JP4307404B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image corresponding to target image information on a transfer material using an electrophotographic system, an electrostatic recording system, a magnetic recording system, or the like.

  Conventionally, for example, an electrophotographic system is used to form an image on a transfer material (paper, OHT sheet, gloss film, etc.), a printer (eg, laser beam printer, LED printer, etc.), a copier, a facsimile machine, a word processor, etc. The image forming apparatus is widely used.

  In an electrophotographic image forming apparatus, an electrostatic image (latent image) is formed on an image carrier that is generally a cylindrical electrophotographic photosensitive member (photosensitive drum), and this electrostatic image is a resin as a developer. Development is performed with toner particles composed of, and the like. An image (toner image) of toner particles is transferred onto a transfer material such as paper using electrostatic force. Thereafter, the toner image is melt-fixed (fixed) on the transfer material by heat and pressure applied by the fixing device, and becomes stable. 2. Description of the Related Art In recent years, electrophotographic image forming apparatuses have advanced functions such as color support and high speed.

  There are the following types of image forming apparatuses that form an image on a transfer material by superimposing a plurality of types of toner images, such as a color image forming apparatus. First, the toner images sequentially formed on the image carrier are transferred onto the transfer material carried on the transfer material carrier in the transfer unit, and a plurality of types of toner images are superimposed on the transfer material. There is a method (direct transfer method). In addition, the toner images sequentially formed on the image carrier are transferred onto the intermediate transfer member at the primary transfer portion each time, and a plurality of types of toner images are superimposed on the intermediate transfer member. There is a method (intermediate transfer method) in which toner images are collectively transferred onto a transfer material. Conventionally, a transfer material carrier as a transfer member that carries a toner image transferred from an image carrier directly or via a transfer material, an intermediate transfer member, a belt that is stretched around a plurality of rollers and moves endlessly, A conveyor belt and an intermediate transfer belt are widely used.

  As an image forming apparatus using a plurality of types of toner, a so-called tandem type image forming apparatus is particularly excellent in terms of high speed. Hereinafter, a tandem color image forming apparatus adopting a direct transfer method using a transfer material carrier will be described as an example.

  In a tandem type image forming apparatus, a plurality of image forming units including, for example, a cylindrical electrophotographic photosensitive member (photosensitive drum) as an image carrier and a developing unit as a developing unit that supplies toner onto the photosensitive drum. The units are arranged in series along the conveyance direction of the conveyance belt. A toner image is formed on the photosensitive drum of each image forming unit by using different types of toner (for example, magenta, cyan, yellow, and black toners). Then, the toner images are sequentially superimposed and transferred onto the transfer material on the conveyance belt from the photosensitive drum of each image forming unit by the action of a transfer unit to which a bias is applied. Thereafter, the transfer material is separated from the conveying belt, and after the toner image is fused and fixed thereon by the fixing device, it is discharged out of the device. On the other hand, toner remaining on the photosensitive drum without being transferred to the transfer material (transfer residual toner) is removed from the photosensitive drum by a cleaner as a cleaning unit including a cleaning member such as a cleaning blade. Hereinafter, a part including the image forming unit and the corresponding transfer means is referred to as an image forming station.

  Some electrophotographic image forming apparatuses as described above have a self-adjusting function using a test image. In other words, in an electrophotographic image forming apparatus, the density and chromaticity of an output image may vary due to the influence of toner image density and gradation characteristics (γ characteristics) due to changes in the surrounding environment and usage conditions. There is. Therefore, a test image (detection pattern) is periodically formed on the conveyor belt during non-image formation, and the density is detected by an optical sensor provided adjacent to the conveyor belt. Then, the image forming conditions are finely adjusted based on the detection result. Conventionally, many electrophotographic image forming apparatuses have a mechanism (image density control mechanism) that always maintains stable density and γ characteristics in this way.

  Furthermore, in a tandem type image forming apparatus, it is necessary to precisely control the image forming timing of each color in order to superimpose a plurality of color toner images with high accuracy. For this reason, a dedicated test image is formed on the conveyance belt, and the image formation timing of each color is finely adjusted based on the result detected by the optical sensor. Conventionally, many tandem type image forming apparatuses have a mechanism (color misregistration control mechanism, registration control mechanism) for preventing color misregistration in this way.

  By the way, when a jam (transfer material clogs in the transport path) occurs in the image forming apparatus, the image protrudes from the paper size, or the test image is directly formed on the transport belt by density control or the like. In such a case, toner remains on the conveyance belt. Therefore, a means for cleaning the toner is necessary.

  Conventionally, a method is known in which toner, dust, and the like remaining on a conveyance belt are transferred to a photosensitive drum and collected by a cleaner of the photosensitive drum. That is, at the time of cleaning the conveyor belt, the conveyor belt and the photosensitive drum are driven. For example, in an image forming apparatus having four image forming stations in the transport direction of the transport belt, the most upstream image forming station (first image forming station) has a negative value that is opposite to that during normal transfer. An eggplant polarity bias is applied. In the next image forming station (second image forming station) in the transport direction of the transport belt, the same positive polarity bias as that during normal transfer is applied to the transfer unit. Similarly, in the third and fourth image forming stations, negative polarity and positive polarity biases are applied to the transfer means, respectively. In this manner, biases having different polarities are alternately applied to the transfer unit for each image forming station along the moving direction of the conveying belt. As a result, a large amount of residual toner and dust having a negative polarity is reversed to the photosensitive drums at the first and third image forming stations, and those having a positive polarity are respectively reversed to the photosensitive drums at the second and third image forming stations. It is copied and removed from the conveyor belt. These residual substances that have moved onto the photosensitive drum are finally collected by a cleaner that removes deposits from the photosensitive drum.

  However, in an image forming apparatus employing a conveyor belt, dirt is gradually attached and grows on the conveyor belt during use, even though the conveyor belt cleaning operation as described above is periodically performed. There is. The adhering dirt eventually grows firmly attached to the surface of the conveyor belt and becomes very difficult to remove.

  According to the study by the inventors, the stain component is mainly calcium carbonate, and talc and kaolin may be contained depending on the type of paper used. In addition, the generation level tends to be conspicuously bad in a low temperature and low humidity environment. The principle of the adhesion of these stains is considered as follows.

  First, when the transfer material is separated from the transfer belt due to the adsorption force acting between the transfer material and the transfer belt, some paper powder is peeled off from the transfer material and remains attached on the transfer belt. . In particular, in a low-temperature and low-humidity environment, there is little attenuation of real charges and polarization charges that contribute to adsorption in paper and a conveyor belt, and the adsorption force works strongly. Therefore, peeling of the paper powder as described above tends to occur. Furthermore, since the moisture absorption of the paper is small, the adhesion (tack property) between the paper fiber and the filler is poor, and the filler is more easily peeled off as paper powder.

  The dirt remaining on the conveyance belt in this way cannot be removed by the conveyance belt cleaning operation as described above because of the adsorption force to the conveyance belt, and adheres while staying on the conveyance belt for a long time. Sometimes. When the fixing of such dirt starts, the releasability of the surface of the conveyor belt is remarkably lowered, and therefore, it becomes easy to fall into a vicious circle that accelerates the adhesion of paper powder and dust.

  The adverse effects due to the adhesion of dirt are significantly affected in density control and color misregistration control by the self-adjustment function using the test image as described above. In these controls, a test image is formed on the conveyance belt as described above, and is detected by an optical sensor. FIG. 8 shows a schematic configuration of an example of an optical sensor that detects specularly reflected light as an example. As shown in the drawing, the optical sensor 30 irradiates the surface of the conveyor belt with light emitted from a light emitting element 301 such as an LED, and detects the amount of regular reflected light by a light receiving element 302 such as a photodiode. That is, in the part where there is no toner, the light is reflected by the surface of the smooth conveying belt, so that the regular reflection light is large. On the other hand, when the amount of toner is large, irregular reflection light increases due to reflection on the surface of fine toner particles and the colorant (pigment) in the toner, so that the regular reflection component decreases. From such a correlation, the presence / absence and density of the test image can be detected.

  However, if dirt is attached to the transport belt, the amount of specular reflection light decreases due to irregular reflection due to the dirt. Therefore, the detection accuracy of the test image is lowered, and accurate density control and color misregistration control cannot be performed.

  Further, when the adhesion level of dirt is further deteriorated, the electrical resistance of the surface of the conveying belt is changed, and the smoothness of the surface of the conveying belt is lost due to unevenness due to the adhesion of dirt. For this reason, when a normal toner image is transferred onto a transfer material, the transfer electric field or transfer pressure varies depending on the location. And it may appear as image spots.

  Further, the attracting force of the transfer material to the transport belt also decreases, and the transport force becomes unstable, so that the color misregistration level may deteriorate and the transfer material may be wrinkled.

On the other hand, as a countermeasure against dirt on the conveyor belt, a dedicated cleaner is provided for the conveyor belt, and a cleaning member such as an elastic rubber blade (cleaning blade) is brought into contact with the conveyor belt to forcibly remove dirt from the conveyor belt. scrape it it is thought. In this case, however, the cost increases due to the addition of a dedicated cleaner. In addition, a waste toner container for storing waste toner and dirt collected by such a dedicated cleaner is separately required. For this reason, a user's hand is troubled at the time of replacement | exchange of this waste toner container. Furthermore, by bringing the cleaning member into contact with the conveyor belt, the driving torque of the conveyor belt becomes heavy, and the conveyor belt is likely to slip or break.

  As in the case of the above-described conveyor belt, the problem of contamination on the belt due to paper dust adhering when the transfer material is peeled from the contact state is an image of an intermediate transfer method using an intermediate transfer member as a transfer member. Also in the forming device.

By the way, Patent Document 1 discloses a position on a belt immediately before a transfer material is carried in order to prevent scratches on the surface of the belt due to paper dust or the like being caught on the tip of a cleaning blade provided for cleaning the belt. The present invention discloses that a toner image is formed and the toner is supplied to a cleaning blade as a lubricant. Such prior art requires a dedicated cleaner for cleaning the belt. Also, the toner image formed on the belt is such that it is supplied to the cleaning blade as a lubricant, and the toner image is more effectively removed by mixing the adhering material such as paper dust on the belt with the toner image. I can't do it.
Japanese Patent Laid-Open No. 11-258919

  An object of the present invention is to provide an image forming apparatus capable of effectively removing foreign matters such as paper dust adhering to a transfer material carrier or an intermediate transfer member.

  One of the more detailed objects of the present invention is to suppress the adhesion of dirt to the transfer material carrier or intermediate transfer member without adding a special member, and to carry the transfer material for controlling image forming conditions. It is an object of the present invention to provide an image forming apparatus capable of maintaining the detection accuracy of a test image formed on a body or an intermediate transfer body.

  One of the more detailed objects of the present invention is to prevent stain adhesion to a transfer material carrier or intermediate transfer body without adding a special member, and to suppress image spots and wrinkles of the transfer material. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides a movable image carrier that carries a toner image , a movable intermediate transfer member that receives a transfer of the toner image on the image carrier, and the intermediate transfer from the image carrier. A first mode in which a toner image is transferred onto a body, and a second mode in which the toner image on the image carrier is passed between the image carrier and the intermediate transfer body without being transferred onto the intermediate transfer body. In an image forming apparatus having a mode,
A cleaning process in which the image carrier carries a cleaning toner image for cleaning the intermediate transfer body, and the second mode is executed in the cleaning process, and the peripheral speed of the image carrier and the intermediate The image forming apparatus is characterized in that the peripheral speed difference from the peripheral speed of the transfer body is different between the first mode and the second mode.

According to another aspect of the present invention, a movable image carrier that carries a toner image , a transfer material carrier that carries a transfer material and is movable, and the image carrier on the transfer material on the transfer material carrier passing a first mode for transferring a toner image on the body, between the image bearing member and said transfer material bearing member to a toner image on the image carrier without transfer to the transfer material or the transfer material bearing member And an image forming apparatus having a second mode.
A cleaning process in which the image carrier carries a cleaning toner image for cleaning the transfer material carrier, and the second mode is executed in the cleaning process, and the peripheral speed of the image carrier and the An image forming apparatus is provided in which a difference in peripheral speed from a peripheral speed of the transfer material carrier is different between the first mode and the second mode.

According to another aspect of the present invention, a movable image bearing member for bearing a toner image, a movable intermediate transfer member for receiving the toner image on the image bearing member, the intermediate from the image bearing member after transferring a first mode for transferring the toner image on the intermediate transfer member to the transfer material by transferring the toner image to a transfer member, the toner image on said image bearing member to the intermediate transfer member, transfer A second mode for reversely transferring the toner image on the intermediate transfer body onto the image carrier,
A cleaning step for transferring a cleaning toner image for cleaning the intermediate transfer member from the image carrier onto the intermediate transfer member, and when the second mode is executed in the cleaning step, wherein before the intermediate transfer member the toner image transferred onto the reverse transcription on the image bearing member, an image forming apparatus characterized by passing between the image carrier and the intermediate transfer member Ru is provided .

According to another aspect of the present invention, a movable image carrier that carries a toner image, a transfer material carrier that carries a transfer material and is movable, and the image carrier on the transfer material on the transfer material carrier A first mode for transferring the toner image on the body, a second mode for transferring the toner image on the image carrier onto the transfer material carrier, and transfer from the image carrier by the second mode. A third mode in which the toner image on the transferred transfer material carrier is reversely transferred onto the image carrier;
A cleaning step of transferring a cleaning toner image for cleaning the transfer material carrier from the image carrier onto the transfer material carrier; in the cleaning step, the second mode and the third mode; When the mode is executed, the toner image transferred onto the transfer material carrier passes between the transfer material carrier and the image carrier before the third mode. An image forming apparatus is provided.

  According to the present invention, foreign matters such as paper dust adhering to the transfer material carrier or the intermediate transfer member can be effectively removed. In addition, as one of the operational effects obtained by the present invention, it is possible to suppress the adhesion of dirt to the transfer material carrier or intermediate transfer member without adding a special member, and to transfer the image for controlling the image forming conditions. For example, the detection accuracy of the test image formed on the material carrier or the intermediate transfer member can be maintained. In addition, as one of the operational effects obtained by the present invention, it is possible to prevent stain adhesion to the transfer material carrier or intermediate transfer body without adding a special member, and to suppress image spots and wrinkles of the transfer material. It can be mentioned.

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

Example 1
[Overall Configuration and Operation of Image Forming Apparatus]
First, the overall configuration and operation of the image forming apparatus of this embodiment will be described with reference to FIG. FIG. 1 shows a schematic cross section of a main part of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 according to the present exemplary embodiment includes an electrophotographic method according to an image information signal from an external device such as a personal computer, a document reading device, or a digital camera connected to the image forming apparatus main body (apparatus main body). Is a full color laser beam printer that can form a full color image on a transfer material. Further, the image forming apparatus 100 of the present embodiment employs a tandem method that is particularly excellent in terms of high speed.

  The image forming apparatus 100 includes, as a plurality of image forming units, a first image forming station PM, a second image forming station PC, a third image forming station PC for forming toner images of magenta, cyan, yellow, and black, respectively. An image forming station PY and a fourth image forming station PK are provided independently. The transfer material 1 is carried and conveyed by a conveyance belt (electrostatic adsorption conveyance belt) 7 as a transfer material carrier, and sequentially passes through each image forming station. For example, during the formation of a full-color image, each color toner image is transferred onto the transfer material 1 every time the transfer material 1 passes through each image forming station. Thereby, a full color image is formed on the transfer material 1.

  Although described in detail below, in this embodiment, the basic configuration and operation of each image forming station are substantially the same except that the type of toner is different. Therefore, in the following, when there is no need to distinguish between them, the subscripts M, C, Y, and K given to the reference numerals in order to indicate that they are elements for any color will be omitted and described collectively.

  The image forming station P is provided with a drum-type electrophotographic photosensitive member that can be rotated as an image carrier, that is, a photosensitive drum 9. A charging roller 10 as charging means for charging the photosensitive drum 9 along the outer periphery of the photosensitive drum 9, a developing device 12 as developing means for developing an electrostatic image formed on the photosensitive drum 9, and toner on the photosensitive drum 9. A cleaner 14 is disposed as a cleaning means for removing water. Furthermore, each image forming station P is provided with a laser exposure optical system (laser scanner) 11 as exposure means (image writing device) so that the photosensitive drum 9 can be irradiated with a laser modulated in accordance with image information. It has been. In this embodiment, the charging roller 10, the laser exposure optical system 11, and the developing device 12 constitute an image forming unit 8 that forms a toner image on the photosensitive drum 9.

  The developing device 12 includes a toner storage container (container) 12 b that stores toner, and a developer carrier (developing roller) 12 a that supports and conveys the toner in the container 12 b and supplies the toner to the photosensitive drum 9. In the present embodiment, negatively chargeable toner is stored in the developing device 12 as a developer. Then, a developing bias is applied to the developing roller 12a from a developing bias power source (not shown) as a developing bias output means, so that the developing roller 12a is opposed to the developing roller 12a and the photosensitive drum 9 (developing region). The upper toner is transferred onto the photosensitive drum 9, and the electrostatic image is visualized as toner.

  The cleaner 14 includes a cleaning blade 14 a as a cleaning member that contacts the photosensitive drum 9, and a waste toner container 14 b that stores toner and the like removed from the photosensitive drum 9 by the cleaning blade 14 b.

  A conveying belt 7 is disposed as a transfer member that carries the toner image transferred from the photosensitive drum 9 directly or via the transfer material 1 so as to face the photosensitive drum 9 of each image forming station P. The conveyor belt 7 is stretched by two rollers, a driving roller 5 and a driven roller 6, as a plurality of rollers. The transport belt 7 is rotated (rotated) in the direction indicated by the arrow in the drawing when the driving force is transmitted to the driving roller 5. The image forming stations P are arranged in a line along the moving direction of the conveyor belt 7.

  In each image forming station P, a transfer roller 13 as a transfer unit is disposed on the inner peripheral surface side of the transport belt 1. The transfer roller 13 presses the conveyance belt 7 toward the photosensitive drum 9 to form a transfer portion (transfer nip) N where the photosensitive drum 9 and the conveyance belt 7 are in contact with each other. The transfer roller 13 moves the toner between the photosensitive drum 9 and the transfer body 7 in the transfer portion N when a bias is applied.

  For example, at the time of a full-color image forming operation, first, in the first image forming station PM which is a magenta image forming station, a peripheral speed (surface moving speed: corresponding to the process speed of the image forming apparatus 100) 180 mm in the direction of the arrow. The photosensitive drum 9 rotated at / s is uniformly charged to −500 V by the charging roller 10. At this time, a charging bias is applied to the charging roller 10 from a charging bias power source (not shown) as a charging bias output means. Next, an electrostatic image (latent image) corresponding to a magenta image is formed on the surface of the photosensitive drum 9 by scanning light from the laser exposure optical system 11. The potential of the latent image portion formed by exposure with the scanning light is about −200V. On the other hand, a fixed amount of magenta toner charged with a negative polarity is supplied onto the developing roller 12a, and a developing bias is applied to the developing roller 12a. In this state, by setting the developing bias to an appropriate value between the charging potential and the exposure portion potential, the toner can be selectively attached to the latent image on the photosensitive drum 9 and the electrostatic image can be developed.

  The magenta toner image formed on the photosensitive drum 9 in this manner is adsorbed and held on the conveyor belt 7 when the conveyor belt 7 is driven at the same peripheral speed (surface movement speed) as the peripheral speed of the photosensitive drum 9. Then, it is electrostatically transferred onto the transfer material 1 conveyed at the same speed as the photosensitive drum 9. At this time, the transfer roller 13 is applied with a transfer bias of +1500 V output from a transfer bias power source 23 serving as a transfer bias output means and having a polarity opposite to the normal charging polarity of the toner (negative polarity in this embodiment). Is done. In other words, the transfer bias power supply 23 outputs a bias having a polarity opposite to the normal charging polarity of the toner, so that the toner charged to a predetermined polarity (negative polarity in this embodiment) is transferred from the photosensitive drum 9 to the conveying belt 7. An electric field is formed in the transfer portion N in the direction toward the front. Incidentally, the toner that is not transferred onto the transfer material 1 but remains on the photosensitive drum 9 is scraped off by the cleaning blade 14a and collected in the waste toner container 14b.

  The above process is performed in the same way in the second, third, and fourth image forming stations PC, PY, and PK, which are cyan, yellow, and black image forming stations, and a full color toner image is formed on the transfer material 1. Is done. Thereafter, the transfer material 1 is separated from the conveyance belt 7 and conveyed to a fixing device 15 as a fixing unit. The toner image is melted and fixed on the transfer material 1 by the fixing device 15 and becomes an output image of the device. The transfer material 1 is then discharged out of the apparatus.

As the transport belt 7, a resin material which is less likely to be stretched or deformed due to long-term use and which is difficult to tear can be used by adjusting the resistance. In this example, a polyimide resin single layer belt having a thickness of 100 μm and having a volume resistance adjusted to about 1.0 × 10 ¹¹ Ωcm by carbon particle dispersion was used. In addition to this, for example, a resin film such as PVdF (polyvinylidene fluoride resin), ETFE (tetrafluoroethylene-ethylene copolymer resin), PET (polyethylene terephthalate), polycarbonate, or the like may be used as the material of the conveyance belt 7. it can. Alternatively, as the transport belt 7, a rubber base layer having a thickness of about 0.5 to 2 mm, for example, EPDM, is coated with, for example, urethane rubber dispersed with a fluorine resin such as PTFE. A layer belt or the like can also be used. Further, as a method for adjusting the resistance of the belt material, a method using dispersion of an ion conductive material may be used.

  Adsorption of the transfer material 1 onto the conveyance belt 7 is assisted by an adsorption roller 3 as an adsorption assist unit that contacts the conveyance belt 7 at a position facing the driven roller 6. That is, the transfer material 1 such as paper supplied from a paper feeding mechanism (not shown) passes through the contact portion (suction nip) between the suction roller 3 and the transport belt 7 when introduced to the transport belt 7. A bias of +1500 V is applied to the suction roller 3 from a suction bias power source (not shown) as suction bias output means. By this electric field and charge supply by the bias, electrostatic polarization between the transfer material 1 and the transport belt 7 is promoted, and the transfer material 1 is attracted to the transport belt 7.

  The image forming apparatus 100 according to this embodiment forms a test image on the conveyance belt 7 and an image density control mechanism that adjusts the image forming condition according to the result of detecting the test image by the optical sensor 30 serving as a detection unit. And a color misregistration adjustment mechanism that adjusts the image formation timing according to the result of detecting the test image by the optical sensor 30. Hereinafter, the image density control mechanism and the color misregistration adjustment mechanism are collectively referred to as a calibration mechanism. In the present embodiment, the optical sensor 30 is disposed so as to face the surface of the conveyor belt 7 wound around the driven roller 6. As will be described in detail later, in this embodiment, the optical sensor 30 is located in the vicinity of both ends of the conveyor belt 7 in a direction intersecting (substantially orthogonal) to the moving direction of the conveyor belt 7 (hereinafter referred to as “thrust direction”). One each is provided. The optical sensor 30 detects a test image formed on the conveyor belt 7 when the calibration mechanism is executed. The structure of the optical sensor 30 is the same as the conventional one described with reference to FIG.

[Transfer cleaning process]
Next, the transfer body cleaning process (belt cleaning operation), which is the most characteristic feature of this embodiment, will be described.

  The image forming apparatus 100 according to the present exemplary embodiment performs the following processing at a timing other than the time of normal printing image formation for transferring and outputting a toner image to the transfer material 1 and the execution of the calibration mechanism (that is, at the time of test image formation). A belt cleaning mode in which the belt cleaning operation described in (1) is performed is provided. In the belt cleaning operation, a predetermined toner image for cleaning the transport belt 7 (hereinafter referred to as “cleaning toner image”) T (FIG. 3) is transferred onto the transport belt 7 and the dirt is removed from the toner of the cleaning toner image T. At the same time, it is reversely transferred to the photosensitive drum 9 and collected.

The basic operation of the belt cleaning operation in this embodiment is as follows.
(1) The photosensitive drum 9, the developing device 12, and the conveying belt 7 are driven in the same way as when forming an image for normal printing, and charging, developing, and transfer biases are also applied.
(2) At each image forming station P, a cleaning toner image T is formed on the photosensitive drum 9 by the same process as that for normal image formation for printing.
(3) A transfer bias of +1500 V output from the transfer bias power supply 23 and having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the transfer roller 13. The transfer bias power source 23 outputs a bias having a polarity opposite to the normal charging polarity of the toner, so that the toner charged to a predetermined polarity (negative polarity in this embodiment) is directed from the photosensitive drum 9 toward the transport belt 7. An electric field in the direction to be displaced is formed at the transfer portion N. As a result, the cleaning toner image T is directly transferred onto the transport belt 7.
(4) After one rotation of the conveying belt 7 from the start of the transfer of the cleaning toner image T, the toner on the conveying belt 7 is reversely transferred to the photosensitive drum 9 simultaneously with foreign matters such as paper dust and dirt.
(5) The toner and foreign matter returned on the photosensitive drum 9 are collected by the cleaner 14.

  FIG. 3 shows the transport belt 7 on which the cleaning toner image T has been transferred developed. In the process (2), the cleaning toner image T contacts at least the region on the conveyance belt 7 facing the optical sensor 30 in the thrust direction, that is, the detection region d of the optical sensor 30 on the conveyance belt 7. It is preferably formed in a region on the photosensitive drum 9 including the region. Thereby, the detection accuracy of the optical sensor 30 can be maintained satisfactorily. Further, the width t in the thrust direction of the cleaning toner image T is preferably wider than the test image so that the wide area of the area that contributes to image formation on the conveyor belt 7 can be cleaned. It is more preferable that the maximum image forming width (g) of the apparatus be greater than or equal to g. Naturally, the width t of the cleaning toner image T in the thrust direction is equal to or smaller than the width w of the transport belt 7 in the same direction.

  The length l of the cleaning toner image in the moving direction of the conveying belt 7 is set so that the cleaning toner image T is in contact with the entire area in the moving direction of the conveying belt 7 by one or more belt cleaning operations. It is preferable to do.

  In this embodiment, the width t in the thrust direction of the cleaning toner image T is 210 mm, which is the same as the maximum width g of image formation in the same direction. On the other hand, the length l of the cleaning toner image T in the circumferential direction (moving direction) of the conveying belt 7 was 180 mm. Further, the cleaning toner image T was a solid image (image of the maximum density level).

  In this embodiment, in order to consume the toners of the four image forming stations P in a balanced manner and substantially uniformly, the sizes of the cleaning toner images T are the same for all four colors. Further, in this embodiment, the formation timing of the cleaning toner image T in each image forming station P is adjusted so that the cleaning toner images T of the respective colors do not overlap on the conveyance belt 7. Accordingly, the cleaning toner image T can be formed in a wider range in the circumferential direction of the transport belt 7.

  In this embodiment, the circumferential length of the conveying belt 7 is 720 mm, and the cleaning toner images T for the above four colors (Tm, Tc, Ty, Tk in FIG. 3) are arranged without being overlapped, so that one belt is formed. In the cleaning operation, it is possible to form a toner image for one rotation of the conveyor belt on the conveyor belt 7. That is, when the number of image forming stations P is n and the circumferential length of the conveyance belt 7 is L, in this embodiment, the circumferential length l of the cleaning toner image of each color formed on the conveyance belt 7 is: L / n.

  As will be described later, it is preferable that the cleaning toner images T of the respective colors are not overlapped on the conveying belt 7 in terms of effective use of the toner. However, the present invention is not limited to this. For example, in order to reliably form the cleaning toner image T for one round in the circumferential direction of the transport belt 7 by one belt cleaning operation, The circumferential length l of the cleaning toner image is set to L / n or more, and a predetermined range of the leading end and the trailing end of the adjacent cleaning toner images T of different colors is overlapped in the circumferential direction of the transport belt 7. Good.

  In the steps (4) to (5), in this embodiment, the toner and foreign matter on the conveyor belt 7 are reversely transferred to the photosensitive drum 9 and collected as follows. The charged potential of the photosensitive drum 9 is kept at −500V. Then, at the most upstream image forming station PM and the third image forming station PY in the moving direction of the transport belt 7, the normal charging polarity of the toner output from the transfer bias power source 23 to the transfer roller 13 (this embodiment) In the example, a bias (reverse bias) of −2500 V having the same polarity as the negative polarity is applied. On the other hand, in the second and fourth image forming stations PC and PK from the upstream in the moving direction of the conveying belt 7, the normal charging polarity of the toner output from the transfer bias power source 23 to the transfer roller 13 (in this embodiment). A bias of +1500 V having a polarity opposite to that of (negative polarity) is applied.

  As a result, in the first and third image forming stations PM and PY, a bias having the same polarity as the normal charging polarity of the toner is output from the transfer bias power source 23, so that a large amount of toner or foreign matter charged to a negative polarity is output. Is formed in the transfer portion N so that the toner and foreign matter are transferred to the photosensitive drum 9 and collected. On the other hand, in the second and fourth stations PC and PK, the transfer bias power supply outputs a bias having a polarity opposite to the normal charging polarity of the toner, so that the toner or foreign matter charged to the positive polarity is conveyed to the transport belt 7. Then, an electric field is formed in the transfer portion N in a direction directed to the photosensitive drum 9, and the toner and foreign matter are transferred to the photosensitive drum 9 and collected.

  As described above, in this embodiment, when the cleaning toner image T transferred to the conveyance belt 7 is reversely transferred to the photosensitive drum 1, the photosensitive drum 9 and the conveyance belt of the first and third image forming stations PM and PY are used. The direction of the electric field formed between the photosensitive drum 9 and the conveying belt 7 of the second and fourth image forming stations PC and PK is reversed.

  By the bias application method as described above, the toner and foreign matter on the conveyor belt 7 can be efficiently reversely transferred to the photosensitive drum 9 and collected. However, the polarity of the bias applied to the transfer roller 13 of each image forming station P in the step (4) is not limited to an aspect in which the polarity is alternately reversed along the moving direction of the conveying belt 7. Absent. If desired, in all the image forming stations P, a bias having the same polarity, in particular, a reverse polarity to the normal charging polarity of the toner may be applied to the transfer roller 13. Further, two or more image forming stations P to which a bias having the same polarity is applied to the transfer roller 13 may be continuously arranged. However, the image forming station P having different bias polarities applied to the transfer roller 13 is capable of forming a plurality of images so that toners and foreign matters having different polarities can be effectively transferred back from the conveying belt 7 to the photosensitive drum 9. Preferably at least one of the stations is included. Further, for the step (4), the conveyance belt 7 is rotated a plurality of times, and the polarity of the bias applied to the transfer roller 13 in one image forming station P is changed during a plurality of rotations ( For example, the polarity can be switched alternately between two rounds).

  Next, a mechanism for removing dirt such as paper dust on the conveyor belt 7 by executing the belt cleaning operation as described above will be described.

  First, when the cleaning toner image (solid image) T is transferred onto the conveyance belt 7, the toner adheres to foreign matters such as paper dust and dirt adhered to the conveyance belt 7 by the pressure of the transfer portion N. And get mixed up. In particular, in this embodiment, since there are four image forming stations P, the foreign matter on the conveyor belt 7 passes through the four transfer portions N until collection, and mixing by pressurization is repeated each time.

  In addition, calcium carbonate, which is one of the components of paper powder, tends to be positively charged, and attracts each other with negative polarity toner particles. In such a mixed state, when the toner is reversely transferred to the photosensitive drum 9 after one round of the conveying belt, pressure is applied again to promote the above mixing. Then, paper dust and dirt mixed with the toner are collected on the photosensitive drum 9 together with the toner and removed from the conveying belt 7.

  The timing of performing the belt cleaning operation as described above is arbitrary, but in this embodiment, it is 1 every time a normal image forming operation for printing is performed 200 times in accordance with the timing of discharging the deteriorated toner from the developing device 12. I decided to do it once.

  That is, in the image forming station P, if the toner supplied onto the developing roller 12a of the developing device 12 remains undeveloped for a long time, the toner may eventually deteriorate. When the toner deteriorates, its charging characteristics change, and accurate image formation may not be performed. Such a problem is particularly likely to occur when image formation with a low printing rate is repeated. Therefore, conventionally, the toner on the developing roller is forcibly transferred onto the photosensitive drum every predetermined period (for example, the predetermined number of image formations), and the toner is collected by a cleaner that removes the toner on the photosensitive drum. There is an image forming apparatus provided with a developer discharging mechanism. According to the developer discharging mechanism, the toner remaining on the developing roller for a long time can be excluded, and the toner on the developing roller can be refreshed.

  The image forming apparatus 100 of the present embodiment also includes the developer discharge mechanism as described above. Then, the belt cleaning operation is performed in accordance with the timing of the developer discharging operation. That is, all or part of the toner image supplied onto the photosensitive drum 9 in the developer discharging operation is used to form the cleaning toner image T. Thereby, the toner (including deteriorated toner) that is discharged from the developing device 12 and that is originally discarded can be actively used for cleaning the transport belt 7. Therefore, the necessity of consuming normal toner for the belt cleaning operation is reduced, and the toner in the developing device 12 can be used effectively.

  In this embodiment, at the time of the belt cleaning operation of the basic operation as described above, the peripheral speed difference is provided between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the transport belt 7 as described in detail below. The performance of removing dirt on the belt 7 is further improved.

  Here, conventionally, there is a case where a peripheral speed difference is provided between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveying belt 7 during image formation for normal printing. Of course, the peripheral speed difference may not be provided, and the peripheral speed difference may be set to 0%. In this embodiment, the difference in the peripheral speed between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the transport belt 7 is 0% during normal print image formation and test image formation. When this circumferential speed difference is provided, the circumferential speed difference is generally set to 2 to 3%.

  The peripheral speed difference is defined as a value obtained by expressing the difference between the peripheral speed V2 of the conveying belt and the peripheral speed V2 of the photosensitive drum in%, that is, a value obtained by | V2−V1 | / V1 * 100.

  In this embodiment, the peripheral speed difference provided between the photosensitive drum 9 and the conveyor belt 7 during the belt cleaning operation may be 2 to 3% as described above, but preferably a larger peripheral speed difference, That is, a peripheral speed difference of 10 to 400% is provided. If the peripheral speed difference is smaller than this, the effect of providing the peripheral speed difference is weakened. On the other hand, if the peripheral speed difference is larger than this, the surface of the photosensitive drum may be damaged by excessive rubbing. More preferably, a peripheral speed difference of 50% to 200% is provided. As described above, in this embodiment, the peripheral speed difference provided between the photosensitive drum 9 and the conveyance belt 7 during the belt cleaning operation is at least transferred to the transfer material 1 on the conveyance belt 7 during image formation for normal printing. The difference in peripheral speed between the photosensitive drum 9 and the conveyor belt 7 when transferring the toner on the photosensitive drum 9 is made larger.

  That is, in the belt cleaning step, at least the cleaning toner image T formed on the photosensitive drum 9 is transferred to the conveyance belt 7 (that is, the step (3)) and the circumferential speed of the photosensitive drum 9 and the conveyance belt 7. The peripheral speed difference between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the transport belt 7 when the toner on the photosensitive drum 9 is transferred to the transfer material 1 on the transport belt 7 during image formation for normal printing. Different from the peripheral speed difference. Further, the peripheral speed between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveyor belt 7 when the cleaning toner image T on the conveyor belt 7 is reversely transferred onto the photosensitive drum 9 (that is, step (4) above). The difference is the difference in the peripheral speed between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the transport belt 7 when the toner on the photosensitive drum 9 is transferred to the transfer material 1 on the transport belt 7 during image formation for normal printing. Can be different. In this embodiment, at the time of the belt cleaning operation, a circumferential speed difference is provided between the photosensitive drum 9 and the conveying belt 7 in all the image forming stations P during the steps (1) to (5).

  Specifically, in the present embodiment, during the belt cleaning operation, the conveyor belt 7 is driven at a peripheral speed of 180 mm / s, whereas the photosensitive drum 9 is half the peripheral speed of 90 mm / s (peripheral speed difference 100). %). In the belt cleaning operation, since there is no need to worry about the deviation of the formed toner image, such a peripheral speed difference can be provided.

  Thus, in the belt cleaning operation, when the cleaning toner image T is transferred onto the conveyance belt 7, when passing the transfer portion N of the subsequent downstream image forming station P, and from the conveyance belt 7 to the photosensitive drum 9. At each time of reverse transfer of the toner image T for cleaning, the applied pressure and rubbing stress at the transfer portion N act on the mixed layer of toner and foreign matter. As a result, both the toner and the foreign matter are more easily mixed. In addition to this, while the rubbing stress is acting, the toner layer itself acts like an abrasive, so that foreign matters such as paper dust and dirt substances that are stuck on the conveying belt 7 can be peeled off. In particular, when the cleaning toner image T is transferred onto the transport belt 7, the toner is mixed on the transport belt 7 while being mixed with the foreign material.

  In other words, in other words, the image forming apparatus 100 according to the present embodiment transfers the toner on the photosensitive drum 9 to the transfer material 1 on the conveying belt 7 and the toner on the photosensitive drum 9 on the conveying belt 7. A second mode in which the transfer is performed, and the difference in the peripheral speed between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveyor belt 7 is different between the first mode and the second mode. Further, the image forming apparatus 100 has a third mode in which the toner on the conveyance belt 7 is reversely transferred onto the photosensitive drum 9, and the peripheral speed and conveyance of the photosensitive drum 9 at the time of reverse transfer in the third mode. The peripheral speed difference from the peripheral speed of the belt 7 can be made different from the peripheral speed difference when the toner is transferred from the photosensitive drum 9 to the transfer material 1 on the conveying belt 7 in the first mode.

  FIG. 4 shows a schematic control mode of this embodiment. The operation of the image forming apparatus 100 is comprehensively controlled by a controller unit 50 provided in the apparatus main body. The controller unit 50 includes a calculation unit, a storage unit, and a control unit. The controller unit 50 controls a normal image forming operation, an operation of a calibration mechanism, and the like according to a program stored in the storage unit, and the belt cleaning operation as described above. To control. The controller 50 controls the formation timing of each image forming station P cleaning toner image in accordance with the detection result of a belt position detection means (not shown) that detects the position on the conveyance belt 7. In the present embodiment, the controller unit 50 has a function as a bias changing unit that changes the value and polarity of the output bias of the transfer bias power source 23 in accordance with the belt cleaning operation process.

  Further, as shown in FIG. 4, the controller unit 50 controls a photosensitive member driving motor 51 as a driving unit for the photosensitive drum 9 and a belt driving motor 52 as a driving unit for the conveying belt 7, respectively. It has a function as a peripheral speed difference changing means for changing the peripheral speed difference between the photosensitive drum 9 and the conveyance belt 7 during image formation (further, when the calibration mechanism is executed) and during a belt cleaning operation.

The effect by a present Example was confirmed. Plain paper (Xerox 4024 75 g / m ² paper) was continuously fed in a low-temperature and low-humidity environment with an air temperature of 15 ° and a humidity of 10% RH, and a belt cleaning operation was performed once every 200 sheets. Here, for the purpose of comparison, when the circumferential speed difference is provided between the photosensitive drum 9 and the conveyor belt 7 during the cleaning operation according to the present embodiment (Example 1), and when the circumferential speed difference is not provided (Comparison) Tests were conducted for both Example 1). And the transition of the regular reflection light quantity of the surface of the conveyance belt 7 at the time of continuing paper passing was observed. Further, for the purpose of comparison, a similar paper passing test was performed on a conventional image forming apparatus (conventional example) that does not perform a belt cleaning operation. The image forming apparatus of the conventional example is substantially the same as the image forming apparatus of the present embodiment except that the belt cleaning operation is not performed. The results are shown in FIG.

  In FIG. 2, the horizontal axis represents the number of sheets to be passed and the vertical axis represents the amount of reflected light. The amount of reflected light is shown as the output voltage value of the optical sensor 30 (that is, the photodiode 302 which is a light receiving element) provided for detecting the test image. Here, the larger the numerical value of this output voltage, the greater the amount of specular reflection. The transition of the relationship between the number of sheets passed and the amount of reflected light in the conventional example is indicated by a broken line, the transition in Comparative Example 1 is indicated by a one-dot chain line, and the transition in the present embodiment is indicated by a solid line.

  As can be seen from FIG. 2, in the initial state, the output voltage value is 2.2 V in any of Example 1, Comparative Example 1, and the conventional example, but regular reflection decreases due to contamination of the conveyor belt 7 as well as durability. Come. In the conventional example, the amount of reflected light (voltage value) decreases to 0.6 V, and problems occur in density control and color misregistration control after 20000 sheets are passed. On the other hand, in Comparative Example 1, it can be seen that the amount of reflected light is stable at about 1.5V. Further, in Example 1, the amount of specular reflection (voltage value) after passing through 50000 sheets was 1.6 V, and it was possible to confirm the effect of preventing dirt further exceeding that of Comparative Example 1. In Example 1, there was no problem in density control or color misregistration control even when 50,000 sheets were passed.

  As described above, according to this embodiment, the toner image is directly transferred onto the conveyance belt 7 during the belt cleaning operation, and the dirt is reversely transferred to the photosensitive drum 9 together with the toner image and collected. Further, during the belt cleaning operation, at least the toner image is transferred onto the conveyance belt 7, and further, the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveyance belt 7 when the toner image is reversely transferred to the photosensitive drum 9. The peripheral speed difference is made different from the peripheral speed difference between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveyor belt 7 when an image for normal printing is formed. Thereby, dirt, such as paper dust, can be removed from the conveyance belt 7 without adding a special member. Accordingly, it is possible to prevent density control and color misregistration adjustment from being caused by dirt on the conveyor belt 7, occurrence of transfer spots, and wrinkles of the transfer material 1. In addition, it is not necessary to provide a dedicated waste toner container for the transport belt 7, and there is no need for a space in the apparatus for the waste toner container or for replacing the waste toner container. In this embodiment, the cleaning toner image T formed during the belt cleaning operation is prevented from overlapping on the conveyor belt 7 as much as possible, so that a smaller amount of toner is used to clean a wider area on the conveyor belt 7. A toner image T can be formed. As a result, it is possible to remove dirt on the conveyor belt 7 by effectively using the toner.

  In this embodiment, the cleaning toner image T for one rotation of the transport belt 7 is formed by one belt cleaning operation. However, the present invention is not limited to this. In other words, the cleaning toner image T for the entire circumference of the conveying belt 7 is not formed by one belt cleaning operation, but is divided into several belt cleaning operations that are periodically performed, and for one circumference of the conveying belt 7. The cleaning toner image T may be formed. For example, in a plurality of belt cleaning operations, the cleaning toner image T can be formed at a position on the transport belt 7 where the location is changed each time. Alternatively, in a plurality of belt cleaning operations, a toner image may be formed at random positions on the conveyor belt 7 so that the entire circumference of the conveyor belt 7 is finally cleaned. In this embodiment, the cleaning toner images T for all the colors are formed by all the image forming stations P by one belt cleaning operation. However, the present invention is not limited to this embodiment. For example, among a plurality of image forming stations provided in the apparatus, only one or a part of a plurality of colors of cleaning toner images T is formed for each belt cleaning operation, and all colors are formed by a plurality of belt cleaning operations. A toner image for cleaning may be formed. Further, the cleaning toner image T of any color may not be formed. The cleaning toner image of any color may be brought into contact with the entire area in the moving direction of the transport belt 7 by one or a plurality of belt cleaning operations.

  In the present embodiment, the cleaning toner image T formed on the conveying belt 7 is formed so as not to overlap between the respective colors, but conversely, a plurality of color toner images may be formed so as to be positively superimposed. good. In this case, since the amount of toner per unit area of the cleaning toner image T formed on the transport belt 7 is increased, the effect of taking dirt into the toner layer is enhanced. Therefore, there is an effect that the dirt removal capability per belt cleaning operation is increased. In particular, in the thrust direction, there may be a place where contamination is likely to occur (locally) due to the configuration of the apparatus, such as a position where a member that contacts the transfer material 1 such as a conveying unit is disposed. For example, in the thrust direction, paper dust is likely to be generated at a position on the conveyor belt 7 corresponding to the paper feed roller position. In such a case, at the time of the belt cleaning operation, the cleaning effect can be concentrated by forming a plurality of color toner images on the portion.

  In this embodiment, the peripheral speed difference is provided between the photosensitive drum 9 and the conveyor belt 7 by making the peripheral speed of the conveyor belt 7 faster than the peripheral speed of the photosensitive drum 9, but this is contrary to this embodiment. In addition, a peripheral speed difference may be provided between the photosensitive drum 9 and the transport belt 7 by making the peripheral speed of the transport belt 7 slower than the peripheral speed of the photosensitive drum 9. However, as in this embodiment, driving the conveyor belt 7 faster than the photosensitive drum 9 can clean the surface of the conveyor belt 7 over a wide range with a small amount of toner, and also for cleaning the conveyor belt 7. This is advantageous in that the time required can be shortened.

Example 2
Next, still another embodiment of the present invention will be described. The basic configuration of the image forming apparatus of this embodiment is the same as that of the first embodiment. Accordingly, elements having substantially the same or corresponding functions as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In this embodiment, during the belt cleaning operation, a circumferential speed difference is provided between the photosensitive drum 9 and the conveying belt 7 as in the first embodiment, while the cleaning toner image T formed on the photosensitive drum 9 is transferred to the conveying belt. 7 is different from the first embodiment in that no image is transferred onto the upper surface. The peripheral speed difference between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the transport belt 7 during the belt cleaning operation is similar to that of the first embodiment, and the peripheral speed and transport of the photosensitive drum 9 during normal printing image formation. Different from the peripheral speed difference with the peripheral speed of the belt 7.

FIG. 5 shows a state of one image forming station P in which a belt cleaning operation is being performed according to the present embodiment. The procedure of the belt cleaning operation in the present embodiment is as follows.
(1) The conveyor belt 7 is driven at a peripheral speed of 180 mm / s, while the photosensitive drum 9 is driven at a peripheral speed of 90 mm / s.
(2) A cleaning toner image T is formed on the photosensitive drum 9 in the same manner as in the first embodiment with a peripheral speed difference provided between the photosensitive drum 9 and the conveyor belt 7. At this time, the bias (transfer bias) applied to the transfer roller 13 is set to OFF (0 V), or −2000 V, which is the same polarity as the normal charging polarity of the toner (negative polarity in this embodiment). Is applied. In other words, the electric field in the direction toward the conveyance belt 7 does not act on the toner on the photosensitive drum 9 (that is, the conveyance belt 7 and the photosensitive drum 9 are conveyed during normal printing image formation). An electric field in the direction opposite to that when transferring the toner on the photosensitive drum 9 to the transfer material 1 on the belt 7 is formed).
(3) In this state, the cleaning toner image T formed on the photosensitive drum 9 is passed through the transfer portion N. As a result, the cleaning toner image T on the photosensitive drum 9 is hardly transferred onto the conveyance belt 7 and passes through the transfer portion N with a circumferential speed difference between the toner image T and the conveyance belt 7. When the cleaning toner image T passes through the transfer portion N, the toner rubs against the foreign matter on the transport belt 7 like an abrasive, and the foreign matter on the transport belt 7 is scraped off.
(4) The toner that has passed through the transfer portion N and the foreign matter scraped off from the transport belt 7 are collected by the cleaner 14 of the photosensitive drum 9.

  Note that, in order to clean the toner that has moved a small amount on the conveyor belt 7 and foreign matter that has not been scraped off, it is the same as the toner collecting process from the conveyor belt 7 to the photosensitive drum 9 in the first embodiment. Then, the operation of collecting these deposits from the conveyor belt 7 may be continued.

  In other words, in this embodiment, the image forming apparatus 100 transfers the toner on the photosensitive drum 9 to the transfer material 1 on the conveying belt 7 and the toner on the photosensitive drum 9 on the transfer material 1 or the conveying belt. A second mode for passing between the photosensitive drum 9 and the conveying belt 7 without transferring to the photosensitive drum 9, and the peripheral speed difference between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveying belt 7 is The first mode is different from the second mode.

  According to the present embodiment, since a peripheral speed difference is provided between the toner layer accompanying the surface of the photosensitive drum 9 and foreign matters such as dirt on the transport belt 7, the frictional stress for peeling off the foreign matters becomes stronger. . Thereby, in particular, the ability to remove the foreign matter that has been strongly adhered to the conveyor belt 7 is excellent. Further, by not moving a large amount of toner on the conveyance belt 7, it is possible to reduce the load in the process of collecting the toner moved on the conveyance belt 7, or to omit the process itself.

  Further, by applying a negative bias having the same polarity as the normal charging polarity of the toner to the transfer roller 13 in the belt cleaning operation of this embodiment, the following effects are accompanied.

  That is, when the cleaning toner image T passes through the transfer portion N or immediately before it, a negative-polarity bias is applied to the transfer roller 13 so that the charge control agent attached to the toner or fluidity imparting is applied. Of the external additives such as an agent, those having a polarity opposite to the charging polarity of the toner move a lot on the conveying belt 7. As a result, in the transfer portion N, these additives are interposed between the cleaning toner image T and the foreign matter on the conveying belt 7. As the additive, a hard substance such as silica or metal oxide is used. By interposing these substances, the effect of polishing and rubbing off foreign matter on the conveyor belt 7 during cleaning becomes higher.

  Further, when the cleaning toner image T that has passed through the transfer portion N is collected on the photosensitive drum 9, the following effects can be obtained. That is, when an image for normal printing is formed, the toner particles are transferred to the transfer material 1 by applying a positive transfer bias having a polarity opposite to the normal charging polarity of the toner. On the other hand, the proportion of the toner external additive remaining on the photosensitive drum 9 is higher. If the cleaning of the photosensitive drum 9 is repeated in this state, an external additive may adhere to the cleaning blade 14a of the cleaner 14 of the photosensitive drum 9 and grow, and a streak-like cleaning defect may eventually occur.

  In the belt cleaning operation of this embodiment, when a negative polarity bias having the same polarity as the toner charging polarity is applied to the transfer roller 13, an external additive is applied to the photosensitive drum 9 after passing through the transfer portion N. Is moved onto the conveyor belt 7 to form a large amount of toner image in which the amount of the external additive is reduced. In this state, when the toner is collected from the photosensitive drum 9 by the cleaner 14, a large amount of toner with a small amount of additive passes through the cleaning blade 14a at a time. Then, the additive adhering to the cleaning blade 14a is removed by the momentum of the toner flow. As a result, poor cleaning of the photosensitive drum 9 can be prevented.

  The control mode of the present embodiment is substantially the same as that of the first embodiment. In the present embodiment, the bias changing means also serving as the controller unit 50 can control the transfer bias power source 23 during the belt cleaning operation to turn off the bias application, that is, to be in the grounded state.

  In this embodiment, the area of the cleaning toner image T formed on the photosensitive drum 9 can be the same as that described in the first embodiment.

  More specifically, in this embodiment, the width t in the thrust direction of the cleaning toner image T is 210 mm, which is the same as the maximum width of image formation, as in the first embodiment. Further, in order to prevent the cleaning areas on the conveying belts by the image forming stations P from overlapping, as in the first embodiment, the number of the image forming stations P is n and the circumferential length of the conveying belt 7 is L. Adjustment of the formation timing of the toner image T for cleaning on the photosensitive drum 9 in each image forming station P, where L / n is the length of the area on the conveying belt where each image forming station P passes the toner image and performs cleaning. Went.

  By doing so, in this embodiment, it is possible to perform cleaning for one rotation of the conveyor belt 7 by one belt cleaning operation. However, as described above, it is divided into several belt cleaning operations performed periodically, for example, by cleaning the position where the place is changed each time, or by cleaning the random position on the transport belt 7, Finally, cleaning for the entire circumference of the conveyor belt may be performed. In this embodiment, the cleaning area on the conveyor belt 7 is not overlapped between the image forming stations P. However, as described above, conversely, the cleaning on the conveyor belt 7 is performed between the plurality of image forming stations P. The cleaning effect per time can be concentrated and enhanced by overlapping the regions.

  Similarly to the first embodiment, in this embodiment, the peripheral speed difference is provided between the photosensitive drum 9 and the conveyor belt 7 by making the peripheral speed of the conveyor belt 7 faster than the peripheral speed of the photosensitive drum 9. Contrary to the present embodiment, the peripheral speed difference of the conveyor belt 7 may be provided between the photosensitive drum 9 and the conveyor belt 7 by making the peripheral speed of the conveyor belt 7 slower than the peripheral speed of the photosensitive drum 9.

Example 3
Next, still another embodiment of the present invention will be described. The basic configuration of the image forming apparatus of this embodiment is the same as that of the first embodiment. Accordingly, elements having substantially the same or corresponding functions as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In this embodiment, in the belt cleaning operation, after the cleaning toner image T is transferred onto the conveying belt 7, the cleaning toner image T is reversely transferred onto the photosensitive drum 9 and collected until the conveying belt 7 is recovered. The embodiment is different from the first embodiment in that it is idled at least once.

Specifically, the procedure of the belt cleaning operation in the present embodiment is as follows.
(1) In the same manner as in the first embodiment, the photosensitive drum 9, the developing device 12, and the conveying belt 7 are driven, and charging, developing, and transfer biases are applied.
(2) In the same manner as in the first embodiment, a cleaning toner image T is formed on the photosensitive drum 9 at each image forming station P in the same manner as a normal image forming process.
(3) In the same manner as in the first embodiment, a transfer bias of +1500 V having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied from the transfer bias power source 23 to the transfer roller 13.
(4) Next, in this embodiment, an operation is added in which the conveyor belt 7 is idled for one rotation or more (one rotation in this embodiment). In the idling rotation of the conveyor belt 7, the bias applied from the transfer bias power source 23 to the transfer roller 13 is maintained at +1500 V, which is a polarity opposite to the normal charging polarity of the toner. That is, an electric field in the direction toward the conveyance belt 7 is applied to the toner on the conveyance belt 7 in the transfer unit N (that is, a normal print is provided between the conveyance belt 7 and the photosensitive drum 9). When the image is formed, an electric field is formed in the same direction as when the toner on the photosensitive drum 9 is transferred to the transfer material 1 on the conveyor belt 7.
(5) After completion of the idling rotation, the toner on the conveyor belt 7 is reversely transferred to the photoconductor 9 simultaneously with foreign matters such as paper dust and dirt substances in the same manner as in the first embodiment.
(6) The toner and foreign matters returned on the photosensitive drum 9 are collected by a cleaner.

  In the present embodiment, as in the first embodiment, at least the toner image is transferred onto the conveyance belt 7 during the belt cleaning operation, and further, the photosensitive drum is used when the toner image is reversely transferred to the photosensitive drum 9. 9 is made different from the peripheral speed difference between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveyor belt 7 when an image for normal printing is formed. Further, in this embodiment, even when the conveyor belt 7 is idling, the peripheral speed difference between the photosensitive drum 9 and the conveyor belt 7 is determined when the toner image is transferred onto the conveyor belt 7 or the toner image is transferred to the photosensitive drum 9. Similarly to the reverse transfer to the reverse, the difference in the peripheral speed between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the conveying belt 7 when an image for normal printing is formed can be made different.

  In other words, in other words, the image forming apparatus 100 according to the present embodiment transfers the toner on the photosensitive drum 9 to the transfer material 1 on the conveying belt 7 and the toner on the photosensitive drum 9 on the conveying belt 7. A second mode in which the toner is transferred onto the photosensitive drum 9, and a third mode in which the toner on the conveyor belt 7 is reversely transferred onto the photosensitive drum 9, and before the third mode, The transferred toner passes between the conveyance belt 7 and the photosensitive drum 9. The difference in the peripheral speed between the peripheral speed of the photosensitive drum 9 and the peripheral speed of the transport belt 7 is different between the first mode and the second mode. Further, the peripheral speed of the photosensitive drum 9 and the peripheral speed of the transport belt 7 are different. The peripheral speed difference from the speed is made different between the peripheral speed difference when the toner transferred on the transport belt 7 passes between the transport belt 7 and the photosensitive drum 9 and the peripheral speed difference in the first mode. Can do.

  By such an operation, in step (4), the negative polarity toner image can be passed through the transfer portion N of each image forming station P while being held on the conveying belt 7. Accordingly, the toner layer on the transport belt 7 can receive the applied pressure and rubbing force at the transfer portion N more times. That is, mixing of toner and dirt such as paper dust proceeds, and the cleaning effect on the conveyor belt 7 can be further enhanced. Further, by providing a peripheral speed difference between the photosensitive drum 9 and the conveyor belt 7 when the cleaning toner image T passes through the transfer portion N, dirt such as paper dust on the conveyor belt 7 can be more effectively removed. Can be removed.

Example 4
Next, still another embodiment of the present invention will be described. The basic configuration of the image forming apparatus of this embodiment is the same as that of the first embodiment. Accordingly, elements having substantially the same or corresponding functions as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the present embodiment, in the belt cleaning operation, among the four image forming stations P, only the first and second image forming stations PM and PC on the upstream side in the moving direction of the conveying belt 7 are exposed to the conveying belt 7. A circumferential speed difference is provided between the drum 9 and the drum 9.

  More specifically, in the present embodiment, the conveyor belt 7 is driven at a peripheral speed of 180 mm / s, whereas in the first and second image forming stations PM and PC, the photosensitive drum 9 is half that of 90 mm / s. Drive with s. On the other hand, in the third and fourth image forming stations PY and PK located downstream of the first and second image forming stations PM and PC, the photosensitive drum 9 is moved at 180 mm / s, which is the same as the peripheral speed of the conveying belt 7. To drive.

  As described in the first exemplary embodiment, the method of providing a peripheral speed difference between the photosensitive drum 9 and the conveying belt 7 in all the image forming stations P is particularly excellent in the effect of taking dirt into the toner layer. However, in the method of the first embodiment, since the rotational speed of the photosensitive drum 9 is slowed with respect to the conveyance belt 7, the surface area of the photosensitive drum 9 passing through the transfer portion N per unit time is reduced. From this, it is assumed that the toner on the conveyor belt 7 may rarely be fully collected on the photosensitive drum 9.

  Therefore, in this embodiment, for the first and second image forming stations PM and PC, the peripheral speed of the photosensitive drum 9 is set to 90 mm / s, and the cleaning toner image T on the conveyor belt 7 is applied to the photosensitive drum 9. The difference in peripheral speed with the conveyor belt 7 at the time of collection is maintained, and the mixing of the dirt and the toner layer is promoted even a little.

  On the other hand, for the third and fourth image forming stations PY and PK, the recovery capability of the cleaning toner image T on the transport belt 7 when the cleaning toner image T on the transport belt 7 is recovered to the photosensitive drum 9 is provided. Priority is given to the peripheral speed of the photosensitive drum 9 being 180 mm / s, which is faster (same as the peripheral speed of the conveyor belt 7).

  As described above, according to the present exemplary embodiment, as in the first exemplary embodiment, it is possible to increase the recovery capability of the cleaning toner image T directly transferred onto the conveyance belt 7 while maintaining the high stain removal capability on the conveyance belt 7. it can.

  As a modification of the present embodiment, the driving speed of the photosensitive drum 9 and / or the conveyance belt 7 in one image forming station P is changed between the transfer of the toner image and the recovery of the toner image in the belt cleaning operation. It is possible to change the peripheral speed difference between the photosensitive drum 9 and the conveyor belt 7 by switching. For example, while the peripheral speed of the conveyance belt 7 is constant at 180 mm / s in the belt cleaning operation, the peripheral speed of the photosensitive drum 9 of each image forming station P is transferred when the cleaning toner image T is transferred to the conveyance belt 7. Is 90 mm / s, and is performed in a state in which the difference between the photosensitive drum 9 and the conveying belt is large. On the other hand, when the cleaning toner image T is transferred from the conveyor belt 7 to the photosensitive drum 9 and recovered, the peripheral speed of the photosensitive drum 9 is switched to 180 mm / s and the recovery capability is high. By adopting such a configuration, the same effect as described above can be expected.

  In the above description, the mode of changing the circumferential speed difference between the photosensitive drum 1 and the conveying belt 7 has been described as providing the circumferential speed difference on the one hand and not providing the circumferential speed difference on the other hand. However, the present invention is not limited to this, and a larger first peripheral speed difference may be provided on one side, and a second peripheral speed difference smaller than the first peripheral speed difference may be provided on the other side. Good.

Example 5
The basic configuration of the image forming apparatus of this embodiment is the same as that of the first to fourth embodiments. In this embodiment, another embodiment of the cleaning toner image T formed during the belt cleaning operation will be described. In the present embodiment, the cleaning toner image T is limited in the thrust direction to a region detected by the optical sensor 30 during density control and color misregistration control or in the vicinity thereof.

  FIG. 6 shows an area on the conveying belt 7 where a cleaning toner image T is formed during the belt cleaning operation in this embodiment (when toner is not transferred as in the second embodiment, the area on the photosensitive drum 9 is shown. This is an area on the conveying belt 7 where the cleaning toner image is rubbed).

  In this embodiment, one optical sensor 30 for detecting a test image at the time of density control or color misregistration control is provided in the vicinity of both ends in the image forming area. The detection area d of each optical sensor 30 is shown in FIG. On the other hand, the region t where the cleaning toner image T is formed is slightly wider than the detection region d of the optical sensor 30 as shown. More specifically, in the present embodiment, the actual detection area d of the optical sensor 30 has a width of 2 mm in the thrust direction. On the other hand, the width t of the cleaning toner image T in the thrust direction is 10 mm. Thereby, a margin is provided so that the foreign matter does not surely enter the detection region d.

  Thus, in this embodiment, the cleaning toner image T is concentrated near the detection region d of the optical sensor 30. Accordingly, the detection region d of the optical sensor 30 on the surface of the conveyor belt 7 that is most likely to cause a problem due to the contamination of the conveyor belt 7 can be intensively cleaned although the amount of toner is small. . For this reason, the effect of suppressing the consumption of the toner used in the belt cleaning operation as much as possible can be obtained while suppressing the occurrence of the problem as in the previous embodiments. Note that the length l of the cleaning toner image T in the moving direction of the transport belt 7 is the same as in the above embodiments.

Example 6
As in the fifth embodiment, the present embodiment is a modification of the embodiment in which the cleaning toner image T formed during the belt cleaning operation is concentrated on the detection region d of the optical sensor 30 in the thrust direction. In this embodiment, a cleaning toner image T having a lower density is also formed in a region other than the detection region d of the optical sensor 30 in the thrust direction.

  That is, FIG. 7 shows a region where the cleaning toner image T of this embodiment is formed. In this embodiment, in the thrust direction, a toner image is formed in a region other than the detection region d of the optical sensor 30 in the image forming region g although the density is low. That is, the cleaning toner image T of the present embodiment has a first toner image region (region including the detection region d) T1 having a larger amount of toner in the thrust direction and a toner amount than that of the first toner image region. And the second toner image region T2 having a small amount. Thus, in addition to the same effect as that of the fifth embodiment, that is, the effect of preventing the decrease in detection accuracy of the optical sensor 30 due to the contamination of the conveyance belt 7 while suppressing the consumption of toner, the detection region of the optical sensor 30 can be obtained. It is possible to reduce the adhesion of dirt to the outside. For this reason, it is possible to prevent transfer spots and poor adsorption between the transfer material 1 and the conveyor belt 7 that occur during transfer of a normal toner image due to excessive contamination of the conveyor belt 7.

  As mentioned above, although this invention was demonstrated according to the specific Example, it should be understood that this invention is not limited to the aspect of each said Example.

  For example, in each of the above embodiments, the case where the transfer body is a conveyance belt has been described as an example, but the present invention is not limited to this. As known to those skilled in the art, there is an intermediate transfer type image forming apparatus including an intermediate transfer member as a transfer member.

  FIG. 9 shows a schematic configuration of an example of an image forming apparatus 200 including an intermediate transfer member as a transfer member. In the image forming apparatus 200 of FIG. 9, elements having substantially the same or corresponding functions and configurations as those of the image forming apparatus 100 shown in FIG. The image forming apparatus 200 shown in FIG. 9 has a belt-like intermediate transfer body, that is, an intermediate transfer belt 70 that moves around in contact with the photosensitive drum 1 as a transfer body onto which a toner image is transferred from the photosensitive drum 1. The image forming apparatus 200 in FIG. 9 includes a primary transfer roller 13 as a transfer unit, which corresponds to the transfer roller 13 in the image forming apparatus 100 in FIG. The primary transfer roller 13 is applied with a bias from a primary transfer bias power source 23 as a transfer bias output unit, so that a toner image is transferred between the photosensitive drum 9 and the intermediate transfer belt 70 in the primary transfer nip N1 which is a transfer portion. Move. Accordingly, the toner images can be sequentially transferred (primary transfer) from the photosensitive drum 9 of each image forming station P onto the intermediate transfer belt 70. The toner image formed on the intermediate transfer belt 70 is subjected to a secondary transfer bias applied to the secondary transfer roller 71 in the secondary transfer nip N2 where the intermediate transfer belt 70 and the secondary transfer roller 71 are in contact with each other. Transfer (secondary transfer) is performed on the transfer material 1.

  As in the above embodiments, in the intermediate transfer type image forming apparatus 200, a difference in peripheral speed is provided between the photosensitive drum 9 and the intermediate transfer belt 70 during normal print image formation or test image formation. May be. Of course, this peripheral speed difference may not be provided. Also in the image forming apparatus 200 of FIG. 9, similarly to the image forming apparatus 100 of FIG. 1, a test image is formed on the intermediate transfer belt 70, which is detected by the optical sensor 30, and the image forming conditions and the like are determined. Control.

  Also in such an intermediate transfer type image forming apparatus 200, the transfer material 1 is separated after coming into contact with the intermediate transfer belt 70 in the secondary transfer portion N 2, so that foreign matter such as paper dust adheres. There is. Therefore, in the image forming apparatus 200 as well, by performing the belt cleaning operation in the same manner as in each of the above embodiments, the same effects as those described in the above embodiments can be obtained.

  That is, the image forming apparatus 200 transfers the toner from the photosensitive drum 9 onto the intermediate transfer belt 70 and transfers the toner on the intermediate transfer belt 70 to the transfer material 1 and the toner on the photosensitive drum 9. A second mode in which the toner is transferred onto the intermediate transfer belt 70 and the toner on the intermediate transfer belt 70 is reversely transferred onto the photosensitive drum 9, as described in the first embodiment. The difference in the peripheral speed between the peripheral speed of the intermediate transfer belt 70 and the peripheral speed of the photosensitive drum 9 when toner is transferred from the photosensitive drum 9 onto the intermediate transfer belt 70 is different between the first mode and the second mode. . The other characteristic belt cleaning operations described in the above embodiments are substantially the same by replacing the transport belt 7 with the intermediate transfer belt 70 and the transfer roller 13 as transfer means as the primary transfer roller. This can also be applied to the intermediate transfer type image forming apparatus 200. The operation of transferring the toner on the photosensitive drum to the transfer material 1 on the conveying belt 7 in the direct transfer type image forming apparatus 100 of each of the above embodiments is performed on the intermediate transfer belt in the intermediate transfer type image forming apparatus 200. This corresponds to the operation of transferring the toner on the photosensitive drum 9.

  When the cleaning toner image T formed on the intermediate transfer belt 70 passes through the secondary transfer portion N2, the secondary transfer roller 71 may be retracted from the intermediate transfer belt 70.

1 is a schematic configuration diagram of a main part of an embodiment of an image forming apparatus according to the present invention. It is a graph which shows the effect of this invention. FIG. 4 is a development view of a conveying belt for explaining a forming region of an embodiment of a cleaning toner image formed according to the present invention. It is a schematic control block diagram for demonstrating the control aspect in one Example of this invention. It is a principal part schematic block diagram which shows the mode of one image forming station in execution of the belt cleaning operation | movement in one Example of this invention. It is explanatory drawing for demonstrating the formation area of the other Example of the cleaning toner image formed according to this invention. It is explanatory drawing for demonstrating the formation area of the other Example of the cleaning toner image formed according to this invention. It is a schematic block diagram of an example of the optical sensor which detects a test image. It is a principal part schematic block diagram which shows the other example of the image forming apparatus which can apply this invention.

Explanation of symbols

7 Conveyor belt (transfer body)
8 Image forming means 9 Photosensitive drum (image carrier)
10 Charging roller (charging means)
11 Laser exposure optical system (exposure means)
12 Developer (Developer)
13 Transfer roller (transfer means)
14 Cleaner (cleaning means)
30 Optical sensor (detection means)
100 Image forming apparatus

Claims (11)

A movable image carrier that carries a toner image, a movable intermediate transfer member that receives the transfer of the toner image on the image carrier, and a toner image that is transferred from the image carrier to the intermediate transfer member. An image forming apparatus comprising: a first mode; and a second mode in which a toner image on the image carrier is passed between the image carrier and the intermediate transfer member without being transferred onto the intermediate transfer member. In
A cleaning process in which the image carrier carries a cleaning toner image for cleaning the intermediate transfer body, and the second mode is executed in the cleaning process, and the peripheral speed of the image carrier and the intermediate An image forming apparatus, wherein a peripheral speed difference from a peripheral speed of a transfer body is different between the first mode and the second mode.   In the direction orthogonal to the moving direction of the image carrier, the length of the cleaning toner image is longer than the maximum toner image that can be carried by the image carrier and is longer than the length of the intermediate transfer member. The image forming apparatus according to claim 1, wherein the image forming apparatus is short. A transferable image carrier that carries a toner image; a transfer material carrier that carries a transfer material; and a transfer material that transfers the toner image on the image carrier to a transfer material on the transfer material carrier. And a second mode in which the toner image on the image carrier is transferred between the image carrier and the transfer material carrier without being transferred to the transfer material or the transfer material carrier. In the image forming apparatus,
A cleaning process in which the image carrier carries a cleaning toner image for cleaning the transfer material carrier, and the second mode is executed in the cleaning process, and the peripheral speed of the image carrier and the An image forming apparatus, wherein a difference in peripheral speed from a peripheral speed of a transfer material carrier is different between the first mode and the second mode.   In the direction orthogonal to the moving direction of the image carrier, the length of the cleaning toner image is longer than the maximum toner image that can be carried by the image carrier, and the length of the transfer material carrier. The image forming apparatus according to claim 3, wherein the image forming apparatus is shorter than the predetermined length. A movable image carrier that carries a toner image, a movable intermediate transfer member that receives the transfer of the toner image on the image carrier, and a toner image transferred from the image carrier to the intermediate transfer member. A first mode in which the toner image on the intermediate transfer member is transferred to a transfer material, and the toner on the intermediate transfer member transferred after the toner image on the image carrier is transferred onto the intermediate transfer member. A second mode for reversely transferring an image onto the image carrier,
A cleaning step for transferring a cleaning toner image for cleaning the intermediate transfer member from the image carrier onto the intermediate transfer member, and when the second mode is executed in the cleaning step, An image forming apparatus, wherein the toner image transferred onto the intermediate transfer member passes between the intermediate transfer member and the image carrier before being reversely transferred onto the image carrier. In the direction orthogonal to the moving direction of the image carrier, the length of the cleaning toner image is longer than the maximum toner image that can be carried by the image carrier and is longer than the length of the intermediate transfer member. The image forming apparatus according to claim 5 , wherein the image forming apparatus is shorter.   The difference in peripheral speed between the peripheral speed of the intermediate transfer member and the peripheral speed of the image carrier when the toner image is transferred from the image carrier to the intermediate transfer member is the first mode and the second mode. The image forming apparatus according to claim 6, wherein the image forming apparatus is different from the first mode.   When the second mode is executed in the cleaning step, the peripheral speed of the image carrier when the toner transferred onto the intermediate transfer member passes between the intermediate transfer member and the image carrier; The difference in peripheral speed from the peripheral speed of the intermediate transfer member is different from the peripheral speed difference when transferring a toner image from the image carrier to the intermediate transfer member in the first mode. Item 8. The image forming apparatus according to any one of Items 5 to 7. A transferable image carrier that carries a toner image; a transfer material carrier that carries a transfer material; and a transfer material that transfers the toner image on the image carrier to a transfer material on the transfer material carrier. One mode, a second mode in which the toner image on the image carrier is transferred onto the transfer material carrier, and the transfer material carrier transferred from the image carrier in the second mode. A third mode for reversely transferring a toner image onto the image carrier,
A cleaning step of transferring a cleaning toner image for cleaning the transfer material carrier from the image carrier onto the transfer material carrier; in the cleaning step, the second mode and the third mode; When the mode is executed, the toner image transferred onto the transfer material carrier passes between the transfer material carrier and the image carrier before the third mode. Image forming apparatus.   The image forming apparatus according to claim 9, wherein a difference in peripheral speed between the peripheral speed of the image carrier and the peripheral speed of the transfer material carrier is different between the first mode and the second mode. .   The difference in the peripheral speed between the peripheral speed of the image carrier and the peripheral speed of the transfer material carrier is that the toner image transferred on the transfer material carrier before the third mode in the cleaning step is The image forming apparatus according to claim 9, wherein a difference in peripheral speed when passing between the transfer material carrier and the image carrier is different from a peripheral speed difference in the first mode.

Images