JP2012185292A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents failure when switching between image modes, even when the image modes are mixedly loaded, and that improves the life duration and productivity of an image forming unit.SOLUTION: An image forming apparatus includes: a color image forming unit 12a-12c having a color toner; a black image forming unit 12e having a black toner; a heterogenous toner image forming unit 12d having a heterogenous toner; a contacting and separating device 60; and controlling means 70. The contacting and separating device 60 carries out a first separating operation for separating the color image forming unit and the heterogenous toner image forming unit from an intermediate transfer belt 7, and a second separating operation for separating the color image forming unit from the intermediate transfer belt. When shifting from a 5 color mode to a black color mode or to a special monochrome mode which uses the black toner and the heterogenous toner, the controlling means 70 controls an operation of the contacting and separating device 60 according to the number of pages to be printed in a post-shifting mode, and if the number of pages to be printed in the post-shifting mode is low, printing is performed in the post-shifting mode without carrying out the first or the second separating operation.

Description

  The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus having a monochrome mode using black toner, a color mode using black toner and color toner, and a mode using another type of toner.

  In image forming apparatuses such as printers and copiers, so-called full-color tandem systems are widely used for the purpose of forming color images at high speed and high image quality.

  In such an image forming apparatus, four image forming units of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in parallel, and these image forming units are sequentially formed. After the toner images of yellow, magenta, cyan, and black are primarily transferred onto the intermediate transfer belt, which is an intermediate transfer member, and superimposed, the secondary transfer is collectively performed on the transfer paper from the intermediate transfer belt. A full-color or monochrome image is formed by fixing the toner image formed on the paper.

  In a full color tandem machine, a full color mode using a plurality of colors and a black and white monochrome mode are often used selectively. Here, for example, when executing the black and white mode, yellow, magenta, and cyan are not used for image formation. However, since the photoconductors of these colors and the intermediate transfer body are in contact with each other, the image forming units of these colors are operated. The life of these image forming units is reduced by operating them.

  Therefore, conventionally, there is an image forming apparatus provided with a separation mechanism that separates an intermediate transfer belt from a photosensitive drum of a color that is not used for image formation when performing image formation of only a specific color such as a monochrome mode (for example, (See Patent Document 1 and Patent Document 2).

  On the other hand, in recent image forming apparatuses, an image that is difficult or impossible to express with only the four colors of yellow, magenta, cyan, and black is added to the fifth color by adding one image forming unit. Techniques for forming toner images are being studied. The toner used for the fifth color toner image is, for example, a special color toner such as red or blue used for a corporate color dedicated to a specific user, a white toner used for a medium that is not white, a foaming toner for Braille, a fluorescent color toner, or a glossy toner. Examples thereof include a transparent toner and a ferromagnetic toner that are improved.

  In addition to the four colors of yellow, magenta, cyan, and black, when performing image formation using the image forming unit for the fifth color, in the case of the tandem method, the fifth image forming unit is used. Therefore, it is necessary to arrange them side by side in a normal four-color image forming unit.

  Here, even in a color image forming apparatus in which the fifth color is added to the usual four colors, like the selection of the full color mode and the black and white mode in the conventional full color machine, the mode is selected by the user.

  When the fifth image forming unit is used, the five color modes including the fifth color (5th color + Y, M, C, K color) and the normal monochrome mode (K color only) are selected. A candidate that selects a special monochrome mode (fifth color + K color) obtained by adding the fifth color to the normal monochrome mode is a candidate.

  At this time, in order to prevent the life of the image forming unit that is not used for image formation from being shortened, the intermediate transfer belt is separated from the photosensitive drum that is not used for image formation as in the above-described normal four-color full-color tandem machine. (For example, refer to Patent Document 3, Patent Document 4, and Patent Document 5).

  However, when a document that requires a five-color mode, a document that requires a special monochrome mode, and a monochrome document are mixed in a print job, it is necessary to switch the contact state between the intermediate transfer belt and the photosensitive drum during the job. As a result, when the image forming operation is started during the switching operation or immediately after the switching operation, defects due to the vibration of the intermediate transfer belt due to the switching operation, for example, image defects such as color misregistration and pitch unevenness may occur. .

  On the other hand, in order to prevent this problem, if the image forming operation is started after the vibration of the intermediate transfer belt is completely settled, the productivity is significantly impaired.

  Therefore, the present invention prevents the trouble at the time of switching the image mode, and can improve the life and productivity of the image forming unit to the maximum even in the case of a print job in which the image mode is mixed as described above. An object is to provide a forming apparatus.

  According to a first aspect of the present invention for solving the above problem, a black image carrier that forms a toner image with black toner, and a color image carrier that forms a colored toner image with colored toner for forming a color image, respectively. The black toner and the color toner are different from each other, that is, the different toner image carrier that forms a toner image with different toner, and the black image carrier, the color image carrier, and the different toner image carrier, respectively. In addition, a toner image formed on the black image carrier, a toner image formed on each of the plurality of color image carriers, and a toner image formed on the different toner image carrier are transferred in an overlapping manner. And a plurality of color image carriers and the different types of toner with respect to the transferred body in an image forming apparatus for forming an image on a recording medium. A separation device configured to perform a first separation operation for relatively separating the carrier and a second separation operation for relatively separating the color image carrier from the transfer target; and a continuous recording medium In this case, the toner image formed on the black image carrier, the toner images formed on the plurality of color image carriers, and the special toner carrier are formed. Switching from a special color image mode in which all the toner images are transferred onto the transfer medium to a monochrome image mode in which only the toner image formed on the black image carrier is transferred to the transfer medium. Or when the recording medium is continuously fed, the toner image formed on the black image carrier and the different toner image carrier are formed from the special color image mode. The toner image When the mode is switched to the special monochrome image mode in which the image is transferred onto the recording medium, the first image is sent to the separation device based on the number of recording media continuously passed in the monochrome image mode or the special monochrome image mode. An image forming apparatus comprising: a control unit that performs one separation operation and the second separation operation.

  Similarly, the invention according to claim 2 is the image forming apparatus according to claim 1, wherein the control unit is configured to perform continuous sheet feeding of a recording medium, and from the special color image mode to the monochrome image mode. Alternatively, when the switching to the special monochrome image mode is performed, the first separation operation is performed after the number of recording media continuously passed in the monochrome image mode or the special monochrome image mode reaches a predetermined threshold value. Alternatively, the second separation operation is controlled.

  Similarly, the invention of claim 3 is the image forming apparatus according to claim 2, wherein the predetermined threshold value is configured to be variably set to zero or an arbitrary natural number.

  Similarly, according to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the control means is a case where a continuous sheet of recording medium is being passed, and the special color A developing unit for developing the latent image formed on the different-type toner image carrier when the image mode is switched to the monochrome image mode and the first separation operation is not performed. And the driving of the developing unit for developing the latent images formed on the plurality of color image carriers are stopped.

  Similarly, according to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the control unit stops driving of the developing unit of the different toner image carrier and the developing units of the plurality of color image carriers. Sometimes, a cleaning blade that contacts the different toner image carrier is separated from the different toner image carrier to clean the untransferred toner on the different toner image carrier, and the plurality of color image carriers In order to clean the untransferred toner, a plurality of cleaning blades respectively contacting the plurality of color image carriers are separated from the plurality of color image carriers.

  Similarly, the invention according to claim 6 is the image forming apparatus according to any one of claims 1 to 3, wherein the control unit is configured to perform continuous sheet passing of the recording medium, and the special unit. Each of the latent images formed on the plurality of color image carriers is developed when the color image mode is switched to the special monochrome image mode and the second separation operation is not performed. Therefore, the driving of the plurality of developing units is stopped.

  Similarly, according to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, when the driving of the plurality of developing units is stopped, the control means is an untransferred toner on the plurality of color image carriers. In order to clean each of the plurality of color image carriers, a plurality of cleaning blades respectively contacting the plurality of color image carriers are separated from the plurality of color image carriers.

  Similarly, according to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the black image carrier is disposed on the most downstream side in the running direction of the transferred body, and the different type is provided. The toner image carrier is disposed second from the downstream in the running direction of the transfer body.

  Similarly, the invention of claim 9 is the image forming apparatus according to claim 8, wherein the control means is a case where a recording medium is continuously fed, and from the special color image mode to the special monochrome image. When the mode is switched, the second separation operation is performed after the toner image of the black toner formed on the black image carrier is transferred to the transfer target.

  Similarly, according to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the separation device contacts and separates the black image carrier relative to the transfer body. A black image carrier contact / separation mechanism; a color image carrier contact / separation mechanism that relatively contacts / separates the plurality of color image carriers with respect to the transfer target; and the dissimilar toner image with respect to the transfer target. A different toner image carrier contact / separation mechanism that relatively contacts and separates the carrier, and the first separation operation includes the color image carrier contact / separation mechanism and the different toner image carrier contact / separation mechanism. The second separation operation is to operate the color image carrier contact / separation mechanism.

  Similarly, the invention according to claim 11 is the image forming apparatus according to any one of claims 1 to 10, wherein the special toner is a transparent toner or a white toner.

  Similarly, according to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, the colored toner for forming the color image is a toner of three colors of yellow, magenta, and cyan. The different toner is a colored toner different from the black toner and the three color toners.

Similarly, according to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the first to twelfth aspects, the transfer object includes the black image carrier, the plurality of color image carriers, and the dissimilar toner image. An intermediate transfer belt arranged in parallel so as to face the carrier, further comprising a secondary transfer member that secondarily transfers the toner image primarily transferred to the intermediate transfer belt to a recording medium. Features.

  According to the present invention, even for a print job in which image modes are mixedly mounted, it is possible to prevent problems at the time of switching image modes and to maximize the life and productivity of the image forming unit.

1 is a schematic configuration diagram illustrating a configuration of an image forming unit in an image forming apparatus according to an embodiment. FIG. 6 is an explanatory view showing a contact / separation state (full contact state) of an intermediate transfer unit of the image forming apparatus. FIG. 7 is an explanatory view showing a state where the transfer unit is in contact with and separated from the image forming apparatus (during a second separation operation). FIG. 6 is an explanatory view showing an intermediate transfer portion contacting / separating state (during a first separating operation) of the image forming apparatus. FIG. 6 is an explanatory view showing an intermediate transfer portion contact / separation state (total separation state) of the image forming apparatus. 6 is a flowchart showing an approach / separation operation at the time of mode switching of the image forming apparatus. 6 is a graph showing an operation time when printing a special monochrome original and a five-color original mixedly of the image forming apparatus. 6 is a graph showing the driving time of the image forming unit per sheet when printing a special monochrome original and a five-color original mixedly printed by the image forming apparatus. 6 is a flowchart showing an approach / separation operation at the time of mode switching of the image forming apparatus.

  An image forming apparatus according to an embodiment includes a black image carrier that forms a toner image using black toner, a color image carrier that forms a colored toner image using colored toner for forming a color image, and the black toner. And a different toner image carrier that forms a toner image of a different type of toner (hereinafter referred to as a different toner) from the colored toner, and the black image carrier, the color image carrier, and the different toner image carrier, respectively. And a toner image formed on the black image carrier, a toner image formed on each of the plurality of color image carriers, and a toner image formed on the dissimilar toner image carrier. An image to be formed on a recording medium.

  In addition, the image forming apparatus includes a first separation operation for relatively separating the plurality of color image carriers and the different type of toner image carrier with respect to the transfer target, and the color image with respect to the transfer target. And a second separating operation for relatively separating the carrier. This separation device is controlled by the control means.

  Further, the control means is a case where the recording medium is continuously fed, and the toner images formed on the black image carrier and the toners formed on the plurality of color image carriers, respectively. From the special color image mode in which the image and the toner image formed on the special toner carrier are all transferred onto the transfer body, only the toner image formed on the black image carrier is transferred to the transfer body. The toner formed on the black image carrier from the special color image mode when switching to the monochrome image mode to be transferred to the recording medium or when the recording medium is continuously fed. When switching to a special monochrome image mode in which an image and a toner image formed on the different kind of toner image carrier are transferred onto the transfer target body, the monochrome image mode or the special mode is switched. The black image mode based on the number of recording media continuously printed to perform the first detachment operation and the second separation operation in the separation device.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention (hereinafter simply referred to as an embodiment) will be described. Several examples are described below, but the present invention is not limited to these examples, and numerous improvements, modifications, variations, substitutions and application examples are possible without departing from the true spirit and scope of the present invention. It will be possible for those skilled in the art to conceive.

  Hereinafter, an image forming apparatus according to an embodiment will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating a configuration of an image forming unit in the image forming apparatus according to the embodiment. In addition to the image writing unit 11 and the image forming unit 13, the image forming apparatus includes a paper feeding unit, a paper discharge unit, and the like (not shown).

  In general, in the tandem color process, four types of colored toners of black, cyan, magenta, and yellow are used. In addition to these, the image forming apparatus 100 according to the embodiment includes special toners other than the four types of toners. A transparent toner is also used.

  As shown in FIG. 1, the image forming apparatus 100 includes image forming units for each color, that is, five image forming units 12a, 12b, 12c, 12d, and 12e arranged in parallel. The image forming units 12a, 12b, 12c, 12d, and 12e are image carriers 1a, 1b, 1c, 1d, and 1e, developing devices 2a, 2b, 2c, 2d, and 2e, cleaning devices 4a, 4b, and photoconductors, respectively. 4c, 4d, 4e, and charging devices 5a, 5b, 5c, 5d, 5e. Reference numerals 6 a, 6 b, 6 c, 6 d, and 6 e indicate writing light from the image writing unit 11. Here, the developing devices 2a, 2b, 2c, and 2d can be stopped regardless of the rotational driving of the image carriers 1a, 1b, 1c, and 1d. The cleaning devices 4a, 4b, 4c, 4d, and 4e are provided with a cleaning blade that contacts the image carrier 1 and removes residual toner from the image carrier 1, and the cleaning blade is used as necessary. The image carrier 1a, 1b, 1c, 1d, 1e can be separated.

  In the example shown in FIG. 1, conventionally known electrophotographic image forming processes of charging, exposure, and development are executed in the respective image forming units 12a, 12b, 12c, 12d, and 12e. The toner image formed on the image carrier 1 is temporarily transferred from the image forming units 12a, 12b, 12c, and 12d to the intermediate transfer belt 7 in order by the primary transfer device 3, and then transferred to the paper P by the secondary transfer device 8. Is done. Further, the paper P is transported to the fixing device 10 by the transport device 9, and the toner image is fixed to the paper P by the fixing device 10.

  In the image forming apparatus 100 according to the embodiment, toner of the fifth color other than yellow, magenta, cyan, and black is used for the image forming unit 12d (hereinafter, the image forming unit 12d is referred to as a different toner image forming unit 12d). As the toner of the fifth color, in addition to the above-described transparent toner, white toner, chromatic color (red, etc.) toner other than YMC can be used.

  The image forming units 12a, 12b, and 12c contain yellow, magenta, and cyan developers in order (hereinafter, the image forming units 12a, 12b, and 12c are referred to as color image forming units 12a, 12b, and 12c). . Further, the image forming unit 12e contains a black developer (hereinafter, the image forming unit 12e is referred to as a black image forming unit 12e). Then, each toner image formed by each image forming unit is transferred onto the intermediate transfer belt 7. Here, the image carrier 1 disposed in the black image forming unit 12e is a black image carrier 1e, and the image carriers 1 disposed in the color image forming units 12a, 12b, and 12c of yellow, magenta, and cyan are respectively color. The image carrier 1a, 1b, 1c, and the image carrier 1 of the different toner image forming unit 12d using the transparent toner become the different toner image carrier 1d.

  Here, in the color image forming apparatus in which the fifth color is added to the usual four colors, as in the selection of the full color mode and the monochrome mode in the conventional full color machine, the user selects the operation mode.

  As the operation mode when the fifth image forming unit is used, a five-color mode (fifth color + Y, M, C, and K colors), which is a special color mode in which different types of toner are added to four-color toner, The monochrome mode (K color only) and the special monochrome mode (fifth color + K color) obtained by adding the fifth color to the normal monochrome mode are assumed.

  In a conventional full-color machine, in the monochrome mode, the color image forming unit and the intermediate transfer member are separated from each other, thereby preventing the life of the color image forming unit from being reduced and the image deterioration. This technique can be applied even when the fifth image forming unit is used. Specifically, it is as follows.

  In the special monochrome mode, since the color image forming units 12a, 12b, and 12c are not used, the intermediate transfer belt 7 and the color image forming units 12a, 12b, and 12c are separated from each other. Further, since the color image forming units 12a, 12b, and 12c and the different toner image forming unit 12d are not used in the monochrome mode, the intermediate transfer belt 7 is separated from the color image forming units 12a, 12b, and 12c and the different toner image forming unit 12d. Let

  FIG. 2 is an explanatory diagram illustrating the contact / separation state (full contact state) of the intermediate transfer unit of the image forming apparatus according to the embodiment. In this example, the intermediate transfer belt 7 is in contact with the image carriers 1a to 1e of all the image forming units 12a, 12b, 12c, 12d, and 12e, and the five-color mode is executed.

  The image forming apparatus 100 includes a contact / separation device 60 for contacting and separating the image carriers 1a to 1e of the image forming units 12a, 12b, 12c, 12d, and 12e and the intermediate transfer belt 7. As shown in FIG. 2, the contact / separation device 60 is a swing arm for simultaneously contacting / separating the intermediate transfer belt 7 with respect to the color image carriers 1a, 1b, 1c of the color image forming units 12a, 12b, 12c. 20, a color image carrier contact / separation mechanism 25 including a contact / separation cam 21, a drive motor 23, and a drive control unit 24, and a swing arm for contacting / separating the intermediate transfer belt 7 to / from the different toner image forming unit 12d. 30, a contact / separation mechanism 35 including a contact / separation cam 31, a drive motor 33, and a drive control unit 34, and a swing arm for making the intermediate transfer belt 7 contact and separate from the black image forming unit 12 e. 40, a contact / separation cam 41, a drive motor 43, and a black toner image carrier contact / separation mechanism 45 including a drive control unit 44.

  The drive control unit 24, the drive control unit 34, and the drive control unit 44 are connected to the control unit 70. The control unit 70 is based on various conditions, and the drive control unit 24, the drive control unit 34, and the drive control unit 44. To control the driving of the color image carrier contact / separation mechanism 25, the different toner image carrier contact / separation mechanism 35, and the black toner image carrier contact / separation mechanism 45. The control unit 70 controls driving and stopping of the operations of the developing devices 2a, 2b, 2c, and 2d of the image forming units 12a, 12b, 12c, and 12d, and contacts and separates the cleaning blades from the image carrier. To control. Here, the control unit 70 can realize its function by an apparatus control unit that performs overall control of the image forming apparatus 100.

  The control means 70 can be configured as a microcomputer including a CPU, RAM, ROM, and the like, and a control function is realized by processing a program stored in the ROM by the CPU. The control unit 70 controls each unit based on an image forming mode and the number of sheets according to an operator's designation from an input unit (not shown) of the image forming apparatus 100.

  The contact / separation cam 21 is rotationally driven by a drive motor 23 that is driven and controlled by a control signal from a drive control unit 24. The contact / separation cam 31 is rotationally driven by a drive motor 33 that is driven and controlled by a control signal from the drive control unit 34. The contact / separation cam 41 is rotationally driven by a drive motor 43 that is driven and controlled by a control signal from the drive control unit 44.

  The swing arm 20 is swingably supported by an intermediate transfer unit frame (not shown) around a swing support point 22 on one end side, and is supported to stretch the intermediate transfer belt 7 on the other end side. A roller 50 is provided.

  One end of the swing arm 30 is supported by a swing support point 32 provided on the swing arm 40 so as to be swingable. Here, since the swing arm 40 swings, the swing fulcrum 32 itself swings. The swing arm 40 is swingably supported by an intermediate transfer unit frame (not shown) around a swing support point 42 on one end side thereof.

  Next, the operation of the image carrier contacting / separating mechanism will be described. FIG. 3 shows a state of the special monochrome mode in which the color image forming units 12a, 12b, and 12c are separated from the intermediate transfer belt 7 among the five image forming units. By rotating the contact / separation cam 21 halfway from the state shown in FIG. 2, the swing arm 20 swings downward in the figure around the swing fulcrum 22, and the intermediate transfer belt 7 moves to the color image forming unit 12a, They are separated from the color image carriers 1a, 1b, 1c in 12b, 12c. At this time, the contact / separation device 60 performs the second separation operation.

  In this special monochrome mode, the operation of the color image forming units 12a, 12b, and 12c of yellow, magenta, and cyan can be stopped to prevent photoconductor wear and extend the life of the image forming unit.

  FIG. 4 shows the state of the black single color mode in which the color image forming units 12 a, 12 b, 12 c and the different toner image forming unit 12 d among the five image forming units are separated from the intermediate transfer belt 7. When the contact / separation cam 31 is rotated halfway from the state shown in FIG. 3, the swing arm 30 swings downward in the figure around the swing support point 32, and the intermediate transfer belt 7 is placed in the different toner image forming unit 12d. Separated from the different type toner image carrier 1d. At this time, the contacting / separating device 60 performs the first separating operation.

  As a result, it is possible to stop the operation of the image forming units other than black in the black monochrome mode, and it is possible to prevent photoconductor wear and extend the life of the image forming unit.

  FIG. 5 shows a state in which all the image forming units 12 a, 12 b, 12 c, 12 d, 12 e are separated from the intermediate transfer belt 7. When the contact / separation cam 41 is rotated halfway from the state shown in FIG. 4, the swing arm 40 swings downward in the figure about the swing fulcrum 42, and the intermediate transfer belt 7 moves to the black image forming unit 12e. Separated from the image carrier 1e.

  This operation is performed at the end of the print job and is performed to separate all the image forming units from the intermediate transfer belt when the machine is stopped.

  Here, when a document that requires the five-color mode, a document that requires the special monochrome mode, and a monochrome document are mixed in the print job, it is necessary to switch the contact state between the intermediate transfer belt and the photosensitive drum during the job. is there. This switching operation takes a certain amount of time, and the productivity is reduced accordingly.

  If an image forming operation is started immediately after the switching operation or immediately after the switching operation, the intermediate transfer belt vibrates due to the switching operation, causing a problem due to an image defect such as color misregistration or pitch unevenness. Arise.

  Further, if the switching operation starts the image forming operation after the vibration of the intermediate transfer belt is completely settled in order to prevent this problem, the productivity is further significantly impaired. Therefore, specific operations for solving these problems will be described below.

  Next, control of the contact / separation device 60 by the control means 70 will be described. First, switching operation from the five-color mode to the special monochrome mode will be described. In this case, the controller 70 controls whether or not the color image forming units 12a, 12b, and 12c are separated from the intermediate transfer belt 7 by operating the contact / separation device 60 according to the number of continuous prints in the special monochrome mode. .

  Hereinafter, a case where the color image forming units 12a, 12b, and 12c are separated from the intermediate transfer belt 7 when the special monochrome mode is the nth continuous sheet will be described. The numerical value of n can be changed, and 0 and a natural number are equivalent. When n = 0, the color image forming units 12a, 12b, 12c and the intermediate transfer belt 7 are not separated. That is, all the image forming units 12a, 12b, 12c, 12d, and 12e are always brought into contact with the intermediate transfer belt 7. On the other hand, when n = 1, a document that forms an image in a special monochrome mode (hereinafter referred to as a special monochrome document) comes after a document that requires a 5-color mode (hereinafter referred to as a 5-color document). The image forming unit 12a and the intermediate transfer belt 7 are separated from each other.

  FIG. 6 is a flowchart showing an operation when switching from a five-color original to a special monochrome original in the same job. In the case of n = 0, the contact / separation operation is not performed and is excluded, and n in the flowchart is a natural number.

In the following, description will be given in order.
Step SA1: For printing a 5-color original, image formation is performed in the state shown in FIG. 2 in which all of the image forming units 12a, 12b, 12c, 12d, and 12e are in contact with the intermediate transfer belt 7.
Step SA2: If the next original is a two-color original, the process proceeds to Step SA3. In the case of a five-color original, step SA1 is continued.
Step SA3: If n = 1, proceed to Step SA4. Otherwise (n ≧ 2), the process proceeds to Step SA6.
Step SA4: The contact / separation cam 21 is actuated from the state shown in FIG. 2 to separate the intermediate transfer belt 7 from the color image forming units 12a, 12b, 12c to the state shown in FIG. 3 (second separation). Operation).
Step SA5: The driving of the color image forming units 12a, 12b, and 12c is stopped, and the special monochrome original is printed by the different toner image forming unit 12d and the black image forming unit 12e.
Step SA6: The special monochrome original is printed in the state shown in FIG. The color image forming units 12a, 12b, and 12c are in a blank image forming state. At this time, the operation of the developing devices of the color image forming units 12a, 12b, and 12c is stopped, and a cleaning blade that removes residual toner from the color image carriers 1a, 1b, and 1c is separated from the color image carriers 1a, 1b, and 1c. Let
Step SA7: If n-1 special monochrome originals have been printed in step SA6, the process proceeds to step SA4 to perform a separation operation. If the number of continuous prints has not yet been reached, the process returns to step SA6, and the special monochrome original printing in the state shown in FIG. 2 is continued.

  FIG. 7 shows images required from the start of printing to the completion of printing 12 sheets when 12 originals mixed with a special monochrome original and a 5-color original are printed according to the flowchart of FIG. 6 while changing the value of n. The operating time of the forming apparatus is shown. Although the time required varies depending on the arrangement of the originals, the average value of the time for all combinations is shown.

Pattern 1 (n = 1): When a special monochrome original comes after a five-color original, a separation operation is always performed.
Pattern 2 (n = 0): No separation operation is performed, and all printing is performed in the state shown in FIG.
Pattern 3 (n = 5): When four special monochrome originals continue, the separation operation is performed on the fifth.
Pattern 4 (n = 3): When two special monochrome originals continue, the separation operation is performed on the third one.

  From FIG. 7, it can be seen that the operation time is considerably longer in the pattern 1 than in the other patterns, and the time required for printing becomes longer when there are many separation operations. In the pattern 2 without the separation operation, the operation time is constant regardless of the original. From the results of patterns 3 and 4, it can be seen that increasing the value of n approaches the operating time of pattern 2. When n = 5, the operation time of pattern 2 is not so different.

  FIG. 8 shows the drive time (total operation time divided by 12) per color image forming unit 12a, 12b, 12c when printing is performed under the same conditions as described above. Similar to the operation time of the image forming apparatus in FIG. 7, the time taken by the arrangement of the originals varies, but shows the average value of the time in all combinations.

  FIG. 8 shows that the driving time is considerably longer in the pattern 2 than in the other patterns. This is because the color image forming unit is driven during two-color printing because no separation operation is performed. On the other hand, since the pattern 1 is always separated at the time of two-color printing and the driving of the color image forming unit is stopped, the driving time per sheet is shortened. In pattern 3 and pattern 4, the driving time is longer than in pattern 1, but when the driving time is extremely long as in pattern 2, the driving time is eliminated. The reason why the driving time may be longer in the pattern 3 and the pattern 4 than in the pattern 2 depending on the combination of the originals is because it takes some time for the separation operation and the driving stop and start of the color image forming unit.

  Here, from FIG. 7 and FIG. 8, when n is a natural number other than 1, the machine operation time is extremely long as in the case of performing the separation operation every time two-color printing after five-color printing (pattern 1). It can be seen that the drive time per image forming unit does not become extremely long as in the case where the separation operation is not performed (Pattern 2). This is because when the color mode is switched from the five-color mode to the special monochrome mode, whether to separate the color image forming unit and the intermediate transfer body can be selected according to the number of continuous prints in the special monochrome mode. It is shown that the life of the color image forming unit can be extended without lowering the productivity.

  Next, switching from the five-color mode to the black single-color mode will be described. The control unit 70 determines whether or not the color image forming units 12a, 12b, 12c and the different toner image forming unit 12d are separated from the intermediate transfer belt 7 when the five-color mode is switched to the black single-color mode. Is controlled according to the number of continuous prints.

  Hereinafter, the control for separating the color image forming units 12a, 12b, and 12c and the different toner image forming unit 12d from the intermediate transfer belt 7 when the black monochrome mode is the nth continuous sheet will be described. As in the embodiment, the numerical value of n can be changed, and 0 and a natural number are applicable. When n = 0, the color image forming units 12a, 12b, and 12c, the different toner image forming unit 12d, and the intermediate transfer belt 7 are not separated. That is, the image forming units 12a, 12b, 12c, 12d, and 12e are always brought into contact with the intermediate transfer belt 7. On the contrary, when n = 1, the color image forming units 12a, 12b, 12c and the different toner image forming unit 12d are always separated from the intermediate transfer belt 7 when a black single-color original comes after a five-color original.

  FIG. 9 is a flowchart showing an operation when switching from a five-color original to a black single-color original in the same job. In the case of n = 0, the contact / separation operation is not performed and is excluded, and n in the flowchart is a natural number.

In the following, description will be given in order.
Step SB1: For printing a five-color original, image formation is performed in the state shown in FIG. 2 in which all the image forming units 12a, 12b, 12c, 12d, and 12e are in contact with the intermediate transfer belt 7.
Step SB2: If the next original is a black monochromatic original, the process proceeds to step SB3. In the case of a five-color original, step SB1 is continued. In the case of a four-color original, the flowchart of FIG.
Step SB3: If n = 1, proceed to Step SB4. Otherwise (n ≧ 2), the process proceeds to step SB6.
Step SB4: The contact / separation cams 21 and 31 are actuated from the state shown in FIG. 2 to separate the intermediate transfer belt 7 from the color image forming units 12a, 12b and 12c and the different toner image forming unit 12d. Only 12e is brought into contact with the intermediate transfer belt 7 (first separation operation).
Step SB5: Driving of the color image forming units 12a, 12b, 12c and the different toner image forming unit 12d is stopped, and the black image forming unit 12e prints a black monochromatic original.
Step SB6: A black monochrome document is printed in the state shown in FIG. The color image forming units 12a, 12b, and 12c and the different toner image forming unit 12d form a blank paper image. At this time, in the different toner image forming unit 12d, the driving of the developing device 2 is stopped, and the cleaning blade for removing the residual toner on the different toner image carrier 1d is separated from the different toner image carrier 1d.
Step SB7: If black monochromatic original printing in step SB6 has continued for n−1 sheets, the process proceeds to step SB4 and a separation operation is performed. If the number of continuous prints has not yet been reached, the process returns to step SB6, and the black monochromatic original printing in the state shown in FIG. 2 is continued.

  Twelve originals mixed with a black single-color original and a five-color original are printed according to the flowchart shown in FIG. 9 while changing the value of n. The results are not shown, but the operation time of the image forming apparatus is the embodiment. 7, and the driving time per sheet of the color image forming units 12 a, 12 b, 12 c and the different toner image forming unit 12 d is almost the same as in FIG. 8.

  This is because when switching from the five-color mode to the black single-color mode, it is possible to select whether to separate the image forming unit other than black and the intermediate transfer body according to the number of continuous prints in the black single-color mode. This shows that the life of image forming units other than black can be extended without lowering the productivity of printed matter.

  As described above, according to the image forming apparatus 100 according to the embodiment, when switching from the five-color mode to the special monochrome mode, whether or not the color image forming unit and the intermediate transfer member are separated from each other is determined according to whether the special monochrome mode is continuous. Since the selection is made according to the number of printed sheets, when the number of printed sheets in the special monochrome mode after switching is small when switching from the five-color mode to the special monochrome mode, the color image forming unit and the intermediate transfer member are not separated. In addition, when the number of printed sheets in the special monochrome mode is large, the life can be improved by separating the color image forming unit and the intermediate transfer member and stopping the color image forming unit.

  For example, when the number of continuous prints in the special monochrome mode is 10 or more, it is possible to switch to the special monochrome mode after the 10th sheet, and not to switch when the number is 9 or less. In this case, since the separation operation is not performed when the number of printed sheets in the special monochrome mode is small (about several sheets), it is possible to prevent a decrease in productivity due to the operation. On the contrary, when the number of prints in the special monochrome mode is large (for example, several hundreds), the color image forming unit can be stopped after that because it is separated at the 10th sheet, and hundreds of blank sheets are created unnecessarily. It is not necessary to operate with an image, and the lifetime can be prevented from decreasing.

  Further, if the separation operation is performed at the time of switching the mode when the number of prints in the special monochrome mode is small, not only the productivity decreases due to the corresponding operation time, but also to some extent to prevent the vibration of the intermediate transfer belt at the separation time. Since it is necessary to operate the image forming unit extra, if the number of printed sheets is small and the separation time is short, the effect of preventing the life reduction is lost. Therefore, when the number of prints in the special monochrome mode is small, it is more advantageous not to perform the separation operation when switching the mode.

  Further, if the number of printed sheets in the special monochrome mode is large and the separation operation is not performed at the time of mode switching, the larger the number of sheets, the more the color image forming unit operates and the life is shortened. This can be solved by performing a separation operation and stopping these units. Further, when the number of printed sheets in the special monochrome mode is large, the ratio of the time for the separation operation to the entire operation time is small, so that the influence of the productivity reduction is small.

  In addition, when switching from the 5 color mode to the black monochrome mode, it is possible to select whether to separate the image forming unit other than black and the intermediate transfer body according to the number of continuous prints in the black monochrome mode. When switching from the 5 color mode to the black single color mode, if the number of black monochrome mode prints after switching is small, the image forming unit other than black and the intermediate transfer member are not separated and the productivity is improved. When the number of printed sheets in the black monochrome mode is large, the service life can be improved by performing separation and stopping the image forming units other than black.

  In addition, since the number of continuously printed sheets to be separated can be arbitrarily set, optimum control can be performed according to the user's request. For example, when considering productivity first, the threshold value may be set to zero or a large value, and the printing operation time may be longer, so if you want to lengthen the unit replacement time (longer life), the threshold value Can be made relatively small.

  In addition, when the color image forming unit and the intermediate transfer unit are not separated when switching from the 5-color mode to the special monochrome mode, the driving of the photosensitive member cannot be stopped, but the driving of the developing unit can be stopped. It is. By stopping, it is possible to prevent deterioration of the components of the developing means and the developer in the color image forming unit.

  Further, when driving of the developing unit is stopped, no toner is input to the cleaning blade, so that the frictional force between the photosensitive member and the cleaning blade is increased, and there is a high possibility that the blade is turned up. Therefore, when driving of the developing unit is stopped, the blade can be prevented from turning over by separating the cleaning blade from the photosensitive member. By combining with stopping the development unit described above, it is possible to prevent deterioration of the component parts of the developing means and the developer while preventing the problem of blade turning.

  In addition, when switching from the five-color mode to the black single-color mode, even if the image forming unit other than black is not separated from the intermediate transfer unit, the driving of the photosensitive member cannot be stopped, but the driving of the developing unit must be stopped. Can do. By stopping, it is possible to prevent deterioration of the components of the developing means other than black and the developer other than black.

  Further, since the image forming apparatus according to the embodiment is provided with five types of image forming units in parallel, the unit that is separated from the intermediate transfer member and the unit that is not separated are arranged in succession so that the image carrier and The number of contact / separation mechanisms with respect to the intermediate transfer member can be minimized. Since the number of contact / separation mechanisms is small, the cost can be saved and the space can be saved, and the control can be simplified to shorten the contact / separation operation time and prevent problems associated with the contact / separation operation.

  Further, since the black image forming unit and the different toner image forming unit are continuously arranged at the end, the number of image carrier contacting / separating mechanisms can be two. Further, by arranging the black unit downstream, the first print speed in the black mode, that is, the time from the start of printing to the completion of the first sheet printing can be made faster than the other apparatus arrangement.

  Further, when switching from the five-color mode to the special monochrome mode, the separation operation between the color image forming unit and the intermediate transfer unit can be performed after the completion of the primary black transfer in the five-color mode, and the intermediate transfer member is Even if it vibrates, image formation on the drum and primary transfer are not hindered, and image defects can be prevented.

  Further, when transparent toner is used for the fifth color, an image that cannot be expressed by the four-color toner can be formed, such as control of image gloss, printing of special patterns such as water marks and background patterns, and an effect of making the image uneven.

  In addition, when white toner is used as the different toner, it is possible to form a white image on a medium that is not white, such as colored paper or a transparent sheet.

  Further, by using a chromatic toner other than YMC as the different type of toner, there is an effect of improving color reproducibility and an effect of suppressing toner consumption. For example, with respect to a color that has a specific color and is particularly concerned about color reproducibility, such as a corporate color, by using a dedicated color toner, it can be brought closer to the original color than when it is reproduced by superimposing YMC. Further, when the toner of a frequently used color (for example, red) is the fifth color, the toner consumption can be reduced as compared with the case of forming with two or three colors, and the cost for the toner can be reduced.

  In combination with the special monochrome mode, two color images can be printed as special monochrome images without operating the three color image forming units of yellow, magenta, and cyan. In this case, since only two image forming units are used, a two-color image can be output at a low cost.

  Since the image forming apparatus includes the intermediate transfer member, the transfer onto the paper is only required to be performed once, so that the paper handling ability and the color matching accuracy can be improved. Further, by using a belt-like member for the intermediate transfer member, the shape of the intermediate transfer unit can be designed relatively freely, and the degree of freedom in the apparatus layout can be improved.

DESCRIPTION OF SYMBOLS 1 Image carrier 1a, 1b, 1c Color image carrier 1d Dissimilar toner image carrier 1e Black image carrier 2 Developing device 3 Primary transfer device 4 Cleaning device 5 Charging device 7 Intermediate transfer belt 8 Secondary transfer device 9 Conveyance device 10 Fixing device 11 Image writing units 12a, 12b, 12c Color image forming unit 12d Different toner image forming unit 12e Black image forming unit 13 Image forming unit 20 Swing arm 21 Contact / separation cam 22 Swing fulcrum 23 Drive motor 24 Drive control unit 25 Color image carrier contact / separation mechanism 30 Oscillating arm 31 Contact / separation cam 32 Oscillation fulcrum 33 Drive motor 34 Drive controller 35 Oscillating arm 41 Contact / separation cam 42 Oscillation fulcrum 43 Drive Motor 44 Drive controller 45 Black toner image carrier contact / separation mechanism 50 Support roller 60 Contact / separation device 70 Control means 100 Image type Apparatus P paper

JP 2006-171233 A JP 2005-099436 A JP 2006-267706 A JP 2004-258512 A JP 2004-219613 A

Claims (13)

A black image carrier that forms a toner image with black toner;
A color image carrier for forming a colored toner image with a colored toner for forming a color image;
A different toner image carrier that forms a toner image of a different type of toner from the black toner and the colored toner;
A toner image formed on the black image carrier and a toner image formed on the plurality of color image carriers, respectively, facing the black image carrier, the color image carrier and the different toner image carrier. An image forming apparatus for forming an image on a recording medium, and a transfer target for transferring the toner image formed on the different type toner image carrier in a superimposed manner,
A first separation operation for relatively separating the plurality of color image carriers and the different type of toner image carrier from the transfer body; and the relative movement of the color image carrier from the transfer body. A second separating operation for separating;
In the case where the recording medium is continuously fed, the toner image formed on the black image carrier, the toner images formed on the plurality of color image carriers, and the special toner carrier From the special color image mode in which all of the toner image formed thereon is transferred onto the transfer body, the monochrome image mode in which only the toner image formed on the black image carrier is transferred to the transfer body. When switching between
Or
A recording medium is continuously fed, and from the special color image mode, a toner image formed on the black image carrier and a toner image formed on the different toner image carrier; Is switched to a special monochrome image mode for transferring the image onto the transfer object,
Control means for causing the separation device to perform the first separation operation and the second separation operation based on the number of recording media continuously passed in the monochrome image mode or the special monochrome image mode;
An image forming apparatus comprising:   The control means is a case where continuous printing of the recording medium is performed, and when the switching from the special color image mode to the monochrome image mode or the special monochrome image mode is performed, the monochrome image mode Alternatively, the first separation operation or the second separation operation is controlled after the number of recording media continuously passed in the special monochrome image mode reaches a predetermined threshold value. Item 2. The image forming apparatus according to Item 1.   The image forming apparatus according to claim 2, wherein the predetermined threshold value is configured to be variably set to zero or an arbitrary natural number.   The control means is a case where the recording medium is continuously fed, the switching from the special color image mode to the monochrome image mode is performed, and the first separation operation is performed. A developing unit for developing a latent image formed on the different toner image carrier, and a developing unit for developing the latent images formed on the plurality of color image carriers, respectively. 4. The image forming apparatus according to claim 1, wherein the driving is stopped. 5.   The control means is for cleaning untransferred toner on the different toner image carrier when driving of the developing portion of the different toner image carrier and the developing portions of the plurality of color image carriers is stopped. A cleaning blade contacting the different toner image carrier is separated from the different toner image carrier, and each of the plurality of color image carriers is cleaned to clean untransferred toner on the plurality of color image carriers. The image forming apparatus according to claim 4, wherein a plurality of the abutting cleaning blades are separated from the plurality of color image carriers.   The control means is a case where continuous feeding of the recording medium is performed, the switching from the special color image mode to the special monochrome image mode is performed, and the second separation operation is performed. 4. The driving of a plurality of developing units for developing the latent images formed on the plurality of color image carriers, respectively, is stopped when it is not broken. The image forming apparatus described in 1.   The control means includes a plurality of abutting contacts with the plurality of color image carriers to clean untransferred toner on the plurality of color image carriers, respectively, when driving of the plurality of developing units is stopped. The image forming apparatus according to claim 6, wherein a cleaning blade is separated from the plurality of color image carriers.   The black image carrier is disposed on the most downstream side in the traveling direction of the transferred body, and the different type toner image carrier is disposed second from the downstream in the traveling direction of the transferred body. The image forming apparatus according to claim 1.   The control means is formed on the black image carrier when continuous printing of the recording medium is performed and when the special color image mode is switched to the special monochrome image mode. The image forming apparatus according to claim 8, wherein the second separation operation is performed after the toner image of the black toner is transferred to the transfer target. The separation device includes a black image carrier contact / separation mechanism that relatively contacts and separates the black image carrier with respect to the transfer body;
A color image carrier contacting / separating mechanism that relatively contacts and separates the plurality of color image carriers with respect to the transfer target;
A different toner image carrier contact / separation mechanism for moving the different toner image carrier relative to and relative to the transfer target;
It is equipped with
In the first separation operation, the color image carrier contacting / separating mechanism and the different toner image carrier contacting / separating mechanism are operated,
The image forming apparatus according to claim 1, wherein the second separation operation is to operate the color image carrier contact / separation mechanism.   The image forming apparatus according to claim 1, wherein the special toner is a transparent toner or a white toner. The colored toner for forming the color image is a toner of three colors, yellow, magenta, and cyan,
11. The image forming apparatus according to claim 1, wherein the different type of toner is a colored toner different from the black toner and the three color toners. The transfer body is an intermediate transfer belt arranged in parallel so that the black image carrier, the plurality of color image carriers, and the different toner image carrier are opposed to each other,
13. The image forming apparatus according to claim 1, further comprising a secondary transfer member that secondarily transfers the toner image primarily transferred to the intermediate transfer belt to a recording medium.