JP4040611B2 - Image forming apparatus - Google Patents

Description

  The present invention is a transfer that develops an electrostatic latent image formed on an image carrier such as a photosensitive drum and transfers it onto a recording material (media) via an intermediate transfer member, such as a color copying machine or a color printer. The present invention relates to a color image forming apparatus that forms an image through processes.

  Conventionally, a color image forming apparatus, particularly electrophotographic, further has a photosensitive drum as a plurality of image carriers, and forms developer images (toner images) of different colors on the photosensitive drum. A tandem method for superimposing color images is known. In the image forming process, first, a photosensitive drum as an image carrier is uniformly charged by a charging device, and an electrostatic latent image is formed by a laser or LED. The process until the electrostatic latent image is developed with a developer (toner) is performed for each color photosensitive drum of, for example, magenta, cyan, yellow, and black. In the direct transfer method, the image is directly superimposed on a recording material carried on a transfer body that moves to face each photosensitive drum and fixed by heat. In the intermediate transfer method, which is a method for widely selecting a recording material, Each formed color toner image is superimposed on an intermediate transfer member, which is a transfer member that moves opposite to the photosensitive drum, and is collectively transferred from the intermediate transfer member to a recording material such as paper, and fixed by heat. As the intermediate transfer member, a belt-like intermediate transfer belt having a high degree of freedom in the image forming apparatus is often used from the viewpoint of space saving.

  In this process, the toner remaining on the photosensitive drum is collected by a photosensitive drum cleaning device provided around the photosensitive drum. The toner remaining on the intermediate transfer belt is removed by an intermediate transfer belt cleaning device (intermediate transfer member cleaning device) provided around the intermediate transfer belt.

  In recent years, in order to improve the image quality of color image forming devices, a conductive elastic layer made of urethane rubber, silicon rubber, etc. has been formed on the base layer as a material for the intermediate transfer belt, and the surface layer is made of fluorine resin, etc. An apparatus having a so-called elastic intermediate transfer belt is presented.

  The first advantage of the elastic intermediate transfer belt is that the toner image is not lost due to toner aggregation during the primary transfer of transferring the toner image on the photosensitive drum to the intermediate transfer belt. Is mentioned.

  Second, in recent years, color image forming apparatuses are required to support various recording materials, and secondary transfer for transferring a toner image from an intermediate transfer belt to a recording material on a recording material having a rough surface. At the nip portion, the intermediate transfer belt that sandwiches the toner image and the surface of the recording material become familiar with each other due to elastic characteristics, and good transfer is performed.

  On the other hand, as a cleaning means for the intermediate transfer member, for example, a blade cleaning method (see, for example, Patent Document 1) in which a blade is brought into contact with the intermediate transfer member and toner is scraped off, or a bias is applied to a conductive fur brush. Then, a conductive brush cleaning method is disclosed in which the toner is recovered by the potential difference generated between the intermediate transfer member and the fur brush.

  However, the blade cleaning method has a problem that residual toner slips through due to the surface roughness of the elastic intermediate transfer belt, and sufficient cleaning cannot be performed.

Further, the conductive brush cleaning method has a restriction on the amount of toner image on the intermediate transfer belt. In other words, the job is stopped while the toner image that has not been transferred to the recording material remains on the intermediate transfer belt due to, for example, a jam, instead of a small amount of cleaning such as the residual toner after transfer to the recording material. In the subsequent cleaning, since a large amount of toner cannot be collected at one time, it is necessary to perform cleaning by rotating the intermediate transfer belt many times during the previous rotation. Therefore, there is a problem that it takes time for the recovery process.
JP-A-4-60569

  An object of the present invention is to provide a sufficient intermediate in a short time even when a large amount of developer remains on an intermediate transfer member in an image forming apparatus using an elastic belt as an intermediate transfer member that moves to face an image carrier. An object of the present invention is to provide an image forming apparatus that performs transfer body cleaning.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the first aspect of the present invention provides a plurality of image carriers, electrostatic latent image forming means for forming an electrostatic latent image on the image carrier based on an image signal based on image information, and on the image carrier. A developing means for developing the electrostatic latent image formed on the toner image, and a toner image; an intermediate transfer member that moves to face the plurality of image carriers and from which the toner image is transferred; An image carrier cleaning device that removes and collects toner on the surface of the image carrier, an intermediate transfer member cleaning device that removes and collects toner on the surface of the intermediate transfer member, and a density of the toner image transferred to the surface of the intermediate transfer member And an image forming apparatus having a means for detecting that the image forming operation has ended abnormally ,
When it is detected that the image forming operation has ended abnormally, the toner remaining on the surface of the intermediate transfer member is removed and collected upon return according to the detected density of the toner image on the surface of the intermediate transfer member. The intermediate transfer member cleaning device is used alone, or the intermediate transfer member cleaning device removes and collects the toner, and at the same time, applies an electric field to all the image carriers to move the toner from the intermediate transfer member to the image carrier. Determining whether to perform the operation of removing and collecting the moved and moved toner by the image carrier cleaning device;
When performing an operation of moving toner from the intermediate transfer member to the image carrier, an image forming apparatus is provided that individually controls the amount of toner to be moved to each of the image carriers.

According to a second aspect of the present invention, a plurality of image carriers, an electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier by an image signal based on image information, and the image carrier are formed on the image carrier. Developing means for developing an electrostatic latent image to form a toner image, an intermediate transfer member that moves opposite to the plurality of image carriers and transfers the toner image from the image carrier, and the image carrier an image bearing member cleaning device for removing collected toner surface, the intermediate transfer member cleaning device for removing collected toner on the intermediate transfer member surface, a video count unit for counting the number of the image signals, the image forming operation is abnormal And an image forming apparatus having means for detecting completion
The intermediate transfer member upon return according to the number of image signals of the toner image formed on the image carrier counted by the video counting means when it is detected that the image forming operation has ended abnormally The toner remaining on the surface is removed and collected only by the intermediate transfer member cleaning device, or the intermediate transfer member cleaning device removes and collects the toner and moves the toner from the intermediate transfer member to the image carrier. An electric field is formed on all the image carriers , and it is determined whether to move and remove the moved toner by the image carrier cleaning device, and the toner is moved from the intermediate transfer member to the image carrier. When the operation is performed, an image forming apparatus is provided in which the amount of toner moved to each of the image carriers is individually controlled.

According to the image forming apparatus of the present invention, even when cleaning a large amount of toner images transferred to the surface of the intermediate transfer member, sufficient intermediate transfer member cleaning can be completed in a short time, and a plurality of image carriers can be recovered. Since the amount can be collected so as not to be biased, the cleaning performance of the image carrier cleaning device can be maintained.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a full-color copying machine which is an example of a tandem type intermediate transfer type electrophotographic image forming apparatus.

  This image forming apparatus is broadly divided into a digital color image reader unit (reader unit) 200 and a digital color image printer unit (printer unit) 201 provided under the digital color image reader unit 200.

  The reader unit 200 takes in image information from the outside and converts it into an image signal.

  That is, in the reader unit 200, the document is placed on the document table glass 211, and the document scanning unit 215 including the exposure lamps 213 and 214 is exposed and scanned at a predetermined constant speed by the optical system reading drive motor 212. An operation unit 900 (FIG. 4), which will be described in detail later, is provided around the platen glass 211, and switches for setting various modes related to a copying sequence, a display for display, and a display are arranged. Then, the reflected light image from the original is condensed on a full color sensor (CCD) 217 by a lens 216 to obtain a color separation image signal. As the full-color sensor 217, a three-line CCD with R (red), G (green), and B (blue) filters disposed adjacent to each other is used. The color separation image signal thus obtained is subjected to image processing by the image processing unit 805 and then transmitted to the printer unit 201.

  The printer unit 201 executes the image forming process according to the image signal transmitted from the reader unit 200.

  In the printer unit 201, the control unit 800 is a controller unit, which includes a controller board including a CPU 801, a RAM 803, a ROM 802, and the like (FIG. 3), and executes image formation based on a control program stored in the ROM 802. Controls overall operations of the image forming means provided in the image forming unit having the image bearing member (photosensitive drum), the paper feeding unit, the intermediate transfer unit, the conveying unit for conveying the recording material, the fixing unit, and the operation unit. ing.

  Since the image forming apparatus of this embodiment is a tandem type, it has a plurality of photosensitive drums as image carriers according to the number of colors of the developer to be used, and an image forming section is provided for each photosensitive drum.

  Each image forming unit is configured as described below. In this embodiment, yellow (Y), magenta (M), cyan (C), and black (Bk) developer images (toner images) are formed as image carriers, respectively. 11a, 11b, 11c, and 11d) are pivotally supported at the center, and are rotationally driven in the direction of the arrow by a drive motor (not shown). A roller charger 12 (12a, 12b, 12c, 12d) as a charging unit and a scanner 13 (13a, 13b, 13c, 13d) as an exposure unit in the rotation direction facing the outer peripheral surface of the photosensitive drum 11, A developing device 14 (14a, 14b, 14c, 14d) as a developing unit and a photosensitive drum cleaning device (image carrier cleaning device) 15 (15a, 15b, 15c, 15d) are arranged, and each photosensitive drum 11 has an image. The forming part S (Sa, Sb, Sc, Sd) is configured. Each image forming unit S faces the belt surface on which the endless intermediate transfer belt 30 provided as the intermediate transfer member moves, and the upstream side along the moving direction of the belt 30. The image forming units Sa, Sb, Sc, and Sd are arranged in this order from the downstream side.

  In each image forming unit S, the roller charger 12 applies a uniform charge amount to the surface of the photosensitive drum 11. Next, a light beam such as a laser beam modulated according to the recording image signal is exposed on the photosensitive drum 11 by the scanner 13 to form an electrostatic latent image thereon. That is, in this embodiment, the roller charger 12 as the charging unit and the scanner 13 as the exposure unit are configured as an electrostatic latent image forming unit. Further, the electrostatic latent images are visualized by the developing devices 14a, 14b, 14c, and 14d containing the four color developers (toners) by the image forming units S such as black, cyan, magenta, and yellow, respectively. An image (toner image) is used. The visualized visible image is transferred onto the intermediate transfer belt 30 in an overlapping manner as the belt 30 moves. Thereafter, the residual toner remaining on the photosensitive drum 11 is removed and collected (cleaned) by the photosensitive drum cleaning device 15. Through the image forming process described above, image formation with toner is sequentially performed on the photosensitive drum 11 in each image forming unit S.

  Next, the paper feed unit detects the cassette 21, the manual feed tray 27, and the deck 28, which are portions for storing the recording material P, various rollers for conveying the recording material P described below, and the passage of the recording material P. A sensor for detecting the presence or absence of the recording material P, and a guide (not shown) for transporting the recording material P along the transport path.

  The recording material P is fed from the cassette 21, the manual feed tray 27, and the deck 28 by the pickup rollers 22, 29, 60 one by one from the top.

  A plurality of recording materials P may be sent out by the pickup roller 22 of the cassette 21, but only one sheet is reliably separated by the BC roller 23 installed in the vicinity thereof. The recording material P separated by only one sheet by the BC roller 23 is further transported by the drawing roller 24 and the pre-registration roller 26 and is transported to the registration roller 25. The recording material P stored in the manual feed tray 27 is separated by a BC roller 29 and conveyed to a registration roller 25 by a pre-registration roller 26. Further, a plurality of recording materials P stored in the deck 28 are conveyed to the paper feeding roller 61 by the pickup roller 60, and only one sheet is reliably separated by the paper feeding roller 61 and conveyed to the drawing roller 62. Further, the recording material P is conveyed to the registration roller 25 by the pre-registration roller 26. Thus, the recording material P fed from any of the paper feeding units 22, 27, 28 is conveyed to the registration roller 25.

  As described above, each color toner image formed in each image forming unit S is sequentially transferred to the intermediate transfer belt 30. The image forming units S are arranged along the belt surface of the intermediate transfer belt 30 so that the photosensitive drums 11 are in contact with the belt surface. Next, an intermediate transfer unit having the intermediate transfer belt 30 will be described.

  The intermediate transfer belt 30 is made of a conductive elastic layer containing urethane rubber, silicon rubber, CR (chloroprene) rubber or the like on a base layer made of PI (polyimide), PVdF (polyvinylidene fluoride), or the like. In addition, a surface layer containing a fluororesin or the like is formed on the surface. The intermediate transfer belt 30 includes a driving roller 32 that transmits driving force to the intermediate transfer belt 30, a tension roller 33 that applies appropriate tension to the intermediate transfer belt 30 by urging a spring (not shown), and an intermediate transfer belt 30. It is supported by three driven rollers 34 that form the next transfer region T2, and is stretched between a drive roller 32 (downstream in the belt 30 movement direction) and a tension roller 33 (upstream in the belt 30 movement direction). Four image forming portions S are arranged in parallel on the primary transfer surface T1 which is a flat portion. The drive roller 32 is rotationally driven by a stepping motor (not shown).

  On the back side of the intermediate transfer belt 30 at a position facing each photosensitive drum 11 and the intermediate transfer belt 30 on the primary transfer surface T1, as a transfer unit, a toner image is transferred to the intermediate transfer belt 30. A primary transfer roller 35 (35a, 35b, 35c, 35d) for applying a high voltage, that is, a transfer bias is disposed. A secondary transfer roller 36 is disposed to face the driven roller 34, and a secondary transfer region T <b> 2 is formed by a nip with the intermediate transfer belt 30. The secondary transfer roller 36 is pressed against the intermediate transfer belt 30 with an appropriate pressure.

  An intermediate transfer belt cleaning device (for cleaning the image forming surface of the intermediate transfer belt 30 downstream of the secondary transfer region T2 and upstream of the image forming portion Sa (first image forming portion Sa) in the moving direction of the belt 30. An intermediate transfer body cleaning device) 50 is disposed, and includes a conductive fur brush 51, a bias roller (not shown) for applying a bias to the fur brush 51, and a waste toner box 52 for storing waste toner.

  On the other hand, the recording material P conveyed to the registration roller 25 stops and temporarily stops the rotation of the roller upstream of the registration roller 25 in the conveyance direction, and the registration roller 25 is synchronized with the image formation timing of the image forming unit S. The rotational drive of the upstream roller including is resumed. In this way, the recording material P is sent out to the secondary transfer region T2.

  On the primary transfer surface T1, the color toner images are superimposed and transferred from the image forming portions S to the intermediate transfer belt 30 to be primarily transferred, and a color toner image is formed on the intermediate transfer belt 30. The toner image is conveyed to the secondary transfer region T2. Then, in the secondary transfer region T2, the color toner image is secondarily transferred all at once to the recording material P that has been transported in time.

  The recording material P on which the color toner image is secondarily transferred is conveyed to the fixing unit 40. The fixing unit 40 is discharged from the fixing roller 41a having a heat source such as a halogen heater inside, a pressure roller 41b (which may also be provided with a heat source) pressed against the roller, and the roller pair. And an internal paper discharge roller 44 for conveying the recording material P. The recording material P is conveyed to the nip portion between the fixing roller 41a and the pressure roller 41b, and heat and pressure are applied to the recording material P to fix the toner image.

  After the toner image is transferred in the secondary transfer region T2 and the recording material P fixed in the fixing unit 40 passes through the inner paper discharge roller 44, the conveyance destination is switched by the switching flapper 73. When the switching flapper 73 is on the face-up discharge side, the recording material P is discharged to the face-up discharge tray 76 by the outer discharge roller 45.

  On the other hand, when the switching flapper 73 is on the face-down paper discharge side, the recording material P is conveyed in the direction of the reverse rollers 72 a, 72 b, 72 c and discharged to the face-down paper discharge tray 77.

  A plurality of sensors are arranged in the conveyance path of the recording material P to detect the passage of the recording material P. The paper feeding retry sensor 64, the deck paper feeding sensor 65, the deck pulling sensor 66, and the registration sensor 67 are provided. An internal paper discharge sensor 68, a face-down paper discharge sensor 69, a double-sided pre-registration sensor 70, a double-sided paper re-feed sensor 71, and the like.

  A cassette paper presence / absence sensor 63 that detects the presence / absence of the recording material P is disposed in the cassette 21 that stores the recording material P, and the manual feed tray 27 detects the presence / absence of the recording material P on the manual feed tray 27. A paper presence / absence sensor 74 is disposed, and a deck paper presence / absence sensor 75 for detecting the presence / absence of the recording material P in the deck 28 is disposed on the deck 28.

  Next, explanation will be added in accordance with the operation of the apparatus. As an example, a case where the recording material P is conveyed from the cassette 21 will be described.

  After a predetermined time has elapsed from the start of the job, first, the recording material P is sent out one by one from the cassette 21 by the pickup roller 22. Then, the recording material P is conveyed by the paper feed roller 23 to the registration roller 25 via the drawing roller 24 and the pre-registration roller 26. At that time, the registration roller 25 is stopped, and the leading edge of the paper hits the nip portion.

  Thereafter, the registration roller 25 starts rotating in accordance with the timing at which the image forming unit starts image formation. The rotation timing is set so that the recording material P and the toner image primary-transferred onto the intermediate transfer belt 30 from the image forming unit S exactly coincide with each other in the secondary transfer region T2.

  On the other hand, in the image forming unit S, when an image forming operation start signal is issued, on the photosensitive drum 11a in the first image forming unit Sa arranged on the most upstream side in the movement (rotation) direction of the intermediate transfer belt 30 by the process described above. The toner image formed on the toner image is primarily transferred to the intermediate transfer belt 30 in the primary transfer region by the transfer roller 35a to which a high voltage is applied. The primarily transferred toner image is conveyed to the position of the image forming unit Sb which is the next primary transfer region.

  Here, image formation is delayed by a time during which the toner image is conveyed between the image forming portions S, and the next toner image is transferred with the leading edge of the image aligned on the previous image. Thereafter, the same process is repeated, and eventually the four color toner images are primarily transferred onto the intermediate transfer belt 30.

  Thereafter, when the recording material P enters the secondary transfer region T2 and contacts the intermediate transfer belt 30, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the recording material P. Then, the four color toner images formed on the intermediate transfer belt 30 by the process described above are transferred onto the surface of the recording material P. Thereafter, the recording material P is guided to the fixing roller nip portion 40. The toner image is fixed on the surface of the recording material P by the heat of the roller pair 41a and 41b and the pressure of the nip. Thereafter, the recording material P is discharged to the face-up discharge tray 76 or the face-down tray 77 in accordance with the switching direction of the switching flapper 73, and a recording material P on which the toner image is fixed as an image formed product is obtained.

  The present invention is an image forming apparatus that forms a color image by the intermediate transfer method as described above, and has been made in view of the problems of the prior art, and remains due to an abnormal end of an image forming operation (job) due to a jam or the like. In the case where a large amount of toner on the elastic intermediate transfer belt 30 is cleaned, a cleaning method for completing the cleaning in a short time was examined.

  In this embodiment, in addition to the intermediate transfer belt cleaning device 50, other means are used. Specifically, the toner on the intermediate transfer belt 30 is transferred to the primary transfer roller 35 in the primary transfer portion of each image forming portion S. By applying a transfer bias and a reverse bias (reverse transfer bias) to the photosensitive drum 11, it is returned to the photosensitive drum 11, and this is recovered by the photosensitive drum cleaning device 15. Further, residual toner on the intermediate transfer belt 30 is recovered. This is a study of how to do this.

  Then, each photosensitive drum 11 is collected so that the collection amount is not biased, and the residual due to a reduction in the cleaning performance of the photosensitive drum cleaning device 15 caused by the collection amount being biased to any one of the plurality of photosensitive drums 11. This is to avoid the occurrence of toner slipping and the like, and the resulting image defect.

  That is, in the present invention, (1) in addition to collecting residual toner by the intermediate transfer belt cleaning device, (2) detecting the amount of toner remaining on the intermediate transfer belt at the abnormal end of the job, that is, the image density of the toner image, Depending on the image density of the image remaining on the intermediate transfer belt in the recovery operation, (3) that is, when the amount of toner on the intermediate transfer belt is large, not only the cleaning by the intermediate transfer belt cleaning device but also the photosensitive drum The toner remaining on the intermediate transfer member is reversely transferred to the photosensitive drum and moved. (4) The residual toner return amount to the plurality of photosensitive drums is individually controlled, so that the collection amount is not biased to a specific photosensitive drum. Thus, the residual toner was returned to the photosensitive drum, and (5) was collected by the photosensitive drum cleaning device. When the amount of toner on the surface of the intermediate transfer belt is small, it is collected by an intermediate transfer belt cleaning device.

  Here, in this embodiment, the image density on the surface of the intermediate transfer belt 30 in (2) is always detected in the image forming operation (print job), and when the abnormal end is caused by a jam or the like, the detection result is displayed. Based on this, it is determined whether the toner is removed by the intermediate transfer belt cleaning device 50 or moved to the photosensitive drum 11 as usual. Therefore, a control mechanism for the image forming operation in the present embodiment, which detects the developer amount on the intermediate transfer belt 30, that is, the density of the transferred toner image and the abnormal end of the print job will be described.

  FIG. 3 is a control block diagram of the controller 800 that is a controller unit and controls the image forming operation.

  In the control unit 800, the CPU 801 performs basic control. The CPU 801 is roughly divided into six control mechanisms: a ROM 802, a work RAM 803, a reader control unit 806, a printer control unit 807, an image processing unit 805, and an operation unit 900.

  Regarding data processing relating to image forming conditions, a ROM 802 in which a control program shown in flowcharts of FIGS. 1 and 9 described later is written and a work RAM 803 for performing processing are connected via an address bus and a data bus. .

  In addition, regarding the control of the image forming operation by each image forming unit described above, the reader control unit 806 and the printer control unit 807 input / output for controlling each component of the reader unit 200 and the printer unit 201, respectively. It is connected to an electric circuit including ports and the like.

  The image processing unit 805 also performs various types of image processing on the digital data of the document image converted by the reader control unit 806, and external operation condition settings are made from the operation unit 900.

  That is, the control CPU 801 receives the image processing of the image processing unit 805 according to the contents of the control program stored in the ROM 802 according to the condition selected from the operation unit 900, controls the reader control unit 806 and the printer control unit 807, An image forming operation is executed.

  Here, the image forming operation is started by first setting a condition from the operation unit 900 and transmitting a start signal.

  The operation unit 900 is shown in detail in FIG. The operation unit 900 includes a touch panel display 901 and normally displays selected image forming conditions such as the number of copies, selected paper size, magnification, and copy density, as shown in FIG. 4B. Further, the touch panel display 901 has a function of displaying the state of the image forming apparatus to the user. When printing is possible immediately, as shown in FIG. However, when the apparatus is started up, as shown in FIG.

  An image forming condition, that is, a copy mode is instructed by the keys 902 to 907 provided in the operation unit 900. For example, the copy mode is returned to the standard mode by the reset key 902. The copy operation is started by the start key 903, and the copy operation is interrupted by the stop key 904. Further, the copy mode can be corrected by the clear key 905. The number of copies is set by the ten key 906. The color mode selection key 907 automatically determines whether the original is color or black and white, and outputs an ACS key that outputs in color if it is color and outputs in black and white if it is black and white. There is a Color key for color output and a Black key for monochrome output regardless of the original, and any one of the keys is lit.

  In the image forming operation (print job) by the image forming apparatus, the A4 size recording material P is selected by the paper selection key 910 shown in FIG. When the number of copies is set to 11 and the start key 903 is pressed, the information is transmitted from the operation unit 900 to the CPU 801 by the control mechanism shown in FIG. 3, and information such as the paper size and the number of copies is stored in the RAM 803. The print job is started.

  During a print job, the density of the toner image formed on the intermediate transfer belt 30, that is, the toner image transferred from the photosensitive drum 11 onto the intermediate transfer belt 30 is always detected.

  Incidentally, data of the formed image is written in the RAM 803 of the control unit. For the formed image, a video count value in which the number of image signals is counted in each color toner image is written, and when the print job is abnormally terminated due to a jam or the like, the progress of image formation can be known. It has become. In other words, it is possible to know at which time of the primary transfer process or the secondary transfer process the abnormal termination has occurred during the image formation of the number of sheets. This video count value will be described.

  FIG. 5 is a block diagram showing an internal configuration of the image processing unit 805 in FIG. 3 described above.

  The original image formed on the CCD sensor 217 is converted into an analog electric signal by the CCD sensor 217. The converted image information is input to the analog signal processing unit 300 for sample & hold, dark level correction, and the like, and then the analog / digital conversion (A / D conversion) is performed by the A / D / SH processing unit 301. Further, shading correction is performed on the digitized signal. In the shading correction, correction for variation in each pixel of the CCD sensor 217 and correction for variation in light quantity depending on the position based on the light distribution characteristics of the document illumination lamp are performed.

  Thereafter, RGB line correction is performed in the RGB line correction unit 302. Since the light input to the RGB light receiving portions of the CCD sensor 217 at a certain time is shifted on the document according to the positional relationship of the RGB light receiving portions, the RGB signals are synchronized here.

  Thereafter, input masking processing is performed by the input masking unit 303 to convert luminance data into density data. Since the RGB value as it is output from the CCD sensor 217 is affected by the color filter attached to the CCD sensor 217, the influence is corrected and converted into a pure RGB value.

  Thereafter, the image is scaled at a desired scaling factor in the scaling unit 304, and the scaled image data is sent to the image memory unit 305 and stored therein.

  For the accumulated image, first, image data is sent from the image memory unit 305 to the γ correction unit 306. The γ correction unit 306 corresponds to a desired output density from the original density data based on a look-up table (LUT) in consideration of the printer characteristics in order to output according to the density value set by the operation unit 900. Converted to density data. Next, the density data is sent to the binarization unit 307. The binarization unit 307 converts an 8-bit multilevel signal into a binary signal. For example, a dither method, an error diffusion method, an improved error diffusion, or the like is used as this conversion method. The binarized data is sent to the video count unit 308, and binarized data is counted for each color image.

  FIG. 6 shows details of the video signal count unit 308. In the video signal counting unit 308, each color is counted with the configuration shown in FIG. The image signal 700 for one color sent from the binarization unit 307 counts the image signal for one image in parallel every 8 bits by 29-bit counters 701 to 708, and those results are output by a 32-bit adder 709. By adding, the video count for one image is obtained as 32-bit data.

  That is, the video count value is obtained by counting the number of image signals for one image in the image signal processing read from the reader unit 200 in the image processing unit 805. Also, the binarized data of the density data obtained by the image processing unit 805 is extracted from the video count value, and the image density of the toner image formed on the intermediate transfer belt 30 is obtained.

  Table 1 shows a data structure for detecting the image density on the intermediate transfer belt 30 in the image forming operation (print job) performed in this embodiment. The data shown in Table 1 are all cleared to “0” on the work RAM 803 at the start of the print job, and data is written as the image forming operation proceeds.

  In Table 1, the toner image on the intermediate transfer belt 30 is identified by the image ID. 1-No. 6, the video count values Sa, Sb, Sc, Sd of each color of the toner image formed in each image forming unit S are recorded after the primary transfer of each color. Note that the image ID of the image for which the primary transfer has not been completed is “0”. The image ID is written when the primary transfer of the first image forming unit Sa (here, yellow station) arranged at the most upstream in the moving direction of the intermediate transfer belt 30 is started.

  That is, the video count value Sa in the first image forming unit Sa is the video count value of the yellow image formed on the photosensitive drum 11a and primarily transferred onto the intermediate transfer belt 30, and the primary image of the yellow image with the corresponding ID. Written when transfer is completed. The video count value Sb of the second image forming unit Sb is the video count value of the magenta image formed on the photosensitive drum 11b and primarily transferred onto the intermediate transfer belt 30, and the primary transfer of the magenta image with the corresponding ID is completed. It is written at the time. The video count value Sc of the third image forming unit Sc is a video count value of a cyan image formed on the photosensitive drum 11c and primarily transferred onto the intermediate transfer belt 30, and the primary transfer of the cyan image with the corresponding ID is completed. It is written at the time. The video count value Sd of the fourth image forming unit Sd is the video count value of the black image formed on the photosensitive drum 11d and primarily transferred onto the intermediate transfer belt 30, and the primary transfer of the black image with the corresponding ID is performed. Written when finished.

  The video count value T2 is information indicating whether or not the image on the intermediate transfer belt 30 has been secondarily transferred to the recording material P, and “1” is written when the primary transfer of the yellow image is started. When the next transfer is completed, “0” is written. Further, when the secondary transfer is completed, the video count values Sa to Sd corresponding to the image ID for which the secondary transfer has been completed are cleared to “0”.

  However, when the job is abnormally terminated due to a jam or the like, the images that have not undergone the secondary transfer process of these video count values Sa to Sd are not cleared to “0”.

  Note that the data shown in Table 1 indicates the intermediate transfer when the print job is started and the toner image 3 on the third intermediate transfer belt 30 from the start is secondarily transferred to the recording material P and is abnormally terminated due to a jam. This is data written in the state of FIG.

  In FIG. 7, the image ID No. 1 transported up to the secondary transfer position T2. 3 toner image 3 and the next image ID No. The toner image 4 of 4 is formed by overlapping toner images of four colors of yellow, magenta, cyan, and black. The image ID No. to be formed next to the toner image 4 is displayed. A toner image 5 of 5 is a toner image in the middle of the primary transfer of cyan to a superposition of yellow and magenta toner images. The image ID No. which is the next toner image. A toner image 6 is a toner image in the middle of the primary transfer of yellow.

  In this state, in Table 1, the image ID Nos. 1 of the first and second toner images 1 and 2 that have already been secondarily transferred and moved from the intermediate transfer belt 30 are shown. 1, no. In the video count value data corresponding to 2, “0” is written in the video count values Sa to Sd at the end of the primary transfer of each color, and “0” is written in the video count value T2 at the end of the secondary transfer.

  The image ID No. of the toner image 3 during the secondary transfer process of the third sheet. 3, the values V-Y3, V-M3, V-C3, and V-K3 of the corresponding video count values Sa to Sd are written at the end of each primary transfer, and the video count values In T2, “1” remains written when the primary transfer of the yellow image is started.

  The image ID No. of the toner image 4 that has just finished the fourth primary transfer process. 4, the values V-Y4, V-M4, V-C4, and V-K4 of the corresponding video count values Sa to Sd are written at the end of each primary transfer, and the video count value T2 includes “1” remains written when the primary transfer of the yellow image is started.

  The image ID No. of the toner image 5 during the fifth primary transfer process. The video counts Sa and Sb values V-Y5 and V-M5 corresponding to 5 are written at the end of the primary transfer of yellow and magenta after the primary transfer, and the primary transfer has not been completed yet. “0” is written in the video count values Sc and Sd of cyan and black. As the video count value T2, “1” remains written when the primary transfer of the yellow image is started.

  The image ID No. in the middle of the 6th primary transfer process. As the video count value T2 corresponding to 6, “1” is written when the primary transfer of the yellow image after the primary transfer process is started. With respect to the video count values Sb to Sd of the colors for which the primary transfer process has not been completed, “0” is still written.

  When the print job is completed normally, all the images on the intermediate transfer belt 30 are secondarily transferred to the recording material P and are ended, and the video count values T2 and Sa to Sd are all “0”. On the other hand, if the print job ends abnormally, the image ID No. 3-No. Since the value of the video count value T2 corresponding to 6 is “1”, it can be detected that the job has ended abnormally.

Also, the video count values Sa to Sd of the data allocated on the RAM 803 are accessed, all the values are added, and the amount of toner remaining on the intermediate transfer belt 30, that is, the density value of the toner image. V _itb is required.

In this embodiment, based on the toner image density V _itb remaining on the intermediate transfer belt 30, if the amount is large, a bias (reverse transfer bias) having a polarity opposite to the primary transfer bias is applied to the primary transfer portion. By applying this, cleaning is performed to return the toner on the intermediate transfer belt 30 to each photosensitive drum 11.

That is, _if the value of V _itb is equal to or greater than the predetermined threshold value T, the reverse transfer bias value of each color is determined by accessing the table in Table 2 assigned on the work RAM 803 as the return amount control value.

  In Table 2, the value of the reverse transfer bias corresponding to each image forming unit S is set. The reverse transfer bias is set to increase as the image forming unit S corresponding to the reverse transfer bias becomes farther from the intermediate transfer belt cleaning device 50. As the reverse transfer bias increases, the potential difference between the surfaces of the photosensitive drum 11 and the intermediate transfer belt 30 increases.

  This is because when the same reverse transfer bias is applied to all colors, the photosensitive drum 11a close to the intermediate transfer belt cleaning device 50 is in the uppermost stream in the moving direction of the belt 30, and thus the toner image has not yet been recovered from the belt 30. The amount of residual toner is large, and the amount collected on the photosensitive drum 11a is the largest. By reducing the amount of toner collected on the upstream side, the toner is evenly distributed to the photosensitive drums 11b to 11d on the downstream side.

  In other words, in this embodiment, when the print job is abnormally terminated due to a jam or the like, the density of the toner image remaining on the intermediate transfer belt 30 is detected and collected to each drum 11 so that the toner amount is not biased. Have The toner reversely transferred by each photosensitive drum 11 is collected by the photosensitive drum cleaning device 15 by its rotation. Here, the toner collected from the intermediate transfer belt 30 is a toner mixed with a plurality of colors, but before reaching the roller charger 12 or the developing device 14 that executes the image forming operation according to the rotation of the photosensitive drum 11. Therefore, there is no problem of color mixing.

  The operation of detecting the abnormal end of the print job and removing the toner on the surface of the intermediate transfer belt 30 as described above is performed during the multiple rotations before the image forming process in which the image formation is started again after the abnormal end. Is called.

  The state of the intermediate transfer belt 30 when the operation of returning the toner to the photosensitive drum 11 is performed will be described with reference to FIG. FIG. 8 shows the state of the residual toner image on the surface of the intermediate transfer belt 30 at the start of the previous multi-rotation in the image forming process after the abnormal end. A position X indicates a position on the intermediate transfer belt 30 corresponding to the leading end of the toner image 3.

  When the intermediate transfer belt 30 starts to rotate in the direction of arrow D in the front multi-rotation, first, the fur 51 of the intermediate transfer belt cleaning device 50 is contaminated by a large amount of toner, and the cleaning performance is deteriorated. A bias in the direction opposite to that at the time of recovery is applied.

Then, the surface potential of the photosensitive drum 11 is charged to about 0 V, and the reverse transfer bias set in Table 2 is applied to the primary transfer roller 35 at the timing when the position X reaches the nip portion of the primary transfer roller 35. The intermediate transfer belt 30 is rotated once. At this time, at the nip portion between the intermediate transfer belt 30 and the photosensitive drum 11, the toner on the intermediate transfer belt 30 is returned onto the respective photosensitive drums 11 due to the potential difference between the surface potentials of the intermediate transfer belt 30 and the photosensitive drums 11. The residual toner transferred to is collected by the photosensitive drum cleaning device 15 .

On the other hand, _when the value of V _itb is smaller than the predetermined threshold T, the toner reverse transfer to the photosensitive drum 11 by applying the reverse transfer bias is not performed, and only the intermediate transfer belt cleaning device 50 is used. Clean with.

  Here, the threshold value T is a value that depends on the cleaning capability of the intermediate transfer belt cleaning device 50. In this embodiment, the intermediate transfer belt 30 is cleaned only by the intermediate transfer belt cleaning device 50 by setting the reverse transfer bias value corresponding to each image forming unit S to 0 V with one threshold value T, or as described above. Although it is determined whether the toner is returned from the intermediate transfer belt 30 to each photosensitive drum 11 so that the toner amount is not biased, a plurality of threshold values T may be prepared, and a plurality of reverse transfer bias values corresponding thereto may be prepared. Good.

  Next, a method for cleaning the toner image on the intermediate transfer belt 30 in the recovery operation after the occurrence of the jam, which is performed by the control mechanism, will be described in detail. The recovery operation after the occurrence of the jam is performed according to the flowchart of steps S1 to S8 shown in FIG. 1 registered in the ROM 802 of the control unit 800.

  When the image processing unit 805 detects the abnormal end of the print job, “adjusting” is displayed on the touch panel display 901 of the operation unit 900 as shown in FIG. A user who knows the abnormal end performs maintenance to remove jammed paper from the machine. Then, a start signal is sent again from the operation unit 900, and subsequent image formation is executed.

  Step S1: In step S1, it is monitored whether or not the user has removed the jammed paper from the inside of the machine after closing the jam and closed all the covers (not shown) of the image forming apparatus. If all covers are not closed, recovery will not start.

  Step S2: When all the covers are closed, the front multi-rotation is started in Step S2. In step S2, the screen of the operation unit 900 touch panel display 901 is changed to a standby screen displaying “Adjusting” shown in FIG. 4C, and driving of the intermediate transfer belt 30 and the photosensitive drum 11 is started.

  Step S3: Next, in step S3, it is determined whether or not the previous job ended abnormally. In step S <b> 3, the video count value T <b> 2 of the data in Table 1 allocated on the work RAM 803 is accessed. If there is an image ID in which “1” is written, the previous job is transferred to the intermediate transfer belt 30 with toner. It is determined that the image has ended abnormally while leaving an image, and the process proceeds to step S4.

Step S4: First, the data of the video count values Sa to Sd among the data of Table 1 allocated on the work RAM 803 are accessed, all of the values are added, and the density value of the toner image remaining on the intermediate transfer belt 30 is obtained. _Find V _itb .

Step S5: It is determined whether or not the density value V _itb on the intermediate transfer belt 30 is equal to or greater than a predetermined threshold T. _If the value of V _itb is equal to or greater than the predetermined threshold value T, the process proceeds to step S6. If the value of V _itb is smaller than the predetermined threshold value T, the reverse transfer bias values for all colors are set to 0 V and the _process proceeds to the photosensitive drum 11. In step S9, the intermediate transfer belt cleaning device 50 performs cleaning.

Step S6: When the density value V _itb on the intermediate transfer belt 30 is equal to or greater than a predetermined threshold T, the reverse transfer bias value corresponding to each image forming unit S is accessed in the table of Table 2 assigned on the work RAM 803. To decide.

  Step S7: Using the reverse transfer bias value determined in Step S6, a process for returning the residual toner on the intermediate transfer belt 30 to the photosensitive drum 11 is performed. Here, at the nip portion between the intermediate transfer belt 30 and the photosensitive drum 11, the toner on the surface of the intermediate transfer belt 30 is returned to the surface of the photosensitive drum 11 due to the potential difference between the surface potential of the intermediate transfer belt 30 and the photosensitive drum 11.

  Step S8: The residual toner transferred to the surface of the photosensitive drum 11 is collected by the photosensitive drum cleaning device 15 in each image forming unit S.

Step S9: If Step S8 is completed, or if the previous job has been completed normally in Step S3, or if the toner density value V _itb on the intermediate transfer belt 30 is less than or equal to the threshold T in Step S5, Step S9 The process proceeds to S9. In step S <b> 9, the normal intermediate transfer belt 30 is cleaned by the intermediate transfer belt cleaning device 50. In step S <b> 9, the reverse bias application of the primary transfer roller 35 is stopped and the toner collection bias +700 V is applied to the fur 51 of the intermediate transfer belt cleaning device 50.

  Step S10: Stop the drive of the applied bias and photosensitive drum 11, and intermediate transfer belt 30, and change the touch panel display 901 of the operation unit 900 to a normal screen that displays “Copyable” shown in FIG. 4B. So that the next print job can be started.

  As described above, in the present invention, when cleaning a large amount of toner images on the intermediate transfer belt, in addition to the intermediate transfer belt cleaning device, in addition to the intermediate transfer belt cleaning device, the cleaning can be completed in a short time. Means, specifically, using a cleaning device for each color photosensitive drum, returning the toner on the intermediate transfer belt onto the photosensitive drum, and recovering the toner on the photosensitive drum cleaning device, the residual toner on the intermediate transfer belt Recover. With this method, even when the image forming operation ends abnormally, if the intermediate transfer belt is rotated once, cleaning can be performed and the cleaning time can be shortened.

  Furthermore, if the collection amount is biased to any one of the plurality of photosensitive drums, it affects the cleaning performance of the photosensitive drum cleaning device, causing residual toner to slip through and causing image defects. Collect so that the collection amount is not biased.

  Accordingly, even when a large amount of developer remains on the transfer body, sufficient intermediate transfer body cleaning can be performed in a short time.

  In this embodiment, the toner amount on the intermediate transfer belt and the abnormal end of the print job are detected based on the video count value. However, these may be detected by other methods.

  The configuration and control mechanism of the image forming apparatus may be other than those described in the present embodiment, and the number of image carriers and the type of color are not limited thereto. The present invention is particularly well applied to cleaning of an intermediate transfer member to which a large amount of toner is directly transferred. The present invention can also be applied to an electrostatic recording type.

  In addition, the dimensions, materials, shapes, and relative positions of the components of the image forming apparatus described above are not intended to limit the scope of the present invention to those unless otherwise specified. Absent.

Example 2
In the first embodiment, in the intermediate transfer type image forming apparatus, when a large amount of toner remaining on the surface of the intermediate transfer belt 30 when the print job is abnormally ended is removed and collected to the plurality of photosensitive drums 11, the first embodiment is performed. Then, in order to prevent the amount of toner returned to the plurality of photosensitive drums 11 from being biased, the reverse transfer bias set in Table 2 was applied to the primary transfer portion.

  On the other hand, in the present embodiment, in the image forming apparatus having the same configuration as that of the first embodiment, the surface potential in each photosensitive drum 11 is changed so as not to bias the amount of toner returned to the plurality of photosensitive drums 11. Control.

  In this embodiment, the charging potential of the photosensitive drum 11 is set in the table shown in Table 3 assigned on the work RAM 803 for each image forming unit S, and the charging unit is used for each image forming unit S accordingly. The photosensitive drum 11 is charged by a roller charger 12. Of course, other charging means for charging the photosensitive drum 11 may be provided.

  In Table 3, the charging potential of the photosensitive drum 11 is set to be lower as the position of the image forming unit S is farther from the intermediate transfer belt cleaning device 50. The reverse transfer bias applied to the primary transfer unit at this time is −1100 V in all the image forming units S. The lower the charging potential of the photosensitive drum 11, the larger the potential difference between the surface of the photosensitive drum 11 and the intermediate transfer belt 30.

  That is, in the first embodiment, the reverse transfer bias is changed to adjust the potential difference between the photosensitive drum 11 and the intermediate transfer belt 30 in the primary transfer portion. However, in this embodiment, the photosensitive drum 11 is charged, This was done by changing the surface potential.

  In step S6 of FIG. 1, in the first embodiment, the reverse transfer bias in the primary transfer portion is determined and applied in step S7, whereas in this embodiment, the charging potential of the photosensitive drum 11 is determined according to Table 3. In step S7, the photosensitive drum 11 is charged.

  As a result, the amount of toner to be returned to the photosensitive drum 11 tends to increase. In the first image forming portion Sa, the potential difference between the photosensitive drum 11 and the intermediate transfer belt 30 is widened, so that the intermediate transfer is evenly transferred to the photosensitive drum 11. The toner can be returned from the belt 30.

  Other controls are executed in the same manner as in the first embodiment.

  That is, also in this embodiment, when cleaning a large amount of toner images on the intermediate transfer belt 30, the cleaning device 15 for each color photosensitive drum 11 is used in addition to the intermediate transfer belt cleaning device 50, The toner is returned to the photosensitive drum 11 and is recovered by the photosensitive drum cleaning device 15 so that the recovery amount is not biased by each photosensitive drum 11. As a result, the performance of the photosensitive drum cleaning device 15 is maintained. With this method, even when the image forming operation ends abnormally, the intermediate transfer belt 30 can be cleaned once and the cleaning time can be shortened.

  As a result, even when a large amount of developer remains on the intermediate transfer member, the intermediate transfer member can be sufficiently cleaned in a short time.

Example 3
In the present embodiment, in the image forming apparatus having the entire configuration shown in FIG. 2 similar to that in the first embodiment, a large amount of residual toner on the intermediate transfer belt 30 is collected in consideration of the durability of each photosensitive drum 11. Control was implemented.

  The durability state of the photosensitive drum 11 is defined by the number of image formations, and is determined according to the table shown in Table 4 allocated on the work RAM 803.

  In Table 4, the photosensitive drum 11 is identified for each image forming unit S, and the durability level is determined correspondingly. The endurance level is a value indicating the endurance state of the photosensitive drum 11, that is, how long the photosensitive drum 11 is endured, and is determined by an image formation number integrated value of a value indicating the total number of images formed on the photosensitive drum 11. The The image formation number integrated values NY, NM, NC, and NK in each photosensitive drum 11 are values obtained by sequentially adding the number of image formations from the initial state of the photosensitive drum 11 at the time of installation in terms of A4 paper size. The corresponding video count integrated value is a value indicating the sum of the video counts of the images formed on the photosensitive drum 11, and VY, VM, VC and VK are the video counts at the time of image formation from the initial state of the photosensitive drum at the time of installation. Is a value obtained by sequentially adding.

  Further, the endurance level values EY, EM, EC, and EK are calculated as follows using the image formation number integrated value and the video count integrated value.

Assuming that the video count integrated value is V _sum , the image formation number integrated value is N _sum , the life number of the drum 11 is N _D , and the A4 size solid image video count value is V _A4 , the endurance level value E is expressed by Equation (1). Sought by.

_{E = (N sum / N D} ) × (V sum / V A4) (1)

  The identification value of each image forming unit S is always maintained, and the durability level, the number of image formations, and the video count value are cleared to “0” when the photosensitive drum unit including the photosensitive drum 11 and the photosensitive drum cleaning device 15 is replaced. The value is written for each subsequent image formation.

  The image control unit S according to the present embodiment also has the same configuration as that described with reference to FIGS.

  That is, also in this embodiment, the table in Table 1 is incorporated in the RAM 803, and the abnormal end and the image density of the toner image on the intermediate transfer belt 30 are detected by the video count value for each photosensitive drum 11. Is done.

  During the pre-rotation after the abnormal end, the endurance state of the photosensitive drum 11 is detected.

  First, the endurance level data in Table 4 allocated on the work RAM 803 is accessed, and values “1”, “2”, “3”, “4” corresponding to the color data in order from the largest value. Are stored in another RAM area (not shown). That is, as the durability state, the photosensitive drum 11 of the image forming unit S having the value “1” has the highest durability level among the four photosensitive drums 11 and the photosensitive drum of the image forming unit S having the value “4”. 11 is judged to have the lowest durability level.

Then, as in the first embodiment, reverse transfer is performed so that the toner on the intermediate transfer belt 30 is returned to the photosensitive drum 11 and collected by the photosensitive drum cleaning device 15 with respect to the photosensitive drums 11 for yellow, magenta, cyan, and black. Determine the bias value. That is, first, the data of Sa to Sd of the data in Table 1 allocated on the work RAM 803 are accessed, and all the values are added to obtain the density value V _itb of the toner image remaining on the intermediate transfer belt 30. .

_If the value of V _itb is equal to or greater than a predetermined threshold value T, the reverse transfer bias value of each color is used as the return amount control value on the work RAM 803 based on the durability level of the photosensitive drum 11 shown in Table 4 in this embodiment. The table of Table 5 assigned to is accessed and determined.

  In Table 5, the reverse transfer bias is determined according to the endurance state of the photosensitive drum 11, and a low reverse transfer bias is applied in the endurance state “1” of the photosensitive drum 11 having the highest endurance. Is set so that the reverse transfer bias increases as the durability level decreases.

  This is to reduce the amount of return to the photosensitive drum 11 whose durability is advanced.

  In the operation of returning the toner from the intermediate transfer belt 30 to the photosensitive drum 11, the surface potential of the photosensitive drum 11 is charged to about 0 V, and the timing shown in FIG. 8 reaches the nip portion of the primary transfer roller 35 as shown in Table 5 below. A reverse transfer bias is applied to the primary transfer roller 35 set in step 1 to rotate the intermediate transfer belt 30 once. At this time, at the nip portion between the intermediate transfer belt 30 and the photosensitive drum 11, the toner on the intermediate transfer belt 30 is returned onto each photosensitive drum 11 due to the potential difference between the surface potential of the intermediate transfer belt 30 and the photosensitive drum 11. Residual toner transferred onto the photosensitive drum 11 is collected by the photosensitive drum cleaning device 50.

_When the value of V _itb is smaller than the predetermined threshold value T, the reverse transfer bias value in all the image forming units S is set to 0 V, and the value is not returned to the photosensitive drum 11. Perform cleaning.

  Here, the threshold value T is a value that depends on the cleaning capability of the intermediate transfer belt cleaning device 50. In this embodiment, the reverse transfer bias value in each durability order is set to 0 V with one threshold value T, and the intermediate transfer belt 30 is cleaned only by the intermediate transfer belt cleaning device 50, or the photosensitive drum 11 is in the durable state. Accordingly, the reverse transfer bias in each image forming unit S is determined and whether the toner on the intermediate transfer belt 30 is returned to the photosensitive drum 11 is determined. A plurality of values may be prepared.

  That is, in this embodiment, when the print job is abnormally terminated due to a jam or the like, the density of the toner image remaining on the intermediate transfer belt 30 is detected, and the return amount of the toner amount is not biased to each drum 11. It has a configuration to collect. The toner reversely transferred by each photosensitive drum 11 is collected by the photosensitive drum cleaner 15 by its rotation. Here, toner collected from the intermediate transfer belt 30 is a mixture of a plurality of colors, but before reaching the charging roller 12 or the developing device 14 where the image forming operation is performed according to the rotation of the photosensitive drum 11. Since it is collected, there is no problem of color mixing.

  Next, a method for cleaning the toner image on the intermediate transfer belt 30 in the recovery operation after the occurrence of a jam will be described in detail with reference to FIG.

  Step S1: After the jam stops, it is monitored whether the user has removed the jammed paper from the machine and closed all the covers.

  Step S2: When all the covers are closed, the front multiple rotation is started in Step S2. The operation unit screen is changed to the screen shown in FIG. 4C, and driving of the intermediate transfer belt 30 and the photosensitive drum 11 is started.

  Step S3: It is determined whether or not the previous job ended abnormally. Of the data in Table 1 allocated on the work RAM 803, the video count value T2 is accessed. If there is an image ID in which “1” is written, the previous job left a toner image on the intermediate transfer belt 30. It is determined that the process has ended abnormally, and the process proceeds to step S4.

  Step S4: The durability level data shown in Table 4 allocated on the work RAM 803 is accessed to detect the durability state of the photosensitive drum 11.

Step S5: Access the video count values Sa to Sd of the data in Table 1 allocated on the work RAM 803, add all the values, and the density value V of the toner image remaining on the intermediate transfer belt 30 _Ask for _itb .

Step S6: It is determined whether or not the density value V _itb on the intermediate transfer belt 30 is equal to or greater than a predetermined threshold T. _If the value of V _itb is equal to or greater than the predetermined threshold value T, the process proceeds to step S7. If the value of V _itb is smaller than the predetermined threshold value T, the reverse transfer bias values for all colors are set to 0V and the process proceeds to the photosensitive drum 11. In step S10, the intermediate transfer belt cleaning device 50 performs cleaning.

Step S7: When the density value V _itb on the intermediate transfer belt 30 is equal to or greater than a predetermined threshold T, the reverse transfer bias value corresponding to each image forming unit S is accessed in the table of Table 5 assigned on the work RAM 803. To decide.

  Step S8: Using the reverse transfer bias value determined in Step S7, a process for returning the residual toner on the intermediate transfer belt 30 to the photosensitive drum 11 is performed. Here, at the nip portion between the intermediate transfer belt 30 and the photosensitive drum 11, the toner on the surface of the intermediate transfer belt 30 is returned to the surface of the photosensitive drum 11 due to the potential difference between the surface potential of the intermediate transfer belt 30 and the photosensitive drum 11.

  Step S9: Residual toner transferred to the surface of the photosensitive drum 11 is collected by the photosensitive drum cleaning device 15.

S10: If step S9 is completed, or if the previous job has been completed normally in step S3, or if the toner density V _itb on the intermediate transfer belt 30 is less than or equal to the threshold value T in step S6, the process proceeds to step S10. Transition. In step S <b> 10, the normal intermediate transfer belt 30 is cleaned by the intermediate transfer belt cleaning device 50. In step S <b> 10, the reverse bias application of the primary transfer roller 35 is stopped and the toner collection bias +700 V is applied to the fur 51 of the intermediate transfer belt cleaning device 50.

  S11: The applied bias and the photosensitive drum 11, and the driving of the intermediate transfer belt 30 are stopped, and the touch panel display 901 of the operation unit 900 is changed to a normal screen displaying “copy available” shown in FIG. 4B. So that the next print job can be started.

  As described above, also in this embodiment, when cleaning a large amount of toner images on the intermediate transfer belt, in addition to the intermediate transfer belt cleaning device in order to complete the cleaning in a short time, the intermediate transfer belt cleaning device Other means, specifically, using a cleaning device for each color photosensitive drum, returning the toner on the intermediate transfer belt onto the photosensitive drum, and recovering the toner on the photosensitive drum cleaning device. Collect the residual toner.

  Further, in this embodiment, since it is possible to avoid the possibility that a large amount of toner is returned from the intermediate transfer belt to the durable photosensitive drum among the plurality of photosensitive drums, the residual toner can be obtained even if the cleaning performance of the photosensitive drum cleaning device is low. Image defects such as slipping through can be avoided.

  Similarly, even when the image forming operation ends abnormally and a large amount of developer remains on the transfer body, the intermediate transfer belt can be cleaned once, and the intermediate transfer body can be sufficiently cleaned in a short time. be able to.

Example 4
As in the third embodiment, when it is detected that a large amount of toner remains on the surface of the intermediate transfer belt 30, the return amount from the intermediate transfer belt 30 to the photosensitive drum 11 is determined according to the durability level of the photosensitive drum 11. In this configuration, similarly to the second embodiment, the control can be performed by changing the surface potential of each photosensitive drum 11.

  In this embodiment, the charging potential of the photosensitive drum 11 is set in the table shown in Table 6 allocated on the work RAM 803 for each image forming unit S, and the roller charger is set for each image forming unit S accordingly. 12, the photosensitive drum 11 is charged. Of course, other means for charging the photosensitive drum 11 may be provided.

In Table 6 , the charging potential of the photosensitive drum 11 is determined in accordance with the durability state of the photosensitive drum 11, and the photosensitive drum 11 having the highest durability in the durability state “1” has the highest durability. The charging potential is determined, and the drum 11 is set so that the charging potential becomes lower as the drum 11 is newer and the durability level is lower. The reverse transfer bias applied to the primary transfer unit at this time is −1100 V in all the image forming units S.

  In Table 5, the charging potential of the photosensitive drum 11 is determined according to the durability state of the photosensitive drum 11, and the photosensitive drum 11 having the highest durability in the durability state “1”, that is, the photosensitive drum 11 having the highest durability. The charging potential is determined, and the drum 11 is set to be lower as the drum 11 is newer and the durability level is lower. The reverse transfer bias applied to the primary transfer unit at this time is −1100 V in all the image forming units S.

  This is to reduce the amount of return to the photosensitive drum 11 whose durability is advanced.

  That is, in the third embodiment, the reverse transfer bias is changed to adjust the potential difference between the photosensitive drum 11 and the intermediate transfer belt 30 in the primary transfer portion. However, in this embodiment, the photosensitive drum 11 is charged, This was done by changing the surface potential.

  9, in Example 3, the reverse transfer bias in the primary transfer portion is determined and applied in Step S8 in the third embodiment, whereas in this embodiment, the charging potential of the photosensitive drum 11 is determined according to Table 6. In step S8, the photosensitive drum 11 is charged.

  As a result, a large amount of toner is returned to the photosensitive drum 11 with advanced durability, and the potential difference between the photosensitive drum 11 and the intermediate transfer belt 30 is adjusted, so that the durability of the photosensitive drum 11 can be adjusted. Thus, the toner can be returned from the intermediate transfer belt 30 with an appropriate amount of toner.

  Other controls are executed in the same manner as in the third embodiment.

  That is, also in this embodiment, when cleaning a large amount of toner images on the intermediate transfer belt, a cleaning device for each color photosensitive drum is used in addition to the intermediate transfer belt cleaning device, and the toner on the intermediate transfer belt is transferred to the photosensitive drum. This is returned to the top, and this is recovered by a photosensitive drum cleaning device so that the recovery amount is not biased by each photosensitive drum. This maintains the performance of the photosensitive drum cleaning device.

  Accordingly, even when a large amount of developer remains on the transfer body, sufficient intermediate transfer body cleaning can be performed in a short time.

  As described above, the image forming apparatus of the present invention uses the cleaning device for each color photosensitive drum in addition to the intermediate transfer belt cleaning device, and returns the toner on the intermediate transfer belt onto the photosensitive drum, which is then used as the photosensitive drum. By collecting with the cleaning device, even when a large amount of toner images are cleaned from the intermediate transfer belt when the image forming operation ends abnormally, the intermediate transfer belt can be cleaned once, and the cleaning can be completed in a short time. it can.

  Furthermore, the cleaning performance of the photosensitive drum cleaning device can be maintained by collecting the toner so that a large amount of toner is not returned to the highly durable photosensitive drum.

  Note that the durability of the photosensitive drums of Examples 3 and 4 is determined based on the number of images formed and the number of video counts, but may be determined under other conditions.

4 is a flowchart illustrating an example of an image formation control operation according to the present invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention. 3 is a block diagram illustrating an example of an image forming apparatus control unit according to the present invention. FIG. It is explanatory drawing which shows an example of the image forming apparatus operation part which concerns on this invention. It is a block diagram which shows an example of the image process part which concerns on this invention. It is a block diagram which shows an example of the video count part which concerns on this invention. FIG. 6 is a partial cross-sectional view illustrating a state of a transfer body when an image forming operation ends abnormally. FIG. 6 is a partial cross-sectional view illustrating a state of a transfer body when an image forming operation ends abnormally. 6 is a flowchart illustrating another example of the image formation control operation according to the present invention.

Explanation of symbols

11 Photosensitive drum (image carrier)
12 Roller charger 15 Photosensitive drum cleaning device (image carrier cleaning device)
30 Intermediate transfer belt (transfer body)
35 Primary transfer roller (transfer means)
50 Intermediate transfer belt cleaning device (intermediate transfer member cleaning device)
51 Fur Brush 800 Control Unit 802 ROM
803 RAM
900 Operation unit 901 Touch panel display

Claims (16)

A plurality of image carriers, an electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier based on an image signal based on image information, and developing the electrostatic latent image formed on the image carrier. , a developing unit that a toner image, said moving plurality of image bearing members and opposite to the intermediate transfer member the toner image is transferred from said image bearing member, for removing collected toner of the image bearing member surface Image carrier cleaning device, intermediate transfer member cleaning device for removing and collecting toner on the surface of the intermediate transfer member , means for detecting the density of the toner image transferred to the surface of the intermediate transfer member, and abnormal image forming operation And an image forming apparatus having means for detecting completion
When it is detected that the image forming operation has ended abnormally, the toner remaining on the surface of the intermediate transfer member is removed and collected upon return according to the detected density of the toner image on the surface of the intermediate transfer member. The intermediate transfer member cleaning device is used alone, or the intermediate transfer member cleaning device removes and collects the toner, and at the same time, applies an electric field to all the image carriers to move the toner from the intermediate transfer member to the image carrier. Determining whether to perform the operation of removing and collecting the moved and moved toner by the image carrier cleaning device;
An image forming apparatus, wherein when performing an operation of moving toner from the intermediate transfer member to the image carrier, the amount of toner moved to each of the image carriers is individually controlled. When the toner is moved from the intermediate transfer member to the image carrier, a potential difference is provided between the surface of the intermediate transfer member and the surface of the image carrier, and the potential difference is individually set for each image carrier. The image forming apparatus according to claim 1, wherein the toner amount to be moved to each of the image carriers is individually controlled by controlling to the above. A transfer means for applying a transfer bias for transferring the toner image from the image carrier to an opposing portion of the intermediate transfer member and the image carrier;
When performing an operation of moving toner from the intermediate transfer member to the image carrier, a reverse transfer bias having a polarity opposite to that of the transfer bias is applied to a facing portion between the intermediate transfer member and the image carrier by the transfer unit. Then, the toner is reversely transferred to the image carrier, and the magnitude of the reverse transfer bias is controlled for each of the image carriers, so that the gap between the image carrier and the intermediate transfer member is controlled. 3. The image forming apparatus according to claim 2, wherein the potential difference is individually controlled. The electrostatic latent image forming unit has a charging unit for charging the image carrier to a predetermined surface potential, and the electrostatic latent image forming unit has a charging unit or a charging unit provided elsewhere. When the toner is moved by the means from the intermediate transfer member to the image carrier, the surface potential of each of the image carriers is individually controlled so that the image carrier and the intermediate 3. The image forming apparatus according to claim 2, wherein a potential difference between the transfer member and the transfer member is individually controlled. When performing the operation of moving the toner from the intermediate transfer member to the image carrier, the potential difference between the surface of the intermediate transfer member and the surface of the image carrier is determined by the image carrier at a position far from the intermediate transfer member cleaning device. The image carrier is adjusted such that the potential difference between the surface of the image transfer member and the surface of the intermediate transfer member is larger than the potential difference between the surface of the image carrier at a close position and the surface of the intermediate transfer member. The image forming apparatus according to claim 2, wherein the amount of toner to be moved is individually controlled. When performing the operation of moving the toner from the intermediate transfer body to the image carrier, the image carrier having a means for detecting the durability state of each of the image carriers, and the durability of the image carrier is advanced. The amount of toner moved to each of the image carriers is individually controlled so that the amount of toner moved from the intermediate transfer member is smaller than that of the image carrier that has not advanced. 5. The image forming apparatus according to any one of items 4.   The image forming apparatus according to claim 6, wherein the endurance state of the image carrier is detected based on a total number of images formed on the image carrier. A plurality of image carriers, an electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier based on an image signal based on image information, and developing the electrostatic latent image formed on the image carrier. , a developing unit that a toner image, said moving plurality of image bearing members and opposite to the intermediate transfer member the toner image is transferred from said image bearing member, for removing collected toner of the image bearing member surface Image carrier cleaning device, intermediate transfer member cleaning device for removing and collecting toner on the surface of the intermediate transfer member, video counting means for counting the number of image signals, and means for detecting that the image forming operation has ended abnormally In an image forming apparatus having
The intermediate transfer member upon return according to the number of image signals of the toner image formed on the image carrier counted by the video counting means when it is detected that the image forming operation has ended abnormally The toner remaining on the surface is removed and collected only by the intermediate transfer member cleaning device, or the intermediate transfer member cleaning device removes and collects the toner and moves the toner from the intermediate transfer member to the image carrier. An electric field is formed on all the image carriers , and it is determined whether to move and remove the moved toner by the image carrier cleaning device, and the toner is moved from the intermediate transfer member to the image carrier. When performing an operation, an image forming apparatus characterized by individually controlling the amount of toner to be moved to each of the image carriers. When the toner is moved from the intermediate transfer member to the image carrier, a potential difference is provided between the surface of the intermediate transfer member and the surface of the image carrier, and the potential difference is individually set for each image carrier. 9. The image forming apparatus according to claim 8, wherein the amount of toner to be moved to each of the image carriers is individually controlled by controlling to the above. A transfer means for applying a transfer bias for transferring the toner image from the image carrier to an opposing portion of the intermediate transfer member and the image carrier;
When performing an operation of moving toner from the intermediate transfer member to the image carrier, a reverse transfer bias having a polarity opposite to that of the transfer bias is applied to a facing portion between the intermediate transfer member and the image carrier by the transfer unit. Then, the toner is reversely transferred to the image carrier, and the magnitude of the reverse transfer bias is controlled for each of the image carriers, so that the gap between the image carrier and the intermediate transfer member is controlled. The image forming apparatus according to claim 9, wherein the potential difference is individually controlled. The electrostatic latent image forming unit has a charging unit for charging the image carrier to a predetermined surface potential, and the electrostatic latent image forming unit has a charging unit or a charging unit provided elsewhere. When the toner is moved by the means from the intermediate transfer member to the image carrier, the surface potential of each of the image carriers is individually controlled so that the image carrier and the intermediate The image forming apparatus according to claim 9, wherein the potential difference between the transfer body and the transfer body is individually controlled. When performing the operation of moving the toner from the intermediate transfer member to the image carrier, the potential difference between the surface of the intermediate transfer member and the surface of the image carrier is determined by the image carrier at a position far from the intermediate transfer member cleaning device. The image carrier is adjusted such that the potential difference between the surface of the image transfer member and the surface of the intermediate transfer member is larger than the potential difference between the surface of the image carrier at a close position and the surface of the intermediate transfer member. The image forming apparatus according to claim 9, wherein the amount of toner to be moved is individually controlled. When performing the operation of moving the toner from the intermediate transfer body to the image carrier, the image carrier having a means for detecting the durability state of each of the image carriers, and the durability of the image carrier is advanced. 9. The amount of toner moved to each of the image carriers is individually controlled so that the amount of toner that moves from the intermediate transfer member is smaller than that of the image carrier that has not advanced. 12. The image forming apparatus according to any one of items 11. The endurance state of the image carrier is detected based on an integrated value of the number of the image signals for the toner image formed on the image carrier counted by the video count means. Item 14. The image forming apparatus according to Item 13.   14. The image forming apparatus according to claim 13, wherein the endurance state of the image carrier is detected based on a total number of images formed on the image carrier. 2. The intermediate transfer member according to claim 1, wherein the toner image is primarily transferred from the plurality of image bearing members so as to be primary transferred, and the toner image transferred to the intermediate transfer member is secondarily transferred to a recording material. The image forming apparatus according to any one of 1 to 15.

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