JP4239628B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tandem type color image forming apparatus. More specifically, the present invention relates to a cleanerless type image forming apparatus having no cleaner in each color image forming unit.
[0002]
[Prior art]
Conventionally, in a tandem type color image forming apparatus, in order to reduce waste toner and to reduce the size of the image forming apparatus, a cleanerless type having no cleaner has been adopted for each image forming unit of each color. Yes. In this method, among the toner images formed on the image carriers of the respective colors, the transfer residual toner that cannot be transferred by the transfer process is collected from the image carrier to the developing device and reused.
[0003]
However, in such a cleanerless type image forming apparatus, when a large amount of residual toner remains due to continuous image formation or a decrease in transfer efficiency, all the residual toner cannot be collected by the developing means. There was a case. On the other hand, there has been proposed an image forming apparatus that removes the transfer residual toner from the image carrier by once collecting it on a contact-type charging member of the charging device (see, for example, Patent Document 1). In this apparatus, the toner temporarily collected in the magnetic brush portion of the magnetic brush charger as the charging member is discharged again onto the image carrier in the time zone between the image forming processes. Then, it is recovered from the image carrier to the developing device and reused. Alternatively, the toner image is transferred from the image carrier to the intermediate transfer belt and collected by a cleaner provided on the intermediate transfer belt.
[0004]
[Patent Document 1]
JP 2001-194951 A (pages 8-15)
[0005]
[Problems to be solved by the invention]
However, when the conventional image forming apparatus described above is stopped in the middle of the image forming process due to, for example, a paper jam, untransferred toner remains on each image carrier or intermediate transfer belt. Sometimes. The polarity of the toner differs depending on the state where the process is stopped and the location where the toner remains, and cannot be specified. This is because it varies depending on the timing of trouble occurrence and machine stop timing.
[0006]
For this reason, when the recovery operation is started after the trouble such as a jam is resolved, if the above recovery operation is performed after the interrupted operation when the machine is stopped, there is a possibility of performing recovery different from the normal case. For example, the toner on the intermediate transfer belt may be reflected on the image carrier and collected as residual toner. The toner image remaining on the intermediate transfer belt at the time of interruption is a toner image formed by the image forming unit upstream from the current position. Then, if it is recovered to the image carrier, the image carrier is that of the image forming unit downstream from the current position. That is, there is a problem that toner of a color different from that of the image forming unit is collected, and the collected toner may be mixed in the developing device and the color may be changed.
[0007]
The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, an object of the present invention is to provide an image forming apparatus capable of forming a stable color image without causing a change in the color of the toner even when the operation is stopped due to a trouble.
[0008]
[Means for Solving the Problems]
In order to solve this problem, the image forming apparatus of the present invention includes a plurality of image forming units that perform image formation with toner using a developing device and an image carrier, and sequentially transfers toner images from the plurality of image forming units. Each image forming unit is an image forming apparatus that collects toner remaining on the image carrier after transfer to the transfer body to a developing device, and at least each of the image forming units when an abnormality occurs. One is a recovery prohibiting means for prohibiting the recovery of toner from the image carrier to the developing device, and a toner on the image carrier that is a target of the recovery prohibiting means among the image forming units when an abnormality occurs. And a toner discharging means for discharging the toner onto the transfer body.
[0009]
According to the image forming apparatus of the present invention, since the transfer residual toner remaining on the image carrier is collected in the developing device in a normal time, it can be reused. On the other hand, when an abnormality occurs, the recovery prohibiting means prohibits the recovery of toner to the developing unit in at least one image forming unit. Therefore, since no toner is collected in the developing unit of the image forming unit, a change in color due to the color mixture of toner is prevented. Further, the toner whose collection to the developing device is prohibited is discharged to the transfer member by the toner discharging means. Accordingly, the toner is removed from the image bearing member and does not affect the next image formation. Thus, even when the operation is stopped due to a trouble, a stable color image can be formed without causing a change in the color of the toner. Here, the transfer body that receives the transfer of the toner image includes one that carries a recording medium and receives the transfer onto the recording medium.
[0010]
The present invention further includes a determination unit that determines whether or not the occurrence location of an abnormality is a location where it is necessary to immediately stop the image carrier of each image forming unit. If it is not necessary to stop the operation, it is performed during the period from the occurrence of the abnormality until the operation stops. If the determination of the determination unit needs to be stopped, it is performed during the pre-operation period after the operation returns. Is to be done.
It is preferable to remove the toner remaining on the image carrier or the transfer member as soon as possible. Therefore, if possible, it is performed during the period from the occurrence of abnormality to the stop of operation. However, if there is a possibility that a further problem may be caused by forcibly rotating the image bearing member or the transfer member, it may be performed prior to the image forming operation after the operation is restored.
[0011]
Furthermore, in the present invention, it is desirable to have a collecting means for collecting the toner on the transfer body, and to collect the toner discharged on the transfer body by the toner discharging means.
In this way, unnecessary toner discharged to the transfer body is secondarily transferred to the recording medium, so that the paper is wasted or reflected back to the image carrier and becomes noise of the next image formation. Because there is no.
[0012]
Further, in the present invention, the collection prohibiting means and the toner discharging means are intended for the image forming units other than the most downstream in the moving direction of the transfer body, and the toner discharged on the transfer body by the toner discharging means is It is desirable that the image is collected by the image forming unit at the most downstream side in the moving direction of the transfer body.
In this way, all of the toner remaining in each place can be collected in the most downstream image forming unit in the moving direction of the transfer body. Therefore, the toner can be reused in the most downstream image forming unit without wasting it.
[0013]
Furthermore, in the present invention, it is desirable that the image forming unit at the most downstream side in the moving direction of the transfer body is to form a black image.
This is because, with black toner, even if some other color toner is mixed in, the color tone hardly changes.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. The image forming apparatus 1 according to the present embodiment is a tandem type color image forming apparatus mounted on a copying machine, a printer, a facsimile, or the like. In the following, each subscript indicates a configuration for each color in which K is black, C is cyan, M is magenta, and Y is yellow.
[0015]
As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment has image forming units 20K, 20C, 20M, and 20Y for each color arranged in this order from the downstream side along the intermediate transfer belt 11. ing. The image forming units 20K, 20C, 20M, and 20Y have the same configuration. The intermediate transfer belt 11 is stretched by three belt rollers 12, 13, and 14 and rotated in the direction of the arrow in the figure. Further, an intermediate transfer belt cleaner 15 is disposed in contact with the intermediate transfer belt 11 at a position away from the image forming units 20K, 20C, 20M, and 20Y. Further, primary transfer members 16K, 16C, 16M, and 16Y are disposed at positions facing the image forming units 20K, 20C, 20M, and 20Y with the intermediate transfer belt 11 interposed therebetween.
[0016]
Each of the image forming units 20K, 20C, 20M, and 20Y includes photosensitive drums 21K, 21C, 21M, and 21Y that rotate in the direction of the arrow in the drawing. In addition, charging devices 22K, 22C, 22M, and 22Y, exposure devices 23K, 23C, 23M, and 23Y, and developing devices 24K, 24C, 24M, and 24Y are arranged around them. The developing devices 24K, 24C, 24M, and 24Y include developing rollers 25K, 25C, 25M, and 25Y, respectively. Here, as the charging devices 22K, 22C, 22M, and 22Y, contact charging type charging members are used. For example, a charging member such as a brush, a roller, a magnetic brush, or a film is selected. Here, no cleaner is provided around each of the image forming units 20K, 20C, 20M, and 20Y.
[0017]
Further, a secondary transfer member 31 is disposed so as to face the belt roller 12, and the recording medium 32 is conveyed between the belt roller 12 and the secondary transfer member 31. A fixing device 33 is provided on the downstream side (upper side in the drawing) of the secondary transfer member 31. These devices are all general ones.
[0018]
A schematic system configuration of the image forming apparatus 1 is shown in FIG. The image forming apparatus 1 includes a control device 2 that controls the entire image forming apparatus 1. The control device 2 includes a normal operation unit 3 that controls each device during normal operation, an abnormality detection unit 4 that detects an abnormality of the device, and an abnormal operation unit 5 that controls each device when an abnormality occurs. Is provided. Further, the abnormal-time operation unit 5 includes a recovery prohibiting unit 6 that prohibits recovery of toner to the developing devices 24K, 24C, 24M, and 24Y of the image forming units 20K, 20C, 20M, and 20Y, and a photosensitive drum 21K, A toner discharge portion 7 that discharges the toner on 21C, 21M, and 21Y to the intermediate transfer belt 11 is provided.
[0019]
In addition to the image forming units 20K, 20C, 20M, and 20Y, the control device 2 includes an intermediate transfer belt drive unit 8 that controls the rotation of the intermediate transfer belt 11, and another device drive unit 9 that drives other devices. And also control. The intermediate transfer belt drive unit 8 drives and controls the belt rollers 12, 13, and 14 to rotate the intermediate transfer belt 11. The other device driving unit 9 controls the operation of the devices such as the primary transfer members 16K, 16C, 16M, and 16Y and the secondary transfer member 31.
[0020]
Next, the operation of the image forming apparatus 1 in the normal state will be described based on the operation sequence of FIG. These operations are normally controlled by the control unit 3. The image forming apparatus 1 starts to operate when a print signal is input (step 41). First, a pretreatment process such as warming up is performed (process 42). Then, an image forming process (process 43) for forming an image on one recording medium 32 and an inter-image process (process 44) executed between the image forming processes are repeated according to the instructed number of printed sheets. When the last image forming step (step 45) is completed, a post-processing step (step 46) is performed. As a result, the series of printing steps is completed (step 47), and the standby state is set.
[0021]
The operation of each image forming unit 20K, 20C, 20M, 20Y in each image forming step (step 43 and step 45) will be described. First, <charging>. For example, an oscillation voltage obtained by superimposing a rectangular wave, an AC voltage, a pulse voltage, etc. on a DC voltage is used as an applied voltage, and the surfaces of the photosensitive drums 21K, 21C, 21M, and 21Y by the charging devices 22K, 22C, 22M, and 22Y. Is charged. Next, <exposure>. Light is irradiated to the photosensitive drums 21K, 21C, 21M, and 21Y by the exposure devices 23K, 23C, 23M, and 23Y. Thereby, the electric potential of a light irradiation part attenuate | damps. Next, <Development>. When the portions of the photosensitive drums 21K, 21C, 21M, and 21Y whose potential is attenuated by exposure come to the positions of the developing devices 24K, 24C, 24M, and 24Y, due to the potential difference with the rotating developing rollers 25K, 25C, 25M, and 25Y. Toner is attracted. As a result, toner images of the respective colors are formed on the photosensitive drums 21K, 21C, 21M, and 21Y.
[0022]
Next, <primary transfer>. When the toner images of the respective colors thus created come to predetermined positions on the intermediate transfer belt 11 by the rotation of the photosensitive drums 21K, 21C, 21M, and 21Y, the photosensitive drums 21K are moved by the primary transfer members 16K, 16C, 16M, and 16Y. , 21C, 21M, and 21Y are applied with a polarity opposite to the charging polarity. As a result, the toner image is transferred to the intermediate transfer belt 11. At this time, the toner images of the respective colors are superimposed on the intermediate transfer belt 11 by being transferred in order from the upstream image forming units 20K, 20C, 20M, and 20Y to the same position of the intermediate transfer belt 11. Next, <secondary transfer>. The toner images of the respective colors superimposed on the intermediate transfer belt 11 are secondarily transferred to the recording medium 32 by the secondary transfer member 31. Furthermore, <fixing / discharging>. The toner image transferred to the recording medium 32 is fixed by the fixing device 33 and discharged as a color print.
[0023]
By the way, at the time of the primary transfer, the toner of the toner images formed on the surfaces of the photosensitive drums 21K, 21C, 21M, and 21Y is not all transferred to the intermediate transfer belt 11, but slightly remains. . When the photosensitive drums 21K, 21C, 21M, and 21Y are further rotated after the primary transfer process and then come into contact with the charging devices 22K, 22C, 22M, and 22Y again, the transfer residual toner is charged due to the potential difference. , 22C, 22M, 22Y. As a result, the surfaces of the photosensitive drums 21K, 21C, 21M, and 21Y are once cleaned.
[0024]
Then, the voltage applied to the charging devices 22K, 22C, 22M, and 22Y is switched in the inter-image process (process 44). Thereby, the transfer residual toner adsorbed to the charging devices 22K, 22C, 22M, and 22Y is discharged to the photosensitive drums 21K, 21C, 21M, and 21Y. Further, the discharged toner is collected by the developing devices 24K, 24C, 24M, and 24Y and reused. Further, the toner remaining on the intermediate transfer belt 11 during the secondary transfer is carried by the intermediate transfer belt 11 and collected by the intermediate transfer belt cleaner 15. The above is the normal sequence.
[0025]
Next, FIG. 4 shows a sequence when a trouble such as a jam occurs during the image forming process (process 43 or process 45). When the abnormality detection unit 4 of the control device 2 detects that a trouble has occurred (step 51), the control of each device is switched to the abnormal operation unit 5. First, the occurrence location is checked (step 52). Depending on where the trouble occurs, the image forming process itself stops immediately, but the rotation of the photosensitive drums 21K, 21C, 21M, 21Y and the intermediate transfer belt 11 does not have to be stopped immediately (pattern A). It is determined whether or not the rotation must be stopped immediately (pattern B). For example, when the recording medium 32 is entangled with the fixing device 33, the next image formation needs to be stopped, but the rotation of the photosensitive drums 21K, 21C, 21M, and 21Y may not be stopped immediately. Here, troubles include all troubles that need to interrupt and stop the image forming process such as charging transformer abnormality and developing bias abnormality in addition to jam.
[0026]
First, the pattern A will be described. In this case, first, the image forming process is stopped (process 61). That is, the steps of <charging><exposure><development><primarytransfer><secondarytransfer><fixing> are interrupted. Then, a cleaning process is performed (process 62). In this cleaning step (step 62), unlike the normal operation, the recovery prohibiting unit 6 prohibits toner recovery to the developing devices 24K, 24C, 24M, and 24Y. Therefore, the control device 2 stops the rotation of the developing rollers 25K, 25C, 25M, and 25Y, or separates the developing rollers 25K, 25C, 25M, and 25Y from the photosensitive drums 21K, 21C, 21M, and 21Y, respectively.
[0027]
Next, the toner discharge unit 7 instructs to discharge toner from the photosensitive drums 21K, 21C, 21M, and 21Y to the intermediate transfer belt 11. Therefore, the control device 2 applies a polarity opposite to the charging polarity of the photosensitive drums 21K, 21C, 21M, and 21Y at that time to the primary transfer members 16K, 16C, 16M, and 16Y. As a result, the toner on the photosensitive drums 21K, 21C, 21M, and 21Y is discharged to the intermediate transfer belt 11.
[0028]
The toner released onto the intermediate transfer belt 11 is carried by the rotation of the intermediate transfer belt 11. Since the secondary transfer process is stopped, the toner is not secondarily transferred to the recording medium 32. Then, it is collected by the intermediate transfer belt cleaner 15. Alternatively, in the image forming apparatus 1 of the present embodiment, since the black image forming unit 20K is arranged on the most downstream side, it is reversely transferred to the photosensitive drum 21K of the image forming unit 20K, and the developing device 24K. You may make it collect | recover. This is because, with the black image forming unit 20K, even if toners of other colors are mixed in, the color tone hardly changes.
[0029]
Thereafter, the machine is stopped (step 63), and a warning is displayed that a trouble has occurred. Therefore, the user clears the trouble by removing the jammed paper (step 64). When it is confirmed that the trouble has been released, the normal sequence is restored (step 65). The pattern A is as described above.
[0030]
Next, the pattern B will be described. In this case, it is necessary to stop the machine first (step 71). This is because depending on the trouble location, if the operation is continued as it is, the photosensitive drums 21K, 21C, 21M, and 21Y may be damaged. In this case, since the cleaning process cannot be performed first, a warning of trouble occurrence is displayed as it is, and the user waits for the trouble to be solved.
[0031]
When the trouble is released (step 72), a cleaning step is performed prior to the pre-operation after the abnormal recovery (step 73). The contents of this cleaning process are the same as the pattern A cleaning process (process 62). That is, first, the rotation of the developing rollers 25K, 25C, 25M, and 25Y is stopped or separated from the photosensitive drums 21K, 21C, 21M, and 21Y. Next, the toner on the photosensitive drums 21K, 21C, 21M, and 21Y is discharged to the intermediate transfer belt 11. The toner on the intermediate transfer belt 11 is collected by the intermediate transfer belt cleaner 15 or is collected by the black developing device 24K. After this cleaning process is completed, the process returns to the normal sequence (process 74). The pattern B is as described above.
[0032]
As described above in detail, the image forming apparatus 1 according to the present embodiment is a cleanerless process, and usually collects transfer residual toner in the developing devices 24K, 24C, 24M, and 24Y. However, when trouble such as a jam occurs, the collection prohibiting unit 6 stops the toner collection operation to the developing devices 24K, 24C, 24M, and 24Y. Further, the toner discharging unit 7 discharges the toner remaining on the photosensitive drums 21K, 21C, 21M, and 21Y onto the intermediate transfer member 11 when a trouble occurs. The toner remaining on the intermediate transfer belt 11 and the discharged toner are collected by the intermediate transfer belt cleaner 15 of the intermediate transfer belt 11 or collected by the black developing device 24K. Therefore, even when the operation is stopped due to a trouble, a stable color image can be formed without causing a change in the color of the toner.
[0033]
Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, in the image forming apparatus 1 of the above-described embodiment, the toner is primarily stored in the charging devices 22K, 22C, 22M, and 22Y, but instead, a dedicated device for primary storage may be provided. As a dedicated device for primary storage, for example, a donor roller can be used. In this case, a non-contact charging type charging device such as a corotron type may be adopted as the charging device instead of the contact charging type charging device.
Further, for example, the image forming apparatus 1 according to the above embodiment is an intermediate transfer type process having the intermediate transfer belt 11, but is a direct transfer type process in which the recording medium 32 is carried on the conveyance belt and directly transferred thereto. There may be.
[0034]
【The invention's effect】
As is apparent from the above description, according to the present invention, there is provided an image forming apparatus capable of forming a stable color image without causing a change in color of the toner even when the operation is stopped due to a trouble. .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment.
FIG. 2 is a block diagram illustrating a schematic system configuration of the image forming apparatus.
FIG. 3 is a process diagram illustrating an operation of a normal image forming apparatus.
FIG. 4 is a process diagram illustrating an operation of the image forming apparatus when a trouble occurs.
[Explanation of symbols]
1 Image forming apparatus 6 Collection prohibition section (collection prohibition means)
7 Toner discharging part (toner discharging means)
11 Intermediate transfer belt (transfer body)
15 Intermediate transfer belt cleaner (collecting means)
20K, 20C, 20M, 20Y Image forming unit 21K, 21C, 21M, 21Y Photosensitive drum (image carrier)
24K, 24C, 24M, 24Y Developer (Developer)

Claims (4)

A plurality of image forming units that perform image formation with toner using a developing device and an image carrier; and a transfer body that sequentially transfers toner images from the plurality of image forming units. In an image forming apparatus that collects toner remaining on an image carrier after transfer to a transfer body in a developing device,
A collection prohibiting means for prohibiting the collection of toner from the image carrier to the developing unit for at least one of the image forming units when an abnormality occurs;
Toner discharging means for discharging toner on the image carrier to the transfer body for each of the image forming units that are targets of the collection prohibiting means when an abnormality occurs ,
A judgment unit for judging whether or not the occurrence location of the abnormality is a location where it is necessary to immediately stop the image carrier of each imaging unit;
The control by the toner discharging means is as follows:
If it is not necessary to stop the determination by the determination unit, it is performed during the period from the occurrence of abnormality to the stop of operation,
The image forming apparatus according to claim 1, wherein when the determination by the determination unit needs to be stopped, the determination is performed during a pre-operation period after the operation is restored . The image forming apparatus according to claim 1,
A collecting means for collecting the toner on the transfer member;
An image forming apparatus, wherein the toner discharged onto the transfer member by the toner discharging means is collected by the collecting means. The image forming apparatus according to claim 1,
The collection prohibiting means and the toner discharging means are intended for the image forming units other than the most downstream in the moving direction of the transfer body,
An image forming apparatus, wherein the toner discharged onto the transfer body by the toner discharging means is collected by an image forming unit located downstream in the moving direction of the transfer body. The image forming apparatus according to claim 3,
The image forming apparatus according to claim 1, wherein the image forming unit at the most downstream side in the moving direction of the transfer body forms a black image.

Images