JP2014112141A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of resetting a reference position for correcting deviation of a sheet and a writing range of an image so as to improve image quality.SOLUTION: An image forming apparatus includes: an image forming unit that has a predetermined writing range set therein, and forms an image on a sheet on the basis of the writing range; a resist roller that is arranged upstream of the image forming unit while being adjustable in an axial direction, and conveys a sheet to the image forming unit; a deviation detection unit that detects a position in a width direction of a sheet passing through the resist roller; a deviation correction unit that moves the resist roller in the width direction by a deviation amount from a reference position on the basis of a detection result by the deviation detection unit to correct the position in the width direction of the sheet; and a control unit that sets the reference position, and sets the writing range on the basis of the set reference position.

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method.

  In general, in an image forming apparatus (printer, copying machine, facsimile, etc.) using an electrophotographic process technology, a charged photoconductor is irradiated (exposed) with a laser beam based on image data. An electrostatic latent image is formed on the surface. Then, toner is supplied from the developing device to the photosensitive member (image carrier) on which the electrostatic latent image is formed, so that the electrostatic latent image is visualized and a toner image is formed. The toner image is transferred directly or indirectly to the sheet via an intermediate transfer belt, and then heated and pressed by a fixing unit, whereby an image is formed on the sheet.

The image forming apparatus described above includes a paper transport unit that transports paper fed from a paper feed tray, a manual feed tray, or an external paper feed device to the image forming unit. A plurality of transport rollers such as an intermediate transport roller, a loop roller, and a registration roller are disposed in the paper transport unit.
In the paper transport unit, the paper is continuously transported by the loop roller even after the leading edge of the paper reaches the registration roller, so that the paper bends between the registration roller and the loop roller, and the tilt of the paper is eliminated. The

  Further, the paper transport unit is provided with a deviation correction unit for correcting the position of the paper in the width direction (direction orthogonal to the transport direction, main scanning direction). For example, the position of the sheet in the width direction is corrected (registration swing) by conveying the sheet while the registration roller swings in the width direction (axial direction of the registration roller). This registration rocking operation is performed based on the detection result (deviation amount, deviation from the reference position) by a deviation detection sensor such as a line sensor arranged on the downstream side of the registration roller (for example, Patent Document 1). .

FIG. 1 is a view showing a registration roller portion having a resist swinging function. As shown in FIG. 1, the deviation amount ΔX of the sheet S detected by the deviation detection sensor 565 is defined by a deviation amount from a predetermined reference position X0 (swing target position). Here, the reference position X0 is given by, for example, a distance d0 from the end of the deviation detection sensor 565, and is set at the time of shipment. At the time of shipment, an image writing range is set based on the reference position X0.
At the time of deviation correction, the registration roller R swings so that the end of the sheet S is at the reference position X0. For example, in the case shown in FIG. 1, the registration roller R moves leftward, whereby the deviation of the sheet S by the deviation amount ΔX is corrected. As a result, an image is formed at a predetermined position on the paper S.

JP 2007-22680 A

In the conventional image forming apparatus, the reference for correcting deviation (distance from the end of the deviation detection sensor) and the image writing range are set at the time of shipment of the image forming apparatus and are changed as they are. Retained without. Therefore, for example, when the axial direction of the registration roller is adjusted to be parallel to the axis of the transfer unit and the fixing unit (so-called alignment adjustment), or the unit (registration unit) in which the registration roller is arranged is replaced. Then, the reference position for performing the deviation correction is shifted (see FIG. 2).
In this case, the sheet S is passed with the offset corrected so that the end is located at the reference position X1 after adjustment or after unit replacement, while the image is written based on the initial reference position X0. Since the image is formed in the range, the image is displaced (see FIG. 2B).

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and an image forming method capable of resetting a reference position and an image writing range for correcting paper misalignment and improving image quality. .

An image forming apparatus according to the present invention has a predetermined writing range, and an image forming unit that forms an image on a sheet based on the writing range;
A registration roller disposed upstream of the image forming unit so as to be adjustable in axial direction, and for conveying paper to the image forming unit;
A deviation detection unit that detects a position in the width direction of the sheet passing through the registration roller;
Based on the detection result by the deviation detection unit, the deviation correction unit that moves the registration roller in the width direction by the amount of deviation from the reference position and corrects the position in the width direction of the paper;
And a control unit that sets the reference position and sets the writing range based on the set reference position.

The image forming method according to the present invention includes a first step of setting a reference position for correcting a shift in the width direction of a sheet and a writing range based on the reference position;
A second step of detecting the position in the width direction of the conveyed paper; a third step of moving the paper in the width direction by an amount of deviation from the reference position based on the detection result in the second step; ,
And a fourth step of forming an image on a sheet based on the writing range.

  According to the present invention, it is possible to reset the reference position and the image writing range for correcting the misalignment of the paper as necessary, so that the deviation between the paper transport position and the image writing position can be reduced. It can be easily solved and the image quality can be improved.

It is a figure which shows the registration roller part provided with the registration rocking | fluctuation function. It is a figure which shows the reference position before and after alignment adjustment. 1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus according to the embodiment. It is the figure which looked at the registration roller part from the upper part. FIG. 6 is a view of a registration roller portion as viewed from the upstream side in the paper conveyance direction. It is a flowchart which shows an example of a reset process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 3 is a diagram showing an overall configuration of the image forming apparatus 1 according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the embodiment.
An image forming apparatus 1 shown in FIGS. 3 and 4 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. In the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction (vertical direction) of the intermediate transfer belt 421, and each color toner image is formed on the intermediate transfer belt 421 in one procedure. The vertical tandem method is used to transfer the images sequentially.
That is, the image forming apparatus 1 transfers the toner images of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 to the intermediate transfer belt 421 (primary transfer). Then, after superposing four color toner images on the intermediate transfer belt 421, the toner images are transferred to the paper S (secondary transfer) to form an image.

  As shown in FIGS. 3 and 4, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, and a control unit 100. .

  The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads a program corresponding to the processing content from the ROM 102 and develops it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 100 also exchanges various data with an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. Send and receive. For example, the control unit 100 receives image data transmitted from an external device, and forms an image on the paper S based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card, for example.

The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.
The automatic document feeder 11 transports the document D placed on the document tray by a transport mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on a document tray all at once.
The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

  The operation display unit 20 is configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, an image status display, an operation status of each function, and the like in accordance with a display control signal input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 100.

  The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 100. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, a compression process, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data subjected to these processes.

  The image forming unit 40 includes, based on input image data, an image forming unit 41, an intermediate transfer unit 42, and a secondary transfer unit for forming an image using colored toners of Y component, M component, C component, and K component. 43 and the like. The writing range of the image formed by the image forming unit 40 is set in advance.

  The image forming unit 41 includes four image forming units 41Y, 41M, 41C, and 41K for Y component, M component, C component, and K component. Since the image forming units 41Y, 41M, 41C, and 41K have the same configuration, for convenience of illustration and description, common constituent elements are denoted by the same reference numerals, and when distinguished from each other, the reference numerals Y, M, and C are used. Or K. In FIG. 1, only the components of the Y-component image forming unit 41Y are denoted by reference numerals, and the constituent elements of the other image forming units 41M, 41C, and 41K are omitted.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

The photosensitive drum 413 has, for example, an undercoat layer (UCL), a charge generation layer (CGL), a charge transport layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube). It is a negatively charged organic photoreceptor (OPC: Organic Photo-conductor) in which CTL (Charge Transport Layer) is sequentially laminated.
The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and generates a pair of positive charges and negative charges by exposure by the exposure device 411. The charge transport layer consists of a hole transport material (electron donating nitrogen-containing compound) dispersed in a resin binder (for example, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.
The control unit 100 controls a driving current supplied to a driving motor (not shown) that rotates the photosensitive drum 413, so that the photosensitive drum 413 rotates at a constant peripheral speed.

The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity.
The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. A positive charge is generated in the charge generation layer of the photosensitive drum 413 and is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

The developing device 412 contains a developer of each color component (for example, a two-component developer composed of a toner having a small particle diameter and a magnetic material), and causes the toner of each color component to adhere to the surface of the photosensitive drum 413. Thus, the electrostatic latent image is visualized to form a toner image.
The drum cleaning device 415 includes a drum cleaning blade that is slidably contacted with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after primary transfer.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423 including a backup roller 423A, a belt cleaning device 426, and the like.
The intermediate transfer belt 421 is an endless belt, and is stretched around a plurality of support rollers 423 in a loop shape. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller. The intermediate transfer belt 421 travels at a constant speed in the direction of arrow A by the rotation of the support roller 423 serving as a drive roller. When the intermediate transfer belt 421 is pressed against the photosensitive drum 413 by the primary transfer roller 422, the respective color toner images are sequentially superimposed and primarily transferred onto the intermediate transfer belt 421.

The secondary transfer unit 43 includes a secondary transfer roller 431, for example. The secondary transfer unit 43 may have a configuration in which a secondary transfer belt is looped around a plurality of support rollers including a secondary transfer roller.
The secondary transfer roller 431 is pressed against the backup roller 423A via the intermediate transfer belt 421, thereby forming a transfer nip (transfer portion). When the sheet S passes through the transfer nip, the toner image carried on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, the toner image is electrostatically transferred onto the paper S by applying a voltage (transfer bias) having a polarity opposite to that of the toner to the secondary transfer roller 431. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 426 includes a belt cleaning blade that is slidably contacted with the surface of the intermediate transfer belt 421 and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

The fixing unit 60 is disposed on the fixing surface side member 61 (for example, a fixing roller) disposed on the fixing surface (surface on which the toner image is formed) side of the paper, and on the back surface (surface opposite to the fixing surface) side of the paper. A back side support member 62 (for example, a pressure belt), a heating source 63, and the like. When the back surface side support member 62 is pressed against the fixing surface side member 61, a fixing nip for nipping and transporting the paper S is formed.
The fixing unit 60 fixes the toner image on the sheet S by heating and pressing the conveyed sheet S at the fixing nip. The fixing unit 60 is disposed in the fixing device F as a unit. An air separation unit that separates the sheet S from the fixing surface side member 61 or the back surface side support member 62 by blowing air may be arranged in the fixing device F.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a first transport unit 53, a second transport unit 57, and the like.
In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, or the like is stored for each preset type. .

The first transport unit 53 includes a plurality of transport roller units including an intermediate transport roller unit 54, a loop roller unit 55, and a registration roller unit 56.
The loop roller unit 55 includes a pair of loop rollers. The loop roller unit 55 conveys the paper S delivered from the upstream intermediate conveyance roller unit 54 and delivers it to the downstream registration roller unit 56. The sheet is bent in the loop forming portion between the two.
The registration roller unit 56 includes a pair of registration rollers (a driving roller 561 and a driven roller 562 described later), and is disposed on the upstream side of the image forming unit 40 (transfer unit) and on the downstream side of the loop roller unit 55. The registration roller unit 56 corrects the inclination of the paper S and the position in the width direction (main scanning direction).

  The second transport unit 57 includes a switchback path 58 and a back surface transport path 59 in which a plurality of transport roller units are arranged. The second transport unit 57 once transports the paper S to the switchback path 58, then switches back and transports the paper S to the back surface transport path 59, thereby reversing the paper S, and the first transport unit 53 (loop roller) To the upstream of the section 55.

  The paper S fed from the paper feed tray units 51 a to 51 c or an external paper feeder (not shown) is transported to the image forming unit 40 by the first transport unit 53. At this time, even after the leading edge of the sheet S reaches the registration roller unit 56, the rotation by the registration roller unit 56 (drive roller 561) is stopped and the conveyance by the loop roller unit 55 is continued. As a result, the leading edge of the sheet S comes into contact with the registration nip, and the bending of the sheet S is formed in the loop forming portion. The inclination of the paper S is corrected by the stress generated in the paper S.

After the inclination of the sheet S is corrected, sheet conveyance (rotation drive of the driving roller 561) by the registration roller unit 56 is started, and the sheet S is conveyed toward the transfer nip of the image forming unit 40. At this time, when the deviation detection sensor 565 detects the deviation of the sheet S, the position of the sheet S in the width direction is corrected in the process of being conveyed by the registration roller unit 56 (registration swing).
Then, when the sheet S passes through the transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred onto one surface (front surface) of the sheet S at a time, and a fixing process is performed in the fixing unit 60. The paper S on which the image is formed is discharged out of the apparatus by a paper discharge unit 52 having a paper discharge roller 52a.

  FIG. 5 is a view of the registration roller portion 56 as viewed from above (the base end side in the Z direction). FIG. 6 is a view of the registration roller unit 56 as viewed from the upstream side in the paper conveyance direction (Y direction base end side). 5 and 6, the X-axis is the horizontal direction (the axial direction of the registration roller), the Z-axis is the vertical direction, and the Y-axis is the paper transport direction perpendicular to the X-axis and the Z-axis.

  As illustrated in FIGS. 5 and 6, the registration roller unit 56 includes a pair of registration rollers R including a driving roller 561 and a driven roller 562 disposed to face the driving roller 561. The driving roller 561 is composed of, for example, a rubber roller, and the driven roller 562 is composed of, for example, a metal roller. The driven roller 562 is held in a state where it is constantly pressed against the driving roller 561. When the driven roller 562 is pressed against the driving roller 561, a nip portion (registration nip) for nipping and transporting the paper S is formed.

The driving roller 561 and the driven roller 562 are inserted through bearings formed on the frame 568 and are rotatably fixed. The axial direction can be adjusted while maintaining the positional relationship between the driving roller 561 and the driven roller 562 by swinging the frame 568 in the vertical direction or the horizontal direction while the driving roller 561 and the driven roller 562 are fixed. . As described above, the registration roller R including the driving roller 561 and the driven roller 562 is arranged so that the axial direction can be adjusted.
Further, the roller shaft 561 b of the driving roller 561 and the roller shaft 562 b of the driven roller 562 are connected by a connecting member 567. Thereby, when correcting the position of the paper S in the width direction, the driving roller 561 and the driven roller 562 move together in the width direction.

  The drive roller 561 is connected to a drive motor 566 via a power transmission unit including gears 561a and 566a. The gear 561a has a predetermined length so that the driving force is transmitted even if the driving roller 561 moves in the axial direction when the resist is rocked. The power of the driving motor 566 is transmitted to the driving roller 561 via the gears 566a and 561a, so that the driving roller 561 and the driven roller 562 rotate. The sheet conveying operation (driving of the driving motor 566) in the registration roller unit 56 is controlled by the control unit 100.

The driving roller 561 is connected to the swinging motor 563 via a power transmission unit 564 including a rack 564b and a pinion 564a. That is, the power transmission unit 564 and the swinging motor 563 constitute a deviation correction unit that moves the registration roller R in the width direction and corrects the position in the width direction of the sheet.
The rack 564b is a cylindrical member having a bearing on the inner surface, and is inserted through the roller shaft 561b. The rack 564b is fixed in the vicinity of the gear 561a by sandwiching both ends of the rack 564b with two washers (for example, E-rings) fixed to the roller shaft 561b. That is, the rack 564b is fixed so as not to move in the axial direction while allowing the drive roller 561 to rotate.

On the downstream side of the registration roller unit 56, a deviation detection sensor 565 that detects a position (deviation) in the width direction of the paper S passing through the registration roller R is disposed. Specifically, the deviation detection sensor 565 is disposed in a region on the downstream side of the registration roller R in the frame 568 in parallel with the registration roller R.
The deviation detection sensor 565 is constituted by, for example, a line sensor in which the image receiving elements are arranged in a horizontal row (or a plurality of rows), and detects the position of the end portion in the width direction of the paper S. By configuring the deviation detection sensor 565 with a line sensor, it is possible to detect the position of the edge of the sheet S in the width direction and the amount of deviation (deviation from the reference position) with high accuracy (for example, several tens of μm). .

  Further, as shown in FIG. 1, the deviation amount ΔX detected by the deviation detection sensor 565 is defined by a deviation amount from a predetermined reference position X0 (swing target position). The reference position X0 is given by, for example, a distance d0 from the end of the deviation detection sensor 565. An image writing range is set based on the reference position X0. The reference position X0 and the image writing range are set when the image forming apparatus is shipped, for example.

  The control unit 100 controls the swinging operation of the registration roller R. Specifically, the control unit 100 controls the swing motor 563 based on the detection result by the deviation detection sensor 565. The rotational motion of the swinging motor 563 is converted into a linear motion by the pinion 564a and the rack 564b and transmitted to the drive roller 561. As a result, the registration roller R including the driving roller 561 and the driven roller 562 moves by a predetermined amount in the axial direction.

  For example, when the sheet S is shifted to the right in the width direction as shown in FIG. 1, the control unit 100 determines the amount of deviation ΔX (reference) based on the detection result (position of the left end in the width direction) by the deviation detection sensor 565. (Deviation from position X0) is calculated. Then, the control unit 100 moves the registration roller R by a movement amount corresponding to the deviation amount ΔX in a direction in which the left end portion in the width direction of the paper S becomes the reference position X0 (left direction in FIG. 5). As the driving roller 561 and the driven roller 562 move in the width direction while rotating, that is, conveying the paper S, the position in the width direction of the paper S is corrected. As a result, an image is formed at a predetermined position on the paper S.

  In addition, when the detection result by the deviation detection sensor 565 exceeds the swingable range (for example, ± 5 mm) of the registration roller unit 56, the position in the width direction of the sheet S cannot be completely corrected. A jam occurs and the image forming process is stopped.

  In the image forming apparatus 1, a reference position X0 and an image writing range for correcting the deviation of the sheet at the time of shipment are set in advance. In this embodiment, after the axial direction of the registration roller R is further adjusted, or after the registration unit in which the registration roller unit 56 is disposed is replaced, the reference position and the image writing range are set as necessary. It is set again.

  FIG. 7 is a flowchart illustrating an example of the resetting process. The resetting process shown in FIG. 7 is realized, for example, by executing a predetermined program stored in the ROM 102 by the CPU 101 when the image forming process is started.

  In step S101 in FIG. 7, the control unit 100 determines whether or not it is necessary to reset the reference position and the image writing range for correcting the deviation of the sheet. If the control unit 100 determines that the reference position and the image writing range need to be reset, the control unit 100 proceeds to the process of step S102.

For example, the control unit 100 determines that resetting is necessary when an operation for instructing resetting is performed by the user on the operation unit 22. Whether or not an operation for instructing resetting has been performed by the user can be determined based on an input signal from the operation unit 22.
After the user adjusts the axial direction of the registration roller R or replaces the registration unit, the user can easily execute the resetting process simply by performing an operation for instructing resetting in the operation unit 22. Further, the resetting process can be easily executed even when the position of the image formed on the paper is shifted due to a shift in the axial direction of the registration roller R over time.

In step S102, the control unit 100 conveys a plurality of sheets in order to confirm the sheet conveyance position. The position of the edge of the conveyed paper is detected by a deviation detection sensor 565.
In step S <b> 103, the control unit 100 acquires and stores the position of the edge of the sheet detected by the deviation detection sensor 565. The control unit 100 performs the same process for a plurality of sheets.

  In step S <b> 104, the control unit 100 calculates the average position of the stored edge portions of the plurality of sheets and sets it as a reference position. Since the set reference position reflects the conveyance state of the sheet, the deviation of the sheet itself is less likely to occur. As a result, the deviation of the paper can be easily corrected.

  In step S105, the control unit 100 sets an image writing range based on the reference position set in step S104. Note that if there is no change in the paper feed tray, it is considered that the paper passage position does not change, so the resetting of the image writing range may be omitted. In this case as well, it can be said that the writing range is set based on the newly set reference position.

  As described above, the image forming apparatus 1 is set with a predetermined writing range, and based on the writing range, the image forming unit 40 that forms an image on the sheet, and the axial direction can be adjusted upstream of the image forming unit 40. And a registration roller R (driving roller 561 and driven roller 562) that conveys the sheet to the image forming unit 40, and a deviation detection sensor 565 (deposition) that detects a position in the width direction of the sheet passing through the registration roller R. Based on the detection result by the deviation detection sensor 565 and the deviation detection sensor 565, the deviation correction part (swing) that corrects the position in the width direction of the paper by moving the registration roller R in the width direction by the amount of deviation from the reference position. The motor 563 and the power transmission unit 564) and the reference position for correcting the deviation of the paper are set, and the writing range is set based on the set reference position. It includes a section 100, a.

  According to the image forming apparatus 1, the reference position and the image writing range for correcting the misalignment of the sheet can be reset as necessary, so that the sheet conveyance position and the image writing position can be set. The shift can be easily eliminated, and the image quality can be improved.

As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and can be changed without departing from the gist thereof.
For example, when the control unit 100 is configured to detect that the axial direction of the registration roller R has changed and the axial direction of the registration roller R has changed (actually, the axial direction of the registration roller R is adjusted). If the registration unit is replaced, the resetting process may be automatically executed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 20 Operation display part 21 Display part 22 Operation part 30 Image processing part 40 Image forming part 50 Paper conveyance part 51 Paper feed part 53 First conveyance part 56 Registration roller part 561 Driving roller (registration roller) )
562 driven roller (registration roller)
563 Oscillation motor (deviation correction part)
564 Power transmission part (deviation correction part)
565 Deviation detection sensor (deviation detection unit)
60 Fixing unit 100 Control unit R Registration roller

Claims (6)

A predetermined writing range is set, and an image forming unit that forms an image on a sheet based on the writing range;
A registration roller disposed upstream of the image forming unit so as to be adjustable in axial direction, and for conveying paper to the image forming unit;
A deviation detection unit that detects a position in the width direction of the sheet passing through the registration roller;
Based on the detection result by the deviation detection unit, the deviation correction unit that moves the registration roller in the width direction by the amount of deviation from the reference position and corrects the position in the width direction of the paper;
An image forming apparatus comprising: a control unit that sets the reference position and sets the writing range based on the set reference position.   The image forming apparatus according to claim 1, wherein the control unit sets an average sheet passing position when a plurality of sheets are passed as the reference position.   3. The control unit according to claim 1, wherein the control unit sets the reference position and the writing range again based on an operation signal that instructs resetting of the reference position and the writing range. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the control unit sets the reference position and the writing range again when the axial direction of the registration roller changes. .   5. The image forming apparatus according to claim 1, wherein the deviation detection unit includes a line sensor and is disposed in parallel with the registration roller. A first position for correcting a deviation in the width direction of the paper and a writing range based on the reference position;
A second step of detecting the position in the width direction of the conveyed paper;
A third step of moving the paper in the width direction by an amount of deviation from the reference position based on the detection result of the second step;
And a fourth step of forming an image on a sheet based on the writing range.

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