JP5820764B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for reducing contamination inside the apparatus due to toner.

  2. Description of the Related Art Conventionally, there is an image forming apparatus that stops paper conveyance and image forming operations when a recording paper jam (paper jam) occurs in a paper conveyance path without normal conveyance of the recording paper. If the image forming operation is interrupted in such a state that the image forming operation is not completed, the toner image before being transferred onto the recording paper may remain on the surface of the photosensitive drum, and the inside of the apparatus may be stained by the toner of the toner image. is there. For this reason, for example, as shown in Patent Document 1 below, for toner that has already been transferred onto the recording paper, the toner is fixed on the recording paper, and then the recording paper is discharged from the inside of the apparatus. An image forming apparatus that prevents the toner on the recording paper from diffusing inside the apparatus has been proposed.

JP 2003-241583 A

  However, the image forming apparatus disclosed in Patent Document 1 reduces the situation in which unfixed toner after being transferred to a recording sheet leaves the recording sheet and remains inside the apparatus. It is impossible to reduce contamination inside the apparatus caused by a toner image formed on the surface of the toner image and not yet transferred to the recording paper. For this reason, even with the image forming apparatus disclosed in Patent Document 1, countermeasures against contamination inside the apparatus due to toner at the time of recording paper jam are not sufficient.

  The present invention has been made to solve the above-described problem. When a jam of a recording medium is detected, the toner image remaining on the surface of the photosensitive drum can be removed, and the inside of the apparatus caused by the residual toner image can be removed. The object is to further reduce the contamination.

According to a first aspect of the present invention, there is provided an image forming unit that forms an image by forming a toner image on a surface of a photosensitive drum and transferring the toner image to a recording medium;
A transport unit that transports the recording medium from a paper feed mechanism to a discharge unit of the recording medium through a transfer position of the toner image by the image forming unit;
The recording medium jam of the recording medium conveyed by the conveying unit, the recording medium jam detector for detecting in the conveying direction downstream side of the recording medium than the transfer position,
Continuous image formation comprising a transport operation by the transport unit that transports a plurality of the recording media to the transfer position in succession, and continuous image formation by the image forming unit for each of the continuously transported recording media. A control unit for controlling the operation;
A recording medium detection unit that detects whether or not there is the recording medium located at the transfer position;
The control unit is a case where the recording medium jam is detected by the recording medium jam detection unit during the control of the continuous image forming operation, and the recording medium is positioned at the transfer position by the recording medium detection unit. When it is detected that the recording medium is detected, the conveyance unit stops conveyance of each recording medium, and at this time, the toner image already formed on the surface of the photosensitive drum is positioned at the transfer position. A toner removing operation for transferring the image to the recording medium by the image forming unit ,
When the recording medium jam is detected by the recording medium jam detection unit during the control of the continuous image forming operation, the recording medium detection unit detects that the recording medium is not located at the transfer position. When this is done, the recording medium to be transported next is transported to the transfer position by the transport unit, and the toner image already formed on the surface of the photosensitive drum at this point is transported to the transported recording medium. a medium, an image forming apparatus Ru to perform the toner removal operation to transfer by the image forming unit.

In this invention, when a recording medium jam is detected by the recording medium jam detection unit on the downstream side in the conveyance direction of the recording medium with respect to the transfer position of the toner image by the image forming unit, the control unit controls each recording medium in the conveyance unit. The toner image already formed on the surface of the photosensitive drum at this time is transferred to the recording medium positioned at the transfer position by the image forming unit. The toner image already formed on the surface of the photosensitive drum is transferred to the recording medium and removed from the surface of the photosensitive drum.

For this reason, if the operator removes the recording medium onto which the toner image has been transferred by the toner removal operation from the inside of the apparatus as jamming processing of the recording medium after completion of the toner removal operation, an image caused by the jam By interrupting the forming operation, the toner image remaining on the recording medium without being transferred onto the surface of the photosensitive drum can be removed without requiring the addition of a special mechanism. Thus, when a jam of the recording medium is detected, it is possible to remove a toner image that has been formed on the surface of the photosensitive drum and has not been transferred to the recording medium. In addition, since the operator removes the recording medium on which the residual toner image has been transferred, the toner collected on the recording medium by the transfer does not remain inside the apparatus. Can be further reduced.

Further, in the present invention, even when a recording medium is not present at the transfer position when a jam is detected, the control unit causes the recording unit to be transported next to the transfer position by the transport unit so that the transfer is performed. Since the untransferred residual toner is transferred to the recording medium conveyed to the position, even if a jam is detected in a state where the preceding recording medium has already passed the transfer position, the untransferred photoconductor The toner remaining on the surface of the drum can be reliably removed from the surface of the photosensitive drum.

The invention according to claim 2 is the image forming apparatus according to claim 1 , wherein the control unit is configured to detect the jam of the recording medium by the recording medium jam detection unit during the control of the continuous image forming operation. If it is determined that the toner image already formed on the surface of the photosensitive drum has not been transferred to the recording medium at this time, the toner is transferred to the transport unit and the image forming unit. When the removal operation is performed and it is determined that the toner image on the surface of the photosensitive drum has been transferred to the recording medium, the toner removal operation is not performed by the transport unit and the image forming unit. .

According to the present invention, when a jam of the recording medium is detected during the control of the continuous image forming operation, the toner image already formed on the surface of the photosensitive drum at this time is recorded on the recording medium. When the toner image has not been transferred, that is, when there is a toner image remaining on the surface of the photosensitive drum, the toner removal operation is performed, and when the toner image on the surface of the photosensitive drum has already been transferred to the recording medium, Since the removal operation is not performed, the toner removal operation is performed only when it is necessary to remove the residual toner image on the surface of the photosensitive drum, and does not contribute to the removal of the toner remaining on the surface of the photosensitive drum. Useless operations can be reduced.

The invention according to claim 3 is the image forming apparatus according to claim 1 or 2 , wherein the image forming unit is configured to rotate the photosensitive drum and the photosensitive drum. And at least a charging part, an exposure part, a development part, and a transfer part,
In the driving of the image forming unit during the toner removal operation, the control unit performs the rotation of the toner image already formed on the surface of the photosensitive drum by the rotation of the peripheral surface of the photosensitive drum toward the transfer position. The charging unit, the exposure unit, and the developing unit are stopped until the transfer unit passes through the transfer position, and at least the drive unit and the transfer unit are driven.

  According to the present invention, the control unit controls the driving of the driving unit and the transfer unit necessary for transferring the toner image on the surface of the photosensitive drum to the recording medium during the toner removal operation, and the toner on the surface of the photosensitive drum. The toner is removed until the image passes through the transfer position, and during this time, the charging unit, the exposure unit, and the development unit that do not contribute to the transfer of the toner image to the recording medium are stopped. This can be performed after eliminating unnecessary operations that do not contribute to the removal.

  According to the present invention, it is possible to remove the toner image remaining on the surface of the photosensitive drum when detecting a jam of the recording medium, and it is possible to further reduce the contamination inside the apparatus due to the toner image.

1 is a side view illustrating a schematic mechanical configuration of an image forming apparatus according to an embodiment of the present disclosure. 1 is a block diagram illustrating a schematic electrical configuration of an image forming apparatus. 5 is a flowchart illustrating a first embodiment of processing when a paper jam is detected during image formation in the image forming apparatus. 12 is a flowchart illustrating a second embodiment of processing when a paper jam is detected during image formation in the image forming apparatus. 12 is a flowchart illustrating a third embodiment of processing performed when a paper jam is detected during image formation in the image forming apparatus.

  Hereinafter, an image forming apparatus 1 according to an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a side view showing a schematic mechanical configuration of an image forming apparatus 1 according to an embodiment of the present invention.

  The image forming apparatus 1 includes an image forming unit 2, a paper transport mechanism 3, a paper feed mechanism 4, a fixing unit 5, and a paper discharge tray 6. In the present embodiment, a case where the image forming apparatus 1 is a printer will be described as an example.

  The image forming unit 2 performs an image forming operation for forming a toner image on the recording paper P (an example of a recording medium) conveyed from the paper feeding mechanism 4 by the paper conveying mechanism 3. The image forming unit 2 includes a photosensitive drum 21, a charging unit 22, an exposure unit 23, a developing unit 24, and a transfer roller 25.

  The photosensitive drum (image carrier) 21 is provided with a photosensitive layer on the surface thereof, and the surface potential is set to a predetermined value by charging by the charging unit 22.

  The charging unit 22 is provided at a position facing the surface of the photosensitive drum 21. The charging unit 22 charges the circumferential surface of the photosensitive drum 21 rotating in the direction of the arrow shown in FIG. 1 substantially uniformly with a predetermined charging capability.

  The exposure unit 23 is a position facing the surface of the photosensitive drum 21 and is provided downstream of the charging unit 22 in the rotational direction of the circumferential surface of the photosensitive drum 21. The exposure unit 23 applies laser light indicated by arrows in FIG. 1 corresponding to image data input from a computer (not shown) connected to the image forming apparatus 1 via a network to the photosensitive drum 21 after charging. Irradiating the circumferential surface, an electrostatic latent image corresponding to the image data is formed on the circumferential surface of the photosensitive drum 21 on the circumferential surface of the photosensitive drum 21. The exposure unit 23 is a laser exposure unit, and a laser light source (not shown) that outputs a laser beam, a polygon mirror (not shown) that reflects the laser beam toward the surface of the photosensitive drum 21, and a reflection by the polygon mirror. Optical components such as a lens (not shown) and a mirror (not shown) for guiding the laser beam to the photosensitive drum 21 are provided. Note that the exposure unit 23 may be made of another method such as a method of irradiating the surface of the photosensitive drum 21 with an LED (Light Emitting Diode).

  The developing unit 24 supplies toner (not shown) to the electrostatic latent image formed by the exposure unit 23 on the surface of the photosensitive drum 21. By supplying the toner by the developing unit 24, the toner is attached to the electrostatic latent image on a portion exposed by the exposure unit 23 on the surface of the photosensitive drum 21, and a toner image corresponding to the electrostatic latent image is formed. . To the developing unit 24, toner is supplied from a toner container (not shown).

  The transfer roller (transfer unit) 25 is provided at a position facing the photoconductor drum 21 and on the downstream side of the developing unit 24 in the rotation direction of the photoconductor drum 21. A transfer bias having a polarity different from that of the toner is applied to the transfer roller 25 by a transfer bias applying mechanism (not shown). The transfer roller 25 sensitizes the toner image formed on the surface of the photosensitive drum 21. At the nip portion between the body drum 21 and the transfer roller 25 (hereinafter referred to as a toner image transfer position N), the toner image is transferred onto the recording paper P conveyed between the surface of the photosensitive drum 21 and the surface of the transfer roller 25.

The fixing unit 5 is disposed downstream of the toner image transfer position N onto the recording paper P by the image forming unit 2 in the conveyance direction of the recording paper P, and is transferred to the recording paper P that has passed through the image forming unit 2. The toner image is heat-pressed by the heat roller 51 and the pressure roller 52 and fixed on the recording paper P. The heat roller 51 and the pressure roller 52 are rotationally driven by a rotational driving force supplied from a main drive motor 9 (see FIG. 2) described later.

  The sheet conveyance mechanism (conveyance unit) 3 includes a sheet conveyance path 31, a conveyance roller pair 32, a registration roller pair 33, and switchback roller pairs 341 and 342. The conveyance roller pair 32, the registration roller pair 33, and the switchback roller pair 341, 342 are rotationally driven by the rotational driving force supplied from the main drive motor 9.

  The paper transport path 31 is a transport path through which the recording paper P is transported from the paper feed mechanism 4 to the paper discharge tray 6 through the image forming unit 2 and the fixing unit 5. A conveyance roller pair 32 is provided at each position of the paper conveyance path 31, and the recording paper P is conveyed in the paper conveyance path 31 by the nip of the roller pair by the rotation of the roller pair forming the conveyance roller pair 32. The paper is fed from the paper feed mechanism 4 to the image forming unit 2, the fixing unit 5, and the paper discharge tray 6.

  In addition, the paper transport path 31 includes a main transport path 311 and a reverse transport path 312. The main transport path 311 is a transport path that connects the paper feed mechanism 4 to the image forming unit 2, the fixing unit 5, and the paper discharge tray 6. The reverse conveyance path 312 is a conveyance path for conveying the recording paper P, on which image formation has been completed on one side of the recording paper P in the image forming unit 2, to the image forming unit 2 again for duplex printing. The reverse conveyance path 312 branches from the main conveyance path 311 on the downstream side in the conveyance direction of the recording paper P from the fixing unit 5 in the main conveyance path 311, and is downstream of the paper feed mechanism 4 in the conveyance direction of the recording paper P. In addition, it joins the main transport path 311 at a position upstream of the image forming unit 2.

  The switchback roller pairs 341 and 342 are disposed in the main conveyance path 311 between the fixing unit 5 and the downstream side in the conveyance direction of the recording paper P to the paper discharge tray 6. The switchback roller pairs 341 and 342 convey the recording paper P between the fixing unit 5 and the paper discharge tray 6 under the control of the control unit 10 (FIG. 2) described later. When the recording paper P that has passed through the image forming unit 2 and the fixing unit 5 is discharged to the paper discharge tray 6, the switchback roller pair 341, 342 is a switch whose rear end of the recording paper P is downstream in the conveyance direction of the recording paper P. Until the back roller pair 342 leaves, the recording paper P is conveyed toward the paper discharge tray 6 by the switch back roller pairs 341 and 342.

  On the other hand, the switchback roller pair 341, 342 passes the fixing unit 5 when the recording paper P that has passed through the image forming unit 2 and the fixing unit 5 is conveyed again to the image forming unit 2 for duplex printing. The recording paper P is first conveyed toward the paper discharge tray 6 by the switchback roller pairs 341 and 342. The trailing edge of the recording paper P in the transport direction leaves the switchback roller pair 341 on the upstream side in the transport direction of the recording paper P, and the switchback roller pair 342 on the downstream side in the transport direction of the recording paper P. The switchback roller pairs 341 and 342 are rotated in the reverse direction under the control of the control unit 10. At this time, the recording paper P is guided to the reverse conveyance path 312 by a conveyance path switching mechanism (not shown) provided at a branch point of the main conveyance path 311 and the reverse conveyance path 312. In this way, the recording paper P that is reversely fed through the main conveyance path 311 by the switchback roller pair 341 and 342 is guided by the reverse conveyance path 312 and is upstream of the image forming unit 2 in the conveyance direction of the recording paper P. It is conveyed to the main conveyance path 311 and is conveyed again from here to the image forming unit 2. At the time of re-conveying, the recording paper P is opposite to the surface on which the image has been previously formed by the reversing operation by the switchback roller pair 341 and 342 and the conveying operation of the recording paper P in the reversing conveying path 312. Since the surface faces the photosensitive drum 21, image formation is performed by the image forming unit 2 on the other surface different from the surface on which image formation has already been performed.

The registration roller pair 33 is provided on the upstream side in the transport direction of the recording paper P of the image forming unit 2 in the main transport path 311, and the recording paper P transported in the main transport path 311 is transferred to the photosensitive drum 21 and the transfer roller 25. Are adjusted, that is, the timing at which the toner is transferred to the transfer position N of the toner image by the image forming unit 2.

  In addition, paper detection sensors 71, 72, 73, and 74 are provided at various locations on the paper transport path 31. The sheet detection sensors 71, 72, 73, and 74 are, for example, optical sensors having a light emitting unit and a light receiving unit provided at positions facing each other across the paper conveyance path 31, and the light receiving unit emits light from the light emitting unit. When light is received, a paper non-signal indicating that no recording paper P exists at the position where the paper detection sensor is located is output to the control unit 10, and the recording paper P is interposed between the light emitting unit and the light receiving unit. When the light receiving unit is not receiving light from the light emitting unit, a paper presence signal indicating that the recording paper P exists at the position where the paper detection sensor is provided is output to the control unit 10.

  In addition, the control unit 10 detects a time when the detection signal received from the paper detection sensor changes from a paper non-signal to a paper presence signal as a time when the leading end of the recording paper P reaches the paper detection sensor, and the paper detection sensor Is detected as the time when the trailing edge of the recording paper P has passed through the paper detection sensor.

The arrangement of each paper detection sensor will be described. For example, the paper detection sensor 71 is provided at a position upstream of the image forming unit 2 and the registration roller pair 33 in the transport direction of the recording paper P in the main transport path 311. The paper detection sensor 72 is provided at a position downstream of the toner image transfer position N and the fixing unit 5 in the conveyance direction of the recording paper P in the main conveyance path 311. The paper detection sensor 73 is further at the rear end of the main conveyance path 311 on the downstream side in the conveyance direction of the recording paper P than the paper detection sensor 72, that is, at the connection portion between the main conveyance path 311 and the sheet discharge tray 6. Is provided. The paper detection sensor 74 is provided in the reverse conveyance path 312.

  The control unit 10 detects a paper jam (a jam of the recording paper P) in the paper transport path 31 based on the paper presence signal and the paper no signal acquired from the paper detection sensors 71, 72, 73 and 74. Details of the paper jam detection will be described later.

  Further, the registration sensor 75 is provided on the upstream side in the conveyance direction of the recording paper P with respect to the registration roller pair 33 in the main conveyance path 311 and on the downstream side in the conveyance direction of the recording paper P with respect to the paper detection sensor 71. The configuration of the registration sensor 75 is the same as that of the paper detection sensor 71.

The control unit 10 uses a timing at which the arrival of the leading end of the recording paper P is detected by the paper detection sensor 71, and a predetermined time (paper transport speed by the registration roller pair 33 and the registration sensor 75). And the distance between the toner image transfer positions N is determined), and the recording paper P forms an image so that the recording paper P is conveyed to the toner image transfer position N by the image forming unit 2 after the passage. The timing at which the image forming unit 2 transfers the toner image onto the recording paper P matches the timing at which the recording paper P arrives at the transfer position N by adjusting the timing at which the unit 2 arrives at the transfer position N. To be adjusted.

  Further, the control unit 10 detects that the trailing edge of the recording sheet P has been separated from the switchback roller pair 342 described above at the timing when the passage of the trailing edge of the recording sheet P is detected by the sheet detection sensor 73. .

  The paper feed mechanism 4 is a mechanism for feeding the recording paper P to the paper transport path 31 and includes a paper feed cassette 40 and a paper feed roller 41. The paper feed cassette 40 stores a plurality of recording papers P in a stacked state. The paper feed roller 41 contacts the surface of the uppermost recording paper P among the recording paper P accommodated in the paper feeding cassette 40, and one sheet of recording paper P is fed from the uppermost portion by the rotation of the paper feeding roller 41. Pick up one by one and feed it to the paper transport path 31.

  FIG. 2 is a block diagram showing an electrical schematic configuration of the image forming apparatus 1. FIG. 2 shows a configuration related to the present invention.

  First, an electrical schematic configuration of the image forming apparatus 1 will be described.

  The image forming apparatus 1 includes a control unit 10 that controls overall operation of the image forming apparatus 1. The control unit 10 mainly drives the image forming unit 2, the drum motor 8, the main drive motor 9, and the fixing heater 12.

  As described above, the main drive motor 9 is a drive source that supplies a rotational drive force to the transport roller pair 32, the switchback roller pairs 341, 342, the paper feed roller 41, and the registration roller pair 33. Further, the main drive motor 9 supplies a rotational driving force to a pair of fixing rollers including a heat roller 51 and a pressure roller 52 of the fixing unit 5.

  The drum motor 8 is a driving source that supplies a rotational driving force to a rotating shaft (not shown) of the photosensitive drum 21. In FIG. 2, the drum motor 8 is described separately from the image forming unit 2, but in the present embodiment, the drum motor 8 is described as a part of the image forming unit 2.

  Further, the control unit 10 drives and controls the paper detection sensors 71, 72, 73, and 74, and acquires the paper presence signal and the paper absence signal described above from the paper detection sensors 71, 72, 73, and 74. Based on the paper presence signal and the paper absence signal acquired from the paper detection sensors 71, 72, 73, 74, the control unit 10 determines the presence / absence of the paper at the position where each paper detection sensor is disposed.

  The control unit 10 controls recording paper conveyance, image formation, fixing operation, and paper jam detection when performing image formation on the recording paper P, as well as toner removal operation described later.

  Subsequently, operation control during image formation in the image forming apparatus 1 will be described.

  During the image forming operation, the control unit 10 picks up the recording paper P stored in the paper feed cassette 40 one by one by the paper feed roller 41 and feeds it to the main transport path 311. The recording paper P is transported toward the image forming unit 2 by the provided transport roller pair 32. In the case of continuous printing in which image formation is continuously performed on a plurality of recording papers P, the control unit 10 uses the paper feed roller 41 and the conveying roller pair 32 to move toward the image forming unit 2 to form a plurality of recording papers P. Are conveyed continuously.

The control unit 10 uses a timing at which the recording paper P is started to be transported to the main transport path 311 by the paper feed roller 41, and uses a predetermined time from the timing (the paper feed roller 41, the transport roller pair 32, and the registration roller pair). 33 is determined on the basis of the sheet conveyance speed of 33 and the distance between the sheet feeding mechanism 4 and the toner image transfer position N), the toner image on the surface of the photosensitive drum 21 is transferred to the recording sheet P. As described above, the image forming unit 2 starts to form a toner image to be transferred onto the recording paper P. At this time, the control unit 10 drives the image forming unit 2 including the drum motor 8 to start a series of processes of charging, exposure, development, and transfer by the above-described units of the image forming unit 2.

Further, the control unit 10 uses the paper detection signal output from the registration sensor 75 provided in the vicinity of the position where the registration roller pair 33 is disposed, so that the leading end of the recording paper P is the toner image transfer position of the image forming unit 2. By adjusting the timing of reaching N by the registration roller pair 33, the transfer timing of the toner image onto the recording paper P by the image forming unit 2 matches the timing of arrival of the recording paper P at the transfer position N. To be adjusted. The control unit 10, for example, moves to the toner image transfer position N of the image forming unit 2 at a timing after the predetermined time elapses after the leading edge of the recording paper P is detected by the registration sensor 75. Adjust to reach.

The control unit 10 sensitizes the recording paper P by the registration roller pair 33 to the toner image transfer position N of the image forming unit 2, that is, the recording paper P conveyed between the photosensitive drum 21 and the transfer roller 25. The toner image on the surface of the body drum 21 is transferred by the transfer roller 25. The toner images on the photosensitive drum 21 are sequentially transferred to the recording sheets P that are continuously conveyed between the photosensitive drum 21 and the transfer roller 25.

The control unit 10 causes the recording paper P, on which image formation in the image forming unit 2 has been completed, to pass through the fixing unit 5, and then is discharged to the paper discharge tray 6 by the switchback roller pairs 341 and 342. When performing duplex printing, the above-described reversing operation is performed by the switchback roller pairs 341 and 342, and the recording paper P is conveyed again from the reversal conveyance path 312 to the toner image transfer position N of the image forming unit 2. Then, after the image forming unit 2 forms an image on the other side of the recording paper P, the recording paper P is discharged to the paper discharge tray 6 by the conveying roller pair 32 or the like.

In the case of continuous printing in which the image forming unit 2 continuously forms an image on a plurality of recording sheets P, the image forming unit 2 is transferring the toner image to the preceding recording sheet P. In addition, when the formation of the toner image to be transferred to the recording paper P has been completed, the control unit 10 moves to the surface of the photosensitive drum 21 that is downstream of the transfer position N in the rotation direction of the photosensitive drum 21. , this next recording sheet P on which the toner image has been transferred at the time, to form a toner image transferred to the recording paper P which is conveyed to the transfer position N by the image forming unit 2.

Further, during the conveyance of the recording paper P during the image formation, the control unit 10 determines that each recording paper P is based on the paper presence signal and the paper no signal from the paper detection sensors 71, 72, 73, 74. It is determined whether or not each paper detection sensor has reached the placement position in the paper transport path 31 at a timing suitable for the toner image transfer by the image forming unit 2, and the recording paper P is placed at each placement position at an appropriate timing. If it is determined that the paper jam has not been reached, it is determined that a paper jam has occurred in the paper transport path 31, that is, paper jam has occurred.

  For example, the control unit 10 starts the feeding of the recording paper P from the paper feeding roller 41, and determines a predetermined elapsed time (paper feeding speed by the paper feeding roller 41 and the conveyance roller pair 32 and the paper feeding mechanism). 4 is determined on the basis of the distance from each sheet detection sensor 71 to the sheet detection sensor 71, the recording sheet P is not detected by the sheet detection sensor 71, or the sheet presence signal from the sheet detection sensor 71 and the sheet are detected. Based on the no signal, the control unit 10 detects the leading end of the recording paper P, and then the predetermined time (the recording paper P transport speed by the transport roller pair 32 and the length of the recording paper P in the transport direction of the recording paper P). If the trailing edge of the recording paper P is not detected even after elapse, it is determined that a paper jam has occurred.

  Further, the control unit 10 determines the paper detection sensor 72 from a timing at which the recording paper P is sent out by the registration roller pair 33 and a predetermined elapsed time (from the paper conveyance speed by the registration roller pair 33 and the registration roller pair 334. The recording paper P is not detected by the paper detection sensor 72 even after a lapse of (determined based on the distance to the paper detection sensor 72), or a paper presence signal and a paper no signal from the paper detection sensor 72 On the basis of this, after the control unit 10 detects the leading end of the recording paper P, it is based on a predetermined time (the recording paper P transport speed by the registration roller pair 33 and the length of the recording paper P in the recording paper P transport direction). If the trailing edge of the recording paper P is not detected after a lapse, it is determined that a paper jam has occurred. The control unit 10 similarly detects a paper jam for the other paper detection sensors 73 and 74.

  When it is determined that a paper jam has occurred, the control unit 10 stops the main drive motor 9 at this time, and stops the operation related to the paper conveyance path 31 by each of the rollers or roller pairs. The paper detection sensors 72, 73, 74 and the control unit 10 are examples of the paper jam detection unit in the claims.

  Next, a first embodiment of toner removal processing when a paper jam is detected during continuous printing in the image forming apparatus 1 will be described. FIG. 3 is a flowchart illustrating a first embodiment of processing in the image forming apparatus 1 when a paper jam is detected during image formation. Hereinafter, an example in which processing at the time of paper jam detection is performed based on the state of the recording paper detected by the paper detection sensor 73 will be described.

  In the present embodiment, it is assumed that the control unit 10 causes the image forming unit 2 and the paper transport mechanism 3 to perform the continuous printing (S1). In the continuous printing, the control unit 10 causes the image forming unit 2 to sequentially perform image formation and transfer on each recording paper P continuously conveyed by the paper conveyance mechanism 3. The control unit 10 performs the above-described paper jam detection process based on the paper presence signal and the paper absence signal acquired from the paper detection sensors 71 to 74.

Here, the control unit 10 feeds the recording paper P from the paper feed mechanism 4 to the main transport path 311, and then downstream of the transfer position N of the toner image by the photosensitive drum 21 and the transfer roller 25 in the paper transport direction. A paper presence signal indicating that the leading edge of the recording paper P has been detected is awaited from the paper detection sensor 73 which is one of the paper detection sensors arranged on the side (NO in S2, NO in S3).

Based on the time measured by a built-in timer function (not shown) or the like, the control unit 10 detects the paper detection sensor 73 from the timing when the recording paper P is sent out from the registration roller pair 33 to when a predetermined time elapses. When the sheet presence signal is acquired for the recording sheet P from (NO in S3, YES in S2), the execution of the contents indicated by the print job for the continuous printing performed in S1 is continued (NO in S8, S1). ). Note that the processing ends when all the print contents indicated by the print job for the above-described continuous printing are completed (YES in S8). Here, the predetermined time is, for example, the recording in which the registration roller pair 33 is started to rotate and the recording paper P is conveyed by the main conveyance path 311 after the recording paper P is conveyed by the registration roller pair 33. This is a preset time as the time required for the leading edge of the paper to move from the paper feed mechanism 4 to the paper detection sensor 73 through the toner image transfer at the transfer position.

On the other hand, the control unit 10 does not acquire a paper presence signal for the recording paper P from the paper detection sensor 73 even after the predetermined time has elapsed (NO in S2, YES in S3), that is, When a paper jam is detected by the paper detection sensor on the downstream side in the conveyance direction of the recording paper P from the toner image transfer position N by the image forming unit 2, the control unit 10 stops the main drive motor 9. The driving of the drum motor 8 is continued with the conveying operation of all the recording papers P in the paper conveying path 31 stopped and the charging unit 22, the exposing unit 23, and the developing unit 24 of the image forming unit 2 stopped. Then, a toner removing operation for continuing the transfer process by the transfer roller 25 is performed (S4).

As a result, the control unit 10 is already exposed to the recording paper P existing at the transfer position N at this time, for example, the recording paper P to which the toner image is being transferred by the image forming unit 2 at this time. The toner image formed on the surface of the body drum 21 is transferred. This control toner image previously formed on the surface of the photosensitive drum 21 at this time, the toner image for transfer to the recording paper P, or the subsequent recording sheet which is conveyed subsequent to the recording paper P Any of the toner images for transfer to the toner image is transferred to the recording paper P during transfer of the toner image at the time of paper jam detection.

The controller 10 performs the toner removal operation until the toner image already formed on the surface of the photosensitive drum 21 passes the toner image transfer position N by the image forming unit 2 (NO in S5, S5). When the control unit 10 determines that the toner image on the surface of the photosensitive drum 21 has passed the toner image transfer position N of the image forming unit 2 (YES in S5), the control unit 10 and the drum motor 8 of the image forming unit 2 The transfer process of the transfer roller 25 is stopped (S6). Note that whether or not the toner image on the surface of the photosensitive drum 21 has passed the toner image transfer position N of the image forming unit 2 is determined when the control unit 10 starts forming the toner image ( from the time) that initiated the exposure for the toner image formed, with the elapsed predetermined time, the toner image on the surface of the photosensitive drum 21, passes through the toner image transfer position N of the image forming section 2 Judge. This predetermined time is the time when the surface of the exposed photosensitive drum 21 is exposed from the time of exposure for forming the toner image (when the exposure is stopped due to the stop of the image forming operation). This time is assumed to reach the toner image transfer position N by the rotation of the photosensitive drum 21. The predetermined time is determined based on the exposure timing, the distance of the peripheral surface of the photosensitive drum 21 from the exposure point by the exposure unit 23 to the toner image transfer position N, and the rotational speed of the photosensitive drum 21.

  After that, the control unit 10 performs processing such as displaying a message indicating that a paper jam has occurred on the display unit 473, and then temporarily stops the overall operation of the image forming apparatus 1. stand by. That is, control for causing the image forming apparatus 1 to transition to a paper jam clearing standby state in which the operation is temporarily stopped until the recording paper that is the cause of the paper jam is removed from the inside of the image forming apparatus 1. (S7). After this, the processes of S1 to S8 are repeated until the continuous printing is completed (YES in S8).

According to the first embodiment, the toner image already formed on the surface of the photosensitive drum 21 when the paper jam occurs is present at the toner image transfer position N of the image forming unit 2 when the paper jam occurs. It is transferred to the recording paper P and removed from the surface of the photosensitive drum 21.

  For this reason, if the operator removes the recording paper P with the toner image transferred from the inside of the apparatus as a paper jam process after the toner removal is completed, the image forming operation is interrupted due to the paper jam. The untransferred toner image remaining on the surface of the photosensitive drum 21 can be removed without the need for adding a special mechanism.

As described above, according to the first embodiment, the residual toner does not remain inside the apparatus due to the removal of the recording paper P onto which the residual toner image has been transferred by the operator. Dirt can be reduced more than before.

Further, the controller 10 performs the rotation process of the drum motor 8 and the transfer process of the transfer roller 25 necessary for transferring the toner image on the surface of the photosensitive drum 21 onto the recording paper P during the toner removal operation. 21 until the residual toner image on the surface passes through the toner image transfer position N, during which the charging unit, the exposure unit, and the development unit that do not contribute to the transfer of the residual toner image onto the recording paper P are stopped. By doing so, the toner removal operation can be performed after eliminating unnecessary operations that do not contribute to the toner removal.

  Next, a second embodiment of toner removal processing when a paper jam is detected during continuous printing in the image forming apparatus 1 will be described. FIG. 4 is a flowchart illustrating a second embodiment of processing when a paper jam is detected during image formation in the image forming apparatus 1. The description of the same processing as that of the first embodiment shown in FIG. 3 is omitted.

In the second embodiment, when the controller 10 does not acquire the paper presence signal from the paper detection sensor 73 even after the predetermined time has elapsed (NO in S12, YES in S13), that is, When a paper jam is detected by the paper detection sensor 73 on the downstream side in the transport direction of the recording paper P from the transfer position N by the image forming unit 2, the recording paper P is the toner by the image forming unit 2 at this time. It is determined whether or not the image exists at the image transfer position N (S14).

For example, the control unit 10 starts the transfer of the toner image by the image forming unit 2 from the position at which the registration sensor 75 is located after the trailing edge of the recording paper P is detected by the registration sensor 75. A predetermined time (determined on the basis of the sheet conveyance speed by the registration roller pair 33 and the distance between the registration roller pair 33 and the toner image transfer position N) as a time required for the conveyance to the position N. If the paper jam has not been detected, it is determined that the recording paper is present at the toner image transfer position N by the image forming unit 2. In this case, the control unit 10 and the registration sensor 75 are examples of the recording medium detection unit in the claims.

Here, when the control unit 10 determines that the recording paper P exists at the toner image transfer position N by the image forming unit 2 (YES in S14), the same as S4 to S7 in the first embodiment. Processes S15 to S18 are performed.

On the other hand, when the control unit 10 determines that the recording paper P does not exist at the toner image transfer position N by the image forming unit 2 (NO in S14), the control unit 10 forms the image by the image forming unit 2. The operation is stopped (S19). At this time, the control unit 10 also stops the main drive motor 9. That is, the control unit 10 stops the formation of a new toner image on the surface of the photosensitive drum 21 and stops the drum motor 8.

Then, the control unit 10 drives the main drive motor 9 to be next transported from the paper cassette 40 to the toner image transfer position N by the paper feed roller 41 and the transport roller pair 32 of the paper transport mechanism 3. A scheduled recording sheet P (hereinafter referred to as the next recording sheet P) is conveyed to the toner image transfer position N (S20). If there is a stopped recording paper P on the upstream side of the toner image transfer position, the recording paper P is conveyed to the toner image transfer position (S20).

The control unit 10 transports the next recording paper P to the toner image transfer position N, and then stops the main drive motor 9 to stop the transport of the next recording paper P to charge the image forming unit 2. The drum motor 8 is driven in a state where the unit 22, the exposure unit 23, and the developing unit 24 are stopped, and a toner removal operation for executing a transfer process by the transfer roller 25 is performed (S15). Thereafter, the processes of S16 to S18, which are the same processes as S5 to S7 in the first embodiment, are performed.

In the second embodiment, when the paper jam of the recording paper P is detected, even if the recording paper P is not present at the transfer position N, the control unit 10 transfers the next recording paper P to the transfer paper. The toner remaining untransferred on the surface of the photosensitive drum 21 is transferred to the next recording paper P that is transported to the position N by the paper feed roller 41 and the transport roller pair 32 and transported to the transfer position N. Even when the preceding recording paper P has already passed the transfer position N at the time of jam detection, the untransferred residual toner can be reliably removed from the surface of the photosensitive drum 21. Further, when the preceding recording paper P is located at the toner image transfer position N by the image forming unit 2 when the paper jam is detected, the toner removing operation is performed using the preceding recording paper P. By performing such a toner removal operation, when a jam is detected, a state where the residual toner on the surface of the photosensitive drum 21 can be transferred to the recording paper P is ensured, and the residual toner on the surface of the photosensitive drum 21 is surely removed. It becomes possible to do.

  Next, a third embodiment of toner removal processing when a paper jam is detected during continuous printing in the image forming apparatus 1 will be described. FIG. 5 is a flowchart illustrating a third embodiment of processing when a paper jam is detected during image formation in the image forming apparatus 1. The description of the same processing as that of the first embodiment shown in FIG. 3 or the second embodiment shown in FIG. 4 is omitted.

  In the third embodiment, the control unit 10 does not acquire a paper presence signal indicating that the recording paper P has been detected from the paper detection sensor 73 even after the predetermined time has elapsed (NO in S32). , S33: YES), it is determined whether there is a residual toner image on the surface of the photosensitive drum 21 (S34). Here, when the control unit 10 determines that there is a residual toner image on the surface of the photosensitive drum 21 (YES in S34), if the recording paper P exists at the transfer position N at this time (S35). If the recording paper P does not exist at the transfer position N at this time (NO at S35), the paper transport mechanism 3 moves the next recording paper P to the transfer position N. (S40, S41), and the toner removal operation is performed on the next recording paper P (S36 to S39).

  That is, when a paper jam is detected during the control of the continuous image forming operation, the control unit 10 does not transfer the toner image already formed on the surface of the photosensitive drum 21 to the recording paper P at this time. When it is determined that there is a toner, the paper transport mechanism 3 and the image forming unit 2 are caused to perform a toner removal operation.

On the other hand, when the paper jam is detected, the control unit 10 determines that the toner image is not formed on the surface of the photosensitive drum 21 or that the formed toner image has been transferred to the recording paper P (in S34). NO), the image forming unit 2 and the main drive motor 9 are stopped (S43), and the process is terminated. Thereafter, the process proceeds to control for setting a paper jam clearing standby state.

The control unit 10 determines whether or not there is a residual toner image on the surface of the photosensitive drum 21. When the paper jam of the recording paper P is detected by the paper detection sensor 73, the recording in which the paper jam is detected. When the image forming unit 2 is forming the toner image to be transferred onto the paper P, it is determined that there is a residual toner image on the surface of the photosensitive drum 21. Even when the image forming unit 2 has not started the formation of the toner image to be transferred to the recording paper P in which the paper jam is detected, the control unit 10 detects the next paper jam when the paper jam is detected. When the formation of the toner image to be transferred to P is started and it is determined that the peripheral surface portion on which the toner image is formed has not reached the toner image transfer position N, the toner image is formed on the surface of the photosensitive drum 21. It is determined that there is a residual toner image.

On the other hand, when the paper jam of the recording paper P is detected by the paper detection sensor 71, the control unit 10 detects that the peripheral surface portion on which the toner image to be transferred to the recording paper P where the paper jam is detected is the toner. If it is determined that the toner image passing through the image transfer position N and the toner image to be transferred to the next recording sheet P has not been formed, there is no residual toner image on the surface of the photosensitive drum 21, that is, the photosensitive It is determined that the toner image on the surface of the body drum 21 has already been transferred to the recording paper P.

According to the third embodiment, when a paper jam of the recording paper P is detected during the control of the continuous image forming operation, the toner image already formed on the surface of the photosensitive drum 21 at this time is detected. Is not transferred onto the recording paper P, that is, when there is a toner image remaining on the surface of the photosensitive drum 21, the toner removal operation is performed, and the toner image on the surface of the photosensitive drum 21 has already been recorded. When the toner image has been transferred to the paper P, the toner removal operation is not performed. Therefore, the toner removal operation is performed only when it is necessary to remove the residual toner image on the surface of the photosensitive drum 21, and the photosensitive member is removed. Wasteful operations that do not contribute to the removal of toner remaining on the surface of the drum 21 can be reduced.

In the third embodiment, in S35, if the recording paper P is not present at the transfer position N of the toner image by the image forming unit 2 (NO in S35), the control unit 10 reaches the transfer position N. Although the processing for causing the toner removal operation to be performed on the next recording paper P transported by the paper transport mechanism 3 is performed (S40, S41), the processing of S35, S40, S41 may be omitted.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the first to third embodiments, when the control unit 10 detects a paper jam in which the recording paper P does not reach the paper detection sensor 73 based on a paper no signal from the paper detection sensor 73, Although the toner removal operation is performed, the controller 10 detects the leading edge of the recording paper P based on the paper presence signal and the paper no signal from the paper detection sensor 73, and the predetermined time has elapsed. Alternatively, the toner removal operation may be performed when a paper jam that does not detect the trailing edge of the recording paper P is detected.

Further, in the first to third embodiments, the control unit 10 is disposed on the downstream side in the recording paper transport direction from the transfer position N of the toner image by the photosensitive drum 21 and the transfer roller 25. 72, or when a paper jam that does not reach the recording paper P reaches the paper detection sensor 72 or the paper detection sensor 74 based on a paper no signal from the paper detection sensor 74, or the control unit 10 detects the paper detection sensor 72. Alternatively, after detecting the leading edge of the recording paper P based on the paper presence signal and the paper non-signal from the paper detection sensor 74, a paper jam that does not detect the trailing edge of the recording paper P even after the predetermined time has elapsed. If detected, the toner removal operation may be performed. Since the reverse conveying path 312, in the path recording medium on which the toner image is transferred to one side at the transfer position N of the toner image has been performed is conveyed, is the downstream side in the transport direction of the recording paper, the paper detection sensor 74 This is also one of the paper detection sensors arranged downstream of the toner image transfer position N in the recording paper conveyance direction.

  Furthermore, in the first to third embodiments, the control unit 10 detects a paper jam by any one of the paper detection sensors 73, 72, and 74 regardless of which of the two types of jam detection described above. In this case, the toner removal operation may be performed.

  In each of the above embodiments, a printer is used as an embodiment of the image forming apparatus according to the present invention. However, this is only an example, and the image forming apparatus according to the present invention is a copy other than a printer. Other image forming apparatuses such as a multifunction machine having a plurality of functions such as a copying machine, a facsimile machine, a copying function, a facsimile function, a scanner function, and a printer function may be used.

  The configurations and processes shown in the above embodiments using FIGS. 1 to 5 are only one embodiment of the present invention, and are not intended to limit the present invention to the configurations and processes.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 21 Photosensitive drum 22 Charging part 23 Exposure part 24 Developing part 25 Transfer roller 3 Paper conveyance mechanism 31 Paper conveyance path 311 Main conveyance path 312 Reverse conveyance path 32 Conveyance roller pair 33 Registration roller pair 341 342 Switchback roller pair 4 Paper feed mechanism 40 Paper feed cassette 41 Paper feed roller 5 Fixing unit 8 Drum motor 9 Main drive motor 10 Control units 71, 72, 73, 74 Paper detection sensor 75 Registration sensor

Claims (3)

An image forming unit for forming an image by forming a toner image on the surface of the photosensitive drum and transferring the toner image to a recording medium;
A transport unit that transports the recording medium from a paper feed mechanism to a discharge unit of the recording medium through a transfer position of the toner image by the image forming unit;
The recording medium jam of the recording medium conveyed by the conveying unit, the recording medium jam detector for detecting in the conveying direction downstream side of the recording medium than the transfer position,
Continuous image formation comprising a transport operation by the transport unit that transports a plurality of the recording media to the transfer position in succession, and continuous image formation by the image forming unit for each of the continuously transported recording media. A control unit for controlling the operation;
A recording medium detection unit that detects whether or not there is the recording medium located at the transfer position;
The control unit is a case where the recording medium jam is detected by the recording medium jam detection unit during the control of the continuous image forming operation, and the recording medium is positioned at the transfer position by the recording medium detection unit. When it is detected that the recording medium is detected, the conveyance unit stops conveyance of each recording medium, and at this time, the toner image already formed on the surface of the photosensitive drum is positioned at the transfer position. A toner removing operation for transferring the image to the recording medium by the image forming unit ,
When the recording medium jam is detected by the recording medium jam detection unit during the control of the continuous image forming operation, the recording medium detection unit detects that the recording medium is not located at the transfer position. When this is done, the recording medium to be transported next is transported to the transfer position by the transport unit, and the toner image already formed on the surface of the photosensitive drum at this point is transported to the transported recording medium. the medium, the image forming apparatus Ru to perform the toner removal operation to transfer by the image forming unit. When the recording medium jam is detected by the recording medium jam detection unit during the control of the continuous image forming operation, the control unit forms a toner image already formed on the surface of the photosensitive drum at this time. Is determined to be untransferred to the recording medium, the toner removal operation is performed by the conveyance unit and the image forming unit, and the toner image on the surface of the photosensitive drum has been transferred to the recording medium. The image forming apparatus according to claim 1, wherein the toner removal operation is not performed by the conveyance unit and the image forming unit when the image forming unit determines that the toner removal operation is not performed. The image forming unit includes at least the photosensitive drum, a driving unit that rotationally drives the photosensitive drum, a charging unit, an exposure unit, a developing unit, and a transfer unit,
In the driving of the image forming unit during the toner removal operation, the control unit performs the rotation of the toner image already formed on the surface of the photosensitive drum by the rotation of the peripheral surface of the photosensitive drum toward the transfer position. to pass through a transfer position, the charging unit, the exposure unit, and said developing unit is stopped, the image forming apparatus according to claim 1 or claim 2 drives at least the drive unit and the transfer unit.