JP2008170815A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem which conventionally has been frequently generated in an image forming apparatus where a bias roller is arranged at the inside of a belt for transferring toner on the surface of a photoreceptor to the surface of an intermediate transfer belt that the surface of the bias roller is stained by toner, thus a bias is not effectively applied, and, image quality is reduced by providing a cleaning means for removing foreign matters and toner stuck to the surface of a transfer member arranged at the inside of the intermediate transfer belt. <P>SOLUTION: As a method where a reverse bias is applied to a transfer means, toner is transited to an intermediate transferring belt 1, and the rear side of the intermediate transfer belt 1 is cleaned, an elastic blade is used. An intermediate transfer rear-side cleaner 26 is arranged between a cleaning opposed roller 20 and the primary transfer roller 8K in the rear side of the intermediate transfer belt 1, and the toner removed with the intermediate transfer belt rear-side cleaner 26 is recovered at a recovering part 27, arranged directly below in the gravity direction of the intermediate transfer belt rear side cleaner 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a fax machine, a printer, and a printing machine that forms an image using an electrophotographic system, and a transfer device used for these.

  An image forming apparatus that forms an image using an electrophotographic technique is configured using members having various structures. For example, a roller-shaped member such as a charging roller used as a charging member or a transfer roller used as a transfer unit, an intermediate transfer belt as an intermediate transfer member used in a color image forming apparatus, or a belt such as a paper transport belt for transporting paper There are shape members.

  Among these, since the belt-shaped member can be freely changed by the arrangement of the rollers including the form, it is possible to increase the degree of freedom of arrangement of various mechanism units arranged in the apparatus, Enables miniaturization and greatly contributes to lower prices. As an example of an image forming apparatus using such a belt-shaped member, an image forming apparatus described in Patent Document 1 using a belt-shaped member as an intermediate transfer member is known. In these conventional examples, a bias roller for transferring toner from the photosensitive member to the intermediate transfer belt is disposed inside the intermediate transfer belt.

Japanese Patent No. 3733277

  By the way, in an image forming apparatus using an electrophotographic system, in many cases, image recording on a recording medium is performed using toner. The toner is stored in the toner hopper (storage unit), the developing unit, the cleaning unit, the waste toner storage unit, etc., but since it is a fine resin powder, it may leak from those storage members and its joints. In some cases, the toner is floated by the airflow in the apparatus, and the entire apparatus becomes dirty. In particular, in the image forming apparatus having the belt-shaped member described in the prior art, the toner may enter the back surface of the belt and adhere to the roller back surface and the inner roller surface.

  If the back surface of the belt or the roller to be contained becomes dirty in this way, a bias is applied to transfer the toner on the surface of the photoreceptor onto the surface of the intermediate transfer belt inside the intermediate transfer belt that is endlessly wound around the roller as in the conventional example. In the image forming apparatus in which the roller is disposed, the surface of the bias roller is contaminated with toner, so that there is a problem that the bias is not effectively applied and the image quality is deteriorated.

  Therefore, the present invention is intended to solve the conventional problem by providing a cleaning means for removing foreign matter and toner adhering to the surface of a transfer member disposed inside the belt.

  The transfer device according to claim 1 of the present invention includes an endless belt having an internal space, an image carrier that is provided on an outer peripheral surface of the endless belt and carries a developer charged to a predetermined polarity, and the endless belt. A transfer device disposed in an inner space of the belt and having a transfer member configured to transfer the developer to the endless belt or a recording medium carried on the endless belt; A cleaning means for removing the agent is provided.

  The transfer device according to claim 2 is the transfer device according to claim 1, wherein the cleaning unit applies a bias having the same polarity as the predetermined polarity to the transfer member, and adheres to the surface of the transfer member. Or the developer is moved to the back surface of the endless belt for cleaning.

  The transfer apparatus according to claim 3 is the transfer apparatus according to claim 2, further comprising a cleaning unit that cleans foreign matter and developer adhering to the back surface of the endless belt.

  The transfer device according to claim 4 is the transfer device according to claim 1, wherein the endless belt is stretched around at least a plurality of rollers, and at least one of the plurality of rollers is attached to a surface of the roller. A roller cleaning means for removing dirt is provided.

  The transfer device according to claim 5 is the image forming apparatus according to claim 2, wherein the cleaning means for cleaning the back surface of the endless belt is in a roller shape, and toner and foreign matter are more likely to adhere to the back surface of the endless belt. It is characterized by being treated.

  The transfer device according to claim 6 is the transfer device according to any one of claims 1 to 5, wherein the toner image formed on the image bearing member is changed to the endless timing when the bias polarity of the means for applying the bias is changed. It is characterized in that it is executed at times other than when transferring to a belt.

  The transfer device according to claim 7 is characterized in that, in the transfer device according to claim 6, the bias applied to the primary transfer means is increased before the polarity change of the bias applied to the transfer member is performed. .

  The transfer device according to claim 8 is the transfer device according to claim 3, wherein the cleaning unit is provided on a roller disposed at a position facing the transfer member, and the transfer member is changed when the bias applying unit changes its polarity. The polarity of the bias means is changed at the timing when the back surface of the endless belt that has been in contact with the endless belt passes through the transfer member placement site as the endless belt moves.

  An image forming apparatus according to claim 9 uses the transfer device according to any one of claims 1 to 8.

  According to the transfer apparatus of the present invention, as the image forming apparatus is used, dirt enters the intermediate transfer member, and even if the primary transfer means becomes dirty, the primary transfer means has a reverse bias to the normal one. Can be transferred to and removed from the intermediate transfer body, so that the reduction in transfer efficiency and transfer unevenness caused by the contamination of those members can be suppressed, and the deterioration of the image due to printing is eliminated, resulting in high quality. It is possible to provide an image forming apparatus capable of outputting the image.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a schematic sectional view of an image forming apparatus to which the present invention is applied. An intermediate transfer belt 1 stretched horizontally is disposed at the center of the main body. The intermediate transfer belt 1 rotates counterclockwise in the drawing. Above the intermediate transfer belt 1, printing units 2K, 2M, 2C, and 2Y are arranged side by side from the upstream side in the rotation direction of the intermediate transfer belt 1. Further, an exposure unit 3 is disposed above the four printing units 2K, 2M, 2C, and 2Y.

  A waste toner box 17 is disposed below the intermediate transfer belt 1, and a paper cassette 10 is disposed below the waste toner box 17. A paper conveyance path is provided on the right side of the main body, and a paper feed roller 12, a registration roller 13, a secondary transfer roller 14, and a fixing device 15 are arranged from the paper cassette 10 to the upper right of the main body. An intermediate transfer belt cleaner 9 is disposed on the intermediate transfer belt 1 between the secondary transfer roller 14 and the printing unit 2K. A controller 16 is disposed on the left side of the main body on the opposite side.

  Next, the internal structure of the printing units 2K, 2M, 2C, and 2Y included in the image forming apparatus of FIG. 1 will be described. First, the structure of the printing unit 2Y will be described. A photosensitive drum 2Y is disposed at the center of the printing unit 2Y and rotates clockwise in the drawing. A charger 5Y, a developing device 6Y, and a photoconductor cleaner 7Y are arranged along the rotation direction on the outer periphery of the photoconductor drum 2Y. The other printing units 2M, 2C, and 2K have the same structure as the printing unit 2Y. The charging units 5M, 5C, and 5K, the developing units 6M, 6C, and 6K, and the photoreceptor cleaners 7M, 7C, and 7K are the same. It is arranged in.

Next, functions and features of each member will be described.
A detailed sectional view of the intermediate transfer belt 1 is shown in FIG. The intermediate transfer belt 1 is stretched by two rollers, a driven roller 18 and a driving roller 19 which are tension rollers. In addition, the intermediate transfer belt 1 includes primary transfer rollers 8K, 8M, 8C, and 8Y and a cleaning counter roller 20 along the rotation direction of the belt. The intermediate transfer belt 1 is a semiconductive resin belt having a volume resistance of 10 MΩ to 1 GΩcm and a surface resistance of 10 MΩ to 1 GΩ / □. The material is mainly composed of polycarbonate resin so as to ensure sufficient strength against repeated bending so that it can be used as a belt, and has a thickness of 100 to 150 μm. Of course, it is also possible to use resin materials, such as a polyimide resin and a polyamide resin, by appropriate thickness. The driven roller 18 applies tension to the intermediate transfer belt 1 and applies tension of 100 to 400 N / m. The intermediate transfer belt 1 is driven by rotating a driving roller 19. Therefore, in order to stably drive the intermediate transfer belt 1 by friction, a friction layer having a friction coefficient of 0.1 or more, for example, a thin rubber layer, is formed on the surface of the drive roller 19.

  The primary transfer rollers 8K, 8M, 8C, and 8Y are provided to transfer the toner images formed by the printing units 2K, 2M, 2C, and 2Y to the surface of the intermediate transfer belt 1, and use a metal roller. Yes. The primary transfer rollers 8K, 8M, 8C, and 8Y are applied with a bias having a polarity opposite to that of the toner (in this embodiment, a positive bias because the toner has a negative polarity), and the toner is electrostatically applied to the surface of the intermediate transfer belt 1. Transcript. The primary transfer rollers 8K, 8M, 8C, and 8Y are arranged immediately below the photosensitive drums 4K, 4M, 4C, and 4Y arranged in the printing units 2K, 2M, 2C, and 2Y. The intermediate transfer belt 1 is slightly shifted in the running direction, and the intermediate transfer belt 1 is wound around and contacts the respective photosensitive drums and the primary transfer roller.

  The cleaning facing roller 20 is disposed at a position facing the intermediate transfer belt cleaner in order to stabilize the contact property of the intermediate transfer belt cleaner 9. The cleaning facing roller 20 is composed of a surface layer and a metal shaft, and the surface layer has some adhesiveness. The reason why the surface layer is made sticky is to adhere dirt on the back surface of the intermediate transfer belt 1 and clean the back surface of the belt, details of which will be described later.

  The exposure device 3 is an exposure device using a laser scanning optical system or an LED array, and irradiates light corresponding to an image data signal onto a photosensitive drum to form an electrostatic latent image.

  The printing units 2K, 2M, 2C, and 2Y are configured as separate units, and can be easily removed. The photosensitive drums 4K, 4M, 4C, and 4Y are drum-shaped members in which a photosensitive layer is formed on the surface of a metal tube. The chargers 5K, 5M, 5C, and 5Y charge the surface of the photosensitive drums 4K, 4M, 4C, and 4Y to a predetermined potential, and use a system that uses a charging principle such as a roller charging method or a corotron charging method. ing. The developing devices 6K, 6M, 6C, and 6Y are used for developing a latent image formed on the surface of the photosensitive drums 4K, 4M, 4C, and 4Y with toner to form a visible image. The developing devices 6K, 6M, 6C, and 6Y store toners of different colors, for example, black, magenta, cyan, and yellow, and toner images of different colors are stored on the photosensitive drums 4K, 4M, 4C, and 4Y, respectively. Form.

  In the image forming apparatus of FIG. 1, toner is rubbed against a roller-shaped developing roller, and this toner is rubbed / restricted with a metal blade to form a toner layer having a prescribed charge amount and adhesion amount on the surface of the developing roller. A toner system corresponding to the electrostatic latent image on the photosensitive member is formed on the surface of the photosensitive member by contacting the surface of the photosensitive member with a non-magnetic one-component developing system. Of course, other development systems such as a two-component development system having the same function may be used.

  The photoreceptor cleaners 7K, 7M, 7C, and 7Y are formed on the surfaces of the photoreceptor drums 4K, 4M, 4C, and 4Y after the toner images developed on the surfaces of the photoreceptor drums 4K, 4M, 4C, and 4Y are transferred to the intermediate transfer belt 1. The residual toner is removed, and the toner is scraped off by a rubber blade.

  The intermediate transfer belt cleaner 9 removes toner remaining on the surface of the intermediate transfer belt 1 after being transferred from the surface of the intermediate transfer belt 1 to the paper 11, and scrapes the toner from the intermediate transfer belt 1 with a rubber blade. take.

  The paper cassette 10 is for storing paper 11 as a recording medium. The paper feed roller 12 is for pulling out the paper 11 from the paper cassette 10. The registration roller 13 is used to level the front end of the paper 11 and to transport the paper to the transfer unit in accordance with the front end of the image.

  The secondary transfer roller 14 is for transferring the toner image formed on the surface of the intermediate transfer belt 1 to the paper 11, and uses a medium resistance rubber roller to bring the paper 11 and the toner image on the intermediate transfer belt 1 into close contact with each other. At the same time, a bias image having a polarity opposite to that of the toner is applied to transfer the toner image onto the paper 11.

  The fixing device 15 is for fixing the toner image on the paper 11 to the paper by melting and heating it with heat and pressure.

  The controller 16 processes external control signals and image data to control the operation of the main body and image output. The waste toner box 17 is a member that stores and holds the toner scraped off by the intermediate transfer belt cleaner 9 and the photoreceptor cleaners 7K, 7M, 7C, and 7Y.

  Next, the operation of the image forming apparatus in FIG. 1 will be described. When an image forming signal and image data are input to the controller 16 from the outside such as a computer, rotation of the intermediate transfer belt 1 and driving of the printing units 2Y, 2M, 2C, and 2K are started. After the intermediate transfer belt 1 rotates stably, the exposure unit 3 first starts image exposure to the printing unit 2K at the most upstream portion in the rotation direction of the intermediate transfer belt 1 based on the image signal, and the surface of the photosensitive drum 4K. Then, an electrostatic latent image is formed, and a toner image is created by the developing device 6K and transferred to the intermediate transfer belt 1. The toner images are sequentially formed by the printing units 2M, 2C, and 2Y so as to be superimposed on the toner image that is moved with the rotation of the intermediate transfer belt 1, and transferred to the intermediate transfer belt 1 to be formed on the surface of the intermediate transfer belt 1. A full-color toner image is formed. The toner image formed on the intermediate transfer belt 1 is drawn from the paper cassette 10 by the paper feed roller 12 in advance by the secondary transfer roller 14 at the timing, and transferred to the paper 11 conveyed to the position of the secondary transfer roller 14. To do. The toner image transferred onto the surface of the paper 11 is fused and fixed to the surface of the paper 11 by the fixing device 15 and then output to the outside of the main body.

  In the image forming apparatus of FIG. 1, when the printing units 2K, 2M, 2C, and 2Y are near the end of their lives, some toner may be scattered from the inside of the printing units 2K, 2M, 2C, and 2Y. The belt 1 may be mixed inside the belt 1 and adhere to the primary transfer rollers 8K, 8M, 8C, and 8Y disposed inside. As described above, when toner adheres to the primary transfer rollers 8K, 8M, 8C, and 8Y and the amount increases to cover the roller itself, the toner in the primary transfer portion is moved from the photosensitive drum to the intermediate transfer belt. There arise problems that the electric field is reduced, transfer efficiency is lowered, and an image is thinned. In addition, the adhesion of the dirty toner to the primary transfer roller does not cover the roller uniformly, resulting in uneven transfer rate, which also appears in the final printed image, greatly reducing the image quality. Will end up.

  In order to solve the above problem, in the image forming apparatus of the present invention, the primary transfer rollers 8K, 8M, 8M, 8M, and 8Y are given a bias having a polarity opposite to that of the primary transfer rollers 8K, 8M, 8C, and 8Y. Control is provided to remove the foreign matter on the surfaces of the primary transfer rollers 8K, 8M, 8C, and 8Y by electrostatically transferring the toner adhering to the surfaces of the 8C and 8Y to the back surface of the intermediate transfer belt. Further, a cleaning counter roller 20 disposed on the back surface of the intermediate transfer belt 1 is provided with a function for cleaning the toner transferred to the back surface of the intermediate transfer belt 1.

The details will be described below.
FIG. 3 is a diagram illustrating a bias structure for the photosensitive drums 4K, 4M, 4C, and 4Y and the primary transfer rollers 8K, 8M, 8C, and 8Y of the image forming apparatus of FIG. The photosensitive drums 4K, 4M, 4C, and 4Y are each grounded to a zero potential. On the other hand, a positive bias voltage having a polarity opposite to that of the toner is applied to the primary transfer rollers 8K, 8M, 8C, and 8Y as described above. These primary transfer rollers 8K, 8M, 8C, and 8Y are respectively provided with high-voltage power supplies 21K, 21M, 21C, and 21Y so that a bias can be applied independently. The high-voltage power supplies 21K, 21M, 21C, and 21Y can apply positive and negative voltages to the primary transfer rollers 8K, 8M, 8C, and 8Y. In the example of FIG. 3, a power source is arranged for each primary transfer roller 8, but the effect of the present invention does not change even if a method of applying a bias to the four primary transfer rollers 8 with one power source is used.

  FIG. 4 is a diagram showing the operation of the high-voltage power supplies 21K, 21M, 21C, and 21Y of the image forming apparatus of FIG. 1 using a timing chart. When a print command is input to the main body (T0), the intermediate transfer belt is first driven (T1). Thereafter, a positive voltage (300 to 1200 V) is generated by the high voltage power source 21 (T2), and image formation is started (T3). When the image formation is completed (T4), the polarity of the output of the high-voltage power supply 21 is reversed to output a negative voltage (-300 to 800V) (T5), and the primary transfer roller 8 is cleaned. It is desirable that the negative voltage is output for at least the time required for the primary transfer roller 8 to make one round. After a negative voltage is output for a desired time by the high-voltage power source 21, the output of the high-voltage power source 21 is turned off (T6), and the rotation of the intermediate transfer belt 1 is stopped (T7).

  By the way, in the case of the image forming apparatus of FIG. 1, since the toner transferred from the primary transfer roller 8 to the back surface of the intermediate transfer belt 1 is removed by the cleaning counter roller 20, the toner on the back surface of the intermediate transfer belt 1 is also removed. Then, it is necessary to cause the intermediate transfer belt 1 to idle so that the toner transferred from the primary transfer roller 8 to the back surface of the intermediate transfer belt 1 reaches the cleaning counter roller 20. For this reason, in the image forming apparatus of FIG. 1, the time for the intermediate transfer belt 1 to make one round is ensured as the time between T6 and T7.

  Of course, the timing for outputting the negative voltage may be executed after printing a desired number of sheets in addition to the above, or by interrupting the image forming operation of the main body after printing the desired number of sheets.

  Next, the cleaning counter roller 20 will be described in detail. FIG. 5 is a view showing a detailed cross section of the cleaning facing roller 20. The cleaning counter roller 20 includes a metal shaft 22 and a surface layer 23, and the surface layer 23 uses foamed urethane rubber. In particular, in the case of such a foamed rubber, if the foamed cell is made very small, for example, 50 μm or less, the toner easily adheres, and the toner on the back surface of the intermediate transfer belt 1 can be efficiently cleaned. Of course, depending on the amount of toner mixed on the back surface of the intermediate transfer belt 1, a surface layer of another material or structure, such as EPDM, NBR, silicon rubber solid, sponge rubber, fluororesin, silicon resin, or urethane resin, is coated. It is also possible to use it. Moreover, you may comprise only the metal shaft 22 without using a surface layer.

  As described above, in the image forming apparatus according to the present exemplary embodiment, even when the toner enters the intermediate transfer belt as the apparatus is used and the primary transfer roller is contaminated, the primary transfer roller is biased in a reverse bias. Is applied to transfer the toner to the intermediate transfer belt, and the transferred toner is collected by the cleaning counter roller, so that the dirt on the primary transfer roller and the dirt on the intermediate transfer belt can be removed. Accordingly, a decrease in transfer efficiency and transfer unevenness caused by the contamination of these members are suppressed, and image deterioration due to printing is eliminated, so that a high-quality image can be provided.

  Incidentally, the primary transfer rollers 8K, 8M, 8C, and 8Y used in the image forming apparatus of FIG. 1 are metal rollers, but it is also possible to use rollers having various other configurations. FIG. 6 is a view showing a cross-sectional structure of a roller in which a surface layer 25 is provided on the surface of the metal shaft 24. For the surface layer 25, a resin material having electrical conductivity (volume resistance of 10 MΩcm or less), for example, a fluororesin having a thickness of several μm to several mm in which carbon is dispersed, a silicon resin, and a urethane resin are used. In the roller of FIG. 6 in which the surface layer is formed of these resin materials, the effect of making it difficult for toner and foreign matter mixed on the back surface of the intermediate transfer belt 1 to adhere to these rollers is obtained, and at the same time, the primary transfer roller by bias application. The transfer of dirt from 8K, 8M, 8C, 8Y to the intermediate transfer belt 1 is improved.

  Moreover, it is also possible to use an elastic body for the surface layer 25 of FIG. In the case of using an elastic body, conductive urethane, EPDM, NBR, or silicon rubber in solid form or sponge form can be used.

  Further, the arrangement positions of the primary transfer rollers 8K, 8M, 8C, and 8Y are slightly in the running direction of the intermediate transfer belt 1 with respect to the positions immediately below the photosensitive drums 4K, 4M, 4C, and 4Y in the image forming apparatus of FIG. Although the arrangement is shifted, the arrangement is arranged on the upstream side in the traveling direction, and the arrangement is arranged immediately below the photosensitive drums 4K, 4M, 4C, and 4Y at a position where a nip is formed by the photosensitive drum and the primary transfer roller. Even so, the effects of the present invention can be obtained.

  By the way, in the image forming apparatus of the embodiment of FIG. 1, the toner transferred from the surface of the primary transfer rollers 8K, 8M, 8C, 8Y to the intermediate transfer belt 1 is adhered to the surface of the cleaning counter roller 20 on which the surface layer is formed. It has been removed. In this way, not only the cleaning counter roller 20 shown in the example of FIG. 1 but also other internal members such as the driven roller 18 and the drive roller 19 are attached to the members included in the intermediate transfer belt 1 in advance. It is also possible to carry out with the same function as the cleaning counter roller 19. Further, the toner transferred to the back surface of the intermediate transfer belt 1 may be removed by the following method.

  FIG. 7 shows an example in which a cleaning member using an elastic blade is used as a method for cleaning the back surface of the intermediate transfer belt 1. An intermediate transfer belt back surface cleaner 26 is disposed between the cleaning opposing roller 20 and the primary transfer roller 8K on the back surface of the intermediate transfer belt 1, and a back surface of the intermediate transfer belt is collected by a collecting unit 27 disposed immediately below the intermediate transfer belt back surface cleaner 26 in the gravity direction. The toner removed by the cleaner 26 is collected. When the toner adhering to the back surface of the intermediate transfer belt 1 has a large amount of toner mixed in the intermediate transfer belt 1, for example, in an image forming apparatus in which the lifetime of the apparatus is set long, the image forming apparatus shown in FIG. In the method of holding dirt on the surface of the encapsulating member used in FIG. 7, since a lot of dirt is generated and it cannot be handled, it is effective to use the cleaning member having the structure of FIG. Further, in the example of FIG. 7, an elastic blade is used as a member for cleaning the back surface of the intermediate transfer belt 1, but a member such as a brush roller known as a method for cleaning toner can also be used.

  FIG. 8 is a view showing another example of a cleaning member suitable for use when the amount of toner mixed on the back surface of the intermediate transfer belt 1 is large. The example of FIG. 8 describes a method of scraping off the transferred toner by providing a cleaning mechanism on the surface of the roller member to be included. In the structure of FIG. 8, a driven roller cleaning blade 28 that cleans the surface of the driven roller 18 is disposed in the vicinity of the driven roller 18, and a collecting unit 29 that collects the toner scraped off by the driven roller cleaning blade 28 is provided as the driven roller cleaning blade 28. It is located directly below. By using the configuration of FIG. 8, even when a large amount of toner is mixed on the back surface of the intermediate transfer belt 1, image formation can be realized without any problem.

  FIG. 9 is a diagram showing a configuration of a method for further effectively cleaning the back surface of the intermediate transfer belt 1 of FIG. In the embodiment of FIG. 9, the driving roller 19 is provided with a driving roller cleaning blade 30 (a brush roller can be used) for cleaning the roller surface, and adheres to the surface of the driving roller 19 scraped by the driving roller cleaning blade 20. A collecting unit 31 that collects toner is disposed immediately below the driving roller cleaning blade 30. As a result, the toner is transferred from the front surface of the primary transfer rollers 8Y, 8M, 8C, and 8K to the back surface of the intermediate transfer belt 1, and the toner transferred to the surface of the drive roller 19 is scraped off by the drive roller cleaning blade 30 to execute toner cleaning. it can. At this time, the toner transfer from the intermediate transfer belt 1 to the drive roller 19 is also efficient by using electrostatic force due to the bias of the secondary transfer roller 14 disposed on the front side of the intermediate transfer belt 1 at a position facing the drive roller 19. Can be improved.

  In the configuration of FIG. 9, the above principle is realized by changing the polarity of the secondary transfer high-voltage power supply 32 that applies a bias to the secondary transfer roller 14. In the image forming apparatus of FIG. 1, the toner on the surface of the intermediate transfer belt 1 is transferred to a sheet by applying a positive voltage to the secondary transfer roller 14. Since the toner adhering to the back surface of the intermediate transfer belt 1 has a negative polarity, if a negative bias is applied to the secondary transfer roller 14, the toner can be attached to the driving roller 19 even with an electrostatic force. The cleanability of the back surface of the intermediate transfer belt 1 can be improved. The toner adhering to the surface of the driving roller 19 is removed by a driving roller cleaning blade 30 that cleans the surface of the driving roller 19.

FIG. 10 is a timing chart showing the operation of the secondary transfer high-voltage power supply 32 in the configuration of FIG.
When a print command is input to the main body (T0), first, the intermediate transfer belt is driven (T1). Thereafter, a positive voltage is generated by the high voltage power source 21 (T2), and image formation is started (T3). When the image formation is completed (T4), the polarity of the output of the high-voltage power supply 21 is reversed and a negative voltage is output (T5), and the primary transfer roller 8 is cleaned. It is desirable that the negative voltage is output for at least the time required for the primary transfer roller 8 to make one round. After a negative voltage is output by the high voltage power source 21 for a desired time, the output of the high voltage power source 21 is turned off (T6), but the toner transferred from the primary transfer roller 8 to the back surface of the intermediate transfer belt 1 rotates the intermediate transfer belt 1. Accordingly, the output of the secondary transfer high-voltage power supply 32 is set to a negative voltage at the timing (T7) when the secondary transfer portion is reached. Thereafter, the output of the secondary transfer high-voltage power supply 32 is turned off at the timing (T8) when all the toner on the back surface of the intermediate transfer belt 1 passes through the secondary transfer portion, and the rotation of the intermediate transfer belt 1 is stopped (T9).

  By using the systems shown in FIGS. 9 and 10, the toner transferred to the back surface of the intermediate transfer belt 1 can be reliably cleaned.

  Incidentally, toner transfer from the primary transfer rollers 8Y, 8M, 8C, and 8K to the intermediate transfer belt 1 is mainly performed by electrostatic force. Therefore, if the charging of the toner on the surfaces of the primary transfer rollers 8Y, 8M, 8C, and 8K can be increased in advance, the toner adhering to the surfaces of the primary transfer rollers 8Y, 8M, 8C, and 8K is transferred to the intermediate transfer belt 1. Can be done efficiently. FIG. 11 is a diagram illustrating a sequence in a case where control for applying a high positive voltage to the primary transfer rollers 8Y, 8M, 8C, and 8K is performed in advance. When a print command is input to the main body (T0), the intermediate transfer belt is first driven (T1). Thereafter, a positive voltage is generated by the high voltage power source 21 (T2), and image formation is started (T3). When the image formation is completed (T4), the polarity of the output of the high-voltage power supply 21 is inverted to output a negative voltage, but before that, a positive voltage higher than the voltage applied during normal image formation is applied (T5). ). This higher positive voltage is set to a voltage at which minute discharge is generated in the gaps between the primary transfer rollers 8Y, 8M, 8C, and 8K and the intermediate transfer belt 1. When a discharge occurs in the gap between the primary transfer rollers 8Y, 8M, 8C, and 8K and the intermediate transfer belt 1, a positive voltage is applied to the primary transfer rollers 8Y, 8M, 8C, and 8K, so that the intermediate transfer belt is applied. Plus on the 1 side, minus charge will be poured on the surfaces of the primary transfer rollers 8Y, 8M, 8C, 8K, and the charged state of the toner adhering to the surfaces of the primary transfer rollers 8Y, 8M, 8C, 8K Is surely negative and the charge amount is negatively increased. Thereafter, the primary transfer roller 8 is cleaned by setting the output of the high voltage power source 21 to a negative voltage (T6). It is desirable that the negative voltage is output for at least the time required for the primary transfer roller 8 to make one round. After the negative voltage is output for a desired time by the high voltage power source 21, the output of the high voltage power source 21 is turned off (T7), and the rotation of the intermediate transfer belt 1 is stopped (T8).

  In this way, the electrostatic force acting on the toner when a negative voltage is applied to the primary transfer rollers 8Y, 8M, 8C, and 8K by previously negatively charging the toner on the surface of the primary transfer rollers 8Y, 8M, 8C, and 8K. Can be improved, and the cleaning properties of the surfaces of the primary transfer rollers 8Y, 8M, 8C, and 8K can be improved.

  As described above, in the image forming apparatus according to the present exemplary embodiment, even when the toner enters the intermediate transfer belt as the apparatus is used and the primary transfer roller is contaminated, the primary transfer roller is biased in a reverse bias. Is applied to transfer the toner to the intermediate transfer belt, and the transferred toner is collected by the cleaning counter roller, so that the dirt on the primary transfer roller and the dirt on the intermediate transfer belt can be removed. Accordingly, a decrease in transfer efficiency and transfer unevenness caused by the contamination of these members are suppressed, and image deterioration due to printing is eliminated, so that a high-quality image can be provided.

  The apparatus of the embodiment described above is an image forming apparatus having an intermediate transfer tandem configuration having a plurality of photoconductors. However, the present invention is not limited to this, and the apparatus has a plurality of photoconductors and toner is supplied from the photoconductor. The present invention can also be applied to an apparatus having a direct transfer tandem configuration that directly transfers images onto a recording medium, and an image forming apparatus having an intermediate transfer configuration of one drum. Since the basic configuration of these devices is well known, detailed description and illustration are omitted.

  Further, as a cleaning method other than bias cleaning of the cleaning unit of the transfer member (primary transfer bias applying unit in the above-described embodiment), a cleaning blade, a cleaning brush, a cleaning roller, or the like is brought into contact with the transfer roller surface. Of course, it may be a thing. Also in this respect, since the basic configuration is known, detailed description and illustration are omitted.

  Furthermore, the transfer device according to the present invention and the image forming apparatus using the transfer device can employ a known and well-known configuration in addition to the above-described configuration, and is not limited to the illustrated configuration. For example, a cleaning unit that uses an elastic blade is used as a cleaning unit that cleans the back surface of the intermediate transfer member, a brush-shaped member is used as a cleaning unit that cleans the back surface of the intermediate transfer member, and a cleaning unit that cleans the roller surface. Various means such as using an elastic blade or a brush-shaped member can be employed.

That is, the toner image carrier itself, a belt-shaped intermediate transfer member disposed in contact with the toner image carrier, and the primary transfer contained in the intermediate transfer member and disposed substantially opposite to the toner carrier. Means, a primary transfer bias applying means for applying a bias to the primary transfer means, a secondary transfer means arranged on the surface side of the intermediate transfer member, and a secondary transfer bias means for applying a bias to the secondary transfer means. An image formed on the surface of the toner image bearing member is transferred to the surface of the intermediate transfer member by a bias voltage applied to the primary transfer unit, and the image transferred to the surface of the intermediate transfer member is transferred by the secondary transfer unit. In an image forming apparatus using an electrophotographic process for transferring to a recording medium, the polarity of the primary transfer bias applying means is changed to change the difference between the primary transfer means and the primary transfer means. Configured to be migrated to the back surface the intermediate transfer member and toner,
A configuration having a cleaning means for cleaning the back surface of the intermediate transfer member;
A configuration in which the intermediate transfer member is stretched by at least a plurality of rollers, and at least one of the plurality of rollers is provided with roller cleaning means for removing dirt on the surface;
The cleaning means for cleaning the back surface of the intermediate transfer member has a roller shape, and has been subjected to a process that makes it easier for toner and foreign matter to adhere to the back surface of the intermediate transfer member.
A configuration in which the timing for changing the bias polarity of the primary transfer bias applying means is executed except when the toner image formed on the toner carrying member is transferred to the intermediate transfer member;
A configuration in which the bias applied to the primary transfer unit is increased before the polarity change of the bias applied to the primary transfer unit is performed;
The roller cleaning unit is provided on a roller disposed at a position opposite to the secondary transfer unit, and the back surface of the intermediate transfer member is in contact with the primary transfer unit when the primary transfer bias applying unit changes polarity. A configuration in which the polarity of the secondary transfer bias unit is changed at a timing when the intermediate transfer unit passes through the arrangement portion of the secondary transfer unit as the intermediate transfer unit moves
It is possible to adopt various configurations and the like and variations thereof without departing from the scope of the claims.
Then, by changing the polarity of the primary transfer bias applying means, it is possible to remove foreign matter and toner adhering to the primary transfer means to the back surface of the intermediate transfer body, thereby removing the dirt on the primary transfer means. High quality image formation can be realized. Further, it is also possible to have cleaning means for cleaning the back surface of the intermediate transfer body in consideration of cleaning of the back surface of the intermediate transfer body. Further, the intermediate transfer body is stretched by at least a plurality of rollers, The same can be said by providing roller cleaning means for removing dirt on the surface of at least one of the rollers.
The same is true if the cleaning means for cleaning the back surface of the intermediate transfer member has a roller shape and is subjected to a treatment that makes it easier for toner and foreign matter to adhere to the back surface of the intermediate transfer member. The same applies even if the cleaning means for cleaning is a cleaning means using an elastic blade or a brush-shaped member.
Further, the cleaning means for cleaning the roller surface is the same as the cleaning means using an elastic blade or a brush-shaped member.
In order to execute the transfer with the above-described configuration, the timing for changing the bias polarity of the primary transfer bias applying means is executed except when the toner image formed on the toner carrying member is transferred to the intermediate transfer member. The bias applied to the primary transfer unit may be increased before changing the polarity of the bias applied to the primary transfer unit. In addition, the roller cleaning unit is provided on a roller disposed at a position opposite to the secondary transfer unit, and the back surface of the intermediate transfer member that the primary transfer unit is in contact with when the primary transfer bias applying unit changes polarity is intermediate transfer. The polarity of the secondary transfer bias unit may be changed at the timing of passing the arrangement portion of the secondary transfer unit as the unit moves.
In any case, even when dirt enters the intermediate transfer member as the apparatus of the present invention is used and dirt on the primary transfer unit is generated, a reverse bias is applied to the primary transfer unit. Dirt can be transferred to and removed from the intermediate transfer body, and the deterioration of transfer efficiency and transfer unevenness caused by the dirt of these members can be suppressed, and image deterioration due to printing can be eliminated or almost eliminated. The image forming apparatus can output a high-quality image.

Schematic sectional view of an image forming apparatus to which the present invention is applied Detailed sectional view of intermediate transfer belt 1 is a diagram illustrating a bias structure for a photosensitive drum and a primary transfer roller of the image forming apparatus of FIG. FIG. 1 is a timing chart illustrating the operation of the high-voltage power supply of the image forming apparatus of FIG. Detailed sectional view of cleaning counter roller The figure which showed the section structure of the roller which provided the surface layer on the surface of the metal shaft The figure which shows the example using the cleaning member which used the elastic blade as a method of cleaning the back surface of an intermediate transfer belt The figure which showed the other example of the cleaning member suitable for using when the amount of the toner mixed in the back surface of the intermediate transfer belt 1 is large. The figure which showed the structure of the method of implementing the cleaning of the back surface of the intermediate transfer belt of FIG. 8 more effectively FIG. 9 is a timing chart showing the operation of the secondary transfer high-voltage power supply 32 in the configuration of FIG. The figure which showed the sequence at the time of performing control which applies a high positive voltage beforehand to a primary transfer roller

Explanation of symbols

1 Intermediate transfer belt 1
2 (2K, 2M, 2C, 2Y) Printing unit 3 Exposure unit 4 (4K, 4M, 4C, 4Y) Photosensitive drum 5 (5K, 5M, 5C, 5Y) Charger 6 (6K, 6M, 6C, 6Y) ) Developer 7 (7K, 7M, 7C, 7Y) Photoconductor cleaner 8 (8K, 8M, 8C, 8Y) Primary transfer roller 9 Intermediate transfer belt cleaner 10 Paper cassette 11 Paper 12 Paper feed roller 13 Registration roller 14 Secondary Transfer roller 15 Fixing device 17 Waste toner box 16 Controller 18 Driven roller 19 Drive roller 20 Cleaning counter roller 21 (21, 21K, 21M, 21C, 21Y) High voltage power supply 22 Metal shaft 23 Surface layer 24 Metal shaft 25 Surface layer 26 Intermediate transfer Belt back surface cleaner 27 Recovery unit 28 Driven roller cleaning blade 29 Recovery unit 30 Drive roller cleaning blur De 31 recovery unit 32 the secondary transfer high-voltage power supply

Claims (9)

An endless belt having an internal space, an image carrier that is provided on the outer peripheral surface of the endless belt and carries a developer charged to a predetermined polarity, and disposed in the internal space of the endless belt, In a transfer apparatus having an endless belt or a transfer member that transfers to a recording medium carried on the endless belt,
A transfer apparatus comprising a cleaning means for removing foreign matter and developer adhering to the surface of the transfer member.   The transfer device according to claim 1, wherein the cleaning unit applies a bias having the same polarity as the predetermined polarity to the transfer member, and removes foreign matter and developer attached to the surface of the transfer member. A transfer device that is cleaned by being moved to.   3. The transfer apparatus according to claim 2, further comprising a cleaning unit that cleans foreign matter and developer adhering to the back surface of the endless belt.   2. The transfer device according to claim 1, wherein the endless belt is stretched around at least a plurality of rollers, and at least one of the plurality of rollers is provided with a roller cleaning means for removing dirt on the surface of the rollers. A transfer device characterized by that.   3. The image forming apparatus according to claim 2, wherein the cleaning means for cleaning the back surface of the endless belt has a roller shape, and has been subjected to a process in which toner and foreign matter are more likely to adhere to the back surface of the endless belt. Transfer device.   6. The transfer device according to claim 1, wherein the bias polarity of the means for applying the bias is changed at a timing other than when the toner image formed on the image carrier is transferred to the endless belt. A transfer device characterized in that the transfer device is executed.   7. The transfer apparatus according to claim 6, wherein the bias applied to the primary transfer means is increased before the polarity change of the bias applied to the transfer member is performed.   4. The transfer device according to claim 3, wherein the cleaning unit is provided on a roller disposed at a position opposite to the transfer member, and the endless belt is in contact with the transfer member when the bias applying unit changes polarity. A transfer apparatus, wherein the polarity of the bias means is changed at a timing when the back surface passes through the transfer member arrangement site as the endless belt moves. An image forming apparatus using the transfer device according to claim 1.