JP2005062637A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device designed for shortening time needed for removal of residual matter remaining on the surface of an image carrier and to provide an image forming apparatus having such a developing device. <P>SOLUTION: The developing device includes: a developing roll which rotates holding, on its surface, two component developer composed of toner and magnetic carrier and conveys the developer to a development area formed between the image carrier and the development roll; and a speed control part which controls the rotating speed of the developing roll. Further, the developing device has a refresh mode in which during a predetermined refresh period when development is not performed, the speed control part performs control such that the developing roll is rotated at a refresh speed higher than a rotating speed used for development, and the surface of the image carrier is cleaned by rubbing the surface of the image carrier with the developer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device for developing an electrostatic latent image formed on an image carrier on which an electrostatic latent image is formed on the surface while moving in a predetermined direction, and image formation provided with such a developing device. Relates to the device.

    Conventionally, some image forming apparatuses such as copying machines and printers adopt an electrophotographic system.

  In this electrophotographic system, for example, an electrostatic latent image created by exposure according to image data is converted into a visible image (toner image) with toner on the surface of a charged photoreceptor roll, and this visible image is finally obtained. In this method, an image is formed by transferring and fixing to a recording sheet.

  By the way, it is known that a discharge product generated by charging adheres to the photoreceptor roll, and a phenomenon called image flow often occurs.

  This is because the electrical discharge product absorbs moisture, so that the electrical resistance of the portion of the photoreceptor roll where the electrical discharge product adheres decreases, and this reduction in electrical resistance adversely affects the formation of a latent image by exposure. Because.

  Therefore, in the conventional image forming apparatus, the cleaning blade is brought into contact with the photoconductor roll to remove discharge products and other residues from the surface of the photoconductor roll.

  Recently, however, there has been a proposal for removing these residues without using the cleaning blade for the purpose of suppressing the wear of the photosensitive roll caused by bringing the cleaning blade into contact with the photosensitive roll. (See Patent Documents 1 and 2.)

  The above proposal develops an electrostatic latent image by rotating a developer composed of toner and a magnetic carrier while holding the developer on the surface, and rubbing the developer against a photoreceptor roll on which the electrostatic latent image is formed. The developing roll is also used for scraping off the residue on the surface of the photoreceptor roll.

However, in the case of the cleaning methods as seen in these Patent Documents 1 and 2, it is expected that it takes time to remove the residue.
JP 2002-174915 A Japanese Patent Laid-Open No. 10-3238

  SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a developing device that has been devised for reducing the time required to remove residues remaining on the surface of an image carrier, and an image forming apparatus including such a developing device. The purpose is to do.

In order to achieve the above object, the developing device of the present invention comprises:
In a developing device for developing an electrostatic latent image formed on an image carrier on which an electrostatic latent image is formed on a surface while moving in a predetermined direction,
A developing roll for carrying a two-component developer comprising a toner and a magnetic carrier on the surface and rotating and transporting the two-component developer to a development area formed between the image carrier,
A speed control unit for controlling the rotation speed of the developing roll, and
During a predetermined refresh period during non-development, the speed controller is slid on the surface of the image carrier by the two-component developer by rotating the developing roll at a predetermined refresh speed higher than the rotation speed during development. Thus, a refresh mode for cleaning the surface of the image carrier is provided.

  In the developing device of the present invention, the developing roll is rotated at a predetermined speed at which image quality is ensured during development, and is rotated at a faster speed than during development in a predetermined refresh period during non-development. Compared with the case where the rotational speed at the time is the same as the rotational speed at the time of development, the surface of the image carrier can be cleaned in a short time.

  Here, it is preferable that the developing roll rotates in a direction that moves in a direction opposite to the moving direction of the image carrier in the developing region.

  This makes it possible to more effectively clean the surface of the image carrier.

In order to achieve the above object, an image forming apparatus of the present invention comprises:
The electrostatic latent image formed on the image carrier moving in a predetermined direction is developed with toner to form a toner image, and the toner image is finally transferred and fixed on the recording medium, thereby fixing on the recording medium. In an image forming apparatus for forming an image composed of a toner image,
A developing device for developing the electrostatic latent image formed on the image carrier,
This developer is
A developing roll for carrying a two-component developer comprising a toner and a magnetic carrier on the surface and rotating and transporting the two-component developer to a development area formed between the image carrier,
A speed control unit for controlling the rotation speed of the developing roll, and
During a predetermined refresh period during non-development, the speed controller is slid on the surface of the image carrier by the two-component developer by rotating the developing roll at a predetermined refresh speed higher than the rotation speed during development. Thus, it has a refresh mode in which the surface of the image carrier is cleaned.

  An image forming apparatus according to the present invention includes a developing device that rotates a developing roll at a predetermined speed at which image quality is ensured during development, and rotates at a faster speed than during development during a predetermined refresh period during non-development. Therefore, the time required to remove the residue remaining on the surface of the image carrier while ensuring the image quality, compared to the case where a developing device that rotates the developing roll at the same speed as that during development is provided even during non-development. Can be shortened.

  Here, the image forming apparatus of the present invention may be provided with a refresh mode inserting means for inserting the refresh mode when not developing after forming a predetermined number of images, or the density of the formed toner image is adjusted. A toner density sensor to be measured and refresh mode insertion means for inserting the refresh mode when not developing based on a density measurement result by the toner density sensor may be provided. Alternatively, an environment sensor that detects the environment and a refresh mode insertion unit that inserts the refresh mode at the time of non-development based on the environment measurement result by the environment detection sensor may be provided.

  In this way, the surface of the image carrier can be effectively cleaned.

  Alternatively, the image forming apparatus of the present invention may include a refresh mode insertion unit that inserts the refresh mode at the time of non-development at a fixed timing in a sequence for operating the image forming apparatus. .

  As described above, the refresh mode may be inserted uniformly instead of inserting the refresh mode as appropriate according to the sensor or the like.

  According to the image forming apparatus of the present invention, the developing roll is rotated at a predetermined speed at which image quality is ensured during development, and is rotated at a faster speed than during development in a predetermined refresh period during non-development. With this development device, the residue remaining on the surface of the image carrier while ensuring image quality, compared to the case where a development device that rotates the development roll at the same speed as during development is provided even during non-development The time required for removal of can be shortened.

  Hereinafter, embodiments of the developing device of the present invention and the image forming apparatus of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of an embodiment of the image forming apparatus of the present invention, including an embodiment of the developing apparatus of the present invention.

  A printer 1 that is an embodiment of the image forming apparatus according to the present invention shown in FIG. 1 includes four image forming units 10Y, 10M, 10C, and 10K. Body rolls 11Y, 11M, 11C, 11K, charging sections 12Y, 12M, 12C, 12K, exposure sections 13Y, 13M, 13C, 13K, developing rolls 14Y, 14M, 14C, 14K, primary transfer rolls 15Y, 15M, 15C, 15K , And control units 16Y, 16M, 16C, and 16K. The printer 1 is capable of full-color printing, and the symbols Y, M, C, and K added to the end of each of the above components are yellow, magenta, cyan, and black images, respectively. It is a component for formation.

  The printer 1 also includes an intermediate transfer belt 30, a density sensor 31, a secondary transfer roll 32, fixing rollers 33 and 34, a tension roller 35, a humidity sensor 36, and a central control unit 37.

  A basic image forming operation in the printer 1 will be described.

  First, toner image formation by the yellow image forming unit 10Y is started, and a predetermined charge is applied to the surface of the photoreceptor roll 11Y rotating in the direction of arrow A by the charging unit 12Y. Next, exposure light corresponding to a yellow image is irradiated on the surface of the photoreceptor roll 11Y by the exposure unit 13Y to form a latent image. The latent image is developed with yellow toner by the developing roll 14Y, and a yellow toner image is formed on the photoreceptor roll 11Y. The toner image is transferred to the intermediate transfer belt 30 by the primary transfer roll 15Y.

  The intermediate transfer belt 30 circulates in the direction of arrow B, and is synchronized with the timing at which the yellow toner image transferred onto the intermediate transfer belt 30 reaches the primary transfer roll 15M of the next color image forming unit 10M. The magenta image forming unit 10M forms a toner image so that the next color magenta toner image reaches the primary transfer roll 15M. The magenta toner image formed in this way is transferred onto the yellow toner image on the intermediate transfer belt 30 by the primary transfer roll 15M.

  Subsequently, toner image formation by the cyan and black image forming units 10C and 10K is performed at the same timing as described above, and sequentially superimposed on the yellow and magenta toner images of the intermediate transfer belt 30 in the primary transfer rolls 15C and 15K. Is transcribed.

  Thus, the multicolor toner image transferred onto the intermediate transfer belt 30 is secondarily transferred onto the paper 100 by the secondary transfer roll 32, and the multicolor toner image is conveyed along with the paper 100 in the direction of arrow C, and the fixing roll 33. , 34 is fixed on the paper 100 to form a color image.

  FIG. 2 is a schematic configuration diagram of an embodiment of the developing device of the present invention provided in the printer.

  2 shows a developing device 140Y in charge of a yellow image in the printer 1 shown in FIG. 1, a photoreceptor roll 11Y, an exposure device 13Y, a control unit 16Y, and a central portion constituting the image forming unit 10Y shown in FIG. A control unit 37 is shown. Since the developing devices for each color of YMCK have the same configuration, the developing device 140Y responsible for the yellow image will be representatively described below.

  A developing device 140Y shown in FIG. 2 includes a developing roll 14Y, a housing 141Y, mixing augers 142Y and 143Y, a developing roll motor 144Y, and a layer thickness regulating member 145Y, in which toner and a magnetic carrier are mixed. FIG. 2 shows a state in which two mixing augers 142Y and 143Y are disposed inside a housing 141Y in which the developer is accommodated with a partition wall 1411Y interposed therebetween. In addition, a state in which the half of the developing roll 14Y is disposed so as to enter the inside of the housing 141Y is also shown.

  The mixing augers 142Y and 143Y have their rotational directions determined so as to convey the developer in opposite directions, and by uniformly mixing the toner and the magnetic carrier, the toner concentration of the developer, that is, the charge amount of the toner Is kept constant.

  As described above, the developing roll 14Y is disposed so that its half body enters the housing, and rotates while carrying the developer in the housing on the surface, so that the developer can be conveyed to the outside of the housing. It has become.

  The layer thickness regulating member 145Y is provided at the end of the housing 141Y so that the tip 1451Y is close to the surface of the developing roll 14Y, and regulates the layer thickness of the developer held on the surface of the developing roll 14Y. .

  In the developing device 140Y, the toner and the magnetic carrier are agitated in the housing, so that a sufficient charge is imparted to the toner by rubbing with the magnetic carrier. Further, a so-called magnetic brush is formed on the surface of the developing roll 14Y in which magnetic carriers are linked in a spike shape, and toner is electrostatically attached to each magnetic carrier.

  Further, in the developing device 140Y, when the developing roll 14Y rotates in the direction of arrow D, the magnetic brush is also transported in the direction of arrow D, and the developing is an area close to the photoreceptor roll 11Y rotating in the arrow A direction. When passing through the region 20Y, the magnetic brush rubs the surface of the photoreceptor roll 11Y. At this time, development is performed by the charged toner adhering to the electrostatic latent image formed on the surface of the photoreceptor roll 11Y by the electric field applied between the photoreceptor roll 11Y and the developing roll 14Y. It is.

  FIG. 2 also shows a motor 144Y that rotates the developing roll 14Y, a motor driver 1441Y that controls the rotational speed of the motor 144Y, a control unit 16Y that is a component of the image forming unit 10Y shown in FIG. A central control unit 37 that controls the entire printer 1 is also shown. The central control unit 37 receives an operation instruction signal, an image signal, and a humidity sensor 36 transmitted from the personal computer or the like to the printer 1. A humidity signal representing humidity, a density signal representing toner density from the density sensor 31 and the like are received, and a refresh operation to be described later is controlled.

  Image information about the yellow image and rotation speed instruction information for designating the rotation speed of the developing roll 14Y are input from the central control unit 37 to the control unit 16Y of the image forming unit 10Y. The rotational speed of the motor 142Y is controlled through the driver 1421Y and the exposure by the exposure unit 13Y is controlled.

  The developing device 140Y includes an initial job processing period after power-on, an initial job processing period after a predetermined number of images are formed, and an initial job after the humidity exceeds a predetermined value. The difference between the toner density calculated from the processing period and the image information that is the basis of the image formation at the time of image formation and the toner density of the image formed based on the image information is detected, and this difference exceeds a predetermined value. A refresh mode is provided to refresh the residue adhering to the surface of the photoreceptor roll 11Y by increasing the rotational speed of the developing roll 14Y higher than the rotational speed at the time of image formation when the image is not formed in the first job processing period after the image processing. ing.

  FIG. 3 is a graph showing changes in the rotation speeds of the photoconductor roll and the development roll in the refresh mode.

  FIG. 3 shows the state of the refresh operation in the first job processing period after the power is turned on. Here, when the image is formed twice, the rotation speed of the developing roll 14Y is set to 160 m / s and the image is formed. However, the rotation speed of the developing roll 14Y is increased to 260 m / s during the refresh period when the image is not formed. Note that the rotation speed of the photoreceptor roll 11Y is kept at 104 m / s throughout the job processing period.

  The state of the refresh operation in the first job processing period after the predetermined number of images are formed and the state of the refresh operation in the first job processing period after the humidity exceeds a predetermined value are also shown in the figure. Since this is the same as 3, the illustration and description are omitted.

  FIG. 4 is also a graph showing changes in the rotation speeds of the photoconductor roll and the developing roll in the refresh mode.

  FIG. 4 shows a difference between the toner density calculated from the image information that is the basis of the image formation at the time of image formation and the toner density of the actual toner image formed based on the image information. The state of the refresh operation in the first job processing period after it has been found that the threshold value has been exceeded is shown. Here, the state in which patch images are formed three times during the refresh operation is also shown. ing.

  In the printer 1, during the job processing period, first, a refresh operation is performed at the same time as the job is started. First, after the first patch image formation and density detection of the patch image are performed, and the refresh operation is performed again. The second patch image formation and the density detection of the patch image are performed, and the density difference from the first patch image is calculated. At that time, if the density difference is larger than a predetermined value, the refresh operation and the density detection of the patch image are further repeated, and when the density difference from the previous patch image becomes a predetermined value or less, After entering the adjustment cycle, normal image formation is performed. In FIG. 4, the density difference between the patch image formed the third time and the patch image formed the second time is determined in advance. It is shown that normal image formation is performed through the subsequent adjustment cycle by being smaller than a certain value.

  As described above, in the printer 1 of the present embodiment, the developing roll 14Y is rotated at a predetermined speed at which image quality is ensured during development, and is faster than during development during a predetermined refresh period during non-development. Is provided on the surface of the image carrier while ensuring image quality, as compared with the case of having a developing device that rotates the developing roll at the same speed as during development, even when non-developing is provided. The time required for removing the remaining residue can be shortened.

  In this embodiment, the refresh mode is the first job processing period after the power is turned on, the first job processing period after the predetermined number of images are formed, and after the humidity exceeds a predetermined value. The difference between the toner concentration calculated from the first job processing period and the image information that is the basis of the image formation at the time of image formation and the toner concentration of the image formed based on the image information is detected. Although described as being provided at the time of image non-formation in the first job processing period after exceeding a predetermined value, the present invention may not be provided with a refresh mode in all these job processing periods.

  In this embodiment, the difference between the toner density calculated from the image information that is the basis of the image formation at the time of image formation and the toner density of the image formed based on the image information is detected, and this difference is a predetermined value. The refresh mode is provided when the image is not formed in the first job processing period after it is determined that the value exceeds the threshold, but the present invention is not limited to this, and a patch in which a reference density value serving as a reference is calculated in advance. The refresh mode is set for the first job processing period after the image is formed and the difference between the actual density value detected by the density sensor shown in FIG. 1 and the reference density value serving as a reference exceeds a predetermined value. It may be what has been done.

  In the present embodiment, the case where the refresh mode is provided when no image is formed in the first job processing period after the power is turned on is described as an example. However, the present invention is not limited to this, and the printer 1 The timing may be fixedly determined in the sequence in which the operation is performed, or the refresh mode is provided when the image is not formed in the first job processing period after the humidity exceeds a predetermined value. However, the present invention is not limited to this, and may be provided based on the result of detecting an environment other than humidity.

1 is a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention, including an embodiment of a developing device of the present invention. 1 is a schematic configuration diagram of an embodiment of a developing device of the present invention provided in a printer. It is a graph showing the change of the rotational speed of the photoreceptor roll and the developing roll in the refresh mode. 6 is a graph showing changes in the rotation speeds of a photoreceptor roll and a developing roll in a refresh mode.

Explanation of symbols

1 Printer 10Y, 10M, 10C, 10K Image forming unit 11Y, 11M, 11C, 11K Photosensitive member roll 12Y, 12M, 12C, 12K Charging unit 13Y, 13M, 13C, 13K Exposure unit 14Y, 14M, 14C, 14K Developing roll 15Y , 15M, 15C, 15K Primary transfer roll 20Y Development area 30 Intermediate transfer belt 31 Density sensor 32 Secondary transfer roll 33, 34 Fixing roller 35 Tension roller 36 Humidity sensor 37 Central control unit 100 Paper 140Y Developing device 141Y Housing 142Y, 143Y Mixing Auger 144Y Motor 1441Y Partition 145Y Layer thickness regulating member 1451Y Tip

Claims (7)

In a developing device for developing an electrostatic latent image formed on an image carrier on which an electrostatic latent image is formed on a surface while moving in a predetermined direction,
A developing roll for carrying a two-component developer composed of a toner and a magnetic carrier on the surface and rotating and transporting the two-component developer to a development area formed between the image carrier,
A speed controller for controlling the rotation speed of the developing roll, and
During a predetermined refresh period during non-development, the surface of the image carrier is rubbed by the two-component developer by causing the speed controller to rotate the developing roll at a predetermined refresh speed higher than the rotation speed during development. And a refresh mode in which the surface of the image carrier is cleaned. 2. The developing device according to claim 1, wherein the developing roll rotates in a direction that moves in a direction opposite to a moving direction of the image carrier in the developing area. The electrostatic latent image formed on the image carrier that moves in a predetermined direction is developed with toner to form a toner image, and the toner image is finally transferred and fixed on the recording medium, thereby fixing on the recording medium. In an image forming apparatus for forming an image composed of a toner image,
A developing device for developing the electrostatic latent image formed on the image carrier;
The developer is
A developing roll for carrying a two-component developer composed of a toner and a magnetic carrier on the surface and rotating and transporting the two-component developer to a development area formed between the image carrier,
A speed controller for controlling the rotation speed of the developing roll, and
During a predetermined refresh period during non-development, the surface of the image carrier is rubbed by the two-component developer by causing the speed controller to rotate the developing roll at a predetermined refresh speed higher than the rotation speed during development. An image forming apparatus having a refresh mode in which the surface of the image carrier is cleaned. 4. The image forming apparatus according to claim 3, further comprising a refresh mode inserting unit that inserts the refresh mode when the predetermined number of images are not formed and is not developed. A toner density sensor for measuring the density of the formed toner image;
4. The image forming apparatus according to claim 3, further comprising: a refresh mode inserting unit that inserts the refresh mode in a non-developing manner based on a density measurement result by the toner density sensor. An environmental sensor to detect the environment;
4. The image forming apparatus according to claim 3, further comprising: a refresh mode insertion unit that inserts the refresh mode during non-development based on an environmental measurement result by the environmental sensor. 4. The image forming apparatus according to claim 3, further comprising refresh mode insertion means for inserting the refresh mode at the time of non-development at a fixed timing on a sequence for operating the image forming apparatus.

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