4, the conveyance of the sheet 300 is stopped and the optical sensor 501 is moved, but a configuration may be adopted in which the optical sensor 501 is moved in a direction opposite to the conveyance direction of the sheet 300 while the sheet 300 is being conveyed. In this case, assuming that the conveyance speed of the sheet 300 is S1, the moving speed of the optical sensor 501 is S2, and the period during which the optical sensor 501 detects the sheet 300 is T, the length LP in the conveyance direction of the sheet 300 is obtained as (S1 + S2) × T.

[0026] FIG. 5 is a schematic configuration diagram of the reading unit 700. In the reading unit 700, the sheet 300 is conveyed by the conveyance rollers 211, 212, and 213. The reading unit 700 includes contact image sensors (CIS) 701 and 702 that optically read the sheet 300. The CIS 702 reads the second surface of the sheet through the glass 704 between the conveyance rollers 211 and 212. On the side opposite to the glass 704 with respect to the conveyance path of the sheet 300, a black backing roller 706 for clarifying the contrast with the end of the sheet 300 is arranged. The CIS 701 reads the first surface of the sheet through the glass 703 between the conveyance rollers 212 and 213. On the side opposite to the glass 703 with respect to the conveyance path of the sheet 300, a black backing roller 705 for clarifying the contrast with the end of the sheet 300 is arranged.

[0027] CISs 702 and 703 include a light source that irradiates light over the entire width direction orthogonal to the sheet conveyance direction, a line sensor that receives the reflected light from the sheet, and an optical member for causing the reflected light from the sheet to enter each light receiving element of the line sensor. The line sensor reads an image of one line in the width direction of the sheet 300 by receiving the reflected light from the sheet 300. While the sheet 300 is being conveyed, by repeating the reading of one line in the width direction of the sheet 300, CISs 702 and 703 optically read the entire second surface and the entire first surface of the sheet 300.

[0028] FIG. 6 is a control configuration diagram of the image forming apparatus 100. The controller 103 controls the entire image forming apparatus 100. The storage unit 900 is composed of, for example, a volatile memory and a non-volatile memory, and stores data and control programs used by the controller 103 in its control. The controller 103 has one or more processors (not shown), and by executing the control program stored in the storage unit 900 by the one or more processors, the correction unit 320 and the processing unit 321 shown in FIG. 6 are realized.

[0029] The processing unit 321 creates geometric correction information in the position adjustment process described later and stores it in the storage unit 900. FIG. 7 shows an example of the geometric correction information. "Sheet type" is information regarding the type of the sheet 300, and includes, for example, information on "sheet name", "size", "basis weight", "surface property", and "color". "Sheet name" indicates the name given to the sheet 300 to identify it. "Size" indicates the size of the sheet 300, for example, the nominal value of the length of the long side and the nominal value of the length of the short side. When the sheet is a standard size such as A4 size or A3 size, "size" can be indicated by the standard size. "Basis weight", "surface property", and "color" indicate the basis weight, surface property, and color of the sheet 300, respectively.

[0030] "Orientation" indicates the orientation of the sheet when transporting the sheet. When transporting the long side of sheet 300 parallel to the transport direction, "vertical" is set for the "orientation". Also, when transporting the short side of sheet 300 parallel to the transport direction, "horizontal" is set for the "orientation". Based on the "sheet type" and the "orientation", the nominal value (reference value) of the length LP in the transport direction of sheet 300 is determined. For example, when transporting sheet 300 named S#1 in the vertical orientation, the nominal value of the length LP in the transport direction of sheet 300 is Ll, and when transporting it in the horizontal orientation, the nominal value of the length LP in the transport direction of sheet 300 is Ls.

[0031] The "first side" of the "adjustment amount" is a parameter for adjusting the image formation position on the first side (front surface) of sheet 300. The "second side" of the "adjustment amount" is a parameter for adjusting the image formation position on the second side (back surface) of sheet 300. According to FIG. 7, the parameters for adjusting the image formation position include the "lead position", "side position", "main scanning magnification", and "sub-scanning magnification". The "lead position" is a parameter for adjusting the image formation position in the transport direction of sheet 300. When the lead position is X, the image formation position in the transport direction is shifted X from the reference position to the rear end side of sheet 300. The "side position" is a parameter for adjusting the image formation position in the width direction of sheet 300. When the side position is X, the image formation position at the left end of sheet 300 in the transport direction is shifted X to the right from the reference position. The "main scanning magnification" is a parameter for adjusting the size of the image in the main scanning direction. Note that the main scanning direction corresponds to the width direction in sheet 300. When the main scanning magnification is X%, the image size in the width direction is enlarged by X% from the reference size. The "sub-scanning magnification" is a parameter for adjusting the size of the image in the sub-scanning direction. Note that the sub-scanning direction corresponds to the transport direction of sheet 300. When the sub-scanning magnification is X%, the image size in the transport direction is enlarged by X% from the reference size. Note that the parameters included in the geometric correction information in FIG. 7 are examples, and the parameters included in the geometric correction information are not limited to those shown in FIG. 7.

[0032] Returning to FIG. 6, when forming on the sheet 300 based on the image data, the correction unit 320 refers to the geometric correction information to obtain an adjustment amount corresponding to the type and orientation of the sheet 300 and the surface of the sheet 300 on which the image is formed. Then, the correction unit 320 controls the engine control unit 312 based on the obtained adjustment amount so that the image formation position of the sheet 300 becomes the target position, and forms an image on the sheet 300. In this way, by forming an image on the sheet 300 based on the geometric correction information, the image formation position can be accurately approximated to the target position. The geometric correction information is an image formation condition for adjusting or controlling the image formation position.

[0033] Subsequently, the position adjustment process for generating the geometric correction information will be described. FIG. 8 shows an example of a position adjustment pattern formed on the sheet 300 for the position adjustment process. In the following description, the leading end and the trailing end in the conveyance direction are simply referred to as the "leading end" and the "trailing end". Also, in the following description, "right" and "left" mean the right and left when viewed in the conveyance direction. The position adjustment pattern is formed in a region different from the image formation region 310 where the user image is formed on the sheet 300 when the user executes a print job involving the position adjustment process via the operation unit 180. Note that the user image means an image that the user forms on the sheet 300. In the example of FIG. 8, the position adjustment pattern includes marks 820, 821, 822, and 823.

[0034] The distance L#1 from the leading edge of the sheet 300 to the image forming area 310 on the left side of the sheet 300 and the distance L#5 from the left end of the sheet 300 on the leading edge side of the sheet 300 to the image forming area 310 are measured by the mark 820. The distance L#1 and the distance L#5 correspond to the position of the corner on the left leading edge side of the image forming area 310. The distance L#2 from the leading edge of the sheet 300 to the image forming area 310 where an image is formed on the sheet on the right side of the sheet 300 and the distance L#6 from the right end of the sheet 300 on the leading edge side of the sheet 300 to the image forming area 310 are measured by the mark 821. The distance L#2 and the distance L#6 correspond to the position of the corner on the right leading edge side of the image forming area 310. The distance L#3 from the trailing edge of the sheet 300 to the image forming area 310 on the left side of the sheet 300 and the distance L#7 from the left end of the sheet 300 on the trailing edge side of the sheet 300 to the image forming area 310 are measured by the mark 822. The distance L#3 and the distance L#7 correspond to the position of the corner on the left trailing edge side of the image forming area 310. The distance L#4 from the trailing edge of the sheet 300 to the image forming area 310 on the right side of the sheet 300 and the distance L#8 from the right end of the sheet 300 on the trailing edge side of the sheet 300 to the image forming area 310 are measured by the mark 823. The distance L#4 and the distance L#8 correspond to the position of the corner on the right trailing edge side of the image forming area 310.

[0035] Note that the position adjustment pattern shown in FIG. 8 is formed on the surface of the sheet 300 on the side where the position adjustment is performed. That is, when adjusting the image forming position on the first surface, the position adjustment pattern shown in FIG. 8 is formed on the first surface of the sheet 300. Also, when adjusting the image forming position on both the first surface and the second surface, the position adjustment pattern shown in FIG. 8 is formed on the first surface and the second surface of the sheet 300.

[0036] The processing unit 321 acquires the reading result of the position adjustment pattern by the reading unit 700, and determines the distances L#1 to L#8 in FIG. 8, that is, at which positions of the sheet 300 the four corners of the image forming area 310 are formed. Then, based on the distances L#1 to L#8 and the lengths LP and WP (FIG. 8) in the conveyance direction and width direction of the sheet 300, the processing unit 321 generates the geometric correction information shown in FIG. 7 so that the user image is formed in the image forming area 310 without distortion.

[0037] For example, an A3-size sheet 300 is conveyed in the longitudinal direction, that is, so that the long side is parallel to the conveyance direction, and as shown in FIG. 9(A), the length LI in the conveyance direction of the image forming area 310 is adjusted to be 400 mm. In this case, the target values of the distances L#1 to L#4 are each set to 10 mm, and based on the measured values of the distances L#1 to L#4, an adjustment amount is obtained so as to bring the distances L#1 to L#4 closer to the target values, whereby the length LI in the conveyance direction of the image forming area 310 can be made 400 mm.

[0038] However, in the case of a cut sheet, due to cutting errors or the like, the length LP in the conveyance direction of the sheet 300 may be different from its nominal value. Further, the length LP of the sheet 300 may vary from the nominal value also due to the expansion and contraction of the sheet 300 during the fixing process in the fixing units 150 and 160. For example, as shown in FIG. 9(B), when the actual length LP of the sheet 300 is 421 mm, if an adjustment amount is obtained so as to bring the distances L#1 to L#4 closer to the target value of 10 mm, the length LI in the conveyance direction of the image forming area 310 becomes 401 mm, and the length in the conveyance direction of the image forming area 310 expands. Therefore, the user image formed in the image forming area 310 also expands in the conveyance direction.

[0039] Therefore, in this embodiment, target values of distances L#1 to L#4 are determined based on the measured value of the length LP in the conveyance direction of the sheet 300 measured by the measurement unit 500. For example, as shown in FIG. 10, when the measured value of the length LP in the conveyance direction of the sheet 300 is 421 mm, in order to make the length LI in the conveyance direction of the image forming area 310 400 mm, the target values of distances L#1 to L#4 may each be set to 10.5 mm. By setting the target values of distances L#1 to L#4 in this way, as shown in FIG. 10, the length LI in the conveyance direction of the image forming area 310 can be made the target value of 400 mm.

[0040] FIG. 11 is a flowchart of the position adjustment process. The position adjustment process is also a process of generating or updating geometric correction information. As described above, in this embodiment, the position adjustment process is performed together with the formation process of the user image based on the print job. FIG. 12 shows an example of a setting screen for executing the position adjustment process. For example, the user can select the sheet type and orientation for generating geometric correction information by operating the position adjustment button 1002 on the screen of FIG. 12 displayed on the operation unit 180. After that, when a print job for forming a user image with the sheet type and orientation selected on the screen of FIG. 12 is started, the process of FIG. 11 is started.

[0041] In the following description, the distances L#1 and L#2 in FIG. 8 are collectively referred to as the "first distance", and the distances L#3 and L#4 are collectively referred to as the "second distance". The first distance is the distance in the conveyance direction from the leading end of the sheet 300 in the conveyance direction to the image forming area 301, and the second distance is the distance in the conveyance direction from the trailing end of the sheet 300 in the conveyance direction to the image forming area 301. Similarly, in the following description, the distances L#5 and L#7 are collectively referred to as the "third distance", and the distances L#6 and L#8 are collectively referred to as the "fourth distance". The third distance is the distance in the width direction from the left end of the sheet 300 to the image forming area 301, and the fourth distance is the distance in the width direction from the right end of the sheet 300 to the image forming area 301.

[0042] Furthermore, as described with reference to FIGS. 9 and 10, this embodiment suppresses fluctuations in the length LI in the conveyance direction of the image forming region 301 due to fluctuations in the length LP in the conveyance direction of the sheet 300. Therefore, the following description will focus on the processing of the length in the conveyance direction.

[0043] In S10 of FIG. 11, the controller 103 acquires the sheet type and the conveyance direction. The controller 300 determines the length LI in the conveyance direction of the image forming region 301 based on the sheet type and the conveyance direction. Note that information indicating the relationship between the combination of the sheet type and the conveyance direction and the length LI in the conveyance direction of the image forming region 301 is stored in advance in the storage unit 900. For example, as shown in FIG. 9(A), when the A4-size sheet 300 is conveyed in the vertical direction, the length LI in the conveyance direction of the image forming region 301 is determined to be 400 mm based on the information stored in the storage unit 900.

[0044] In S11, the controller 103 forms the user image and the position adjustment pattern on the sheet 300 using the geometric correction information corresponding to the combination of the sheet type and the conveyance direction stored in the storage unit 900. The sheet 300 on which the image is formed is conveyed to the adjustment unit 200.

[0045] In S12, the processing unit 321 acquires the measured value of the length LP in the conveyance direction of the sheet 300 based on the detection result of the sheet 300 by the measurement unit 500. In S13, the processing unit 321 determines the first target value of the first distance and the second target value of the second distance based on the measured length LP in the conveyance direction of the sheet 300 and the length LI in the conveyance direction of the image forming region 301 determined in S10.

[0046] As an example, a ratio between a first target value and a second target value is set in the processing unit 321, and the processing unit 321 determines the first target value and the second target value by distributing the difference between the length LP and the length LI to the first target value and the second target value based on the set ratio. For example, in the example of FIG. 10, the difference between the length LP and the length LI is 21 mm. Therefore, by distributing the 21-mm difference to the first target value and the second target value so that the ratio between the first target value and the second target value is 1:1, as shown in FIG. 10, the first target value and the second target value are determined to be 10.5 mm. Note that the ratio between the first target value and the second target value is, for example, set in advance by the user. Also, for example, the ratio between the first target value and the second target value can be determined based on the combination of the sheet type and the conveyance direction. In this case, information indicating the relationship between the combination of the sheet type and the conveyance direction and the ratio between the first target value and the second target value is stored in advance in the storage unit 900. Then, the processing unit 321 determines the ratio between the first target value and the second target value based on the combination of the sheet type and the conveyance direction acquired in S10 and the information stored in the storage unit 900.

[0047] Also, the processing unit 321 can be configured such that for one of the values of the first target value and the second target value, it is a constant value, and the other value of the first target value and the second target value is determined based on the difference between the length LP and the length LI. As an example, if the first target value is set to be constant at 10 mm, when the difference between the length LP and the length LI is 21 mm, the second target value is 11 mm obtained by subtracting the first target value of 10 mm from the difference. Note that when one of the first target value and the second target value is a constant value, the constant value can be set in advance by the user. Alternatively, the constant value can be determined based on the combination of the sheet type and the conveyance direction acquired in S10. In this case, information indicating the relationship between the combination of the sheet type and the conveyance direction and one of the values of the first target value and the second target value is stored in advance in the storage unit 900. Then, the processing unit 321 determines one of the values of the first target value and the second target value based on the combination of the sheet type and the conveyance direction acquired in S10 and the information stored in the storage unit 900.

[0048] In S14, the processing unit 321 determines distances L#1 to L#8 by obtaining the reading result of the position adjustment pattern by the reading unit 700. In S15, the processing unit 321 generates geometric correction information for the sheet 300 based on the reading result by the reading unit 700, that is, the determination values of distances L#1 to L#8 and the target values of the first distance to the fourth distance, and stores it in the storage unit 900.

[0049] In S16, the controller 103 determines whether the image formation in the print job has ended. If the image formation has ended, the controller 103 ends the process of FIG. 11. On the other hand, if the image formation in the print job has not ended, the controller 103 repeats the process from S11. Note that the geometric correction information used in the image formation in S11 after the repetition uses the one generated in the previous S15.

[0050] Although not specified in the flowchart of FIG. 11, the length WI in the width direction of the image formation area 301 can be determined based on the sheet type and the conveyance direction obtained in S10. In this case, information indicating the relationship between the combination of the sheet type and the conveyance direction and the length WI in the width direction of the image formation area 301 is stored in advance in the storage unit 900. Further, the target values of the third distance and the fourth distance in the width direction are also determined based on, for example, the combination of the sheet type and the conveyance direction obtained in S10. In this case, information indicating the relationship between the combination of the sheet type and the conveyance direction and the target values of the third distance and the fourth distance is stored in advance in the storage unit 900.

[0051] Alternatively, the target values of the third distance and the fourth distance in the width direction can be determined based on the measured value of the length WP of the sheet 300 in the width direction. Specifically, since the reading unit 700 reads the entire width direction of the sheet 300, the controller 103 can obtain the measured value of the length WP of the sheet 300 in the width direction based on the reading result of the reading unit 700. Then, similar to the first target value of the first distance and the second target value of the second distance, based on the difference between the measured value of the length WP of the sheet 300 in the width direction and the length WI of the image forming area 301 in the width direction, the target values of both the third distance and the fourth distance, or one of them, are determined. When determining the target values of both the third distance and the fourth distance, the ratio of the two target values can be determined based on the sheet type and the conveyance direction. Also, when determining one of the target values of the third distance and the fourth distance, the other target value can be determined based on the sheet type and the conveyance direction.

[0052] Also, in the process of FIG. 11, the geometric correction information was updated each time an image was formed on one sheet 300, but it is also possible to adopt a configuration in which the geometric correction information is updated each time an image is formed on N sheets (N is an integer of 2 or more) of the sheet 300. In this case, the geometric correction information can be created by averaging the N adjustment amounts obtained in the N image formations. Further, in the present embodiment, the position adjustment process is performed in combination with the formation process of the user image, but it is also possible to adopt a configuration in which only the position adjustment process is performed alone. In this case, only the position adjustment pattern is formed on the sheet 300, and the geometric correction information is created.

[0053] Furthermore, in the above description, the distances L#1 and L#2 were collectively referred to as the "first distance", and the distances L#3 and L#4 were collectively referred to as the "second distance". This was because it was premised that the target values of the distances L#1 and L#2 were the same value, and the target values of the distances L#3 and L#4 were the same value. However, a configuration in which the target values of the distances L#1 and L#2 are different values and the target values of the distances L#3 and L#4 are different values may also be acceptable. In this case, the target values of the distances L#1 and L#3 are determined based on the difference between the length LP and the length LI, in the same manner as the first target value of the first distance and the second target value of the second distance described above. Also, the target values of the distances L#2 and L#4 are determined based on the difference between the length LP and the length LI, in the same manner as the first target value of the first distance and the second target value of the second distance described above. However, the target value of the distance L#1 and the target value of the distance L#2 may be different, and the target value of the distance L#3 and the target value of the distance L#4 may be different. The same applies to the distances L#5 to L#8 in the width direction.

[0054] Also, in the above embodiment, the positions of the four corners of the image formation region 310 were determined by the adjustment pattern, and geometric correction information was generated so as to bring these four corners closer to the target values. That is, the length LI in the conveyance direction and the length WI in the width direction of the image formation region 310 were used as the target values. However, in order to suppress fluctuations in the length of the user image in the conveyance direction, the concept of the above embodiment can also be applied to control in which only the length LI from the front end to the rear end in the conveyance direction of the image formation region 310 is used as the target value. In this case, the adjustment pattern is a pattern for determining the first distance and the second distance, and the processing unit 321 determines only the first target value of the first distance and the second target value of the second distance based on the difference between the length LP and the length LI, and determines the adjustment amount.

[0055] As described above, a measuring unit 500 for measuring the length LP in the conveyance direction of the sheet 300 is provided, and at least one of the first target value and the second target value is set based on the measured value of the length LP by the measuring unit 500. With this configuration, even if the length LP in the conveyance direction of the sheet 300 is different from the nominal value, it is possible to suppress deterioration in the adjustment accuracy of the image formation position.

[0056] [Other Embodiments] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0057] The invention is not limited to the above-described embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, the claims are attached to disclose the scope of the invention.

Description of Reference Numerals

[0058] 101: Printer unit, 500: Measurement unit, 700: Reading unit, 103: Controller

Claims

1. Image forming means for forming an image on a sheet based on image forming conditions; Conveying means for conveying the sheet along the conveying direction; Measuring means for measuring the length of the sheet in the conveying direction; Reading means for reading the sheet; A control means for forming an adjustment pattern on the sheet by the image forming means, generating the image forming conditions based on the reading result of the adjustment pattern by the reading means, a first target value of a first distance in the conveying direction from a leading end of the sheet in the conveying direction on which the adjustment pattern is formed to an image forming area where an image is formed on the sheet by the image forming means, and a second target value of a second distance in the conveying direction from a trailing end of the sheet in the conveying direction on which the adjustment pattern is formed to the image forming area; Comprising; The control means determines at least one of the first target value and the second target value based on a measured value by the measuring means of the sheet on which the adjustment pattern is formed. An image forming apparatus.

2. The control means determines at least one of the first target value and the second target value based on a difference between the length of the image forming area in the conveying direction and the measured value. The image forming apparatus according to Claim 1.

3. The control means determines the length of the image forming area in the conveying direction based on the type of the sheet and the orientation of the sheet when the sheet is conveyed. The image forming apparatus according to Claim 2.

4. The control means determines the first target value and the second target value by distributing the difference to the first target value and the second target value based on a ratio between the first target value and the second target value. The image forming apparatus according to Claim 2.

5. The control means determines the ratio between the first target value and the second target value based on the type of the sheet and the orientation of the sheet when the sheet is conveyed. The image forming apparatus according to Claim 4.

6. The control means determines one of the first target value and the second target value by subtracting the other value of the first target value and the second target value from the difference. The image forming apparatus according to Claim 2.

7. The control means determines the other value of the first target value and the second target value based on the type of the sheet and the orientation of the sheet when the sheet is conveyed. The image forming apparatus according to Claim 6.

8. The control means further generates the image forming conditions based on a third target value of a third distance in the width direction orthogonal to the conveyance direction from one of two sides parallel to the conveyance direction of the sheet on which the adjustment pattern is formed to the image forming area, and a fourth target value of a fourth distance in the width direction from the other of the two sides parallel to the conveyance direction of the sheet on which the adjustment pattern is formed to the image forming area. The image forming apparatus according to claim 1.

9. The adjustment pattern is a pattern for determining the first distance, the second distance, the third distance, and the fourth distance. The control means generates the image forming conditions so as to bring the first distance, the second distance, the third distance, and the fourth distance determined based on the reading result of the adjustment pattern closer to the first target value, the second target value, the third target value, and the fourth target value. The image forming apparatus according to claim 8.

10. The adjustment pattern is formed in an area of the sheet different from the image forming area. The image forming apparatus according to claim 1.

11. The control means forms the adjustment pattern on the sheet together with the image by controlling the image forming means. The image forming apparatus according to claim 10.

12. The image forming means includes a fixing means for fixing the image on the sheet. The measuring means measures the length of the sheet in the conveyance direction downstream of the fixing means in the conveyance direction. The image forming apparatus according to claim 1.

13. The reading means reads the sheet downstream of the measuring means in the conveyance direction. The image forming apparatus according to claim 12.

14. The measuring means has a contact type or non-contact type sensor for detecting the sheet conveyed by the conveying means, and measures the length of the sheet in the conveyance direction based on the period during which the sheet conveyed by the conveying means is detected. The image forming apparatus according to any one of claims 1 to 13.

15. The measuring means has a non-contact type sensor for detecting the sheet, and is configured to be movable in the conveyance direction, and measures the length of the sheet in the conveyance direction based on the period during which the sheet is detected while the measuring means is moving in the conveyance direction. The image forming apparatus according to any one of claims 1 to 13.

16. The image forming apparatus according to claim 15, wherein the control means stops the conveyance of the sheet by the conveyance means while the measurement means measures the length of the sheet in the conveyance direction.

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