JP2019028329A - Image formation device and control method - Google Patents

Abstract

To suppress displacement of an image position with respect to a sheet due to sub-scanning curvature.SOLUTION: An image formation device comprises: image formation units 10M, 10C and 10K (image writing-out parts) for writing out an image; a position detection sensor SE2 (detection part), which is disposed on a second surface path provided for forming an image on a rear surface or a front surface of a sheet in an overlapping manner, i.e. on the image surface side of a sheet, for detecting image information including a position of a side end portion of the sheet and an image transferred to the sheet; and a control unit 11 for causing the image formation units 10M, 10C and 10K to execute image writing-out on the basis of the detection result detected by the position detection sensor SE2 and predetermined writing-out control information.SELECTED DRAWING: Figure 4

Description

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

  In recent years, multifunctional image forming apparatuses having functions such as printers, scanners, copiers, and fax machines have been widely used. In an image forming apparatus, paper is transported from a paper feed unit or a reverse path to a transfer unit during image formation. (There is also a case of direction). When the printing process is performed in such a state where the paper is misaligned, there is a problem that the image forming position on the paper is deviated from the original proper position.

Therefore, in order to accurately align the image and the paper in consideration of the deviation of the paper, the registration rocking that corrects the deviation of the paper by sandwiching the paper with the registration roller and swinging in the paper width direction is performed. Dynamic correction is performed.
For example, in Patent Document 1, a registration roller is disposed on the upstream side of the image forming position, and a line sensor is disposed on the downstream side of the registration roller and on the upstream side of the secondary transfer roller. An image forming apparatus that corrects a deviation of a sheet by swinging the sheet in the sheet width direction based on the deviation amount of the sheet is disclosed.

JP 2013-91563 A

  However, since the conventional technology including Patent Document 1 employs a configuration in which a line sensor is arranged on the downstream side of the registration roller and the upstream side of the secondary transfer roller, after the paper fixing process, When image formation is performed on the back side of the paper or on the front side of the paper, misalignment of the transport rollers in the path (reversing path, etc.) provided for that purpose, and the roller diameter between the front side and the back side of each transport roller Due to this difference, it is not possible to detect a deviation between the paper and the image position due to the sub-scanning bending in which the paper is bent from the middle in the transport direction (sub-scanning direction). Accordingly, when image formation is performed on the back surface of the paper or on the front surface of the paper, the image position relative to the paper may be shifted because the shift between the paper and the image position due to the sub-scanning curve cannot be accurately suppressed.

  An object of the present invention is to suppress a shift of an image position with respect to a sheet due to a sub-scanning curve.

The invention described in claim 1 has been made to achieve the above object,
In an image forming apparatus that conveys a sheet to an image transfer position by a transfer unit and transfers the image to the sheet,
An image writing unit for writing the image;
A second path provided to form an image on the back surface of the paper or on the front surface of the paper, and is disposed on the image surface side of the paper, and the position of the side edge of the paper and the paper A detection unit for detecting image information of the image transferred to
A control unit that executes writing of the image by the image writing unit based on a detection result detected by the detection unit and predetermined writing control information;
It is characterized by providing.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The second surface path includes a recirculation path provided to form an image on the surface of the sheet.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect,
The recirculation path is provided with a transport unit for transporting the paper.

According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect,
The recirculation path is a path that passes through a lower portion of a paper feed tray provided below the transfer section and a fixing section that fixes the image transferred onto the paper by the transfer section.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect,
The detection unit is arranged below the paper feed tray.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The detection unit is arranged on the upstream side of a reversing roller that guides the paper to a reversing path provided for image formation on the back surface of the paper.

The invention described in claim 7
An image writing unit for writing an image, and a second-side path provided to form an image on the back surface of the paper or on the front surface of the paper, and is disposed on the image surface side of the paper, A method for controlling an image writing unit in an image forming apparatus, comprising: a detection unit configured to detect a position of an edge and image information of an image transferred to the paper;
And a step of executing the writing of the image by the image writing unit based on a detection result detected by the detection unit and predetermined writing control information.

  According to the present invention, it is possible to suppress the shift of the image position with respect to the paper due to the sub-scanning curve.

1 is a configuration diagram schematically illustrating an image forming apparatus according to an embodiment. It is the figure which looked at an example of the structure which has arrange | positioned the position detection sensor in the upstream of the inversion roller from the bottom face side. 2 is a block diagram schematically showing a configuration of a control system of the image forming apparatus according to the present embodiment. FIG. It is a flowchart which shows the write-out control process performed in this embodiment. It is a figure which shows the example of data storage of a write-out control table. 1 is a configuration diagram schematically illustrating an image forming apparatus provided with two position detection sensors. It is a block diagram which shows the modification of a recirculation path | route typically. FIG. 9 is an explanatory diagram illustrating a paper swing process by a registration roller.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[Configuration of Image Forming Apparatus 100]
First, the configuration of the image forming apparatus 100 in the present embodiment will be described.
FIG. 1 is a configuration diagram schematically illustrating an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 is an electrophotographic image forming apparatus 100 such as a copying machine, and forms a full-color image by arranging a plurality of photoconductors facing one intermediate transfer belt in the vertical direction. This is a so-called tandem color image forming apparatus.

  The image forming apparatus 100 is mainly composed of a document reading device SC, an image forming unit 10, a fixing device 50, an image reading unit 60, and a control unit 11, and these are housed in one casing.

  The document reader SC scans and exposes an image of the document with the optical system of the scanning exposure device, reads the reflected light with a line image sensor, and obtains an image signal. This image signal is subjected to processing such as A / D conversion, shading correction, and compression, and then input to the control unit 11 as image data. Note that the image data input to the control unit 11 is not limited to the data read by the document reading device SC. For example, the image data is received from a personal computer connected to the image forming device 100 or another image forming device by the communication unit 13. It may be what you did.

  The image forming unit 10 includes four sets of image forming units (image writing units) 10Y, 10M, 10C, and 10K, an intermediate transfer belt 6, a secondary transfer roller 9, and the like. The image forming units 10Y, 10M, 10C, and 10K are an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and an image that forms a cyan (C) image. The forming unit 10C includes an image forming unit 10K that forms a black (K) image.

  The image forming unit 10Y includes a photosensitive drum 1Y and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y arranged around the photosensitive drum 1Y. Similarly, the image forming units 10M, 10C, and 10K include the photosensitive drums 1M, 1C, and 1K and charging units 2M, 2C, and 2K, optical writing units 3M, 3C, and 3K, and developing devices 4M, arranged around the photosensitive drums 1M, 1C, and 1K. 4C, 4K and drum cleaners 5M, 5C, 5K.

  The surfaces of the photosensitive drums 1Y to 1K are uniformly charged by the charging units 2Y to 2K, and latent images are formed on the photosensitive drums 1Y to 1K by scanning exposure by the optical writing units 3Y to 3K. Is done. Further, the developing devices 4Y to 4K develop latent images on the photosensitive drums 1Y to 1K by developing with toner. Thereby, a toner image of a predetermined color corresponding to any one of yellow, magenta, cyan, and black is formed on the photosensitive drums 1Y to 1K. The toner images formed on the photosensitive drums 1Y to 1K are sequentially transferred to predetermined positions on the rotating intermediate transfer belt 6 by primary transfer rollers 7Y, 7M, 7C, and 7K.

  The toner image composed of each color transferred onto the intermediate transfer belt 6 is transferred by the secondary transfer roller 9 to the paper P conveyed at a predetermined timing by a paper conveyance unit 20 described later. The secondary transfer roller 9 is a pressure contact member that forms a nip portion (hereinafter referred to as “transfer nip portion”) by being disposed in pressure contact with the intermediate transfer belt 6.

  The paper transport unit 20 transports the paper P along the transport path of the paper P. The paper P is stored in the paper feed tray 21, and the paper P stored in the paper feed tray 21 is taken in by the paper feed unit 22 and sent out to the transport path. Alternatively, the paper P is stored in a paper feed tray included in an external paper feed device (not shown) connected to the image forming apparatus 100 via the external paper feed ports 81 and 82 and the like. The held paper P is supplied from the paper supply device to the image forming apparatus 100 via the external paper supply port 81 or 82 and is sent out to the conveyance path. For example, the long paper is supplied from the external paper feeder to the image forming apparatus 100 via the external paper feed port 81 or 82.

  In this transport path, a plurality of transport means for transporting the paper P is provided upstream of the transfer nip portion. Each of the conveying means is composed of a pair of pressure-contacted rollers, and conveys the paper P when at least one of the rollers is rotationally driven through a driving mechanism mainly composed of an electric motor. In addition, the pair of rollers constituting the individual conveying means is configured so that the state between the rollers can be switched between a pressure contact state and a separated state.

  In the present embodiment, intermediate conveyance rollers 23 to 25, a loop roller 26, and a registration roller 27 are provided as conveyance means from the upstream side to the downstream side of the conveyance path of the paper P. In addition to the configuration of the pair of rollers, the conveyance unit can widely employ a configuration including a pair of rotating members such as a combination of belts or a combination of a belt and a roller.

  In such a transport path, the paper P fed from the paper feed tray 21 or the paper feed tray of the paper feeder is fed by a plurality of intermediate transport rollers 23 to 25 and a loop roller 26 provided from the upstream side to the downstream side. It is sequentially transported and travels along the transport path. When the leading edge of the sheet P approaches the registration roller 27, the sheet P conveyed by the intermediate conveyance rollers 23 to 25 and the loop roller 26 is abutted against the registration roller 27 in a rotation stopped state, and the loop roller 26 is predetermined. By continuing the rotation for the time, a loop is formed on the paper P. By this loop forming action, the bending of the leading edge of the paper P is corrected (skew correction).

  Next, when the registration roller 27 starts rotating at a predetermined timing so as to synchronize with the toner image carried by the intermediate transfer belt 6, the intermediate transport rollers 23 to 25 and the loop roller 26 are switched from the pressure contact state to the separated state. It is done. That is, after the intermediate conveyance rollers 23 to 25 and the loop roller 26 are shifted to the separated state, the paper P is conveyed only by the registration roller 27. The registration roller 27 conveys the paper P to the transfer nip portion of the intermediate transfer belt 6 as an image carrier and the secondary transfer roller 9 as a transfer portion.

  A registration sensor SE1 and a position detection sensor SE2 are provided on the transport path, and the operations of the image forming units 10Y, 10M, 10C, and 10K are controlled by the control unit 11 based on detection results of these sensors.

  A registration sensor SE <b> 1 is disposed between the registration roller 27 and the loop roller 26 in the transport path. The registration sensor SE1 detects the arrival of the leading edge of the paper P at the detection position of the registration sensor SE1 (a position a predetermined distance before the registration roller 27). The detection result of the registration sensor SE1 is used for detecting the rotation start timing of the registration roller 27 and the like.

  As shown in FIGS. 1 and 2, a position detection sensor SE2 is provided on the upstream side of the reverse roller 31 in the paper transport direction FD and on the image surface side of the paper P (below the transport path). It has been. The position detection sensor SE2 includes, for example, a linear image sensor (for example, a CCD line sensor) in which a plurality of light receiving elements are linearly arranged along the paper width direction CD, an optical system, a light source, and the like. The position detection sensor SE <b> 2 is a detection unit that detects the position in the sheet width direction CD of the side edge of the sheet P that is subjected to the fixing process by the fixing device 50 and is conveyed to the reverse roller 31. In this embodiment, since the position detection sensor SE2 can read the paper P from the image surface side, the image position of the toner image transferred to the paper P (that is, where the toner image is formed with respect to the paper P). Can be detected as image information. The detection result of the position detection sensor SE2 is output to the control unit 11 and used for determining the write control information of the image forming units 10Y, 10M, 10C, and 10K.

  The fixing device 50 is a device that performs a fixing process on the paper P on which the toner image is transferred, that is, the paper P sent out from the transfer nip portion. For example, the fixing device 50 includes a pair of fixing members (eg, a pair of rollers) It is comprised with the heater which heats one or both of the members. The fixing device 50 fixes the toner image onto the paper P through the action of the pressure applied by the pair of fixing members and the heat of the fixing member in the conveyance process of the paper P.

  The paper P that has been subjected to fixing processing by the fixing device 50 is read by an image reading unit (ICCU) 60 and then discharged by a paper discharge roller 28 to a paper discharge tray 29 attached to the outer side surface of the housing. . In addition, when image formation is performed on the back surface of the paper P or on the front surface of the paper P, the paper P that has finished image formation on the front surface of the paper is read by the image reading unit 60 and is then moved downward by the switching gate 30. To the reversing roller 31.

When image formation is performed on the back surface of the paper P, the reversing roller 31 pinches the rear end of the conveyed paper P, reverses the paper P by reverse feeding, and sends it to the reversing path R1. The inversion path R1 is a path provided for image formation on the back surface of the paper P. The paper P sent out to the reversing path R1 is transported by a plurality of transport means 32 in the reversing path R1 and returns the paper P to the transfer nip portion via the registration roller 27.
On the other hand, when the image is formed on the surface of the paper P, the reversing roller 31 sends the paper P to the recirculation path R2 as it is without running backward. The recirculation path R <b> 2 is a path provided to form an image on the surface of the paper P in an overlapping manner. The paper P sent out to the recirculation path R2 is transported by a plurality of transport means (transport parts) 33 in the recirculation path R2, and the paper P is returned to the transfer nip portion via the registration rollers 27. In addition, when the paper P sent out to the recirculation path R2 is a long sheet, the recirculation path R2 can be transported by the reversing roller 31, so that a plurality of transport means 33 is not provided in the recirculation path R2. It may be.

  The paper discharge roller 28, the switching gate 30, the reversing roller 31, the transporting means 32 in the reversing path R1, and the transporting means 33 in the recirculation path R2 also constitute the paper transporting unit 20 described above. In the present embodiment, the path that has been switched by the switching gate 30 and that rejoins the original transport path (the transport path on which image formation has been performed on the front surface (first surface) of the paper P) (that is, the path) , A route including the reversal route R1 and the recirculation route R2) is referred to as a “second surface route”. Therefore, even in a so-called recirculation case in which image formation is performed on the front surface of the paper P (a case in which image formation is not performed on the back surface (second surface) of the paper P), a path for transporting the paper P at that time ( The recirculation route R2) is referred to as a second surface route. That is, the second-side path is a path provided for image formation on the back surface of the paper P or on the front surface of the paper P.

  The image reading unit 60 includes, for example, a linear image sensor (for example, a CCD line sensor), an optical system, a light source, and the like. The image reading unit 60 reads the paper P on which the toner image is transferred, and controls the obtained read image. 11 is output. In the present embodiment, the image reading unit 60 can measure the color of the toner image on the paper P, but is not particularly limited as long as at least the area of the paper P and the area of the toner image can be recognized. In the present embodiment, the image reading unit 60 is disposed downstream of the fixing device 50 and on the near side where the conveyance path is switched by the switching gate 30, but the secondary transfer roller 9 (transfer nip unit) The arrangement position is not particularly limited as long as it is a position that can read both sides of the paper P (which may be one side at a time). Of course, it may be arranged downstream of the image forming apparatus 100 as an optional device.

FIG. 3 is a block diagram schematically showing the configuration of the control system of the image forming apparatus 100 according to the present embodiment.
As shown in FIG. 3, the control unit 11 includes a storage unit 12, a communication unit 13, an operation unit 14, a document reading device SC, an image forming unit 10, a sheet conveying unit 20, a fixing device 50, an image reading unit 60, a registration sensor. It is connected to SE1, position detection sensor SE2, and environmental sensor SE3. The control unit 11 includes a CPU, a RAM, and the like. The CPU of the control unit 11 reads the system program and various processing programs stored in the storage unit 12 and expands them in the RAM, and centrally controls the operations of the respective units of the image forming apparatus 100 according to the expanded programs. For example, when a job execution command is input from the operation unit 14, the control unit 11 executes a job and forms a toner image on the paper P based on image data input by the document reading device SC or the communication unit 13. Take control. Further, when a job execution command is input from the operation unit 14, the control unit 11 executes a writing control process and performs writing control of the image forming units 10Y, 10M, 10C, and 10K that are executing the job.

The storage unit 12 is configured by a nonvolatile semiconductor memory, an HDD (Hard Disk Drive), or the like, and stores various programs executed by the control unit 11 as well as parameters and data necessary for each unit.
For example, the storage unit 12 stores a write control table 121 (see FIG. 5).

  The communication unit 13 includes various interfaces such as a NIC (Network Interface Card), a MODEM (Modulator-DEModulator), and a USB (Universal Serial Bus), and connects to an external device.

  The operation unit 14 outputs various information set by the user to the control unit 11. As the operation unit 14, for example, a touch panel capable of performing an input operation according to information displayed on the display can be used. Through the operation unit 14, the user sets the printing conditions, that is, the type of paper P (for example, basis weight, size, paper quality, etc.), paper feed tray to be used, image density, magnification, presence / absence of duplex printing, and the like. be able to. Further, the user can input a job execution command and an operation instruction in the adjustment mode through the operation unit 14. The control unit 11 can display various messages to the user via the operation unit 14 by controlling the operation unit 14.

  The environment sensor SE3 includes, for example, a temperature sensor, a humidity sensor, and the like, detects the temperature and humidity in the housing of the image forming apparatus 100, and outputs the detection result to the control unit 11.

[Operation of Image Forming Apparatus 100]
Next, the operation of the image forming apparatus 100 in this embodiment will be described.
FIG. 4 is a flowchart showing processing (writing control processing) for shifting the image writing position by the image forming units 10Y, 10M, 10C, and 10K. The processing shown in this flowchart is executed in cooperation with the program stored in the control unit 11 and the storage unit 12 in accordance with a job execution command from the user.

First, the control unit 11 determines whether or not the leading end of the paper P is detected by the position detection sensor SE2 (step S1).
When the control unit 11 determines that the leading edge of the paper P has been detected by the position detection sensor SE2 (step S1; YES), the position of the side edge of the paper P at a plurality of positions (for example, two points) by the position detection sensor SE2. The detection result is acquired (step S2). As a result, it is possible to detect variations in paper conveyance by the conveyance rollers arranged in the second-surface path.
On the other hand, when it is determined that the leading edge of the paper P is not detected by the position detection sensor SE2 (step S1; NO), the control unit 11 waits until the leading edge of the paper P is detected by the position detection sensor SE2.

Here, the variation in the position of the side edge of the paper P varies depending on the conditions relating to the paper conveyance (predetermined conditions that affect the paper conveyance). Therefore, it is necessary to change the writing control information (the shift amount of the image writing position) for each condition related to the sheet conveyance in accordance with the variation in the position of the side edge of the sheet P. The conditions related to paper conveyance include, for example, the paper type (basis weight, size, paper quality, etc.), environment (eg, temperature and humidity), paper surface (front / back) on which an image is formed, and / or paper feed. This is the condition of the tray. For example, if the paper type is thin paper, the paper P tends to bend more easily than plain paper or thick paper, so the shift amount needs to be increased.
In the present embodiment, a table storing the shift amount of the image writing position is stored in the storage unit 12 for each condition relating to the above-described sheet conveyance. That is, the shift amount of the image writing position is set according to the conditions related to the sheet conveyance. FIG. 5 shows an example of a table (writing control table 121) that stores the shift amount of the image writing position for each paper type.

Next, the control unit 11 determines the image forming units 10Y, 10M, 10C, and 10K at each predetermined writing timing based on the detection result by the position detection sensor SE2 and the predetermined writing control information (writing control table 121). Is determined (step S3).
In the present embodiment, the image forming units 10Y, 10M, 10C, and 10K are controlled to write at a plurality of predetermined timings (referred to as writing timings). Write control information used at the write timing (timing 1 to n) is stored. Here, in order to accurately write out the toner image at the optimum image position on the paper P, in the writing control table 121, writing is performed for each paper type, each environment, each paper surface, each paper feed tray, or each combination thereof. It is preferable that the write control information used at the timing (timing 1 to n) is stored.
As described above, by storing the write control table 121 in the storage unit 12, write control information can be appropriately determined according to each condition.

  The write control table 121 shown in FIG. 5 illustrates a configuration for storing the offset amount from the image write position (the center position of the paper in the paper width direction), but is not limited to this. The shift amount of the image writing position Wc may be stored.

  In the present embodiment, since the position detection sensor SE2 is provided on the image surface side of the paper P, the image information of the toner image can be acquired. Accordingly, the write control information of the image forming units 10Y, 10M, 10C, and 10K may be determined based on the detection result of the position of the sheet side edge and the position of the toner image by the position detection sensor SE2. For example, the distance between the sheet side edge and the toner image at each writing timing is calculated based on the detection result of the position of the sheet side edge and the position of the toner image detected by the position detection sensor SE2. Then, the difference (deviation amount) between the calculated distance and the distance between the sheet side edge and the toner image when the toner image is arranged at the optimum image position is calculated, and each writing timing is calculated based on the calculated deviation amount. Determine the write control information in. Thereby, the toner image can be aligned with the optimum image position with higher accuracy.

Next, the control unit 11 determines whether or not the writing timing of the image forming units 10Y, 10M, 10C, and 10K has arrived (step S4). In the present embodiment, for example, a plurality of writing timings are determined in advance (for example, at substantially equal intervals) such as t1 seconds after the timing when the position detection sensor SE2 detects the leading edge of the paper P, t2 seconds later, and so on. It has been.
When it is determined that the writing timing has arrived (step S4; YES), the control unit 11 uses the image forming units 10Y, 10M, 10C, and 10K based on the writing control information determined in step S3 according to the writing timing. Writing is executed (step S5).
On the other hand, when the control unit 11 determines that the writing timing has not arrived (step S4; NO), the control unit 11 waits until the writing timing has come.

Next, the control unit 11 determines whether or not writing at the final writing timing is finished (step S6). For example, based on the paper size of the paper P, the elapsed time after the position detection sensor SE2 detects the leading edge of the paper P, and the conveyance speed, it is determined whether or not the writing at the final writing timing is completed.
When it is determined that the writing at the final writing timing has been completed (step S6; YES), the control unit 11 determines whether or not the transfer to the final page has been completed (step S7).
On the other hand, when the control unit 11 determines that the writing at the final writing timing has not ended (step S6; NO), the control unit 11 returns to step S4, waits for the next writing timing, and when the writing timing arrives, The process for executing the writing by the image forming units 10Y, 10M, 10C, and 10K is repeated.

Next, when it is determined that the transfer to the last page has been completed (step S7; YES), the control unit 11 ends the writing control process.
On the other hand, if the control unit 11 determines that the transfer to the last page has not been completed (step S7; NO), the control unit 11 returns to step S1.

As described above, the image forming apparatus 100 according to the present embodiment performs image formation with the image forming units 10M, 10C, and 10K (image writing unit) for writing an image and the back surface of the paper or the top of the paper. A position detection sensor SE2 (detection unit) that is disposed on the image surface side of the sheet and detects the position of the side edge of the sheet and the image information of the image transferred to the sheet. And a control unit 11 for executing image writing by the image forming units 10M, 10C, and 10K based on the detection result detected by the position detection sensor SE2 and predetermined writing control information.
Therefore, according to the image forming apparatus 100 according to the present embodiment, image formation is performed based on the deviation of the position of the side edge portion of the paper P detected by the second path and the deviation of the image transferred to the paper P. Since the image writing by the units 10M, 10C, and 10K can be executed and the image position with respect to the paper P can be adjusted, the deviation of the toner image position with respect to the paper P due to the sub-scanning bending can be suppressed with high accuracy. In particular, it is more effective when the paper is long in the paper conveyance direction, such as long paper.

Further, according to the image forming apparatus 100 according to the present embodiment, the second-side path includes the recirculation path R <b> 2 that is provided to form an image on the surface of the sheet.
Therefore, according to the image forming apparatus 100 according to the present embodiment, the image position with respect to the paper P can be adjusted even when the image is formed on the surface of the paper P. The toner image position shift with respect to the toner image can be more reliably suppressed.

Further, according to the image forming apparatus 100 according to the present embodiment, the recirculation path R2 is provided with the conveyance unit 33 (conveyance unit) for conveying the paper.
Therefore, according to the image forming apparatus 100 according to the present embodiment, the recirculation path R2 can be transported even when the paper P is a standard paper, so that it overlaps the surface of the paper P regardless of the paper length. Image formation can be performed.

Further, according to the image forming apparatus 100 according to the present embodiment, the position detection sensor SE2 is located upstream of the reversing roller 31 that guides the sheet to the reversing path R1 provided for image formation on the back surface of the sheet. Has been placed.
Therefore, according to the image forming apparatus 100 according to the present embodiment, the position and the image information of the side edge of the paper P after being reversed by the reversing roller 31 can be detected, so Thus, it is possible to acquire the information on the toner image, and to suppress the displacement of the toner image position with respect to the paper P due to the sub-scanning curve with higher accuracy.

  As mentioned above, although concretely demonstrated based on embodiment which concerns on this invention, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.

  For example, in the above embodiment, the configuration (see FIGS. 1 and 2, etc.) in which the position detection sensor SE2 is disposed in the vicinity (upstream side) of the reversing roller 31 is described as an example. However, the present invention is limited to this. It is not a thing. That is, any configuration may be used as long as the position detection sensor SE2 is disposed on the image surface side of the sheet P of the second path, for example, the downstream side of the reversing roller 31, the downstream side of the switching gate 30, or the reconfiguration. The structure arrange | positioned in the exit vicinity etc. of circulation path | route R2 may be sufficient. However, as the position where the position detection sensor SE2 is disposed, the position where the position detection sensor SE2 is disposed on the upstream side of the reversing roller 31 as much as possible is secondary transfer after detection by the position detection sensor SE2 and writing by the image forming units 10Y, 10M, 10C, and 10K. Since sufficient time can be ensured until transfer by the roller 9, it is more preferable.

  Moreover, in the said embodiment, although the structure which arrange | positions position detection sensor SE2 only in the upstream of the inversion roller 31 was illustrated and demonstrated, it is not limited to this. That is, it is only necessary to have one position detection sensor SE2 on the image surface side of the sheet P of the second-side path. For example, as shown in FIG. 6, in addition to the position detection sensor SE2, a second detection sensor SE2 is provided. You may make it employ | adopt the structure which arrange | positions position detection sensor SE21.

As described above, in the writing control of the image forming units 10Y, 10M, 10C, and 10K, when the two position detection sensors SE2 and SE21 are used, the writing operation is determined based on the individual detection results. Alternatively, the writing operation may be determined using two detection results.
For example, when the writing operation is determined based on the individual detection result, first, the writing by the image forming units 10Y, 10M, 10C, and 10K is executed based on the detection result of the position detection sensor SE2, and then the position detection sensor SE21. Based on this detection result, processing for executing writing by the image forming units 10Y, 10M, 10C, and 10K may be performed.
For example, when the writing operation is determined based on the two detection results, the inclination (sub-scanning curve) of the paper P is calculated, and the image forming units 10Y, 10M, and 10C are calculated based on the calculated inclination of the paper P. , 10K may be executed. Note that the inclination of the paper P is defined as “X1, X2 in the paper width direction” is “X1, X2” when the coordinates of the two paper conveyance directions FD at which the position of the edge of the paper is detected are X1 and X2, respectively. It can be calculated by dividing by “the transport distance between X2”. Thus, by calculating the inclination of the paper P based on the two detection results, the number of detections of the position of the paper side edge can be reduced, so that the processing speed can be improved.

  Moreover, in the said embodiment, although the structure which provides the recirculation path | route R2 in the downstream of the paper conveyance direction FD of the inversion roller 31 is illustrated and demonstrated, it is not limited to this. For example, as shown in FIG. 7, on the upstream side of the sheet conveyance direction FD of the reverse roller 31, a path (image reverse roller 31, reverse path R 1, etc.) for performing image formation on the back surface of the paper P by the switching gate 30 A A configuration in which the paper P is transported to any one of a path (recirculation path R3 and the like) for forming an image on the surface of the paper P may be adopted. FIG. 7 illustrates a configuration in which the recirculation path R <b> 3 passes below the paper feed tray 21.

In FIG. 7, instead of disposing the position detection sensor SE <b> 2 in the vicinity (upstream side) of the reversing roller 31, the position detection sensor SE <b> 22 is provided on the upstream side in the sheet conveyance direction FD of the switching gate 30 </ b> A, A configuration in which the position detection sensor SE23 is provided is illustrated.
As described above, by providing the position detection sensor SE22 on the upstream side of the sheet conveyance direction FD of the switching gate 30A, the side end portion of the sheet P regardless of whether the reversing path R1 or the recirculation path R3 is conveyed. Therefore, it is possible to more reliably suppress the deviation of the toner image position with respect to the paper P due to the sub-scanning curve.
In addition, by providing the position detection sensor SE23 below the paper feed tray 21, the influence of the temperature (heating) by the fixing device 50 or the like can be eliminated at the time of detection by the position detection sensor SE23 or the like. The position and image information of the side edge of the paper P can be detected.

  In addition, the said structure is an example and the structure which provides any one among position detection sensors SE22 and SE23 may be sufficient. Moreover, you may make it combine with the structure which provides a position detection sensor in the other position of a 2nd surface path | route.

  Further, the shift amount of the image writing position Wc does not need to be determined based on the position matched with the image writing center, and can be any position as long as the toner image can be finally formed at the optimum image position in the paper P. You may make it determine based on a position. In other words, any configuration may be used as long as an image is formed on the paper P at the optimum image position when the image is printed on the paper P.

  In the above embodiment, control is performed to shift the image writing position by the image forming units 10Y, 10M, 10C, and 10K based on the detection result detected by the position detection sensor SE2 and the predetermined writing control information. However, the present invention is not limited to this. For example, in addition to control for shifting the image writing position by the image forming units 10Y, 10M, 10C, and 10K, control for swinging the registration roller 27 may be performed.

  FIG. 8 is an explanatory view showing the swinging process of the paper P by the registration roller 27. The registration roller 27 is configured to be swingable in a paper width direction CD (a direction perpendicular to the paper transport direction (sub-scanning direction) FD). A driving mechanism 34 mainly composed of an electric motor is connected to the registration roller 27, and can be moved in the paper width direction CD starting from a predetermined home position by being driven by the driving mechanism 34. .

  The registration roller 27 can move the conveyed paper P along the paper width direction CD by moving along the paper width direction CD in accordance with a passage period during which the paper P passes through the registration roller 27 (oscillating). processing). Thereby, the registration roller 27 adjusts the transport position of the paper P in the paper width direction CD so as to be aligned with the position of the transferred toner image. Here, the position where the side edge of the paper P should pass in the paper width direction CD is called a target position Tp. The target position Tp is optimal in the positional relationship between the paper P and the toner image if the side edge of the paper P passes through the position in the paper width direction CD (for example, the center of the paper P in the width direction). The registration roller 27 adjusts the transport position of the paper P in the paper width direction CD so that the side edge of the paper P becomes the target position Tp. To do. The position of the toner image where the positional relationship between the paper P and the toner image is optimal is called the optimal image position.

  For example, by controlling the image writing position by the image forming units 10Y, 10M, 10C, and 10K, the absolute value of the image with respect to the paper is corrected, and then the control to swing the registration roller 27 is performed. Thus, the variation in the side edge of the paper P may be reduced. Thereby, since the rocking | fluctuation amount of the registration roller 27 can be reduced, durability of the registration roller 27 can be improved.

  In the above-described embodiment, the color image forming apparatus that primarily transfers the image formed on the photosensitive drum to the intermediate transfer roller and transfers the image from the intermediate transfer roller to the paper by the secondary transfer roller has been described as an example. However, the present invention is also applicable to a monochrome image forming apparatus that directly transfers an image from a photosensitive drum to a sheet by a transfer roller.

  In the above embodiment, an electrophotographic image forming apparatus is described as an example. However, the present invention is not limited to this. For example, an ink jet image forming apparatus that records an image on a recording medium by ejecting ink from a nozzle onto the recording medium and landing in a desired pattern (for example, the ink jet recording apparatus includes a predetermined energy beam). The present invention is applied to an apparatus in which ink that is cured by the above method is ejected from a nozzle and the ink on the ejected recording medium is cured by irradiating the predetermined energy ray to cure the ink on the recording medium. It is also possible.

  In the above description, an example in which a non-volatile memory, a hard disk, or the like is used as a computer-readable medium for the program according to the present invention is disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. Further, a carrier wave (carrier wave) is also applied as a medium for providing program data according to the present invention via a communication line.

  In addition, the detailed configuration and detailed operation of the image forming apparatus can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 11 Control part 12 Memory | storage part 121 Writing control table 13 Communication part 14 Operation part SC Original reading apparatus 10 Image forming part 10Y, 10M, 10C, 10K Image forming unit (image writing part)
9 Secondary transfer roller (transfer section)
20 Paper transport unit 27 Registration roller 31 Reverse roller 32 Transport unit 33 Transport unit (transport unit)
50 Fixing Device 60 Image Reading Unit SE1 Registration Sensor SE2, SE21 to SE23 Position Detection Sensor (Detection Unit)
SE3 Environmental sensor R1 Reverse path R2, R3 Recirculation path

Claims (7)

In an image forming apparatus that conveys a sheet to an image transfer position by a transfer unit and transfers the image to the sheet,
An image writing unit for writing the image;
A second path provided to form an image on the back surface of the paper or on the front surface of the paper, and is disposed on the image surface side of the paper, and the position of the side edge of the paper and the paper A detection unit for detecting image information of the image transferred to
A control unit that executes writing of the image by the image writing unit based on a detection result detected by the detection unit and predetermined writing control information;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the second surface path includes a recirculation path provided to form an image on the surface of the sheet.   The image forming apparatus according to claim 2, wherein a transport unit for transporting the paper is provided in the recirculation path.   The recirculation path is a path that passes through a lower portion of a paper feed tray provided below the transfer section and a fixing section that fixes an image transferred to the paper by the transfer section. Item 4. The image forming apparatus according to Item 2 or 3.   The image forming apparatus according to claim 4, wherein the detection unit is disposed below the paper feed tray.   6. The detection unit according to claim 1, wherein the detection unit is disposed on an upstream side of a reversing roller that guides the sheet to a reversing path provided to form an image on the back surface of the sheet. The image forming apparatus according to claim 1. An image writing unit for writing an image, and a second-side path provided to form an image on the back surface of the paper or on the front surface of the paper, and is disposed on the image surface side of the paper, A method for controlling an image writing unit in an image forming apparatus, comprising: a detection unit configured to detect a position of an edge and image information of an image transferred to the paper;
A control method including a step of executing writing of the image by the image writing unit based on a detection result detected by the detection unit and predetermined writing control information.

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