JPH11184192A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively avoid such a failure that an image carrier with recording material sticking rushes into a cleaning means, and to facilitate the jamming processing of the recording material by detecting a situation that the recording material sticks to the image carrier positioned on the downstream side of a transfer part, restricting the movement of the recording material based on the detection information and also stopping the image carrier after a lapse of prescribed time. SOLUTION: When the recording material 4 sticks to the image carrier 1 while a transfer operation is executed by a transfer means 3, the presence of the recording material 4 on the image carrier 1 positioned on the downstream side of the transfer means 3 is detected by a means 5 for detecting the presence or absence of the recording material. Then, the recording material 4 feeding operation is restricted by the recording material restricting means 6 arranged on the upstream side of the transfer means 3 under the condition where the presence of the recording material 4 on the image carrier 1 is detected. The movement of the image carrier 1 is stopped by an image carrier stopping means 7 after a lapse of prescribed time in accordance with the restricting operation. In this state, the recording material 4 restricted/held by the recording material restricting means 6 is peeled from the moving image carrier 1, and then, easily removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, and more particularly to an image forming apparatus effective for a type in which a full-color image is collectively transferred to a recording material using an intermediate transfer member. Regarding improvement.

[0002]

2. Description of the Related Art In a conventional intermediate transfer type image forming apparatus, for example, a photosensitive member on which a toner image corresponding to an electrostatic latent image is formed and a toner image on the photosensitive member are transferred intermediately. An intermediate transfer belt, a primary transfer device for transferring the toner image on the photoconductor to the intermediate transfer belt, and a secondary transfer device for collectively and secondarily transferring the toner image on the intermediate transfer belt to paper. There is also known an apparatus provided with a paper position sensor (registration sensor) and a paper discharge sensor before secondary transfer to detect paper jam (for example, see Japanese Patent Application Laid-Open No. 5-323704).

[0003]

However, in this type of image forming apparatus, since the registration sensor and the paper ejection sensor detect the jam of the paper, the position of the paper registration sensor and the paper ejection sensor is changed. Although it is possible to grasp the paper jam at the time when the paper does not pass, if the paper sticks to the intermediate transfer belt, the paper is transferred to the intermediate transfer belt cleaner located downstream of the secondary transfer position of the intermediate transfer belt. , And there is a concern that the intermediate transfer belt cleaner or the intermediate transfer belt may be damaged, and that there is a technical problem that the jamming of the paper entering the intermediate transfer belt cleaner becomes troublesome. This is particularly due to the fact that, in an intermediate transfer type image forming apparatus, a large secondary transfer voltage is required in accordance with full colorization, and the paper is more likely to be attracted to the intermediate transfer belt by that amount. As the restriction on the paper used by the user is released, paper having various electric resistance values is handled, and there are many papers which are easily attracted to the intermediate transfer belt.

[0004] Such technical problems are remarkable in the intermediate transfer type image forming apparatus as described above.
This can also occur in an image forming apparatus of a type in which a toner image on a photoconductor is directly transferred to a sheet.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and an object of the present invention is to provide an image forming apparatus capable of effectively avoiding various problems caused by jamming of a recording material to a cleaner. .

[0006]

That is, the present invention provides:
As shown in FIG. 1, an image carrier 1 on which a visible image 2 such as a toner image is carried and conveyed, transfer means 3 for transferring the visible image 2 on the image carrier 1 to a recording material 4, A recording material presence / absence detection unit 5 for detecting the presence / absence of the recording material 4 on the image carrier 1 located downstream of the transfer unit 3; and a recording material presence / absence detection unit 5 provided upstream of the transfer unit 3 and The recording material constraining means 6 restricts the transport operation of the recording material 4 under the conditions in which it is detected that the recording material 4 remains on the image carrier 1, and the recording by the recording material constraining means 6 An image carrier stopping means 7 is provided which stops the movement of the image carrier 1 after a lapse of a predetermined time in conjunction with the restraining operation of the material 4.

In such technical means, an electrophotographic method, an electrostatic recording method, an ink jet recording method, or the like may be appropriately selected as an image forming method of the image forming apparatus which is an object of the present application. The image carrier 1 may be an image carrier having only a visible image 2 formed and carried thereon, such as a photoreceptor or a dielectric material. It is preferable to apply the present invention to a mold (an embodiment in which an intermediate transfer member is attached to one or a plurality of image forming carriers).

Further, the transfer means 3 also includes an image carrier 1
If it is a functional member for transferring the above visible image 2 to the recording material 4,
An electrostatic transfer method, a pressure transfer method, or the like may be appropriately selected. However, from the viewpoint of ensuring good transferability in a type in which the visible image 2 is formed by charged particles such as toner, the electrostatic transfer method is preferred. preferable. Here, examples of the electrostatic transfer method include a contact bias method that includes a transfer member such as a roll that is disposed in contact with the image carrier 1 and performs a transfer process using a transfer electric field by a transfer bias. A non-contact bias method using a corona discharge or the like that is arranged in a non-contact manner may be selected as appropriate.However, in a type such as an intermediate transfer type that requires a high transfer bias during the secondary transfer, a contact It is preferable to adopt a bias method.

The recording material presence / absence detecting means 5 is a surface potential sensor (for example, an ESV) capable of measuring the charged potential on the image carrier 1 as long as it can detect the presence / absence of the recording material 4.
[Electrostatic Voltmeter]), or a device for sandwiching the image carrier 1 from the front and back of the image carrier 1 to detect the resistance of the image carrier 1 or disposing a distance sensor to the image carrier 1 The distance to the image carrier 1 is always recognized, and the presence or absence of the recording material 4 is detected based on the difference in the distance in a state where the recording material 4 is stuck to the image carrier 1. A reflective photo sensor is arranged for
An appropriate selection may be made, for example, by detecting the shadow of the leading end of the recording material 4 attached to the image carrier 1 and detecting the presence or absence of the recording material 4. In this case, from the viewpoint of effectively suppressing the increase in the apparatus cost, the recording material presence / absence detecting means 5
It is preferable to use an existing device. For example, if a surface potential sensor has already been used to control the charging potential of the image carrier 1 such as an intermediate transfer member, an existing surface potential sensor may be used as the recording material presence / absence detecting means 5. Good. When the image carrier 1 such as an intermediate transfer member is a belt having a seam, for example, the potential of the seam, the electric resistance, the distance, etc. are recognized, and the recording material 4 is used as the image carrier. It is preferable to provide a threshold value so as to distinguish (separate) from the state stuck to 1.

Further, as long as the recording material restraining means 6 is a functional member whose transporting operation of the recording material 4 is restricted based on information detected by the recording material presence / absence detecting means 5, the recording material 4 can be pinched as necessary. It may be appropriately selected, for example, by stopping, but from the viewpoint of effectively suppressing an increase in apparatus cost, it is preferable to use an existing device. Here, as an aspect in which an existing device is used as the recording material restraining means 6, a positioning roll for positioning and transporting the recording material 4 is also used. The positioning roll is used to pinch and convey the recording material 4. If the drive is stopped, the positioning roll becomes a functional member that prevents the recording material 4 from moving while holding the recording material 4.

Furthermore, in order to ensure that the recording material 4 is restrained by the recording material restraining means 6, the distance between the recording material presence detecting portion of the recording material presence detecting means 5 and the recording material restraining means 6 (the recording material restraining means 6). A recording material capable of transporting the distance from the restraining means 6 to, for example, the transfer nip area exit of the transfer means 3 plus the distance on the image carrier 1 from the transfer nip area exit to the recording material presence / absence detection site) What is necessary is just to set shorter than the dimension length of No. 4.

Further, the image carrier stopping means 7 may be configured to stop the movement of the image carrier 1 when a predetermined time has elapsed after the recording material 4 is restrained by the recording material restraining means 6. Good. At this time, the stop timing of the image carrier 1 may be arbitrarily set, but from the viewpoint of effectively preventing the visible image 2 on the image carrier 1 from dropping and scattering, the transfer unit 3 In the type provided with a cleaning means 9 for cleaning the residue on the image carrier 1 on the downstream side of the image carrier 1, the image carrier 1
It is preferable that the image carrier 1 be stopped after a predetermined time has passed when the upper visible image forming area passes through the cleaning unit 9.

Further, regarding the stop timing of the image carrier 1, from the viewpoint of effectively avoiding the sticking of the recording material 4 to the image carrier 1, the stop of the image carrier 1 by the image carrier stopping means 7. Before the operation is performed, it is preferable to include an abnormal-time transfer processing unit 8 in which the transfer operation capability of the transfer unit 3 is reduced. For example, as an example of a type in which the transfer unit 3 is placed in contact with the image carrier 1 and performs a transfer process with a transfer electric field by an applied bias, as a unit for lowering the transfer operation capability, the transfer electric field itself by the transfer unit 3 is used. The transfer means 3 may be appropriately selected, for example, by reducing the transfer means 3 or by arranging the transfer means 3 apart from the visible image carrying surface of the image carrier 1. Here, reducing the transfer electric field may be lower than the electric field necessary for the transfer process, and includes not only the zero mode but also the electric field of the opposite polarity.

In particular, in a type in which the transfer means 3 is arranged in contact with the image carrier 1 and performs a transfer process by a transfer electric field by an applied bias, sticking of the recording material 4 to the image carrier 1 is more reliably avoided. From this viewpoint, before the image carrier 1 is stopped by the image carrier stopping means 7, the transfer electric field by the transfer means 3 is reduced and the transfer means is moved from the visible image carrying surface of the image carrier 1 to the transfer means. It is preferable to include an abnormal-time transfer processing unit 8 in which the reference numeral 3 is disposed separately.
In this embodiment, the recording material 4 is hardly electrostatically attracted to the image carrier 1 and hardly adheres under pressure, and the effect of preventing the recording material 4 from sticking to the image carrier 1 is great.

Further, when the positional relationship between the recording material presence / absence detecting means 5 and the cleaning means 9 is close to each other due to the layout, the image carrier 1 is stopped by the image carrier stopping means 7. However, there may be a mode in which the leading end of the recording material 4 enters the cleaning unit 9. In such a mode, from the viewpoint of facilitating removal of the recording material 4 that has entered the cleaning unit 9, the image carrier 1 is stopped before the image carrier 1 is stopped by the image carrier stopping unit 7. Cleaning means 9 from the visible image bearing surface of carrier 1
It is preferable to provide an abnormal-time cleaning processing unit 10 for temporarily retreating the apparatus.

Next, the operation of the above technical means will be described. Assuming that the recording material 4 adheres to the image carrier 1 such as an intermediate transfer body during the transfer operation by the transfer means 3 as indicated by a two-dot chain line in FIG. It is detected that the recording material 4 is present on the image carrier 1 located on the downstream side, and it is surely grasped that the recording material 4 is stuck on the image carrier 1. Then, the recording material restraining means 6 arranged on the upstream side of the transfer means 3 operates under the condition that the recording material presence / absence detecting means 5 detects that the recording material 4 remains on the image carrier 1. In addition, the conveyance operation of the recording material 4 is restricted. Further, the image carrier stopping means 7 stops the movement of the image carrier 1 after a lapse of a predetermined time in conjunction with the restraining operation of the recording material 4 by the recording material restraining means 6. In this state, the recording material 4 restrained and held by the recording material restraining means 6 is separated from the moving image carrier 1, and the recording material 4 stuck on the image carrier 1 is easily removed.

Further, in the case where the abnormal-time transfer processing means 8 is provided, the abnormal-time transfer processing means 8 transfers the transfer means before the image carrier 1 stopping operation by the image carrier stopping means 7 is performed. Since the transfer operation capability of the recording material 4 is reduced, the force of sticking the recording material 4 to the image carrier 1 is reduced. On the other hand, in the mode in which the abnormal-time cleaning processing unit 10 is provided, the abnormal-time cleaning processing unit 10 can remove the image carrier before the image carrier 1 stopping operation by the image carrier stopping unit 7 is performed. In order to temporarily retreat the cleaning unit 9 from the visual image holding surface, even if the leading end of the recording material 4 enters the cleaning unit 9, a jam occurs while the leading end of the recording material 4 enters the cleaning unit 9. No, it is easily dropped and removed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a schematic configuration of a color image forming apparatus (a color electrophotographic copying machine in the present embodiment) to which the present invention is applied. In FIG. 1, reference numeral 11 denotes a photosensitive drum (latent image carrier), and the surface thereof is charged with a charging device 12 and a well-known electronic device such as an exposure device 13 such as a laser scanning scanner as it rotates in the direction of arrow A. An electrostatic latent image corresponding to the image information is formed by a photographic process. Around the photosensitive drum 11, developing devices 14a corresponding to the colors of black (Bk), yellow (Y), magenta (M), and cyan (C) are provided.
, A rotary developing device 14 mounted thereon is provided, and the electrostatic latent image formed on the photosensitive drum 11 is developed by one of the developing devices 14a to 14d to form a toner image T. ing. Further, reference numeral 15 denotes a pre-transfer charging device for processing the toner images T of the respective colors on the photoconductor drum 11 so as to be easily transferred, 16 denotes a static eliminator for removing residual toner charges on the photoconductor drum 11 after transfer, and 17 denotes a photoconductor. Drum 11
It is a drum cleaner for removing the upper residual toner.

Reference numeral 20 denotes an intermediate transfer belt disposed so as to be in contact with the surface of the photosensitive drum 11;
A plurality (in the present embodiment) of five rolls 21 to 25 are stretched and rotated in the arrow B direction. Here, in the present embodiment, reference numeral 21 denotes the intermediate transfer belt 20.
Is a tension roll for controlling the tension of the intermediate transfer belt 20 to be constant, 23 and 24 are driven rolls, 25 is an opposing roll (back-up roll) for secondary transfer, and the drive roll 21 Is driven by a drive motor 31 (see FIG. 3), for example. In the present embodiment, the intermediate transfer belt 20 has a volume resistivity of 10 ⁶ to 10 by adding an appropriate amount of carbon black or the like to a resin such as polyimide, polycarbonate, polyester, polypropylene, or polyethylene terephthalate or various rubbers. ^It is formed to be ¹⁵ Ω · cm, and its thickness is set to, for example, 0.1 mm.

Further, at a portion (primary transfer position) of the intermediate transfer belt 20 opposed to the photosensitive drum 11, a primary transfer device (primary transfer roll in the present embodiment) 18 is disposed on the back side of the intermediate transfer belt 20. The toner image T on the photosensitive drum 11 is electrostatically attracted to the intermediate transfer belt 20 by applying a voltage having a polarity opposite to the charge polarity of the toner to the primary transfer roll 18. I have.

Further, a secondary transfer device 40 is provided at a secondary transfer position of the intermediate transfer belt 20 facing the conveyance path of the sheet P as a recording material. And a counter roll (back-up roll) 25 disposed on the back side of the intermediate transfer belt 20 and serving as a counter electrode of the secondary transfer roll 26. I have. And
In the present embodiment, the secondary transfer roll 26 is grounded, and a bias having the same polarity as the charged polarity of the toner is stably applied to the backup roll 25 via the power supply roll 27. Further, a roll cleaner 28 having a cleaning blade 28a made of, for example, urethane rubber is attached to the secondary transfer roll 26. The secondary transfer roll 26 and the roll cleaner 28 are moved by a transfer retract mechanism 29 (see FIG. 3). It moves forward and backward between a transfer position that is in pressure contact with the intermediate transfer belt 20 and a standby position that is separated from the transfer position.

In the present embodiment, as the backup roll 25, a two-layered EPDM in which a foamed elastic material layer and an outer conductive layer are coated on the outer periphery of a metal core material is used. The outer conductive layer is a semiconductive EPDM (ethylene propylene diene rubber) foam rubber in which carbon black is dispersed at 15 to 35% by weight, and the thickness of the surface layer is 0.5 to 1.5.
mm. Surface resistivity is 10 ⁷ to 10 ¹⁰ Ω
/ □ is controlled in the resistance region. Also, the secondary transfer roll 2
Reference numeral 6 denotes a core layer made of a carbon black-dispersed foamed EPDM material fixed around the core, coated with a carbon black-dispersed fluororesin-based material having a thickness of 5 to 20 μm via a skin layer. the volume resistivity of the coating layer becomes 10 ⁴ [Omega] cm to 10 ⁶ [Omega] cm, roll hardness is 45 ° to 20 ° in Asker C hardness.

Further, a belt cleaner 41 for removing residual toner on the intermediate transfer belt 20 is provided downstream of the secondary transfer device 40. The belt cleaner 41 moves forward and backward between a cleaning position where the belt cleaner 41 is pressed against the intermediate transfer belt 20 via a cleaner retract mechanism 42 and a standby position where the belt cleaner 41 is separated from the cleaning position.

Further, in the present embodiment, the paper transport system sends out the paper P from the paper tray 50 by a feed roll 51, transports the paper P by a transport roll 52, and temporarily sends it by a registration roll (registration roll) 53. After the positioning is stopped, the sheet P is fed to the secondary transfer position via the guide chute 54 at a predetermined timing, and the sheet P after the secondary transfer is transferred to the sheet transport guide 5.
5 to the transport belt 56, and the transport belt 5
6 to the fixing device 57,
Through a discharge tray (not shown).

In particular, in the present embodiment, the jam control system 100 for preventing the paper P from jamming on the belt cleaner 41.
Is provided. Jam processing system 1 according to the present embodiment
3, a surface potential sensor 101 for detecting the surface potential of the intermediate transfer belt 20 is provided on the downstream side of the secondary transfer device 40 of the intermediate transfer belt 20 and on the upstream side of the belt cleaner 41, as shown in FIG. The belt 20 is disposed so as to face the surface (toner image carrying surface) of the belt 20. Here, as the surface potential sensor 101, for example, an ESV (Electrostatic Volt
meter) is used, and in this embodiment, usually,
The potential of the surface of the intermediate transfer belt 20 is monitored, and is used to control, for example, development conditions and transfer conditions. Paper presence sensor (POB
(Paper On Belt) jam sensor).

Further, in the present embodiment, a registration sensor (registration sensor) 102 is disposed in front of the registration roll 53 on the entrance side, and a sheet conveyance guide downstream of the secondary transfer device 40 is provided. A post-transfer sensor 103 is provided near 55.

The detection signals from the surface potential sensor (POB jam sensor) 101, the registration sensor 102, and the post-transfer sensor 103 are input to the control device 104. The control device 104 is generally constituted by a microcomputer system, and basically executes a series of image forming programs, executes a jam control processing program shown in FIG.
1. A predetermined control signal is transmitted to the registration roll 53, the primary transfer device 18, the secondary transfer device 40, the belt cleaner 41, and the like. Incidentally, in FIG.
1 indicates a primary transfer bias, and 152 indicates a secondary transfer bias.

In this embodiment, the distance d1 from the nip area of the registration roll 53 to the exit of the nip area of the secondary transfer device 40 and the intermediate transfer of the jam sensor 101 from the nip area exit of the secondary transfer apparatus 40 The sum d with the distance d2 to the detection position on the belt 20 is shorter (for example, about 1) than the minimum paper size (postcard size in the present embodiment).
40 mm).

Next, an image forming process of the color image forming apparatus according to the present embodiment will be described. Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed. Specifically, the photosensitive drum 11
If the electrostatic latent image written on the photosensitive drum 1 corresponds to, for example, yellow image information, the electrostatic latent image is developed by the developing device 14b containing yellow (Y) toner.
1 is formed with a yellow toner image T. The unfixed toner image T formed on the photoconductor drum 11 is transferred from the photoconductor drum 11 to the surface of the intermediate transfer belt 20 at a primary transfer position where the photoconductor drum 11 and the intermediate transfer belt 20 are in contact.

At this time, when forming a monochromatic image,
The toner image T primarily transferred to the intermediate transfer belt 20 is secondarily transferred to the sheet P immediately. When a color image in which toner images of a plurality of colors are overlapped is formed, the toner image T on the photosensitive drum 11 is formed. Formation of toner image and toner image T
Is repeated by the number of colors. For example, 4
When a full-color image is formed by superimposing color toner images, black, yellow, magenta, and cyan toner images T are formed on the photosensitive drum 11 for each rotation, and these toner images T are sequentially formed. The primary transfer is performed on the intermediate transfer belt 20. On the other hand, the intermediate transfer belt 20 rotates at the same cycle as the photosensitive drum 11 while holding the black toner image T that has been primarily transferred first, and the yellow, magenta and The cyan toner image T is transferred.

The toner image T primarily transferred onto the intermediate transfer belt 20 in this manner is conveyed to a secondary transfer position as the intermediate transfer belt 20 rotates. On the other hand, the paper P is supplied to the secondary transfer position at a predetermined timing by the registration roll 53, and the secondary transfer roll 26 nips the paper P with respect to the backup roll 25. Then, at the secondary transfer position, the secondary transfer roll 26 as the secondary transfer device 40
Of the toner image T carried on the intermediate transfer belt 20 by the action of the transfer electric field formed between
Is electrostatically transferred to the sheet P at the secondary transfer position. still,
When a color image is formed, these members are separated from the intermediate transfer belt 20 until the toner image T before the final color passes through the secondary transfer roll 26 and the belt cleaner 41. Thereafter, the paper P on which the secondary transfer has been performed is transferred to the transport belt 56.
Is carried to the fixing device 57 through which the toner image T on the sheet P is fixed. The intermediate transfer belt 20 on which the secondary transfer of the toner image has been completed removes residual toner by the belt cleaner 41.

In such an image forming process, the paper P
When the sheet P is guided to the fixing device 57 side, the sheet P passes through the registration sensor 102 and then passes through the post-transfer sensor 103, during which time the surface potential sensor 101 does not show a rapid change. For this reason, the control device 104 controls the potential monitor (for example, the intermediate transfer belt 2) from the surface potential sensor 101.
A series of image forming processes is executed while controlling development conditions, transfer conditions, and the like based on the change by the surface potential monitor (0).

On the other hand, as shown in FIG. 5, if the sheet P after the secondary transfer (indicated by a thick dotted line in FIG. 5) is stuck to the intermediate transfer belt 20, a surface potential sensor (POB)
The potential monitor of the jam sensor 101 fluctuates greatly. Note that, in FIG. 5, a symbol T indicates a toner image. The control device 104 catches the output fluctuation from the POB jam sensor 101 and immediately recognizes that the sheet P is stuck on the intermediate transfer belt 20 (step 1 in FIG. 4 (hereinafter abbreviated as ST) 1). Then, the control device 104 determines in FIG.
As shown in FIG. 6, the driving of the registration roll 53 is urgently stopped, and the advance of the sheet P is stopped while the sheet P is held therebetween. In this state, since the intermediate transfer belt 20 is still in the operating state, the sheet P is easily separated from the intermediate transfer belt 20.

Thereafter, the control device 104 turns off the bias (the bias applied from the backup roll 25 in the present embodiment) 152 of the secondary transfer roll 26, as shown in FIG. At the same time, the secondary transfer roll 26 is retracted from the intermediate transfer belt 20 to the standby position by the transfer retract mechanism 29. At this time, since the transfer electric field does not act on the sheet P at the secondary transfer portion, the electrostatic attraction force to the intermediate transfer belt 20 does not act on the sheet P, and the amount of the secondary transfer roll 26 retracted is reduced. Therefore, the leading end portion of the sheet P easily falls.

Further, as shown in FIG. 4 ST 4 and FIG. 8, the controller 104 retracts the belt cleaner 41 from the intermediate transfer belt 20 to the standby position by the cleaner retract mechanism 42. By doing so, temporarily the paper P
Even if the leading end of the paper P enters the belt cleaner 41, the penetrated paper P is easily removed, and the leading end of the paper P easily falls because the belt cleaner 41 is retracted.

After that, the control device 104 determines in FIG.
As shown in FIGS. 6 and 9, by sending a stop signal to the drive motor 31, the drive of the intermediate transfer belt 20 is stopped, and the nip between the registration roll 53 and the transport roll 52 is released. Even if a stop signal is input to the intermediate transfer belt 20, there is an idle running distance of about 30 mm. Therefore, even if the drive of the intermediate transfer belt 20 is stopped immediately after the drive of the registration roll 53 is stopped, The sheet P adsorbed on the intermediate transfer belt 20 is peeled off, and the leading end of the sheet P falls. Accordingly, in this state, the jammed paper P is completely peeled off from the intermediate transfer belt 20, and
Since the leading end of the sheet P is falling, the operation of removing the jammed sheet P is easily performed.

Further, as shown in FIG. 4 ST7, the control device 104 controls the surface potential sensor (POB jam sensor) 10
It recognizes that the jammed paper P has been removed based on the signal change of the registration sensor 1 and the registration sensor 102, and ends a series of jam control processing.

Embodiment 2 FIG. 10 is a flowchart showing the processing contents of the jam control system used in Embodiment 2. In the figure, the control device 104 has substantially the same processing steps (ST1 to ST7) as in the first embodiment, but differs from the first embodiment in that the bias of the secondary transfer roll 26 is turned off and the intermediate transfer is performed. Between the step of retracting the secondary transfer roll 26 from the belt 20 (ST3) and the step of retracting the belt cleaner (ST4), the intermediate transfer belt 2
Step of Cleaning Residual Toner on ST0 (ST)
8).

Therefore, according to the present embodiment, as shown in FIG. 11, if the paper P after secondary transfer (indicated by a thick dotted line in FIG. 11) is stuck to the intermediate transfer belt 20, the control device 104 captures the output fluctuation from the POB jam sensor 101 and immediately recognizes that the paper P has stuck on the intermediate transfer belt 20 (FIG. 10ST1), and FIG.
As shown in FIG. 12 and FIG. 12, the driving of the registration roll 53 is urgently stopped, and the bias 152 of the secondary transfer roll 26 is turned off as shown in FIG. 10 ST3 and FIG. The secondary transfer roll 26 is retracted from the intermediate transfer belt 20 to the standby position.

After that, the control device 104 returns to ST8 of FIG.
As shown in FIG. 14, the residual toner T on the intermediate transfer belt 20 is cleaned by the belt cleaner 41.
Further, as shown in FIGS. 10ST4 and 15, the controller 104 retracts the belt cleaner 41 from the intermediate transfer belt 20 to the standby position by the cleaner retract mechanism 42, and thereafter, shown in FIGS. 10ST5 and 6 and FIG. 16. As described above, the drive of the intermediate transfer belt 20 is stopped by sending the stop signal to the drive motor 31, and the nip between the registration roll 53 and the transport roll 52 is released.

In this state, when the jam sheet P is removed, in the present embodiment, the intermediate transfer belt 2
Since there is no residual toner T on the intermediate transfer belt 20, dropping of toner on the intermediate transfer belt 20 and scattering of toner, which may occur at the time of removing the jammed paper P, are effectively prevented. Then, when the operation of removing the jammed paper P is completed, the control device 104 ends a series of jam control processing via ST7 in FIG.

Third Embodiment FIG. 17 shows a color image forming apparatus according to a third embodiment. The color image forming apparatus according to the present embodiment is different from the intermediate transfer method according to the first and second embodiments in that toner images are formed on a photoconductor in a required number of colors in a state of being stacked on each other. This is an example in which the present invention is applied to a type in which toner images of a required number of colors formed on a sheet are collectively transferred onto paper.

In the figure, reference numeral 81 denotes a photosensitive belt of an organic photosensitive member having an insulating surface coat layer, and reference numeral 82 denotes a charger composed of, for example, a scorotron. A DC power supply is connected to a corona discharge wire. Reference numeral 83 denotes an exposure beam emitted from an exposure device such as a laser scanning device to the photosensitive belt 81, and reference numerals 84 to 87 denote yellow (Y), magenta (M), cyan (C), and black (Bk) toners, respectively. A developing device included separately, 88 is a transfer device for transferring the toner image on the photosensitive belt 81 to the paper P, and 89 is a belt cleaner for removing toner remaining on the photosensitive belt 81 after the transfer process. .

In this embodiment, the photoreceptor belt 81 is stretched around four rolls 91 to 94 and rotates in the direction of arrow B. Here, reference numeral 91 denotes a drive roll of the photoreceptor belt 81, 92 denotes a driven roll, 93 denotes a tension roll for controlling the tension of the photoreceptor belt 81 to a constant value, and 94 denotes a facing roll which constitutes one element of the transfer device 88. (Backup roll).

In this embodiment, the transfer device 8
8 is a photoreceptor belt 81 substantially similar to the first and second embodiments.
Transfer roll 95 pressed against the toner image bearing surface of the transfer roller 95
And a counter roll (backup roll) 94 disposed on the back side of the photoreceptor belt 81 and serving as a counter electrode of the transfer roll 95. In this embodiment, the transfer roll 95 is grounded, and the backup roll 9
A bias power supply (not shown) is connected to 4. The transfer roll 95 is provided with a cleaning blade 98 made of, for example, urethane rubber.

Further, in the present embodiment, the photosensitive belt 8
A surface potential sensor 101 also serving as a POB jam sensor is provided downstream of the first transfer device 88 and upstream of the belt cleaner 89, and a jam control system (not shown) substantially similar to the first embodiment. The control device (not shown) of the jam control system executes, for example, a jam processing control program shown in FIG.

Next, an image forming process of the color image forming apparatus according to the present embodiment will be described. First, first
As a cycle, the photosensitive belt 81 is uniformly charged by applying a DC bias to the grid of the charger 82. Thereafter, a first image exposure is performed by an exposure device (not shown) to form an image latent image. Then, a developing bias is applied to the yellow developing device 84 to cause the yellow developing device 84 to adhere to the photoreceptor belt 81. Subsequently, the second cycle is started, and the photoreceptor belt 81 is
2 uniformly charges. Thereafter, a second image exposure is performed by an exposure device to form an image latent image, a developing bias is applied to a magenta developing device 85, and magenta toner is adhered onto the photoreceptor belt 81. The above steps are repeated to form cyan and black images.

Thereafter, the toner adhering to the photoreceptor belt 81 is collectively transferred to the paper P by using the transfer device 88.
In particular, in the present image forming process, the photosensitive belt 8
1 is rotated a plurality of times, and a plurality of color toner images are formed on the photoreceptor belt 81 so that a toner image before the final color is formed on the photoreceptor belt 81. The transfer roll 95 and the belt cleaner 89 are spaced apart from the photosensitive belt 81 until they pass through the belt cleaner 89. Immediately before the transfer operation is performed, the transfer roll 95 is placed in contact with the photosensitive belt 81 and The transfer operation is performed when the paper P from the tray 50 is sent to the transfer position of the photosensitive belt 81 at a predetermined timing, and the residual toner on the photosensitive belt 81 after the transfer is brought into contact with the timing. It is cleaned by the belt cleaner 89.

In this embodiment, if the sheet P after the batch transfer is stuck to the photoreceptor belt 81, the output of the surface potential sensor (POB jam sensor) 101 changes to the "sheet present" level. I do. As shown in FIG. 18, a control device (not shown) captures this change, recognizes that the paper P has adhered to the photoreceptor belt 81, and drives the registration roll 53 first, substantially in the same manner as in the first embodiment. After the stop, the bias of the transfer roll 95 is turned off, and the transfer roll 95 is retracted from the photoreceptor belt 81.
The belt cleaner 89 is retracted, and thereafter, the driving of the photosensitive belt 81 is stopped, the nip of the registration roll 53 is released, and it is finally checked whether or not the jammed sheet P has been removed. If you do this,
Also in the present embodiment, the sheet is reliably removed from the photoreceptor belt 81. In the present embodiment, ST
As shown by the dotted line in FIG. 18, a step (ST8) for cleaning the residual toner on the photoreceptor belt 81 is added between ST3 and ST4, and the jam control process substantially similar to that of the second embodiment is performed. Needless to say, this may be done.

[0050]

As described above, according to the present invention,
A state in which the recording material is stuck on the image carrier positioned downstream of the transfer portion by the transfer unit is detected, and based on this detection information, the movement of the recording material is restricted, and the restraining operation of the recording material is performed. Since the image carrier is stopped after a predetermined period of time in conjunction therewith, the recording material adhered to the image carrier can be reliably peeled off. For this reason, it is possible to effectively avoid a situation in which the recording material adheres to the image carrier and enters into, for example, a cleaning unit located on the downstream side, and the damage to the cleaning unit or the image carrier can be effectively avoided. In addition, it is possible to easily perform the jam processing of the recording material, thereby improving the reliability of the apparatus.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an outline of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating an outline of the image forming apparatus according to the first embodiment;

FIG. 3 is an explanatory diagram showing a jam control system used in the first embodiment.

FIG. 4 is a flowchart showing processing contents of a jam control system shown in FIG. 3;

FIG. 5 is an explanatory diagram showing an operation example of a jam processing system used in the first embodiment.

FIG. 6 is an explanatory diagram showing an operation example of a jam processing system used in the first embodiment.

FIG. 7 is an explanatory diagram showing an operation example of a jam processing system used in the first embodiment.

FIG. 8 is an explanatory diagram showing an operation example of a jam processing system used in the first embodiment.

FIG. 9 is an explanatory diagram illustrating an operation example of a jam processing system used in the first embodiment.

FIG. 10 is a flowchart showing processing contents of a jam control system used in the second embodiment.

FIG. 11 is an explanatory diagram showing an operation example of a jam processing system used in the second embodiment.

FIG. 12 is an explanatory diagram showing an operation example of a jam processing system used in the second embodiment.

FIG. 13 is an explanatory diagram showing an operation example of a jam processing system used in the second embodiment.

FIG. 14 is an explanatory diagram illustrating an operation example of a jam processing system used in the second embodiment.

FIG. 15 is an explanatory diagram showing an operation example of a jam processing system used in the second embodiment.

FIG. 16 is an explanatory diagram showing an operation example of a jam processing system used in the second embodiment.

FIG. 17 is an explanatory diagram illustrating an outline of an image forming apparatus according to a third embodiment;

FIG. 18 is a flowchart showing processing contents of a jam control system used in the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Visible image, 3 ... Transfer means, 4 ... Recording material, 5 ... Recording material presence detection means, 6 ... Recording material restraining means, 7
... Image carrier stopping means, 8 transfer processing means at abnormal time, 9 cleaning means, 10 cleaning processing means at abnormal time

Claims (7)

[Claims] An image carrier on which a visible image is carried and conveyed; a transfer unit for transferring the visible image on the image carrier to a recording material; and an image carrier on a downstream side of the transfer unit. A recording material presence / absence detection means for detecting the presence / absence of the recording material, and a recording material presence / absence detection means disposed upstream of the transfer means and detecting that the recording material remains on the image carrier. A recording material constraining means for constraining the recording material conveyance operation under the conditions described above, and interlocking with the recording material constraining operation by the recording material constraining means,
An image forming apparatus, comprising: an image carrier stopping means for stopping the movement of the image carrier after a lapse of a predetermined time. 2. The image forming apparatus according to claim 1, wherein the distance between the recording material presence / absence detecting portion of the recording material presence / absence detecting means and the recording material restraining means is set shorter than the dimension length of the transportable recording material. An image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the recording material restraining means is a positioning roll for positioning and transporting the recording material. 4. The image forming apparatus according to claim 1, further comprising a cleaning unit that cleans a residue on the image carrier downstream of the transfer unit. An image forming apparatus, wherein the image carrier is stopped after a predetermined period of time when the visible image forming area on the body passes through the cleaning means. 5. The image forming apparatus according to claim 1, further comprising: an abnormal-time transfer processing unit that reduces a transfer operation capability of the transfer unit before the stop operation of the image carrier by the image carrier stop unit is performed. An image forming apparatus characterized in that: 6. An image forming apparatus according to claim 5, wherein the transfer means is arranged in contact with the image carrier and performs a transfer process by a transfer electric field by an applied bias. Before the stopping operation of the image carrier by the body stopping means is performed, the transfer electric field by the transfer means is reduced and the transfer means is provided with the transfer means separated from the visible image carrying surface of the image carrier. An image forming apparatus characterized in that: 7. The image forming apparatus according to claim 1, further comprising a cleaning unit that cleans a residue on the image carrier downstream of the transfer unit, wherein the image carrier is stopped by the image carrier stopping unit. An image forming apparatus comprising: an abnormal-time cleaning unit that temporarily retreats a cleaning unit from a visible image carrying surface of an image carrier before a stop operation is performed.