JP2016212366A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: when a cleaning body is driven to clean an image carrier while in contact with the image carrier, if the image carrier and the cleaning body are driven by separate driving sources, image carrier driving control may not be satisfactorily performed due to an influence of the drive for cleaning at the start-up of the drive.SOLUTION: An image forming apparatus 1 comprises: an image carrier 2; image carrier driving means 2BM that drives the image carrier; a cleaning body 10 that is in contact with the image carrier; and cleaning body driving means 113 that drives the cleaning body and is different from the image carrier driving means. The image forming apparatus starts the drive of the image carrier driving means before starting the drive of the cleaning body driving means.SELECTED DRAWING: Figure 15

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus such as a printer, a facsimile machine, and a copying machine, an electrostatic cleaning type cleaning device that removes toner using electrostatic force as an intermediate transfer belt cleaning device that removes transfer residual toner on an intermediate transfer belt The one that adopts is known.

  The electrostatic cleaning type cleaning device described in Patent Document 1 is provided with a cleaning brush roller that rotates while contacting an intermediate transfer belt that is a member to be cleaned, and a collection roller that rotates while contacting this. The cleaning brush roller and the collection roller are rotatably held in the casing. A cleaning voltage is applied to the cleaning brush roller, and a recovery voltage is applied to the recovery roller.

  Transfer residual toner adhering to the surface of the intermediate transfer belt is electrostatically transferred from the surface of the intermediate transfer belt to the cleaning brush roller by the cleaning voltage, and is removed from the intermediate transfer belt. The toner electrostatically transferred to the cleaning brush roller is conveyed to a contact position with the recovery roller by the rotation of the cleaning brush roller, electrostatically transferred to the recovery roller by the recovery voltage, and recovered from the cleaning brush roller to the recovery roller.

  Further, the inventors have proposed that a cleaning roller is mounted downstream of the cleaning brush roller as an improved cleaning device of the electrostatic cleaning system described in Patent Document 1.

  However, in the above-described cleaning apparatus, when a large number of machines are manufactured, there are cases where a machine in which the drive control of the intermediate transfer belt becomes unstable due to variations. When the driving of the intermediate transfer belt becomes unstable, the image is not properly transferred and an abnormal image is generated. Alternatively, if an abnormal display is performed when the speed is unstable to prevent such an abnormal image, the abnormal display is frequently turned on.

  In order to solve the above-described problems, the present invention provides an image carrier, an image carrier, an image carrier driving unit that drives the image carrier, a cleaning body that contacts the image carrier, and the cleaning body. And a cleaning body driving unit that is different from the image carrier driving unit. The driving of the cleaning body driving unit is started after the driving of the image carrier driving unit is started.

  As described above, according to the present invention, since the driving of the cleaning body is started after the driving of the image carrier such as the intermediate transfer belt is started, the load due to the driving of the cleaning body after the driving of the image carrier such as the intermediate transfer belt is stabilized. This is applied as a load for driving the image carrier. This facilitates drive control of the image carrier such as the intermediate transfer belt, enables stable drive control, and prevents occurrence of abnormal images or frequent display of abnormal images.

1 is a schematic configuration diagram showing an overall configuration of a copier according to an embodiment. FIG. 3 is an enlarged cross-sectional view illustrating a layer configuration of an intermediate transfer belt. FIG. 3 is an enlarged schematic configuration diagram in the vicinity of a secondary transfer belt showing a gradation pattern and an optical sensor. FIG. 3 is an enlarged schematic view showing a chevron patch transferred to the secondary transfer belt. The schematic diagram of the toner consumption pattern transcribe | transferred to the secondary transfer belt. FIG. 3 is an enlarged configuration diagram illustrating an intermediate transfer belt cleaning device and its surroundings in an enlarged manner. The graph which shows the relationship between the voltage applied to a post-cleaning roller, and the number of spots-like image generation. The graph which shows the relationship between the number of the spot-like image generation | occurrence | production in a normal temperature and normal humidity environment, and a low temperature and low humidity environment, and the applied voltage to a post-cleaning roller. 6 is a graph comparing the number of spot-like images generated when a positive voltage is applied to the post-cleaning roller and the number of spot-like images generated when a negative voltage is applied to the post-cleaning roller. The graph which investigated the number of the spot-like image generation | occurrence | production of the comparative example 1 and Examples 1-4. 6 is a graph showing a relationship between a linear velocity difference between a post cleaning roller and an intermediate transfer belt and a torque of a intermediate transfer drive motor that drives the intermediate transfer belt. 6 is a graph showing a relationship between a linear velocity difference between a post cleaning roller and an intermediate transfer belt and a torque of a drive motor of the intermediate transfer belt cleaning device. The graph which investigated the relationship between the amount of biting with respect to the intermediate transfer belt of a post cleaning roller, and the number of spots-like abnormal image generation. The graph which investigated the correlation with brush flocking density and brush thickness. 6 is a timing chart showing bias applied to the cleaning brush roller and post cleaning roller, bias applied to each recovery roller, and on / off timing of driving of the intermediate transfer belt and driving of the intermediate transfer belt cleaning device. FIG. 3 is a schematic configuration diagram illustrating a power supply unit included in the intermediate transfer belt cleaning device. The flowchart of an example of a voltage setting value change process. FIG. 3 is a schematic diagram of a speed detection unit that detects the speed of an intermediate transfer belt. 6 is a graph showing an example of a relationship between an intermediate transfer belt drive timing and an intermediate transfer belt cleaning drive timing.

  FIG. 1 is a schematic configuration diagram illustrating an overall configuration of a copying machine 1 according to the embodiment. The copying machine 1 has a tandem configuration in which a plurality of photoreceptors 3 (Y, C, M, B) serving as latent image carriers that carry color toner images corresponding to color separation are juxtaposed. The toner images formed on the respective photoreceptors 3 (Y, C, M, B) are superimposed and transferred (primary transfer) so as to overlap each other on an intermediate transfer belt 2 as an intermediate transfer member that is an image carrier. The superimposed toner image is collectively transferred (secondary transfer) to a recording sheet as a recording material. In this way, the copying machine 1 can form a multi-color image on the recording paper.

  In FIG. 1, a copying machine 1 serving as an image forming apparatus has an image forming unit 1A positioned at the center in the vertical direction, a sheet feeding unit 1B below it, and a document reading unit 1C above the image forming unit 1A. , Each is arranged.

  An intermediate transfer belt 2 having a horizontally extending surface is disposed in the image forming unit 1A. In the image forming unit 1A, four photosensitive members 3 (Y, C, M, B) carrying toner images of complementary colors (yellow, magenta, cyan, black) are extended on the intermediate transfer belt 2. It is juxtaposed along the surface. In the following description, in the case of contents common to all colors, Y, C, M, and B, which are color-coded codes, are omitted as appropriate.

  Each photoconductor 3 (Y, C, M, B) is composed of a drum that can rotate in the same direction (counterclockwise in FIG. 1). Around the periphery, a charging device 4, a writing device 5, a developing device 6, a primary transfer device, and a cleaning device 8 that perform image forming processing in a rotating process are arranged to form an image forming unit 66. In FIG. 1, for convenience, the reference numerals of the respective devices are assigned to the black photoconductor 3 </ b> B.

  To the intermediate transfer belt 2, toner images on the photoreceptors 3 (Y, C, M, and B) are sequentially transferred by a primary transfer device. The intermediate transfer belt 2 is wound around a plurality of belt stretching rollers (2A to 2D) and driven to rotate. As a belt stretching roller different from the two belt stretching rollers (2A, 2B) constituting the stretched surface, a bias having the same polarity as the toner is opposed to the secondary transfer device 9 with the intermediate transfer belt 2 interposed therebetween. Is provided with a secondary rolling opposing roller 2C. Furthermore, as another belt stretching roller, a tension roller 2D is provided. The intermediate transfer belt 2 is driven by a driving roller 2B. The driving roller 2B is driven by an intermediate transfer driving device which is an image carrier driving means. Specifically, the intermediate transfer driving device is composed of a driving system including an intermediate transfer belt driving motor 2BM and a gear. An intermediate transfer belt drive motor 2BM is installed near the black photoreceptor on the back of the copying machine 1, and the drive is transmitted to the drive roller 2B of the intermediate transfer belt unit by a drive gear or the like.

  The intermediate transfer driving device may be provided inside the intermediate transfer unit. The intermediate transfer driving device has a speed detection unit for the intermediate transfer belt 2. As shown in FIG. 18, lines 70 are printed at regular intervals at the end of the belt back 2A, and this is read by the reflection type optical sensor 71 to detect the belt speed. Based on the signal from the speed detection unit, the control unit 200 adjusts the voltage or current of the intermediate transfer belt drive motor 2BM that drives the intermediate transfer belt 2 to keep the speed of the intermediate transfer belt 2 constant. A brushless DC motor can be used as the intermediate transfer belt drive motor 2BM. Specifically, the position control method is adopted, the ideal position of the belt is compared with the actual belt position at a specified sampling cycle (eg, every 5 [μs]), and the motor applied voltage is determined according to the advance / delay of the position. Adjust and correct the belt advance / delay by adjusting the motor speed. The speed detection method is not limited to this. For example, an encoder may be attached to one of the driven rollers, and speed detection control may be performed based on the signal. The reflection type photosensor 71 is disposed between the primary transfer rollers 7Y, 7C, and 7M of the color and the primary transfer roller 7B of black, near the primary transfer roller 7B of black. As will be described later, the color primary transfer rollers 7Y, 7C, and 7M are sometimes separated from the color photoconductors, so that the linear velocity can be detected even in such a case.

  When the speed of the intermediate transfer belt 2 fluctuates, the influence on the image quality is great, for example, the color alignment described later becomes meaningless. For this reason, it is important to control the speed fluctuation so as not to exceed a predetermined value. If the speed fluctuation does not fall within this predetermined range for some reason, the machine is stopped and an abnormal display is displayed. In the apparatus of the present embodiment, the deviation between the signal interval corresponding to the scale 70 from the reflection type optical sensor 71 and the reference value is always accumulated, and if the accumulated value exceeds a predetermined value, it is determined as abnormal and the machine is stopped. Abnormal display. For example, the deviation between the signal interval and the reference value at a certain detection timing is +5 [%], and the deviation between the signal interval and the reference value at the next detection timing is -3 [%]. In this case, the cumulative value is (+5 [%]) + (-3 [%]) = + 2 [%]. The predetermined value serving as the abnormality determination threshold is 7 [%] or less, preferably 5 [%] or less.

  Transfer residual toner remaining on the intermediate transfer belt 2 after the secondary transfer is removed by the intermediate transfer belt cleaning device 10. The intermediate transfer belt cleaning device 10 is an electrostatic cleaning system, and applies a bias to a cleaning roller or a cleaning brush, and electrostatically adsorbs the transfer residual toner adhering to the intermediate transfer belt 2 for cleaning.

  The secondary transfer device 9 includes a secondary transfer belt 9C, and the secondary transfer belt 9C is wound around four secondary transfer belt support rollers (9D, 9E, 9F, 9G). Then, when one of the four secondary transfer belt support rollers is rotationally driven as a drive roller, the secondary transfer belt 9C rotates counterclockwise in FIG.

  In the copier 1 of the embodiment shown in FIG. 1, a conveyance belt 91 is provided between the secondary transfer belt 9 </ b> C and the fixing device 11. The conveyor belt 91 is wound around a conveyor belt drive roller 91A and a conveyor belt driven roller 91B, and rotates in the counterclockwise direction in FIG. 1 when the conveyor belt drive roller 91 is rotationally driven.

  The optical sensor unit 300 is disposed at a position facing the surface of the secondary transfer belt 9C on the downstream side in the surface movement direction of the secondary transfer belt 9C with respect to the secondary transfer portion where the secondary transfer belt 9C faces the intermediate transfer belt 2. doing. Further, a secondary transfer belt cleaning device 90 for removing foreign matters on the surface of the secondary transfer belt 9C is provided on the downstream side of the surface of the secondary transfer belt 9C with respect to the position where the optical sensor unit 300 faces.

  One of the four secondary transfer belt support rollers is applied with a secondary transfer bias having the same polarity as the toner on the belt, with the secondary transfer belt 9C and the intermediate transfer belt 2 sandwiched between the secondary transfer portions. This is a secondary transfer roller 9D facing the next transfer counter roller 2C. A support roller 9E disposed on the left side of the drawing with respect to the secondary transfer roller 9D receives the recording paper carried on the surface of the secondary transfer belt 9C by the conveyance belt 91 after passing through the secondary transfer portion. This is a separation roller 9E that stretches the secondary transfer belt 9C at the sheet separation portion that is passed. The support roller 9F disposed below the separation roller 9E is a sensor facing roller 9F that stretches the secondary transfer belt 9C at a detection position where the secondary transfer belt 9C faces the optical sensor unit 300. Further, a support roller disposed on the right side of the sensor facing roller 9F in the drawing is a secondary transfer belt cleaning facing roller 9G that stretches the secondary transfer belt 9C at a position where the cleaning blade of the secondary transfer belt cleaning device 90 contacts. It is.

  The secondary transfer belt 9C used in the embodiment is a single-layer belt. Specific examples include carbon dispersion in materials such as PI (polyimide), PAI (polyamideimide), PC (polycarbonate), ETFE (ethylene-tetrafluoroethylene), PVDF (polyvinylidene fluoride), and PPS (polyphenylene sulfide). Alternatively, a medium resistance resin single layer whose resistance is adjusted by blending an ionic conductive agent can be used. Further, a belt having a surface layer slightly higher in resistance than the volume resistivity of the belt layer itself may be provided only on the surface side of the secondary transfer belt 9C having a single layer structure. In this case, the surface layer thickness is preferably about 1 to 10 [μm].

  In the copying machine 1 of the embodiment, one of the four secondary transfer belt support rollers is rotationally driven as a drive roller, so that the secondary transfer belt 9C is in the middle of the secondary transfer portion that contacts the intermediate transfer belt 2. The surface moves in the same direction as the transfer belt 2. Although depending on the bias characteristics of the primary transfer device, the secondary transfer roller 9D may be provided with a charging characteristic to electrostatically attract the recording paper. The secondary transfer device 9 transfers the superimposed toner image or the single color toner image on the intermediate transfer belt 2 to the recording sheet in the process of conveying the recording sheet by the secondary transfer belt 9C.

  The secondary transfer device 9 is fed with recording paper from the paper feed unit 1B. The paper feed unit 1B includes a plurality of paper feed cassettes 1B1 and a plurality of transport rollers 1B2 arranged in a transport path for recording paper fed from the paper feed cassette 1B1. Further, the wall surface of the image forming unit 1A is provided with a manual feed tray 1A1 that can be raised and lowered and a feeding roller 1A2.

  In the middle of the recording paper conveyance path from the paper feed cassette 1B1 to the registration roller 1B3, the recording paper conveyance path fed out from the manual feed tray 1A1 joins. The registration timing of the recording paper fed from any of the conveyance paths is set by a registration roller 1B3 located upstream of the secondary transfer unit in the paper conveyance direction.

  In the writing device 5, writing light is controlled by image information obtained by scanning a document on the document table 1C1 in the document reading unit 1C or image information output from a computer. An electrostatic latent image is formed on the photoreceptor 3 (Y, C, M, B) according to image information.

  The document reading unit 1C is provided with a scanner 1C2 that exposes and scans the document on the document table 1C1, and an automatic document feeder 1C3 is disposed on the upper surface of the document table 1C1. The automatic document feeder 1C3 has a configuration capable of reversing the document fed on the document table 1C1, and can perform scanning on both sides of the document.

  The electrostatic latent image formed on the photoreceptor 3 (Y, C, M, B) by the writing device 5 is developed by the developing device 6 (in FIG. 1, for convenience, indicated by reference numeral 6B). The developed image is primarily transferred to the intermediate transfer belt 2. When the toner images for each color are superimposed and transferred onto the intermediate transfer belt 2, the secondary transfer device 9 performs secondary transfer on the recording paper at once.

  The unfixed image carried on the surface of the recording paper that has been secondarily transferred is fixed by the fixing device 11. The fixing device 11 has a belt fixing structure including a fixing belt heated by a heating roller, and a pressure roller facing and abutting the fixing belt. By providing a contact area between the fixing belt and the pressure roller, that is, a nip area, a heating area for the recording paper can be expanded as compared with the fixing structure of another roller type. The recording paper that has passed through the fixing device 11 is switched in its transport direction by a transport path switching claw 12 disposed behind the fixing device 11, and is discharged again from the paper discharge tray 13 or the registration roller 1 </ b> B <b> 3 again. It is sent toward.

  In the copying machine 1 shown in FIG. 1, a primary transfer device as a transfer means uses a primary transfer roller 7 (Y, C, M, B) to which a positive polarity transfer bias is applied. The primary transfer roller 7 (Y, C, M, B) is pressed by a predetermined pressure against the photoreceptor 3 via the intermediate transfer belt 2 by a bearing and an elastic body such as a compression spring. Further, the primary transfer roller 7 (Y, C, M, B) has an intermediate transfer belt of about 1 to 2 [mm] with respect to a position opposed to the center position of the photoreceptor 3 (Y, C, M, B). It rotates in conjunction with the intermediate transfer belt 2 at a position offset downstream in the surface movement direction. This is to prevent pre-transfer that starts transfer by a transfer bias before the normal transfer position and generates an abnormal image such as an image flow.

The primary transfer roller 7 (Y, C, M, B) is configured in such a form that a rubber material having a medium resistance electric characteristic is wound around a metal core. In the embodiment, it is made of a foamed rubber having a medium resistance, and its volume resistivity is in the range of 10 ⁶ to 10 ¹⁰ [Ω · cm], preferably 10 ⁷ to 10 ⁹ [Ω · cm]. The material is not limited to foam rubber, and medium resistance solid rubber can be used as well.

  A primary transfer voltage having a positive polarity is applied to the primary transfer roller 7 (Y, C, M, B) by a constant current controlled power source, and the current set value (set value of the primary transfer current) is approximately 10. It is controlled in the range of ˜40 [μA]. In this way, by applying the primary transfer voltage to the primary transfer roller 7 (Y, C, M, B), the primary transfer between each photoreceptor 3 (Y, C, M, B) and the intermediate transfer belt 2 is performed. A primary transfer electric field is formed in the part. This primary transfer electric field is a primary transfer electric field in a direction in which the toner (negative polarity) on each photoconductor 3 (Y, C, M, B) is drawn toward the intermediate transfer belt 2 side.

  On the other hand, a secondary transfer voltage having a negative polarity is applied to the secondary transfer facing roller 2C by a constant current controlled power source. Thus, in the configuration in which the secondary transfer voltage is applied to the secondary transfer opposing roller 2C, the drive roller 9D is electrically grounded. By facing the drive roller 9D connected to the ground, a secondary transfer electric field is formed in the secondary transfer portion in the direction in which the toner (negative polarity) on the intermediate transfer belt 2 is pushed out to the recording paper side.

  The intermediate transfer belt 2 used in this embodiment is provided with an elastic layer of 100 to 500 [μm] on a 50 to 100 [μm] base layer, and further includes an elastic intermediate transfer constituted by a three-layer belt having a surface layer. It is a belt. Specific examples of the base layer include carbon dispersion in materials such as PI (polyimide), PAI (polyamideimide), PC (polycarbonate), ETFE (ethylene-tetrafluoroethylene), PVDF (polyvinylidene fluoride), and PPS (polyphenylene sulfide). Alternatively, there is one constituted by a medium resistance resin whose resistance is adjusted by blending an ionic conductive agent. Specific examples of the elastic layer include a rubber material such as urethane, NBR, CR, and the like, which includes a material whose resistance is adjusted by carbon dispersion or ionic conductive agent blending. As a specific example of the surface layer, the surface of the elastic layer is coated with a fluorine rubber or resin having a thickness of about 1 to 10 [μm] (or a hybrid material thereof). is there.

The intermediate transfer belt 2 has a volume resistivity in the range of 10 ⁶ to 10 ¹⁰ [Ω · cm], preferably 10 ⁸ to 10 ¹⁰ [Ω · cm]. The surface resistivity is in the range of 10 ⁶ to 10 ¹² [Ω / □], preferably 10 ⁸ to 10 ¹² [Ω / □]. Further, the Young's modulus (longitudinal elastic modulus) of the base layer is desirably 3000 [MPa] or more, and sufficient mechanical strength is required to withstand elongation, bending, wrinkle, and waviness due to driving. By using the elastic intermediate transfer belt 2 having such elasticity, the recording paper such as a paper having a low density of paper fibers or a recording paper such as a so-called embossed paper having an unevenness of 20 to 30 [μm] on the surface. The elastic layer follows the concave portion. For this reason, a solid filling improvement effect that the toner transfer property to the concave portion of the recording paper is improved is known.

  In this copying machine, the contact state between the photosensitive member 3 and the intermediate transfer belt 2 is different between a monochrome mode for forming a monochrome image and a color mode for forming a color image.

  Specifically, among the four primary transfer rollers 7 (Y, C, M, B) in the transfer unit, the black primary transfer roller 7B is a dedicated bracket separately from the other primary transfer rollers 7. I support it.

  The three primary transfer rollers 7 (Y, C, M) for Y, M, and C are supported by a common moving bracket. This moving bracket is moved in a direction approaching the photoreceptor 3 (Y, C, M) for Y, M, and C and a direction away from the photoreceptor 3 (Y, C, M) by driving the solenoid. It is possible.

  When the moving bracket is moved away from the photoreceptor 3 (Y, C, M), the stretching posture of the intermediate transfer belt 2 changes, and the intermediate transfer belt 2 has three photoreceptors for Y, C, and M. 3 (Y, C, M).

  Similarly, the B bracket allows the B photoconductor 3B and the intermediate transfer belt 2 to contact and separate. In the monochrome mode, the image forming operation is performed in a state where only the B photoconductor 3B is in contact with the intermediate transfer belt 2 in this manner. All colors are separated when the machine is stopped.

  When the moving bracket described above is moved in a direction approaching the three photoconductors 3 (Y, C, M), the stretching posture of the intermediate transfer belt 2 changes, and the three photoconductors 3 (Y, C, The intermediate transfer belt 2 that has been separated from M) contacts these three photosensitive members 3 (Y, C, M).

  At this time, the B photoconductor 3B and the intermediate transfer belt 2 remain in contact with each other. In the color mode, the image forming operation is performed in a state where all of the four photoconductors 3 (Y, C, M, and B) are in contact with the intermediate transfer belt 2 as described above.

  In such a configuration, the moving bracket, the solenoid described above, and the like function as contact / separation means for contacting / separating the photoreceptor 3 and the intermediate transfer belt 2.

  For the photoreceptor 3 (Y, C, M, B) after the Y, C, M, B toner images are primarily transferred to the intermediate transfer belt 2, the transfer residual toner is cleaned by a drum cleaning device. Then, after neutralizing with a static elimination lamp, it charges uniformly with a charging device, and prepares for the next image formation.

  Further, the intermediate transfer belt 2 after the primary transfer onto the recording paper P is subjected to a cleaning process for residual toner by the intermediate transfer belt cleaning device 10.

  In the copying machine 1 of the present embodiment, image adjustment control is performed at a predetermined timing. In the image quality adjustment control, a toner pattern is created, and image density control and positional deviation control are performed based on the result of detecting the image density and image forming position of the toner pattern. In the image density control, for example, a toner adhesion amount (image density) of a density control pattern (tone pattern) obtained by developing a predetermined pattern latent image is detected. Then, in accordance with the detection result of the toner adhesion amount, set values such as the toner concentration in the developer in the developing device, the writing conditions (exposure power, etc.) of the writing device 5, the charging bias and the developing bias are changed. In the positional deviation control, for example, the latent image writing timing of each color toner image is adjusted by the detection timing of the positional deviation control pattern (chevron patch).

  Such toner pattern detection locations for the density control pattern are, for example, on the photoreceptor 3 from the development area to the primary transfer portion, or on the intermediate transfer belt 2 after the primary transfer. Can be mentioned. However, when the diameter of the photoconductor 3 is small, it is difficult to detect the image density detection sensor on the photoconductor 3 due to the installation space of the image density detection sensor, and therefore, on the intermediate transfer belt 2 or the secondary transfer belt 9C. It is preferable to detect by. On the other hand, regarding the misregistration control pattern, it is necessary to observe the misregistration between the color toner images due to the variation in the distance between the photoconductors or the misregistration due to the writing timing of each color latent image. For this reason, detection on the surface moving body carrying the toner image after the intermediate transfer belt 2 is essential. In the embodiment, both the density control pattern and the positional deviation control pattern are detected on the secondary transfer belt 9C.

  Conventionally, many medium- and low-speed image forming apparatuses have a secondary transfer member that forms a secondary transfer electric field between the secondary transfer counter roller 2C and the intermediate transfer belt 2 at the secondary transfer unit. In general, a roller-shaped member having a small diameter is used instead of a belt-shaped member. In the configuration used for such a roller-shaped member secondary transfer member, it is difficult to detect the image quality adjustment pattern on the surface of the secondary transfer member. On the other hand, in the present embodiment, as shown in FIG. 1, since the secondary transfer belt 9C is provided as the secondary transfer member, it is possible to detect the image quality adjustment pattern on the surface of the secondary transfer member.

  Further, the secondary transfer member is not limited to a belt shape, and may be configured to use a roller having a large diameter. However, in the roller shape, since the detection position of the optical sensor unit 300 is curved, it is necessary to increase the diameter of the roller, which is disadvantageous in terms of space saving. On the other hand, by using a belt shape like the secondary transfer belt 9C, the degree of freedom can be improved by the layout configuration. In addition, since the belt-like shape is relatively easy to have a configuration in which the detection position of the optical sensor 300 is a flat surface, detection accuracy can be improved.

  As a restriction of the intermediate transfer belt 2, there is surface followability at the secondary transfer portion with respect to the surface of the recording medium having different surface properties in order to form an image on recording media such as various recording papers. As surface followability, in recent years, images are often formed on various recording media using full-color electrophotography. And as a recording medium, not only ordinary smooth recording paper but also a high slip smoothness such as coated paper, rough surface properties such as recycled paper, embossed paper, Japanese paper and kraft paper Things are increasingly being used. The followability of the surface of the intermediate transfer belt 2 at the secondary transfer portion for various recording media having different surface properties is important. If this followability is poor, the toner image transferred onto the recording medium has uneven density and color tone.

  Examples of the intermediate transfer belt 2 having such followability to various recording media include the elastic intermediate transfer belt described in Patent Document 2. FIG. 2 is an enlarged cross-sectional view showing a layer configuration of the intermediate transfer belt 2 having the same configuration as the intermediate transfer belt described in Patent Document 2. In the intermediate transfer belt 2 shown in FIG. 2, a flexible elastic layer 212 is laminated on a rigid base layer 211 that can be relatively flexible, and fine particles are laminated on the outermost surface as a surface layer 213.

  First, the base layer 211 will be described. Examples of the constituent material of the base layer 211 include a resin material containing a filler (or additive) for adjusting electric resistance, a so-called electric resistance adjusting material. As a resin material used for the base layer 211, from the viewpoint of flame retardancy, for example, a fluorine-based resin such as PVDF or ETFE, a polyimide resin, or a polyamide-imide resin is preferable. From the viewpoint of mechanical strength (high elasticity) and heat resistance. In particular, a polyimide resin or a polyamideimide resin is suitable. Examples of the electric resistance adjusting material contained in the resin material of the base layer 211 include metal oxide, carbon black, an ionic conductive agent, and a conductive polymer material.

  Next, the elastic layer 212 laminated on the base layer 211 will be described. A rubber elastic layer can be used as the elastic layer 212, and an acrylic rubber can be used as a specific example. As this acrylic rubber, what is marketed now can be used, and it is not specifically limited. However, among the various crosslinking systems (epoxy groups, active chlorine groups, carboxyl groups) of acrylic rubber, the carboxyl group crosslinking system is excellent in rubber properties (especially compression set) and processability, so select the carboxyl group crosslinking system. It is preferable to do.

  Next, the surface layer 213 made of spherical resin fine particles formed on the elastic layer 212 will be described. The material of the fine particles used for the spherical resin fine particles is not particularly limited, but the spherical resin fine particles mainly composed of resins such as acrylic resin, melamine resin, polyamide resin, polyester resin, silicone resin, fluororesin (hereinafter simply referred to as “fine resin fine particles”). Also referred to as “resin fine particles”. Further, the surface of fine particles made of these resin materials may be subjected to a surface treatment with a different material.

  Further, the resin fine particles referred to herein include a rubber material. A structure in which the surface of spherical resin fine particles made of a rubber material is coated with a hard resin is also applicable. The shape of the resin fine particles may be hollow or porous. Of the above-described materials, silicone resin fine particles are most preferable as a resin having a high function capable of imparting releasability and abrasion resistance to toner.

  The resin fine particles to be used are preferably fine particles produced in a spherical shape by a polymerization method or the like, and those closer to a true sphere are more preferable. The particle size is preferably monodispersed with a volume average particle size of 0.5 [μm] to 5 [μm] and a sharp distribution. When the average particle size is less than 0.5 [μm], the aggregation between the fine particles is remarkable, and thus it is difficult to uniformly apply to the surface of the acrylic rubber elastic layer. On the other hand, if the average particle diameter exceeds 5 [μm], the unevenness of the belt surface after application of the fine particles becomes large, and when used as the intermediate transfer belt 2, cleaning failure occurs during cleaning with the intermediate transfer belt cleaning device 10. .

The elastic layer 212 has a Martens hardness of 0.2 [N / mm ² ] to 0.8 [N / mm ² ] when pressed into 10 [μm], and the surface layer 213 provided on the surface of the elastic layer 212 However, they are arranged in the plane direction with independent spherical resin particles and are formed in a uniform uneven shape. In such an intermediate transfer belt 2, good followability to the surface of various recording media in the secondary transfer portion can be obtained while ensuring the releasability with respect to the toner by the surface layer 213. Moreover, as the elastic layer 212, good flame retardancy can be obtained while obtaining good followability by using a flame retardant acrylic rubber elastic layer showing VTM-0 in the UL94VTM combustion test. Specific examples of the base layer 211, the elastic layer 212, and the surface layer 213 of the intermediate transfer belt 2 can be those described in Patent Document 2, but are not limited thereto.

  In the case of the intermediate transfer belt 2 having the elastic layer 212 as shown in FIG. 2, the surface follows rough uneven paper having a rough surface property, thereby suppressing the occurrence of uneven density and uneven color tone on various recording media. Good image formation can be performed. However, the rubber material forming the elastic layer 212 generally has a poor releasability with respect to the toner, and the secondary transfer rate and the cleaning properties are poor unless a surface layer made of another material having a good releasability with respect to the toner is provided. It is difficult to make it practical.

  As an intermediate transfer belt having a conventional elastic layer, there is one in which a coating layer is provided on the surface of the elastic layer. Specifically, a belt having a coating layer provided on the surface of the elastic layer can be prepared by applying a liquid as a material for the coating layer to the surface of the elastic layer and drying the coating. However, the material used for the coating layer cannot be deformed following the deformation that the rubber material used for the elastic layer expands and contracts over time. Cracks occur. When cracks occur, the transferability and cleaning properties of the toner attached to the cracked portion deteriorate.

  On the other hand, in the intermediate transfer belt 2 shown in FIG. 2, the surface layer 213 has a structure in which resin fine particles are spread on the surface of the elastic layer 212. For this reason, when the surface of the elastic layer 212 is deformed so as to extend, the adjacent resin fine particles are displaced so as to open, and when the surface of the elastic layer 212 is deformed so as to contract, the space between the adjacent resin fine particles is Displace to clog. Even if the rubber material used for the elastic layer 212 is deformed, only the positional relationship between the resin fine particles is displaced, and cracks and the like do not occur. For this reason, it is possible to maintain the releasability with respect to the toner stable over time, and to improve the transferability and cleaning properties of the toner.

  Next, the toner pattern transferred to the secondary transfer belt 9C will be described in detail. FIG. 3 is an enlarged schematic configuration diagram in the vicinity of the secondary transfer belt 9C showing the gradation pattern and the optical sensor. As shown in FIG. 3, the optical sensor unit 300 includes a Y optical sensor 300Y, a C optical sensor 300C, an M optical sensor 300M, and a B optical sensor 300B arranged in the width direction of the secondary transfer belt 9C.

  Each of these sensors is a reflection type photosensor, and the light emitted from the light emitting element is reflected by the toner image on the front surface of the secondary transfer belt 9C or the belt, and the amount of reflected light is detected by the light receiving element. The control unit 200 (see FIG. 1) detects the toner image on the secondary transfer belt 9C based on the output voltage values from these sensors, and detects the image density (toner adhesion amount per unit area). Can be.

  In this printer, image density control for optimizing the image density of each color is executed when the power is turned on or every time a predetermined number of prints are performed. In the image density control, first, as shown in FIG. 3, the gradation patterns Sb, Sm, Sc, and Sy of the respective colors as the density control patterns are converted into the optical sensors 300 (Y, C, M) on the secondary transfer belt 9C. , B) is automatically formed at a position facing. The gradation pattern of each color is composed of 10 toner patches having an area of 2 [cm] × 2 [cm] having different image densities.

  The charging potential of the photoreceptor 3 (Y, C, M, B) when creating the gradation patterns Sb, Sm, Sc, Sy of each color is different from the uniform drum charging potential in the printing process, and the value is Increase gradually. Then, while forming a plurality of patch electrostatic latent images for forming a gradation pattern image on the photoconductor 3 (Y, C, M, B) by scanning with a laser beam, they are Y, C, M, Development is performed by a developing device for B. During this development, the value of the developing bias applied to the developing roller is gradually increased.

By such development, gradation pattern images of Y, C, M, and B are formed on the photoreceptor 3 (Y, C, M, and B). These are primarily transferred so as to be arranged at a predetermined interval in the main scanning direction of the secondary transfer belt 9C. At this time, the toner adhesion amount of the toner patch in the gradation pattern of each color is about 0.1 [mg / cm ² ] at the minimum and 0.55 [mg / cm ² ] at the maximum, and the toner Q / d distribution When measured, it is almost aligned with the regular charging polarity. The normal charging polarity here refers to the charging polarity of the toner in the developer in the developing device. Although it is negative in the present embodiment, it may be positive depending on the image forming apparatus.

  Each toner pattern (Sb, Sm, Sc, Sy) formed on the secondary transfer belt 9C passes through a position facing the optical sensor unit 300 as the secondary transfer belt 9C moves endlessly. At this time, each color optical sensor 300 (Y, C, M, B) receives an amount of light corresponding to the toner adhesion amount per unit area with respect to the toner patch of each gradation pattern.

  Next, the adhesion amount of each color toner pattern in each toner patch is calculated from the output voltage of the optical sensor 300 (Y, C, M, B) when each color toner patch is detected and the adhesion amount conversion algorithm. Image forming conditions are adjusted based on the calculated adhesion amount.

  Specifically, a function (y = ax + b) indicating a straight line graph is calculated by regression analysis based on the result of detecting the toner adhesion amount on the toner patch and the development potential when each toner patch is imaged. Then, an appropriate development bias value is calculated by substituting the target value of the image density into this function, and the development bias values for Y, C, M, and B are specified.

  The memory stores an image forming condition data table in which several tens of development bias values and appropriate drum charging potentials individually corresponding to the values are associated in advance. For each of the image forming units 66Y, 66C, 66M, and B, a developing bias value closest to the specified developing bias value is selected from the image forming condition table, and the drum charging potential associated therewith is specified.

  The copier 1 also performs color misregistration correction processing when the power is turned on or whenever a predetermined number of prints are performed. In this color misregistration amount correction process, Y, C, and so-called chevron patches PV as misregistration control patterns as shown in FIG. 4 are respectively provided at one end and the other end in the width direction of the secondary transfer belt 9C. A color misregistration detection image composed of M and B color toner images is formed.

As shown in FIG. 4, the chevron patch PV has a predetermined pitch in the belt moving direction, which is the sub-scanning direction, with the toner images of each color of Y, C, M, and B inclined by about 45 [°] from the main scanning direction. Is a line pattern group arranged in. The amount of the chevron patch PV attached is about 0.3 [mg / cm ² ].

  Then, by detecting each color toner image in the chevron patch PV, the position in the main scanning direction (photoconductor axial direction), the position in the sub-scanning direction (belt moving direction), the magnification error in the main scanning direction in each color toner image, Each skew from the main scanning direction is detected. The main scanning direction here refers to the direction in which the laser light is phased on the surface of the photosensitive member as it is reflected by the polygon mirror.

  For such Y, C, M toner images in the chevron patch PV, the optical sensor 300 reads the detection time difference from the B toner image. In the drawing, the vertical direction of the paper surface corresponds to the main scanning direction, and after the Y, C, M, and B toner images are arranged in order from the left, the postures are different from those of B, M, and C by 90 [°]. , Y toner images are further arranged.

  Based on the difference between the actual measurement value and the theoretical value for the detection time differences tyk, tmk, and tck with respect to K as the reference color, the shift amount in the sub-scanning direction of each color toner image, that is, the resist shift amount is obtained. Then, on the basis of the registration deviation amount, the optical writing start timing with respect to the photosensitive member 3 is corrected every other polygon mirror surface of the writing device 5, that is, one scanning line pitch as one unit. Reduce the deviation. Further, the inclination (skew) of each color toner image from the main scanning direction is obtained based on the difference in the amount of deviation in the sub-scanning direction between both ends of the belt. Then, based on the result, surface tilt correction of the optical system reflection mirror is performed, and skew deviation of each color toner image is reduced.

  As described above, the color misregistration correction process is a process for correcting the optical writing start timing and the surface tilt based on the timing of detecting each toner image in the chevron patch PV to reduce the registration error and the skew error. By such a color misregistration correction process, it is possible to suppress the occurrence of color misregistration of an image due to a shift in the formation position of each color toner image with respect to the secondary transfer belt 9C over time due to a temperature change or the like.

  Further, if the image forming operation with a low image area continues, the amount of old toner that stays in the developing device for a long time increases, so that the toner charging characteristics deteriorate and the image quality deteriorates when used for image formation (development capability decreases, Transferability decline). In order to prevent such old toner from staying in the developing device, the toner is discharged to a non-image area of the photosensitive member 3 at a certain timing, and new toner is replenished to the developing device whose toner density is lowered after the discharging to refresh the developing device. It has a refresh mode.

  The control unit 200 stores the toner consumption amount of each developing device and the operation time of each developing device, and the toner consumption amount is equal to or less than a threshold with respect to the operation time of the developing device at a predetermined timing. Each developing device is checked to see if it is. Then, the refresh mode is executed for the developing device below the threshold. When the refresh mode is executed, a toner consumption pattern as a toner pattern is created in a non-image forming area corresponding to the space between the sheets of the photoreceptor 3 and transferred to the secondary transfer belt 9C (see FIG. 5). In this embodiment, the size of the toner consumption pattern is set to 330 [mm] in the main scanning direction.

  The adhesion amount of the toner consumption pattern is determined based on the toner consumption amount with respect to the operation time of the developing device for a predetermined period.

Further, the toner consumption pattern of each color is formed on the secondary transfer belt 9C by superimposing two colors in the order of size, Y → C or M → B as shown below.
-Maximum sub-scanning direction length of each color: 15 [mm]
-Maximum length of each color in the main scanning direction: 330 [mm]

  The length of the toner consumption pattern in the sub-scanning direction is determined from the image forming history in the normal image forming operation. Therefore, the length of the Y, C, M, and B toner patterns in the sub-scanning direction is not always a constant length such as 15 [mm], but the length of the toner pattern in the sub-scanning direction independently for each color. The height is variable, for example, from 0 to 15 [mm].

  In recent years, it has become difficult to ensure the cleanability of the intermediate transfer belt cleaning device 10 in a combination of a small particle size polymerized toner and an elastic intermediate transfer belt that are used to improve image quality. Conventionally, each color gradation pattern, chevron patch, and toner consumption pattern formed on the intermediate transfer belt 2 are collected by the intermediate transfer belt cleaning device 10. At this time, the intermediate transfer belt cleaning device 10 must remove a large amount of toner of an untransferred toner image such as each color gradation pattern, chevron patch, and toner consumption pattern from the intermediate transfer belt 2.

  However, in the configuration in which the small particle size polymerized toner and the elastic intermediate transfer belt are combined, the cleaning device including the polarity control unit and the brush roller or the two brush rollers for removing the positive and negative toners is not used. The transferred toner image could not be removed at once. In such a case, the toner on the intermediate transfer belt 2 that could not be cleaned may be transferred onto the recording paper during the next printing operation, resulting in an abnormal image.

  Therefore, in this copying machine 1, toner patterns such as each color gradation pattern, chevron patch, and toner consumption pattern are transferred to the secondary transfer belt 9C and removed by the secondary transfer belt cleaning device 90. As a result, only the secondary transfer residual toner is input to the intermediate transfer belt cleaning device 10, and the amount of toner input to the intermediate transfer belt cleaning device 10 can be reduced. Thereby, it is possible to suppress the occurrence of poor cleaning in the intermediate transfer belt cleaning device 10 and it is possible to suppress the occurrence of abnormal images. On the other hand, since the secondary transfer belt 9C is a belt without an elastic layer, it is easy to ensure cleaning properties. Accordingly, the toner pattern such as the toner consumption pattern transferred to the secondary transfer belt 9C can be satisfactorily removed by the secondary transfer belt cleaning device 90.

  Further, in the conventional configuration in which the toner consumption pattern is removed by the intermediate transfer belt cleaning device 10, the toner consumption pattern is created with a halftone image in consideration of the load of the intermediate transfer belt cleaning device 10. However, in this embodiment, the toner consumption pattern is a solid image. This is because the transfer rate of the halftone image from the intermediate transfer belt 2 to the secondary transfer belt 9C is lower than that of the solid image. By making the toner consumption pattern a solid image, the amount of residual toner transferred to the intermediate transfer belt cleaning device 10 can be reduced. Thus, even in the configuration of the present embodiment in which the small particle size polymerized toner and the elastic intermediate transfer belt, which are difficult to ensure the cleaning property, are used, the toner on the intermediate transfer belt 2 can be satisfactorily removed by the intermediate transfer belt cleaning device 10. Can do.

  Also, a secondary transfer bias for secondary transfer of a toner pattern such as a gradation pattern, a chevron patch, a toner consumption pattern to the secondary transfer belt 9C, and a secondary transfer for secondary transfer of a toner image to a recording sheet. It is preferable to set the bias individually. This is because the secondary transfer bias provides a good transfer rate when the toner pattern is secondarily transferred to the secondary transfer belt 9C, and the transfer rate becomes good when the toner image is secondarily transferred to the recording paper. This is because the secondary transfer bias is different from each other. Therefore, the secondary transfer bias when the toner pattern is secondarily transferred to the secondary transfer belt 9C is set to a secondary transfer bias that provides a good transfer rate when the toner image is secondarily transferred to the recording paper. As a result, the transfer rate deteriorates and the amount of toner input to the intermediate transfer belt cleaning device 10 increases. As a result, there is a risk of poor cleaning.

  On the other hand, the secondary transfer bias when the toner pattern is secondarily transferred to the secondary transfer belt 9C and the secondary transfer bias when the toner image is secondarily transferred to the recording paper are individually set. As a result, when the toner pattern is secondarily transferred to the secondary transfer belt 9C and when the toner image is secondarily transferred to the recording paper, the secondary transfer residual toner input to the intermediate transfer belt cleaning device 10 is removed. Can be reduced. Thereby, it is possible to suppress the occurrence of cleaning failure in the intermediate transfer belt cleaning device 10.

  Next, the intermediate transfer belt cleaning device 10 of this embodiment will be described. FIG. 6 is an enlarged configuration diagram showing the intermediate transfer belt cleaning device 10 of the copying machine 1 and its surroundings in an enlarged manner. In the figure, the intermediate transfer belt cleaning device 10 includes a first cleaning unit 100a and a second cleaning unit 100b adjacent to the first cleaning unit 100a on the downstream side in the belt moving direction. The post cleaning unit 100c is also adjacent to the second cleaning unit 100b on the downstream side in the belt movement direction.

  In the first casing 120a of the first cleaning unit 100a, a first cleaning brush roller 101 serving as a cleaning member that removes transfer residual toner from the surface of the intermediate transfer belt 2 is disposed. Further, the first collection roller 102 which is a collection member that rotates while contacting the first cleaning brush roller 101 to collect the transfer residual toner from the brush roller, and the first transfer roller scrapes the transfer residual toner from the surface of the first collection roller 102 A scraping blade 103 and the like are also provided. The first casing 120a is also provided with a first conveying screw 110a that discharges the transfer residual toner scraped off from the first recovery roller 102 to the outside of the first casing 120a. Further, the first casing 120a is provided with an inlet seal 111a and an outlet seal 112a that are in contact with the intermediate transfer belt 2 and prevent the toner in the first casing from scattering outside the first casing. Yes. These brush roller, recovery roller, and conveying screw are driven by an intermediate transfer belt cleaning motor 113 in the copying machine main body outside the intermediate transfer belt cleaning device 10. The rotation of the intermediate transfer belt cleaning motor 113 is transmitted to the intermediate transfer belt cleaning device 10 by a gear or the like. The cleaning body driving means is the intermediate transfer belt cleaning motor 113 and its driving system. The control unit 200 performs control so that the rotation speed of the motor is constant. The intermediate transfer belt cleaning motor 113 is a DC brushless motor. Speed control is performed by adjusting a motor applied voltage by looking at a difference between a Hall element signal and a reference clock by PLL (phase locked loop) control.

  Most of the secondary transfer residual toner that has not been completely transferred by the secondary transfer belt 9C (about 80% of the transfer residual toner) is reversely charged toner that is charged with a polarity opposite to the normal charge polarity (negative polarity). Therefore, in the present embodiment, a voltage having a normal charging polarity (negative polarity) is applied to the first cleaning brush roller 101 to electrostatically remove the positive polarity toner on the intermediate transfer belt 2. In addition, a negative voltage greater than that of the first cleaning brush roller 101 is applied to the first recovery roller 102. In the intermediate transfer belt cleaning device 10, a voltage applied to the first cleaning brush roller 101 is set so that most of the secondary transfer residual toner image is removed by the first cleaning brush roller 101. However, at this time, there is a toner in which the toner receives a negative charge from the first cleaning brush roller 101 and becomes normal polarity (negative polarity).

  Similar to the first cleaning unit 100a, a second cleaning brush roller 104, a second recovery roller 105, and a second scraping blade 106, which are cleaning members, are disposed in the second casing 120b of the second cleaning unit 100b. . Further, a second transport screw 110b, an inlet seal 111b, and an outlet seal 112b are also disposed in the second casing 120b.

  The second cleaning unit 100b receives the secondary transfer residual toner charged to the normal charging polarity (negative polarity) that cannot be removed by the first cleaning unit 100a and the negative charge from the first cleaning brush roller 101, and receives the normal polarity (negative polarity). ) Is removed. Therefore, a voltage having a polarity (positive polarity) opposite to the normal charging polarity of the toner is applied to the second cleaning brush roller 104 to electrostatically remove the negative polarity toner on the intermediate transfer belt 2. Further, a negative voltage greater than that of the second cleaning brush roller 104 is applied to the second recovery roller 105.

  The two cleaning brush rollers 101 and 104 include a metal rotary shaft member that is rotatably supported, and a brush portion that includes a plurality of raised brushes that are erected on the peripheral surface thereof. The diameter is φ15 to 16 [mm]. The raised nail has a two-layer core-sheath structure in which the inside is made of a conductive material such as conductive carbon and the surface portion is made of an insulating material such as polyester. As a result, the lead has substantially the same potential as the cleaning bias applied to the cleaning brush rollers 101 and 104, and the toner can be electrostatically attracted to the raised surface. As a result, the toner on the intermediate transfer belt 2 is captured by the raised brushes of the cleaning brush rollers (101, 104).

  The raised brushes of the cleaning brush rollers 101 and 104 may be composed of only conductive fibers instead of the two-layered core-sheath structure. Moreover, you may make it the so-called oblique hair planted in the attitude | position inclined with respect to the normal line direction of a rotating shaft member. Further, the raising of the second cleaning brush roller 104 to which a negative cleaning bias is applied may have a core-sheath structure, and the raising of the first cleaning brush roller 101 may be composed of only conductive fibers. By forming the raised portions of the first cleaning brush roller 101 to which the negative cleaning bias is applied only with conductive fibers, it is possible to easily generate charge injection from the first cleaning brush roller 101 to the toner. Therefore, the first cleaning brush roller 101 can satisfactorily align the toner on the intermediate transfer belt 2 with negative polarity. On the other hand, the brushing of the second cleaning brush roller 104 has a core-sheath structure, so that charge injection into the toner can be suppressed, and the toner on the intermediate transfer belt 2 is suppressed from being positively charged. As a result, the second cleaning brush roller 104 can suppress the generation of toner that cannot be removed electrostatically.

  Further, the two cleaning brush rollers 101 and 104 are bited into the intermediate transfer belt 2 by a biting amount of 1 [mm]. Then, the brush roller is rotationally driven by the driving means so as to move the raising at the contact position in a direction (counter direction) opposite to the moving direction of the intermediate transfer belt 2. By rotating the raised hair so as to move in the counter direction at the contact position, the linear velocity difference between the cleaning brush roller and the intermediate transfer belt 2 can be increased. As a result, the probability of contact with the raised hair before a portion of the intermediate transfer belt 2 passes through the contact range with the cleaning brush roller increases, and the toner can be removed from the intermediate transfer belt 2 satisfactorily.

  The cleaning brush rollers 101 and 104 are disposed to face the cleaning facing rollers 13 and 14 with the intermediate transfer belt 2 interposed therebetween. The cleaning counter rollers 13 and 14 are also conductive and are grounded to form a cleaning electric field between the cleaning brush rollers 101 and 104, respectively.

  As the two collection rollers 102 and 105, both are made of SUS (stainless steel) rollers. The collection rollers 102 and 105 may be made of any material as long as the following functions can be exhibited. That is, this function is to transfer the toner adhering to the cleaning brush rollers 101 and 104 from the cleaning brush roller to the collecting roller by the potential gradient between the raised brush and the collecting roller. For example, as a collection roller, a conductive cored bar is covered with a high resistance elastic tube of several [μm] to 100 [μm] or is coated with an insulating coating so that the roller resistance is logR = 12 to 14 [Ω · cm]. You may use what you did. By using a SUS roller as the collection roller, there is an advantage that the cost can be reduced, the applied voltage can be kept low, and the power can be saved. On the other hand, by setting the roller resistance to logR = 12 to 14 [Ω · cm], charge injection into the toner during collection to the collection roller is suppressed, and the toner has the same polarity as the applied voltage of the collection roller. In addition, it is possible to suppress a decrease in the toner recovery rate.

  In FIG. 6, the secondary transfer residual toner on the intermediate transfer belt 2 passes through the contact portion between the first inlet seal 111a and the belt as the intermediate transfer belt 2 moves, and the position of the first cleaning brush roller 101 is increased. It is transferred to. A cleaning bias having a normal charging polarity (negative polarity) of toner is applied to the first cleaning brush roller 101. The positively charged toner on the intermediate transfer belt 2 is electrostatically applied to the brush of the first cleaning brush roller 101 by the electric field formed by the potential difference between the intermediate transfer belt 2 and the surface potential of the first cleaning brush roller 101. Adsorb. At this time, a negative charge is received from the brush by charge injection or discharge, and a part of the toner is charged with normal polarity (negative polarity) and remains on the belt.

  The positive toner transferred to the first cleaning brush roller 101 is transferred to a contact position with the first recovery roller 102 to which a negative recovery bias having a larger absolute value than the first cleaning brush roller 101 is applied. . Then, due to the electric field formed by the potential difference between the surface potential of the first cleaning brush roller 101 and the surface potential of the first recovery roller 102, the transfer residual toner in the brush of the first cleaning brush roller 101 is transferred onto the first recovery roller 102. Is electrostatically transferred to. Then, after being scraped off from the surface of the first recovery roller 102 by the first scraping blade 103, the first cleaning screw 100a transports the toner from the first cleaning unit 100a to the toner reservoir.

  The secondary transfer residual toner on the intermediate transfer belt 2 that could not be removed by the first cleaning brush roller 101 is transferred to a contact position with the second cleaning brush roller 104. A voltage having a polarity (positive polarity) opposite to the normal charging polarity of the toner is applied to the second cleaning brush roller 104. The negatively charged toner on the intermediate transfer belt 2 is electrostatically adsorbed by the electric field formed by the potential difference between the intermediate transfer belt 2 and the surface potential of the second cleaning brush roller 104, and the second cleaning brush roller Move to 104. Thereafter, after electrostatic transfer to the second recovery roller 105, the second scraping blade 106 scrapes off the second recovery roller 105, and then from the second cleaning unit 100 b to the toner storage unit by the second transport screw 110 b. It is conveyed to.

  In the present embodiment, most of the secondary transfer residual toner can be cleaned by the first cleaning unit 100a and the second cleaning unit 100b. However, in the case of the intermediate transfer belt cleaning apparatus including only the first cleaning unit 100a for removing the positive polarity toner and the second cleaning unit 100b for removing the negative polarity toner, a stain-like abnormal image that seems to be a poor cleaning sometimes occurs. there were. In particular, among the plurality of image forming units 66, a noticeable spot-like abnormal image occurred in the Y color solid image formed by the Y color image forming unit 66 arranged at the most upstream in the moving direction of the intermediate transfer belt 2.

  As a result of earnest research on the above-described spot-like abnormal image, the present applicants sometimes found that the toner (hereinafter referred to as “reattached toner”) reattached to the intermediate transfer belt 2 from each cleaning brush roller (101, 104). It was found that it appeared as a spot-like abnormal image.

  Therefore, in the intermediate transfer belt cleaning device 10 of the present embodiment, the post cleaning unit 100c for removing the reattached toner that has reattached to the intermediate transfer belt 2 on the downstream side of the second cleaning unit 100b in the moving direction of the intermediate transfer belt. Was established.

  The post cleaning unit 100 c has a post cleaning roller 107 made of a conductive sponge that removes the reattached toner on the intermediate transfer belt 2. Further, the post cleaning roller 108 is a recovery member that rotates while contacting the post cleaning roller 107 and recovers toner from the post cleaning roller 107. Further, a post scraping blade 109 for scraping off transfer residual toner from the surface of the post recovery roller 108 is also provided. The post cleaning roller 107, the post collection roller 108, and the post scraping blade 109 are disposed in the post casing 120c. In the post casing 120c, a post transport screw 110c and the like for discharging the toner scraped off from the post collection roller 108 to the outside of the post casing 120c are also provided. Further, the post casing 120c is provided with an inlet seal 111c and an outlet seal 112c that are in contact with the intermediate transfer belt 2 and prevent the toner in the post casing from scattering outside the post casing.

  A positive voltage much larger than the absolute value of the voltage applied to each of the cleaning brush rollers 101 and 104 is applied to the post cleaning roller 107. A positive voltage greater than that of the post cleaning roller 107 is applied to the post collection roller 108. Further, the post cleaning roller 107 is disposed to face the cleaning facing roller 15 with the intermediate transfer belt 2 interposed therebetween. The cleaning counter roller 15 is conductive, and is grounded to form a cleaning electric field with the post cleaning brush roller 107.

  FIG. 7 is a graph showing the relationship between the voltage applied to the post-cleaning roller 107 and the number of spot-like images generated. The number of occurrences on the vertical axis in FIG. 7 indicates that all 50 solid images of M, C, and B are continuously output, then 50 Y solid images are output, and the output Y solid images are output. This is the number of sheets that have been visually confirmed and a stain-like abnormal image has been confirmed. As shown in FIG. 7, it can be seen that the number of occurrences of spot-like abnormal images decreases as the voltage applied to the post cleaning roller 107 is increased. In particular, when the post cleaning roller 107 is a conductive sponge roller and the applied voltage is increased, the number of occurrences of spot-like abnormal images can be reduced to zero. In the above description, the cleaning property and the toner re-adhesion property of the re-adhering toner of the post cleaning unit 100c are evaluated based on the number of the spot-like images generated, but there is no difference in the tendency among other evaluation methods.

  How much bias is sufficient depends on the intended user and system of the machine. It also depends on the environment. In the present embodiment, as shown in FIG. 8, in the low temperature and low humidity environment, the current setting value of the second cleaning brush roller 104 is 20 [μA], and the current setting value of the first cleaning brush roller 101 is −30 [μA. ]. At that time, with the current value 55 [μA] of the post-cleaning roller 107, the number of occurrences of spot-like abnormal images could be reduced to zero. At this time, the current value used by the post-cleaning roller 107 was | 55 | [μA] with respect to the absolute value | 30 | [μA] of the current value used by the brush. In this way, the number of occurrences of spot-like abnormal images could be reduced to 0 when the current value of the post cleaning roller 107 was 1.8 times or more the current value of the brush. Here, the current value is a current that flows from the cleaning brush roller or the post cleaning roller 107 to the intermediate transfer belt 2.

  Furthermore, in a normal temperature environment, the current setting value of the second cleaning brush roller 104 is 10 [μA], and the current setting value of the first cleaning brush roller 101 is −30 [μA]. At this time, by applying a current of 100 [μA] and 3.3 times or more to the absolute value of the current value used for the brush, the number of occurrences of a spot-like abnormal image could be reduced to zero.

  Further investigations were made, including in a high-humidity environment, and when an absolute value of 10 times or 30 times the absolute value of the current value of the brush was passed through the post cleaning roller 107, a spot-like abnormal image was generated. The number could be zero. Thus, the higher the humidity is, the higher the current value of the post cleaning roller 107 required to suppress the abnormal image due to the reattached toner.

  As described above, the absolute value of the current of the post cleaning roller 107 is set to at least twice the absolute value of the current of the cleaning brush rollers 101 and 104. Further, the current value of the post cleaning roller 107 is varied under each environment. Specifically, a temperature / humidity sensor is provided in the apparatus, and the current value of the post cleaning roller 107 is changed based on the detection result of the temperature / humidity sensor. The voltage value applied to the post cleaning roller 107 may be changed according to the environment.

  The post cleaning roller 107 includes a metal rotating shaft member that is rotatably supported and a conductive sponge roller portion that covers the peripheral surface of the rotating shaft member, and has an outer diameter of 15 to 16 mm. The post collection roller 108 has the same configuration as the first collection roller 101 and the second collection roller 104.

  Further, as shown in FIG. 7, in the case of the brush roller, the number of occurrences of spot-like abnormal images can be reduced by increasing the bias, but the number of occurrences cannot be reduced to zero. On the other hand, in the case of the conductive sponge roller, by increasing the bias, the number of occurrences of spot-like abnormal images could be reduced to zero. In the case of the brush roller, the toner adsorbed to the brush may move to the base of the brush, and thus the toner that has moved to the base of the brush is not collected by the collecting roller but remains on the brush. It is considered that the toner remaining on the brush reattaches to the intermediate transfer belt 2 at some point. Therefore, in the case of the brush roller, it is considered that the reattached toner that was removed by itself reattached to the intermediate transfer belt 2 again, and the spot-like image could not be reduced to zero.

  On the other hand, in the conductive sponge roller, the toner adsorbed on the sponge roller stays near the surface of the sponge roller. Therefore, it is considered that there is hardly any toner that is well collected by the collecting roller and that remains without being collected. As a result, no toner reattaches to the intermediate transfer belt 2 from the sponge roller, and no reattachment toner adheres to the intermediate transfer belt 2 that has passed through the intermediate transfer belt cleaning device 10, resulting in generation of a spot-like image. It is thought that it was made 0.

  In this embodiment, a sponge roller is used as the post cleaning roller 107, but a roller having a flat surface such as a rubber roller or a metal roller may be used. Even if the surface flat roller such as a rubber roller or a metal roller is used, the toner adheres only to the surface of the post cleaning roller 107. Therefore, the toner removed by the post cleaning roller 107 can be recovered satisfactorily by the post recovery roller 108, and the occurrence of toner that remains without being recovered by the post recovery roller 108 can be suppressed. As a result, the reattachment toner removed by the post cleaning roller 107 can be prevented from adhering to the intermediate transfer belt 2 again from the post cleaning roller, and the number of occurrences of spot-like abnormal images can be reduced to zero. .

  In this embodiment, the polarity of the voltage applied to the post cleaning roller 107 is positive. Thereby, the polarity of the voltage applied to the post cleaning roller 107 and the polarity of the voltage applied to the second cleaning brush roller 104 can be made the same polarity. as a result. The potential difference between the second cleaning brush roller 104 and the post cleaning roller 107 is smaller than when the polarity of the voltage applied to the second cleaning brush roller 104 and the polarity of the voltage applied to the post cleaning roller 107 are different from each other. can do. Therefore, voltage leakage between the second cleaning brush roller 104 and the post cleaning roller 107 can be suppressed. Further, by setting the polarity of the voltage applied to the post cleaning roller 107 to a positive polarity, it is possible to remove a slight amount of negative polarity toner that could not be removed by the second cleaning brush roller 104.

  In this embodiment, a positive voltage is applied to the post cleaning roller 107, but a negative voltage may be applied. 9, when a voltage of +1500 [V] is applied to the post cleaning roller 107, the occurrence of a spot-like image is 17 out of 14 sheets and 14 sheets, and the average is 15.5 sheets. It was. As indicated by the ▲ mark in FIG. 9, when a voltage of −1500 [V] was applied to the post cleaning roller 107, the occurrence of spot-like images was 22 out of 50 sheets and 10 sheets, which was an average of 16 sheets. . In this way, there was no significant difference in the average number of spot-like images generated when positive polarity bias was applied and when negative polarity was applied, and there was a tendency for the same cleaning property. Note that the number of occurrences on the vertical axis in FIG. 9 indicates that after 50 continuous images of M, C, and B colors are output continuously in a high temperature and high humidity environment, 50 Y solid images are output and output. This is the number of the Y-color solid images that were visually confirmed and spot-like abnormal images were confirmed. As described above, there is no difference in cleaning performance between the case where a negative voltage is applied to the post cleaning roller 107 and the case where a positive voltage is applied. Therefore, it is considered that the re-adhering toner can be satisfactorily removed by the post cleaning roller 107 by applying a large voltage regardless of the polarity of the applied voltage. Therefore, even if a large negative voltage is applied to the post cleaning roller 107, it is possible to suppress the presence of reattached toner on the intermediate transfer belt 2 that has passed through the intermediate transfer belt cleaning device 10.

  If the cleaning members of the first cleaning unit 100a and the second cleaning unit 100b are made of conductive sponge rollers, it is considered that the post-cleaning unit 100c can be eliminated without causing reattachment toner. However, if the cleaning members of the first cleaning unit 100a and the second cleaning unit 100b are conductive sponge rollers, the secondary transfer residual toner cannot be removed satisfactorily. This is because in the case of the conductive sponge roller, the cleaning nip between the intermediate transfer belt 2 and the cleaning member cannot be sufficiently obtained as compared with the brush roller. As a result, sufficient opportunity for electrostatic adsorption of the secondary transfer residual toner on the intermediate transfer belt 2 to the cleaning member cannot be obtained, and the secondary transfer residual toner cannot be removed satisfactorily. Therefore, by using the brush roller as the cleaning member of the first cleaning unit 100a and the second cleaning unit 100b, the secondary transfer residual toner can be removed satisfactorily. On the other hand, the re-adhering toner that re-adheres to the intermediate transfer belt 2 from the cleaning brush rollers 101 and 104 is scattered, and the amount of toner is smaller than that of the secondary transfer residual toner. Therefore, even if the cleaning sponge has a narrower cleaning nip than the brush roller, the reattached toner can be sufficiently removed.

  The average cell diameter of the post cleaning roller 107 made of a conductive sponge roller is preferably 150 [μm] or less. FIG. 10 shows Comparative Example 1 using a conductive sponge roller having a cell diameter of 386 [μm] to 795 [μm], and Examples 1-4 using a conductive sponge roller having an average cell diameter of 150 [μm] or less. This is data obtained by examining the number of occurrences of spot-like images. In Examples 1 to 4, the cell diameter is 99 to 134 [μm].

  The vertical axis in FIG. 10 shows a predetermined number of times (0 to 5 times) in which high-humidity / high-temperature environments (H / H environments) continuously output 50 solid images of M, C, and B colors, respectively. It was. Thereafter, 50 Y-color solid images are output, and the output Y-color solid images are visually confirmed, and the number of spots of abnormal stain images is confirmed. “Start” on the horizontal axis is a result of outputting 50 Y-color solid images and visually confirming the output Y-color solid images. In addition, “KCM solid × 1” performs an operation of outputting 50 solid images of M color, C color, and B color one by one, and then outputs and outputs 50 Y color solid images. It is the result of visually confirming the Y color solid image. In addition, “KCM Solid × 5” performs the operation of outputting 50 solid images of M, C, and B in succession 5 times each, and then outputs and outputs 50 Y solid images. It is the result of visually confirming the Y color solid image. In Examples 1 to 4, the diameter of the screening roller, Asker C hardness, the diameter of the collection roller, and the like are different.

  As shown in FIG. 10, in each of Examples 1 to 4 in which the cell diameter was 150 [μm] or less, the number of spots-like images generated could be suppressed to 6 or less. On the other hand, in Comparative Example 1 in which the cell diameter was 386 [μm] to 795 [μm], the number of spots-like images generated was 6 or more in any case. This is considered for the following two reasons. First, in Comparative Example 1 having a large cell diameter, the reattachment toner on the intermediate transfer belt 2 is not adsorbed by the post cleaning roller 107, and the reattachment toner removal performance is deteriorated. Further, as the cell diameter increases, the amount of toner that has moved into the sponge roller increases, and the amount of toner that remains on the sponge roller without being collected by the post collection roller 108 increases. As a result, the amount of toner that reattaches from the post cleaning roller 107 to the intermediate transfer belt 2 has increased. From these two factors, it is considered that the sponge roller having a large cell diameter could not sufficiently suppress the occurrence of a spot-like image that is an abnormal image due to the reattached toner.

  On the other hand, in Examples 1 to 4 in which the cell diameter is 150 [μm] or less, the reattached toner on the intermediate transfer belt 2 can be satisfactorily brought into contact with the post cleaning roller 107 and can be adsorbed favorably. Furthermore, it is possible to suppress the adsorbed toner from moving deep into the cell, and the post recovery roller 108 can recover the toner well. As a result, it was possible to satisfactorily suppress a spot-like image due to the reattached toner.

  The post cleaning roller 107 made of a sponge roller is preferably rotated (hereinafter referred to as forward rotation) so that the surface movement direction is the same as the intermediate transfer belt movement direction at the contact position with the intermediate transfer belt 2. . This is because the sponge roller has a larger rotational load than the brush roller. Therefore, like the cleaning brush rollers 101 and 104, the post cleaning roller 107 is rotated so that the surface movement direction is opposite to the intermediate transfer belt movement direction at the contact position with the intermediate transfer belt 2 (hereinafter referred to as reverse). When it is rotated), the following problems occur. That is, the intermediate transfer drive motor that drives the intermediate transfer belt 2 and the intermediate transfer belt cleaning motor 113 that drives the post-cleaning roller 107 need to use an expensive drive motor with a large rated torque, which increases the cost of the apparatus. It is a problem of being connected. In addition, there is no difference in cleaning performance even when the post-cleaning roller 107 is rotated forward or backward, and in any case, the reattached toner does not move to the image forming unit 66, and a spot-like image is formed. It never occurred. For this reason, it is preferable to rotate the post cleaning roller 107 forward.

  FIG. 11 is a graph showing the relationship between the linear velocity difference between the post cleaning roller 107 and the intermediate transfer belt 2 and the torque of the intermediate transfer belt drive motor 2BM that drives the intermediate transfer belt 2. FIG. 12 shows the relationship between the linear velocity difference between the post cleaning roller 107 and the intermediate transfer belt 2 and the torque of the intermediate transfer belt cleaning motor 113 that rotationally drives each collection roller and each cleaning roller of the intermediate transfer belt cleaning device 10. It is a graph to show. The linear velocity difference between FIGS. 11 and 12 is (linear velocity of the post cleaning roller / linear velocity of the intermediate transfer belt) × 100. Further, the post cleaning roller 107 is forwardly rotated with respect to the rotation direction of the intermediate transfer belt 2.

  As shown in FIG. 11, when the linear speed of the post cleaning roller 107 is slower than the linear speed of the intermediate transfer belt 2 by 1 [%], the intermediate transfer belt is driven in a normal temperature / humidity (MM) environment. It can be seen that the torque of the motor 2BM increases to near the rated torque. Also, as shown in FIG. 12, if the linear speed of the post cleaning roller 107 is faster than the linear speed of the intermediate transfer belt 2 by 1 [%], the intermediate transfer belt cleaning is performed in a low temperature and low humidity (LL) environment. It can be seen that the torque of the motor 113 rises to near the rated torque.

  As can be seen from FIGS. 11 and 12, it is preferable that the linear velocity of the post cleaning roller 107 is suppressed to ± 1 [%] or less with respect to the linear velocity difference of 100 [%]. By rotating the post cleaning roller 107 with the intermediate transfer belt cleaning motor 113, there is an advantage that the post cleaning roller 107 can be stably rotated.

  FIG. 13 is a graph in which the relationship between the amount of biting of the post cleaning roller 107 with respect to the intermediate transfer belt 2 and the number of spot-like abnormal images generated is examined. The number of stain-like abnormal images generated is such that, in a high-temperature / high-humidity environment, 50 continuous images of M, C, and B colors are output continuously, then 50 Y-color solid images are output, and the output Y-color solid image This is the number of images where a spot-like abnormal image was confirmed by visually checking the image. As can be seen from FIG. 13, there is no difference in the relationship between the applied bias and the number of generated spot-like images when the biting amount is 0.5 [mm] and when the biting amount is 0.05 [mm] in consideration of data variation. It was. From the viewpoint of driving load, the smaller the biting amount, the better. However, in consideration of the variation of the biting amount, 0.05 to 0.35 [mm] is a desirable range in actual use. However, it is sufficient to raise the motor rating for torque, so from the standpoint of preventing the occurrence of spot-like abnormal images due to re-adhering toner, it can be used with no significant difference at a biting amount of at least 0.05 [mm] to 0.5 [mm]. is there.

  In addition, the present applicant examined the number of occurrences of a spot-like abnormal image similar to the above using a sponge roller having an Asker C hardness of 28 degrees and a sponge roller having an Asker C hardness of 45 degrees. As a result, there was no difference in the relationship between the number of spot-like abnormal images generated and the applied bias between 28 degrees and 45 degrees in Asker C hardness, which was the same as the graph shown in FIG. From the standpoint of driving load and from the standpoint of setability in which the post cleaning roller 107 is set while being crushed with respect to the post collection roller 108, the post cleaning roller 107 is preferably soft. From the viewpoint of preventing the occurrence of spot-like abnormal images due to the reattached toner, at least Asker C hardness of 28 degrees to 45 degrees can be used without much difference. In this embodiment, the Asker C hardness of the post cleaning roller 107 is set to 35 degrees. By setting the Asker hardness to 35 degrees, the Asker altitude of the post cleaning roller 107 can be made 28 degrees or more and 45 degrees or less even if mass production variation is included.

  The post collection roller 108 is a stainless steel (SUS) roller, like the first collection roller 102 and the second collection roller 105, and can adopt the same configuration as the first collection roller 102 and the second collection roller 105. . Of course, the post collection roller 108 may be made of any material as long as it can perform the function of transferring the toner adhering to the post cleaning roller 107 to the post collection roller 108 by the potential gradient with the post collection roller 108. . The post recovery roller 108 is also covered with a high resistance elastic tube of several [μm] to 100 [μm] on the conductive mandrel, or further coated with an insulating coating so that the roller resistance is logR = 12 to 14 [Ω · cm You may use what was set to].

  Further, from the viewpoint of driving load, the post collection roller 108 is preferably configured to rotate with the post cleaning roller 107. The contact pressure between the post collection roller 108 and the post cleaning roller 107, which is a sponge roller, is stronger than the brush roller, and the driving load is increased. Further, since the contact pressure is strong, the post collection roller 108 can be rotated with the metal roller stably. This eliminates the need for a drive mechanism for driving the post collection roller 108, reduces the number of parts, and reduces the cost of the apparatus. Of course, the post recovery roller 108 may be rotationally driven by transmitting a driving force from the drive motor to the post recovery roller 108.

  As described above, the post-cleaning roller 107 has reattached toner that has reattached to the intermediate transfer belt 2 from the second cleaning brush roller 104 and a very small amount of negative polarity toner that could not be removed by the second cleaning brush roller 104. Be transported. A very small amount of negative polarity toner and re-adhering toner transferred to the post cleaning roller 107 are electrostatically attached to the post cleaning roller 107 to which a voltage having a polarity opposite to the normal charging polarity of the toner is applied. Then, the toner is recovered by the post recovery roller 108 and scraped off from the post recovery roller 108 by the post toner scraping blade 109. After being scraped off from the post collection roller 108 by the post scraping blade 109, it is transported from the post cleaning unit 100c to the toner reservoir by the post transport screw 110c.

The conditions of the cleaning brush rollers 101 and 104 are as follows. Brush material: conductive polyester (the first brush has a structure with a conductive material on the fiber surface, the second brush has conductive carbon inside the fiber, and the fiber surface has a polyester, so-called core-sheath structure. (Available at brush manufacturers such as Toei Sangyo Co., Ltd.)
Brush resistance: 10 ⁶ to 10 ⁸ [Ω]
・ Brush flocking density: 60,000 to 150,000 [lines / inch ² ]
・ Brush fiber diameter: about 25 to 35 [μm]
-Brush tipping treatment: None-Brush diameter φ: 14-20 [mm]
-Brush fiber biting amount into the intermediate transfer belt 2: 1 to 1.5 [mm]

The conditions of the post cleaning roller 107 are as follows.
・ Cleaning roller material: Conductive polyurethane (manufactured by Yamauchi Co., Ltd.)
・ Diameter φ: 14-20 [mm]
・ Resistance: 107.25 ± 0.25 [Ω]
・ Hardness: Asker C35 degrees ・ Intermediate transfer belt biting amount: 0.05 [mm] to 0.4 [mm]
The material of the post cleaning roller 107 is not limited to conductive polyurethane, and any material having a smooth or porous surface may be used.

  The voltage applied to the first cleaning brush roller 101 is set so that when the secondary transfer residual toner is input to the intermediate transfer belt 2, the reverse polarity charged toner is eliminated. Specifically, the toner after passing through the first cleaning brush roller is experimentally determined by air suction and put in a Faraday cage or the like, or by examining toner adhesion after cleaning.

  The second cleaning brush roller 104 is set so that the toner on the intermediate transfer belt 2 can be cleaned. Further, the brush flocking density, brush resistance, fiber diameter, applied voltage, fiber type, and brush fiber biting amount can be optimized by the system, and thus are not limited thereto. Examples of the types of fibers that can be used include nylon, acrylic, and polyester.

The conditions of each collection roller 102, 105, 108 are as follows.
・ Recovery roller core material: SUS303
-Brush fiber biting amount into the collection roller: 1 to 1.5 [mm]
・ Roller bite amount: 0.5mm

  The collection roller material, brush fiber entrapment amount, and applied voltage can be optimized by the system, and are not limited thereto.

The conditions of each scraping blade 103, 106, 109 are as follows.
・ Recovery roller core material: SUS304
・ Blade contact angle: 20 [°]
・ Blade thickness: 0.1 [mm]
・ Amount of blade biting into the collection roller: 0.5 to 1.5 [mm]

  The blade contact angle, the blade thickness, and the amount of biting into the collection roller can be optimized by the system, and are not limited thereto.

  In the intermediate transfer belt cleaning device 10, a voltage is applied to each of the collecting rollers 102, 105, and 108, each of the cleaning brush rollers 101 and 104, and the post cleaning roller 107. However, a voltage may be applied only to the collecting roller. Good.

  In this case, a bias voltage somewhat lower than the bias voltage applied to the recovery roller through the contact portion with the recovery roller is applied to the cleaning roller and the post cleaning roller due to a potential drop due to the resistance of the cleaning brush roller or the post cleaning roller. Applied. As a result, a potential difference is formed between the collection roller and the cleaning brush roller and between the post cleaning roller and the post collection roller, and the toner can be electrostatically moved to the collection roller by a potential gradient in the direction of the collection roller. it can.

  The cleaning current that provides the best cleaning is a target current that flows through the contact points between the cleaning brush rollers 101 and 104 and the post cleaning roller 107 and the intermediate transfer belt 2. Table 1 shows an example of the target current value. In Table 1, 1st means the first cleaning brush rollers 101, 2 nd are the second cleaning brush rollers 104, 3 rd are the post cleaning rollers 107. In the present embodiment, the first cleaning brush roller 101 is set to a constant voltage.

  The process linear velocity in the embodiment is 350 [mm / s]. Of course, it is possible to cope with a process linear velocity of 100 to 800 [mm / s].

  The target current may be a value proportional to the linear velocity. For example, when the process linear velocity is 175 [mm / s] which is half of 350 [mm / s], the target current value may be half of the process linear velocity 350 [mm / s]. In addition, when the process linear velocity is 700 [mm / s], which is twice the 350 [mm / s], the target current value may be set twice the process linear velocity 350 [mm / s].

Further, it is more preferable that the flocking density of the second cleaning brush roller 104 is smaller than that of the first cleaning brush roller 101 to be 15,000 to 20,000 [lines / inch ² ].

  Table 2 below shows the results of experiments conducted by changing the brush flocking density and the brush thickness of the second cleaning brush roller 104.

  The above Table 2 shows that after performing three times the operation of outputting all the solid images of M, C, and B in a high-temperature and high-humidity environment where a spot-like abnormal image is likely to occur, This is the number of sheets where 50 solid images were output, and the output Y-color all-solid images were confirmed visually, and a spot-like abnormal image was confirmed. Further, -1400 [V] was applied to the first cleaning brush roller 101, 1200 [V] was applied to the second cleaning brush roller 104, and 2500 [V] was applied to the post cleaning roller 107.

As shown in Table 2 above, by making the brush flock density of the second cleaning brush roller 104 lower than that of the first cleaning brush roller 101, the number of occurrences of spot-like abnormal images due to reattached toner is suppressed. I understand that. This is thought to be due to the fact that by reducing the flocking density, the number of raised hairs is reduced, the amount of toner held by the brush is reduced, and the amount of reattached toner that is reattached from the second cleaning brush roller 104 to the intermediate transfer belt 2 is reduced. It is done. Further, a similar experiment was performed by changing the experimental environment. However, by using a 14 denier, 20,000 [lines / inch ² ] brush as the second cleaning brush roller 104, the occurrence of a spot-like image is suppressed. I was able to.

  It is preferable that the brush be as thick as possible so that the brush contacts the intermediate transfer belt 2 as much as possible at the contact position. By making the brush contact the intermediate transfer belt 2 as much as possible at the contact position, the secondary transfer residual toner on the intermediate transfer belt 2 can be reliably brought into contact with the brush, and the secondary transfer residual toner can be removed well. can do.

FIG. 14 is a graph obtained by examining the correlation between the brush flocking density and the brush thickness. From FIG. 14, it seems that there is an approximate relationship of the following formula for the flocking density of 15,000 to 20,000 [lines / inch ² ].

Brush thickness (denier) = − 0.0032 × Flocking density (book / inch ² ) +78

  However, even if the brush thickness is larger than this formula, the cleaning property is improved.

  FIG. 15 is a timing chart showing on / off timings of bias applied to the cleaning brush roller and post cleaning roller, bias applied to the recovery roller, photosensitive member drive, intermediate transfer belt drive, intermediate transfer belt cleaning device drive, and the like. is there. Note that the first cleaning bias in FIG. 15 is a bias applied to the first cleaning brush roller 101. The second cleaning bias is a bias applied to the second cleaning brush roller 104. The third cleaning bias is a bias applied to the post cleaning roller 107. The first collection bias is a bias applied to the first collection roller 102, the second collection bias is a bias applied to the second collection roller 105, and the third collection bias is applied to the post collection roller 108. Bias.

  Conventionally, driving of the intermediate transfer belt and driving of the intermediate transfer belt cleaning device (that is, driving of two cleaning brush rollers, a post cleaning roller, and three recovery rollers) have been performed simultaneously. However, it has been found that when the driving is started in this way, it becomes difficult to control the driving of the intermediate transfer belt. When a large number of image forming apparatuses are made, some of the variations have a small driving load on the intermediate transfer belt. A small driving load means that it is easy to move. This means that it is easily moved by driving other units. In other words, it means that it is susceptible to load fluctuations of other units. In particular, at the start of driving, the control unit 200 gradually stabilizes the intermediate transfer belt while increasing or decreasing the speed of the intermediate transfer belt too much. It turned out that it might become such a situation. In this embodiment, when the machine is stopped, all the photoreceptors 3 (Y, C, M, B) are separated from the intermediate transfer belt 2, and the secondary transfer belt 9C is also separated from the intermediate transfer belt 2. . Therefore, these driving loads do not cause an abnormality at the start of the intermediate transfer belt driving.

  The cleaning brush rollers 101 and 104 and the post cleaning roller 107 of the intermediate transfer belt cleaning device 10 are desirably kept in contact with each other in order to remove foreign matters on the intermediate transfer belt 2. Naturally, the cleaning brush rollers 101 and 104 and the post cleaning roller 107 remove foreign matters on the intermediate transfer belt 2, and therefore it is necessary to apply a certain load to the intermediate transfer belt 2. As described above, particularly the post cleaning roller 107 affects the load torque applied to the intermediate transfer belt motor 2BM. Therefore, an experiment is performed using an image forming apparatus that detects an abnormality at the start of driving of the intermediate transfer belt by changing the drive timing of the intermediate transfer belt cleaning motor 113 and the intermediate transfer belt drive motor 2BM and causing a variation in the intermediate transfer belt drive load. Was done. The results are as follows. In addition, the gain in the following is responsiveness in feedback control.

(1) After the intermediate transfer belt cleaning motor 113 is stabilized, the intermediate transfer belt drive motor 2BM is started (500 [msec] delay) → speed fluctuation occurs (2) the intermediate transfer belt drive motor control gain at the time of activation is lowered → Speed fluctuation occurrence (3) Slow start-up of the intermediate transfer belt drive motor 2BM at startup (rise time 150 [msec] → 300 [msec]) → Speed fluctuation occurrence (4) Intermediate transfer belt drive at startup Decrease motor control gain and slow start-up ((2) + (3)) → Generation of speed fluctuation (5) After the intermediate transfer belt drive motor 2BM is stabilized, the intermediate transfer belt cleaning motor 113 is set to 85 [ %] (150 [msec] delay). After that, the intermediate transfer belt cleaning motor 113 is started up to 100 [%] (the rotation speed is switched from 85 [%], and then 100 [%] is stable at 300 [msec]) → No speed fluctuation occurs

  About the said result, it thinks as follows. In the above (2), (3), and (4) in which the speed fluctuation has occurred, the intermediate transfer belt cleaning device 10 (intermediate transfer belt cleaning motor 113) is also activated while the intermediate transfer belt drive motor is activated. This is because the intermediate transfer belt drive motor 2BM is affected by the effects of the rotation of the cleaning brush rollers 101 and 104 and the post cleaning roller 107 of the intermediate transfer belt cleaning device 10 being overshooted and stabilized. I mean. For this reason, it is considered that the control on the intermediate transfer belt drive motor 2BM side becomes complicated and cannot be controlled completely and becomes abnormal. With regard to (1), the driving load is considerably reduced even when the cleaning brush rollers 101 and 104 or the post cleaning roller 107 of the intermediate transfer belt cleaning device 10 are moving or not moving the intermediate transfer belt 2. It becomes a state. Under such circumstances, the overshoot of the intermediate transfer belt drive becomes larger than usual, and it is considered that the control is not performed well.

  FIG. 19 is a graph showing an example of the relationship between the intermediate transfer belt drive timing and the intermediate transfer belt cleaning drive timing in (5) above. Note that a graph A in the figure indicates the intermediate transfer belt drive. Graph B shows the intermediate transfer belt cleaning drive when the speed is raised to the final speed in two stages. Graph C shows the intermediate transfer belt cleaning drive when starting up from the beginning aiming at the final speed as a comparative example. Also, t = 0 in the figure is the intermediate transfer belt cleaning drive start time.

  For the above (5) in which no speed fluctuation occurred, the intermediate transfer belt cleaning motor 113 is started after the intermediate transfer belt drive is stabilized. Further, the intermediate transfer belt cleaning motor 113 is first raised to a speed of 85 [%], and then raised to a target speed, so that the overshoot of the intermediate transfer belt cleaning device 10 is reduced and no abnormality occurs. I think. Here, the speed of 85 [%] is a speed obtained by subtracting the maximum overshoot amount of the roller linear speed of the intermediate transfer belt cleaning device 10 from the intermediate transfer belt linear speed. In (5) above, the time (150 [msec]) for which the intermediate transfer belt cleaning motor 113 is stabilized after the intermediate transfer belt cleaning motor 113 is started up to 85 [%] is set in advance. When the set time has elapsed, control is performed to raise the intermediate transfer belt cleaning motor 113 to 100 [%]. However, the present invention is not limited to this. For example, after the intermediate transfer belt cleaning motor 113 is raised to 85 [%], if it is detected by a sensor or the like that the intermediate transfer belt cleaning motor 113 is stabilized, control may be performed to raise it to 100 [%]. good.

  Further, an experiment was also conducted in which the intermediate transfer belt cleaning motor 113 is simply started after the intermediate transfer belt drive motor 2BM is stabilized. This sometimes detected an abnormality in the experimental machine, but no abnormality was detected in a machine with a high margin. Therefore, a certain effect can be expected by simply delaying the start-up of the intermediate transfer belt cleaning motor 113.

From the above experiment, it seems that the phenomenon of speed abnormality is summarized as follows.
(1) An intermediate transfer belt cleaning device 10 including belt cleaning rollers (first cleaning brush roller 101, second cleaning brush roller 104, and post cleaning roller 107) that rotate in the forward direction with respect to the intermediate transfer belt conveyance direction.
(2) When the intermediate transfer belt 2 and the intermediate transfer belt cleaning device 10 are activated simultaneously,
(3) When the rotational speed of the intermediate transfer belt cleaning motor being started causes a speed overshoot,
(4) When the rotational speed of the belt cleaning roller exceeds the conveyance speed of the intermediate transfer belt 2,
(5) The intermediate transfer belt 2 is conveyed by the belt cleaning roller.
(6) Transmission of drive torque from the intermediate transfer belt drive motor 2BM to the intermediate transfer belt 2 is hindered,
(7) The intermediate transfer belt drive speed control cannot be normally performed and a large error occurs in the intermediate transfer belt speed.
(8) An intermediate transfer belt speed control error occurred. Here, as described above, the speed abnormality is determined to be abnormal when the deviation from the target exceeds ± 5 [%] in the present embodiment.

  Therefore, in the copying machine 1 of the present embodiment, driving and bias application are performed at the timing shown in FIG. This will be described below. In the copying machine 1 of the present embodiment, the photoreceptor 3 and the secondary transfer belt 9C are separated from the intermediate transfer belt 2 when the machine is stopped. Only the cleaning brush rollers 101 and 104 and the post cleaning roller 107 of the intermediate transfer belt cleaning device 10 are in contact with the intermediate transfer belt 2. In this state, first, the intermediate transfer belt drive is started. After the intermediate transfer belt linear velocity is stabilized, driving of the intermediate transfer belt cleaning device 10 is started. The stabilization of the intermediate transfer belt drive is determined based on a signal from a separately provided intermediate transfer belt speed detection unit. Of course, for simplification, the intermediate transfer belt cleaning device 10 may be moved after waiting for a certain time (for example, 300 [ms]) from the start of driving the intermediate transfer belt in consideration of variations.

  When the intermediate transfer belt cleaning device 10 is moved after waiting for a certain time from the start of the intermediate transfer belt drive, the intermediate transfer belt cleaning drive is started after 300 msec from the start of the intermediate transfer belt drive. The intermediate transfer belt cleaning drive is performed in two stages. First, drive control is performed for 150 [msec] with 85 [%] of the target rotational speed (target value of final speed) of the intermediate transfer belt cleaning device 10 as a target. Next, the drive rotation speed target value is set to the original set value (target value of the final speed) and brought to the target value. The number “150” is a number that varies depending on the motor start-up performance, but it may be set to a time shorter than the motor start-up nominal value. That is, in a strict sense, it is not necessary to reach the rotational speed of 85 [%] within 150 [msec]. The rotational speed is raised to a value smaller than the target value in a short time, and then a little time is taken. It is important to take the rotational speed. This is because the aim of such control is to suppress the overshoot of the driving speed.

  In motors currently in common use, in actual use, the initial target value is 60 [%] to 95 [%], preferably 80 [%] to 90 [%], and more preferably 85 [%]. This is a good first target value to suppress overshoot. The control time is preferably equal to or shorter than the nominal rise time of the motor. In the apparatus of this embodiment, 150 [msec] is 1/5 of the nominal value 750 [msec]. The control time may be set between 1/10 and 1/2 of the nominal value. Thus, by setting the speed control below the nominal value of the rise of the motor, the time from the start of the intermediate transfer belt drive until the intermediate transfer belt drive speed reaches the target value is within one second.

  At the same time as the driving of the intermediate transfer belt cleaning device 10 is started, the cleaning bias and the recovery bias are turned ON. Next, when the linear transfer target value of the intermediate transfer belt cleaning device 10 is set to the original target value and drive control is started, the drive for bringing the intermediate transfer belt 2 into contact with the photosensitive member 3 is started and simultaneously the photosensitive member. Start driving. At the same time, the movement of bringing the secondary transfer belt 9C into contact with the intermediate transfer belt 2 also starts. Then, after the photoreceptor 3 and the intermediate transfer belt 2, and the secondary transfer belt 9C and the intermediate transfer belt 2 are in contact with each other, primary transfer biases for the four photoreceptors 3 (Y, C, M, B), and secondary The transfer bias is turned on, and then an image forming operation is started. After the secondary transfer to the recording medium such as paper is completed, the driving around the intermediate transfer belt 2, the primary transfer bias, and the secondary transfer bias are turned off in the following order.

  The timing at which the recording medium such as paper has completed the secondary transfer can be identified from the previously known paper size information, the paper transport linear velocity, the layout distance of the registration rollers that transport the paper to the secondary transfer area, and the drive ON timing. . At this secondary transfer end timing, the secondary transfer bias and the primary transfer bias are turned off. If the primary transfer bias is turned off before the secondary transfer, the force relationship between the intermediate transfer belt 2 and the photosensitive member 3 changes and the movement of the intermediate transfer belt 2 may change. Therefore, the primary transfer bias is also continuously applied. is there. Next, the photosensitive member separation operation start and the photosensitive member drive stop operation are started, and then all of the intermediate transfer belt drive, the intermediate transfer belt cleaning drive, and the cleaning bias and the recovery bias of the intermediate transfer belt cleaning device 10 are turned off. The The intermediate transfer belt cleaning bias may be turned off after all others are stopped. This is because foreign matters such as toner on the intermediate transfer belt 2 are attracted to the cleaning brush rollers 101 and 104 and the post cleaning roller 107.

  Regarding the stop, the intermediate transfer belt drive, the intermediate transfer belt cleaning drive, the cleaning bias, and the recovery bias are simultaneously turned OFF for the following reason. That is, when the images are simultaneously turned off as described above, the image cannot be formed, so there is no problem even if the linear speed of the intermediate transfer belt 2 slightly changes, and no abnormality is detected. The machine can be quickly stopped by simultaneously turning off the intermediate transfer belt drive, the intermediate transfer belt cleaning drive, the cleaning bias, and the recovery bias.

  The copying machine 1 performs setting change processing of the applied voltage of the intermediate transfer belt cleaning device 10 other than at the time of process control that is performed every time the power is turned on or every time a predetermined number of prints are performed. Specifically, when the measured value of the temperature / humidity sensor changes by a predetermined value or more as compared with the measured value of temperature / humidity recorded during the previous setting change process, the setting change process for the voltage setting value is performed.

  For example, when the temperature change is 10 [° C.] or more or the humidity change is 50 [%] or more, a setting change process is executed for the second cleaning brush roller 104 and the post cleaning roller 107. Then, the setting of the applied voltage is changed so that the target current value of the setting table corresponding to the current temperature and humidity measurement value is obtained.

  In this embodiment, the temperature / humidity environment is broadly divided into three and has three types of setting values. However, in order to respond more finely, the temperature / humidity environment is further divided into three or more types of setting values. You may have it.

  FIG. 16 is a schematic configuration diagram illustrating a power supply unit included in the intermediate transfer belt cleaning device 10. The applied voltage setting change process of the intermediate transfer belt cleaning device 10 is performed in a state where the intermediate transfer belt 2 and the intermediate transfer belt cleaning device 10 are driven and no toner is input to the intermediate transfer belt cleaning device 10. Here, in the present embodiment, the voltage setting values of the applied voltages of the cleaning brush rollers 101 and 104, the post cleaning roller 107, and the recovery rollers 102, 105, and 108 are simultaneously changed. Therefore, a predetermined voltage is applied from the six power supplies 130, 131, 132, 133, 134, 135 connected to the cleaning rollers 101, 104, 107 and the collection rollers 102, 105, 108, respectively.

  Here, in order to simplify the control, a constant voltage corresponding to each environment is applied to the first cleaning brush roller 101 and the first recovery roller 102 from a power source. For this reason, the first cleaning power supply unit 130 that applies a voltage to the first cleaning brush roller 101 and the first recovery power supply unit 131 that applies a voltage to the first recovery roller 102 receive the current flowing through the power supply of each power supply unit. It does not have a detection unit to detect.

  On the other hand, the second cleaning power supply unit 132 that applies a voltage to the second cleaning brush roller 104 includes a power supply 132a and a detection unit 132b that detects a current value IB2 flowing through the power supply 132a. The second recovery power supply unit 133 that applies a voltage to the second recovery roller 105 also includes a power supply 133a and a detection unit 133b that detects a current value IC2 flowing through the power supply 133a.

  Further, the third cleaning power supply unit 134 that applies a voltage to the post-cleaning roller 107 includes a power supply 134a and a detection unit 134b that detects a current value IB3 flowing through the power supply 134a. The third recovery power supply unit 135 that applies a voltage to the post recovery roller 108 is also provided with a power source 135a and a detection unit 135b that detects a current value IC3 flowing through the power source 135a.

  A voltage is specified such that the total value IT2 (IB2 + IC2) of the current value IB2 and the current value IC2 and the total value IT3 (IB3 + IC3) of the current value IB3 and the current value IC3 respectively become target current values. And the voltage setting value of the applied voltage of each cleaning roller 104,107 and each collection | recovery roller 105,108 is changed simultaneously.

  In the subsequent image forming operation, this set value is used until the voltage set value is next changed.

  FIG. 17 shows a flowchart of an example of the voltage set value changing process. In FIG. 17, since the same voltage set value changing process is simultaneously performed on the cleaning units 100b and 100c, the cleaning units 100b and 100c are not distinguished. In the following description, the post-cleaning roller 107 and the second cleaning brush roller 104 are referred to as “cleaning rollers” unless otherwise distinguished. When the voltage setting value is changed, the voltage applied first to each of the cleaning rollers 104 and 107 and the collecting rollers 105 and 108 is stored as the initial value of the voltage when the voltage setting was changed last time. Read it out and do it. The voltage value shown in Table 1 is an example of the initial value.

  This is because when a voltage far from the voltage to be set is applied, the current flowing through the intermediate transfer belt 2 and flowing between the cleaning rollers increases, and the deterioration of the cleaning rollers 101, 104, 107 and the intermediate transfer belt 2 is accelerated. It is because it ends.

  First, based on the measurement value of the temperature and humidity sensor in the printer, the target current value of the temperature and humidity environment corresponding to the measurement value is read from the setting table shown in Table 1 (S1). Next, a first cleaning bias and a first recovery bias are applied (S2).

  Next, a predetermined voltage is applied from the four power sources 132a, 133a, 134a, and 135a connected to the cleaning rollers 104 and 107 and the collection rollers 105 and 108, respectively (S3).

  At this time, the voltages VB2 and VB3 applied to the cleaning rollers 104 and 107 are read as the initial values of the voltages when the previous voltage setting change stored as described above is used. As the voltages VC2 and VC3 applied to the collecting rollers 105 and 108, voltages higher by 400 [V] than the voltages VB2 and VB3 are used.

  Then, current values IB2 and IB3 flowing through 132a and 134a for applying voltages to the cleaning rollers 104 and 107 are detected. Similarly, current values IC2 and IC3 flowing through the power supplies 133a and 135a that apply voltages to the collecting rollers 105 and 108 are detected. Further, a total value IT2 (IB2 + IC2) of the current value IB2 and the current value IC2 and a total value IT3 (IB3 + IC3) of the current value IB3 and the current value IC3 are obtained from the detected current values (S4).

  Then, it is determined whether the total values IT2 and IT3 are within the range of 80 [%] of the target current value and 120 [%] of the target current value (S5).

  If the total values IT2 and IT3 are in the range of 80% or more of the target current value and 120% or less of the target current value (YES in S5), the voltages VB2 and VB3, and the voltages VC2 and VC3 at that time Is determined as a voltage setting value (S6). Thereby, a series of voltage setting change processing is complete | finished (S7).

  On the other hand, if the total values IT2 and IT3 are not within the range of 80% or more of the target current value and 120% or less of the target current value (NO in S5), the total values IT2 and IT3 are the target current value. It is determined whether it is smaller than the lower limit (S8).

  If the total values IT2 and IT3 are smaller than the lower limit of the target current value (YES in S8), a voltage that is 100 [V] higher than the voltages VB2 and VB3 is obtained, and this is set to voltages VB'2 and VB'3. . Further, a voltage that is 400 [V] higher than the voltages VB'2 and VB'3 is obtained, and these are set as voltages VC'1, VC'2, and VC'3 (S9).

  Conversely, when the total values IT2 and IT3 are larger than the lower limit of the target current value (NO in S8), a voltage that is 100 [V] lower than the voltages VB2 and VB3 is obtained, and this is obtained as the voltages VB′2 and VB ′. Do 3 Further, a voltage that is 400 [V] higher than the voltages VB'2 and VB'3 is obtained and set as voltages VC'2 and VC'3 (S10).

  Then, VB'2 and VB'3 are applied to the cleaning rollers 104 and 107, and voltages VC'2 and VC'3 are applied to the recovery rollers 105 and 108 (S11). Thereafter, the current values IB2 and IB3 and the current values IC2 and IC3 are detected, and the series of controls as described above are repeated.

  In the present embodiment, the current value is detected at a timing after both the second cleaning brush roller 104 and the post cleaning roller 107 have made one rotation or more after voltage application. This is because, as a result of the study by the present inventor, it has been found that the currents of the second cleaning brush roller 104 and the post cleaning roller 107 change after that in the first round. Therefore, if the setting operation is performed while the second cleaning brush roller 104 or the post cleaning roller 107 is making the first rotation, the setting takes time and is undesirable.

  Further, the second cleaning brush roller 104 and the post cleaning roller 107 have a slight biting amount variation due to a variation in diameter or the like, and a resistance variation during production. Therefore, the current is also measured for one rotation of the second cleaning brush roller 104 or the post cleaning roller 107. Specifically, a data sample was waited for a time period from the time when the intermediate transfer belt drive was turned on (the outer peripheral length of the second cleaning brush roller 104 or the post cleaning roller 107 ÷ the rotational speed of the second cleaning brush roller 104 or the post cleaning roller 107). Thereafter, the current value of the data sample is read in units of 10 [msec] in accordance with the CPU clock, for example, and the average is obtained.

  The detection of the current value is performed in a state where the primary transfer bias and the secondary transfer bias are turned on and the intermediate transfer belt 2 to which the primary transfer bias and the secondary transfer bias are added passes through the cleaning rollers 104 and 107. preferable. This is because the resistance of the intermediate transfer belt 2 may change when a primary transfer bias or a secondary transfer bias is applied to the intermediate transfer belt 2. Therefore, by detecting the current value in this way, each bias can be set in consideration of a change in resistance of the intermediate transfer belt 2, and the bias can be set with higher accuracy.

  These current measurements may be performed during image output as well as during setting. Measuring current during image output is very convenient for service personnel to identify the cause when cleaning failure occurs. If a target current does not flow in the first place when a cleaning failure occurs, the voltage setting may be changed so that the target current flows. If the current is as intended, other causes such as a brush defect can be considered, and the cause can be clarified at an early stage.

  For the current measurement at the time of image output, the above-described detection units 132b and 134b may perform the same operation as at the time of voltage setting at the same timing as the image output. Specifically, the service man operates the operation panel to execute the current measurement mode. When the current measurement mode is executed, the current is synchronized with the image output, for example, the timing at which the area after the secondary transfer of the image calculated from the linear velocity is applied to the cleaning roller in synchronization with the registration roller ON timing. Start detection. Then, a sample of the cleaning roller is sampled and averaged and displayed on the operation panel of the copying machine 1 or the like.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
(Aspect 1)
In the copying machine 1 that is an image forming apparatus, an intermediate transfer belt 2 that is an image carrier, an intermediate transfer belt drive motor 2BM that drives the intermediate transfer belt 2, and an intermediate transfer belt that is a cleaning body that contacts the intermediate transfer belt 2 The intermediate transfer belt driving motor 2BM has a cleaning device 10 and an intermediate transfer belt cleaning motor 113 which is a cleaning body driving means different from the intermediate transfer belt driving motor 2BM for driving the intermediate transfer belt cleaning device. Later, the driving of the intermediate transfer belt cleaning motor 113 is started.
By starting driving in this way, after the speed control of the intermediate transfer belt 2 is started and stabilized, noise due to the speed control of the intermediate transfer belt cleaning device 10 enters the intermediate transfer belt speed control. As a result, it is possible to prevent the occurrence of an abnormality without partitioning the intermediate transfer belt speed control and to stabilize the speed control.
(Aspect 2)
In (Aspect 1), the speed control of the intermediate transfer belt cleaning motor 113 is at least two stages. By increasing the speed stepwise in this way, the rotational speed overshoot of the post cleaning roller 107 and the like can be suppressed, and the intermediate transfer belt speed control can be stabilized.
(Aspect 3)
In (Aspect 2), the speed of the intermediate transfer belt cleaning device 10 is controlled at a speed that is slower than the final target speed as the first stage, and the final target speed is set as the second stage. Control the target value. As described above, by approaching the final speed from the slow speed, the rotation speed overshoot of the cleaning roller 107 and the like can be suppressed, and the intermediate transfer belt speed control can be stabilized.
(Aspect 4)
In (Aspect 3), the speed (linear speed) of the intermediate transfer belt 2 in which the speed slower than the final target speed is the speed variation at the start of driving of the intermediate transfer belt cleaning motor 113 is the image carrier speed. It is below the subtracted speed. By doing so, even if the rotation of the intermediate transfer belt cleaning motor 113 overshoots, the speed of the intermediate transfer belt 2 does not exceed the target value, and the occurrence of speed abnormality can be prevented more reliably.
(Aspect 5)
In (Aspect 1) to (Aspect 4), the driving speed of the intermediate transfer belt cleaning is within one second from the start of driving of the intermediate transfer belt to the target value. By doing so, the image forming apparatus can be used at an early stage.
(Aspect 6)
In (Aspect 1) to (Aspect 5), an image forming unit including a plurality of photoreceptors such as the photoreceptors 3 (Y, C, M, and B), and an image developed on each photoreceptor are sequentially transferred. An intermediate transfer member such as an intermediate transfer belt 2, a secondary transfer unit that transfers an image on the intermediate transfer member to a recording medium, and at least one post that removes toner remaining on the intermediate transfer member after the secondary transfer. A cleaning roller such as a cleaning roller 107 and at least two cleaning brush rollers such as a first cleaning brush roller 101 and a second cleaning brush roller 107 are provided, and cleaning biases having different polarities are applied to the two cleaning brush rollers. Intermediate transfer in which a cleaning bias having a polarity opposite to the normal charging polarity of the toner is applied to the cleaning roller. And an image forming apparatus having an intermediate transfer member cleaning means such as a belt cleaning device 10. Such an image forming apparatus can provide a stable image over a long period of time, but has a large cleaning load on the intermediate transfer member. By combining with the contents of (Aspect 1) to (Aspect 5), it is possible to continue to provide truly stable image quality.

1: Copier 2: Intermediate transfer belt 6: Developing device 9C: Secondary transfer belt 10: Intermediate transfer belt cleaning device 66: Image forming unit 100a: First cleaning unit 100b: Second cleaning unit 100c: Post cleaning unit 101: First cleaning brush roller 102: first recovery roller 103: first scraping blade 104: second cleaning brush roller 105: second recovery roller 106: second scraping blade 107: post cleaning roller 108: post recovery roller 109: Post scraping blade 110a: first transport screw 110b: second transport screw 110c: post transport screws 111a, 111b, 111c: inlet seals 112a, 112b, 112c: outlet seal 120a: first casing 120 : Second casing 120c: post casing 130: first cleaning power supply 131: first recovery power supply 132: second cleaning power supply 133: second recovery power supply 134: third cleaning power supply 135: third recovery power supply 200: Control unit 211: Base layer 212: Elastic layer 213: Surface layer 300: Optical sensor

JP 2007-121568 A JP 2012-208485 A

Claims (6)

An image carrier;
Image carrier driving means for driving the image carrier;
A cleaning body in contact with the image carrier;
A cleaning body driving means different from the image carrier driving means for driving the cleaning body,
An image forming apparatus, wherein driving of the cleaning body driving unit is started after driving of the image carrier driving unit is started. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the speed of the cleaning body driving means is increased in at least two stages. The image forming apparatus according to claim 2.
In the first stage, the speed of the cleaning body is controlled at a speed lower than the final target speed, and in the second stage, the final target speed is controlled as a target value. An image forming apparatus. The image forming apparatus according to claim 3.
2. An image forming apparatus according to claim 1, wherein a speed slower than the final target speed is equal to or lower than a speed obtained by subtracting a speed fluctuation at the start of driving of the cleaning body driving means from an image carrier speed. The image forming apparatus according to any one of claims 1 to 4,
The image forming apparatus according to claim 1, wherein the driving speed of the cleaning body driving means from the start of driving of the image carrier driving means is within 1 second until the final speed is reached. The image forming apparatus according to any one of claims 1 to 5,
An image forming unit including a plurality of photoconductors;
An intermediate transfer member to which the developed image is sequentially transferred on each photosensitive member;
Secondary transfer means for transferring the image on the intermediate transfer member to a recording medium;
It has at least one cleaning roller and at least two cleaning brush rollers for removing toner remaining on the intermediate transfer member after the secondary transfer, and cleaning biases of different polarities are applied to the two cleaning brush rollers. An image forming apparatus comprising: an intermediate transfer member cleaning unit to which a cleaning bias having a polarity opposite to a normal charging polarity of toner is applied to the cleaning roller.

Images