JP2011197110A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove fixing oil from a transfer part and to form excellent images.SOLUTION: In the image forming apparatus 100 including a secondary transfer roller 19 for transferring to a recording medium P a toner image on an intermediate transfer belt 8 where the toner images of photoreceptor drums 1Y, 1C, 1M, 1K are transferred, a cleaning blade 40 for cleaning the surface of the secondary transfer roller 19, and a fixing device 20 using fixing oil, when sticking of the fixing oil to the secondary transfer roller 19 occurs, a toner pattern covering an area including the sticking area of the fixing oil is transferred to the secondary transfer roller 19, the bias voltage of the same polarity as toner T is applied, and the toner T and the layer 60 of the fixing oil are mixed by a brush member 31 and removed by the cleaning blade 40.

Description

  The present invention relates to an image forming apparatus, and in particular, an intermediate transfer member to which a toner image on an image carrier is transferred, and a first transfer unit that transfers the toner image on the image carrier onto the intermediate transfer member; A second transfer means for transferring the toner image on the intermediate transfer member to a transfer material; a cleaning means for cleaning the surface of the second transfer means; and the toner image transferred by the second transfer means. The present invention relates to an image forming apparatus having fixing means for fixing to a transfer material.

  Conventionally, a belt transfer device is often used as a means for transferring a toner image formed on a photoreceptor. When the belt transfer device is used for transferring a toner image onto a transfer material, it can be expected to stably separate the transfer material from the photoconductor regardless of the type and state of the transfer material, and the transfer can be easily performed multiple times. it can. The belt transfer device is also used as an intermediate transfer device for transferring a toner image onto a transfer belt and then transferring it again to a transfer material. A full-color image forming apparatus using an intermediate transfer body can stably form a multicolor image without being affected by the type of transfer material when the primary transfer process is repeated for each color. Therefore, it is possible to configure the transfer material conveyance path on a straight line and to use various transfer materials.

  The image forming apparatus using the intermediate transfer member includes a photosensitive member as a first image carrier, an intermediate transfer member as a second image carrier, a charging unit, an exposure unit, a developing unit, a primary transfer unit, and a secondary transfer unit. Means and fixing means.

  In order to form an image, the surface of the photoreceptor is first charged by a charging unit. Next, an image pattern is exposed on the surface of the photoreceptor by exposure means such as a laser, and a potential difference is generated between the exposed portion and the unexposed portion on the surface of the photoreceptor to form an electrostatic latent image on the surface of the photoreceptor. When the electrostatic latent image is developed by the developing means, charged toner adheres to the exposed portion, and the latent image is visualized as a toner image.

  The toner image formed on the photosensitive member is primary-transferred to the intermediate transfer member by applying a voltage having a polarity opposite to that of the toner to the intermediate transfer member. In the case of a full-color image, the above process is repeated for a plurality of color toners to form an image in which a plurality of color toners are superimposed on the surface of the intermediate transfer member.

  Next, the image formed on the surface of the intermediate transfer member is transferred to a transfer material by applying a voltage having a polarity opposite to that of the toner by a secondary transfer unit. The transfer material that has been secondarily transferred in this way is fixed on the transfer material using heat or pressure by a fixing means. The fixing device includes a heating roller having a heater therein and a pressure roller that is in pressure contact with the heating roller. Fixing oil such as silicone oil because the paper image may be transferred to the heating roller when the paper with the unfixed toner image transferred to the nip between the heating roller and pressure roller is passed through. Is applied to the heating roller to prevent offset.

  In an image forming apparatus, it is widely known that a filming phenomenon occurs in which foreign matter adheres to an image carrier such as a photosensitive member or an intermediate transfer belt, a transfer roller, and the like. For example, when filming with unevenness occurs partially, resistance unevenness occurs on the surface, resulting in image unevenness due to a difference in transfer efficiency. In addition, a phenomenon occurs in which an image flows due to moisture absorption in a high humidity environment. In addition, the transfer efficiency changes due to a change in physical adhesion with the toner, and image defects such as density unevenness and missing characters tend to occur. Further, when the apparatus environment is high, the surface friction coefficient is increased, the adhesion force with the toner is increased, and cleaning failure is liable to occur.

  Filming generally occurs due to adhesion of a toner additive or resin, but when double-sided printing, the fixing oil that adheres after passing the first side of the paper adheres to the secondary transfer portion when transferring the second side. It can also be caused by oil wraparound. Various methods for removing such filming have been proposed.

  Patent Document 1 proposes a method of sliding the intermediate transfer member and the secondary transfer roller at different peripheral speeds. That is, Patent Document 1 has a removal mode for removing foreign matter adhering to the intermediate transfer member in order to prevent filming on the image forming unit from affecting the image quality, and the peripheral speed of the secondary transfer roller. Is operated at a peripheral speed different from that at the time of toner transfer, and is in sliding contact with the intermediate transfer member.

  Japanese Patent Application Laid-Open No. H10-228561 describes a technique that allows a fixing release agent to be removed by applying a bias. That is, Patent Document 2 describes a technique in which a release agent adhered to a sheet is transferred and removed by an electric field action in order to prevent filming on the image forming unit from affecting the image quality. Yes.

  However, the thing of patent document 1 has only the thing which can be removed by the electric field effect | action which can be removed, and there exists a problem that it cannot remove in the case of fixing oil which is not acted on by an electric field.

  Further, in the case of the one described in Patent Document 2, when the fixing oil wraps around and adheres to the secondary transfer portion during double-sided printing, the fixing oil cannot be removed only by sliding contact at different peripheral speeds. There is a problem of spreading.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can efficiently remove fixing oil from a transfer portion and can perform good image formation.

  According to the first aspect of the present invention, there is provided an image carrier that carries a toner image on a surface thereof, an intermediate transfer member to which a toner image on the image carrier is transferred, and a toner image on the image carrier on the intermediate transfer member. A first transfer means for transferring the toner image on the intermediate transfer body, a second transfer means for transferring the toner image on the intermediate transfer member to a transfer material, a cleaning means for cleaning the surface of the second transfer means, and the second transfer. A fixing unit that fixes the toner image transferred by the fixing unit to the transfer material, wherein the fixing oil is attached to the second transfer unit. A toner pattern creating means for creating a toner pattern covering the area to be included, and a means for applying a bias voltage having the same polarity as the toner pattern transferred to the second transfer means, and in contact with the second transfer means for transferring. Cleaning auxiliary means for applying repulsive force to the toner pattern with the bias voltage, and after the double-sided printing on the transfer material, the toner pattern creating means applies a predetermined toner pattern to the second transfer means. An image forming apparatus characterized in that the fixing oil is generated and removed together with the toner pattern by the cleaning means.

  According to a second aspect of the present invention, in the image forming apparatus, an image carrier that carries a toner image on a surface thereof, a transfer unit that transfers a toner image on the image carrier to a recording material, and a surface of the transfer unit are cleaned. In an image forming apparatus that includes a cleaning unit and a fixing unit that fixes the toner image transferred by the transfer unit to the transfer material and uses fixing oil at the time of fixing, the same polarity as the toner pattern transferred to the transfer unit And a cleaning auxiliary means for mixing the toner pattern transferred in contact with the transfer means and the fixing oil, and after the double-sided printing on the transfer material, the toner pattern creation A predetermined toner pattern is generated on the transfer means by the means, and the fixing oil is removed together with the toner pattern by the cleaning means.

  According to a third aspect of the present invention, in the image forming apparatus according to any one of the first to second aspects, the value of the bias voltage for removing the fixing oil applied to the cleaning auxiliary means is for transfer. The bias voltage is smaller than the value of the applied bias voltage.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the bias voltage for the transfer is applied to the bias voltage when the toner is removed. It is characterized by being performed when not.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the cleaning assisting unit is disposed upstream of the cleaning unit. .

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the execution time of the fixing oil removing operation and the length of the toner pattern to be formed are determined by the transfer to be printed. It is determined based on the length in the conveyance direction of the material.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the execution time of the fixing oil removing operation and the length of the toner pattern to be formed are determined by the transfer to be printed. It is determined based on the type of material.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the execution time of the fixing oil removing operation and the length of the toner pattern to be formed are determined by the image to be formed. It is determined based on the area ratio.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the execution time of the fixing oil removal operation and the length of the toner pattern to be formed depend on environmental conditions. It is determined based on.

  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the cleaning assisting unit includes a brush-like rotating member.

  According to the image forming apparatus of the present invention, the toner of the toner pattern formed by the toner pattern generation unit by the cleaning auxiliary unit enters the transfer oil by the bias voltage, and the transfer oil that has entered the toner is efficiently removed by the cleaning unit. Therefore, it is possible to prevent image defects and filming due to fixing oil adhering to the transfer member.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus of an image forming apparatus. It is sectional drawing which shows a transfer apparatus and a cleaning assistance means. 2 is a block diagram illustrating a control system of the image forming apparatus. FIG. It is a schematic diagram which shows the removal state of the fixing oil which concerns on an Example. 6 is a timing chart showing the timing of fixing oil removal according to an embodiment. It is a timing chart which shows the timing of the fixing oil removal which concerns on a 2nd Example. 12 is a timing chart showing the timing of fixing oil removal according to a third embodiment.

  An image forming apparatus according to the present invention includes an image carrier that carries a toner image on a surface thereof, an intermediate transfer member to which a toner image on the image carrier is transferred, and a toner image on the image carrier that is transferred to the intermediate transfer member. A first transfer means for transferring onto the body, a second transfer means for transferring the toner image on the intermediate transfer body onto a transfer material, a cleaning means for cleaning the surface of the second transfer means, and the second A fixing means for fixing the toner image transferred by the transfer means to the transfer material, and the fixing oil attached to the second transfer means in an image forming apparatus using fixing oil in the fixing means. A toner pattern creating means for creating a toner pattern covering an area including the area; a means for applying a bias voltage having the same polarity as the toner pattern transferred to the second transfer means; and the second transfer means. Cleaning auxiliary means for applying repulsive force to the toner pattern transferred by touch with the bias voltage, and after the double-sided printing on the transfer material, the toner pattern creating means applies a predetermined toner to the second transfer means. A pattern is generated, and the fixing oil is removed together with the toner pattern by the cleaning means.

  According to this example, the toner of the toner pattern formed by the toner pattern generation unit receives the repulsive force from the cleaning auxiliary unit by the bias voltage and enters the transfer oil, and the transfer oil that has entered the toner is efficiently removed by the cleaning unit. Therefore, image defects and filming due to the fixing oil attached to the second transfer member can be prevented.

  The image forming apparatus according to the present invention includes an image carrier that carries a toner image on a surface, a transfer unit that transfers a toner image on the image carrier to a recording material, and a cleaning that cleans the surface of the transfer unit. And a fixing unit that fixes the toner image transferred by the transfer unit to the transfer material. In an image forming apparatus that uses fixing oil at the time of fixing, the same polarity as the toner pattern transferred to the transfer unit A cleaning auxiliary means for mixing the toner pattern transferred in contact with the transfer means and the fixing oil, and a means for applying a bias voltage, and the toner pattern creating means after double-sided printing on the transfer material A predetermined toner pattern is generated on the transfer means, and the fixing oil is removed together with the toner pattern by the cleaning means.

  According to this example, the toner of the toner pattern formed by the toner pattern generation unit by the cleaning assist unit enters the transfer oil by the bias voltage, and the transfer oil that has entered the toner can be efficiently removed by the cleaning unit. Further, it is possible to prevent image defects and filming due to fixing oil adhering to the transfer member.

  In the image forming apparatus according to the present invention, the value of the bias voltage for fixing oil removal applied to the cleaning assisting unit can be smaller than the value of the bias voltage applied for transfer. When the bias voltage to the auxiliary cleaning device for removing the fixing oil becomes larger than the bias voltage for transfer, the transfer condition changes and an image defect occurs. According to this example, it is possible to prevent image defects and filming without causing side effects in transfer.

  In the image forming apparatus according to the present invention, the application of the bias voltage at the time of toner removal can be performed when the bias voltage for the transfer is not applied. When a bias voltage for transfer and a bias voltage to the auxiliary cleaning device for removing fixing oil are applied at the same time, the transfer conditions change and image defects occur. In this example, this can be prevented, and image defects and filming can be prevented without adversely affecting the transfer.

  In the image forming apparatus according to the present invention, the cleaning assisting unit may be disposed upstream of the cleaning unit. During double-sided printing, the fixing oil attached to the paper when the first side passes is attached to the secondary transfer portion when the second side passes, and filming occurs. In this example, even when the amount of fixing oil that wraps around is large, the attached oil can be removed, and image defects and filming can be prevented.

  In the image forming apparatus according to the present invention, the execution time of the fixing oil removing operation and the length of the toner pattern to be formed can be determined based on the length of the transfer material to be printed in the transport direction. The amount of fixing oil adhering to the transfer material varies depending on the length of the transfer material. In this example, since the removal condition is determined based on the length of the transfer material, even if the amount of fixing oil changes depending on the length of the transfer material, the fixing oil removal process corresponding to the change can be performed, and image defects and Filming can be prevented.

  In the image forming apparatus according to the present invention, the execution time of the fixing oil removal operation and the length of the toner pattern to be formed can be determined based on the type of transfer material to be printed. The amount of fixing oil adhering to the transfer material varies depending on the type of transfer material. In this example, the removal conditions are determined based on the type of transfer material, so even if the amount of fixing oil changes depending on the type of transfer material, it is possible to perform fixing oil removal processing corresponding to the change, resulting in image defects and filming. Can be prevented.

  In the image forming apparatus according to the present invention, the execution time of the fixing oil removing operation and the length of the toner pattern to be formed can be determined based on the image area ratio to be formed. The amount of fixing oil adhering to the transfer material varies depending on the image area ratio to be formed. In this example, the removal condition is determined based on the image area ratio to be formed. Therefore, even if the amount of fixing oil changes depending on the image area ratio to be formed, the fixing oil removal process corresponding to the change can be performed. Filming can be prevented.

  In the image forming apparatus according to this example, the execution time of the fixing oil removing operation and the length of the toner pattern to be input can be determined based on environmental conditions. The amount of fixing oil adhering to the transfer material varies depending on environmental conditions. In this example, the removal condition is determined based on this environmental condition. Therefore, even if the amount of fixing oil changes depending on the environmental condition, the fixing oil removal process corresponding to the change is possible, and image defects and filming are prevented. Can do.

  The cleaning assisting unit of the image forming apparatus according to the present invention may include a brush-like rotating member. According to this example, since the toner of the toner pattern and the fixing oil can be mixed with the brush-like rotating member, the fixing oil can be removed more efficiently by the cleaning unit.

  The image forming apparatus according to the embodiment will be described below. FIG. 1 is a cross-sectional view illustrating an image forming apparatus according to an embodiment, and FIG. 2 is a cross-sectional view illustrating a configuration of an image forming unit. The image forming apparatus 100 includes image forming units 6Y, 6C, 6M, and 6K that form yellow (Y), cyan (C), magenta (M), and black (K) toner images, and image forming units 6Y. , 6C, 6M, and 6K image bearing members 1Y, 1C, 1M, and 1K, a writing unit 7 that emits writing light, and toner images of the image forming units 6Y, 6C, 6M, and 6K are transferred. And an intermediate transfer unit 15 for transferring to the recording medium P.

  The image forming unit 6Y includes a photosensitive drum 1, a developing device 62 including a developing roller 61, a cleaner 63 for cleaning the photosensitive drum 1, a charger 64 for charging the photosensitive drum 1, and a static on the photosensitive drum 1. An exposure device for writing an electrostatic latent image is provided. The other image forming units 6Y, 6C, 6M, and 6K have the same configuration as the image forming unit 6Y.

  An intermediate transfer member is provided between the photosensitive drums 1Y, 1C, 1M, and 1K of the image forming units 6Y, 6C, 6M, and 6K and the transfer rollers 9Y, 9C, 9M, and 9K as the first transfer unit. An intermediate transfer belt 8 is disposed. The toner images of the respective colors created by the image forming units 6Y, 6C, 6M, and 6K are synchronously transferred to the intermediate transfer belt 8 to form a color toner image.

  The intermediate transfer belt 8 is wound around a turning roller 18 at a lower portion, and a secondary transfer roller 19 as a second transfer unit is disposed facing the turning roller 18.

  When printing only the first surface, a recording medium such as a sheet placed on the paper feed tray 26 is transported to the registration roller 28 via the transport path K1. Then, the recording medium P transported to the position of the registration roller 28 temporarily stops at the position of the roller nip of the registration roller 28 that has stopped rotating. Then, the registration roller 28 is rotated in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is directed toward the nip portion (transfer position) between the intermediate transfer belt 8 and the secondary transfer roller 19. Be transported. In this way, a desired color image is transferred onto the back surface of the recording medium P using the back surface of the recording medium P as a transfer surface. The recording medium P to which the color toner image has been transferred is fixed by the fixing device 20 and discharged to a discharge tray.

  In the image forming apparatus 100 according to this example, a double-sided printing unit for forming a toner image on the second surface which is the back surface of the recording medium P after the image is transferred and fixed to the first surface of the recording medium P Is installed. That is, the image forming apparatus 100 includes a conveyance path K2 for double-sided printing (indicated by a one-dot chain line in the drawing), a reversing mechanism (forward / reverse reversing roller 29) for reversing and conveying the recording medium P, and the like. is set up.

  When the double-sided printing mode is selected by operating an operation unit (not shown), the recording medium P after the toner image is transferred and fixed on the first surface through the image forming process described above is sent from the fixing device 20. Thereafter, the sheet is guided from the vertical conveyance path toward the forward / reverse reversing roller 29 without being discharged out of the apparatus by an operation of a switching claw (not shown). Thereafter, the recording medium P that has reached the position of the reversing mechanism (the state in which an image is formed on the first surface), the reverse rotation operation of the forward / reverse reversing roller 29, the operation of the switching claw (not shown), After being guided by the horizontal path, the sheet is conveyed toward the position of the registration roller 28.

  Then, the recording medium P transported to the position of the registration roller 28 temporarily stops at the position of the roller nip of the registration roller 28 that has stopped rotating. Then, the registration roller 28 is rotationally driven in time with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the nip portion (transfer position). In this way, a desired color image is transferred onto the back surface of the recording medium P using the back surface of the recording medium P as a transfer surface. Thereafter, the recording medium P with the image transferred on the back surface is discharged outside the apparatus through a fixing process in the fixing device 20. Thereby, the double-sided printing on the recording medium P is completed.

  In such double-sided printing, the fixing oil adheres to the recording medium P when passing through the fixing device 20 during printing on the first side, and the fixing oil is applied when passing through the secondary transfer roller 19 during printing on the second side. It will stick.

  In this example, the secondary transfer roller 19 includes a cleaning blade 40 as a cleaning unit for the secondary transfer roller 19 and a cleaning assisting unit 30 disposed on the upstream side of the cleaning blade 40.

  FIG. 3 is an enlarged cross-sectional view illustrating the secondary transfer roller of the image forming apparatus according to the embodiment. In addition to the cleaning blade, the secondary transfer roller 19 is provided with a cleaning auxiliary means 30 for applying a bias voltage having the same polarity as the toner to the portion of the secondary transfer roller 19 where the fixing oil is attached. The cleaning assisting unit 30 includes a brush member 31 that is rotatably arranged and a power source 32 that applies a bias voltage to the brush member 31. The brush member 31 is rotationally driven by a driving means such as a motor (not shown).

  In this example, the toner pattern is generated at the timing between the sheets, the toner is adhered to the secondary transfer portion to which the fixing oil is adhered, the bias having the same polarity as the toner is applied by the cleaning assisting means 30, and the brush member At 31, both are mixed, and the fixing oil mixed with toner is removed by the cleaning blade 40.

  Next, fixing oil removal processing in the image forming apparatus will be described. FIG. 4 is a block diagram illustrating a control system of the image forming apparatus, and FIG. 5 is a schematic diagram illustrating a fixing oil removal state according to the embodiment. As illustrated in FIGS. 1 and 4, the image forming apparatus 100 includes a toner pattern. A fixing oil removal control means 50 serving as a creation means is arranged. The fixing oil removal control means 50 operates the writing unit 7, the image forming unit 6, the intermediate transfer unit 15 and the cleaning auxiliary means 30 at a predetermined timing, Remove the fixing oil. The fixing oil removal control means 50 can be composed of a microcomputer equipped with a CPU, ROM, RAM, etc., and executes a control program to remove the fixing oil at a predetermined timing. The fixing oil removal control unit 50 can cause the control unit that performs printing control of the image forming apparatus 100 to execute the function.

  The fixing oil removal control means 50 generates writing light for forming a toner pattern at a predetermined timing in the writing unit 7 so as to expose the photosensitive drum 1 (for example, the photosensitive drum 1 of the black image forming unit 6K). Then, a toner image for drawing a toner pattern is generated by the image forming unit 6K and transferred to the intermediate transfer belt 8. This toner pattern is formed so as to correspond to a region where the fixing oil attached to the first surface of the recording medium P fixed by the previous double-sided printing is attached to the secondary transfer roller 19.

  Here, the bias voltage applied by the cleaning assisting unit 30, that is, the toner removal bias value is set so that the transfer bias voltage value is less than the bias voltage value for removing the fixing oil so as not to affect the bias applied at the time of transfer. It is set to be larger. In order to completely eliminate the influence of the bias, it is preferable to apply the toner removal bias only at a timing when the transfer bias is not applied.

  The toner T of the toner pattern transferred to the secondary transfer roller 19 as the second transfer means as such an inter-paper pattern moves to the position where the cleaning assisting means 30 is arranged according to the rotation of the secondary transfer roller 19 and is cleaned. Since the auxiliary unit 30 is applied with a bias having the same polarity as the toner, the auxiliary unit 30 receives a repulsive force (repulsive force) from the cleaning auxiliary unit 30 and, as shown in FIG. 5, the surface direction of the secondary transfer roller 19, that is, the secondary transfer. The toner T acts to move toward the center of the roller 19.

  In this embodiment, since the brush member 31 is disposed in the cleaning assisting means, in addition to the toner moving action by the bias voltage, the brush member 31 comes into contact with the secondary transfer roller 19 and the toner T layer ( The thickness: several μm to several tens of μm) and the fixing oil layer 60 (thickness: several μm to several hundred μm) are stirred. Then, the toner T reaches the cleaning blade 40 while being mixed with the fixing oil layer 60. Here, since the fixing oil mixed with the toner T is easier to be removed by the cleaning blade 40 than the fixing oil alone, the fixing oil layer 60 is efficiently removed together with the mixed toner T. In addition, since a bias having the same polarity as the toner is applied to the cleaning assisting unit, it is possible to prevent a problem that the toner accumulates on the cleaning assisting unit and accumulates as dirt.

  Next, the timing for generating the toner pattern and removing the fixing oil will be described. FIG. 6 is a timing chart showing fixing oil removal timing according to the embodiment. In FIG. 6, each rectangle represents a toner image transferred at the secondary transfer position. In this example, fixing oil adheres to the secondary transfer roller 19 at the time of printing on the second surface (back surface), thereby causing filming. In this example, the toner pattern is formed at the timing when the printing on the second surface is completed. In the example shown in FIG. 6, since printing on both sides (first side, second side) is performed after printing only the first side, a toner pattern is formed after printing on the second side, Fixing oil is removed.

  Here, in parallel with applying the toner removal bias at the timing between the sheets, a toner image for the next printing is generated on the photosensitive drum 1, and further, the toner image is transferred at the nip position with the intermediate transfer belt. If the operation is performed, the fixing oil can be removed between printings, and the overall printing time can be shortened.

  In this case, if the toner removal bias is large, this bias acts on the nip position via the roller, affecting the transfer operation, and image defects such as image dust and white spots may occur in the next image printing. . Therefore, in this example, the value of the bias voltage for fixing oil removal is set smaller than the value of the transfer bias voltage so that the toner removal bias does not adversely affect the transfer.

  The present inventor has experimentally confirmed that if the toner removal bias current is set to a value within 13 percent of the transfer bias current (several μA to several hundred μA), side effects and image defects can be sufficiently prevented. I have confirmed. Therefore, it is desirable to set the toner removal bias current to a magnitude within 13 percent of the transfer bias current. Note that it is desirable to set the magnitude of the toner removal bias current with respect to the transfer bias controlled by constant current.

  Further, in this embodiment, the execution time of the fixing oil removal operation set by the fixing oil removal control means 50 and the length of the toner pattern to be formed are the length in the transport direction of the transfer material to be printed, the transfer material to be printed It can be determined based on the type of the image, the image area ratio to be formed, and the environmental conditions. The execution time and the length of the toner pattern are determined based on these conditions through experiments and the like, stored in the RAM or the like of the fixing oil removal control means 50, and the conditions of the paper to be used are read manually or automatically. decide. By performing such control, it is possible to perform fixing oil removal processing optimal for various conditions, and to prevent image defects and filming.

  Next, the fixing oil removal timing according to the second embodiment will be described. FIG. 7 is a timing chart showing the timing of fixing oil removal according to the second embodiment. In this example, after printing (secondary transfer) on the second surface (back surface), the toner pattern is transferred to the secondary transfer roller 19 within the time until the next printing is started, and transferred to this toner pattern. A toner voltage is transferred to the secondary transfer roller 19 by applying a bias voltage. In this example, the transfer of the toner pattern is completed at time t1, the transfer bias is turned OFF, and then the bias voltage for fixing oil removal by the cleaning assisting means 30 is turned ON at time t2 to remove the fixing oil for a predetermined time. Apply a bias voltage. Next, the bias voltage for fixing oil removal is turned off at time t3, and the transfer bias voltage is turned on at the next printing timing at time t4. In this example, since the application timings of both bias voltages are controlled in this way, the removal bias is not applied during the transfer operation, and there is no problem that causes a side effect on the transfer. Problems with image defects such as image dust and white spots can be reliably prevented.

  Furthermore, the fixing oil removal timing according to the third embodiment will be described. FIG. 8 is a timing chart showing the timing of fixing oil removal according to the third embodiment. In this example, the fixing oil is removed during printing standby after a series of print jobs are completed. That is, after the print job is completed, toner pattern transfer, application of fixing oil removing bias voltage, and fixing oil removal are executed. In this example, since the fixing oil is removed so as to avoid printing, the timing need not be set in detail, and the execution timing can be set with a high degree of freedom. Further, since the bias voltage for fixing oil removal is applied when the transfer operation (printing) is not performed, the problem of image defects such as image dust and white spots can be prevented without adversely affecting the printing conditions.

  In the above embodiment, the image forming apparatus is provided with the secondary transfer device, and the toner image transferred to the secondary transfer belt or the like is transferred to the recording medium P as an example. The present invention can be applied to an image device that directly transfers a toner image formed on a photoconductor to a recording medium. In this case, a cleaning assisting unit may be provided on a transfer body such as a transfer roller disposed to face the image carrier, and the same processing as in the above-described embodiment may be performed.

1Y, 1C, 1M, 1K Photosensitive drums 6Y, 6C, 6M, 6K Image forming unit 7 Writing unit 8 Intermediate transfer belt 9Y, 9C, 9M, 9K Transfer roller 15 Intermediate transfer unit 18 Turning roller 19 Secondary transfer roller 20 Fixing device 26 Paper feed tray 28 Registration roller 29 Forward / reverse reversing roller 30 Cleaning auxiliary means 31 Brush member 32 Power supply 40 Cleaning blade 50 Fixing oil layer 60 Fixing oil removal control means 61 Developing roller 62 Developing device 63 Cleaner 64 Charger 100 Image Forming equipment

JP 2000-275988 A JP 2000-137403 A

Claims (10)

An image carrier that carries a toner image on its surface, an intermediate transfer member to which the toner image on the image carrier is transferred, and a first transfer that transfers the toner image on the image carrier onto the intermediate transfer member Means, a second transfer means for transferring the toner image on the intermediate transfer member to a transfer material, a cleaning means for cleaning the surface of the second transfer means, and a toner image transferred by the second transfer means. Fixing means for fixing to the transfer material,
In the image forming apparatus using fixing oil in the fixing unit,
A toner pattern creating means for creating a toner pattern that covers an area including an adhesion area of the fixing oil adhered to the second transfer means;
A cleaning unit that includes a unit that applies a bias voltage having the same polarity as the toner pattern transferred to the second transfer unit and that applies a repulsive force to the toner pattern transferred in contact with the second transfer unit with the bias voltage. An auxiliary means,
After double-sided printing on the transfer material, the toner pattern creating unit generates a predetermined toner pattern on the second transfer unit, and the cleaning unit removes the fixing oil together with the toner pattern. Image forming apparatus. An image carrier that carries a toner image on the surface, a transfer unit that transfers a toner image on the image carrier to a recording material, a cleaning unit that cleans the surface of the transfer unit, and a toner that is transferred by the transfer unit Fixing means for fixing the image to the transfer material,
In an image forming apparatus that uses fixing oil during fixing,
A cleaning auxiliary means for mixing the toner pattern transferred in contact with the transfer means and a fixing oil, and a means for applying a bias voltage having the same polarity as the toner pattern transferred to the transfer means;
An image forming apparatus, wherein after the double-side printing on the transfer material, a predetermined toner pattern is generated on the transfer unit by the toner pattern creating unit, and the fixing oil is removed together with the toner pattern by the cleaning unit.   3. A bias voltage value for removing fixing oil applied to the cleaning assisting unit is smaller than a bias voltage value applied for transfer. The image forming apparatus described.   4. The image forming apparatus according to claim 1, wherein the bias voltage is applied when the toner is removed when the bias voltage for the transfer is not applied. 5. .   The image forming apparatus according to claim 1, wherein the cleaning assisting unit is disposed on an upstream side of the cleaning unit.   The execution time of the fixing oil removing operation and the length of the toner pattern to be formed are determined based on the length of the transfer material to be printed in the conveyance direction. The image forming apparatus according to claim 1.   The execution time of the fixing oil removing operation and the length of the toner pattern to be formed are determined based on the type of transfer material to be printed. The image forming apparatus described.   The execution time of the fixing oil removing operation and the length of a toner pattern to be formed are determined based on an image area ratio to be formed. Image forming apparatus.   9. The image formation according to claim 1, wherein an execution time of the fixing oil removal operation and a length of a toner pattern to be formed are determined based on environmental conditions. apparatus. The image forming apparatus according to claim 1, wherein the cleaning assisting unit includes a brush-like rotating member.