JP3498556B2 - Image forming device - Google Patents

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 onto a recording material by 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 photoconductor on which a toner image corresponding to an electrostatic latent image is formed and a toner image on the photoconductor are intermediately transferred. An intermediate transfer member, a primary transfer device that transfers the toner image on the photosensitive member to the intermediate transfer member, and a secondary transfer device that secondarily transfers the toner image on the intermediate transfer member onto a sheet at a time. Those equipped are known (for example, Japanese Patent Publication No. Sho 49-
209, JP-A-62-206567).

In such an image forming apparatus, since transfer residual toner remains on the surface of the intermediate transfer body after transfer, the residual toner is cleaned and removed by the intermediate transfer body cleaner, and the intermediate transfer is performed again. A new toner image is formed on the body surface so that image formation can be repeated. Conventionally, as the intermediate transfer member cleaner of this type, a blade made of a material such as rubber having an appropriate hardness is used, and the edge of the blade is pressed against the surface of the intermediate transfer member by an appropriate pressing force by an elastic force to remove the toner. The cleaning blade method for scraping off and the fur brush method for cleaning the surface by sliding a rotating bristle brush onto the surface of the intermediate transfer member are well known. In particular, the cleaning blade method is a device compared to the fur brush method. Is simple and cheap,
It is widely used because of its high reliability.

However, in the image forming apparatus as described above, the intermediate transfer member cleaner is not only the residual toner after the secondary transfer but also a large amount of untransferred toner that is generated when a paper jam or a paper shortage occurs. Must also be cleaned, especially in full-color image forming apparatuses,
It is necessary to clean the toner about three times as much as in the case of monochrome image formation. The untransferred toner is charged by the primary transfer electric field and strongly adheres to the intermediate transfer body. Therefore, the blade or the fur brush alone may increase the load applied to the cleaner of the intermediate transfer member, and may not be able to clean a large amount of the generated toner. Therefore, in consideration of such cleaning at the time of trouble, it is necessary to use a high-performance intermediate transfer member cleaner such as a combination of a blade and a brush, which leads to complication of the apparatus and cost of the intermediate transfer member cleaner. Raises a technical problem.

As means for solving such a technical problem, in an image forming apparatus using an intermediate transfer system, when a large amount of untransferred toner is generated due to, for example, a paper jam or the like, an intermediate transfer member is formed. The cleaner is released to separate it from the intermediate transfer body, and the primary transfer device applies a DC bias voltage having a reverse polarity to that of the transfer to charge the untransferred toner to the reverse polarity, thereby exposing the untransferred toner on the intermediate transfer body. While the untransferred toner that has been reversely transferred to the body and then reversely transferred is cleaned by the photosensitive member cleaner provided on the photosensitive member,
There is disclosed a technique of cleaning the toner remaining on the intermediate transfer body without reverse transfer with an intermediate transfer body cleaner that is brought into pressure contact with the intermediate transfer body (see JP-A-5-297739).

[0006]

However, in such a prior art, in order to effectively reverse transfer the untransferred toner onto the photoconductor, the reverse DC bias voltage is usually higher than the normal voltage. It is necessary to set.
At this time, when a direct current bias voltage larger than that at the time of normal transfer is applied in the primary transfer device at the time of paper jam, etc., the charged charge of the toner itself remaining on the intermediate transfer member without being reversely transferred to the photosensitive member is generated. As a result, the adhesion between the residual toner and the intermediate transfer member becomes large, which makes it difficult to clean with the intermediate transfer member cleaner. By applying a large reverse bias voltage to the photoconductor, the injection current to the photoconductor becomes unnecessarily large, and the charge on the photoconductor cannot be completely removed by the static eliminator, and a history remains. There is a possibility that image unevenness may occur during image formation.

Further, as an image forming apparatus using an intermediate transfer system, a DC bias voltage having a reverse polarity to that at the time of transfer is applied to the residual toner on the intermediate transfer member during normal image formation to make the untransferred toner reverse polarity. A technique is disclosed in which an intermediate transfer member cleaner is not required by charging and untransferring the untransferred toner on the intermediate transfer member onto the photosensitive member in reverse (for example, JP-A-5-333706, JP-A-9-). 44007 publication). However, even with such a technical means, it is difficult to completely reverse transfer a large amount of untransferred toner generated when a trouble occurs to the photosensitive member side, and the toner remaining on the intermediate transfer member causes the next image. This causes deterioration of image quality during formation.

Further, a static eliminator for discharging residual toner is disposed between the secondary transfer device and the intermediate transfer member cleaner, and the static eliminator neutralizes the untransferred toner on the intermediate transfer member and then the intermediate transfer member. By cleaning the untransferred toner with a cleaner, it is conceivable to reduce the load on the intermediate transfer member cleaner when the paper is jammed. However, in such an aspect, when the space between the secondary transfer device and the intermediate transfer member cleaner is small and the degree of freedom in arranging the static eliminator is small, it is difficult to dispose the static eliminator. In addition, since the amount of untransferred toner is too large, it is necessary to use a high-performance intermediate transfer member cleaner, which eventually leads to a technical problem that the apparatus becomes complicated and the intermediate transfer member cleaner becomes expensive.

The present invention has been made in order to solve the above technical problems, and can effectively perform cleaning even when a large amount of untransferred toner is generated due to a recording material jam or a recording material shortage. An image forming apparatus that can be used is provided.

[0010]

Means for Solving the Problems That is, the invention concerns an
As shown in FIG. 1, an image carrier 1 on which toner images of respective colors are formed and carried, an intermediate transfer member 2 on which the toner images of respective colors on the image carrier 1 are successively transferred and held, and a transfer electric field A primary transfer unit 3 that sequentially forms the toner images of the respective colors on the image carrier 1 onto the intermediate transfer member 2, and a toner image of the respective colors held on the intermediate transfer member 2 by forming a transfer electric field. Four
Secondary transfer means 5 for collectively transferring the image onto the image carrier 1, an image carrier cleaner 6 for cleaning the residue on the image carrier 1, and an intermediate transfer member cleaner 7 for cleaning the residue on the intermediate transfer member 2 after the secondary transfer.
The recording material non-passage detecting means 8 for detecting the non-passage of the recording material 4 to be conveyed to the secondary transfer means 5, and the non-passage of the recording material 4 is detected by the recording material non-passage detecting means 8. Under the conditions, the intermediate transfer member 2 is idled, the transfer operation by the secondary transfer unit 5 is not performed, and an AC bias is applied to the primary transfer unit 3 to transfer the untransferred toner on the intermediate transfer member 2.
T 'After neutralization the untransferred toner T the static elimination'
And an abnormality occurrence control means 9 for controlling the intermediate transfer body cleaner 7 to be cleaned.

In such technical means, the present application
The present invention is not limited to a mode in which one image carrier 1 is rotated a plurality of times to primarily transfer toner images of respective colors to the intermediate transfer member 2, but a mode in which a plurality of image carriers 1 are provided (for example, four image carriers are used). It also includes a mode in which the bodies 1 are arranged in parallel and the toner images of respective colors are primarily transferred to the intermediate transfer body 2. The image carrier 1 and the intermediate transfer body 2 may be drum-shaped or belt-shaped, and the toner image forming method may be an electrophotographic method as long as it forms at least a toner image.
An electrostatic recording method or the like may be appropriately selected.

Further, if the recording material non-passage detecting means 8 can detect the non-passage of the recording material 4, a roll pair is provided in the conveyance path of the recording material 4 and the resistance value between the roll pairs is measured. It is also possible to appropriately select a recording material 4 or a material that provides a passage type or a reflection type photosensor in the conveyance path of the recording material 4 to detect the presence or absence of the recording material 4. Here, in the present invention,
The non-passage of the recording material 4 means, for example, a state in which the recording material 4 does not enter due to lack of the recording material 4, or a state in which the recording material 4 is not discharged due to jamming.

Further, the primary transfer means 3 may be properly selected as long as it forms a transfer electric field to transfer the toner images of the respective colors formed on the image carrier 1 onto the intermediate transfer body 2. . Furthermore, under the condition that the recording material non-passage detecting means 8 detects the non-passage of the recording material 4, the primary transfer means 3 discharges the untransferred toner T ′ , so that an AC bias is applied to the primary transfer means 3. It is necessary to provide means for doing so.

The application of the AC bias to the primary transfer means 3 includes, for example, a plurality of image carriers 1 (for example, four image carriers 1 are arranged in parallel and toner images of respective colors are transferred to the intermediate transfer member 2). In the mode of primary transfer), any of the primary transfer means 3 provided for each image carrier 1 may be provided with a means for applying an AC bias, but the untransferred toner T ' From the viewpoint of preventing a large load from being applied to the intermediate transfer member cleaner 7 during cleaning, the primary transfer means 3 of the image carrier 1 on the most upstream side in the rotation direction of the intermediate transfer member 2 or all the image carriers. It is preferable to dispose a means for applying an AC bias to the primary transfer means 3 of No. 1 so that the untransferred toner T ′ after the charge elimination is partially reversely transferred onto each image carrier 1.

Further, in the intermediate transfer member 2, the untransferred toner T ′ on the intermediate transfer member 2 is transferred by the primary transfer unit 3 under the condition that the recording material non-passage detecting unit 8 detects the non-passage of the recording material 4. It is preferable to perform idle rotation until the charge is removed and the intermediate transfer body cleaner 7 is cleaned.

Further, the secondary transfer means 5 may be appropriately selected as long as it can transfer a toner image on the intermediate transfer body 2 onto the recording material 4 by forming a transfer electric field. From the viewpoint of simplification, it is preferable that a roll-shaped transfer roll to which a transfer bias is applied is arranged in pressure contact with the intermediate transfer member 2.

In such an embodiment, in order to prevent the secondary transfer means 5 from unnecessarily transferring to something other than the recording paper 4, the recording material non-passage detecting means 8 detects the recording material 4. It is necessary not to perform the transfer operation by the secondary transfer means 5 under the condition that non-passage is detected.

[0018] As the specific embodiment, for example, to cut the transfer bias applied to the secondary transfer unit 5 when the passage of the untransferred toner T ', to reduce the transfer bias to a voltage enough to transfer is not performed Alternatively, it is possible to reduce the transfer force by forming an electric field in the opposite direction so that transfer is not performed. Further, in the mode in which the transfer bias is cut off, from the viewpoint of reliably preventing transfer due to pressure or the like, the condition under which the recording material non-passage detecting unit 8 detects the non-passage of the recording material 4 Under the secondary transfer means 5
It is preferable that the transfer roll is separated from the image bearing surface of the intermediate transfer member 2 immediately after the transfer bias is cut off and before the untransferred toner T ′ rushes in.

Further, the intermediate transfer member cleaner 7 is appropriately selected as long as it can clean the residual toner adhering to the surface of the intermediate transfer member 2 after the normal transfer operation and the untransferred toner T'generated by the non-passage of the recording material 4. It may be selected, but from the viewpoint of simplification of the apparatus configuration, it is preferable to use a blade made of an elastic body such as rubber and to place it in pressure contact with the intermediate transfer body 2. Furthermore, 'from the viewpoint of facilitating cleaning of the untransferred toner T on the intermediate transfer member 2' the transferred toner T to the intermediate transfer member cleaner 7 until is discharged by the primary transfer device 3 The intermediate transfer body cleaner 7 may be disposed so as to be in contact with and separated from the intermediate transfer body 2 and after the untransferred toner T ′ is discharged by the primary transfer means 3. preferable.

Further, if the static elimination by the AC bias untransferred toner T 'from the viewpoint of effectively performing, under conditions where non-passage of the recording medium 4 is detected by the recording material non-passed detecting means 8, at least not yet While the transfer toner T ′ passes through the primary transfer means 3, it is preferable to provide a peripheral speed difference between the peripheral speeds of the image carrier 1 and the intermediate transfer body 2.

Not only when the recording material 4 is not supplied to the secondary transfer means 5 due to occurrence of a jam or the like, but also the recording material 4 to which the size of the formed toner image of each color is supplied.
If it is larger than (for example, JI
SA4 is placed vertically, whereas the image is large in JIS A4 size), a large amount of untransferred toner is present on the portion of the intermediate transfer body 2 other than the contact with the recording material 4. T'is left. From the viewpoint of facilitating the cleaning of the untransferred toner T ′ thus generated,
A recording material size detecting means for detecting the type of the recording material 4 conveyed to the secondary transfer means 5, an image size detecting means for detecting the size of each color toner image formed on the intermediate transfer body 2, and both. A size comparing means for comparing the recording material size and the image size based on the detection result of is provided, and under the condition that the recording material size is smaller than the image size by the size comparing means, control is performed when an abnormality occurs. The means 9 idles the intermediate transfer body 2 and applies an AC bias to the primary transfer means 3 without performing the transfer operation by the secondary transfer means 5, thereby removing the untransferred toner T ′ on the intermediate transfer body 2. After removing the charge, it is preferable to control the removed untransferred toner T ′ to be cleaned by the intermediate transfer member cleaner 7.

Next, the operation of the above-mentioned technical means will be described. In FIG. 1, when the non-passage of the recording material 4 is detected by the recording material non-passage detecting unit 8, a toner image (which should be transferred to the intermediate transfer body 2 from the surface of the image carrier 1 and originally transferred to the recording material 4 ( Although the untransferred toner T ′ ) enters the secondary transfer means 5, the transfer operation by the secondary transfer means 5 is not performed. Next, when an AC bias is applied to the primary transfer means 3, the untransferred toner T ′ on the intermediate transfer body 2 is neutralized by the primary transfer means 3 and the electrostatic adhesion force to the intermediate transfer body 2 is weakened. To be At this time, the untransferred toner T ′ whose adhesion to the intermediate transfer body 2 has been weakened is left on the intermediate transfer body 2 and transferred to the image carrier 1 side when passing through the primary transfer portion. Is divided into two. Thereafter, the residual toner transferred to the image carrier 1 side is easily cleaned by the image carrier cleaner 6, while the untransferred toner T ′ remaining on the intermediate transfer member 2 is easily cleaned by the intermediate transfer member cleaner 7.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments 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 this embodiment) to which the present invention is applied. In the figure, reference numeral 11 is a photosensitive drum (latent image bearing member), and the surface of the photosensitive drum (latent image bearing member) rotates in the direction of the arrow A.
An electrostatic latent image corresponding to the image information is formed by a well-known electrophotographic process such as that shown in FIG. Further, around the photosensitive drum 11, developing devices 14 to 17 corresponding to each color of black (Bk), yellow (Y), magenta (M), and cyan (C) are arranged. The electrostatic latent image formed on the drum 11 is developed by any of the developing devices 14 to 17 to form a toner image. Incidentally, reference numeral 1
A drum cleaner 9 collects the residual toner that has not been primarily transferred.

Reference numeral 20 denotes an intermediate transfer belt arranged so as to be in contact with the surface of the photosensitive drum 11.
A plurality of (four in the present embodiment) rolls 21 to 24 are stretched and rotated in the arrow B direction. Here, in the present embodiment, reference numeral 21 is a drive roll for the intermediate transfer member, 22 is a driven roll, 23 is a tension roll for controlling the tension of the intermediate transfer belt 20 to be constant, and 2 is a tension roll.
Reference numeral 4 is an opposing roll (backup roll) for secondary transfer. Further, in the present embodiment, the intermediate transfer belt 20 has a volume resistivity of 10 ⁶ to 10 ⁶ by containing an appropriate amount of carbon black or the like in resin such as polyimide, polycarbonate, polyester, polypropylene, polyethylene terephthalate or various rubbers. ^It is formed to have a thickness of ¹⁵ Ω · cm, and its thickness is set to 0.1 mm, for example.

Further, in the present embodiment, at the portion of the intermediate transfer belt 20 facing the photosensitive drum 11 (primary transfer position), the primary transfer device (primary transfer device in the present embodiment) is provided on the back surface side of the intermediate transfer belt 20. A transfer roll) 18 is provided, and by applying a voltage having a polarity opposite to the charging polarity of the toner to the primary transfer roll 18, the photosensitive drum 11
The upper toner image is electrostatically attracted to the intermediate transfer belt 20.

A secondary transfer device 40 is arranged at the secondary transfer position of the intermediate transfer belt 20 facing the conveyance path of the sheet P as a recording material. In the present embodiment, the intermediate transfer belt 20 is provided. A secondary transfer roll 25 arranged in pressure contact with the toner image carrier surface side, and a counter roll (backup roll) 24 arranged on the back side of the intermediate transfer belt 20 and serving as a counter electrode of the secondary transfer roll 25. ing. Further, in the present embodiment, the secondary transfer roll 25 is grounded, and the bias having the same polarity as the charging polarity of the toner is stably applied to the backup roll 24 via the power feeding roll 26. A cleaning blade 28 made of urethane rubber, for example, is attached to the secondary transfer roll 25.

In this embodiment, the backup roll 24 is made of EPDM (ethylene propylene diene rubber) having a two-layer structure in which the outer periphery of the metal core material is covered with the foam elastic layer and the outer conductive layer. I was there. The outer conductive layer is a semiconductive EPDM foamed rubber in which carbon black is dispersed in an amount of 15 to 35% by weight, and the surface layer has a thickness of 0.5 to 1.5.
mm. Surface resistivity is 10 ⁷ to 10 ¹⁰ Ω
It is controlled to the resistance area of / □. In addition, the secondary transfer roll 2
5 is a core layer made of carbon black dispersed foam rubber EPDM material fixed around the core metal and a fluorocarbon resin material of carbon black dispersion having a thickness of 5 to 20 μm through a skin layer, and coated with the core metal. The volume resistivity with the layer is 10 ⁴ Ω · cm to 10 ⁶ Ω · cm, and the roll hardness is 20 ° to 45 ° in Asuka C hardness.

Further, on the downstream side of the secondary transfer device 40, the toner remaining on the intermediate transfer belt 20 without being transferred to the paper P and the untransferred toner due to the supply trouble of the paper P are transferred.
A belt cleaner 41 for removing (not shown) is provided.

Further, in the present embodiment, the paper transport system feeds the paper P from the paper tray 50 to the feed roll 51.
The sheet P is sent to the secondary transfer position at a predetermined timing after the positioning is temporarily stopped by the registration roll (registration roll) 52, and the sheet P after the secondary transfer is not shown. The sheet is guided to the conveyance belt 53 via the sheet conveyance guide, and is conveyed to the fixing device 54 by the conveyance belt 53. Further, in the present embodiment, as shown in FIG. 3, the secondary transfer roll 25 and the belt cleaner 41 are connected to and separated from the intermediate transfer belt 2 by contact and separation devices 104 and 105 such as actuators.
When the color image is formed, the toner image before the final color is transferred to the secondary transfer roll 25,
These members are set to be separated from the intermediate transfer belt 20 until they pass through the belt cleaner 41.

Further, in this embodiment, as shown in FIG. 3, a paper supply trouble control system 100 for controlling the cleaning operation when a paper supply trouble (paper jam or paper shortage) occurs is provided. In the figure, reference numeral 101 is a registration sensor which is provided on the downstream side of the registration roll 52 and which is a reflection type optical sensor for detecting entry and passage of the paper P, 102 is a switch for applying a bias to the power feeding roll 26, and 103 is power feeding. A DC bias power source for the roll 26, and 104 denotes the secondary transfer roll 25 for the intermediate transfer belt 20.
A contacting / separating device for retracting from the belt cleaner 105 is a belt cleaner 41.
Contacting / separating device for retracting the sheet from the intermediate transfer belt 20,
Is a switching AC / DC switch for bias to be supplied to the primary transfer roll 18, 107 is an AC power supply for supplying an AC bias to the primary transfer roll 18, 108 is a DC power supply for supplying a DC bias to the primary transfer roll 18, and 109 is these Is a control device for controlling the.

Further, FIG. 4 shows a block diagram of the control system 100. In the figure, the paper passage detection signal 111 from the registration sensor 101 is fetched by the CPU 122 via the input interface 121, and then the CPU 122
After the drive control program stored in advance in the ROM 123 is executed to appropriately perform data processing with the RAM 124, the secondary transfer bias control signal 131 is sent to the switch 102 of the power feeding roll 26 via the output interface 125. , The secondary transfer roll position control signal 132 is sent to the contact / separation device 104 of the secondary transfer roll 25.
The belt cleaner position control signal 1
33, the intermediate transfer belt speed control signal 134 to the driving roll 21 of the intermediate transfer belt 20, and the primary transfer roll bias switching signal 135 to the changeover switch 106 of the primary transfer roll 18. There is.

Next, the image forming process of the color image forming apparatus according to this embodiment will be described. Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed. Specifically, the photoconductor drum 11
If the electrostatic latent image written above corresponds to, for example, yellow image information, the electrostatic latent image is developed by the developing device 15 containing yellow (Y) toner, and the photosensitive drum 1
A yellow toner image T is formed on 1. Then, the unfixed toner image T formed on the photosensitive drum 11 is transferred from the photosensitive drum 11 to the surface of the intermediate transfer belt 20 at the primary transfer position where the photosensitive drum 11 and the intermediate transfer belt 20 are in contact with each other.

At this time, when a monochromatic image is formed,
The toner image T primarily transferred to the intermediate transfer belt 20 is secondarily transferred immediately. However, when a color image in which toner images of a plurality of colors are superimposed is formed, the photosensitive drum 1
The steps of forming a toner image on the first image forming apparatus and primary transferring the toner image are repeated for the number of colors. For example, when forming a toner image in which toner images of four colors are superimposed, black, yellow,
Magenta and cyan toner images T are formed, and these toner images T are primarily transferred to the intermediate transfer belt 20 sequentially.
On the other hand, the intermediate transfer belt 20 rotates in the same cycle as the photosensitive drum 11 while holding the black toner image T that has been primarily transferred first, and on the intermediate transfer belt 20, the yellow and magenta are rotated for each rotation. And a cyan toner image T is formed.

The toner image T is primarily transferred to the intermediate rolling Utsushibe belt 20 in this way, with rotation of the intermediate transfer belt 20 is conveyed to the secondary transfer position. On the other hand, the paper P is supplied to the secondary transfer position by the registration roll 52 at a predetermined timing, and the secondary transfer roll 25 nips the paper P with respect to the backup roll 24.

At this time, as shown in FIG. 5, when the registration sensor 101 confirms the entry and passage of the paper P, the registration sensor 101 outputs the paper passage detection signal 1
11 is sent out, and the normal cleaning process is performed.
That is, at the secondary transfer position shown in FIG. 2, the toner carried on the intermediate transfer belt 20 is acted by the transfer electric field formed between the secondary transfer roll 25 which is the secondary transfer device 40 and the backup roll 24. The image T is transferred onto the paper P at the secondary transfer position. The paper P on which the toner image T has been transferred is conveyed to the fixing device 54 by the conveying belt 53 and the toner image is fixed. Further, the toner remaining on the intermediate transfer belt 20 after the transfer is removed by the belt cleaner 41.
To be cleaned.

A timing chart during normal operation is shown in FIG. In the figure, the toner image T is sequentially primary-transferred from the photosensitive drum 11 onto the intermediate transfer belt 20. At this time, a DC transfer bias is applied to the primary transfer roll 18. Then, during the primary transfer, the secondary transfer roll 2
5 and the belt cleaner 41 are separated from the intermediate transfer belt 20. Next, with the completion of the primary transfer, the bias applied to the primary transfer roll 18 is cut off, and then the conveyance of the paper P is started. Then, when the registration sensor 101 confirms that the paper P has entered, the control device 109 moves the secondary transfer roll 25 to the intermediate position before the paper P reaches the nip portion between the secondary transfer roll 25 and the backup roll 24. A secondary transfer roll position control signal 132 that is brought into pressure contact with the transfer belt 20 is sent, and immediately after that, a secondary transfer bias control signal 131 that starts the application of the transfer bias by the power feeding roll 26 is sent.

Then, as the paper passage detection signal 111,
A signal that the paper P has passed the registration sensor 101 is sent, and the secondary transfer is performed by the secondary transfer device 40.
After that, by the time the toner remaining on the intermediate transfer belt 20 after the transfer to the belt cleaner 41 enters, the control device 1
A belt cleaner position control signal 133 for pressing the belt cleaner 41 to the intermediate transfer belt 20 is sent out, and the residual toner is collected by the belt cleaner 41.

On the other hand, in FIG. 5, when a paper out or paper jam occurs, a special cleaning process is performed. That is, as shown in the timing chart of FIG. 7, for example, a paper jam occurs when the bias applied to the primary transfer roll 18 is cut and the conveyance of the paper P is started with the completion of the primary transfer to the intermediate transfer belt 20. When the error occurs, the registration sensor 101 detects the entry of the sheet but does not detect the passage of the sheet, and therefore outputs an abnormal signal as the sheet passage detection signal 111.

At this time, the control device 109 neither presses the secondary transfer roll 25 against the intermediate transfer belt 20 nor does it apply a transfer bias to the secondary transfer roll 25 of the power supply roll 26.

After that, the untransferred toner on the intermediate transfer belt 20 which has not been transferred is moved by the belt cleaner 4 as it moves.
However, the control device 109 keeps the belt cleaner 41 separated from the intermediate transfer belt 20 at this time. Then, untransferred bets on the intermediate transfer belt 20
By the time the toner reaches the nip portion with the primary transfer roll 18, the control device 109 sends the intermediate transfer belt speed control signal 134 so as to reduce the speed of the intermediate transfer belt 20, and the alternating current is applied to the primary transfer roll 18. The primary transfer roll bias switching signal 135 is sent to apply the bias. When the untransferred toner plunges into the nip region between the photoconductor drum 11 and the primary transfer roll 18, the untransferred toner on the intermediate transfer belt 20 is neutralized, and about half of the untransferred toner is electrostatically attached and the nip pressure is applied. The toner transferred onto the photosensitive drums 11 and transferred onto the photosensitive drums 11 is thereafter collected by the drum cleaner 19.

On the other hand, the untransferred toner on the intermediate transfer belt 20 which has not been transferred to the photosensitive drum 11 by being discharged by the AC bias on the primary transfer roll 18 advances to the secondary transfer device 40. At this time, the control device 109 keeps the secondary transfer roll 25 separated from the intermediate transfer belt 20. Then, the untransferred toner on the intermediate transfer belt 20
The controller 1 before the belt reaches the belt cleaner 41.
At 09, a belt cleaner position control signal 133 is sent to bring the belt cleaner 41 into pressure contact with the intermediate transfer belt 20, and the residual toner is collected by the belt cleaner 41. After that, after the collection of the untransferred toner is completed,
The control device 109 sends the intermediate transfer belt speed control signal 134 to stop the intermediate transfer belt 20, and the series of image forming processes ends. In addition, in FIG. 5, when the paper is out, the registration sensor 101 causes the paper P
Is not detected, an abnormal signal is sent and cleaning is performed in the same process.

[Second Embodiment] This embodiment is substantially the same as the first embodiment, except that FIG.
As shown in FIG. 5, the toner image T to be transferred is compared with the size of the paper P to be supplied, and the cleaning operation is controlled when the image size exceeds the paper size. In the figure, the registration sensor 101 also has a function of detecting the size of the paper P. Further, reference numeral 151 denotes an image input device such as a scanner, and 152 denotes the exposure beam 13 according to the input image information.
Is a writing device for controlling the.

Further, in the present embodiment, the control system 10
0 indicates the registration sensor 101, as indicated by the dotted line in FIG.
In addition to the paper passage detection signal 111 from the image input device 1
Image size signal 112 from 51 and registration sensor 10
The paper size signal 113 from No. 1 is taken into the CPU 122 via the input interface 121, and the control similar to that of the first embodiment is executed. In particular, in the present embodiment, as shown in FIG. 9, the image size and the paper size are compared, and the special cleaning process is executed even when the image size is larger than the paper size. There is.

In this embodiment, as in the first embodiment, a large amount of untransferred toner generated when a paper out or paper jam occurs is easily collected, and the image size is larger than the paper size. Is large, that is, paper P
Even in the case where a large amount of toner that cannot be transferred onto the surface occurs, these toners are easily collected.

Third Embodiment FIG. 10 shows a third embodiment of the color image forming apparatus to which the present invention is applied. In the figure, the color image forming apparatus according to the present embodiment is provided with a plurality of image forming units 20 in which toner images of respective color components are formed by, for example, an electrophotographic method.
0 (specifically, 200Y, 200M, 200C, 20
0Bk) are arranged in parallel, the toner images of the respective color components formed by the respective image forming units are sequentially primary-transferred onto the intermediate transfer belt 220, and the secondary transfer roll 225 transfers the intermediate transfer belt 220 onto the paper P supplied from the supply tray 250. The toner images of the respective color components above are secondarily transferred and guided to the fixing device 254 via the conveyor belt 253.

In the present embodiment, the image forming unit 200 for each color component has a uniform charging in which the photosensitive drum 201 is charged around the photosensitive drum 201 (specifically, 201Y, 201M, 201C and 201Bk). Bowl 20
2. A laser scanning type image exposure device 203 for writing an electrostatic latent image on the photosensitive drum 201, and a developing device for accommodating toner of each color component and visualizing the electrostatic latent image on the photosensitive drum 201. 204, a primary transfer roll 205 for transferring the toner image of each color component on the photosensitive drum 201 to the intermediate transfer belt 220, a cleaner 206 for removing the residual toner on the photosensitive drum 201, etc. are sequentially arranged. .

For example, when the color image forming apparatus is configured as a digital color copying machine, a color image reading device reads a document set on a document table (not shown), and the read signal is digital imaged by the image signal processing means. The signals are converted into signals and temporarily stored in a memory, and toner images of respective colors are formed based on the stored digital image signals of four colors (Y, M, C, Bk).

That is, the image forming unit 2 is responsive to the digital image signals of the respective colors inputted from the image signal processing means.
00Y, 200M, 200C, 200Bk are driven respectively, and chargers 202Y, 202M, 202C, 202Bk are respectively driven.
The photosensitive drums 201Y, 201 that are uniformly charged by
The electrostatic latent images are written in M, 201C, and 201Bk, respectively. Then, each of these electrostatic latent images is developed by the developing device 204 containing the toner of each color to form the toner image of each color. When the color image forming apparatus is configured as a device such as a printer, toner images of respective colors may be formed based on an image signal input to the image signal processing means from the outside or the like.

Further, in the present embodiment, reference numeral 220
Is a belt-shaped intermediate transfer belt arranged so as to be stretched around a plurality of rolls and abutted on the surface of the photosensitive drum 201;
Is a counter roll (backup roll) for secondary transfer.

Further, in the present embodiment, at the portion of the intermediate transfer belt 220 facing the photosensitive drum 201 (primary transfer position), the primary transfer device (primary transfer device in the present embodiment) is provided on the back side of the intermediate transfer belt 220. Transfer roll) 205
Are respectively provided, and by applying a voltage having a polarity opposite to the charging polarity of the toner to the primary transfer roll 205, the toner image on the photosensitive drum 201 is electrostatically attracted to the intermediate transfer belt 220. Has become.

Further, a secondary transfer device 240 is arranged at the secondary transfer position of the intermediate transfer belt 220 facing the conveyance path of the sheet P as a recording material. In the present embodiment, the intermediate transfer belt 220 is provided. A secondary transfer roll 225 arranged in pressure contact with the surface of the toner image carrier and a counter roll (backup roll) 224 arranged on the back side of the intermediate transfer belt 220 and serving as a counter electrode of the secondary transfer roll 225. ing. Then, in the present embodiment, the secondary transfer roll 2
25 is grounded, and the backup roll 22
A bias having the same polarity as the charging polarity of the toner is stably applied to No. 4 via the power feeding roll 226. A cleaning blade 228 made of urethane rubber, for example, is attached to the secondary transfer roll 225, and the materials of the intermediate transfer belt 220, the secondary transfer roll 225, and the backup roll 224 are the same as those in the first embodiment. Is.

Further, on the downstream side of the secondary transfer device 240,
Untransferred preparative due to supply problems of the toner and the paper P remaining on the intermediate transfer belt 220 without being transferred onto the sheet P
Belt cleaner 241 for removing toner is provided.

Further, in the present embodiment, the paper transport system feeds the paper P from the supply tray 250 to the feed roll 2
The sheet P is sent out at 51, the positioning is temporarily stopped by the registration roll (registration roll) 252, and then the sheet P is sent to the secondary transfer position at a predetermined timing. The sheet P after the secondary transfer is conveyed. It is guided to the conveyor belt 253 through the guide 222, and the conveyor belt 25
At 3, the sheet is conveyed to the fixing device 254. Further, in the present embodiment, as shown in FIG. 11, the secondary transfer roll 225 and the belt cleaner 241 are arranged so as to be able to come into contact with and separate from the intermediate transfer belt 220 by the contacting / separating devices 304 and 305 such as actuators. .

Further, in this embodiment, as shown in FIG. 11, a paper supply trouble control system 300 for controlling the cleaning operation when a paper supply trouble (paper jam or paper shortage) occurs is provided. In the figure, reference numeral 301
Is a registration sensor that is provided on the downstream side of the registration roll 252 and includes a reflection type optical sensor that detects the entrance and passage of the paper P. 302 is a switch for applying a bias to the power supply roll 226. Reference numeral 304 designates the secondary transfer roll 225 and the intermediate transfer belt 2
20, a contact / separation device 305 for retracting the belt cleaner 241 from the intermediate transfer belt 220, 306 for an AC / DC changeover switch for bias supplied to the primary transfer roll 205Y, and 307 for the primary transfer roll 20.
5Y is an AC power supply that supplies an AC bias, 308 is a DC power supply that supplies a DC bias to the primary transfer roll 205Y, and 309 is a control device that controls these.

Also in the present embodiment, when a paper run-out or a paper jam occurs, a special cleaning process is executed by the image forming process similar to that of the first embodiment, and a large amount of the intermediate transfer belt 220 is generated. The residual toner is easily collected. In this embodiment, although the application of the AC bias is performed only at the primary transfer roll 205Y of the uppermost stream side is not limited to this, other primary transfer roll 205M, and go in 205C or 205BK, A plurality of them may be used, and the tandem color image forming apparatus according to the present embodiment may be added with the configuration shown in the second embodiment to compare the image size with the paper size. It is needless to say that the special cleaning process may be controlled when the image size is large.

[0056]

As described above, according to the image forming apparatus of the present invention, when a large amount of toner that cannot be transferred to the recording material is generated due to lack of the recording material or jam, the toner is discharged. Since the cleaning is performed after that, the toner can be collected without using a complicated and expensive intermediate transfer member cleaner, and a good image without cleaning failure can be obtained. Furthermore, by performing control by comparing the image size to be transferred and the recording material size, even if the image size becomes larger than the recording material size, it is possible to use a complicated and expensive intermediate transfer member cleaner. The toner can be collected without any trouble, and a good image without defective cleaning can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an outline of a color image forming apparatus according to the first embodiment.

FIG. 3 is an explanatory diagram showing a control system of the color image forming apparatus according to the first embodiment.

FIG. 4 is a block diagram showing a control system of the color image forming apparatus according to the first and second embodiments.

FIG. 5 is a flowchart showing a cleaning process of the color image forming apparatus according to the first embodiment.

FIG. 6 is a timing chart showing the operation timing when the normal cleaning process of the color image forming apparatus according to the first embodiment is executed.

FIG. 7 is a timing chart showing an operation timing at the time of performing a special cleaning process of the color image forming apparatus according to the first embodiment.

FIG. 8 is an explanatory diagram showing a control system of the color image forming apparatus according to the second embodiment.

FIG. 9 is a flowchart showing a cleaning process of the color image forming apparatus according to the first embodiment.

FIG. 10 is an explanatory diagram showing a configuration of a tandem type color image forming apparatus according to a third embodiment.

FIG. 11 is an explanatory diagram showing a control system of the tandem color image forming apparatus according to the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Intermediate transfer body, 3 ... Primary transfer means, 4
... recording material, 5 ... secondary transfer means, 6 ... image carrier cleaner,
7 ... Intermediate transfer member cleaner, 8 ... Recording material non-passage detecting means,
9 ... Control means when abnormality occurs, T ' ... Untransferred toner

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kawabata 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zerox Co., Ltd. (56) Reference JP-A-5-297739 (JP, A) (58) Fields investigated (58) Int.Cl. ⁷ , DB name) G03G 15/16-15/16 103 G03G 15/00 303 G03G 21/00 370-540 G03G 21/14

Claims (5)

(57) [Claims] 1. An image carrier on which a toner image of each color is formed and carried, an intermediate transfer member on which the toner image of each color on the image carrier is successively transferred and held, and an image is formed by forming a transfer electric field. Primary transfer means for sequentially transferring the toner images of the respective colors on the carrier to the intermediate transfer body, and secondary transfer means for collectively transferring the toner images of the respective colors held on the intermediate transfer body to the recording material by forming a transfer electric field. An image carrier cleaner for cleaning the residue on the image carrier, an intermediate transfer member cleaner for cleaning the residue on the intermediate transfer member after the secondary transfer, and a recording material to be conveyed to the secondary transfer means. Of the recording material non-passage detecting means for detecting the non-passage of the recording material, and under the condition that the recording material non-passage detecting means detects the non-passage of the recording material, the intermediate transfer member is idled and transferred by the secondary transfer means. AC bias is applied to the primary transfer means without any operation. An image forming apparatus, comprising: a control unit at the time of occurrence of an abnormality, which controls to discharge the untransferred toner on the intermediate transfer body by means of and to clean the discharged untransferred toner by an intermediate transfer body cleaner. . 2. The image forming apparatus according to claim 1, wherein the recording material size detecting means for detecting the size of the recording material conveyed to the secondary transfer means, and the toner of each color formed on the intermediate transfer body. Image size detection means for detecting the size of the image,
When an abnormality occurs under the condition that the recording material size is smaller than the image size by the size comparing means, the size comparing means compares the recording material size and the image size based on the detection results of both. The control unit idles the intermediate transfer member, removes the untransferred toner on the intermediate transfer member by applying an AC bias to the primary transfer unit without performing the transfer operation by the secondary transfer unit, An image forming apparatus, which controls to remove uncharged toner that has been discharged by an intermediate transfer member cleaner. 3. The image forming apparatus according to claim 1, wherein the abnormality occurrence control unit causes the secondary transfer unit to be intermediate when the untransferred toner on the intermediate transfer body passes through the secondary transfer unit. image forming apparatus and controlling so as to between the image bearing surface or et away of the transcript. 4. The image forming apparatus according to claim 1, wherein the abnormality occurrence control unit includes an intermediate transfer member cleaner when untransferred toner on the intermediate transfer member before charge removal passes through the intermediate transfer member cleaner. Is separated from the intermediate transfer body, and when the untransferred toner on the intermediate transfer body after the charge removal passes through the intermediate transfer body cleaner, the intermediate transfer body cleaner is controlled to be pressed against the intermediate transfer body. . 5. The image forming apparatus according to claim 1, wherein the abnormality occurrence control unit controls the image carrier and the intermediate member under the condition that the recording material non-passage detection unit detects the recording material non-passage. An image forming apparatus, characterized in that the rotational speed of a transfer member is controlled to have a peripheral speed difference.