JP2018150105A - Image formation unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation unit which achieves miniaturization while obtaining an exact end portion position of paper.SOLUTION: A control unit acquires detection information which shows with or without detection of each image that is printed on adjustment paper from an offset sensor (S100). Subsequently, the thinnest image of line width (line) among images detected by the offset sensor is specified, and the specified image is stored in a storage unit (S110). Subsequently, after passing of a prescribed number of sheets of adjustment paper finishes (S120), one number among a plurality of image numbers that are acquired for each adjustment paper is decided (S130). Subsequently, a distance amendment value corresponding to the decided image number is acquired as referring an amendment value table (S140). The control unit fulfills an offset amendment of paper on the basis of an end portion position of the paper detected by the offset sensor and a distance amendment value that is acquired from the amendment value table at the time of resist swing amendment.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet.

  2. Description of the Related Art Conventionally, image forming apparatuses such as printers and copiers that employ an electrophotographic method have been widely used. In general image forming apparatuses, the direction of the paper is the direction of conveyance due to various types and properties of the paper used, the characteristics of parts such as the conveyance rollers, and the usage environment of temperature and humidity during conveyance. In some cases, the sheet is transported in a direction that is perpendicular to the direction (hereinafter referred to as the width direction). If the printing process is executed in this state, there is a problem that the printing position accuracy is lowered.

  Therefore, conventionally, the positional deviation of the paper in the width direction is detected by the deviation sensor, and the positional relationship of the paper with respect to the image is adjusted by moving the paper in the width direction by the registration roller based on the detected deviation. In other words, so-called registration fluctuation correction (deviation correction) is performed.

  However, in the case where the resist swing correction is performed, there may be a variation in the distance between the offset detection sensor and the transported paper surface. As the cause of this, there are variations in the installation positions of the transport rollers, guide members, and the like, and crossing variations of these components. As described above, when a deviation occurs in the edge position of the sheet due to the variation in the distance between the deviation sensor and the sheet, there is a problem that the image forming position also varies.

  FIG. 9A is a diagram for explaining the edge position of the paper P detected by the deviation sensor 350 when the distance between the deviation sensor 350 and the surface of the paper P is short, and FIG. 9B is a deviation sensor. FIG. 6 is a diagram for explaining an end position of a sheet P detected by a deviation sensor 350 when a distance between the surface of the sheet P and a sheet P is long. 9A and 9B, the vertical axis represents the light receiving level of the deviation sensor 350, and the horizontal axis represents the pixel position of the paper edge of the deviation sensor 350.

  The light emitted from the deviation sensor 350 is reflected by the edge of the paper P, and the reflected light is received by the deviation sensor 350. 9A and 9B, the end position O2 of the paper P detected by the deviation sensor 350 is shifted outward from the end position O3 of the paper P detected by the deviation sensor 350. The positional deviation is larger than the actual edge position O1 of the paper P. This is because the amount of light diffusion increases as the distance between the deviation sensor 350 and the surface of the paper P increases.

  In order to solve such a problem, for example, Patent Document 1 describes a technique for suppressing variation in the distance between the sheet surface and the sensor. Specifically, for the purpose of suppressing variations in the distance between the sensor and the recording paper surface due to floating of the recording paper surface, etc., the same pattern is read by a plurality of sensors with different reading angles, and the recording paper sheet on which the pattern is recorded By calculating the floating state as the amount of paper floating at both ends of the pattern, the distance between the sensor and the recording paper surface due to the floating of the recording paper surface is avoided.

JP 2013-52964 A

  However, the image forming apparatus disclosed in Patent Document 1 has the following problems. That is, in Patent Document 1, in addition to the deviation sensor, a plurality of sensors for measuring the distance between the deviation sensor and the sheet are separately required. Therefore, there is a problem that a space for installing these sensors is required, and the layout in the apparatus becomes complicated.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of obtaining an accurate edge position of a sheet while saving space.

  An image forming apparatus according to the present invention detects a position of a conveyance unit that conveys a sheet and an end position in a second direction orthogonal to a first direction that is a conveyance direction of the sheet conveyed by the conveyance unit. And a control unit that performs control to correct the deviation of the sheet by moving the sheet in the second direction based on the detection result of the end position of the sheet in the second direction detected by the detection unit. The control unit estimates the distance between the paper and the detection unit based on the image printed on the adjustment paper by the detection unit or the detection result of the adjustment paper itself.

  According to the present invention, since the detection unit is used when measuring the distance between the detection unit and the paper surface, the distance between the detection unit and the paper surface can be measured without requiring a new sensor. it can. Accordingly, it is not necessary to provide a separate installation space for the distance measurement sensor, so that the space of the apparatus can be saved. In addition, an accurate edge position of the sheet can be obtained based on the estimated distance between the detection unit and the sheet surface.

1 is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration example of an image forming apparatus. A is a diagram showing a configuration example of an image printed on the adjustment paper, and B is a diagram showing an example of detection of an image by a deviation sensor. A is a diagram for explaining the light reception level of the image of the offset sensor when the image printed on the adjustment paper is within the set distance, and B is when the image printed on the adjustment paper exceeds the set distance. It is a figure for demonstrating the light reception level of the image of a deviation sensor. It is a figure which shows the structural example of a correction value table. 10 is a flowchart illustrating an operation example of the image forming apparatus when a correction value based on a distance between a deviation sensor and a sheet is calculated. It is a figure which shows the structural example of the other image printed on adjustment paper. It is a figure which shows the structural example of the other image printed on adjustment paper. A is a diagram for explaining the edge position of the sheet detected by the deviation sensor when the distance between the deviation sensor and the sheet is short, and B is the distance between the deviation sensor and the sheet surface. FIG. 6 is a diagram for explaining an edge position of a sheet detected by a deviation sensor when is separated.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, the dimension ratio of drawing is expanded on account of description and may differ from an actual ratio.

[Configuration Example of Image Forming Apparatus 100]
FIG. 1 shows an example of the configuration of an image forming apparatus 100 according to the present invention. The image forming apparatus 100 shown in FIG. 1 forms a color image. However, the present invention is not limited to an image forming apparatus that forms a color image, but can be applied to an image forming apparatus that forms a monochrome image. it can.

  As shown in FIG. 1, the image forming apparatus 100 is called a tandem type image forming apparatus, and includes an automatic document feeder 80 and an apparatus main body 102. The automatic document conveyance unit 80 is attached to the upper part of the apparatus main body 102 and sends out the paper set on the conveyance table to the image reading unit 90 of the apparatus main body 102 by a conveyance roller or the like.

  The apparatus main body 102 includes an operation display unit 70, an image reading unit 90, an image forming unit 10, an intermediate transfer belt 8, a paper feeding unit 20, a registration unit 200, a fixing unit 44, and an automatic paper reversing conveyance unit. 60 (Auto Duplex Unit: hereinafter referred to as ADU).

  The operation display unit 70 includes a touch panel in which a display unit and an input unit are combined, and a plurality of operation keys including a start key and a determination key provided in a peripheral part of the touch panel. The operation display unit 70 displays a menu screen or the like on the screen, or receives information such as an image forming condition input by a touch operation on the menu screen or an operation of an operation key.

  The image reading unit 90 scans and exposes the document placed on the document table or the document transported by the automatic document transport unit 80 by the optical system of the scanning exposure device, and the image of the scanned document is CCD (Charge Coupled Device). ) Photoelectric conversion is performed by an image sensor to generate an image information signal. The image information signal is output to the image forming unit 10 after being subjected to analog processing, analog / digital (hereinafter referred to as A / D) conversion processing, pseudo correction, image compression processing, and the like by an image processing unit (not shown).

  The image forming unit 10 forms an image by electrophotography, and includes an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, The image forming unit 10C forms a cyan (C) color image, and the image forming unit 10K forms a black (K) color image. In this example, common function names, for example, Y, M, C, and K indicating colors to be formed are added to the back of the reference numeral 10.

  The image forming unit 10Y includes a photosensitive drum 1Y, a charger 2Y, an exposure unit (optical writing unit) 3Y, a developing unit 4Y, and a cleaning unit 6Y arranged around the photosensitive drum 1Y. The image forming unit 10M includes a photosensitive drum 1M, a charger 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 6M disposed around the photosensitive drum 1M. The image forming unit 10C includes a photosensitive drum 1C, and a charger 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 6C disposed around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K, a charger 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 6K disposed around the photosensitive drum 1K.

  Respective photosensitive drums (image carriers) 1Y, 1M, 1C, and 1K in the image forming units 10Y, 10M, 10C, and 10K, chargers 2Y, 2M, 2C, and 2K, exposure units 3Y, 3M, 3C, and 3K, development The devices 4Y, 4M, 4C, and 4K, the cleaning units 6Y, 6M, 6C, and 6K, and the primary transfer rollers 7Y, 7M, 7C, and 7K have a common configuration. In the following description, Y, M, C, and K are not used unless particularly distinguished.

  The charger 2 charges the surface of the photosensitive drum 1 almost uniformly. The exposure unit 3 is composed of, for example, an LPH (LED Print Head) having an LED array and an imaging lens, or a polygon mirror type laser exposure scanning device, and the photosensitive drum 1 is irradiated with laser light based on an image information signal. Scan to form an electrostatic latent image. The developing device 4 develops the electrostatic latent image formed on the photosensitive drum 1 with toner. As a result, a toner image which is a visible image is formed on the photosensitive drum 1.

  The intermediate transfer belt 8 is stretched by a plurality of rollers and is rotatably supported. Along with the rotation of the intermediate transfer belt 8, the primary transfer roller 7 and the photosensitive drum 1 rotate, and a predetermined voltage is applied between the primary transfer roller 7 and the photosensitive drum 1, whereby the photosensitive member. The toner image formed on the drum 1 is transferred onto the intermediate transfer belt 8 (primary transfer).

  The paper feed unit 20 has a plurality of paper feed trays 20A and 20B in which paper P such as A3 and A4 is accommodated. The paper P transported from the paper feed trays 20 </ b> A and 20 </ b> B by the transport rollers 22, 24, 26, and 28 is transported to the registration unit 200. Note that the number of paper feed trays is not limited to two. Further, a single or a plurality of large-capacity paper feeders that can accommodate a large-capacity paper P may be connected as necessary.

  The registration unit 200 corrects the bending of the paper P or corrects the deviation. The paper P in which the bending of the paper P is corrected is conveyed to the secondary transfer roller 34 in accordance with the conveyance timing of the toner image transferred to the intermediate transfer belt 8. In the secondary transfer roller 34, the Y, M, C, and K color toner images transferred onto the intermediate transfer belt 8 are collectively transferred onto the surface of the paper P (secondary transfer). The second-transferred sheet P is conveyed to the fixing unit 44 on the downstream side in the conveyance direction D1.

  The fixing unit 44 includes a pressure roller and a heating roller. The fixing unit 44 fixes the toner image on the surface of the paper P to the paper P by performing pressure and heat treatment on the paper P on which the toner image has been transferred by the secondary transfer roller 34.

  A transport path switching unit 48 for switching the transport path of the paper P to the paper discharge path side or the ADU 60 side is provided downstream of the fixing unit 44 in the paper travel direction D. The transport path switching unit 48 performs transport path switching control based on the selected print mode (single-sided print mode, double-sided print mode, or the like).

  The paper P on which single-sided printing has been completed in the single-sided printing mode or the paper P on which double-sided printing has been completed in the double-sided printing mode is discharged onto the paper discharge tray by the paper discharge roller 46.

  Further, when an image is formed on the back side of the paper P in the duplex printing mode, the paper P on which the image is formed on the front side is conveyed to the ADU 60 via the conveyance roller 62 and the like. In the switchback path of the ADU 60, the reverse rotation control of the ADU roller 64 causes the rear end of the paper P to be transported to the U-turn path section, and is reversed by the transport rollers 66 and 68 provided in the U-turn path section. In this state, the paper is fed again to the secondary transfer roller 34.

[Configuration Example of Resist Part 200]
FIG. 2 illustrates an example of a functional configuration of the registration unit 200 and the like that configure the image forming apparatus 100. As shown in FIG. 2, the registration unit 200 includes a registration roller 210, a swinging unit 220, a pressure-bonding / separating unit 230, a transport unit 240, a deviation sensor 250, and a storage unit 260. Each of the oscillating part 220, the crimping / separating part 230, the conveying part 240, and the offset sensor 250 is connected to the control part 50.

  The control unit 50 controls the operation of the entire apparatus, and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU executes the software (program) read from the ROM to control each unit of the image forming apparatus 100, and the distance between the deviation sensor 250 and the sheet P and the width P of the sheet P based on the distance. A process of calculating a deviation amount (correction value) is realized.

  The registration roller 210 is composed of a pair of rollers made of a resin material arranged to face each other. The registration roller 210 corrects the bending of the paper P by creating a loop by abutting the leading edge of the paper P, or corrects the deviation of the paper P by swinging in the width direction D2 while holding the paper P. To do.

  The oscillating unit 220 includes a drive motor configured by a stepping motor, a rack, a pinion gear, and the like. The drive motor of the swing unit 220 is driven based on a drive signal (correction value) supplied from the control unit 50, and moves the registration roller 210 along the width direction D2 by operating the rack and pinion gear.

  The crimping / separating portion 230 has a drive motor constituted by a stepping motor or the like, a cam, a cam follower, or the like. The drive motor of the crimping separation unit 230 rotates the cam based on the drive signal supplied from the control unit 50 and presses the cam follower to move the registration roller 210 away from the crimping state or rotate the cam. Thus, the registration roller 210 is changed from the separated state to the pressure-bonded state by being separated from the cam follower.

  The transport unit 240 is composed of a drive motor such as a stepping motor or a DC brushless motor, for example, and is driven based on a drive signal supplied from the control unit 50 to rotate the registration roller 210 forward or backward.

  The offset sensor 250 is provided downstream of the registration roller 210 in the transport direction D1, and, for example, a line sensor or a photoelectric conversion element in which a plurality of photoelectric conversion elements are linearly arranged along the width direction D2 in a matrix form. It is composed of arranged image sensors. The deviation sensor 250 reads the end position Os in the width direction D2 of the conveyed paper P, and supplies information related to the read end position Os to the control unit 50. In the present embodiment, the deviation sensor 250 detects the distance between the deviation sensor 250 and the paper P and supplies the detection information to the control unit 50.

  In addition, the image forming apparatus 100 includes a storage unit 260. The storage unit 260 is connected to the control unit 50 and includes, for example, a semiconductor memory, an HDD (Hard Disc Drive), or the like. The storage unit 260 stores a correction value table TB described later.

[Configuration Example of Adjustment Paper Pt]
FIG. 3A shows an example of the configuration of the images G1 to G9 printed on the adjustment paper Pt, and FIG. 3B shows the detection results of the images G1 to G9 by the deviation sensor 250.

  As shown in FIG. 3A, a plurality of images G1 to G9 having a line shape are printed on the surface of the adjustment paper Pt. The longitudinal directions of the images G1 to G9 extend in parallel to the transport direction D1. The lengths of the images G1 to G9 in the short direction (hereinafter sometimes referred to as line width) are set in this order so as to become shorter from the left side to the right side in the width direction D2 of the adjustment paper Pt. Specifically, the line width becomes narrower in the order of image G1 <image G2 <image G3 <image G4 <image G5 <image G6 <image G7 <image G8 <image G9.

  The line widths of the images G1 to G9 are associated with distances at which the deviation sensor 250 can detect the paper P. In other words, when the paper P is separated by a corresponding distance or more with respect to the deviation sensor 250, the images G1 to G9 cannot be detected (recognized) by the deviation sensor 250. For example, as shown in FIG. 3B, when the images G7 to G9 are separated from the offset sensor 250 beyond the set distance, the images G7 to G9 are not detected by the offset sensor 250, and the output waveform does not fall. Turns on. On the other hand, since the images G1 to G6 are detected by the deviation sensor 250, the output waveform falls and is turned off.

  As the adjustment paper Pt, for example, images obtained by printing images G1 to G9 on paper may be prepared in advance. Further, the adjustment sheet Pt may be created before or after execution of the job. Further, the number of images to be printed on the adjustment paper Pt is not limited to the number and the line width shown in FIG. 3A.

[Example of relationship between distance between adjustment sheet Pt and offset sensor 250 and light receiving level of offset sensor 250]
FIG. 4A is a diagram for explaining the light reception level of the image G1 at the deviation sensor 250 when the image G1 printed on the adjustment paper Pt is within the corresponding distance S1, for example. As shown in FIG. 4A, when the adjustment paper Pt is at the distance S1, the light reflected around the image G1 does not enter the portion corresponding to the image G1 of the deviation sensor 250. For this reason, the light reception level of the analog waveform of light detected by the deviation sensor 250 falls in the image G1 portion, exceeds the threshold value, and the digital waveform is turned off. In this case, since the image G1 printed on the adjustment paper Pt is at a position that can be detected by the deviation sensor 250, it can be determined that the adjustment paper Pt is within the distance S1.

  FIG. 4B is a diagram for explaining the light reception level of the image G1 at the deviation sensor 250 when, for example, the image G1 printed on the adjustment paper Pt exceeds the corresponding distance S1. In FIG. 4B, distance S2> distance S1. As shown in FIG. 4B, when the adjustment paper Pt is at a distance S2 that exceeds the distance S1, light reflected and diffused around the image G1 easily enters the portion corresponding to the image G1 of the deviation sensor 250. Become. Therefore, the light reception level of the analog waveform of the light detected by the deviation sensor 250 does not exceed the threshold value, and the digital waveform remains on and does not change. In this case, since the image G1 printed on the adjustment paper Pt is not in a position that can be detected by the deviation sensor 250, it can be determined that the adjustment paper Pt is not within the distance S1.

[Configuration Example of Correction Value Table TB]
FIG. 5 shows an example of the configuration of the correction value table TB. As shown in FIGS. 2 and 5, the correction value table TB is stored in a memory such as the storage unit 260. In the correction value table TB, the image numbers corresponding to the images G1 to G9, the distance at which each of the images G1 to G9 can be detected by the offset sensor 250, and the width direction D2 of the paper P generated according to each distance are displayed. The distance correction values for correcting the deviation are stored in association with each other. In the correction value table TB, for example, the image number “3” of the image G3, the distance “1.6” that is the distance that the image G3 can be detected by the offset sensor 250, and the distance “1.6” are stored. The distance correction value “−0.35” for correcting the shift in the width direction D2 of the paper P is stored in association with each other.

  The control unit 50 adds the edge position of the sheet P detected by the deviation sensor 250 and the distance correction value acquired from the correction value table TB during the registration swing correction, and swings the registration roller 210. The oscillation correction value to be calculated is calculated. The correction value table TB may be created before the shipping stage, or may be created and updated after shipping.

[Operation Example of Image Forming Apparatus 100]
FIG. 6 is a flowchart showing an example of the operation of the image forming apparatus 100 when calculating a correction value based on the distance between the paper P and the deviation sensor 250. This control may be executed when, for example, a predetermined number of sheets P based on the job have been passed, or may be performed when the image forming apparatus 100 is turned on or returned from the sleep mode. Alternatively, it may be executed when the user selects this control on the operation display unit 70 or the like. Hereinafter, a case where the adjustment paper Pt shown in FIG. 3A is used will be described.

  As shown in FIG. 6, in step S <b> 100, the control unit 50 acquires detection information indicating whether or not each image G printed on the adjustment paper Pt is detected from the deviation sensor 250. For example, as illustrated in FIGS. 3A and 3B, when the images G1 to G6 are detected by the deviation sensor 250 as the adjustment paper Pt is conveyed, the control unit 50 changes the images G1 to G6 from the deviation sensor 250. Get detection information based on it. When step S100 ends, the process proceeds to step S110.

  In step S <b> 110, the control unit 50 specifies the image G having the narrowest line width (line) among the images G detected by the deviation sensor 250, and stores the specified image G in the storage unit 260. For example, the control unit 50 identifies the image G6 having the narrowest line width among the images G1 to G6 detected by the deviation sensor 250. When step S110 ends, the process proceeds to step S120.

  In step S120, the control unit 50 determines whether or not the passing of the specified number of adjustment sheets Pt has been completed. If the control unit 50 determines that the passing of the specified number of adjustment sheets Pt has not been completed, the control unit 50 returns to step S100 and repeatedly executes the processes of S100 and S110 described above. On the other hand, if the control unit 50 determines that the passing of the specified number of adjustment sheets Pt has been completed, the process proceeds to step S130.

  In step S130, the control unit 50 determines one number from the numbers of the plurality of images G acquired for each adjustment sheet Pt. For example, when the numbers of a plurality of images G are the same on a plurality of adjustment sheets Pt, the numbers of the images G can be selected. Further, when the numbers of the plurality of images G are different on the plurality of adjustment sheets Pt, the number with the largest number can be selected. Thereby, the accuracy at the time of calculating the distance between the paper P and the deviation sensor 250 can be improved. When step S130 ends, the process proceeds to step S140.

  In step S140, the control unit 50 acquires a correction value corresponding to the determined number of the image G with reference to the correction value table TB. For example, when the determined number of the image G is “6”, the control unit 50 acquires “1.0” as the distance and “−0.20” as the distance correction value.

  The control unit 50 adds the edge position of the paper P detected by the deviation sensor 250 and the distance correction value acquired from the correction value table TB to calculate a swing correction value for swinging the registration roller 210. To do. At the time of registration swing correction, the control unit 50 corrects the deviation of the paper P by swinging the paper P in the width direction D2 with the registration roller 210 sandwiching the paper P based on the swing correction value. Further, the control unit 50 adjusts the writing position of the laser beam (image) to be written on the photosensitive drum 1 based on the calculated fluctuation correction value, thereby correcting the deviation of the image forming position with respect to the paper P. May be.

[Modification of Image Printed on Adjustment Paper Pt]
FIG. 7 shows an example of the configuration of another image G10 printed on the adjustment paper Pt. As shown in FIG. 7, a line-like image G10 is printed on one end of the adjustment paper Pt in the width direction D2. The longitudinal direction of the image G10 extends in parallel to the transport direction D1. The line width of the image G10 is associated with the distance between the deviation sensor 250 and the paper P that allows the deviation sensor 250 to accurately detect the image G10. Hereinafter, this distance is referred to as a reference distance.

  When the line width of the image G10 detected by the offset sensor 250 is the same as the preset line width (design value) of the image G10, the control unit 50 determines whether the offset sensor 250 and the adjustment paper Pt are between. A preset reference distance is selected as the distance. On the other hand, when the line width of the image G10 detected by the deviation sensor 250 is greater than or less than the preset line width of the image G10, the deviation sensor 250 is based on a preset reference distance. And the adjustment paper Pt is calculated.

  FIG. 8 shows an example of the configuration of another image G11 printed on the adjustment paper Pt. As shown in FIG. 8, a line-shaped image G11 extending in the direction intersecting the transport direction D1 is printed on the surface of the adjustment paper Pt. The line width of the image G10 is the same as that of the image G10 described above, and the line width of the image G10 is between the deviation sensor 250 and the paper P, which allows the deviation sensor 250 to accurately detect the image G10. Associated with distance. Note that the method for calculating the distance between the deviation sensor 250 and the adjustment paper Pt is almost the same as that for the image G10 shown in FIG.

  As described above, according to the present embodiment, when the distance between the deviation sensor 250 and the surface of the paper P is measured, the deviation sensor 250 is used, so that a new sensor is not required. The distance between the deviation sensor 250 and the surface of the paper P can be measured. As a result, it is not necessary to provide a separate installation space, so that the space of the apparatus can be saved. Furthermore, since no separate sensor is required, the cost can be reduced.

  Further, when the image G11 shown in FIG. 7 is used, the distance between the deviation sensor 250 and the adjustment paper Pt in the entire width direction D2 of the adjustment paper Pt can be calculated, and the inclination of the adjustment paper Pt is calculated. You can also Accordingly, the image formation can be performed with higher accuracy by adjusting the image writing position based on the inclination result of the adjustment paper Pt. When calculating the inclination of the paper P in addition to the distance between the deviation sensor 250 and the adjustment paper Pt, the line widths of the images G1 to G9 shown in FIG. 3A are all configured to be the same length. Can be realized.

  Although the present invention has been described using the embodiment, the technical scope of the present invention is not limited to the scope described in the embodiment. Various modifications or improvements can be added to the above-described embodiments without departing from the spirit of the present invention.

  For example, it is preferable that the control unit 50 obtains the distance between the deviation sensor 250 and the paper P each time the conveyance path of the paper P is changed, and estimates the variation in the distance between the papers P. Specifically, when the paper P is sent out from the paper feeding unit 20 of the image forming apparatus 100, and from the large-capacity paper feeding device (not shown) connected to the upstream side in the transport direction D1 of the image forming apparatus 100. The distance between the deviation sensor 250 and the paper P is acquired in each case of sending out. This is because the crossing variation and deterioration of parts such as the conveyance roller are different for each conveyance path, and the conveyance varies. Thereby, the end position of the paper P can be corrected with higher accuracy.

  In the above-described embodiment, the distance between the deviation sensor 250 and the adjustment paper Pt is calculated based on the image G printed on the adjustment paper Pt. However, the present invention is not limited to this. For example, when the length in the width direction D2 of a postcard or B5 size paper is shorter than the length in the width direction D2 of the offset sensor 250, the postcard or B5 size paper itself is used as the adjustment paper Pt. Can do. In this case, the offset sensor 250 detects a peripheral portion such as a postcard as black, and detects the postcard itself as white. The control unit 50 determines the distance between the offset sensor 250 and the postcard based on the detection result of the postcard or the like by the offset sensor 250 and the length (design value) of the postcard or the like in the width direction D2. Is calculated. The other parts are the same as those in FIGS. 4 and 7 and the like, and thus the details are omitted.

1Y, 1M, 1C, 1K Photosensitive drum (image carrier)
50 Control unit 100 Image forming apparatus 210 Registration roller (conveyance unit)
240 Conveyor 250 Misalignment sensor (detector)
G, G1, G2, G3, G4, G5, G6, G7, G8, G9, G10, G11 Image P Paper Pt Adjustment paper D1 Conveying direction (first direction)
D2 width direction (second direction)

Claims (9)

A transport unit for transporting paper;
A detection unit that detects an end position in a second direction orthogonal to a first direction that is a conveyance direction of a sheet conveyed by the conveyance unit;
A control unit that performs control to correct the deviation of the sheet by moving the sheet in the second direction based on the detection result of the end position in the second direction of the sheet detected by the detection unit. ,
The control unit estimates the distance between the sheet and the detection unit based on an image printed on the adjustment sheet by the detection unit or a detection result of the adjustment sheet itself. The control unit acquires a correction value for correcting a shift in the edge position of the sheet from the estimated distance.
The image forming apparatus according to claim 1. The image extends in a direction parallel to or intersecting the first direction;
The image forming apparatus according to claim 1. A plurality of images are formed on the adjustment paper,
The plurality of images have different lengths in the second direction.
The image forming apparatus according to claim 1. The control unit selects an image having the shortest length in the second direction among the plurality of images that can be detected by the detection unit, and based on the selected image, between the sheet and the detection unit. Get the distance,
The image forming apparatus according to claim 1. The control unit determines whether the adjustment sheet and the detection unit are based on a preset length in the second direction of the image and a length in the second direction of the image detected by the detection unit. To get the distance between the
The image forming apparatus according to claim 1. The adjustment sheet is configured such that the length in the second direction is shorter than the length in the second direction of the detection unit,
The control unit is configured to set the adjustment sheet and the detection unit based on a preset length in the second direction of the adjustment sheet and a length in the second direction of the adjustment sheet detected by the detection unit. To get the distance between the
The image forming apparatus according to claim 1. The control unit corrects a writing position for moving the paper in the second direction or writing an image on the image carrier based on the correction value.
The image forming apparatus according to claim 2. The control unit obtains a distance between the detection unit and the sheet for each sheet conveyance path.
The image forming apparatus according to claim 1.

Images