JP4498339B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, for example, an image forming apparatus such as a copying machine, a printer, and a FAX (facsimile).

  In recent years, image forming apparatuses using an electrophotographic system have been increased in speed, function, and color, and various types of copying machines, printers, and fax machines have been put on the market.

  Among these, image forming units for forming a plurality of different color toner images are juxtaposed in series in the transfer direction of the transfer material carried on the transfer belt as the transfer material carrying member, and the transfer material is transferred from the plurality of image carrying members. An in-line image forming apparatus that sequentially transfers multiple toner images to each other can perform image formation at high speed, and is considered to be the main force in the future. In addition to such an image forming apparatus, an image forming unit for forming a plurality of toner images of different colors is juxtaposed in series in the moving direction of an intermediate transfer belt as an intermediate transfer member, and intermediate transfer is performed from a plurality of image carriers. There has also been proposed a method in which toner images are sequentially transferred onto a belt in a multiple transfer manner, and then the toner images on the intermediate transfer belt are collectively transferred onto a transfer material.

  In such an image forming apparatus, if toner remains on or adheres to the surface of the transfer belt or the intermediate transfer belt, an image defect may occur unless some form of cleaning is performed. A blade that scrapes the toner remaining on and attached to the surface of the transfer belt or intermediate transfer belt against the transfer belt or intermediate transfer belt is scraped off, and the toner that is scraped off is collected in a waste toner tank. A cleaning device has been proposed.

  There has also been proposed an image forming apparatus that is integrally configured as a process cartridge having at least an image carrier, the cleaning device, and the waste toner tank, and that the process cartridge can be attached to and detached from the apparatus main body. This is to make it easier for the user to replace the image carrier when the life of the image carrier has expired. In such an image forming apparatus, when the process cartridge is replaced, the waste toner tank can also be replaced. Therefore, the usability is excellent.

  Further, without providing the cleaning device for scraping off the toner adhering to the transfer belt or the intermediate transfer belt, the toner adhering to the transfer belt or the intermediate transfer belt is applied to one specific image carrier of the plurality of image carriers. There has also been proposed a method in which electrostatic transfer is performed each time and the image is recovered by a cleaning device for the image carrier.

  However, in the image forming apparatus, the toner remaining on and attached to the transfer belt or the intermediate transfer belt has a charge of a normal charge polarity due to the action of a transfer electric field or the like, and has a polarity opposite to the charge polarity. Any toner that remains on or adheres to the transfer belt or intermediate transfer belt can be transferred to the specified image carrier and collected for the reason that there are charged or uncharged. There wasn't. As a result, the backside of the transfer material and image defects may occur.

  Further, in the above-described image forming apparatus using a plurality of image carriers, toner remaining on and attached to the transfer belt or intermediate transfer belt is collected in a waste toner tank of a cleaning device for a specific image carrier. In some cases, the use of the waste toner tank becomes inefficient. That is, the waste toner tank for a specific image carrier is filled up more quickly than the other waste toner tanks for the image carrier, and the replacement of the waste toner tank becomes complicated and the usability is reduced. have done.

  In addition, in an image forming apparatus having a plurality of process cartridges, a specific process is performed before the unused toner stored in a specific process cartridge is completely used up or before the life of the photosensitive drum is reached. The waste toner tank of the cleaning device provided in one of the process cartridges fills up too quickly and it must be replaced with a new process cartridge. Was too fast.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of satisfactorily cleaning toner on a moving body (in the above, a transfer belt or an intermediate transfer belt).

In order to achieve the above object, the present invention according to claim 1 is directed to an endless movable body capable of rotating, a first image carrier that carries a toner image, and a first image carrier on the first image carrier. A first collecting unit that collects toner; a second image carrier that is disposed downstream of the first image carrier in the rotational direction of the moving body and carries a toner image; and the second A second collecting means for collecting toner on the image carrier, and a toner image on the first image carrier on the moving body or a transfer material carried on the moving body at a first transfer position. First transfer means for transferring the image and a toner image on the second image carrier at a second transfer position electrostatically transferred to the movable body or a transfer material carried on the movable body. 2 transfer means, and a residual toner recovery mode for recovering residual toner remaining on the movable body can be executed. In the image forming apparatus, when executing the residual toner collection mode, the polarity of the voltage applied to the second transfer means, by a polarity opposite the polarity of the voltage applied to the first transfer means the direction of the electric field formed in the second transfer position to transfer the toner on the movable body in the second image bearing member, the toner on the movable body in the first image carrier The residual toner that has not been transferred from the moving body to the first image carrier at the first transfer position is opposite to the direction of the electric field formed at the first transfer position for transfer. The polarity of the voltage applied to each of the first transfer unit and the second transfer unit when the toner image is transferred to the first transfer unit and the second transfer unit. Apply a voltage of the same polarity as An image forming apparatus, characterized in that for round the movable body.

The present invention according to claim 2, in the image forming apparatus according to claim 1, wherein the movable body to the first image bearing member and said second image carrier to control the concentration of each of the toner image carrying A density control mode for transferring a test toner image from the first image carrier and the second image carrier, and collecting the test toner image from the moving body after executing the density control mode. For this purpose, the residual toner collecting mode is executed.

  According to the present invention, it is possible to satisfactorily clean the moving body including the residual toner charged to the opposite positive polarity (plus) or the nonpolar residual toner due to the influence of the transfer electric field or the like.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

< Reference Example 1 >
FIG. 1 is a schematic cross-sectional view of a color image forming apparatus using an electrophotographic process. Four independent and detachable units having a photosensitive drum as an image carrier for Y toner, M toner, C toner, and Bk toner, a developing device as developing means, and a cleaning device as collecting means A transfer material in which process cartridges 1, 2, 3, and 4 are juxtaposed and toner images of different colors formed by the process cartridges 1 to 4 are adsorbed to a transfer belt 8 (transfer material carrier) as a moving body. A full-color image is obtained by sequentially superimposing and transferring on P.

  Reference numerals 11, 12, 13, and 14 in FIG. 1 denote rotating drum type electrophotographic photosensitive members (hereinafter referred to as “photosensitive drums”) that are repeatedly used, and have a predetermined peripheral speed (process speed) in the clockwise direction in the drawing. Is driven to rotate.

The photosensitive drums 11 to 14 are uniformly made to have a predetermined polarity and potential (minus in Reference Example 1 ) by primary charging rollers (primary chargers) 21, 22, 23, and 24 as charging means during the rotation process. The image is subjected to charging and then subjected to image exposure by image exposure means 31, 32, 33, 34 (configured by a laser diode, a polygon scanner, a lens group, etc.), whereby the first to first color images of each target color image are obtained. An electrostatic latent image corresponding to four color component images (for example, yellow, magenta, cyan, and black component images) is formed.

  Subsequently, the electrostatic latent image is developed by a developing unit of each image forming station. Each developing sleeve carrying toner in developing devices 41, 42, 43, 44 (yellow, magenta, cyan, black) as developing means for storing toner of each color is indicated by an arrow in the drawing by a rotation driving device (not shown). And is arranged so as to face the photosensitive drums 11 to 14 in the developing process. Then, the toner of each color that is negatively frictionally charged in each developing device and carried on each developing sleeve is electrostatically developed on each photosensitive drum 11 to 14 to form a toner image of each color.

  The transfer belt 8 is rotationally driven at substantially the same peripheral speed as the photosensitive drums 11 to 14 in the direction of the arrow while being in contact with the photosensitive drums 11 to 14.

  The transfer material P fed from the paper cassette is fed toward the suction nip formed by the transfer belt 8 and the suction roller 7 by the registration roller pair 60 at a predetermined timing, and is electrostatically applied to the transfer belt 8. Adsorbed. At this time, in order to electrostatically attract the transfer material P to the transfer belt 8, a predetermined voltage is applied to the attracting roller 7.

The suction roller 7 is formed by molding a solid rubber on a core metal having a diameter of 6 mm, and is configured so that a high pressure bias for suction can be applied to the core metal. The adsorption roller 7 is a solid rubber roller having a diameter of 12 mm in which carbon black is dispersed for resistance adjustment on EPDM rubber. The resistance value when voltage is applied is adjusted to about 10 ⁵ Ω.

  Each time the transfer material P adsorbed to the transfer belt 8 passes through each process cartridge (each image forming station) 1 to 4, toner images of different colors are transferred from the photosensitive drums 11 to 14. The full color toner image is fixed by the fixing device 9 on the transfer material P separated by curvature at the separation position where the transfer belt 8 and the roller 71 come into contact with each other, and is discharged outside the apparatus (outside the image forming apparatus main body).

  After the toner image is transferred from the photosensitive drums 11 to 14 to the transfer material P on the transfer belt 8, the toner remaining on the photosensitive drums 11 to 14 (transfer residual toner) is cleaned by a cleaning device (collecting unit). It is removed and collected by cleaning blades 61, 62, 63 and 64. The collected toner is accumulated in a waste toner tank (waste toner tank) in the cleaning devices 61 to 64.

Hereinafter, a method for collecting the residual toner remaining and adhered on the transfer belt 8 used in Reference Example 1 will be described.

  In order to control the image density, a test toner image formed on the photosensitive drums 11 to 14 is intentionally transferred onto the transfer belt 8, and the density of the test toner image is detected by an optical sensor or the like. The density control mode for controlling the density of the toner image formed on the photosensitive drums 11 to 14 based on the density detection result. Further, when continuous images are formed, fog toner on the photosensitive drums 11 to 14 adheres to the surface of the transfer belt 8 between the two transfer materials P carried on the surface of the transfer belt 8, or the transfer material P is jammed. When the toner adheres due to an accidental cause such as, the toner remains, adheres and forms on the transfer belt 8. For this reason, it becomes a cause of image stains and image defects during subsequent image formation. Such residual, attached, and formed toner (hereinafter referred to as “residual toner”) is collected in a waste toner tank in the cleaning devices 61 to 64 of the process cartridges 1 to 4.

  Further, in the image forming apparatus described above, each color toner image is formed on the transfer material P in a shifted manner, which may cause a change in color. Considering the moving speed of the transfer belt 8 and the distances (N1-N2, N2-N3, N3-N4) between the transfer portions (transfer positions) N1, N2, N3, and N4 of the respective image forming stations on the transfer material P In addition, a mode (hereinafter referred to as “registration control mode”) for detecting registration and preventing misregistration is performed so that transfer is performed at each image forming station at the timing at which the positions of the toner images of the respective colors formed coincide with each other. .

  As a resist detection method, a plurality of lines parallel to the main scanning direction formed on the photosensitive drums 11 to 14 prior to the transfer of the toner image onto the transfer material P are used as a resist detection pattern on the transfer belt 8. Transcript.

  Further, this image forming apparatus is provided with an optical sensor facing the transfer belt 8 to detect the center position of the line of the resist detection pattern. Based on the detection result of the optical sensor, the registration position of each color toner image is controlled by adjusting the writing timing of the latent image on the photosensitive drums 11 to 14 as necessary.

  As described above, since the toner image is transferred onto the transfer belt 8 at the time of registration detection, the transfer belt 8 can be refreshed by performing the above-described cleaning after detection in such a case.

In Reference Example 1 , the amount of remaining toner collected for each operation is switched between the process cartridges 1 to 4 so that the remaining toner can be collected in the waste toner tanks of the cleaning devices 61 to 64 relatively uniformly.

  For example, when a large amount of residual toner is first collected by the process cartridge 1, a large amount is collected by the process cartridge 2 at the next operation, and a large amount is collected by the process cartridge 3 at the next operation. During operation, the process cartridge 4 collects a large amount.

  These controls are possible by controlling the transfer bias to the transfer rollers (transfer members) 51 to 54 as transfer means, the charging bias of the primary charging rollers 21 to 24, and the exposure operation by the image exposure means 31 to 34. is there. When collecting the residual toner, the image exposure means 31 to 34 exposes the photosensitive drums 11 to 14 to approximately 0 V, and a voltage of −1 kV is applied to the transfer rollers 51 to 54. On the other hand, when the remaining toner is not collected, the primary charging rollers 21, 22, 23, and 24 set the potential of the photosensitive drums 11 to 14 to approximately −550 V (the same potential as that during normal image formation), and the transfer roller No voltage is applied to 51-54.

  Thus, by appropriately switching the process cartridge for collecting the residual toner, it is possible to prevent the residual toner from being biasedly collected in the waste toner tank in the cleaning device of the specific process cartridge.

  In the residual toner recovery mode, the recovery of the residual toner is not necessarily limited to one (first) process cartridge among the plurality of process cartridges. There is no problem even if it is carried out with any one of the first, second) or any three (first, second, third) process cartridges.

  For example, when the remaining toner is first collected by the process cartridge 1 and the process cartridge 2, the remaining toner is collected by the process cartridge 2 and the process cartridge 3 at the next operation, and at the next operation, the process cartridge 3 and the process cartridge are collected. 4, the remaining toner is collected by the process cartridge 4 and the process cartridge 1 in the next operation, and the remaining toner is collected again by the process cartridge 1 and the process cartridge 2 in the next operation. Alternatively, it may be controlled by a CPU (control means) 50 as selection means.

  In such a case, in an in-line image forming apparatus having a plurality of process cartridges, the consumption amount of each color toner varies depending on the usage status, and therefore, the process cartridge replacement timing varies due to toner exhaustion. If the process cartridge is replaced due to running out of toner, the waste toner tank may become full when the toner consumption is excessively biased.

  Therefore, for example, an optical sensor is provided as a detection mechanism (detection means) for detecting the amount of waste toner collected in the waste toner tank, and the residual toner is collected in which waste toner tank by the CPU 50 based on the detection result by the detection mechanism. It is even more preferable to select whether or not. With this configuration, only one specific waste toner tank fills up too quickly compared to the other waste toner tanks, and there is still unused toner. It is possible to prevent a specific process cartridge from being replaced.

  As an emergency measure, the remaining toner is not collected in the waste toner tank full of waste toner until the user purchases and replaces the process cartridge, and the remaining toner is collected using the remaining process cartridge. Thus, only a toner image of a specific color can be formed (for example, when the waste toner tank for Y toner is full, a black and white image can be formed). Further, when it is found from the detection result by this detection mechanism that the waste toner tank is full of waste toner, the CPU 50 displays the display unit of the apparatus main body (if the image forming apparatus is a printer, even on the personal computer screen via the connection cable). It is possible to improve usability by displaying an exchange indication to (good) and preventing trouble.

  Further, as a means for determining the process cartridge for collecting the remaining toner, a mechanism for detecting the amount of unused toner in the developing device is not provided, for example, a detection mechanism (detection means) for detecting the amount of unused toner in the developing device. It is also possible to select a process cartridge (photosensitive drum, waste toner tank) that should collect the residual toner on the transfer belt 8 from the detection result of the detection mechanism. When the amount of transfer residual toner that should not be transferred to the transfer material P on the transfer belt 8 and remains on the photosensitive drums 11 to 14 and the amount of residual toner on the transfer belt 8 is compared, Since there are more transfer residual toners to be used, it is possible to correlate the unused toner in the developing unit with the residual toner collected in the waste toner tank. If this correlation value is input to a memory (ROM) in advance, the CPU 50 can select which photosensitive drum the remaining toner should be collected from the detection result of the remaining amount of unused toner.

  Further, a counter (detecting means) capable of counting (detecting) the number of times of image forming operation (number of image forming sheets) is provided in each process cartridge, and the photosensitive member on which the remaining toner on the transfer belt 8 is to be collected from the count value. The drum may be determined by the CPU 50. When the amount of transfer residual toner remaining on the photosensitive drum that should be collected originally and the amount of residual toner on the transfer belt 8 are compared, the amount of transfer residual toner on the photosensitive drum is larger. It is possible to correlate with the amount of toner collected in the waste toner tank. Further, when the count value of each process cartridge exceeds a certain count, the remaining toner on the transfer belt 8 can be prevented from being collected on the photosensitive drum of the process cartridge.

  Further, as another method, the amount of toner used for each color is obtained from the image data (image information) of each color component, and the photosensitive drum (process cartridge) from which the remaining toner on the transfer belt 8 is to be collected is selected from this value. There is a way. When the amount of transfer residual toner on the photosensitive drum to be originally collected and the residual toner on the transfer belt 8 are compared, the amount of toner remaining on the photosensitive drum is larger, so the amount of toner used and the waste toner tank It is possible to correlate with the toner collected inside.

  That is, based on the image data, the CPU 50 selects the photosensitive drum from which the remaining toner on the transfer belt 8 is to be collected. When the integrated value of the used toner amount obtained from the image data exceeds a certain amount, the process cartridge can prevent the remaining toner on the transfer belt 8 from being collected.

  In addition, when a mechanism for detecting the amount of waste toner in the waste toner tank is not provided, some of the above methods may be used in combination.

In Reference Example 1 , the process cartridge that collects the residual toner on the transfer belt 8 is switched using a detection unit that detects the amount of waste toner collected in the waste toner tank of each process cartridge. The meaning of the process cartridge is not limited by this means, and the process cartridge to be collected can be determined by other means.

As described above, in Reference Example 1 , in-line color image forming apparatus using the transfer material carrier (transfer belt 8) prevents residual toner from being biasedly collected in a waste toner tank in a specific process cartridge. There is an advantage that a plurality of waste toner tanks can be effectively used.

<Reference Example 2>
FIG. 2 shows a schematic configuration of the image forming apparatus of Reference Example 2 . This figure is a four-color full-color image forming apparatus having a plurality of image forming stations (process cartridges) arranged in series and provided with an intermediate transfer belt (intermediate transfer body) as a moving body.

  Hereinafter, an outline of the configuration of the image forming apparatus and the image forming process will be described with reference to FIG. Reference numerals 1 to 4 denote developing devices as developing means for Bk toner, M toner, C toner, and Y toner, a photosensitive drum as an image carrier, a charging device as a charging means, and a collecting means. A process cartridge provided with a cleaning device is shown. Image information corresponding to each color component is written as optical information on the surfaces of the photosensitive drums 11 to 14 included in each process cartridge, and an electrostatic latent image is formed. The electrostatic latent images of the respective components are visualized (developed) by developing agents D1 to D4 of the respective colors at the developing unit. The developed toner images on the photosensitive drums are sequentially transferred by primary transfer rollers (transfer means) T1 to T4 at primary transfer portions N1 to N4 where the intermediate transfer belt 5 and the photosensitive drums 11 to 14 are in contact with each other. Is electrostatically transferred to. At the time of toner image transfer, the primary transfer rollers T1 to T4 come into contact with the back surface (inner surface) of the intermediate transfer belt 5 and are applied with a charge (plus) having a polarity opposite to the normal charging polarity of the toner. The full-color toner images on the intermediate transfer belt 5 sequentially transferred at the primary transfer portions (transfer positions) N1 to N4 are secondarily transferred to the transfer material P sent from the registration roller 60 and conveyed at the same timing. After being collectively transferred by the secondary transfer roller (transfer means) T5 at the transfer portion (transfer position) N5, the transfer material P is separated from the intermediate transfer belt 5 by the curvature and conveyed to the fixing device 9 to be heated and heated. It is pressed and fixed.

In the following, a method for collecting the residual, adhered, and formed residual toner on the intermediate transfer belt 5 used in Reference Example 2 will be described.

As in Reference Example 1 described above, when a toner image for detection is transferred onto the intermediate transfer belt 5 as a resist detection pattern for image density control or resist detection, or when a continuous image is formed, When the fog toner on the photosensitive drum adheres between the toner image and the next toner image, or when the toner adheres due to an accidental cause such as a jam of the transfer material P, the toner image is transferred onto the intermediate transfer belt 5. The toner remains, adheres and is formed.

For this reason, an image defect is caused at the time of subsequent image formation. Such residual, adhered, and formed toner (residual toner) is collected in a waste toner tank in the process cartridge as in the first embodiment .

In Reference Example 2 , the amount of remaining toner collected for each operation cartridge is switched for each operation so that the remaining toner can be collected relatively uniformly in the waste toner tanks (collecting means) C1 to C4.

  For example, when a large amount of residual toner is first collected by the process cartridge 1, a large amount is collected by the process cartridge 2 at the next operation, a large amount is collected by the process cartridge 3 at the next operation, and a process is performed at the next operation. A large amount is collected by the cartridge 4, and a large amount is again collected by the process cartridge 1 at the next operation.

  These controls are possible by controlling the transfer bias of the primary transfer rollers T1 to T4, the charging bias of the primary charging rollers 21, 22, 23, and 24, and the exposure operation of the image exposure means. When collecting the residual toner, the potential of the photoconductive drums 11 to 14 is set to approximately 0 V by exposure by the image exposure unit, and a voltage of −1 kV is applied to the primary transfer rollers T1 to T4. On the other hand, when the residual toner is not collected, the potentials of the photosensitive drums 11 to 14 are set to approximately −550 V (potential during normal image formation) by the primary charging rollers 21 to 24 and applied to the primary transfer rollers T1 to T4. No voltage is applied.

  Thus, by appropriately switching the process cartridge for collecting the residual toner, it is possible to prevent the residual toner from being biasedly collected in the waste toner tank in the cleaning device of the specific process cartridge.

  In the residual toner collection mode, the collection of the residual toner is not necessarily limited to one process cartridge, and there is no problem even if the collection of the residual toner is performed with two or three process cartridges.

  For example, when the remaining toner is first collected by the process cartridge 1 and the process cartridge 2, the remaining toner is collected by the process cartridge 2 and the process cartridge 3 at the next operation, and at the next operation, the process cartridge 3 and the process cartridge are collected. 4, the remaining toner is collected by the process cartridge 4 and the process cartridge 1 in the next operation, and the remaining toner is collected again by the process cartridge 1 and the process cartridge 2 in the next operation. Alternatively, it may be controlled by the CPU 50.

As the intermediate transfer belt 5 used here, a polyimide resin film is used, and a single-layer structure having a volume resistance value of about 10 ⁹ Ω · cm and a thickness of 150 μm is used.

  In the case of the configuration as described above, in an inline type image forming apparatus having a plurality of image forming stations (process cartridges), the amount of consumption of each color toner varies depending on the use state, and therefore, the process cartridge replacement timing varies due to running out of toner. . If the process cartridge is replaced due to running out of toner, the waste toner tank may become full when the toner consumption is excessively biased.

  Therefore, as a detection mechanism (detection means) for detecting the amount of waste toner collected in the waste toner tank, for example, an optical sensor is provided, and based on the detection result by this detection mechanism, the CPU 50 as the control means stores in which waste toner tank. It is even more preferable to select whether to collect the toner. With this configuration, only one specific waste toner tank fills up too quickly compared to the other waste toner tanks, and there is still unused toner. It is possible to prevent a specific process cartridge from being replaced.

  As an emergency measure, the remaining toner is not collected in the waste toner tank full of waste toner until the user purchases and replaces the process cartridge, and the remaining toner is collected using the remaining process cartridge. Thus, only a toner image of a specific color can be formed (for example, when the waste toner tank for Y toner is full, a black and white image can be formed). Further, when it is found from the detection result by this detection mechanism that the waste toner tank is full of waste toner, the CPU 50 displays the display unit of the apparatus main body (if the image forming apparatus is a printer, even on the personal computer screen via the connection cable). It is possible to improve usability by displaying an exchange indication to (good) and preventing trouble.

  Further, as a means for determining the process cartridge for collecting the remaining toner, a mechanism for detecting the amount of unused toner in the developing device is not provided, for example, a detection mechanism (detection means) for detecting the amount of unused toner in the developing device. It is also possible to select a process cartridge (photosensitive drum, waste toner tank) from which the remaining toner on the intermediate transfer belt 5 is to be collected from the detection result of the detection mechanism. When the amount of transfer residual toner that should not be transferred onto the intermediate transfer belt 5 and remains on the photosensitive drums 11 to 14 is compared with the amount of residual toner on the intermediate transfer belt 5, it should be recovered originally. Since there is more transfer residual toner, it is possible to correlate the unused toner in the developing unit and the residual toner collected in the waste toner tank. If this correlation value is input to a memory (ROM) in advance, the CPU 50 can select which photosensitive drum the remaining toner should be collected from the detection result of the remaining amount of unused toner.

  Further, a counter (detecting means) capable of counting (detecting) the number of times of image forming operation (number of images formed) is provided in each process cartridge, and the photosensitive toner for collecting the remaining toner on the intermediate transfer belt 5 from the count value. The body drum may be determined by the CPU 50. When the amount of transfer residual toner remaining on the photosensitive drum that should be collected originally is compared with the amount of residual toner on the intermediate transfer belt 5, the amount of primary transfer residual toner on the photosensitive drum is larger. The count value and the amount of toner collected in the waste toner tank can be correlated. Further, when the count value of each process cartridge exceeds a certain count, the remaining toner on the intermediate transfer belt 5 may not be collected on the photosensitive drum of the process cartridge.

  Further, as another method, the amount of toner used for each color is obtained from the image data of each color component, and the CPU 50 selects a photosensitive drum (process cartridge) from which the remaining toner on the intermediate transfer belt 5 is to be collected based on this value. There is. When comparing the amount of residual toner on the photosensitive drum that should be collected with the residual toner on the intermediate transfer belt 5, the amount of residual toner on the photosensitive drum is larger. A correlation can be made with the toner collected in the tank.

  That is, the photosensitive drum on which the remaining toner on the intermediate transfer belt 5 is to be collected is selected based on the image data (image information). When the integrated value of the used toner amount obtained from the image data exceeds a certain amount, the process cartridge can prevent the remaining toner on the intermediate transfer belt 5 from being collected.

  In addition, when a mechanism for detecting the amount of waste toner in the waste toner tank is not provided, some of the above methods may be used in combination.

In Reference Example 2 , the process cartridge that collects the remaining toner on the intermediate transfer belt 5 is switched using a detection unit that detects the amount of waste toner collected in the waste toner tank of each process cartridge. However, the purpose is not limited by this means, and the process cartridge to be collected can be determined by other means.

As described above, in Reference Example 2 , in-line color image forming apparatus using the intermediate transfer member (intermediate transfer belt 5) prevents residual toner from being biasedly collected in the waste toner tank in a specific process cartridge. There is an advantage that a plurality of waste toner tanks can be effectively used.

< Embodiment 1 >
In the reference example 1 described above, it is assumed that the charging polarity of most of the residual toner on the transfer belt 8 is negative (minus). There are cases where charged and nonpolar ones may exist, and the purpose of this embodiment is to satisfactorily clean even residual toner having such a negative polarity.

  FIG. 3 shows an image forming apparatus according to the present embodiment. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and the duplication description shall be abbreviate | omitted suitably.

  In the present embodiment, the residual toner on the transfer belt 8 is collected in a waste toner tank in at least two image forming stations (process cartridges). That is, the cleaning electric fields for transferring the residual toner onto at least two photosensitive drums are opposite to each other.

  Hereinafter, collection of residual toner in the present embodiment will be described in detail.

  First, the sub-cleaning bias (plus) having the same polarity as the polarity (plus) at the time of transfer to the transfer roller 51 in the most upstream process station (image forming station, process cartridge) 1 along the rotation direction of the transfer belt 8. Is applied from the power source 101, and the residual toner having the opposite polarity (plus) is attracted to the photosensitive drum 11 and collected in the waste toner tank (cleaning device 61) in the process station 1, and the transfer belt 8 is also collected. The remaining toner on top is charged to normal polarity (minus).

  Next, in the process station 2, a main cleaning bias (minus) having a polarity (minus) opposite to the polarity (plus) at the time of transfer is applied to the transfer roller 52 by switching a switch 102 a in the power source 102. The normal polarity (minus) toner that has passed through the process station 1 is transferred to the photosensitive drum 12 of the process station 2 and collected in a waste toner tank (cleaning device 62) in the process station 2. At this stage, toner is almost collected. However, when the amount of residual toner is large, it may not be possible to collect all normal polarity (minus) toner at the process station 2. The toner remaining on the transfer belt 8 without being collected at the process station 2 remains in the opposite polarity (plus), nonpolarity, or normal polarity (minus) when passing through the process station 2.

  Also in the process station 3, the switch 103a in the power source 103 is switched, and a main cleaning bias (minus) is applied to the transfer roller 53, whereby residual toner that has not been transferred to the photosensitive drum 12 in the process station 2 is processed. The toner is transferred to the photosensitive drum 13 of the station 3 and collected in a waste toner tank (cleaning device 63) in the process station 3. As a result, the remaining toner of normal polarity (minus) is almost recovered and is not transferred to the photosensitive drum 13 because of the small amount of charge although it is of opposite polarity (plus), nonpolar, or normal polarity (minus). The toner on the transfer belt 8 is charged to the opposite polarity (plus). As described above, since most of the remaining toner has already been collected in the process stations 1 to 3, there is no residual toner on the transfer belt 8, but in rare cases it may remain.

  Further, in the process station 4, a sub cleaning bias (plus) is applied to the transfer roller 54 by the power source 104, and the toner of the opposite polarity (plus) that has passed without being transferred in the process station 3 is transferred to the photosensitive member of the process station 4. The toner is transferred onto the drum 14 and collected in a waste toner tank (cleaning device 64). Thereby, the toner cleaning on the transfer belt 8 is completed.

  As described above, a process station in which the cleaning bias applied to the transfer rollers 51 to 54 of the process stations 1 to 4 is the sub-cleaning bias (plus) having the same polarity (plus) as the polarity (plus) at the time of transfer, By having a process station having a main cleaning bias (minus) that is opposite (minus) to the polarity at transfer (plus), the normal polarity (minus) and the opposite polarity (plus) of the surface of the transfer belt 8 are present. The remaining toner can be collected in a waste toner tank (cleaning devices 61 to 64) in each of the process stations 1 to 4, and the remaining toner can be cleaned and collected by only one rotation (one rotation) of the transfer belt 8. It can be terminated.

  According to the present embodiment, it is possible to collect the residual toner on the transfer belt 8 in a short time (only the transfer belt 8 makes one round).

  Further, it is possible to suppress the abrasion of the photosensitive drums 11 to 14 by the cleaning blade and the transfer belt 8 and the deterioration of the toner in the developing sleeve and the developing device as compared with the case where the transfer belt is rotated a plurality of times for cleaning. It became.

  In this embodiment, the toner charging polarity is negative, the sub-cleaning bias having the same polarity as the transfer polarity is set to +1 kV, and the main cleaning bias having the opposite polarity to the transfer polarity is set to -2 kV.

  When the sub-cleaning bias and the main cleaning bias are applied, the surface of the photosensitive drum is charged by the primary charging rollers 21 to 24 (to the same potential (dark portion potential) as that during normal image formation). The residual toner is transferred to the surface. When the main cleaning bias is applied, the CPU is configured so that the potential on the surface of the photosensitive drum becomes a bright portion potential (exposure portion potential) whose absolute value is lower than the potential at the time of normal image formation by the image exposure means, or zero potential. It may be controlled by. By doing so, the absolute value of the main cleaning bias can be reduced, the enlargement of the power source can be prevented, and the cost can be reduced.

  In the above description, the cleaning bias applied from the power sources 101 to 104 to the transfer rollers 51 to 54 when cleaning the transfer belt 8 is the sub cleaning bias, the main cleaning bias, the main cleaning bias, and the sub cleaning bias in order from the upstream. ing.

  The cleaning bias applied to at least one of the transfer rollers 51 to 54 may be a main cleaning bias, and the other may be a sub cleaning bias.

Therefore, in order from the upstream side (in order of process stations 1 to 4),
・ Sub-cleaning bias, main cleaning bias,
Sub-cleaning bias, main cleaning bias / sub-cleaning bias, main cleaning bias,
Sub-cleaning bias, sub-cleaning bias / sub-cleaning bias, main cleaning bias,
Main cleaning bias, main cleaning bias / sub-cleaning bias, sub-cleaning bias,
Main cleaning bias, main cleaning bias / sub-cleaning bias, sub-cleaning bias,
Sub-cleaning bias, main cleaning bias / sub-cleaning bias, sub-cleaning bias,
A main cleaning bias or a sub-cleaning bias may be used.

If the main cleaning bias and the sub-cleaning bias are mixed, among the above combinations, for example,
・ Sub-cleaning bias, no cleaning bias,
There may be a combination in which there is a process station to which no cleaning bias is applied, such as a main cleaning bias and no cleaning bias.

Further, as an example different from the image forming apparatus shown in FIGS. 4 and 5, the bias applied in the order of the transfer rollers 51 to 54 is:
・ Main cleaning bias, sub-cleaning bias,
Main cleaning bias, Main cleaning bias / Main cleaning bias, Main cleaning bias,
Main cleaning bias, sub-cleaning bias / main cleaning bias, sub-cleaning bias,
Sub-cleaning bias, main cleaning bias / main cleaning bias, main cleaning bias,
Sub-cleaning bias, sub-cleaning bias / main cleaning bias, sub-cleaning bias,
A sub cleaning bias or a sub cleaning bias may be used.

If the main cleaning bias and the sub-cleaning bias are mixed, among the above combinations, for example,
・ Main cleaning bias, no cleaning bias,
There may be a combination in which there is a process station to which no cleaning bias is applied, such as no sub-cleaning bias and no cleaning bias.

  In the developing unit, the toner can be given a constant charge. However, a small amount of toner (ground fog toner) that cannot be sufficiently charged or toner whose polarity is reversed (reversed toner) may be generated.

  Such toner adheres to the Vd portion (non-image portion, dark portion potential portion) of the photoreceptor drums 11 to 14 charged by the primary charging rollers 21 to 24 as fog toner, and the photoreceptor drums 11 to 14. Stick on top.

  When the toner is transferred to the transfer material P, the transfer bias is positive, so that the reverse toner (plus) is not transferred to the transfer material P even if it adheres on the photosensitive drums 11 to 14. However, the ground fog toner (minus) is transferred to the transfer material P if it adheres to the photosensitive drums 11 to 14.

  Therefore, it is preferable to adopt a configuration in which the ground fog toner hardly adheres. For this purpose, there are measures such as increasing the potential difference (back contrast) between the Vd portion and the developing sleeve. However, in this configuration, the ground fog toner hardly adheres to the photosensitive drums 11 to 14, but the reverse toner easily adheres to the photosensitive drums 11 to 14.

  With such a configuration, when the transfer belt 8 is cleaned with the main cleaning bias in a system in which the reverse toner easily adheres to the photosensitive drums 11 to 14, a small amount of the reverse toner is transferred onto the transfer belt 8. .

  Therefore, in a system in which fog toner is generated, cleaning to be applied to the transfer rollers 51 to 54 after cleaning by the main cleaning bias and the sub cleaning bias described above (at least after the transfer belt 8 is cleaned for one week). Occurs when cleaning is performed by applying the main cleaning bias when the bias is changed to the sub-cleaning bias having the same polarity as that at the time of transfer (plus) and the cleaning process (at least for one week of the transfer belt 8) is completed. The reversal fog toner to be recovered can be collected from the transfer belt 8 and can be transferred to the next transfer step.

As described above, in this embodiment, the residual toner on the transfer belt 8 can be satisfactorily cleaned, and should be collected in the photosensitive drum (waste toner tank of the cleaning device) as in Reference Example 1 described above. By controlling the amount of residual toner on the transfer belt 8, usability can be improved when replacing the process cartridge.

  In the present embodiment, the example applied to the image forming apparatus having the transfer belt 8 has been described. However, the present invention is not limited to this. For example, as shown in FIG. It can be similarly applied to. For example, in FIG. 6, when cleaning the residual toner on the intermediate transfer belt 5, the sub-cleaning bias, the main cleaning bias, the main cleaning bias, and the sub-cleaning bias are supplied to the power sources 201 to 204 in the order of the primary transfer rollers T1 to T4. The example which applies more is shown.

  Furthermore, in the present embodiment, the amount of residual toner (including zero) transferred from the transfer belt 8 or the intermediate transfer belt 5 to the photosensitive drum is set to the transfer rollers 51 to 54 or the primary transfer rollers T1 to T4 and the photosensitive member. You may control by controlling the magnitude | size of the electric field formed between the drums 11-14.

< Reference Example 3 >
In contrast to the reference example 1 described above, the reference example 3 is characterized in that the residual toner on the transfer belt 8 is charged in advance by the charging device 10 as shown in FIG.

  The residual toner remaining on the transfer belt 8 after the transfer process includes a part of the toner whose charge polarity is reversed or whose charge amount is reduced.

Therefore, in order to collect the toner (residual toner) remaining, adhered and formed on the transfer belt 8, the remaining toner on the transfer belt 8 is charged to a predetermined polarity ( reference example 3 ) by the charging device (charging roller) 10. Will be positively charged). Here, the charging device 10 is applied with an alternating voltage obtained by superimposing the DC voltage and the AC voltage, and is charged to a polarity opposite to the normal charging polarity (minus in Reference Example 3 ) of the toner in the developing device. Specifically, the DC component is applied so that the intermediate value of the peak-to-peak voltage is approximately 0 V to the AC component of the peak-to-peak voltage Vpp = 2.5 kV, frequency 2000 Hz, duty ratio 80% positive polarity, 20% negative is doing. Due to this AC component, the residual toner reciprocates in the gap portion between the transfer belt 8 and the charging device 10 and is more uniformly reversely charged. The residual toner charged to the opposite polarity is conveyed to the transfer portions (primary transfer nips) N1 to N4, and reversely transferred to the photosensitive drums 11 to 14 by the transfer rollers 51 to 54 to which a predetermined voltage (plus voltage) is applied. It can be copied. Thereafter, the remaining toner is removed by the cleaning devices 61 to 64 and accumulated in a waste toner tank in the cleaning device.

In this way, by charging the residual toner on the transfer belt 8 in advance, it is possible to control and grasp the amount of residual toner that is reversely transferred to each photosensitive drum more accurately.
That is, the amount of residual toner collected in the waste toner tank for each photosensitive drum can be controlled and grasped.

  Further, the present invention can be similarly applied to an image forming apparatus having the intermediate transfer belt 5 shown in FIG.

  Details will be described below.

  After the secondary transfer, the secondary transfer residual toner remaining on the intermediate transfer belt (intermediate transfer member) 5 is conveyed to the charging device 10 (recharging roller), where the alternating voltage is obtained by superimposing the DC voltage and the AC voltage. Is charged to a polarity (plus) opposite to the normal charging polarity of the toner in the developing device. The charged residual toner is conveyed to a transfer portion (nip portion) N1 between the photosensitive drum 11 and the intermediate transfer belt 5, and a predetermined voltage (with a polarity opposite to the normal charging polarity of the toner) is applied to the transfer roller T1. By applying (plus), the toner image is transferred to the photosensitive drum 11 and collected by the waste toner tank (cleaning device) C1 and stored in the waste toner tank. At this time, the surface potential of the photosensitive drum 11 is 0 V (bias off by the charging roller 21).

  Here, cleaning of the residual toner on the intermediate transfer belt 5 will be described. When the toner is transferred from the intermediate transfer belt 5 to the transfer material P, the secondary transfer residual toner on the intermediate transfer belt 5 receives an electric field having a polarity opposite to the normal charging polarity of the toner and is charged to the opposite polarity. There is also toner remaining on the intermediate transfer belt 5.

  However, not all residual toners are charged to the opposite polarity, and there are toners that are partially neutralized and have no charge, and toners that maintain normal polarity. Therefore, a bias obtained by superimposing the AC component of the peak-to-peak voltage Vpp on the DC component is applied to the charging device 10 provided after the secondary transfer. Specifically, the DC component is set so that the intermediate value of the peak-to-peak voltage is approximately 0 V to the AC component of the peak-to-peak voltage Vpp = 2.5 kV, the frequency 2000 Hz, the duty ratio is 80% on the positive polarity side, and 20% on the negative polarity side. Applied. Due to this AC component, the secondary residual toner reciprocates in the gap portion between the intermediate transfer belt 5 and the roller member of the charging device 10, and the secondary transfer residual toner charged more uniformly with a reverse polarity is transferred to the transfer portions N1 to N1. After being transferred to N4 and reversely transferred to the photosensitive drum side of the process cartridge selected by the CPU, it is removed by the cleaning device and accumulated in a waste toner tank in the cleaning device.

  In this way, by charging the residual toner on the intermediate transfer belt 5 in advance, it is possible to control and grasp the amount of residual toner that is reversely transferred to each photosensitive drum more accurately. That is, the amount of residual toner collected in the waste toner tank for each photoconductor drum can be controlled and grasped, and the residual toner is favorably prevented from being biased to a specific waste toner tank. Can do.

In the above first embodiment and reference examples 1 to 3 , the process cartridge is configured by integrating the photosensitive drum, the primary charger, the developer, and the cleaning device (waste toner tank and cleaning blade). Has been described with respect to an example in which the image forming apparatus main body is detachable. An example is shown in FIG. This is a longitudinal sectional view showing details of the image forming station (process station) 1 in FIG. With such a configuration, it is possible to easily perform replacement work due to the life of the photosensitive drum or running out of toner.

  The process cartridge may have at least a photosensitive drum and a cleaning device.

  The present invention is not limited to the above description, and various modifications can be made within the scope of the technical idea of the present invention.

  As described above, according to the present invention, it is possible to prevent residual toner from being biasedly collected in a waste toner tank in a specific process cartridge, and to effectively use a plurality of waste toner tanks. In addition, since both the normal polarity toner and the reverse polarity toner on the moving body can be reversely transferred to the image carrier, efficient cleaning can be performed.

2 is a schematic cross-sectional view of an image forming apparatus according to Reference Example 1. FIG. FIG. 4 is a schematic cross-sectional view of an image forming apparatus according to Reference Example 2 . 1 is a schematic cross-sectional view of an image forming apparatus according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to Embodiment 1. FIG. FIG. 10 is a schematic cross-sectional view of an image forming apparatus according to Reference Example 3 . FIG. 10 is a schematic cross-sectional view of an image forming apparatus according to Reference Example 3 . FIG. 3 is a schematic cross-sectional view of an image forming station (process station).

Explanation of symbols

1, 2, 3, 4 Process cartridge (image forming station, process station)
11, 12, 13, 14 Image carrier (photosensitive drum)
5 Moving body (intermediate transfer body, intermediate transfer belt)
8 Moving body (transfer material carrier, transfer belt)
21, 22, 23, 24 Charging means (primary charger, primary charging roller)
31, 32, 33, 34 Exposure means (image exposure means)
41, 42, 43, 44 Development means (developer)
50 selection means (control means, CPU)
51, 52, 53, 54 Transfer means (transfer member, transfer roller)
61, 62, 63, 64 Recovery means (cleaning device)
C1, C2, C3, C4 recovery means (waste toner tank)
N1, N2, N3, N4 Transfer position (primary transfer part, transfer nip)
N5 transfer position (secondary transfer part)
P transfer material T1, T2, T3, T4 transfer means (primary transfer roller)
T5 transfer means (secondary transfer roller)

Claims (2)

An endless movable body capable of rotating,
A first image carrier for carrying a toner image;
First collecting means for collecting toner on the first image carrier;
A second image carrier that is disposed downstream of the first image carrier in the rotational direction of the movable body and carries a toner image;
Second collecting means for collecting toner on the second image carrier;
First transfer means for electrostatically transferring a toner image on the first image carrier to the moving body or a transfer material carried on the moving body at a first transfer position;
A second transfer means for electrostatically transferring the toner image on the second image carrier to the moving body or a transfer material carried on the movable body at a second transfer position;
In an image forming apparatus capable of executing a residual toner recovery mode for recovering residual toner remaining on the moving body,
When executing the residual toner recovery mode, the polarity of the voltage applied to the second transfer unit is set to be opposite to the polarity of the voltage applied to the first transfer unit, thereby The direction of the electric field formed at the second transfer position for transferring the toner of the toner to the second image carrier is the same as the direction of the electric field formed at the second transfer position for transferring the toner on the movable body to the first image carrier. The residual toner that has not been transferred from the movable body to the first image carrier at the first transfer position is set to be opposite to the direction of the electric field formed at the first transfer position. A voltage having the same polarity as the polarity of the voltage applied to each of the first transfer unit and the second transfer unit when the toner image is transferred to the first transfer unit and the second transfer unit. the applied is around at least the mobile An image forming apparatus comprising and. In order to control the density of each toner image carried on the first image carrier and the second image carrier, a test toner image is transferred to the movable body on the first image carrier and the second image carrier. It has a density control mode to transfer from the image carrier,
The image forming apparatus according to claim 1, characterized in that to perform said residual toner recovery mode for recovering the test toner image from said moving body after performing the density control mode.

Images