JP2007017587A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate adverse effects by a stuck stripe formed on an intermediate transfer belt, when an image forming apparatus is in a stopped state for a long time. <P>SOLUTION: The image forming apparatus is provided with a mechanism for making an intermediate transfer belt cleaning blade 11 separated from the intermediate transfer belt 70. When power is supplied to the image forming apparatus, or when the image forming apparatus is restored from a sleep mode, in response to a command, photoreceptors 20Y, 20M and 20C are separated from the intermediate transfer belt 70. Then, the intermediate transfer belt 70 is rotated at a speed lower than the speed of the regular rotation of the intermediate transfer belt 70, until a spot on the intermediate transfer belt 70 coming into contact with the intermediate transfer belt cleaning blade 11, in such a state that the intermediate transfer belt 70 stops passes through at least a nip region B between the first photoreceptor 20Y and the intermediate transfer belt 70. The stuck stripe on the intermediate transfer belt 70, wetted by the carrier from the photoreceptor is removed, when passing through the intermediate transfer belt cleaning blade 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that develops an electrostatic latent image formed on a photoreceptor with a developer in which toner is dispersed in a carrier liquid made of silicon oil or mineral oil.

  There is known an image forming apparatus that develops an electrostatic latent image formed on a photosensitive member with a developer in which toner is dispersed in an insulating carrier liquid. In such an image forming apparatus, unlike a dry electrophotographic image forming apparatus, it is a major theme to efficiently remove and collect the carrier on the photoreceptor and the intermediate transfer belt.

  Japanese Patent Laid-Open No. 2002-189354 discloses an endless belt such as an intermediate transfer belt or a transfer conveyance belt when a carrier on the endless belt such as an intermediate transfer belt or a transfer conveyance belt is removed by a cleaning blade. The structure which made it the subject to prevent the slip of this endless belt and the drive roller which drives this endless belt by the wraparound of liquid substances, such as a carrier, to the inner peripheral surface of this is described.

  FIG. 13 shows a schematic configuration diagram of a wet electrophotographic image forming apparatus disclosed in Patent Document 1. In FIG. This image forming apparatus is configured to form a monochromatic image using one developing device as a developing unit. In the case of a color image forming apparatus, as the developing means, for example, four developing devices using toners of black, yellow, magenta, and cyan are used to form an image. The basic principle of image formation is the same as that of the illustrated image forming apparatus.

  In FIG. 13, first, the surface of a photoreceptor 1001 as a latent image carrier is uniformly charged by a charging roller 1002 as a charging unit. The charged area of the photoconductor 1001 is irradiated with image light 1003 of a document image from an exposure device (not shown) to form an electrostatic latent image on the photoconductor 1001. Thereafter, the electrostatic latent image formed on the photosensitive member 1 is developed with toner supplied from the developing unit 4.

  The developing unit 1004 includes a developing belt 1041 stretched in contact with the photoreceptor 1001 by a plurality of driven rollers 1004a, a driving roller 1004b, and a backup roller 1004c, and a surface (outer peripheral surface) of the developing belt 1041. And a toner application device 1042 for applying the liquid developer. The toner application device 1042 has a pumping roller 1004e that pumps up toner T contained in a toner container 1004d, a squeeze roller 1004f that scrapes off excess toner pumped up by the pumping roller 1004e, and pumped up by the pumping roller 1004e. An application roller 4g for applying the toner T to the surface of the developing belt 1041 is formed.

  The toner T applied to the surface of the developing belt 1041 by the coating roller 1004g rotates the developing belt 1041 in the direction of the arrow in FIG. 13, thereby causing a contact portion (developing) between the developing belt 1041 and the photoreceptor 1001. Part) is supplied to the surface of the photoreceptor 1001. As a result, the electrostatic latent image formed on the surface of the photoconductor 1001 is developed with the toner T, and a toner image is formed on the photoconductor 1001. Specifically, a high-viscosity developer (coating method) uniformly applied onto the surface of the photosensitive member 1001 on which the electrostatic latent image has been formed on a developing belt 1041 as a developer carrying member of the developing unit 1004. However, the toner in the developer is transferred to the electrostatic latent image on the photoreceptor 1001 by the force of an electric field and developed. Note that a roller-shaped developer may be used as the developer carrier. Here, the toner T that has not contributed to the development is scraped off and removed from the outer peripheral surface of the developing belt 1041 by the developing cleaning blade 1004h disposed in contact with the outer peripheral surface of the developing belt 1041.

  The toner image thus formed on the photoreceptor 1001 is stretched by a plurality of stretching rollers (a primary transfer roller 1005a, a driving roller 1005b, and an opposing roller 1005c), similarly to the developing belt 1041. In the contact portion (primary transfer portion) between the intermediate transfer belt 51 of the intermediate transfer unit 5 that rotates in the direction of the arrow and the photosensitive member 1, primary transfer is performed on the outer peripheral surface of the intermediate transfer belt 1051. In the case of the color image forming apparatus, toner images of the respective colors are sequentially formed on the photoreceptor 1001, and the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 1051 in the primary transfer unit. Primary transfer. Specifically, the intermediate transfer belt 1051 is brought into contact with the photosensitive member 1001, and a bias having a polarity opposite to the electrical polarity of the toner is applied to the intermediate transfer belt 1051, and the photosensitive formed by the development. The toner image on the body 1001 is primarily transferred onto the intermediate transfer belt 1051. In the case of forming a color image, the primary transfer process is repeated a plurality of times until a desired image is obtained.

  Here, the residual toner remaining on the photoconductor 1001 without being primary transferred onto the intermediate transfer belt 1051 in the primary transfer portion is a photoconductor cleaning disposed in contact with the outer peripheral surface of the photoconductor 1001. The blade 1006 is scraped off and removed from the outer peripheral surface of the developing belt 1041. Further, the charge remaining on the surface of the photoreceptor 1001 is also removed by a quenching lamp 1007 serving as a charge eliminating unit. As a result, the surface of the photoreceptor 1001 prepares for the next image formation.

  Next, the toner image primarily transferred onto the intermediate transfer belt 1051 is secondly transferred as a secondary transfer unit that is detachably disposed on a portion of the intermediate transfer belt 1051 stretched by the facing roller 1005c. At the nip portion (secondary transfer portion) between the next transfer roller 1008 and the intermediate transfer belt 1051, 2 is placed on a transfer material 1009 such as a transfer sheet or an OHP sheet as a recording medium fed from a sheet feeding device (not shown). Next is transferred.

  Here, the residual toner remaining on the intermediate transfer belt 1051 without being primary transferred onto the transfer material 1009 in the secondary transfer portion is prepared for the next primary transfer. The intermediate transfer belt cleaning blade 1010 disposed in contact with the outer peripheral surface is scraped off and removed from the outer peripheral surface of the intermediate transfer belt 1051. Further, the toner adhering to the peripheral surface of the secondary transfer roller 1008 is also removed by the secondary transfer roller cleaning blade 1011. The transfer material 1009 onto which the toner image is secondarily transferred in this manner is subjected to a fixing process of the toner image by a fixing device (not shown) and then discharged outside the apparatus.

FIG. 14 shows the relationship between the intermediate transfer belt 1051 and the intermediate transfer belt cleaning blade 1010 of the image forming apparatus. As shown in FIG. 14, the blade width D of the intermediate transfer belt cleaning blade 1010 is larger than the image area and the maximum transfer material size area of the intermediate transfer belt 1051, and the belt width B of the intermediate transfer belt 1051. Set to be smaller. Thereby, the back circumference of the carrier C to the back surface of the intermediate transfer belt 1051 is not promoted.
JP 2002-189354 A

  As described above, the surface of the intermediate transfer belt 1051 is configured to be cleaned by the intermediate transfer belt cleaning blade 1010 after the secondary transfer of the toner image onto the transfer material 1009 is completed. In the image forming apparatus disclosed in Patent Document 1, the blade width D of the intermediate transfer belt cleaning blade 1010 is larger than the image area of the intermediate transfer belt 1051 and the maximum transfer material size area, and the intermediate transfer belt 1051. Therefore, the carrier carried on the surface of the intermediate transfer belt 1051 and attached to both end portions of the intermediate transfer belt 1051 is the inner peripheral surface of the intermediate transfer belt 1051. Between the roller and the roller peripheral surface of each tension roller and slippage between the driving roller for driving the intermediate transfer belt 1051 and the intermediate transfer belt 1051 is eliminated, so that the driving of the intermediate transfer belt 1051 is performed. Has the effect of stabilizing.

  However, after the surface of the intermediate transfer belt 1051 is cleaned by the intermediate transfer belt cleaning blade 1010, the area between the surface of the intermediate transfer belt 1051 and the intermediate transfer belt cleaning blade 1010 is shown by the hatched portion in FIG. Residual toner and carrier accumulate. If the image forming apparatus is in a stopped state for a long period of time, the residual toner and the carrier that have accumulated will cause a fixed streak L on the intermediate transfer belt 1051. The principle that the fixed streaks L are generated by the residual toner and the carrier liquid is that the residual toner and the carrier liquid are separated over time. That is, as shown by the hatched portion in FIG. 14, what is scraped by the intermediate transfer belt cleaning blade 1010 is initially in a state where the residual toner is almost uniformly dispersed in the carrier, but the fluidity is low. A certain carrier diffuses on the intermediate transfer belt 1051 with the passage of time, whereas the toner does not diffuse, and remains in the same position as a solid and aggregates. The agglomerated toner stuck in a form that serves as a bridge between the intermediate transfer belt 1051 and the intermediate transfer belt cleaning blade 1010 is the fixing line L. If this fixed streak L remains on the surface of the intermediate transfer belt 1051 as it is, it will cause image disturbance such as streak-like lines in the image finally formed on the recording medium. There was a problem. In addition, this fixed streak L causes a large resistance between the intermediate transfer belt cleaning blade 1010 and the surface of the intermediate transfer belt 1051 when the intermediate transfer belt 1051 starts to rotate again. There is a problem that the surface layer portion of the intermediate transfer belt 1051 is destroyed.

  In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that developing means for developing an electrostatic latent image formed on a photoconductor with a developer in which toner is dispersed in a carrier, and development on the photoconductor. Primary transfer means for transferring the transferred image to the intermediate transfer medium, secondary transfer means for transferring the image transferred to the intermediate transfer medium to the recording medium, and heating and pressurizing the image transferred to the recording medium to the recording medium Fixing means for fixing on the intermediate transfer medium and an intermediate transfer medium for removing the carrier and toner remaining on the intermediate transfer medium from the surface of the intermediate transfer medium after the image transferred to the intermediate transfer medium is transferred to the recording medium A first developing means, a second developing means, a third developing means, each having a cleaning means and an intermediate transfer medium driving means for driving the intermediate transfer medium; 4 developing means of 4th developing means Among the four developing units of the first developing unit, the second developing unit, the third developing unit, and the fourth developing unit, three developing units other than the developing unit that handles the black developer are arranged in the middle. An image forming apparatus including a developing unit separating and contacting mechanism that separates and contacts the transfer medium, the intermediate transfer medium cleaning and separating unit temporarily separating the intermediate transfer medium cleaning unit from the intermediate transfer medium, As a drive mode when the intermediate transfer medium driving unit drives the intermediate transfer medium, a first drive mode in which the intermediate transfer medium is rotated at a normal drive speed at the time of image formation, and a lower speed than the first drive mode. And a second drive mode for rotating the intermediate transfer medium for a certain period of time. The intermediate transfer medium drive means is configured such that the developing means separating mechanism separates the three developing means, and the intermediate transfer medium cleaning After separating means is moved away an intermediate transfer medium cleaning means, it is characterized in that the rotating intermediate transfer medium in said second drive mode.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the intermediate transfer medium driving unit performs the driving in the second driving mode when turning on the power or returning from the sleep mode. It is characterized by this.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the intermediate transfer that has been in contact with the intermediate transfer medium cleaning unit while the intermediate transfer medium is stopped. The intermediate transfer medium is rotated in the second drive mode until the portion on the medium passes through the nip region between the developing means handling the black developer and the intermediate transfer medium.

  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 developing means for handling the black developer is the fourth developing means, and the intermediate transfer medium is The portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning unit in a stopped state passes through the nip region between the third developing unit and the intermediate transfer medium, and then is separated from the developing unit. The mechanism is characterized in that three developing means are brought into contact with the intermediate transfer medium.

  According to a fifth aspect of the present invention, there is provided developing means for developing an electrostatic latent image formed on a photoconductor with a developer in which toner is dispersed in a carrier, and an image developed on the photoconductor as an intermediate transfer medium. Primary transfer means for transferring to the recording medium, secondary transfer means for transferring the image transferred to the intermediate transfer medium to the recording medium, and fixing means for fixing the image transferred to the recording medium by heating and pressing. And an intermediate transfer medium cleaning means for removing the carrier and toner remaining on the intermediate transfer medium from the surface of the intermediate transfer medium after the image transferred to the intermediate transfer medium is transferred to the recording medium. An intermediate transfer medium driving unit for driving the transfer medium, and the developing unit handles first and second developing units, a second developing unit, a third developing unit, and a fourth developing unit. Development means, and the first current means Among the four developing means of the first developing means, the second developing means, the third developing means, and the fourth developing means, the three developing means other than the developing means handling the black developer are separated from and brought into contact with the intermediate transfer medium. The intermediate transfer medium is transferred from the state where the intermediate transfer medium is stopped to a state where the intermediate transfer medium is rotated at a normal driving speed when performing image formation. As a driving mode when the medium driving unit is driven, a third driving mode in which the intermediate transfer medium instantaneously reaches the normal driving speed, and the normal driving speed is reached by taking a longer time than the third driving mode. And a fourth drive mode.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, a fifth drive mode in which the intermediate transfer medium is rotated at a normal drive speed at the time of image formation, and the fifth drive mode. A sixth drive mode for rotating the intermediate transfer medium at a lower speed for a certain period of time, and the intermediate transfer medium drive means moves the intermediate transfer medium in the fourth drive mode when the power is turned on or when returning from the sleep mode. The intermediate transfer medium is rotated in the sixth drive mode after being rotated.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the portion on the intermediate transfer medium that is in contact with the intermediate transfer medium cleaning means while the intermediate transfer medium is stopped. Is characterized in that the intermediate transfer medium is rotated in the sixth drive mode until it has passed through the nip region between the developing means handling black developer and the intermediate transfer medium.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the fifth to seventh aspects, the developing means for handling the black developer is the fourth developing means, and the intermediate transfer medium is The portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning unit in a stopped state passes through the nip region between the third developing unit and the intermediate transfer medium, and then is separated from the developing unit. The mechanism is characterized in that three developing means are brought into contact with the intermediate transfer medium.

  The invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 8, wherein the intermediate transfer medium cleaning means is a cleaning blade.

  According to a tenth aspect of the present invention, there is provided developing means for developing an electrostatic latent image formed on a photoconductor with a developer in which toner is dispersed in a carrier, and an image developed on the photoconductor as an intermediate transfer medium. Primary transfer means for transferring to the recording medium, secondary transfer means for transferring the image transferred to the intermediate transfer medium to the recording medium, and fixing means for fixing the image transferred to the recording medium by heating and pressing. And an intermediate transfer medium cleaning means for removing the carrier and toner remaining on the intermediate transfer medium from the surface of the intermediate transfer medium after the image transferred to the intermediate transfer medium is transferred to the recording medium. An intermediate transfer medium driving unit for driving the transfer medium, and the developing unit handles first and second developing units, a second developing unit, a third developing unit, and a fourth developing unit. The first developing means, the first Of the four developing means of the image means, the second developing means, the third developing means, and the fourth developing means, three developing means other than the developing means that handles the black developer are separated from the intermediate transfer medium. In an image forming apparatus having a developing unit separating contact mechanism that is in contact with the intermediate transfer medium, the intermediate transfer medium is driven normally when image formation is performed as a drive mode when the intermediate transfer medium driving unit drives the intermediate transfer medium. A first drive mode for rotating at a speed; and a second drive mode for rotating the intermediate transfer medium for a certain period at a lower speed than the first drive mode.

  According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, the intermediate transfer medium driving unit performs driving in the second driving mode when the power is turned on or when returning from the sleep mode. It is characterized by this.

  The invention according to claim 12 is the image forming apparatus according to claim 10 or 11, wherein the intermediate transfer medium is in contact with the intermediate transfer medium cleaning unit while the intermediate transfer medium is stopped. The intermediate transfer medium is rotated in the second drive mode for a period until the portion on the medium finishes passing through the nip region between the developing means handling black developer and the intermediate transfer medium. is there.

  The invention according to claim 13 is the image forming apparatus according to any one of claims 10 to 12, wherein the developing means for handling the black developer is the fourth developing means, and the intermediate transfer medium is The portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning unit in a stopped state passes through the nip region between the third developing unit and the intermediate transfer medium, and then is separated from the developing unit. The mechanism is characterized in that three developing means are brought into contact with the intermediate transfer medium.

  The invention according to claim 14 is the image forming apparatus according to any one of claims 10 to 13, wherein the intermediate transfer medium cleaning means is a cleaning roller.

  According to the present invention, even if a fixed streak occurs between the intermediate transfer medium and the intermediate transfer medium cleaning unit, the intermediate transfer medium is generated between the intermediate transfer medium cleaning unit due to the fixed streak. Large resistance is not received at the start of rotation of the intermediate transfer medium.

  According to the present invention, the fixed streaks on the intermediate transfer medium are dampened when the carrier is supplied from the photoconductor, and the next time the streaks pass through the intermediate transfer medium cleaning means, the intermediate transfer medium It can be easily removed by cleaning means. For this reason, the image formed on the recording medium is not disturbed by streak-like images.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An outline of a laser beam printer (hereinafter also referred to as a printer) 10 will be described as an example of the image forming apparatus. Needless to say, the image forming apparatus of the present invention is not limited to a laser printer, but can also be applied to a copying machine, a facsimile, or a multifunction machine having a plurality of these functions. FIG. 1 is a diagram illustrating main components constituting the printer 10. In FIG. 1, the vertical direction is indicated by arrows. For example, the developing units 50Y, 50M, 50C, and 50K are arranged at the lower part of the printer 10, and the intermediate transfer belt 70 is arranged at the upper part of the printer 10. Is arranged.

  The developing units 50Y, 50M, and 50C other than the developing unit 50K are configured to move up and down by a mechanism (not shown), and the photosensitive members 20Y, 20M, and 20C are attached to the intermediate transfer belt 70 along with the movement. On the other hand, it can be contacted and separated. The usage of this mechanism will be described later.

  As shown in FIG. 1, the printer 10 according to the present embodiment includes four developing units 15Y, 15M, 15C, and 15K, an intermediate transfer belt 70, a secondary transfer unit 80, and a fixing unit (not shown). The display unit includes a liquid crystal panel that serves as an informing means for the user, and a control unit 100 (FIG. 2) that controls these units and operates as a printer.

  The developing units 15Y, 15M, 15C, and 15K have a function of developing a latent image with a yellow (Y) developer, a magenta (M) developer, a cyan (C) developer, and a black (K) developer, respectively. ing. As the yellow (Y) developer, magenta (M) developer, cyan (C) developer, and black (K) developer, toners of various colors are dispersed in a liquid carrier. Since the developing units 15Y, 15M, 15C, and 15K have the same configuration, the developing unit 15Y will be described below.

  As shown in FIG. 1, the developing unit 15Y includes a charging unit 30Y, an exposure unit 40Y, a developing unit 50Y as an example of a developing device, and a primary transfer unit along the rotation direction of a photoconductor 20Y as an example of an image carrier. 60Y, a charge eliminating unit 73Y, and a photoreceptor cleaning unit 75Y.

  The photoreceptor 20Y has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and is rotatable about a central axis. In the present embodiment, as shown by an arrow in FIG. Rotate clockwise.

  The charging unit 30Y is a device for charging the photoconductor 20Y. From an exposure unit (not shown), a latent image is formed on the charged photoreceptor 20Y by irradiating a laser in the optical path 40Y. The exposure unit includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and the modulated laser is charged based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoreceptor 20Y.

  The developing unit 50Y is a device for developing the latent image formed on the photoreceptor 20Y using a yellow (Y) developer. Details of the developing unit 50Y will be described later.

  The primary transfer unit 60Y is a device for transferring the yellow developer image formed on the photoreceptor 20Y to the intermediate transfer belt 70. When the four color developers are sequentially transferred by the primary transfer units 60Y, 60M, 60C, and 60K, a full color developer image is formed on the intermediate transfer belt 70.

  The intermediate transfer belt 70 is an endless belt stretched around a plurality of support rollers, and is rotationally driven while being in contact with the photoreceptors 20Y, 20M, 20C, and 20K.

  The secondary transfer unit 80 is a device for transferring a single color developer image or a full color developer image formed on the intermediate transfer belt 70 to a medium such as paper, film, or cloth.

  A fixing unit (not shown) is a device for fusing a single color developer image or a full color developer image transferred onto a medium onto a medium such as paper to form a permanent image.

  The neutralization unit 73Y is a device that removes residual charges on the photoreceptor 20Y after the developer image is transferred onto the intermediate transfer belt 70 by the primary transfer unit 60Y.

  The photoconductor cleaning unit 75Y has a rubber photoconductor cleaning blade 76Y that is in contact with the surface of the photoconductor 20Y. After the developer image is transferred onto the intermediate transfer belt 70 by the primary transfer unit 60Y, the photoconductor cleaning unit 75Y performs photosensitivity. This is a device for scraping and removing the developer remaining on the body 20Y by the photoreceptor cleaning blade 76Y.

  As shown in FIG. 2, the control unit 100 includes a main controller 101 and a unit controller 102. An image signal and a control signal are input to the main controller 101, and in response to a command based on the image signal and the control signal. A unit controller 102 controls each of the units and forms an image.

  Next, the operation of the printer 10 configured as described above will be described with reference to other components.

  First, when an image signal and a control signal from a host computer (not shown) are input to the main controller 101 of the printer 10 via the interface (I / F) 112, the unit controller 102 based on a command from the main controller 101. Under the control, the photoconductors 20Y, 20M, 20C, and 20K, the developing rollers (described later) provided in the developing units 50Y, 50M, 50C, and 50K, the intermediate transfer belt 70, and the like rotate. The photoconductors 20Y, 20M, 20C, and 20K are sequentially charged by the charging units 30Y, 30M, 30C, and 30K at the charging positions while rotating.

  The charged regions of the photoconductors 20Y, 20M, 20C, and 20K reach the exposure position as the photoconductors 20Y, 20M, 20C, and 20K rotate, and are exposed to yellow Y and magenta by the exposure units 40Y, 40M, 40C, and 40K. A latent image corresponding to the image information of M, cyan C, and black K is formed in the area.

  The latent images formed on the photoreceptors 20Y, 20M, 20C, and 20K reach the development position as the photoreceptors 20Y, 20M, 20C, and 20K rotate, and are developed by the development units 50Y, 50M, 50C, and 50K. . As a result, developer images are formed on the photoreceptors 20Y, 20M, 20C, and 20K.

  The developer images formed on the photoconductors 20Y, 20M, 20C, and 20K reach the primary transfer position as the photoconductors 20Y, 20M, 20C, and 20K rotate, and are transferred by the primary transfer units 60Y, 60M, 60C, and 60K. Then, the image is transferred to the intermediate transfer belt 70. At this time, a primary transfer voltage having a polarity opposite to the charging polarity of the developer is applied to the primary transfer units 60Y, 60M, 60C, and 60K. As a result, the four color developer images formed on the respective photoconductors 20Y, 20M, 20C, and 20K are transferred to overlap the intermediate transfer belt 70, and a full color developer image is formed on the intermediate transfer belt 70. Is done.

  A roller is provided on the inner periphery of the intermediate transfer belt 70, and the intermediate transfer belt 70 is driven by a driving force such as a motor (not shown) being transmitted through the roller.

  The full color developer image formed on the intermediate transfer belt 70 reaches the secondary transfer position as the intermediate transfer belt 70 rotates, and is transferred to the recording medium by the secondary transfer unit 80. Such a recording medium is conveyed from a paper supply tray (not shown) to the secondary transfer unit 80 via various rollers (the arrows in FIG. 1 indicate the conveyance direction of the medium). Further, when performing the transfer operation, the secondary transfer unit 80 is pressed against the intermediate transfer belt 70 and a secondary transfer voltage is applied.

  After the full-color developer image is transferred to the recording medium by the secondary transfer unit 80, the intermediate transfer belt 70 further rotates counterclockwise, and the liquid carrier and toner remaining on the surface of the intermediate transfer belt 70 are transferred to the intermediate transfer belt 70. It is removed by the belt cleaning blade 11. The intermediate transfer belt cleaning blade 11 is a rubber blade, and urethane rubber having a hardness of JIS-A 70 ° is used. The width of the intermediate transfer belt cleaning blade 11 is 317 mm with respect to the width of 324 mm of the intermediate transfer belt 70, and the intermediate transfer belt cleaning blade 11 is brought into contact with the intermediate transfer belt 70 at a linear pressure of 50 gf / cm. A mechanism for separating the intermediate transfer belt cleaning blade 11 may be provided as necessary.

  The full-color developer image transferred to the recording medium is heated and pressed by the fixing unit and fused to the medium.

  On the other hand, the photoreceptors 20Y, 20M, 20C, and 20K are neutralized by the neutralization units 73Y, 73M, 73C, and 73K after passing the primary transfer position, and are further supported by the photoreceptor cleaning units 75Y, 75M, 75C, and 75K. The developer adhering to the surface is scraped off by the photoconductor cleaning blades 76Y, 76M, 76C, and 76K to prepare for charging to form the next latent image. The developer that has been scraped off is collected in a remaining developer collecting section provided in the photoreceptor cleaning units 75Y, 75M, 75C, and 75K.

  Next, the configuration of the control unit 100 will be described with reference to FIG. The main controller 101 of the control unit 100 is connected to a host computer via an interface 112 and includes an image memory 113 for storing image signals input from the host computer. The unit controller 102 includes units (charging units 30Y, 30M, 30C, and 30K, exposure units 40Y, 40M, 40C, and 40K, developing units 50Y, 50M, 50C, and 50K, primary transfer units 60Y, 60M, and 60C, and the like. 60K, static elimination units 73Y, 73M, 73C, 73K, photoconductor cleaning units 75Y, 75M, 75C, 75K, secondary transfer unit 80, fixing unit, display unit), and signals from sensors included in these , Each unit is controlled based on a signal input from the main controller 101 while detecting the state of each unit.

  Next, a configuration example of the developing unit will be described with reference to FIGS. FIG. 3 is a cross-sectional view showing main components of the developing unit. FIG. 4 is a conceptual perspective view showing the surface of the developer supply roller 550. 5A to 5C are cross-sectional views showing the shapes of grooves provided on the surface of the developer supply roller 550. FIG. 6 is a schematic diagram illustrating the trail regulation of the regulation blade 560. In FIG. 3, the vertical direction is indicated by arrows as in FIG. 1. For example, the developing roller 510 is above the developer pumping roller 540.

  The printer 10 includes, as developing units, a black developing unit 50K containing black (K) developer, a magenta developing unit 50M containing magenta (M) developer, and a cyan developing unit 50C containing cyan (C) developer. , And a yellow developing unit 50Y containing a yellow (Y) developer is provided. Since each developing unit has the same configuration, the yellow developing unit 50Y will be described below.

  The yellow developing unit 50Y includes a developing roller 510 as an example of a developer carrier, a developer container 530, a developer scooping roller 540, a developer supply roller 550 as an example of a developer supply member, and a regulating member. As an example, a regulation blade 560 and a developing roller cleaning unit 570 are provided.

  The developer storage unit 530 stores a developer D for developing the latent image formed on the photoconductor 20Y. The developer D accommodated in the developer accommodating portion 530 has a low concentration (about 1 to 2 wt%) and a low viscosity with Isopar (trademark: exon) as a carrier, which is generally used conventionally. It is not a volatile liquid developer having volatility, but a non-volatile liquid developer D having a high concentration and high viscosity and having non-volatility at room temperature. That is, the liquid developer D according to the present embodiment has a high concentration of toner particles made of resin, pigment, and the like having an average particle diameter of about 0.1 to 5 μm in a non-volatile and insulating carrier liquid such as silicone oil ( Developer D having a high viscosity (about 100 to 10,000 mPa · s) dispersed in about 5 to 40 wt%.

  The developer pump-up roller 540 pumps up the developer D stored in the developer storage unit 530 and conveys it to the developer supply roller 550. The lower part of the developer pumping roller 540 is immersed in the developer D accommodated in the developer accommodating portion 530, and is separated from the developer supply roller 550 with a width of about 1 mm.

  Further, the developer scooping roller 540 can rotate around its central axis, and the central axis is below the rotational central axis of the developer supply roller 550. Further, the developer scooping roller 540 rotates in the same direction (clockwise in FIG. 3) as the rotation direction of the developer supply roller 550 (clockwise in FIG. 3). The developer pump-up roller 540 has a function of pumping up the developer D stored in the developer storage section 530 and transporting it to the developer supply roller 550, and developing the developer D in an appropriate state. It also has a function of stirring the agent D.

  The developer supply roller 550 supplies the developer D conveyed from the developer container 530 by the developer pumping roller 540 to the developing roller 510. This developer supply roller is formed by uniformly and spirally forming a groove 550a as an example of a recess as shown in FIG. 4 on the surface of a metallic roller such as iron, and having a diameter of about 25 mm. The developer supply roller 550 in the present embodiment includes a groove 550a having a trapezoidal cross section as shown in FIG. 5A as the groove, for example, a groove having an inverted triangular cross section as shown in FIG. 5B. Or a groove having a semicircular cross section as shown in FIG. 5C. As shown in FIG. 5A, the groove dimensions of the developer supply roller 550 in the present embodiment are a groove pitch of about 170 μm, a peak width of about 45 μm, a valley width of about 30 μm, and a groove depth of about 50 μm.

  Further, the developer supply roller 550 has a surface pressed against an elastic layer described later of the development roller 510 in order to appropriately transfer the developer D on the developer supply roller 550 to the development roller 510. ing. Further, the developer supply roller 550 can rotate around its central axis, and the central axis is below the rotation central axis of the developing roller 510. Further, the developer supply roller 550 rotates in a direction (clockwise in FIG. 3) opposite to the rotation direction of the developing roller 510 (counterclockwise in FIG. 3).

  The regulation blade 560 contacts the surface of the developer supply roller 550 and regulates the amount of the developer D on the developer supply roller. That is, the regulation blade 560 plays a role of scraping off the excess developer on the developer supply roller 550 and measuring the developer D on the developer supply roller 550 supplied to the development roller 510. The restriction blade 560 is made of urethane rubber as an elastic body, and is supported by a restriction blade support member 562 made of metal such as iron. The rubber hardness of the regulation blade 560 is about 62 degrees according to JIS-A, and the hardness (about 62 degrees) of the contact portion of the regulation blade 560 with the surface of the developer supply roller 550 is about the developing roller described later. This is lower than the hardness (about 85 degrees) of the pressure contact portion of the elastic body layer 510 to the surface of the developer supply roller 550.

  Further, the edge 560a of the regulating blade 560 is in contact with the surface of the developer supply roller 550, and so-called edge regulation is performed. Further, as shown in FIG. 6, the regulating blade 560 is disposed so that the tip thereof faces the downstream side in the rotation direction of the developer supply roller 550, and performs so-called trail regulation. As shown in FIG. 6, the trail angle is about 10 degrees.

  The developing roller 510 carries the developer D and conveys it to the developing position facing the photoconductor 20Y in order to develop the latent image carried on the photoconductor 20Y with the developer D. The developing roller 510 is provided with an elastic layer as an example of an elastic portion having conductivity on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 510 is in pressure contact with the developer supply roller 550 and the photoreceptor 20Y in a state where the surface layer is a pressure contact portion and is elastically deformed.

  Further, the developing roller 510 can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 20Y. Further, the developing roller 510 rotates in a direction (counterclockwise in FIG. 3) opposite to the rotation direction of the photoreceptor 20Y (clockwise in FIG. 3). When developing the latent image formed on the photoconductor 20Y, an electric field is formed between the developing roller 510 and the photoconductor 20Y.

  The developing roller cleaning unit 570 has a rubber developing roller cleaning blade 571 in contact with the surface of the developing roller 510, and the developer D remaining on the developing roller 510 after development is performed at the developing position. Is scraped off by the developing roller cleaning blade 571 and removed.

  In the yellow developing unit 50Y configured as described above, the developer scooping roller 540 rotates around its central axis, thereby scooping up the developer D accommodated in the developer accommodating portion 530 and developing developer supply roller 550. Transport to.

  The developer D conveyed to the developer supply roller 550 reaches the contact position of the regulating blade 560 by the rotation of the developer supply roller 550. Then, when passing through the contact position, the excess amount of the developer D is scraped off by the regulating blade 560, and the amount of the developer D supplied to the developing roller 510 is measured. That is, since the developer supply roller 550 is provided with the groove 550a as described above, the regulating blade 560 that contacts the developer supply roller 550 causes the developer D on the developer supply roller 550 to enter the groove 550a. The retained developer D is left and scraped off. Further, since the dimension of the groove 550a is determined so that the developer amount of the developer D supplied to the developing roller 510 is an appropriate amount, the regulating blade 560 causes the developer D on the developer supply roller 550 to be removed. When scraped off, the developer D measured to an appropriate amount by the groove 550a remains in the groove 550a.

  The developer D held in the groove 550 a of the developer supply roller 550 reaches a pressure contact position with the development roller 510 by further rotation of the developer supply roller 550. The developer D that has reached the pressure contact position is transferred from the developer supply roller 550 to the development roller 510 due to the pressure generated by the pressure contact between the developer supply roller 550 and the development roller 510, and is transferred onto the development roller 510. A thin film of developer D is formed.

  The developer D thin film formed on the developing roller 510 in this manner reaches the developing position (that is, the pressure contact position with the photoconductor 20Y) facing the photoconductor 20Y by the rotation of the developing roller 510, and the development The latent image formed on the photoconductor 20Y is subjected to development at a position under an electric field of a predetermined magnitude. The developer D on the developing roller 510 that has passed the developing position reaches the contact position of the developing roller cleaning blade 571 as the developing roller 510 further rotates. When passing through the contact position, the developer D attached to the surface of the developing roller 510 is scraped off by the developing roller cleaning blade 571, and the developer D thus scraped off is removed from the developing roller cleaning unit. It is collected in a residual developer collecting unit provided in 570.

  Next, a power supply system of such an image forming apparatus will be described. Such an image forming apparatus is provided with three power sources: a 5V power source that supplies power to a control system component such as a CPU, a 24V power source that supplies power to a drive system component such as a motor, and a 100V power source that supplies power to a fixing heater. . When the main switch is turned on, each of the power supplies is activated and each component can be used. Such an image forming apparatus having a plurality of power supplies is not always used by the user after the main switch is turned on, and there is a time in a standby state.

  In the period in which the image forming apparatus is in a standby state, the sleep mode (power saving mode) is set for the purpose of reducing power consumption and reducing heat dissipation to the surrounding environment. When the sleep mode is set, the energization of the components from the 100V power supply and the 24V power supply is cut off, and only the 5V power supply is energized to the components.

  As described in the section of the problem to be solved by the invention, when the image forming apparatus is in a stopped state for a long time, the residual toner and the liquid carrier accumulated between the intermediate transfer belt 70 and the intermediate transfer belt cleaning blade 11 are collected. This causes sticking streaks. If the fixed streaks L remain on the surface of the intermediate transfer belt 70, streaky image distortion may occur in the image formed on the recording medium. Therefore, in the present invention, such a fixed streak is dealt with by supplying a carrier from the photosensitive member and moistening the fixed streak with the carrier. When this fixed streak passes through the intermediate transfer belt cleaning blade 11 next time, the fixed streak is wet with the carrier, so that it can be easily removed by the intermediate transfer belt cleaning blade 11.

  Further, the fixed streak may destroy the surface layer portion of the intermediate transfer belt 70 when the image forming apparatus is restarted. Therefore, in the present invention, the intermediate transfer belt cleaning blade 11 is moved from the intermediate transfer belt 70 when the image forming apparatus is restarted after being stopped for a long time, that is, when the image forming apparatus is turned on or returned from the sleep mode. Measures against such streaks are made by separating them, controlling the rotational speed of the intermediate transfer belt 70, or using a roller-like intermediate transfer belt cleaning mechanism. It is configured as follows. More detailed embodiments will be described later.

  In this embodiment, the case where an intermediate transfer belt is used as the intermediate transfer medium will be described below. However, the problem of the present invention as described above is that the intermediate transfer medium other than the belt, for example, a drum-like one is used. According to the means for solving the problems of the present invention, an effect can be expected even for a drum-shaped medium, and the intermediate transfer medium of the present invention is not necessarily applied to the intermediate transfer belt. It is not limited.

  FIG. 7 shows a cross-sectional configuration of the intermediate transfer belt 70. The base material layer 701 of the intermediate transfer belt 70 is formed of a polyimide resin and has a thickness of 100 μm. On the upper layer of the base material layer 701, an elastic layer 702 made of urethane rubber having a hardness of JIS-A 80 ° is formed with a thickness of 200 μm. An upper side of the elastic layer 702 is a coat layer 703, and a fluororesin coat is applied with a thickness of 10 μm.

  Next, with reference to FIG. 1 again, the toner and carrier remaining on the intermediate transfer belt 70 after the image formed on the intermediate transfer belt 70 is transferred by the secondary transfer unit 80 will be described. Then, it is removed by the intermediate transfer belt cleaning blade 11. This does not occur in the situation where the intermediate transfer belt 70 is continuously rotating, but the situation where the rotation of the intermediate transfer belt 70 is stopped for a long time when the image forming apparatus is in a stopped state for a long time. Below, streaks are generated on the intermediate transfer belt 70 due to residual toner and liquid carrier accumulated between the intermediate transfer belt 70 and the intermediate transfer belt cleaning blade 11.

  If the image forming apparatus is restarted after such a fixed streak is formed and the intermediate transfer belt 70 is rapidly rotated, the surface layer portion of the intermediate transfer belt 70 may be destroyed. Therefore, in order to cope with such a situation, in the present embodiment, a mechanism for separating the intermediate transfer belt cleaning blade 11 (not shown) is provided. The mechanism for separating the intermediate transfer belt cleaning blade 11 is expressed as “intermediate transfer medium cleaning / separating means” in the claims. A mechanism for separating the intermediate transfer belt cleaning blade 11 is provided, and when the image forming apparatus is restarted for a long period of time, the intermediate transfer belt cleaning blade 11 is separated so that the intermediate transfer belt cleaning blade 11 is separated. The transfer belt 70 does not receive a large resistance generated between the transfer belt 70 and the intermediate transfer belt cleaning blade 11 due to the sticking lines when the intermediate transfer belt 70 starts to rotate.

  Further, if the residual toner formed when the image forming apparatus has been stopped for a long period of time and the streaks due to the liquid carrier are present on the surface of the intermediate transfer belt 70, a streak-like image is formed on the image formed on the recording medium. May cause disturbance.

  Therefore, in the present invention, such a fixed streak is dealt with by supplying a carrier from the photosensitive member and moistening the fixed streak with the carrier. The fixed streaks moistened by the carrier can be easily removed by the intermediate transfer belt cleaning blade 11 the next time when passing through the intermediate transfer belt cleaning blade 11.

  Here, the developing units 50Y, 50M, and 50C other than the developing unit 50K are moved downward by the mechanism described above. By this movement, the respective photoconductors 20Y, 20M, and 20C are separated from the intermediate transfer belt 70, and only the photoconductor 20K that handles the black developer comes into contact with the intermediate transfer belt 70.

  FIG. 8 shows a state in which the photoconductors 20Y, 20M, and 20C are separated from the intermediate transfer belt. When the carrier is supplied to the fixed streaks on the intermediate transfer belt 70, only the photoconductor 20K is in contact with the carrier 20K.

  The reason for using only the photoconductor 20K instead of using the photoconductors 20Y, 20M, and 20C for supplying the carrier is that when the carrier is supplied to the intermediate transfer belt 70, residual toner or the like on the intermediate transfer belt 70 adheres to the photoconductor side. However, if the toner adheres to the photoconductor 20K that handles the black developer, the color of the residual toner or the like does not stand out, and the image quality of the image formed thereafter has a great influence. This is because there is not.

  In order to supply the carrier from the photoconductor 20K to the intermediate transfer belt 70, so-called white printing is performed in which the photoconductor 20K is charged by the charging unit 30K and no exposure is performed. At this time, the photosensitive member 20K is rotated at the same speed as the intermediate transfer belt 70. The fixed streaks wetted by the carrier in this way can be easily removed by the intermediate transfer belt cleaning blade 11 the next time it passes through the intermediate transfer belt cleaning blade 11.

  More specifically, in FIG. 8, a location on the intermediate transfer belt 70 that is in contact with the intermediate transfer belt cleaning blade 11 in a state where the intermediate transfer belt 70 is stopped (a location where there is a high possibility that fixing streaks have occurred. ) Until the toner passes through the nip region B between the photoconductor 20K and the intermediate transfer belt 70, the intermediate transfer belt 70 is rotated at a lower speed than the rotation of the normal intermediate transfer belt 70, and the carrier is fixed from the photoconductor 20K. Supply to streaks. The reason why the rotation of the intermediate transfer belt 70 is kept at a lower speed than usual is to pass the portion with the fixed streaks on the intermediate transfer belt 70 more slowly than usual, thereby supplying the carrier to that portion accordingly.

  Here, the normal speed is a speed at which the mechanism for driving the intermediate transfer belt 70 drives the intermediate transfer belt 70 when actually forming an image. FIG. 9 shows the belt speed when the intermediate transfer belt 70 is started. A dotted line is a profile when the intermediate transfer belt 70 is driven at a normal speed, and a solid line is a profile when the intermediate transfer belt 70 is driven at a lower speed than usual. The timing at which the intermediate transfer belt 70 is driven at a lower speed than usual is when the image forming apparatus has been in a stopped state for a long period of time, and there is a possibility that the streaks are fixed on the intermediate transfer belt 70. That is, the intermediate transfer belt 70 is driven at a lower speed than usual when the power is supplied to the image forming apparatus or when the image forming apparatus receives a command and returns from the sleep mode.

  In the claims, a mode in which the mechanism for driving the intermediate transfer belt 70 drives the intermediate transfer belt 70 at a normal speed is expressed as a “first drive mode”, and a mechanism for driving the intermediate transfer belt 70 A mode in which the intermediate transfer belt 70 is driven at a speed lower than the normal speed is expressed as a “second drive mode”.

  As described above, when the intermediate transfer belt 70 is driven at a low speed, the carrier on the intermediate transfer belt 70 is sufficiently supplied with a carrier from the photoconductor 20K [and becomes damp. When passing through the intermediate transfer medium cleaning means, it can be easily removed by the intermediate transfer medium cleaning means, so that the image formed on the recording medium is not disturbed by streak-like images.

  In order for the image forming apparatus to prepare for image formation, the developing units 50Y, 50M, and 50C that have moved downward are raised again, and the respective photoreceptors 20Y, 20M, and 20C are in contact with the intermediate transfer belt 70. Must return to state. FIG. 10 shows the timing at which the photoconductors 20Y, 20M, and 20C are brought into contact with the intermediate transfer belt. Such a timing Tu is before the portion on the intermediate transfer belt 70 where the fixing streaks are formed passes through the nip region B, and the nip region C between the photoconductor 20C and the intermediate transfer belt 70 is moved to the corresponding portion. After the image has passed, it is the earliest timing for starting up the image forming apparatus, which is efficient in executing the subsequent startup sequence of the image forming apparatus.

  As described above, as the period during which the intermediate transfer belt 70 is rotationally driven at a low speed, the portion on the intermediate transfer belt 70 that is in the nip region A between the intermediate transfer belt 70 and the intermediate transfer belt cleaning blade 11 is It is not necessary to limit the nip region B between the photosensitive member 20K and the intermediate transfer belt 70 until it passes once.

  If necessary, the intermediate transfer belt 70 can be continuously rotated several times to supply more carriers to the fixing lines, and the number of passes through the nip region between the photoconductor 20K and the intermediate transfer belt 70 can be increased. . In this way, it can be expected that the cleaning effect becomes higher.

  Next, another embodiment according to the present invention will be described. In the above embodiment, if the image forming apparatus is restarted after the fixing streaks are formed and the intermediate transfer belt 70 is rapidly turned, the surface layer portion of the intermediate transfer belt 70 may be destroyed. In order to cope with this, a mechanism for separating the intermediate transfer belt cleaning blade 11 is provided. However, in this embodiment, such a mechanism for separating the intermediate transfer belt cleaning blade 11 is not provided. Instead of providing such a mechanism for separating the intermediate transfer belt cleaning blade 11, in this embodiment, when the intermediate transfer belt 70 is started to rotate, the rise of the belt speed is made slower than when the belt is normally raised. By doing so, the resistance generated between the intermediate transfer belt cleaning blade 11 and the intermediate transfer belt 70 due to the fixing streaks is reduced.

  FIG. 11 shows how the belt speed rises when the intermediate transfer belt 70 is started. A dotted line indicates a state when the rotational speed of the intermediate transfer belt 70 is raised at a normal time, and a solid line indicates a state when the rotational speed of the intermediate transfer belt 70 is gradually raised from a normal time. Here, increasing the rotational speed of the intermediate transfer belt 70 to normal means that the intermediate transfer belt 70 is instantaneously brought to the rotational speed at the time of image formation as shown by the dotted line in FIG. . On the other hand, when there is a possibility that the streaks have been formed on the intermediate transfer belt 70, the rotational speed of the intermediate transfer belt 70 is raised more slowly than usual. By doing so, the resistance generated between the intermediate transfer belt cleaning blade 11 and the intermediate transfer belt 70 due to the fixing streaks can be reduced, so that the surface of the intermediate transfer belt 70 is prevented from being destroyed. it can.

  In the claims, a mode in which the rotation speed of the intermediate transfer belt 70 is raised at the normal time is expressed as a “third drive mode”, and a mode in which the rotation speed of the intermediate transfer belt 70 is gradually raised from the normal time is “ This is expressed as “fourth drive mode”.

  If the residual toner that has been formed when the image forming apparatus has been stopped for a long time and the streaks due to the liquid carrier are on the surface of the intermediate transfer belt 70, the image formed on the recording medium is disturbed in the form of streaks. In order to deal with this, in the present embodiment, after the rotation speed of the intermediate transfer belt 70 is raised more slowly than usual, the same as in the previous embodiment. The fixed streaks are dealt with by supplying a carrier from the photoconductor 20K and moistening the fixed streaks with the carrier.

  Also in this embodiment, when the carrier is supplied from the photosensitive member 20K to the fixing stripe, the photosensitive members 20Y, 20M, and 20C are separated from the intermediate transfer belt 70 as shown in FIG. Only the photoconductor 20K is in contact.

  In order to supply the carrier from the photoconductor 20K to the intermediate transfer belt 70, so-called white printing is performed in which the photoconductor 20K is charged by the charging unit 30K and no exposure is performed. At this time, the photosensitive member is rotated at the same speed as the intermediate transfer belt 70. The fixed streaks moistened by the carrier can be easily removed by the intermediate transfer belt cleaning blade 11 the next time when passing through the intermediate transfer belt cleaning blade 11.

  Also in the present embodiment, at least the location on the intermediate transfer belt 70 that has been in contact with the intermediate transfer belt cleaning blade 11 in a state where the intermediate transfer belt 70 is stopped (the location where there is a high possibility of fixing streaks) is at least. Until the first photosensitive member 20K and the intermediate transfer belt 70 pass through the nip region B, the intermediate transfer belt 70 is rotated at a lower speed than the normal rotation of the intermediate transfer belt 70 to fix the carrier from the photosensitive member 20K. To supply. The reason why the rotation of the intermediate transfer belt 70 is kept at a lower speed than usual is to pass the portion with the fixed streaks on the intermediate transfer belt 70 more slowly than usual, thereby supplying the carrier to that portion accordingly.

  Here, the normal speed is a speed at which the mechanism for driving the intermediate transfer belt 70 drives the intermediate transfer belt 70 when actually forming an image. FIG. 12 shows how the belt speed increases when the intermediate transfer belt 70 is started in another embodiment of the present invention. A dotted line is a profile when the intermediate transfer belt 70 is driven at a normal speed, and a solid line is a profile when the intermediate transfer belt 70 is driven at a lower speed than usual. As shown by the solid line profile, in this embodiment, in addition to driving the intermediate transfer belt 70 at a lower speed than usual, the rise in the rotational speed of the intermediate transfer belt 70 is also gentler than usual.

  As described above, the timing at which the intermediate transfer belt 70 is driven at a lower speed than usual is when the image forming apparatus has been in a stationary state for a long period of time, and there is a possibility that the streaks are fixed on the intermediate transfer belt 70. That is, the intermediate transfer belt 70 is driven at a lower speed than usual when the power is supplied to the image forming apparatus or when the image forming apparatus receives a command and returns from the sleep mode.

  In the claims, the mode in which the mechanism for driving the intermediate transfer belt drives the intermediate transfer belt 70 at a normal speed is expressed as “fifth drive mode”, and the mechanism for driving the intermediate transfer belt is the intermediate transfer belt. A mode in which the belt 70 is driven at a speed lower than the normal speed is expressed as a “sixth drive mode”.

  As described above, by driving the intermediate transfer belt 70 at a low speed, the carrier on the intermediate transfer belt 70 is sufficiently supplied with a carrier to be in a damp state. When passing through the cleaning unit, the intermediate transfer medium cleaning unit can easily remove it, so that the image formed on the recording medium is not disturbed by streak-like images.

  In order for the image forming apparatus to prepare for image formation, the developing units 50Y, 50M, and 50C that have moved downward are raised again, and the respective photoreceptors 20Y, 20M, and 20C are in contact with the intermediate transfer belt 70. Must return to state. FIG. 13 shows the timing at which the photoconductors 20Y, 20M, and 20C are brought into contact with the intermediate transfer belt. Such a timing Tu is before the portion on the intermediate transfer belt 70 where the fixing streaks are formed passes through the nip region B, and the nip region C between the photoconductor 20C and the intermediate transfer belt 70 is moved to the corresponding portion. After the image has passed, it is the earliest timing for starting up the image forming apparatus, which is efficient in executing the subsequent startup sequence of the image forming apparatus.

  Also in this embodiment, as the period during which the intermediate transfer belt 70 is rotationally driven at a low speed, the portion on the intermediate transfer belt 70 that is in the nip region A between the intermediate transfer belt 70 and the intermediate transfer belt cleaning blade 11 is the same. It is not necessary to limit the nip region B between the photosensitive member 20K and the intermediate transfer belt 70 until it passes once.

  If necessary, the intermediate transfer belt 70 can be continuously rotated several times to supply more carriers to the fixing lines, and the number of passes through the nip region between the photoconductor 20K and the intermediate transfer belt 70 can be increased. . In this way, it can be expected that the cleaning effect becomes higher.

  Next, another embodiment according to the present invention will be described. In the previous embodiment, when the image forming apparatus is restarted after the fixing streaks have been formed, if the intermediate transfer belt 70 is suddenly turned, the surface layer portion of the intermediate transfer belt 70 may be destroyed. In order to cope with this, a mechanism for separating the intermediate transfer belt cleaning blade 11 is not provided, and when the intermediate transfer belt 70 is started to rotate, the rise of the belt speed is set to be slower than when the belt is normally started. By setting in this way, the resistance generated between the intermediate transfer belt cleaning blade 11 and the intermediate transfer belt 70 due to the fixing streaks is reduced. In contrast, in this embodiment, the intermediate transfer belt cleaning roller 12 is provided as a cleaning mechanism for the intermediate transfer belt 70 for removing residual toner and carrier on the intermediate transfer belt 70.

  FIG. 14 shows main components constituting an image forming apparatus according to another embodiment of the present invention. 1 is that the mechanism for cleaning the intermediate transfer belt 70 is the intermediate transfer belt cleaning roller 12 as described above. The intermediate transfer belt cleaning roller 12 is configured by winding a urethane shaft having a thickness of 2 mm and a hardness of JIS-A 30 ° on a metal shaft having a diameter of 10 mm and further winding a PFA tube of 20 μm. The intermediate transfer belt cleaning roller 12 has a width of 307 mm and is brought into contact with the intermediate transfer belt 70 at a linear pressure of about 50 gf / cm. The resistance value of the intermediate transfer belt cleaning roller 12 is about Log 4Ω, and a bias of 150 V is applied between the intermediate transfer belt cleaning roller 12 and the cleaning backup roller.

  In the present embodiment, since the intermediate transfer belt cleaning roller 12 having a low resistance to the intermediate transfer belt 70 is used as the cleaning mechanism for the intermediate transfer belt 70, the belt particularly when the intermediate transfer belt 70 starts to rotate. The resistance caused by the sticking streaks can be alleviated without making the rise in speed more gradual than when starting up at normal times.

  If the residual toner that has been formed when the image forming apparatus has been stopped for a long time and the streaks due to the liquid carrier are on the surface of the intermediate transfer belt 70, the image formed on the recording medium is disturbed in the form of streaks. May cause.

  Therefore, in the present invention, such a fixed streak is dealt with by supplying a carrier from the photosensitive member and moistening the fixed streak with the carrier.

  Here, the developing units 50Y, 50M, and 50C other than the developing unit 50K are moved downward by the mechanism described above. By this movement, the respective photoconductors 20Y, 20M, and 20C are separated from the intermediate transfer belt 70, and only the photoconductor 20K that handles the black developer comes into contact with the intermediate transfer belt 70.

  The reason for using only the photoconductor 20K instead of using the photoconductors 20Y, 20M, and 20C for supplying the carrier is that when the carrier is supplied to the intermediate transfer belt 70, residual toner or the like on the intermediate transfer belt 70 adheres to the photoconductor side. However, if the toner adheres to the photoconductor 20K that handles the black developer, the color of the residual toner or the like does not stand out, and the image quality of the image formed thereafter has a great influence. This is because there is not.

  In order to supply the carrier from the photoconductor 20K to the intermediate transfer belt 70, so-called white printing is performed in which the photoconductor 20K is charged by the charging unit 30K and no exposure is performed. At this time, the photosensitive member is rotated at the same speed as the intermediate transfer belt 70. The fixed streaks moistened by the carrier can be easily removed by the intermediate transfer belt cleaning roller 12 the next time it passes through the intermediate transfer belt cleaning roller 12.

  More specifically, in FIG. 14, a location on the intermediate transfer belt 70 that is in contact with the intermediate transfer belt cleaning roller 12 in a state where the intermediate transfer belt 70 is stopped (a location where the sticking streak is highly likely to have occurred). ) At least until the first intermediate photosensitive belt 20K and the intermediate transfer belt 70 pass through the nip region B, the intermediate transfer belt 70 is rotated at a lower speed than the rotation of the normal intermediate transfer belt 70. Supply the carrier to the fixed streaks. The reason why the rotation of the intermediate transfer belt 70 is kept at a lower speed than usual is to pass the portion with the fixed streaks on the intermediate transfer belt 70 more slowly than usual, thereby supplying the carrier to that portion accordingly.

  Here, the normal speed is a speed at which the mechanism for driving the intermediate transfer belt 70 drives the intermediate transfer belt 70 when actually forming an image. FIG. 8 shows the belt speed when the intermediate transfer belt 70 is started. A dotted line is a profile when the intermediate transfer belt 70 is driven at a normal speed, and a solid line is a profile when the intermediate transfer belt 70 is driven at a lower speed than usual. The timing at which the intermediate transfer belt 70 is driven at a lower speed than usual is when the image forming apparatus has been in a stopped state for a long period of time, and there is a possibility that the streaks are fixed on the intermediate transfer belt 70. That is, the intermediate transfer belt 70 is driven at a lower speed than usual when the power is supplied to the image forming apparatus or when the image forming apparatus receives a command and returns from the sleep mode.

  In the claims, a mode in which the mechanism for driving the intermediate transfer belt 70 drives the intermediate transfer belt 70 at a normal speed is expressed as a “first drive mode”, and a mechanism for driving the intermediate transfer belt 70 A mode in which the intermediate transfer belt 70 is driven at a speed lower than the normal speed is expressed as a “second drive mode”.

  As described above, by driving the intermediate transfer belt 70 at a low speed, the carrier on the intermediate transfer belt 70 is sufficiently supplied with carrier from the photosensitive member and becomes damp. When passing through the cleaning roller 12, it can be easily removed by the intermediate transfer belt cleaning roller 12, so that the image formed on the recording medium is not disturbed by streak-like images.

  In order for the image forming apparatus to prepare for image formation, the developing units 50Y, 50M, and 50C that have moved downward are raised again, and the respective photoreceptors 20Y, 20M, and 20C are in contact with the intermediate transfer belt 70. Must return to state. FIG. 10 shows the timing at which the photoconductors 20Y, 20M, and 20C are brought into contact with the intermediate transfer belt. Such a timing Tu is before the portion on the intermediate transfer belt 70 where the fixing streaks are formed passes through the nip region B, and the nip region C between the photoconductor 20C and the intermediate transfer belt 70 is moved to the corresponding portion. After the image has passed, it is the earliest timing for starting up the image forming apparatus, which is efficient in executing the subsequent startup sequence of the image forming apparatus.

  Also in this embodiment, as a period during which the intermediate transfer belt 70 is rotationally driven at a low speed, the portion on the intermediate transfer belt 70 that is in the nip region A between the intermediate transfer belt 70 and the intermediate transfer belt cleaning roller 12 is the same. It is not necessary to limit the nip region B between the photosensitive member 20K and the intermediate transfer belt 70 until it passes once.

If necessary, the intermediate transfer belt 70 can be continuously rotated several times to supply more carriers to the fixing lines, and the number of passes through the nip region between the photoconductor 20K and the intermediate transfer belt 70 can be increased. . In this way, it can be expected that the cleaning effect becomes higher.

1 is a diagram illustrating main components constituting an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a control unit of the image forming apparatus in FIG. 1. It is sectional drawing which showed the main components of the developing unit. 5 is a perspective conceptual diagram showing the surface of a developer supply roller 550. FIG. 5A to 5C are cross-sectional views showing the shapes of grooves provided on the surface of the developer supply roller 550. FIG. 6 is a schematic diagram illustrating trail regulation of a regulation blade 560. 2 is a diagram showing a cross-sectional configuration of an intermediate transfer belt 70. FIG. 2 is a diagram illustrating a state where the photoconductors 20Y, 20M, and 20C are separated from the intermediate transfer belt 70. FIG. FIG. 6 is a diagram illustrating a belt speed when the intermediate transfer belt 70 is started. FIG. 6 is a diagram illustrating timing for bringing photoconductors 20Y, 20M, and 20C into contact with the intermediate transfer belt 70. FIG. 4 is a diagram illustrating how the belt speed rises when the intermediate transfer belt is started. FIG. 6 is a diagram showing a belt speed at the start of an intermediate transfer belt 70 in another embodiment according to the present invention. FIG. 6 is a diagram illustrating timing for bringing photoconductors 20Y, 20M, and 20C into contact with the intermediate transfer belt 70. It is a figure which shows the main components which comprise the image forming apparatus of other embodiment which concerns on this invention. It is a schematic block diagram of the conventional image forming apparatus of a wet electrophotographic system. FIG. 6 is a diagram illustrating a relationship between an intermediate transfer belt and an intermediate transfer belt cleaning blade of a conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Laser beam printer 11 ... Intermediate transfer belt cleaning blade 12 ... Intermediate transfer belt cleaning rollers 15Y, 15M, 15C, 15K ... Development units 20Y, 20M, 20C, 20K ... Photoconductor 30Y , 30M, 30C, 30K ... charging units 40Y, 40M, 40C, 40K ... exposure unit optical path 50Y, 50M, 50C, 50K ... development units 60Y, 60M, 60C, 60K ... primary transfer unit 70 ... Intermediate transfer belts 73Y, 73M, 73C, 73K ... Static elimination units 75Y, 75M, 75C, 75K ... Photoconductor cleaning units 76Y, 76M, 76C, 76K ... Photoconductor cleaning blade 80 ... Secondary transfer unit 100 ... control unit, 101 ... main Controller 102 ... unit controller, 112 ... interface 113 ... image memory, 120 ... CPU
510 ... developing roller, 530 ... developer receiving portion 540 ... developer pumping roller 550 ... developer supply roller, 550a ... groove 560 ... regulating blade, 560a ... edge portion 562 ... Restricting blade support member 570 ... Developing roller cleaning unit 571 ... Developing roller cleaning blade

Claims (14)

Developing means for developing an electrostatic latent image formed on the photoreceptor with a developer in which toner is dispersed in a carrier;
Primary transfer means for transferring an image developed on the photoreceptor to an intermediate transfer medium;
Secondary transfer means for transferring the image transferred to the intermediate transfer medium to a recording medium;
Fixing means for heating and pressurizing the image transferred to the recording medium and fixing the image on the recording medium;
Intermediate transfer medium cleaning means for removing the carrier and toner remaining on the intermediate transfer medium from the surface of the intermediate transfer medium after transferring the image transferred to the intermediate transfer medium to the recording medium;
Intermediate transfer medium driving means for driving the intermediate transfer medium,
The developing means is composed of four developing means, each of a first developing means, a second developing means, a third developing means, and a fourth developing means, each handling a different color developer.
Of the four developing units of the first developing unit, the second developing unit, the third developing unit, and the fourth developing unit, three developing units other than the developing unit handling the black developer are transferred from the intermediate transfer medium. In the image forming apparatus provided with the developing unit separating and contacting mechanism for separating and contacting,
An intermediate transfer medium cleaning and separating means for temporarily separating the intermediate transfer medium cleaning means from the intermediate transfer medium;
As a drive mode when the intermediate transfer medium driving means drives the intermediate transfer medium,
A first driving mode in which the intermediate transfer medium is rotated at a normal driving speed for image formation;
A second drive mode in which the intermediate transfer medium is rotated at a lower speed than the first drive mode for a certain period,
The intermediate transfer medium driving unit is configured such that the developing unit separating mechanism separates the three developing units, the intermediate transfer medium cleaning separating unit separates the intermediate transfer medium cleaning unit, and then the intermediate transfer medium driving unit in the second driving mode. An image forming apparatus that rotates a medium. The intermediate transfer medium driving means performs driving in the second driving mode.
The image forming apparatus according to claim 1, wherein the image forming apparatus is performed when power is turned on or when returning from the sleep mode. The portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning means while the intermediate transfer medium is stopped passes through the nip region between the developing means that handles black developer and the intermediate transfer medium. 3. The image forming apparatus according to claim 1, wherein the intermediate transfer medium is rotated in a second drive mode for a period until the end. The developing means that handles the black developer is the fourth developing means, and the portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning means while the intermediate transfer medium is stopped is the fourth developing means. 3. The developing device separating mechanism causes the three developing devices to contact the intermediate transfer medium after passing through a nip region between the developing device and the intermediate transfer medium. The image forming apparatus according to any one of the above. Developing means for developing an electrostatic latent image formed on the photoreceptor with a developer in which toner is dispersed in a carrier;
Primary transfer means for transferring an image developed on the photoreceptor to an intermediate transfer medium;
Secondary transfer means for transferring the image transferred to the intermediate transfer medium to a recording medium;
Fixing means for heating and pressurizing the image transferred to the recording medium and fixing the image on the recording medium;
Intermediate transfer medium cleaning means for removing the carrier and toner remaining on the intermediate transfer medium from the surface of the intermediate transfer medium after transferring the image transferred to the intermediate transfer medium to the recording medium;
Intermediate transfer medium driving means for driving the intermediate transfer medium,
The developing means is composed of four developing means, each of a first developing means, a second developing means, a third developing means, and a fourth developing means, each handling a different color developer.
Of the four developing units of the first developing unit, the second developing unit, the third developing unit, and the fourth developing unit, three developing units other than the developing unit handling the black developer are transferred from the intermediate transfer medium. In the image forming apparatus provided with the developing unit separating and contacting mechanism for separating and contacting,
As a drive mode when the intermediate transfer medium driving unit drives the intermediate transfer medium from a state where the intermediate transfer medium is stopped to a state where the intermediate transfer medium is rotated at a normal driving speed at the time of image formation,
A third drive mode for causing the intermediate transfer medium to instantaneously reach the normal drive speed;
An image forming apparatus comprising: a fourth drive mode that takes time to reach the normal drive speed from the third drive mode. A fifth driving mode in which the intermediate transfer medium is rotated at a normal driving speed for image formation;
A sixth drive mode for rotating the intermediate transfer medium for a certain period at a lower speed than the fifth drive mode,
The intermediate transfer medium driving unit rotates the intermediate transfer medium in the fourth drive mode and then rotates the intermediate transfer medium in the sixth drive mode when the power is turned on or when returning from the sleep mode. The image forming apparatus according to claim 5. The portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning unit while the intermediate transfer medium is stopped passes through the nip region between the developing unit that handles black developer and the intermediate transfer medium. The image forming apparatus according to claim 6, wherein the intermediate transfer medium is rotated in a sixth drive mode for a period until completion. The developing means that handles the black developer is the fourth developing means, and the portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning means while the intermediate transfer medium is stopped is the fourth developing means. 8. The developing means separating mechanism causes the three developing means to contact the intermediate transfer medium after passing through the nip region between the developing means and the intermediate transfer medium. The image forming apparatus according to any one of the above. The image forming apparatus according to claim 1, wherein the intermediate transfer medium cleaning unit is a cleaning blade. Developing means for developing an electrostatic latent image formed on the photoreceptor with a developer in which toner is dispersed in a carrier;
Primary transfer means for transferring an image developed on the photoreceptor to an intermediate transfer medium;
Secondary transfer means for transferring the image transferred to the intermediate transfer medium to a recording medium;
Fixing means for heating and pressurizing the image transferred to the recording medium and fixing the image on the recording medium;
Intermediate transfer medium cleaning means for removing the carrier and toner remaining on the intermediate transfer medium from the surface of the intermediate transfer medium after transferring the image transferred to the intermediate transfer medium to the recording medium;
Intermediate transfer medium driving means for driving the intermediate transfer medium,
The developing means is composed of four developing means, each of a first developing means, a second developing means, a third developing means, and a fourth developing means, each handling a different color developer.
Of the four developing units of the first developing unit, the second developing unit, the third developing unit, and the fourth developing unit, three developing units other than the developing unit handling the black developer are transferred from the intermediate transfer medium. In the image forming apparatus provided with the developing unit separating and contacting mechanism for separating and contacting,
As a drive mode when the intermediate transfer medium driving means drives the intermediate transfer medium,
A first driving mode in which the intermediate transfer medium is rotated at a normal driving speed for image formation;
An image forming apparatus comprising: a second driving mode in which the intermediate transfer medium is rotated at a lower speed than the first driving mode for a certain period. The intermediate transfer medium driving means performs driving in the second driving mode.
The image forming apparatus according to claim 10, wherein the image forming apparatus is performed when power is turned on or when returning from the sleep mode. The portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning means while the intermediate transfer medium is stopped is a nip region between the developing means that handles the black developer and the intermediate transfer medium. 12. The image forming apparatus according to claim 10, wherein the intermediate transfer medium is rotated in the second drive mode for a period until passing. The developing means that handles the black developer is the fourth developing means, and the portion on the intermediate transfer medium that has been in contact with the intermediate transfer medium cleaning means while the intermediate transfer medium is stopped is the fourth developing means. 13. The developing device separating mechanism causes the three developing devices to contact the intermediate transfer medium after passing through the nip region between the developing device and the intermediate transfer medium. The image forming apparatus according to any one of the above. The image forming apparatus according to claim 10, wherein the intermediate transfer medium cleaning unit is a cleaning roller.

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