JP5287202B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Patent Document 1 discloses an intermediate transfer member, an intermediate transfer member cleaning unit, a transfer material charging unit, a transfer material separating unit from the intermediate transfer unit, a separation assisting unit, a separation unit in the event of a jam (paper jam) or the like. An image forming apparatus is disclosed in which a later-described transfer material guide means or the like has a unique safety mechanism that can cope with an accident.

JP 11-095627 A

  An object of the present invention is to prevent the upstream side of a transfer unit in a recording medium conveyance path from being soiled by an unfixed toner image on a recording medium.

The invention according to claim 1, by conveying while pressing in a heated state across the record medium Doo toner image has been transferred between a pair of rotary members, a fixing for fixing the toner image on the recording medium A pair of transport members provided upstream of the fixing unit in the recording medium transport path, the pair of transport members transporting the recording medium between the pair of transport members, A pair of conveying members is arranged between a conveying position where the recording medium is sandwiched by the pair of conveying members to convey the recording medium, and a separation position where the distance between the pair of conveying members is larger than the conveying position. When the image formation is stopped in a state in which the recording medium is sandwiched between the pair of rotating members of the fixing unit, the pair of rotating members is reversely rotated in the direction opposite to the normal direction. Rotation means; And when the image formation is stopped without the recording medium being sandwiched between the pair of rotating members of the fixing unit, the moving unit moves the pair of conveying members from the conveying position to the separated position. And when the image formation is stopped with the recording medium sandwiched between the pair of rotating members of the fixing unit, the moving unit does not move the pair of conveying members to the separated position. The image forming apparatus is characterized in that the image forming apparatus is maintained at the transport position .

According to a second aspect of the present invention, in the first aspect of the invention, the pair of transport members are a pair of rotating members included in the transfer unit, and the pair of rotating members perform image formation on the recording medium. , While the recording medium is rotated by sandwiching the recording medium by the pair of rotating members arranged at the transport position by the moving means, and the recording medium is transported, on the surface of one of the rotating members of the pair of rotating members The formed toner image is transferred to the surface of the recording medium sandwiched between the one rotating member and the other rotating member of the pair of rotating members, and the moving unit is configured to transfer the pair of fixing units to the pair of fixing units. When the image formation is stopped with the recording medium sandwiched between the rotating members, the moving unit maintains the transport position without moving the pair of rotating members of the transfer unit to the separated position. It allows the unfixed portion of the recording medium in accordance with the reverse rotation of the pair of rotary members in the fixing means is prevented from returning to the upstream side of the transfer unit, it is characterized in that.

According to a third aspect of the present invention, in the second aspect of the invention according to the second aspect, the second conveying means is provided upstream of the transfer means in the recording medium conveying path and conveys the recording medium with a pair of rotating members interposed therebetween. The pair of rotating members of the second conveying means, a conveying position for sandwiching the recording member by the pair of rotating members to convey the recording medium, and the pair of rotating members between the pair of rotating members. And a second moving means for moving the gap between the pair of rotating members of the fixing means so that the recording medium is not sandwiched between them. When the image formation is stopped in the state, the second moving unit moves the pair of rotating members of the second conveying unit from the conveying position to the separated position, and the pair of rotating members of the fixing unit. Between When the image formation is stopped with the recording medium being sandwiched, the second moving means does not move the pair of rotating members of the second conveying means to the separated position and remains in the conveying position. It is characterized by maintaining .

  According to a fourth aspect of the present invention, a toner image formed on a surface of one rotating member of the pair of rotating members is provided on the recording medium conveyance path, and the one rotating member is provided with the pair of rotating members. And a transfer means for transferring to the surface of the recording medium sandwiched between the rotation member and the other rotation member of the pair of rotation members, and provided on the downstream side of the transfer means in the recording medium conveyance path, and the toner image is transferred The recording medium is conveyed while being pressed while being sandwiched between a pair of rotating members, and a fixing unit that fixes the toner image to the recording medium, and when the image forming apparatus stops due to an abnormality, When a first recording medium is present between the transfer unit and the fixing unit, a gap between the pair of rotating members of the transfer unit is opened, and the first recording medium is moved along the recording medium conveyance path. Following the medium Continuing to convey the second recording medium to which the conveyed toner has not been transferred, so that the unfixed portion of the first recording medium downstream from the transfer means is covered with the second recording medium. And an image forming apparatus.

  According to the first aspect of the present invention, it is possible to prevent the upstream side of the transfer unit in the recording medium conveyance path from being soiled by an unfixed toner image on the recording medium.

  According to the invention of claim 2, in addition to the effect of the invention of claim 1, there is an effect that it is not necessary to add a special mechanism for gripping a recording medium having an unfixed portion.

  According to the third aspect of the present invention, even when the pair of rotating members of the transfer unit cannot obtain a holding force sufficient to stop the recording medium from reversing, the transfer unit and the conveying unit upstream of the transfer unit hold the holding force. The reversal of the recording means can be stopped with the combined force.

  According to the fourth aspect of the present invention, it is possible to prevent the upstream side of the transfer unit in the recording medium conveyance path from being soiled by an unfixed toner image on the recording medium.

  FIG. 1 schematically shows an example of the peripheral structure of a transfer unit and a fixing unit of an electrophotographic image forming apparatus to which the control of this embodiment is applied. FIG. 2 shows an example of a control mechanism for driving control around the transfer unit and the fixing unit in the illustrated image forming apparatus.

  In the illustrated example, a recording medium such as paper or a transparent sheet (hereinafter collectively referred to as “paper” for the sake of simplicity) 100 is transported through the paper transport path 10. A guide member and a pair of transport rolls are provided in the paper transport path 10 everywhere. The pair of transport rolls transports the paper by sandwiching the paper between the rolls and rotating. In the drawing, a pair of conveyance rolls 12a and 12b adjacent to the transfer unit 17 on the upstream side of the transfer unit 17 in the sheet conveyance path 10 is illustrated. The transport roll 12a rotates in the direction of the arrow in the figure and the transport roll 12b rotates in synchronization with the opposite direction, so that the paper 100 is transported in the transport direction (indicated by a white arrow in the figure), that is, toward the transfer unit 17. The Hereinafter, the direction in the transport direction is also referred to as “downstream side” as appropriate. The guide chute 14 is a guide plate that guides the conveyed paper 100 to enter the transfer unit 17. In one example, the pair of transport rolls 12a and 12b are latched by rotating in the forward direction indicated by the arrow in FIG. 1 by the driving force of a motor (not shown). The distance becomes smaller. On the other hand, for example, when the image forming apparatus stops due to the end of a job or an abnormality such as a paper jam, the transport roll pairs 12a and 12b rotate in the reverse direction. As a result, the latch is released, the distance between the transport roll pairs 12a and 12b is increased, and both rolls return to their home positions when not in operation (that is, when no job is being executed). It should be noted that the rotation drive for conveying the pair of conveyance rolls 12a and 12b and the latching and release of the conveyance roll pairs 12a and 12b may be operated by separate drive sources (motors). When the latches 12a and 12b are released, the rolls 12a and 12b do not rotate reversely. Such rotation in the forward and reverse directions of the transport roll pairs 12 a and 12 b is controlled by the transport roll driving unit 32 based on a command from the control unit 30. A job is a group of printing (copying) processes according to user instructions. For example, a process for executing a processing instruction designated by a print instruction (for example, an instruction for the number of print copies) indicated in input print data or a print or copy instruction input from an operation unit (not shown) It is.

  In this example, the transfer unit 17 includes an intermediate transfer belt 16, a pressure roll 18, and a transfer roll 20. That is, the transfer unit 17 is a part that performs secondary transfer of the intermediate transfer body type, and the toner image 120 transferred from the photoreceptor (not shown) to the intermediate transfer belt 16 is transferred to the pressure roll 18 and the transfer roll 20. Is transferred to the upper surface of the paper 100 by the potential difference and the pressing force. The pressure roll 18 rotates in the direction of the arrow shown in the figure, and the transfer roll 20 rotates in synchronization with the opposite direction, so that the paper 100 onto which the toner image 120 has been transferred is conveyed to the fixing unit 23 on the downstream side.

  In one example, the pressure roll 18 and the transfer roll 20 are latched by rotating in the forward direction indicated by an arrow in FIG. 1 by a driving force of a motor (not shown), and are pressed toward each other. Will fit. On the other hand, when the image forming apparatus stops due to, for example, the end of a job or a paper jam, the latch is released by rotating the pressure roll 18 and the transfer roll 20 in the opposite directions, and the pressure roll 18 and the transfer roll An interval of 20 is opened, and both rolls return to their home positions when not in operation. Such rotation of the pressure roll 18 and the transfer roll 20 in the forward and reverse directions is controlled by the transfer roll driving unit 34 based on a command from the control unit 30. It should be noted that the drive source (motor) for latching and releasing the pressure roll 18 and the transfer roll 20 may be different from the drive source for paper conveyance by these rolls. In this case, when the latching between the pressure roll 18 and the transfer roll 20 is released, the rolls do not rotate reversely.

  The fixing unit 23 includes a roll pair including a heating roll 22 and a pressure roll 24. During the fixing process, the heating roll 22 is heated to a temperature required for fixing by a heating means such as an internal halogen lamp. The pressure roll 24 is pressed toward the heating roll 22 during the fixing process. Thereby, the paper 100 sandwiched between both rolls is pressed. The paper toner image 120 sandwiched between the heating roll 22 and the pressure roll 24 is heated by the heating roll 22 and is pressed by the two rolls 22 and 24 to melt and fix to the paper. To do. The paper 100 after fixing is conveyed in the conveyance direction according to the rotation of the heating roll 22 and the pressure roll 24.

  The heating roll 22 and the pressure roll 24 are latched by rotating in the forward direction indicated by the arrow in FIG. 1 by the driving force of a motor (not shown), and are thereby pressed toward each other. On the other hand, when the image forming apparatus stops due to, for example, the end of a job or a paper jam, the heating roll 22 and the pressure roll 24 are rotated in the reverse direction to release the latch, and the heating roll 22 and the pressure roll The interval of 24 opens, and both rolls return to their home positions when not in operation. For example, if the heating roll 22 and the pressure roll 24 remain in contact with each other, the pressure roll 24 may be affected by heat, and thus such control is performed. The rotation of the heating roll 22 and the pressure roll 24 in the forward / reverse direction is controlled by the fixing roll driving unit 36 based on a command from the control unit 30.

  Further, a paper position sensor 26 (see FIG. 2) is provided in each part on the paper transport path 10. The sheet position sensor detects whether or not a sheet exists at the position of the sensor and outputs a signal indicating the detection result. The control unit 30 (see FIG. 2) recognizes the position of the sheet on the sheet conveyance path 10 based on the signal output from each sheet position sensor, and performs sheet conveyance control based on the recognized information. In FIG. 1, paper position sensors 26a and 26b before and after the transfer unit 17 are illustrated.

  FIG. 1 illustrates an intermediate transfer member type image forming apparatus, but the control of this embodiment can be applied to methods other than the intermediate transfer member method (for example, a method of directly transferring a toner image from a photosensitive member to a sheet). It is.

  In the image forming apparatus exemplified above, when the image forming apparatus is stopped due to an abnormality such as a paper jam, the heating roll 22 and the pressure roll 24 of the fixing unit 23 are in normal operation until then as described above. Rotates in the opposite direction. At this time, as shown in FIG. 1, if there is a portion of the toner image 120 transferred to the paper 100 that has not been fixed yet (the portion from the transfer portion 17 to the fixing portion 23 in FIG. 1), the heating roll In response to the reverse rotation of the pressure roller 22 and the pressure roll 24, the unfixed portion may go back up the paper conveyance path 10 and enter the upstream side of the transfer unit 17 (see FIG. 3). When this occurs, there is a possibility that members on the upstream side of the transfer unit 17, such as the guide chute 14 and the transport roll 12 a, will be contaminated by the toner in the unfixed portion.

  In order to avoid such a problem, in this embodiment, as illustrated in FIG. 4, when the image forming apparatus stops due to an abnormality such as a paper jam, the control unit 30 includes the transfer roll driving unit 34 and the transfer roll driving unit 34. By controlling the transport roll drive unit 32, the roll pair composed of the pressure roll 18 and the transfer roll 20 of the transfer unit 17 and the transport roll pair 12a and 12b adjacent to the upstream side are prevented from rotating in reverse. The sheet 100 is maintained in a state of being gripped by the roll pair including the pressure roll 18 and the transfer roll 20 and the transport roll pairs 12a and 12b. In this way, even if the roll pairs 22 and 24 of the fixing unit 23 rotate in the reverse direction, the unfixed portion of the paper 100 is bent between the transfer unit 17 and the fixing unit 23 as shown in FIG. There is no return to the upstream side of the part 17.

  If only the gripping force of the roll pairs 18 and 20 of the transfer unit 17 is sufficient to fix the paper 100 against the reverse rotation of the roll pairs 22 and 24 of the fixing unit 23, the transport roll pairs 12a and 12b are set. You may control to reverse and to return to the fixed position at the time of non-operation. Further, in the above example, the state of the roll pairs 18 and 20 and the transport roll pairs 12a and 12b of the transfer unit 17 is maintained at the time of operation, but the grip force of the roll pair (the pressing force toward the opposite roll) ) May be performed on one or both of the two roll pairs.

  FIG. 5 shows an example of a processing procedure executed by the control unit 30 in this embodiment. In this example, when the control unit 30 stops the image forming apparatus due to an abnormality such as a paper jam (S10), the vicinity of the transfer unit 17 and the fixing unit 23 is based on detection signals from the paper position sensors 26a and 26b. In step S12, it is determined whether the sheet 100 exists. For example, it may be determined whether there is a sheet between the transfer unit 17 and the fixing unit 23. If it is determined in step S12 that there is no paper 100, the controller 30 releases the pressurization state by rotating the pair of transport rolls 12a and 12b in the reverse direction and returns it to the home position during non-operation (as in the prior art). S14) Further, by rotating the roll pairs 22 and 24 of the fixing unit 23 in the reverse direction, the pressurized state is released to return to a fixed position during non-operation (S16).

  On the other hand, if it is determined in step S12 that the sheet 100 is present, the control unit 30 maintains the pressure state of the roll pairs 18 and 20 of the transfer unit 17 (or further increases the pressing force) (S18). The pressurized state of the transport roll pairs 12a and 12b is maintained (or the pressing force is further increased) (S20). Then, while maintaining this state, the roll pairs 22 and 24 of the fixing unit 23 are reversely rotated to release the pressure state of the roll pairs 22 and 24 and return to the fixed position during non-operation (S16). ). At this time, since the paper 100 is gripped at the positions of the roll pairs 18 and 20 of the transfer unit 17 and the positions of the transport roll pairs 12a and 12b, the reverse rotation of the roll pairs 22 and 24 of the fixing unit 23 causes reverse rotation of the paper 100. Even if the leading edge is returned to the upstream side, only the fixing portion of the sheet 100 is bent between the transfer portion 17 and the fixing portion 23 and does not return to the upstream side from the transfer portion 17.

  In the above example, when the image forming apparatus is abnormally stopped, the paper 100 is gripped by using the existing gripping mechanisms of the roll pairs 18 and 20 and the transport roll pairs 12a and 12b of the transfer unit 17, but instead of this, In addition, a dedicated gripping mechanism for gripping and fixing the paper 100 when the image forming apparatus stops abnormally may be provided. If this dedicated gripping mechanism is provided between the transfer unit 17 and the fixing unit 23, even if the roll pairs 18 and 20 of the transfer unit 17 are reversely rotated to return to a fixed position during non-operation during an abnormal stop, The unfixed portion 100 is prevented from returning to the upstream side of the transfer portion 17.

  Next, a second embodiment will be described. In the second embodiment, when the image forming apparatus is stopped due to an abnormality such as a paper jam, a succeeding sheet conveyed next to the sheet 100 on the sheet 100 being fixed as shown in FIG. 200 is sent in and covered.

  In this method, as shown in FIG. 7, when the control unit 30 stops the image forming apparatus in response to the occurrence of an abnormality such as a paper jam (Yes in S10), the transfer unit 17 and the fixing unit 23 are used. If there is a sheet in the vicinity (Yes in S12), before the reverse rotation (S16) of the roll pairs 22 and 24 of the fixing unit 23, and the upstream of the roll pairs 18 and 20 of the transfer unit 17 The distance between the transport roll pairs 12a and 12b is increased (S22, S24). The processes in steps S22 and S24 may be, for example, a process in which the roll pair is reversely rotated to return each roll included in the roll pair to a fixed position during non-operation, or from the case where the roll is in a fixed position during non-operation. Alternatively, a process that widens the interval between rolls may be used.

  Thereafter, the sheet 200 immediately after the sheet 100 currently being fixed is conveyed on the sheet conveyance path 10 (S26). In other words, before the image forming apparatus is stopped, a predetermined time sufficient for the succeeding paper 200 to cover the paper 100 for each of the transport roll pairs adjacent to the transfer unit 17 on the upstream side of the pair of transport rolls 12a and 12b. Just drive. As a result, the sheet on the upstream side of the sheet 100 is conveyed by a distance corresponding to the driving time. At this time, the conveyance roll pair (not including 12a and 12b) from the position of the subsequent sheet 200 to the conveyance roll pair 12a and 12b is determined from the signal of the sheet position sensor, and only these conveyance roll pair is driven. Also good.

  By such transport, the sheet 200 immediately after the sheet 100 is transported beyond the pair of transport rollers 12a and 12b and the transfer unit 17, and naturally covers the sheet 100 by the transport operation. In particular, as shown in FIG. 8, the sheet 200 descends from the upper side of the preceding sheet 100 toward the gap between the pair of conveying rolls 12a and 12b by the guide plate 28 on the upstream side of the conveying roll pair 12a and 12b. In the case of the carry route, the conveyed paper 200 is placed on the preceding paper 100. Not limited to such an example, various methods have been known in the past for placing a subsequent sheet on a preceding sheet, and such a conventional method may be used.

  Since the toner image is not transferred by the transfer unit 17, the upper surface of the paper 200 to be covered in this manner remains blank. This blank sheet surface covers a part (or all) of the upstream side of the unfixed portion of the sheet 100 as shown in FIG. Therefore, even if the roll pairs 22 and 24 of the fixing unit 23 are rotated in reverse in step S16, the unfixed portion of the paper 100 does not touch the members such as the guide chute 14 on the upstream side of the transfer unit 17, so Toner does not adhere.

FIG. 2 is a diagram schematically illustrating an example of a peripheral structure of a transfer unit and a fixing unit of an electrophotographic image forming apparatus to which the control of the embodiment is applied. FIG. 2 is a diagram illustrating an example of a control mechanism for driving control around a transfer unit and a fixing unit of an electrophotographic image forming apparatus to which the control of the embodiment is applied. It is a figure for demonstrating the problem of the conventional control. It is a figure for demonstrating control of embodiment. It is a figure which shows the example of the procedure of control of embodiment. It is a figure for demonstrating control of 2nd Embodiment. It is a figure which shows the example of the procedure of control of 2nd Embodiment. It is a figure for demonstrating control of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Paper conveyance path, 12a, 12b Conveyance roll, 14 Guide chute, 16 Intermediate transfer belt, 17 Transfer part, 18 Pressure roll, 20 Transfer roll, 22 Heating roll, 23 Fixing part, 24 Pressure roll, 26, 26a , 26b Paper position sensor, 28 guide plate, 30 control unit, 32 transport roll drive unit, 34 transfer roll drive unit, 36 fixing roll drive unit, 100 paper, 120 toner image, 200 paper.

Claims (4)

By preparative toner image is conveyed while pressed under heating in between the been record medium a pair of rotary members transfer, and fixing means for fixing the toner image on the recording medium,
A pair of conveying members provided upstream of the fixing unit in the recording medium conveying path, the pair of conveying members conveying the recording medium between the pair of conveying members;
Between the pair of transport members, a transport position where the recording medium is sandwiched by the pair of transport members to transport the recording medium, and a separation position where the distance between the pair of transport members is larger than the transport position. Moving means to move with,
Reverse rotation means for rotating the pair of rotation members in a direction opposite to normal when image formation is stopped in a state where the recording medium is sandwiched between the pair of rotation members of the fixing means;
Have
When image formation is stopped when the recording medium is not sandwiched between the pair of rotating members of the fixing unit, the moving unit moves the pair of conveying members from the conveying position to the separated position. ,
When the image formation is stopped with the recording medium being sandwiched between the pair of rotating members of the fixing unit, the moving unit does not move the pair of conveying members to the separated position. Keep it,
An image forming apparatus. The pair of conveying members are a pair of rotating members included in the transfer unit, and the pair of rotating members are arranged at the conveying position by the moving unit when the image is formed on the recording medium. The toner image formed on the surface of one rotating member of the pair of rotating members is transferred between the one rotating member and the pair of pairs while rotating the recording medium between the members and conveying the recording medium . Transfer to the surface of the recording medium sandwiched between the other rotating members of the rotating member,
When the image forming stops when the recording medium is sandwiched between the pair of rotating members of the fixing unit , the moving unit moves the pair of rotating members of the transfer unit to the separated position. By maintaining the transport position without moving to the position, it is possible to prevent the unfixed portion of the recording medium from returning to the upstream side from the transfer unit due to the reverse rotation of the pair of rotating members in the fixing unit. To
The image forming apparatus according to claim 1. A second conveying unit that is provided upstream of the transfer unit in the recording medium conveying path and conveys the recording medium with a pair of rotating members;
The pair of rotating members of the second conveying means, a conveying position where the recording member is sandwiched by the pair of rotating members to convey the recording medium, and a distance between the pair of rotating members than the conveying position Second moving means for moving between the open position and the separated position;
Further comprising
The second moving means includes
When image formation stops when the recording medium is not sandwiched between the pair of rotating members of the fixing unit, the second moving unit moves the pair of rotating members of the second conveying unit to the pair of rotating members. Move from the transfer position to the separation position,
When image formation is stopped while the recording medium is sandwiched between the pair of rotating members of the fixing unit, the second moving unit separates the pair of rotating members of the second conveying unit from the separation unit. Maintain the transport position without moving to a position,
The image forming apparatus according to claim 2. A toner image formed on the surface of one rotating member of the pair of rotating members is provided on the recording medium conveyance path, and the toner image formed on the surface of the rotating member of the pair of rotating members Transfer means for transferring to the surface of the recording medium sandwiched between the other rotating member,
The toner image is provided on the downstream side of the transfer unit in the recording medium conveyance path and conveyed while being pressed in a heated state with the recording medium onto which the toner image has been transferred being sandwiched between a pair of rotating members. Fixing means for fixing to the recording medium;
When the first recording medium exists between the transfer unit and the fixing unit when the image forming apparatus is stopped due to an abnormality, the interval between the pair of rotating members of the transfer unit is increased, and the recording is performed. Continuing to transport the second recording medium to which the toner that has been transported following the first recording medium on the medium transport path is not transferred, the undetermined downstream of the transfer means in the first recording medium. Control means for performing control so that the wearing portion is covered with the second recording medium;
An image forming apparatus comprising:

Images