JP2010058376A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of detecting a paper width by means of a sensor mounted on a carriage, without paper feeding troubles due to paper floating-up from a platen or excessive-sucking, even when using paper whose size is unknown. <P>SOLUTION: The image forming apparatus includes: a paper feeder; the platen 24; a suction device 19 that sucks and supports the paper on the platen; a head 15 that ejects the ink to the paper placed on the platen to form an image on the paper; the sensor that detects the width of the paper placed on the platen; and the carriage 16 where the head 15 and the sensor are loaded, for scanning in the width direction of the paper. The carriage 16 is retracted outside the image forming area of the platen 24, the suction force of the suction device 19 is controlled to be equal to or below a first determined value, then, the paper is fed onto the platen, and the paper is supported by the suction force of the suction device 19 controlled to be a second predetermined value, and then, the carriage 16 is scanned so as to detect the paper width by means of the sensor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art An ink jet image forming apparatus (ink jet printer) has an ink head mounted on a carriage that arranges paper at a predetermined position of a paper placement unit (called a platen) at the time of image formation and scans corresponding to the position. Ink is ejected to form an accurate image. Here, if the paper width or paper position on the platen does not correspond to the ink ejection position of the ink head, an image will not be formed on the paper, or ink will be ejected onto the platen and the platen will be contaminated. To do. For this reason, it is necessary to accurately place a predetermined sheet on the platen.

  In order to make the paper width or paper position on the platen correspond to the ink ejection position of the ink head, it is necessary to first grasp the paper width and control the scanning range of the carriage. It is also necessary to accurately grasp the position of the paper on the platen. Furthermore, it is necessary to prevent the paper from freely moving on the platen during image formation.

  Normally, in order to prevent the paper from moving freely on the platen, a large number of micro holes are provided in the platen, and the conveyed paper is sucked onto the platen by suction from the lower part of the platen with a suction fan or the like. is doing. On the other hand, the width of the conveyed paper and the position in the width direction are measured by a detection device such as an optical sensor to control the correspondence with the scanning position of the carriage. There are two types of paper width detecting devices: a type installed in a paper feeding device (including a conveying device) and a type mounted on a carriage, but it is preferable to use a carriage mounting type that is economical and easy to detect.

As an example of a carriage-mounted type detection apparatus, in Patent Document 1, in order to accurately detect the width of a sheet conveyed on a platen, a size detection unit is provided on the carriage to determine the size (width) of the sheet. An image forming apparatus for detection is disclosed. Further, in Patent Document 2, when detecting the paper edge by the sensor on the carriage, the detection time is shortened by increasing the carriage speed outside the section in which the paper edge is detected, thereby increasing the printing speed. An image forming apparatus is disclosed.
JP 2006-036429 A JP 2007-230721 A

  As described above, the position and size (width) of the sheet on the platen can be known by measuring the width and position of the sheet conveyed on the platen with a sensor. However, according to this method, the carriage scans on the paper conveyed on the platen whose paper size is unknown. In this case, it is necessary to fix the sheet on the platen with an appropriate suction force. If the suction force is insufficient, the sheet may be lifted, and when the carriage is scanned, the head and the sheet come into contact with each other, causing a paper jam or movement of the sheet. On the other hand, if the suction force from the platen is too strong, the leading edge of the conveyed paper is fixed on the platen, and the platen can no longer proceed smoothly on the platen. Since the paper is further pushed out from the upstream side of the transport path, a jam occurs near the entrance of the platen.

  Usually, the platen is provided with a large number of minute holes uniformly in the width direction, and the sheet is sucked onto the platen by sucking air from the back side of the platen through the minute holes by a fan. For this reason, for the paper having a wide width and close to the width of the platen, most of the micro holes are blocked by the paper, so that the suction force of the fan is relatively weak and prevents the paper from being excessively fixed on the platen. On the other hand, if the narrow holes on the platen are not clogged by the paper, the air can easily flow through the platen, and the paper should be affixed to the platen unless it is sucked strongly by a suction fan. I can't.

  That is, the suction force of the suction fan needs to be controlled in accordance with the sheet width. However, when the paper width is unknown, there is no index for controlling the suction force of the suction fan. For this reason, a sensor for detecting the paper width may be separately required. In this case, the meaning of mounting the paper width sensor on the carriage is lost.

  In view of the above problems, the object of the present invention is to prevent the paper from being lifted on the platen or causing a paper feeding trouble due to excessive suction, even if the width of the paper is unknown. An object of the present invention is to provide an image forming apparatus capable of detection.

  The present invention provides a paper feeding device capable of feeding paper having different widths, a platen on which paper fed from the paper feeding device is placed at an image forming position, and sucking and supporting the paper on the platen. A suction device, a head that forms an image by ejecting ink onto a paper placed on the platen, a detection device that detects the width of the paper on the platen, the head and the detection device are mounted, An image forming apparatus including a carriage that scans in a width direction of the paper, wherein the carriage is retracted outside an image forming area of the platen, and the suction force of the suction device is set to a first predetermined value or less. A sheet is fed onto a platen, the sheet is supported with the suction force of the suction device as a second predetermined value, the carriage is scanned, and the width of the sheet is detected by the detection device. Image forming apparatus A.

  In the image forming apparatus, if the paper size is determined and the paper is continuously supplied from the same paper feed unit, normal image formation is possible without detecting the paper size (width). is there. However, when the paper feeding device can supply a plurality of papers of different sizes (widths) and the device itself detects the width of the paper fed on the platen and executes image formation in accordance with this, the paper width It is necessary to provide a sensor (detection device) for detecting the above. The sensor may be on the paper feeding device side or on the carriage, but it is preferable to mount the sensor on the carriage in order to reduce the number of sensors or to make a simple sensor. However, when the paper width is detected by the sensor, the size of the paper is not known, and if the suction power of the suction device for the paper fed on the platen is too strong, the wide paper is transported by the suction force. When the first half of the sheet that has been brought into close contact with the platen is trying to further convey the second half of the sheet from the sheet feeding device, the sheet may buckle and jam. Also, for a small size paper, if the suction force is too weak, the paper may float and the paper and the head may come into contact with each other when the carriage is scanned.

  In the image forming apparatus of the present invention, for a paper whose paper size (width) is unknown, the carriage is retracted outside the printing area, and the suction force by the suction device is set to a first predetermined value or less. Even if the sheet is lifted, contact with the carriage and the head on the carriage can be prevented. Further, since the suction force by the suction device is equal to or less than the first predetermined value, if the first predetermined value is set as the suction force corresponding to the maximum width of the paper that is supposed to be supplied to the image forming device, the suction force The front half of the paper being conveyed is not so strong that the force is so strong that the paper is conveyed to a required position.

  Further, when the sheet fed onto the platen is conveyed to a position necessary for width detection, the conveyance of the sheet is stopped, and the suction force by the suction device is set to a second predetermined value. If the second predetermined value is set to the suction force corresponding to the minimum width of the paper that is supposed to be supplied to the image forming apparatus, the suction force is too weak for paper of all widths wider than this. Does not occur. If the carriage is scanned on the paper in this state, the paper does not come into contact with the carriage or the head due to the floating of the paper, and there is no worry about jamming, and the paper width can be detected by the detection device on the carriage.

  According to a preferred embodiment of the present invention, the first predetermined value is a suction force at the time of image formation on the maximum width paper that can be fed, and the second predetermined value is an image formation on the minimum width paper that can be fed. The image forming apparatus according to claim 1, wherein the image forming apparatus has a suction force at a time.

  As described above, the first predetermined value and the second predetermined value may be adjusted according to the paper width assumed in image formation, but the maximum width of paper that can be fed by the image forming apparatus itself. If the first predetermined value is set as the first predetermined value and the minimum width of the paper that can be fed is set as the second predetermined value, the setting need not be changed. The first predetermined value may be zero, that is, the suction device may be stopped.

  In a preferred aspect of the present invention, the image forming apparatus forms an image after detecting the width of the sheet by the detecting device when the width of the fed sheet is unknown.

  The image forming apparatus of the present invention does not always need to detect the paper width in image formation. When the paper width is continuously fed or the operator specifies the paper width, the paper width It is not necessary to carry out this detection operation, and it is only necessary to execute image formation following paper feeding by the paper feeding device onto the platen. The image forming apparatus of the present invention may perform the above-described sheet width detection operation when the width of the sheet to be fed is unknown.

  In a preferred aspect of the present invention, after the width of the sheet is detected by the detection device, the sheet is pulled back from the platen, the carriage is disposed at a position facing the width of the sheet on the platen, and the suction device is In the image forming apparatus, the sheet is fed onto a platen as a suction force corresponding to the width of the sheet, and the leading end of the sheet is detected by the detection device.

  In this image forming apparatus, the detection device can detect the width of the paper and the front end position in the paper conveyance direction. In this image forming apparatus, when the width of the paper is detected by the detection device, the fed paper is pulled back from the platen to the paper supply device, and the suction device is set to a suction force corresponding to the detected paper width. Then feed the paper again onto the platen. The carriage is scanned at a position opposite to the sheet width on the platen, and when the sheet is conveyed on the platen, the leading end in the sheet conveying direction is detected by the detection device. If the detection device detects the leading edge of the paper, the position of the paper on which the head should form an image can be specified based on this. Then, the paper can be used without waste.

  According to a preferred aspect of the present invention, the paper feeding device includes a plurality of paper feeding units, and the detecting device detects a paper width by detecting one end of the paper fed from a predetermined paper feeding unit. The image forming apparatus is characterized in that it calculates.

  Usually, the paper feeding device includes a continuous paper feeding device and a manual paper feeding device. Automatic paper feeders include rolls, folded continuous paper feeders, and automatic paper feeders for cut paper. The paper fed from these paper feeders depends on the scanning direction (paper width) on the platen. Direction). Further, since the size of the paper used is a standard paper such as JIS, the width of the paper is known in advance. With respect to the sheet fed from the automatic sheet feeder onto the platen, the sheet width can be detected by detecting the position of one end in the width direction that varies depending on the sheet size. If the paper width can be detected at one place, the detection and detection device can be simplified.

  In a preferred aspect of the present invention, the detecting device detects a position of a sheet on the platen, and the head is controlled in an image forming position according to the position of the sheet. .

  The detection device in this image forming apparatus can detect not only the paper width but also the position of the paper on the platen. The paper conveyed on the platen may be shifted in the width direction on the platen depending on the state of the paper feeding device and the paper feeding method. For this reason, it is possible to detect the position in the width direction (scanning direction) of the sheet and control the image forming position by the head by scanning the carriage in accordance with the deviation. In this way, it is possible to cope with paper feeding that tends to shift the position in the width direction of the paper, such as paper feeding from a manual paper feeding device, without stopping image formation.

  In a preferred aspect of the present invention, the detection device detects the position of the sheet on the platen, and when the position of the sheet is outside a predetermined range on the platen, the sheet is pulled back to perform skew correction. The image forming apparatus.

  Further, as described above, when it is detected that the position in the width direction of the paper is shifted, the position of the paper is outside the predetermined range on the platen, and a range in which normal image formation can be performed by scanning the carriage. If the paper is misaligned beyond the limit, or the paper is fed diagonally and cannot be recognized as a normal width, pull the paper back from the platen, Correct the paper skew and then refeed. In this way, the sheet can be returned to a normal resting state.

  In a preferred aspect of the present invention, the detection device detects a position of a sheet on the platen, and reports a sheet shift when the position of the sheet is outside a predetermined range on the platen. An image forming apparatus.

  As described above, when the position of the paper on the platen is detected, the position of the paper is outside the predetermined range on the platen, and the paper is misaligned beyond the range where normal image formation is possible. Is fed obliquely and cannot be recognized as a normal size width, it is possible to report a paper misalignment. In particular, if this predetermined range exceeds the range that can be corrected by skew correction of the paper, or if the paper does not return to the normal position even after repeated skew correction, image formation is stopped and a notification to that effect is given. It is also possible to do.

  In a preferred aspect of the present invention, the suction device includes a suction fan, and the suction fan is controlled in suction power by PWM control.

  Usually, the suction device may be a suction fan that sucks air from the back side of the platen. The suction fan is preferably controlled in its suction force by PWM control. A large number of fine holes are uniformly formed on the platen, and when the paper is conveyed onto the platen, the paper is sucked by the suction force of the suction fan through the fine holes. At this time, the wider the paper width, the larger the suction area, and the smaller the micropore area that is not covered by the paper and through which air can flow, the greater the degree of decompression on the back side of the platen. On the other hand, by performing PWM control of the suction fan, suction can be performed with a suction force suitable for each sheet.

  According to the present invention, there is provided an image forming apparatus capable of detecting a paper width by a sensor mounted on a carriage without causing a paper feeding problem due to paper floating on the platen or excessive suction even for a paper of unknown width. Can be provided.

  Specific embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic view of an ink jet printer which is an image forming apparatus of the present invention. FIG. 2 is an external view of a carriage on which a paper placement unit (platen), a print head (head), and paper detection means are mounted in the image forming apparatus shown in FIG. However, the paper detection means is arranged on the lower side of the carriage (the side facing the platen) and does not appear in the figure.

  As shown in FIG. 1, the image forming apparatus of the present invention includes three roll paper feeding devices, and two flanges 1 are set on both sides of the paper tube of each roll paper 2. The roll paper 2 on which the flange 1 is set is set on a flange cradle 3. The roll paper 2 is pulled out by a paper feed roller 6 driven by a drive motor 7, and is transported to a paper tension applying device 11 through a paper transport path 10. A sensor for detecting whether or not the set flange 1 has been moved is mounted on the roll paper feeder.

  The sheet conveyed between the registration roller 13 and the pressure roller 14 further downstream in the sheet conveyance path 10 is conveyed onto a platen 24 on the chamber 18. A negative pressure is formed in the chamber by a suction fan 19 which is a suction device arranged at the lower part of the chamber 18, and a plurality of small holes are provided on the platen 24, so that the paper is sucked onto the flat platen 24. Thus, the flatness of the paper is maintained. The suction fan 19 is PWM-controlled to cope with various paper sizes, and the suction force of the suction fan 19 is changed by changing the duty value of the PWM signal.

  On the platen 24, a head 15 for ejecting ink and a detector 16 for detecting the width of the paper, for example, a carriage 16 equipped with a reflective optical sensor are arranged. Before printing starts, the carriage 16 scans the paper, and the optical sensor detects the paper width. The head 15 determines the ink discharge position (image forming position) based on the width of the paper detected by the sensor and forms an image. When forming an image on a sheet, the carriage 16 reciprocates in the width direction of the sheet along the main scanning stay 17, and the head 15 ejects ink toward the sheet on the platen 24 while synchronizing with the movement of the carriage 16. .

  Thereafter, each time the carriage 16 scans, an image for each scan is formed on the paper, and is sent out by a predetermined length from the registration roller 13 to form images one after another. When the image formation on the paper is completed, the paper is cut into a predetermined length by the cutter 20, conveyed along the reverse paper guide 21, and discharged to the paper discharge tray 22.

  It is usually necessary to detect the width of the sheet when the apparatus is turned on and when the sheet is replaced. When the apparatus is turned on and when the paper is replaced, the width of the paper is not known, so an operation for detecting the paper width is performed. In this embodiment, one end of the sheet in the width direction is always aligned at a predetermined position and conveyed onto the platen 24, so that only the width of the sheet needs to be detected.

  FIG. 3 shows a flowchart of the detection of the width of the sheet and the printing by the image forming apparatus in this embodiment. When the power of the image forming apparatus is turned on or when it is determined that the sheet has been replaced by a sensor mounted on the sheet feeding device 3 (YES in step S1), there is no size input by the user's manual input (in step S2). NO) moves the carriage 16 toward the end and retracts it outside the printing area, thereby preventing contact between the paper conveyed on the platen 24 and the carriage 16 (step S3).

  In order to ensure the conveyance of the sheet, the sheet is conveyed from the registration roller 13 onto the platen 24 without operating the suction fan 19 (step S4). After the sheet is conveyed to a position where the size of the sheet can be detected, the suction fan 19 is operated at the Duty value at the minimum size that can be handled by the printer (step S5). Since the platen 24 has innumerable suction holes, if the paper size is small, the area where the suction holes are blocked is small, and even if the suction fan 19 is operated with a duty value for sucking a large size paper, the paper is sufficient Therefore, the suction fan 19 is operated with the Duty value of the minimum size paper that can sufficiently fix all the compatible paper sizes on the platen 24.

  When the sheet is fixed on the platen 24, the carriage 16 is scanned and the edge of the sheet is read by the sensor (step S6). At this time, since the paper fed from the roll paper feeding device 3 is considered not to be greatly deviated from the reference transport position in the width direction, it is possible to detect the size by detecting the edge of only one side of the paper. The paper width can be determined by reducing the detection time.

  After the size detection is completed, the registration roller 13 is reversed and rewound to remove the paper from the platen 24 (step S7), and suction is started with a duty value corresponding to the detected size of the suction fan 19 (step S8). Note that, when the image forming apparatus is powered on, or when the paper is replaced by a sensor mounted on the paper feeding device 3 (NO in step S1), or when the size is determined by the user's manual input (step S2). YES) skips this step S8 and proceeds to the next scan.

  When the suction fan 19 starts sucking at a predetermined duty value, the carriage 16 is moved to the sheet conveyance area on the platen 24 (step S9), the registration roller 13 is rotated forward, and the sheet is conveyed onto the platen 24. . The leading edge of the conveyed paper is detected by a sensor mounted on the carriage 16 (step S10). Thereby, the relative position on the carriage 16, that is, the head 15 and the platen 24 becomes clear. The image forming apparatus forms an image on a sheet on the platen 42 based on the detected size and tip position.

(Embodiment 2)
The same image forming apparatus as that of the first embodiment includes a manual paper feeding device 5 that can manually feed paper when printing cut paper other than roll paper. When paper is fed from the manual paper feeder 5, the actual paper conveyance position may be shifted from the conveyance reference position of the apparatus due to a user insertion blur or the like. For this reason, unlike the paper fed from the roll paper feeder, when detecting the size by the sensor, it is necessary to check the paper width by detecting not only one side of the paper but also both ends.

  A flowchart when manual feed is selected is shown in FIG. First, it is determined whether the printing is normal roll paper printing or manual paper feeding (step S20). If the printing is not manual paper feeding (NO in step S20), the normal printing operation described in the first embodiment is performed. (Step S21). Here, printing by roll paper feeding is normal printing, but printing by paper supply from a cut paper tray for continuous printing can also be normal printing described in the first embodiment.

  The sheet fed from the manual sheet feeder 5 (YES in step S20) does not know the sheet size, and therefore the suction fan 19 is not operated with the carriage 16 retracted outside the printing area (step S22). Then, the sheet is conveyed onto the platen 24 (step S23).

  When the sheet has been transported onto the platen 24, the suction fan 19 is operated to suck the sheet onto the platen 24 with a duty value (largest duty value) corresponding to all the sheet sizes (step S24).

  When the sheet is fixed on the platen 24 by suction, the carriage 16 scans the platen 24, and both ends of the sheet are detected by the sensors mounted on the carriage 16 (step S25). Based on the detected paper size (width) and the position of the paper edge on the platen 24, the deviation amount between the actual (width direction) position of the paper and the reference paper position of the printer is calculated, and the deviation amount is within an allowable range. If yes (YES in step S26), printing is started according to the flow from step S27 to step S31 corresponding to step S7 to step S11 described in the first embodiment.

  If the deviation between the actual sheet position and the reference sheet position of the apparatus is large and not within the allowable range (NO in step S26), whether or not the deviation between the actual sheet position and the reference sheet position of the apparatus is within the second allowable range. Is determined (step S32). If the deviation is within the second allowable range (YES in step S32), it is determined that the paper insertion deviation from the manual sheet feeder 5 can be handled, and the following predetermined operation is performed (step S33). . The predetermined operation refers to, for example, scanning the platen 24 and ejecting ink from the head 15 so that the image is printed with the reference position of the image to be printed adjusted to the amount of deviation of the paper and shifted from the reference position on the platen 24. Control. By doing so, even if the paper is significantly displaced on the platen 24, printing can be performed without any problem by shifting the image forming position on the apparatus side without prompting the user to reinsert the paper.

  When the deviation between the actual paper position and the reference paper position of the apparatus is out of the second allowable range (NO in step S32), it is impossible to cope with the apparatus, and the printing scan is stopped and an alarm is issued. (Step S34).

(Embodiment 3)
As in the second embodiment, the image forming apparatus according to the third embodiment has a feature in detecting and controlling the size and arrangement of paper when paper is fed manually. As in the second embodiment, in manual paper feeding, there are cases where the actual paper position on the platen 24 and the reference paper position of the apparatus are shifted from each other due to a user insertion error or the like.

  In this case, if the deviation amount between the actual sheet position on the platen 24 and the reference sheet position of the apparatus is fed within a predetermined range (YES in step S46), steps S20 to S2 described in the second embodiment are performed. Printing is started according to the flow from step S40 to step S51, respectively, corresponding to the flow of S31.

  However, when it is determined in step 46 corresponding to step 26 of the second embodiment that the amount of deviation between the actual sheet position on the platen 24 and the reference sheet position of the apparatus is not within the predetermined range (NO in step S46). Then, the reverse and forward rotation of the registration roller 13 is repeated several times to perform an operation for correcting the oblique conveyance of the paper, and the paper is rearranged on the platen (step S52). Then, the carriage 16 is scanned, and the size and both ends of the sheet are detected again by the sensor (step S53). If the amount of deviation between the actual paper position and the reference paper position of the apparatus falls within the predetermined range (YES in step S53), the process returns to step 47, and as described above, the normal operation is performed according to the flow of image printing after step 47. Start the printing operation. However, if the deviation amount between the actual paper position and the reference paper position of the apparatus is not within the predetermined range (NO in step S53), the deviation amount between the paper position and the reference paper position of the apparatus has no correspondence on the apparatus. As a possible range, the printing scan is stopped and an alarm is issued to notify the user (step S55).

  The image forming apparatus of the present invention relates to, for example, a printer, a plotter, a FAX, a copying machine, etc., which employ an ink jet system. This is particularly effective in an image forming apparatus that supports a wide-width sheet having many types of paper sizes that can be supported.

Schematic of the image forming apparatus of the present invention External view of paper placement section (platen) and carriage Printing flow diagram according to Embodiment 1 Printing flow diagram according to the second embodiment Printing flow diagram according to Embodiment 3

Explanation of symbols

1: Flange 2: Roll paper 3: Roll paper feeder 5: Manual paper feeder 6: Paper feed roller (for roll paper)
7: Drive motor 8: Paper feed roller (for manual paper)
10: Paper transport path 11: Paper tension applying device 13: Registration roller 14: Pressure roller 15: Head 16: Carriage 17: Main scanning stay 18: Chamber 19: Suction fan 20: Cutter 21: Reversing paper guide 22: Paper discharge Tray 24: Platen

Claims (9)

A paper feeder that can feed paper of different widths;
A platen for placing paper fed from the paper feeding device at an image forming position;
A suction device for sucking and supporting paper on the platen;
A head that forms an image by ejecting ink onto a sheet placed on the platen;
A detection device for detecting the width of the paper on the platen;
An image forming apparatus including the head and the detection device, and a carriage that scans in the width direction of the paper,
Retracting the carriage outside the image forming area of the platen;
The suction force of the suction device is set to a first predetermined value or less, paper is fed onto the platen,
Supporting the paper with the suction force of the suction device as a second predetermined value;
An image forming apparatus that scans the carriage and detects the width of the sheet by the detecting device. The first predetermined value is a suction force at the time of image formation on the maximum width of paper that can be fed,
The image forming apparatus according to claim 1, wherein the second predetermined value is a suction force when an image is formed on a sheet having a minimum width that can be fed.   3. The image forming apparatus according to claim 1, wherein when the width of the fed paper is unknown, the image is formed after the width of the paper is detected by the detection device. After detecting the paper width by the detection device,
Pull the paper back from the platen,
The carriage is disposed at a position facing the width of the paper on the platen,
With the suction device as a suction force corresponding to the width of the paper, the paper is fed onto the platen,
The image forming apparatus according to claim 1, wherein a leading edge of the sheet is detected by the detection device. The paper feeding device includes a plurality of paper feeding units,
5. The detection device according to claim 1, wherein, for a sheet fed from a predetermined sheet feeding unit, the sheet width is calculated by detecting one end of the sheet. Image forming apparatus. The detection device detects the position of the paper on the platen,
The image forming apparatus according to claim 1, wherein an image forming position of the head is controlled according to a position of the sheet. The detection device detects the position of the paper on the platen,
The image forming apparatus according to claim 1, wherein when the position of the sheet is out of a predetermined range on the platen, the sheet is pulled back to perform skew correction. The detection device detects the position of the paper on the platen,
8. The image forming apparatus according to claim 1, wherein when the position of the sheet is out of a predetermined range on the platen, a sheet misalignment is notified. The suction device includes a suction fan,
The image forming apparatus according to claim 1, wherein the suction force of the suction fan is controlled by PWM control.