JP2017030900A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which reduces load fluctuation or friction acted on paper, and prevents the generation of an image failure or paper powders.SOLUTION: An image forming device 1 is equipped with a paper detection device 20 which detects that paper is carried to a carrying path 17 of the paper. The paper detection device 20 is equipped with an actuator 40 which is provided so as to rotate about a support shaft 41, and pressed by the paper fed to the carrying path 17 to rock in a direction retracting from the carrying path; and a first sensor portion 51 which detects the rocking in the retracting direction of the actuator 40. The actuator 40 has an arm portion 42 which extends from the support shaft 41 toward the carrying path 17, and is pressed by the paper; and a detected piece 43 which is provided on the support shaft 41 on the retracting direction side than the arm portion 42, and detected by the first sensor portion 51. At a tip end of the arm portion 42, a roller portion 45 which rotates to follow the paper while always projecting out to the carrying path 17 and contacting with the paper, is provided.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet conveyed along a conveyance path.

  In an image forming apparatus such as a printer or a color printer, an image is formed on a sheet transported along a transport path by an image forming unit. In recent years, the types of paper have been diversified, and it has become an important issue to stably transport various types of paper along the transport path. For example, when a strong paper such as thick paper is transported, a load fluctuation during transport and a trailing edge jump of the paper are large, and an image defect such as a horizontal stripe or a lateral magnification defect may occur.

  For the purpose of stably transporting the paper, Patent Document 1 discloses that the traveling trajectory of the paper is stabilized by momentarily interrupting the rotation of the pair of transport rollers that transport the paper and tensioning the paper along the guide member. An image forming apparatus is described.

JP-A-6-48604

  However, in the image forming apparatus described in Patent Document 1, the sheet is stably conveyed while the sheet is in tension, but sudden load fluctuation occurs at the moment when the trailing edge of the sheet is separated from the pair of conveying rollers. Therefore, there is a problem that a toner image shifts or a magnification failure occurs. In addition, there is a problem that paper dust is easily generated due to the rubbing of the paper with the guide member. On the other hand, in order to avoid such a problem, the sheet may be bent. However, if the sheet is bent too much, sudden load fluctuations and speed fluctuations may occur when passing the pair of conveyance rollers, and horizontal stripes may occur. In this way, it is necessary to adjust the balance of tension applied to the paper.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus in which fluctuations in load and friction acting on a sheet are reduced to prevent image defects and paper dust.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a pair of guide members that are arranged to face each other and that form a conveyance path for a sheet from a first conveyance roller to a second conveyance roller, and the conveyance path. A sheet detecting device that detects that the sheet has been conveyed to the sheet, and the sheet detecting apparatus is provided so as to be rotatable about a support shaft and is sent from the first conveying roller to the conveying path. An actuator that swings in a direction of retreating from the transport path when pressed by a sheet; and a first sensor unit that detects the swing of the actuator in the retraction direction. An arm portion that extends from the shaft toward the transport path and is pressed by the paper, and is provided on the support shaft at a position closer to the retracting direction than the arm portion. And a roller portion that is driven to rotate while being in contact with the paper and always protruding in the transport path at the tip of the arm portion. .

  By adopting such a configuration, since the roller portion always protrudes in the transport path, the sheet fed from the first transport roller can be guided mainly by the roller portion. Therefore, the frictional force acting on the paper during conveyance and the load fluctuation can be reduced and the paper can be stably conveyed, so that it is possible to suppress image defects such as generation of paper dust and transfer deviation.

  In the image forming apparatus according to the aspect of the invention, the paper detection device may further include a second sensor unit that detects that the actuator has swung in the retract direction further than a paper detection position detected by the first sensor unit; A control unit that determines a bending state of the sheet in the transport path based on detection signals of the first sensor unit and the second sensor unit, and the control unit swings the actuator in the retraction direction. Any of a first position that is not detected, a second position that is swung until it is detected by the first sensor unit, and a third position that is swung until it is detected by the second sensor unit It may be characterized in that the bending state of the paper is determined based on whether or not the position is swung.

  By adopting such a configuration, when the roller portion is pressed by the tensioned paper, the actuator swings in the retracting direction, so that the paper is transported to the transport path by one actuator, and the paper Can be detected as a tension state, and the configuration of the transport path and the control of the transport timing of the paper are facilitated.

  In the image forming apparatus according to the aspect of the invention, the control unit determines that the sheet conveyed through the conveyance path is in a tension state without bending based on the actuator swinging to the third position. It is good also as controlling at least one of the paper conveyance speed in the 1st conveyance roller and the paper conveyance speed in the 2nd conveyance roller, and adjusting flexure of the paper appropriately.

  By adopting such a configuration, it is possible to promptly feed back so that an appropriate deflection is formed.

  In the image forming apparatus according to the aspect of the invention, the actuator is swung to the third position when the sheet held and pulled between the first conveyance roller and the second conveyance roller contacts the arm portion. This may be a feature.

  By adopting such a configuration, it is possible to reliably detect that the paper is in a tensioned state.

  In the image forming apparatus according to the aspect of the invention, the sheet detection device may further include a stopper that restricts the actuator from rotating in the retracting direction from the third position.

  By adopting such a configuration, even when the paper is in a tensioned state, the roller portion always protrudes in the transport path, and the tensioned paper can be guided by the roller portion, so that the load on the paper can be reduced.

  In the image forming apparatus according to the aspect of the invention, the actuator may be biased in a direction opposite to the retracting direction so that the arm portion protrudes into the transport path.

  By adopting such a configuration, it is possible to always project the arm portion in the transport path.

  According to the present invention, since the paper fed from the pair of transport rollers is mainly guided by the roller unit, the frictional force and load fluctuation acting on the paper during transport can be reduced, so that the paper can be transported stably and the generation of paper dust. And image defects such as transfer deviation can be suppressed.

FIG. 2 is a cross-sectional view schematically illustrating the internal structure of the printer according to the embodiment of the invention. In the printer according to an embodiment of the present invention, FIG. In the printer according to an embodiment of the present invention, FIG. In the printer according to the embodiment of the present invention, it is a diagram showing a paper detection device at the time of paper tension. It is a perspective view showing an actuator of a paper detection device of a printer concerning one embodiment of the present invention.

  Hereinafter, an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

  First, an overall configuration of a printer 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram showing an outline of a printer according to an embodiment of the present invention. In the following description, the front side of the page in FIG. 1 is the front side (front side) of the printer 1, and the left and right directions are the printer. The direction when 1 is viewed from the front is used as a reference.

  The printer 1 includes a substantially rectangular parallelepiped housing 2 having a hollow portion. A paper feed cassette 3 that stores paper is detachably mounted below the inside of the housing 2. A paper feed unit 4 that feeds paper from the paper feed cassette 3 is provided on the upper right side of the paper feed cassette 3.

  An image forming unit 5 is provided above the paper feed cassette 3. A photosensitive drum 6 is rotatably provided in the image forming unit 5, and a charging device 7, a developing device 8, a transfer roller 9, and a cleaning device 10 are disposed around the photosensitive drum 6. It arrange | positions along the rotation direction (refer arrow X of FIG. 1) of the drum 6. FIG. The developing device 8 is connected to the toner container 11. Further, an exposure unit 12 composed of a laser scanning unit (LSU) is provided on the left side of the image forming unit 5.

  A fixing device 13 is provided above the image forming unit 5, and a paper discharge unit 14 is provided at the upper left of the fixing device 13. The paper discharge unit 14 faces a paper discharge tray 15 formed on the upper surface of the housing 2.

  In addition, a conveyance path 17 is provided inside the housing 2 through the transfer nip 16 formed between the photosensitive drum 6 and the transfer roller 9 and the fixing device 13 toward the paper discharge unit 14. A registration roller pair 18 is disposed on the transport path 17 upstream of the transfer nip 16. Between the registration roller pair 18 and the transfer nip 16, a paper detection device 20 that detects that the paper has been transported to the transport path 17 is provided. The paper detection device 20 will be described later. Further, the conveyance path 17 is branched to a reverse path 19 on the downstream side of the fixing device 13. The reverse path 19 joins the transport path 17 on the upstream side of the registration roller pair 18.

  Next, an image forming operation of the printer 1 having such a configuration will be described. After the surface of the photosensitive drum 6 is charged by the charging device 7, exposure corresponding to image data is performed on the photosensitive drum 6 by laser light (see arrow P) from the exposure device 12, and the photosensitive drum 6 is exposed. An electrostatic latent image is formed on the surface. The electrostatic latent image is developed into a toner image by the developing device 8. The toner remaining on the photosensitive drum 6 is removed by the cleaning device 10.

  On the other hand, the paper fed from the paper feed cassette 3 by the paper feed unit 4 is sent out to the transport path 17, and the second pair of registration rollers 18 serving as the first transport rollers is synchronized with the above-described image forming operation and the second timing. It is conveyed to the transfer nip 16 between the photosensitive drum 6 as a conveyance roller and the transfer roller 9. In the transfer nip 16, the toner image on the photosensitive drum 6 is transferred to a sheet. The sheet on which the toner image has been transferred is conveyed downstream in the conveyance path 17 and enters the fixing device 13, where the toner image is fixed on the sheet. The paper on which the toner image is fixed is discharged from the paper discharge unit 14 to the paper discharge tray 15.

  Next, the paper detection device 20 will be described with reference to FIGS. 2 is a diagram showing the paper detection device during standby, FIG. 3 is a diagram showing the paper detection device during paper conveyance, FIG. 4 is a diagram showing the paper detection device during paper tension, and FIG. 5 is a perspective view of the actuator. .

  As shown in FIG. 2, the sheet conveyance path 17 from the registration roller pair 18 toward the transfer nip 16 is inclined obliquely in the upper left direction from the exit of the registration roller pair 18, and thereafter, obliquely upper right toward the transfer nip 16. The inner guide member 31 and the outer guide member 32 are bent so as to be inclined in the direction and are arranged to face each other.

  The outer guide member 32 has a notch 34 formed in the vicinity of the bent portion, and the inner guide member 31 has a recess 35 recessed from the conveying path 17 at a position facing the notch 34. Yes. The cutout hole 34 and the recess 35 are respectively formed in the center portion of the outer guide member 32 and the inner guide member 31 in the width direction orthogonal to the paper transport direction. The inner guide member 31 and the outer guide member 32 are formed of a material having a low friction coefficient and good slipperiness.

  The paper detection device 20 includes an actuator 40 provided outside the notch 34 of the outer guide member 32, and a paper detection sensor 51 and a second sensor unit provided above the actuator 40 as a first sensor unit. The bending detection sensor 52 is provided.

  As shown in FIG. 5, the actuator 40 includes a support shaft 41 that is rotatably supported by a fixed shaft 37 (see FIGS. 2 to 4) that extends in the width direction, and a circumferential direction of the support shaft 41. An arm portion 42 and a detected piece (light-shielding piece) 43 provided on the support shaft 41 are provided at a distant position. The arm portion 42 extends in a direction perpendicular to the support shaft 41, and a roller portion 45 that rotates about an axis parallel to the support shaft 41 is supported at the tip. The width | variety of the roller part 45 is 50 mm as an example. The detected piece 43 is formed in a fan shape with the support shaft 41 as the center.

  The actuator 40 is swingable about the support shaft 41 in such a posture that the arm portion 42 is on the inner side (conveyance path 17 side) and the detected piece 43 is on the outer side. When the actuator 40 swings most counterclockwise about the support shaft 41, the arm portion 42 protrudes almost horizontally into the transport path 17 through the cutout hole 34, and the tip portion of the roller portion 45 is in the inner guide. It is accommodated in a recess 35 formed in the member 31. On the other hand, when the actuator 40 swings around the support shaft 41 in the direction of retreating from the transport path 17 (clockwise direction in FIG. 2), the roller unit 45 is separated from the recess 35 as shown in FIG. A gap is formed between the roller portion 45 and the inner guide member 31.

  The actuator 40 is urged in a protruding direction (counterclockwise direction in FIG. 2) opposite to the retracting direction by an urging member (not shown) such as a torsion coil spring, so that the arm portion 42 is substantially horizontal in the transport path 17. The tip of the roller portion 45 is maintained at the standby position accommodated in the recess 35. When the sheet is conveyed from the registration roller pair 18 at this standby position, the leading end of the sheet comes into contact with the roller unit 45 or the arm unit 42 and pushes up the arm unit 42 against the urging force of the urging member. Swings around the support shaft 41 in the retracting direction.

  A stopper 38 is provided on the downstream side in the retracting direction of the detected piece 43. When the actuator 40 swings in the retracting direction, the side surface of the detected piece 43 on the downstream side in the retracting direction comes into contact with the stopper 38 and the swinging in the retracting direction is restricted. In a state where the swinging of the actuator 40 in the retreat direction is restricted, the roller unit 45 is retreated to a position close to the notch hole 34 of the outer guide member 32 in the transport path 17. Then, a straight line L1 that connects the contact surface between the sheet conveyed on the conveyance path 17 and the roller unit 45 and the nip of the conveyance roller pair 18, and a straight line L2 that connects the contact surface between the sheet and roller unit 45 and the transfer nip 16. However, it does not interfere with the inner and outer guide members 31, 32. With this configuration, when a sheet is stretched between the registration roller pair 18 and the transfer nip 16, the sheet presses the roller portion 45, but does not contact the inner guide member 31 and the outer guide member 32. do not do.

  The paper detection sensor 51 and the deflection detection sensor 52 are provided along the rotation locus of the detected piece 43. The paper detection sensor 51 is disposed on the upstream side in the retreat direction, and the bending detection sensor 52 is disposed on the downstream side with a predetermined gap from the paper detection sensor 51. As the paper detection sensor 51 and the deflection detection sensor 52, for example, a photo interrupter having a light emitting part and a light receiving part can be used. The sheet detection sensor 51 and the deflection detection sensor 52 are electrically connected to the control unit 53.

  When the actuator 40 swings in the retracting direction until the detected piece 43 is detected by the paper detection sensor 51, the roller portion 45 moves away from the concave portion 35 of the inner guide member 31 and advances into the conveyance path 17.

  When the actuator 40 further swings in the retracting direction until the detected piece 43 is detected by the deflection detection sensor 52, the side surface of the detected piece 43 on the downstream side in the retracting direction comes into contact with the stopper 38, and the actuator 40 swings in the retracting direction. The movement is restricted, and the roller unit 45 is retracted in the transport path 17 to a position close to the notch 34 of the outer guide member 32. That is, when the actuator 40 swings in the retracting direction and the detected piece 43 is detected by the bending detection sensor 52, the sheet is stretched between the registration roller pair 18 and the transfer nip 16 as described above. Will be.

  The operation of the sheet detection apparatus 20 having the above configuration will be described with reference to FIGS. As shown in FIG. 2, at the standby position, which is the first position of the actuator 40, the paper detection sensor 51 and the deflection detection sensor 52 are in an off state. When the leading end of the fed paper P comes into contact with the roller portion 45 or the arm portion 42, the arm portion 42 is pressed by the leading end of the paper P, and the actuator 40 moves in the retracting direction against the biasing force of the biasing member. Start swinging.

  Eventually, as shown in FIG. 3, when the actuator 40 swings to the second position where the detected piece 43 is detected by the paper detection sensor 51, the paper detection sensor 51 is turned on. When the control unit 53 detects that the paper detection sensor 51 is on and the deflection detection sensor 52 is off, the control unit 53 determines that the paper P has been conveyed to the conveyance path 17 and transfers the toner image at the transfer nip 16. Adjust timing. Since the actuator 40 is biased in the direction opposite to the retracting direction by the biasing member, the paper P is guided by the roller portion 45 while being pressed in the direction of the inner guide member 31, and along the inner guide member 31, the transfer nip. 16 is conveyed.

  Depending on the type of paper to be conveyed, the paper may be pulled between the registration roller pair 18 and the transfer nip 16. In this case, the roller unit 45 is pressed outward in the transport path 17 by the pulled paper, and the actuator 40 further swings in the retracting direction. Eventually, as shown in FIG. 4, the side surface of the detected piece 43 on the downstream side in the retracting direction comes into contact with the locking protrusion 38 and swings to the third position where the swinging of the actuator 40 in the retracting direction is restricted. Then, the roller unit 45 is fixed at a position for guiding the paper in the transport path 17. At the same time, the detected piece 43 is detected by the bending detection sensor 52.

  The state in which the sheet is pulled is a state in which the sheet is tensioned without being bent through the roller unit 45 between the nip of the registration roller 18 and the transfer nip 16, and the contact surface between the roller unit 45 and the sheet In this state, the sheet is conveyed along a straight line L1 that connects the nip of the registration roller pair 18 and a straight line L2 that connects the contact surface between the sheet and the roller unit 45 and the transfer nip 16. Since the straight lines L1 and L2 do not interfere with the inner and outer guide members 31 and 32 as described above in a state where the swinging of the actuator 40 in the retracting direction is restricted, the sheet is guided to the inner and outer guide members 31 and 32. It is guided by the roller part 45 so that it does not contact.

  Further, when the detected piece 43 is detected by the bending detection sensor 52, the bending detection sensor 52 is switched to the ON state. When the control unit 53 detects that the paper detection sensor 51 is in the on state and the deflection detection sensor 52 is in the on state, the control unit 53 determines that the paper P is in a tension state, and determines the paper conveyance speed in the registration roller pair 18. By adjusting at least one of the sheet conveyance speeds in the transfer nip 16, the deflection of the sheet P is optimized. Specifically, the rotational speed of the registration roller pair 18 is increased, the rotational speed of the transfer roller 9 and the photosensitive drum 6 is decreased, or the rotational speed of the registration roller pair 18 is increased and the transfer roller 9 and The rotational speed of the photosensitive drum 6 is decreased.

  As described above, when at least one of the sheet conveying speed at the registration roller pair 18 and the sheet conveying speed at the transfer nip 16 is adjusted, when the sheet P is moderately bent, the actuator 40 is moved by the urging force of the urging member. The sheet P swings in the direction opposite to the retreat direction, and is guided by the roller unit 45 while being pressed in the direction of the inner guide member 31, and is conveyed to the transfer nip 16. In addition, the detected piece 43 is separated from the bending detection sensor 52, and the bending detection sensor 52 is switched to the off state. When the control unit 53 detects that the paper detection sensor 51 is in the on state and the flexure detection sensor 52 is in the off state, the control unit 53 determines that the paper is released from the tension state and is in a bent state, and the registration roller The sheet conveying speed at the pair 18 and the sheet conveying speed at the transfer nip 16 are returned to the reference speed.

  As described above, in the image forming apparatus 1 of the present invention, even if the actuator 40 swings in the direction of retreating from the conveyance path 17, the roller portion 45 always protrudes into the conveyance path 17. The sheet fed from 18 is guided in the transport path 17 mainly by the roller unit 45. Generally, the frictional force between the paper and the guide member is larger than the frictional force between the paper and the roller part, and the load fluctuation when the paper is detached from the guide member is the load when the paper is separated from the roller part. Greater than fluctuations. Therefore, by mainly guiding the paper by the roller unit 45, the generation of paper dust can be suppressed. In particular, when a tension state of a sheet is detected, an appropriate bending is formed on the sheet, so that the sheet can be stably conveyed.

  In addition, since the actuator 40 having a simple configuration can be used to detect both the conveyance of the sheet to the conveyance path 17 and the tension of the sheet, the conveyance timing of the sheet can be detected by a simple mechanism. And transport posture can be controlled easily.

  Further, when the conveyance path 17 is bent or curved toward the transfer nip 16 as in the present embodiment, when the sheet is pressed toward the inner guide member 31 by the roller unit 45, the sheet is moved to the inner guide member 31. 31, and enters the transfer nip 16 from a direction close to the tangential direction of the photosensitive drum 6. Therefore, when the paper enters the transfer nip 16, it is difficult for the paper to be impacted from the photosensitive drum 6, and the occurrence of horizontal stripes can be prevented.

  Particularly in the present embodiment, when the actuator 40 swings in the retracting direction, the roller portion 45 is close to the bent portion of the transport path 17. In the bent conveyance path 17, the paper is most likely to contact the inner outer guide member 32 in the bent portion. However, in this embodiment, the roller portion 45 has advanced near the bent portion, so that the paper is most tensed. However, the paper can be guided by the roller unit 45 so as not to contact the outer guide member 32.

  In the present embodiment, the position where the swinging of the actuator 40 in the retracting direction is restricted is the same as the position where the bending detection sensor 52 detects the bending, but the swinging restriction position and the bending detection position are the same. May be different.

  Further, in order to maintain the pressure balance in the paper width direction, the registration roller pair 18 has a roller main body divided into two at the center in the width direction, and the support shaft is urged by an urging member at both ends and the center. May be configured to be supported. In such a case, the paper may wave and wrinkle at the center in the width direction where the roller body is not provided. In this embodiment, since the actuator 40 is arranged at the center in the paper width direction, even when the paper is undulated, the undulation can be extended by the roller unit 45, so that generation of wrinkles can be prevented. it can.

  A plurality of actuators 40 may be provided according to the configuration of the registration roller pair. For example, when the registration roller pair has a roller main body portion that is divided into two or more or a comb-tooth-shaped roller main body portion, the actuator 40 is provided between each roller main body portion where the paper corrugation is likely to occur. Can be installed.

  Further, the paper detection sensor 51 can be used for both paper detection and bending detection. For example, the detected piece 43 of the actuator 40 is divided into an upstream detected portion and a downstream detected portion along the retraction direction with a predetermined interval. Then, the paper detection sensor 51 detects the downstream detection portion to detect that the paper has been conveyed to the conveyance path, and the paper detection sensor 51 detects the upstream detection portion, so that the paper is in a tension state. Detect something.

  Alternatively, as a method of detecting the swing of the actuator 40 in the retracting direction, an angle sensor that measures the rotation angle of the shaft support 41 is used, or an urging member that biases the actuator 40 in the direction opposite to the retracting direction is an actuator. For example, a pressure sensor that measures the pressure received from 40 can be used.

  However, as in the present embodiment, it is an error to arrange the paper detection sensor 51 and the deflection detection sensor 52 on the upstream side and the downstream side along the retraction direction and perform the paper detection and the deflection detection respectively. This is preferable because of less detection.

  Note that the above description of the embodiment of the present invention describes a preferred embodiment of the image forming apparatus according to the present invention, and thus may have various technically preferable limitations. The technical scope of the present invention is not limited to this embodiment unless specifically described to limit the present invention. Furthermore, the constituent elements in the embodiments of the present invention described above can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. The description of the embodiment of the present invention is not intended to limit the content of the invention described in the claims.

1 Printer (image forming device)
6 Photosensitive drum (second transport roller)
9 Transfer roller (second transport roller)
17 Transport path 18 Registration roller pair (first transport roller)
20 Paper detection device 31 Inside guide member (guide member)
32 Outer guide member (guide member)
38 Stopper 40 Actuator 41 Support shaft 42 Arm part 43 Detected piece 45 Roller part 51 Paper detection sensor (first sensor part)
52 Deflection detection sensor (second sensor part)
53 Control unit

Claims (6)

A pair of guide members disposed opposite to each other to form a conveyance path for the sheet from the first conveyance roller to the second conveyance roller;
A paper detection device that detects that the paper has been transported to the transport path;
With
The paper detection device includes:
An actuator that is pivotable about a support shaft and swings in a direction of retreating from the transport path by being pressed by a sheet fed from the first transport roller to the transport path;
A first sensor unit that detects swinging of the actuator in the retracting direction,
The actuator is
An arm portion extending from the support shaft toward the transport path and pressed by a sheet;
A detected piece provided on the support shaft on the side of the retracting direction than the arm portion and detected by the first sensor portion;
2. An image forming apparatus according to claim 1, wherein a roller portion is provided at a front end of the arm portion so as to protrude from the conveyance path and rotate while being in contact with a sheet. The paper detection device includes:
A second sensor unit for detecting that the actuator has swung in the retreat direction further than a paper detection position detected by the first sensor unit;
A control unit that determines a bending state of the sheet in the transport path based on detection signals of the first sensor unit and the second sensor unit;
The controller is
A first position where the actuator does not swing in the retraction direction, a second position where the actuator swings until it is detected by the first sensor unit, and a swing until it is detected by the second sensor unit The image forming apparatus according to claim 1, wherein the bending state of the sheet is determined based on which of the third position and the third position is swung.   Based on the fact that the actuator swings to the third position, the control unit determines that the sheet conveyed through the conveyance path is in a tension state without bending, and conveys the sheet on the first conveyance roller. 3. The image forming apparatus according to claim 2, wherein at least one of a speed and a sheet conveyance speed of the second conveyance roller is controlled to appropriately adjust the deflection of the sheet.   3. The actuator swings to the third position when a sheet held and pulled between the first transport roller and the second transport roller comes into contact with the arm portion. Or the image forming apparatus according to 3. The paper detection device includes:
The image forming apparatus according to claim 2, further comprising a stopper that restricts the actuator from swinging in the retracting direction from the third position. The actuator is
The image forming apparatus according to claim 1, wherein the arm portion is biased in a direction opposite to the retracting direction so as to protrude into the transport path.

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