JP2006039220A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of surely detecting a jammed sheet, regardless of the kind or the state of the sheet. <P>SOLUTION: A rotatable detecting member 28, constituting a jamming detecting means S3, is arranged facing a carrying guide member 24 constituting a sheet carrying path C for letting the sheet through; and by detecting the presence or absence of the jammed sheet by the detecting member 28, while rotating the detecting member 28 toward the carrying guide member at a prescribed timing, then, the jammed sheet is surely detected, irrespective of the kind or the state of the sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to jam detection.

  The conventional image forming apparatus includes a jam detection unit that detects a jam of a sheet. When the jam detection unit detects the jam of the sheet, the driving is stopped and the occurrence of the jam is notified to the user at the same time. There is what I did.

  FIG. 7 is a diagram showing the configuration of such a conventional image forming apparatus. In FIG. 7, reference numeral 15 denotes a registration roller for correcting the skew of the sheet 14 conveyed by the paper feed roller 13. A registration sensor S <b> 1 that detects the leading edge of the sheet is provided on the upstream side of the registration roller 15. Reference numeral 17 denotes a fixing device for fixing the toner image transferred onto the sheet. A fixing paper discharge sensor S2 for detecting the sheet discharged from the fixing device 17 is provided on the downstream side of the fixing device 17. .

  Here, as shown in FIG. 8A, the registration sensor S1 has a sensor flag 19 and a photo interrupter 20 that can swing around a support shaft 19a. When it is not transported, it takes a substantially vertical posture due to its own weight, and its upper end protrudes from the transport path C. In this state, the optical path of the photo interrupter 20 is open.

  On the other hand, when the sheet 14 is conveyed, the upper end is pressed by the sheet 14 as shown in FIG. 8B, the sensor flag 19 swings around the support shaft 19a, and the optical path of the photo interrupter 20 is changed. Cut off. When the optical path is interrupted in this way, the light-receiving unit of the photo interrupter 20 sends an open / shield signal to a main body control CPU (not shown), so that the main body control CPU confirms that the sheet 14 has been conveyed. It is configured so that it can be detected. The configuration and operation of the fixing paper discharge sensor S2 are the same as those of the registration sensor S1.

  By the way, the main body control CPU controls image writing, rotation of motors, start / stop of high voltage, and the like based on the sheet conveyance timing information detected by the sensors S1 and S2. A jam is detected based on signals from the sensors S1 and S2.

  For example, if a sheet detection signal is not input from the fixing paper discharge sensor S2 even after a predetermined time has elapsed after the registration sensor S1 detects the sheet 14, it is determined that a jam has occurred, and the main body control CPU Stop driving and notify the user of the occurrence of jam.

  Then, the user who has received the report opens the main body opening / closing cover (not shown) to remove the sheet 14 remaining in the apparatus in order to handle the jam, and closes the main body opening / closing cover again. Thereafter, the main body control CPU resets the jammed state and performs a return operation including forced paper discharge.

  However, when the occurrence of a jam is detected using the sensors S1 and S2 as described above, for example, when two sheets are jammed, only one sheet is removed, and the user does not notice other sheets. The main body opening / closing cover may be closed. After that, when the power switch is turned on, the return operation is started.

  Here, for example, as shown in FIG. 9, the remaining sheet 14 is wound around the heat fixing member (roller or film) 17A of the fixing device 17 between the registration sensor S1 and the fixing paper discharge sensor S2. In such a case, the main body control CPU cannot detect the remaining sheet via the sensors S1 and S2, so that the return operation is performed. As a result, the conveyance of the sheet 14 wound around the heat fixing member 17A is resumed, and the winding around the heat fixing member 17A is further promoted. This not only makes it difficult for the user to jam, but also has a risk of damaging the fixing device 17.

  Further, when the sheet is jammed in the state of undulation on the paper discharge side of the fixing device 17 during continuous printing, the user closes the opening / closing cover without noticing the presence of the sheet conveyed next to the jammed sheet. Even in such a case, the wrapping of the residual sheet as described above around the heat fixing member may be promoted.

  Therefore, in order to solve the problem that if the jam sheet remains between the two sensors S1 and S2, the main body control CPU cannot detect the presence of the jam sheet, as shown in FIG. It has been proposed to provide a sensor S3 between the two parts (see Patent Document 1).

JP 07-112843 A

  Here, in the sensor S3, as in the other sensors S1 and S2, as shown in FIG. 10, the sensor flag 19A protrudes upward from the conveyance guide surface (sheet conveyance path), and the upper end of the sensor flag 19A is It is configured to detect passage of the sheet 14 by being pushed down by the sheet 14.

  However, in the case of the sensor S3 having such a configuration, when the sheet 14 is thin, or when the sheet 14 is left in a high humidity environment for a long time and the stiffness is lost due to moisture absorption, the sheet 14 pushes down the sensor flag 19A. In other words, the sensor flag 19A is pushed and lifted from the conveyance guide surface. Therefore, the conventional image forming apparatus has a problem in that the jam of the sheet 14 cannot be accurately detected even when such a sensor S3 is provided.

  Further, as a conventional image forming apparatus, for example, there is an apparatus in which a sheet 14 is conveyed in a substantially vertical direction as shown in FIG. In this case, since the distance from the paper feed cassette 12 to the paper discharge tray 18 can be shortened, there is an advantage that the time required for printout is shortened and the apparatus can be downsized. Is conveyed in a substantially vertical direction, and it is difficult to detect this sheet when a jam occurs from the transfer portion to the fixing portion.

  That is, when the image forming apparatus is in operation, the sheet 14 is stably conveyed along the conveyance guide surface indicated by the symbol C ′ by the electrostatic absorption force acting on the conveyance guide sheet metal 16c due to the charge received by the transfer unit. However, when a jam occurs in the fixing unit and the time has elapsed, the sheet 14 that has not reached the fixing nip moves away from the conveyance guide sheet metal 16c and is suspended in the machine. Therefore, even when the sensor S3 is provided, the detection is performed. It was difficult to do.

  Therefore, the present invention has been made in view of such a situation, and an object thereof is to provide an image forming apparatus capable of reliably detecting a jam sheet regardless of the type or state of the sheet. Is.

  The present invention provides an image forming apparatus including a jam detection unit that detects a jam of a sheet, and a conveyance guide member that forms a sheet conveyance path through which the sheet passes, and a sheet conveyance surface of the conveyance guide member that is provided opposite to the sheet conveyance surface. And a rotatable detection member constituting the jam detection means, and the presence or absence of a jam sheet is detected by rotating the detection member toward the conveyance guide member at a predetermined timing. Is.

  As described above, the rotation detection member constituting the jam detection means is provided opposite to the conveyance guide member constituting the sheet conveyance path, and this detection member is rotated toward the conveyance guide member at a predetermined timing. By detecting the presence / absence of a jam sheet, the jam sheet can be reliably detected regardless of the type or state of the sheet.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a laser beam printer which is an example of an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, the same reference numerals as those in FIG. 7 denote the same or corresponding parts.

  In FIG. 1, 1A is a laser beam printer main body (hereinafter referred to as a printer main body), 1 is a scanner unit having optical means and scanning means for irradiating and scanning laser light transmitted according to image information, and 10 is a process. The process cartridge 10 is a main image forming means, and is a photosensitive drum 3 as an image carrier, a roller charger 4 made of semiconductive rubber, and a developing device 5 for developing toner 6 on the photosensitive drum 3. , And a cleaner 8 that removes waste toner from the photosensitive drum 3.

  Here, the photosensitive drum 3 in the process cartridge 10 rotates in the direction of the arrow. After the surface of the photosensitive drum 3 is uniformly charged by the roller charger 4, the laser light transmitted from the scanner unit 1 is emitted. By irradiating through the mirror 2, an electrostatic latent image is formed on the surface. The electrostatic latent image is developed with toner supplied from the developing device 5 and visualized as a toner image.

  On the other hand, the sheets 14 in the sheet feeding cassette 12 are separated and fed one by one by a sheet feeding roller 13 and a separation pad (not shown) provided facing the sheet feeding roller 13, and the fed sheet 14 is conveyed to a pair of registration rollers 15 along the upper and lower guides 13a.

  Here, the registration roller 15 is stopped until the sheet 14 arrives, and the skew of the sheet 14 is corrected by the leading edge of the sheet 14 abutting against the registration roller 15 in this state. After correcting the skew of the sheet 14 in this way, the registration roller 15 starts to rotate in synchronization with the leading edge of the image formed on the photosensitive drum 3, and the sheet 14 is transferred to the transfer roller 7 and the photosensitive drum 3. Are transferred to a transfer section.

  Next, the sheet 14 thus transported to the transfer unit is given a charge opposite in polarity to the toner from the transfer roller 7 from the back side of the sheet 14, thereby transferring the toner image formed on the photosensitive drum 3. Is done. Then, the sheet 14 to which the toner image is transferred in this way is conveyed to the fixing device 17 by the conveying roller 16a and the conveying guide 16b, and the toner image on the sheet 14 is heated and pressed by the fixing device 17. The toner image is dissolved and fixed on the sheet 14 to form a permanent image. After that, the sheet 14 is discharged to the discharge tray 18 through each conveyance roller.

  FIG. 2 is an enlarged view of the vicinity of the sheet entrance of the fixing device 17. The sheet carrying the unfixed toner image in the transfer unit is fed to the conveyance guide 16 while being charged by a transfer bias having a polarity opposite to that of the toner. It is done. Here, the conveyance guide 16 includes a grounded metal sheet 16b and a resin conveyance guide 16c formed in a rib shape, and the charged sheet 14 is electrostatically attracted to the metal sheet 16b. Since it is conveyed while receiving the action of force, it is conveyed along the surface of the conveyance guide 16 to the fixing device 17. In FIG. 1, C indicates a sheet conveyance path through which the sheet 14 is conveyed.

  Here, as shown in FIG. 2, the fixing device 17 rotates and drives the fixing roller 21 while being in pressure contact with the fixing roller 21, which is a heat fixing unit provided with a halogen heater 23 as a heating source. And a pressure roller 22 which is a pressure means that is driven and rotated.

  The fixing roller 21 is coated with a fluororesin as a surface release layer on a metal pipe such as aluminum or iron, and the inner surface is painted black so that heat from the halogen heater 23 can be efficiently absorbed. Yes. On the other hand, the pressure roller 22 is an elastic roller in which an elastic layer made of a sponge or solid silicone rubber and a surface release layer are coated on a metal core, and is pressed against the fixing roller 21 with a predetermined pressure. Touch.

  The sheet 14 carrying the unfixed toner image is guided to the nip formed by the contact between the fixing roller 21 and the pressure roller 22, and is heated and pressed to form a permanent image on the sheet. The Reference numeral 24 denotes a fixing entrance guide which is a conveyance guide member constituting a part of the sheet conveyance path C through which the sheet 14 passes. The fixing entrance guide 24 accurately moves the sheet 14 from the conveyance guide 16 to the fixing nip portion. So that you can lead to. The fixing entrance guide 24 is formed of a resin such as PBT or PET.

  On the other hand, the sheet 14 on which the toner image has been fixed at the fixing nip is separated from the fixing roller 21 by the separation claw 25 and conveyed outside the fixing device by the fixing paper discharge roller 30. Reference numeral 26 denotes a spring for bringing the separation claw 25 into contact with the surface of the fixing roller with a predetermined pressure, 27 denotes a fixing frame sheet metal that holds the fixing roller 21 and the pressure roller 22 via a heat insulating member and a bearing, and a resin sheath. It is a fixing frame.

  A fixing paper discharge sensor S2 is provided downstream of the fixing device 17, and a signal from the fixing paper discharge sensor S2 is input to a main body control CPU 50 provided at a predetermined position of the printer main body 1A. It has become. Then, as shown in FIG. 2, the main body control CPU 50 causes the sheet 14 to jam at the separation claw 25 of the fixing device 17, and a sheet detection signal is output from the fixing paper discharge sensor S2 even if a predetermined time elapses accordingly. Is not input, it is determined that a jam has occurred in the sheet 14, and a message prompting the user to jam is displayed by an operation panel (not shown) provided on the printer body.

  The user opens the main body opening / closing cover (not shown) to remove the sheet 14 remaining in the apparatus and closes the main body opening / closing cover again in accordance with this message in order to handle the jam. Thereafter, the main body power supply (not shown) is turned on, whereby the main body control CPU 50 resets the jammed state and performs a return operation including forced paper discharge.

  By the way, a sheet presence / absence detection sensor S3 which is a jam detection unit is provided upstream of the fixing nip of the fixing nip in the sheet conveyance direction. In addition, it is detected whether a jammed sheet exists between the fixing nip portion and the transfer portion. In the present embodiment, the sheet presence / absence detection sensor S3 is provided in the vicinity of the fixing nip of the fixing device 17 so as to prevent the wrapping around the fixing roller 21 in particular.

  This sheet presence / absence detection sensor S3 includes a sensor flag 28 as a detection member provided in the center of a direction (hereinafter referred to as a width direction) orthogonal to the sheet conveyance direction above the fixing entrance guide 24, and the width direction of the fixing entrance guide 24. The photointerrupter 29 is provided below a slot (not shown) formed at a position corresponding to the sensor flag 28 in the substantially central portion.

  Here, the sensor flag 28 is fixed to a sensor flag lever 28c shown in FIG. 3. Further, the sensor flag lever 28c connects the first shaft 28a and the second shaft 28b provided on both sides to both ends of the fixing frame 27. It is rotatably supported by the fixing frame 27 by being inserted into shaft holes 27a and 27b provided in the respective portions. In addition, since the sensor flag 28 is placed in the vicinity of the fixing roller, it is preferable to use a resin such as PBT, PET or the like in which glass is added to improve heat resistance and strength.

  A spring 31 is provided on the first shaft 28a of the sensor flag lever 28c, and each end of the spring 31 is engaged with the sensor flag 28 and the fixing frame 27 so that the sensor flag 28 is shown in FIG. It is energized counterclockwise. The fixing frame 27 to which one end of the spring 31 is locked is provided with a stopper portion (not shown) that comes into contact with the sensor flag 28 urged counterclockwise by the spring 31. Normally, the sensor flag 28 is held at a predetermined position that does not hinder the conveyance of the sheet 14 shown in FIG.

  Further, the second shaft 28 b of the sensor flag lever 28 c is inserted into a support member 33 provided on the outer wall surface of the fixing frame 27. In the vicinity of the tip of the second shaft 28b, as shown in FIG. 4, a projection 28d protruding in the radial direction of the second shaft 28b is formed. In addition, a push-in member 32 that is movable in the sensor flag axial direction is disposed on the peripheral surface of the second shaft 28 b, and the push-in member 32 is inserted into an opening hole 33 a formed in the support member 33.

  Here, a spring 34 is disposed between the pushing member 32 and the support member 33, and when pushed, the pushing member 32 moves while contracting the spring 34. Further, a locking portion 33b is formed on the inner wall surface of the opening hole 33a so that the claw 32a formed on the pressing member 32 is locked. The pressing member 32 is held by the claw 32a and the locking portion 33b. When pushed in, the spring 34 prevents the push-in member 32 from popping out. Reference numeral 35 denotes a pin that moves in conjunction with a solenoid (not shown) whose operation is controlled by the main body control CPU 50.

  On the other hand, the insertion end of the pushing member 32, when pushed, presses the projection 28d on the second shaft side and rotates the second shaft 28b (sensor flag lever 28c) via the projection 28d. have. Thereby, from a state where the pushing member 32 as shown in FIG. 4A is not pushed in, a solenoid (not shown) is turned on as shown in FIG. When the pushing member 32 is pushed by a predetermined amount, the projection 28d of the second shaft 28b is rotated by the cam shape of the pushing member 32. As a result, the sensor flag 28 is rotated clockwise in FIG. To a predetermined angle.

  When the sensor flag 28 rotates in this way, if there is no jam sheet, the light receiving portion of the photo interrupter 29 is shielded by the sensor flag 28, but if there is a jam sheet, the light receiving portion of the photo interrupter 29 is opened. As a result, the main body control CPU 50 can detect the presence of a jam sheet.

  In FIG. 4, reference numeral 37 denotes a spring having one end locked to the support member 33 and the other end locked to the second shaft 28 b. When the second shaft 28 b rotates, As shown, the spring 37 is rotated while being contracted. Thus, when the solenoid is turned off and the pushing member 32 is returned to the original position by the spring 34, the second shaft 28b is moved to the position shown in FIG. 4A by the spring force of the spring 37. You can go back.

  Here, when the sensor flag 28 is rotatably provided facing the conveyance guide surface of the fixing entrance guide 24 of the sheet 14 as in the present embodiment, the sensor flag 28 is rotated as shown in FIG. At this time, the sheet staying in the jam is pressed by the sensor flag 28 and is held by the fixing nip and the fixing entrance guide 24.

  By holding the jam sheet in this way, even when the remaining jam sheet is thin paper or the jam sheet is left in a high humidity environment for a long time and the stiffness is lost, the sensor flag 28 is pressed. Since the sheet is held by the fixing entrance guide 24, it is possible to eliminate the erroneous detection due to the “lifting” of the sheet as in the prior art. As a result, the presence of the sheet can be reliably detected, and the reliability of the printer main body 1A can be improved.

  As described above, the sensor flag 28 is provided to face the fixing entrance guide 24, and the main body power supply is turned on at a predetermined timing after the jam processing, that is, when the main body opening / closing cover opened for the jam processing is closed or after the jam processing. By turning the sensor flag 28 toward the fixing entrance guide side when the sheet is inserted, the presence or absence of a jam sheet is detected, so that the jam sheet can be reliably detected regardless of the type or state of the sheet 14. it can.

  Then, by making it possible to reliably detect the jam sheet in this way, it is possible to prevent the returning operation from restarting unless the jam sheet is completely removed from the printer body. The reliability of 1A can be improved.

  Further, by detecting the presence or absence of the jammed sheet by the sensor flag 28 while the sheet conveyance is stopped, the sensor flag 28 can be prevented from being worn by the conveyance of the sheet 14.

  Although the configuration in which the sensor flag 28 is operated by the solenoid has been described so far, the operation method of the sensor flag 28 is not limited to the above, and the sensor flag 28 is not the fixing device 17 but the printer main body 1A. Needless to say, it may be installed in the station. Further, the fixing device 17 may be an on-demand fixing device using a fixing film and a planar heating element instead of the heat roller fixing method.

  Next, a second embodiment of the present invention will be described.

  FIG. 5 is a diagram for explaining the configuration of the jam detecting means provided in the image forming apparatus according to the present embodiment.

  In FIG. 5, 36 is a sensor flag, and 36c is a sensor flag lever to which the sensor flag 36 is attached. In addition, 36a is the 1st axis | shaft of the sensor flag lever 36c, 36b is the 2nd axis | shaft, 36d is the projection part provided in the 2nd axis | shaft 36b, These 1st axis | shaft 36b, the 2nd axis | shaft 36b, and the projection part 36d are The same configuration and operation as the first axis, the second axis, and the protrusion of the sensor flag lever 28c in the first embodiment described above are achieved.

  Further, 36e is a protrusion formed at the tip of the sensor flag lever 36c, and 36f is a receiving portion formed on the sensor flag 36. The protrusion 36e of the sensor flag lever 36c is engaged with the receiving portion 36f of the sensor flag 36. By combining, the sensor flag lever 36c and the sensor flag 36 can be easily combined.

  Here, the sensor flag lever 36c is made of resin, and the sensor flag 36 is made of rubber or elastic elastomer. In the present embodiment, a polyester elastomer is used as the elastomer of the sensor flag 36 to provide a light shielding property so that a signal change of open / light shielding by a photo interrupter (see FIG. 2) can be performed.

  In this way, the sensor flag 36 is formed of an elastic member and is flexible so that the impact received by the sensor flag 36 when the sensor flag 36 rotates and collides with the fixing entrance guide 24 can be reduced. Thereby, damage to the sensor flag 36 can be prevented, and the collision sound can be reduced. Further, even when the sensor flag 36 rotates and comes into contact with the jammed sheet, the sheet 14 can be prevented from being damaged.

  In the present embodiment, the case where the sensor flag 36 is made of an elastic member has been described. However, the sensor flag 36 may be made elastic by using a leaf spring as the sensor flag 36. . This embodiment is particularly effective for small printers, copiers, and fax machines that require quiet design.

  In the above description, the laser printer (image forming apparatus) configured to convey the sheet 14 in the horizontal direction has been described. However, the present invention is not limited to this, and the sheet is discharged from the sheet feeding cassette. By shortening the distance to the tray, the time required for printing out can be shortened, and the sheet can be applied to an image forming apparatus in which the sheet is conveyed in a substantially vertical direction so that the apparatus can be downsized. .

  Next, an image forming apparatus according to a third embodiment of the present invention in which the sheet is conveyed in the substantially vertical direction will be described.

  FIG. 6 is a diagram illustrating a configuration of a laser printer as an example of an image forming apparatus according to the present embodiment. In FIG. 6, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  In FIG. 6, reference numeral 28A denotes a sensor flag constituting the sheet presence / absence detection sensor S3. This sensor flag 28A normally prevents the conveyance of the sheet 14 conveyed in the substantially vertical direction from the paper feed cassette 12 to the paper discharge tray 18. 6 is held at the position shown in FIG. 6, but when the main body is turned on, it is rotated in the clockwise direction against the direction of gravity by a solenoid (not shown).

  In the present embodiment, when the sensor flag 28A is not in operation, the sensor flag 28A is separated from the conveyance guide sheet metal 16c, which is a conveyance guide member, by its own weight. Therefore, the spring 31 shown in FIG.

  Then, when there is no jam sheet, the light receiving portion of the photo interrupter 29 is shielded by the sensor flag 28A. On the contrary, if the jam sheet exists, the photo interrupter 29 of the photo interrupter 29 operates even if the sensor flag 28A operates. Since the light receiving unit is opened, a jam sheet can be detected.

  Here, in the laser printer according to the present embodiment, during operation, the sheet is transported by the transport guide plate 16c and the electrostatic adsorption force due to the charge received by the transfer unit, and the sheet transport path C (the transport guide surface). ) Is stably conveyed, but a jam occurs in the fixing unit, and the sheet that has not reached the fixing nip is suspended in the machine as time elapses.

  However, even in such a case, the presence of the sheet can be reliably detected even when the sheet is suspended by rotating the sensor flag 28 and pressing the jam sheet in the conveyance guide direction. This can improve the reliability of the printer body 1A.

  As described above, since the jammed sheet can be accurately detected even when the sheet conveying direction is substantially vertical or the fixing device 17 is disposed at the upper portion as in the present embodiment, the reliability of the printer main body 1A can be determined. Can be improved.

1 is a diagram illustrating a configuration of a laser beam printer which is an example of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is an enlarged view of the vicinity of a sheet entrance of a fixing device provided in the laser beam printer. The figure explaining the structure of the sensor flag which comprises the sheet presence detection sensor provided in the said laser beam printer. The figure explaining the structure which rotates the said sensor flag. FIG. 6 is a diagram illustrating a configuration of a sensor flag that constitutes a jam detection unit provided in an image forming apparatus according to a second embodiment of the present invention. FIG. 10 is a diagram illustrating a configuration of a laser beam printer which is an example of an image forming apparatus according to a third embodiment of the present invention. 1 is a diagram illustrating a configuration of a conventional image forming apparatus. The figure explaining the structure of the conventional resist sensor. FIG. 6 is a diagram illustrating a state when a fixing winding jam occurs in a conventional image forming apparatus. FIG. 6 is a diagram illustrating a state where a sensor is provided between a transfer unit and a fixing unit in a conventional image forming apparatus. The figure which shows the structure of the other conventional image forming apparatus.

Explanation of symbols

1A Laser beam printer body 14 Sheet 16c Conveying guide sheet metal 17 Fixing device 21 Fixing roller 22 Pressure roller 24 Fixing entrance guide 28 Sensor flag 28A Sensor flag 29 Photo interrupter 36 Sensor flag 50 Main body control CPU
C sheet conveyance path S1 registration sensor S2 fixing sheet discharge sensor S3 sheet presence / absence detection sensor

Claims (7)

In an image forming apparatus provided with a jam detecting means for detecting a jam of a sheet,
A conveyance guide member constituting a sheet conveyance path through which the sheet passes;
A rotatable detection member provided facing the sheet conveyance surface of the conveyance guide member and constituting the jam detection means;
With
An image forming apparatus, wherein the presence or absence of a jammed sheet is detected by rotating the detection member toward the conveyance guide member at a predetermined timing.   The jam detecting means has a photo interrupter disposed on the back side of the sheet conveying surface of the conveying guide member, and when the detecting member cannot be detected when the detecting member is rotated, the jam sheet is jammed. The image forming apparatus according to claim 1, wherein the image forming apparatus determines that the image is present. An open / close cover for removing the jam sheet;
The image forming apparatus according to claim 1, wherein the detection member is rotated after the opening / closing cover is opened or closed or after power is turned on.   2. When the sheet conveyance path is provided in a substantially vertical direction, the presence or absence of the jam sheet is detected by the detection member, and the jam sheet is held together with the conveyance guide member. The image forming apparatus according to claim 3. A fixing means having a heat fixing means and a pressure means for contacting the heat fixing means and forming a nip portion;
The image forming apparatus according to claim 1, wherein the detection member is provided on an upstream side of the nip portion of the fixing unit.   The image forming apparatus according to claim 1, wherein the detection member has elasticity. The image forming apparatus according to claim 1, wherein a part of the detection member is formed of an elastic elastomer.

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