JP2006350161A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To clean a secondary transfer member for secondarily transferring a toner image formed on an intermediate transfer member to a recording medium while suppressing the shortening of the life of consumption articles such as an image carrier in an image forming apparatus for secondarily transferring the toner image formed on the surface of the intermediate transfer member to the recording medium. <P>SOLUTION: In the printing operation of the image forming apparatus, cleaning reverse-polarity voltage with reverse polarity of the polarity of transfer voltage is applied to the secondary transfer member 5 for time T1 in a time band before a recording medium S rushes into a nip part N between the intermediate transfer member 4 and the secondary transfer member 5, and then cleaning voltage application processing for applying the same-polarity voltage for cleaning with the same polarity as the transfer voltage to the secondary transfer member 5 for time T2 is performed at least once. Then the voltage with the reverse polarity of the polarity of the transfer voltage is applied to the secondary transfer member 5 until the recording medium S rushes into the nip part N between the intermediate transfer member 4 and the secondary transfer member 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer, and in particular, primarily transfers a toner image formed on an image carrier onto the surface of a traveling intermediate transfer member. The present invention relates to an image forming apparatus that secondarily transfers the toner image to a recording medium.

  As an image forming apparatus of a type that primarily transfers a toner image formed on an image carrier onto the surface of a traveling intermediate transfer member and secondarily transfers the toner image on the intermediate transfer member to a recording medium. Examples include a so-called four-cycle type color image forming apparatus and a tandem type color image forming apparatus.

  In a four-cycle color image forming apparatus, a yellow developing device, a magenta developing device, a cyan developing device, and a black developing device are provided in this order, for example, on an image carrier such as a photosensitive drum or a photosensitive belt. In addition, an image exposure device and an intermediate transfer member (generally an endless intermediate transfer belt that is driven to rotate and travels on the surface) are also provided.

  In such a four-cycle color image forming apparatus, when a full-color image is formed using all of the four-color developing devices, an electrostatic for yellow color is applied from the image exposure device onto the image carrier. A latent image is formed and developed by a yellow developing device to form a yellow toner image, and the yellow toner image is primarily transferred from the image carrier onto the intermediate transfer member. Further, following the formation of the yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially formed in the same manner, and these are sequentially primary-transferred on the surface of the intermediate transfer member. Thus, the multiple toner image primarily transferred onto the intermediate transfer member is secondarily transferred onto the recording medium by the secondary transfer member, and is fixed to the recording medium.

  In a tandem color image forming apparatus, a yellow image forming unit, a magenta image forming unit, a cyan image forming unit, and an intermediate transfer member (generally an endless intermediate transfer belt that is rotationally driven and travels on the surface) The black image forming units are arranged in this order, for example, and each image forming unit includes an image carrier such as a photoconductor, an image exposure device for each color, a developing device for each color, and the like.

  In such a tandem type color image forming apparatus, taking a case where a full color image is formed using all of the four color image forming units, a yellow toner image is formed on the intermediate transfer member on the yellow image forming unit. In the magenta image forming unit, a magenta toner image is formed and primary-transferred onto the intermediate transfer member so as to overlap the yellow toner image. Similarly, the cyan image forming unit converts the cyan toner image into a black image. A black toner image is formed by the forming unit, and is primarily transferred onto the intermediate transfer member so as to overlap the preceding toner image. Thus, the multiple toner image primarily transferred onto the intermediate transfer member is secondarily transferred onto the recording medium by the secondary transfer member, and is fixed to the recording medium.

  The secondary transfer member in the image forming apparatus that forms a toner image on the surface of the intermediate transfer member in this way and secondary-transfers the toner image onto the recording medium by the secondary transfer member is a rotating member such as a roller. Thus, a recording medium that presses the recording medium from its back side to the intermediate transfer member and conveys the recording medium together with the intermediate transfer member is widely adopted.

  When the toner image on the intermediate transfer member is secondarily transferred to the recording medium using the secondary transfer member, a transfer voltage (a polarity opposite to the normal charging polarity of the toner in the toner image) is applied to the secondary transfer member. Transfer voltage) is applied.

  By the way, in the image forming apparatus in which the toner image is formed on the surface of the intermediate transfer member and secondarily transferred onto the recording medium by the secondary transfer member as described above, the time is not during the secondary transfer processing of the toner image. In addition, the surface of the secondary transfer member directly contacts the surface of the intermediate transfer member. After the secondary transfer, the transfer residual toner that may remain on the surface of the intermediate transfer member is usually removed by a cleaning device. However, the surface portion of the intermediate transfer member that is still in direct contact with the secondary transfer member The toner may adhere to the surface. Such toner is transferred to the surface of the secondary transfer member, and then when the secondary transfer member comes into contact with the back surface of the recording medium in order to secondary transfer the toner image to the recording medium, the back surface of the recording medium is soiled. .

  In this regard, for example, Japanese Patent No. 2687786 discloses toner image formation for a transfer roller that transfers a toner image onto a recording medium from a toner image forming body (for example, a photoreceptor or an intermediate transfer member) on which a toner image is formed. After transferring the toner image from the body to the recording medium, the toner of the normal charging polarity attached on the transfer roller is moved to the toner image forming body by applying a voltage having a polarity opposite to the normal transfer voltage to the transfer roller, Next, it is disclosed that a normal transfer voltage is applied to the transfer roller to move the reverse polarity charged toner attached to the transfer roller to the toner image forming body, thereby cleaning the transfer roller.

Japanese Patent No. 2687786

  However, according to the transfer roller cleaning method disclosed in Japanese Patent No. 2687786, application of a voltage having a polarity opposite to the normal transfer voltage to the transfer roller and subsequent application of the normal transfer voltage for cleaning It is performed when the forming apparatus is turned on, when the apparatus cover is reclosed after the jam processing, and when the punching operation is completed.

  When the image forming apparatus is turned on, when the cover of the apparatus is reclosed after jamming, and when the transfer roller cleaning for the transfer roller cleaning at the end of the purge operation is longer than that when the transfer roller cleaning is not performed. Accordingly, the drive time of consumables such as a toner image forming body (for example, a photosensitive drum or an intermediate transfer member) becomes longer than that when no transfer roller cleaning is performed. The life of these consumables is shortened accordingly.

  Accordingly, the present invention provides an image forming apparatus that primarily transfers a toner image formed on an image carrier onto the surface of a traveling intermediate transfer member, and secondarily transfers the toner image on the intermediate transfer member to a recording medium. There is provided an image forming apparatus capable of cleaning a secondary transfer member for secondary transfer of a toner image on the intermediate transfer member to a recording medium while suppressing the shortening of consumables such as an image carrier. This is the issue.

In order to solve the above problems, the present invention provides:
An image forming apparatus that primarily transfers a toner image formed on an image carrier onto the surface of a traveling intermediate transfer member, and secondarily transfers the toner image on the intermediate transfer member to a recording medium.
A secondary transfer member for secondary transfer of a toner image on the intermediate transfer member to the recording medium, the recording medium being pressed together with the intermediate transfer member while pressing the recording medium from the back side to the surface of the intermediate transfer member. A rotatable secondary transfer member for conveying a medium;
A transfer voltage for secondary transfer of the toner image on the intermediate transfer member to the recording medium to the secondary transfer member, a cleaning reverse polarity voltage having a polarity opposite to the transfer voltage, or a cleaning having the same polarity as the transfer voltage A voltage application device for a secondary transfer member capable of applying the same polarity voltage;
A control unit of the voltage application device for the secondary transfer member,
In the printing operation of the image forming apparatus, the control unit applies the cleaning reverse polarity voltage to the secondary transfer member in a time zone before the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member. Is applied for a period of time T1, and then the cleaning voltage application process in which the same polarity voltage for cleaning is applied to the secondary transfer member for a period of time T2 is performed at least once. Provided is an image forming apparatus that controls the secondary transfer member voltage application device so that a voltage having a polarity opposite to the transfer voltage is applied to the secondary transfer member until it enters the nip portion with the transfer member. To do.

According to this image forming apparatus, in the printer operation of the image forming apparatus, in other words, when one or more of consumables such as an image carrier must be driven to execute the printing operation, 2 The cleaning voltage application process is performed on the secondary transfer member. After that, until the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member, the secondary transfer member has a polarity opposite to the transfer voltage. A voltage is applied.
Therefore, as compared with the case where the cleaning process of the secondary transfer member is executed when the power of the image forming apparatus is turned on, when the apparatus cover is reclosed after the jam processing, or when the purge operation is completed as in the conventional case, the secondary transfer is performed. Prolonging the drive time of consumables such as the image carrier for cleaning the member is suppressed, and the secondary transfer member can be cleaned while suppressing the shortening of the life of the consumables.

  In the image forming apparatus according to the present invention, the secondary transfer member is cleaned during the purge operation of the image forming apparatus before the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member. Therefore, the image formation is not hindered.

  When cleaning, a reverse polarity voltage for cleaning having a polarity opposite to the transfer voltage (that is, a voltage having the same polarity as the normal charging polarity of the toner) is applied to the secondary transfer member for a time T1 to adhere to the secondary transfer member. The toner charged to the normal charging polarity that may have moved to the intermediate transfer member. After that, the same polarity voltage for cleaning having the same polarity as the transfer voltage is applied to the secondary transfer member for a time T2, so that the toner charged to the reverse polarity that may be attached to the secondary transfer member is also intermediately transferred. Move to the member. Thus, the secondary transfer member is cleaned before the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member.

Further thereafter, a voltage having a polarity opposite to the transfer voltage is applied to the secondary transfer member until the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member. In addition, the adhesion of toner from the intermediate transfer member to the secondary transfer member is suppressed.
Thus, the toner contamination on the back surface of the recording medium can be suppressed accordingly.

  Here, “until the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member” also includes “until the recording medium immediately enters the nip portion”. The case of “until starting to enter the nip portion (more specifically, until a part of the margin portion outside the image forming area of the recording medium starts to enter the nip portion)” is included.

The same polarity voltage for cleaning may be the same as or different from the transfer voltage.
In addition, after the cleaning voltage application process is performed at least once, a voltage having a polarity opposite to the transfer voltage applied until the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member is the reverse voltage for cleaning. The same voltage as the polar voltage may be used.

  In the cleaning voltage application process, the time T1 for applying the reverse polarity voltage for cleaning to the secondary transfer member and the time T2 for applying the same polarity voltage for cleaning to the secondary transfer member are set so that desired cleaning of the secondary transfer member is performed. Depending on the forming apparatus or the like, it can be determined in advance by experiments or the like.

  In addition, the number of times of performing the cleaning voltage application process in which the reverse polarity voltage for cleaning is applied to the secondary transfer member for the time T1, and then the same polarity voltage for cleaning is applied to the secondary transfer member for the time T2 is also secondary. It can be determined in advance by experiments or the like according to the image forming apparatus or the like so that the transfer member can be cleaned as desired.

In terms of the number of times the cleaning voltage application process is performed, the controller performs the cleaning voltage application process at least once on the secondary transfer member voltage application device according to the contamination factor of the secondary transfer member. You may adopt what you want.
Here, the “contamination factor of the secondary transfer member” is a factor of contamination of the secondary transfer member due to toner adhesion, and a representative example is jam (recording medium clogging). When a jam occurs, the printing operation is interrupted, and so-called post-processing at the end of the printing operation is not performed, so that the intermediate transfer member or the image carrier is soiled with toner that has not been consumed by printing, Since there is a residual potential on the top, the time required for the process pre-processing in the printing operation becomes longer and the toner contamination of the secondary transfer member also increases. The number of times of applying the cleaning voltage to the next transfer member may be increased.

  Therefore, the control unit adopts whether or not the jam processing before the printing operation is performed as a contamination factor of the secondary transfer member, and when the jam processing is performed before the printing operation, the secondary transfer member When the cleaning voltage application processing is performed a plurality of times by the voltage application device for the toner and the jam processing is not performed, the cleaning voltage application processing is performed on the voltage application device for the secondary transfer member and the jam processing is performed. The number of times may be less than the number of times the

  As described above, according to the present invention, the toner image formed on the image carrier is primarily transferred onto the traveling intermediate transfer member surface, and the toner image on the intermediate transfer member is secondarily transferred to the recording medium. An image forming apparatus capable of cleaning a secondary transfer member for secondary transfer of a toner image on the intermediate transfer member to a recording medium while suppressing shortening of consumables such as an image carrier. A forming apparatus can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an image forming apparatus according to the present invention.
The image forming apparatus shown in FIG. 1 is a tandem type full color printer. This printer has an endless intermediate transfer belt 4 wound around a driving roller 31 and a roller 32 facing the driving roller 31. The transfer belt 4 can be driven to rotate counterclockwise (in the direction of the arrow in the figure) by a driving roller 31 that is driven to rotate by an intermediate transfer belt drive unit 4D (see FIG. 2).

The counter roller 32 faces a cleaner CL for cleaning secondary transfer residual toner and the like on the transfer belt 4, and the drive roller 31 faces the secondary transfer roller 5.
The surface layer portion of the secondary transfer roller 5 is formed of an elastic material, and is pressed against the intermediate transfer belt 4 by pressing means (not shown) to form a nip portion N between the intermediate transfer belt 4 and the intermediate transfer belt. 4 or according to the movement of the recording medium S fed into the nip portion N as will be described later. A voltage such as a transfer voltage can be applied to the secondary transfer roller 5 from a secondary transfer roller voltage application device PW (see FIG. 2).

  A fixing device 6 is disposed above the intermediate transfer belt 4 and the secondary transfer roller 5, a timing roller pair 70 is disposed below, and a recording medium such as recording paper is accommodated below the fixing device 6. A recording medium accommodation cassette 8 is arranged.

The fixing device 6 includes a fixing roller 61 incorporating a heat source such as a halogen lamp heater (not shown) and a pressure roller 62 pressed against the fixing roller 61.
The recording medium S accommodated in the recording medium accommodating cassette 8 can be pulled out one by one by the medium supply roller 81 at a predetermined timing and supplied to the timing roller pair 70.

A pre-timing roller sensor SE1 for detecting the recording medium S is disposed on the entrance side of the timing roller pair 70.
When the recording medium S starts to be supplied by the roller 81, the medium supply sensor SE2 detects this.

  A discharge tray T for discharging the recording medium S on which an image has been formed is disposed above the intermediate transfer belt 4. The image-formed recording medium S coming out of the fixing device 6 can be transported by the transport roller pair 71 and discharged onto the discharge tray T by the discharge roller pair 72. On the exit side of the discharge roller pair 72, a discharge sensor SE3 for detecting the discharge of the recording medium is provided.

  Between the rollers 31 and 32 around which the intermediate transfer belt 4 is wound, a yellow image forming unit Y, a magenta image forming unit M, and a cyan image forming unit C are arranged along the transfer belt 4 from the rollers 32 to 31. And the black image forming portion K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photoconductor 11 as an electrostatic latent image carrier, and a charging device 12, an image exposure device 13, and a developing device 14 are provided around the photoconductor. The primary transfer roller 2 and the cleaner 15 for removing the primary transfer residual toner and the like on the photosensitive member are arranged in this order. The primary transfer roller 2 faces the photoreceptor 1 with the transfer belt 4 in between. The exposure device 13 can perform image exposure on the photoconductor 11 using a laser beam in accordance with image information provided from a personal computer (not shown).

  The developing device 14 in each image forming unit is not limited thereto, but in this example, a negatively chargeable toner is used, and the electrostatic latent image formed on the photoconductor 11 is developed with a developing bias applied thereto. Reversal development can be performed by the roller 141.

  FIG. 2 shows an outline of the control circuit of this printer. This circuit includes a control unit Cont that controls the overall operation of the printer. The control unit Cont includes an operation panel PA, a timing roller front sensor SE1, a medium supply sensor SE2, a discharge sensor SE3, Y, M, C, and K image forming units, an intermediate transfer belt drive unit 4D, and a secondary transfer roller voltage. The application device PW is connected, and the controller Cont also receives various information and signals necessary for printer operation control from a portion not shown, and also displays various information and signals necessary for printer operation control. Output to the omitted part.

  A driving motor (not shown) for the photoreceptor 11 in each of the image forming units Y, M, C, and K, a charging voltage applying device for the charging device 12, a driving motor for the developing roller 14 of the image exposure device 13 and the developing device 14 ( The developing bias applying device (not shown), the intermediate transfer belt driving unit 4D, the secondary transfer roller voltage applying device PW, and the like operate at a predetermined timing based on an instruction from the control unit Cont. Cleaning control of the secondary transfer roller 5 to be described later is performed under the instruction of the control unit Cont. A control unit of the voltage application device PW for cleaning the secondary transfer roller 5 is included in the control unit Cont.

According to this printer, an image is formed as follows under the instruction of the control unit Cont.
When the power is turned on, initial processing such as making the surface potential of the photoconductor 11 uniform in each image forming unit and setting the fixing device 6 to a fixing temperature is performed, and a standby state for a printing operation is set. Is done.

  In this standby state, when the user gives a print start instruction by operating the print start key on the operation panel PA (FIG. 2), the print operation starts. In this printing operation, first, pre-process processing is performed, and charging of the photosensitive member 11 of each image forming unit is started by the charging device 12, and the surface potential of the photosensitive member is stabilized. Next, an image forming process is entered. Image forming is performed using one or more of the Y, M, C, and K image forming units.

  Taking a case where a full color image is formed using all of the image forming portions Y, M, C and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is primarily transferred onto the transfer belt 4. Is done.

  That is, in the yellow image forming unit Y, the photosensitive member 11 is rotationally driven in the clockwise direction in the drawing, and the image exposure device is applied to the charged area of the photosensitive member 11 whose surface is uniformly charged to a predetermined potential by the charging device 12. 13, yellow image exposure is performed, and a yellow electrostatic latent image is formed on the photoreceptor 11. This electrostatic latent image is developed by a developing roller 141 to which a developing bias of a developing device 14 having yellow toner is applied to become a visible yellow toner image, and the toner image is transferred onto the transfer belt 4 by the primary transfer roller 2. Transcribed. At this time, a primary transfer voltage is applied to the primary transfer roller 2 from a power source (not shown).

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 4, a cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 4, and in the black image forming unit K. A black toner image is formed and transferred to the transfer belt 4.

Yellow, magenta, cyan, and black toner images are formed at the timing when these toner images are transferred onto the intermediate transfer belt 4 in an overlapping manner.
Thus, the multiple toner image formed on the transfer belt 4 moves toward the secondary transfer roller 5 by the rotation of the transfer belt 4.

  On the other hand, the recording medium S is pulled out from the recording medium storage cassette 8 by the medium supply roller 81 and supplied to the timing roller pair 70. Here, the recording medium S is detected by the pre-timing roller sensor SE1. The recording medium S normally reaches the timing roller pair 70 and waits at the end of the pre-process.

  Thus, the recording medium S waiting at the timing roller pair 70 is supplied to the nip portion N between the transfer belt 4 and the secondary transfer roller 5 in accordance with the multiple toner image sent by the intermediate transfer belt 4. The multiple toner images are secondarily transferred onto the recording medium S by the secondary transfer roller 5 to which the transfer voltage is applied from the voltage application device PW under the instruction of the control unit Cont. Thereafter, the recording medium S is passed through the fixing device 6 where the multiple toner images are fixed on the recording medium S under heat and pressure. The recording medium S is continuously discharged to the discharge tray T by the conveying roller pair 71 and the discharge roller pair 72.

  When the trailing edge of the recording medium S exits the fixing device 6, processing at the end of printing (post-processing) such as equalizing the photoreceptor surface potential of each image forming unit is performed, and thus the post-processing is also completed. Thus, when a series of printing operations are completed, the photosensitive member driving motors and the like of the respective image forming units are stopped.

  As described above, an image is formed. In this image forming apparatus, more accurately speaking, using the time zone for the process pre-processing and the like in the print operation, the print operation and the recording medium Is transferred to the nip N between the intermediate transfer belt 4 and the secondary transfer roller 5 under the control of the secondary transfer roller voltage application device PW by the controller Cont. Is cleaned, and toner contamination on the back surface of the recording medium S is suppressed.

The secondary transfer roller cleaning control by the controller Cont will be described based on the flowchart of FIG.
When the process pre-process in the printing operation is started, first, the cleaning number N is initialized to 0 (step S1). Next, a reverse polarity voltage for cleaning having a polarity opposite to that of the transfer voltage is applied from the voltage application device PW to the transfer roller 5 for a time T1 that has been determined in advance by experiments or the like. The toner charged to the regular charging polarity that may be present is moved to the transfer belt 4 and cleaning is performed to remove the toner (S2, S3).

Subsequently, a cleaning same polarity voltage having the same polarity as the transfer voltage (in this example, the same voltage as the transfer voltage) is applied from the voltage application device PW to the transfer roller 5 for a time T2 that is predetermined by experiment or the like. As a result, the toner charged to a polarity opposite to the normal charging polarity that may adhere to the transfer roller 4 is moved to the transfer belt 4 and cleaning is performed to remove the toner (S4, S5).
Here, the times T1 and T2 are times required for at least one rotation of the transfer roller 5, respectively. Further, the control unit Cont has a measuring unit that measures the times T1, T2, and the like, and the measuring unit can measure the times T1, T2, a time T3 described later, and the like.

  When the cleaning voltage application process is completed once, the number of cleanings is incremented by 1 (S6), and the presence / absence of a jam history is checked (S7). When a jam occurs, the printing operation is interrupted, and so-called post-process processing at the end of the printing operation is not executed, so that the intermediate transfer belt 4 and the photoreceptor 11 of the image forming unit are contaminated with toner that is not consumed in printing. In addition, because there is a residual potential on the photoconductor 11, the time required for the process pre-processing in the next printing operation becomes longer and the toner contamination of the secondary transfer roller 5 also increases.

Therefore, when there is no jam history, the process proceeds to step 9; however, when there is a jam history, the cleaning pre-treatment time applied to the secondary transfer roller 5 is set to two times by using the preprocess time that has become longer. Step S2 to S8 are repeated once again, and the process proceeds to Step 9.
In step S <b> 9, application of a voltage having a reverse polarity to the transfer voltage (in this example, the same voltage as the above-described reverse polarity voltage for cleaning) is started again to the secondary transfer roller 5. As a result, the toner is prevented from adhering again from the transfer belt 4 to the secondary transfer roller 5.

  The presence / absence of the jam processing history is determined by, for example, the controller Cont measuring the elapsed time since the medium supply sensor SE2 facing the medium supply roller 81 is turned on, and the elapsed time is the sensor before the timing roller after the sensor SE2 is turned on. When it becomes longer than the normal time until SE1 is turned on, it is detected that a medium jam (jam) has occurred, and the jam history is stored in the control unit Cont.

After applying a voltage having a polarity opposite to the transfer voltage to the secondary transfer roller 5 in step 9, whether or not the timing roller pre-sensor SE1 is turned on, that is, whether the recording medium S has arrived at the timing roller pair 70 or not. When it is determined that the sensor SE1 is turned on, a voltage having a polarity opposite to the transfer voltage is continuously applied to the secondary transfer roller 5 for a time T3, and then the transfer is performed. Application of a transfer voltage for secondary transfer of the toner image on the belt 4 to the recording medium S is started to the transfer roller 5 (S9 to S12).
Here, the time T3 is a time required for the recording medium to enter the nip portion N between the intermediate transfer belt 4 and the secondary transfer roller 5 from the timing roller pair 70.

Next, when the time T4 elapses after the timing roller pre-sensor SE1 is turned off, the voltage having the opposite polarity to the transfer hand voltage is again applied to the transfer roller 5 (in this example, the same voltage as the voltage applied in step S9). (S15), the presence or absence of the next recording medium is checked, and if there is a next recording medium, steps S10 to S16 are repeated, and if not, the control is terminated as it is (S16).
This time T4 is the time required for the trailing edge of the recording medium S to leave the fixing roller 6 after leaving the timing roller pair 70.

According to the cleaning process of the secondary transfer roller 5 described above, in the print operation of the image forming apparatus, in other words, the consumables such as the photosensitive member 11 are executed for the printing operation regardless of the cleaning of the secondary transfer roller 5. When one or more of them must be driven, a cleaning voltage is applied to the secondary transfer roller 5.
Therefore, as compared with the case where the cleaning process of the secondary transfer member is executed when the power of the image forming apparatus is turned on, when the apparatus cover is reclosed after the jam processing, or when the purge operation is completed as in the conventional case, the secondary transfer is performed. Prolonging the drive time of consumables such as the photoconductor 11 for cleaning the roller 5 is suppressed, and the secondary transfer roller 5 can be cleaned while suppressing the shortening of the life of the consumables.

  The present invention relates to an image forming apparatus for transferring a toner image on an intermediate transfer member onto a recording medium using a secondary transfer member, and cleaning the secondary transfer member to remove consumables such as an image carrier. It can be used to implement while suppressing shortening of life.

1 is a diagram illustrating a schematic configuration of an example of an image forming apparatus (printer) according to the present invention. FIG. 2 is a block diagram illustrating an outline of an operation control circuit of the image forming apparatus in FIG. 1. 6 is a flowchart illustrating an example of secondary transfer roller cleaning control.

Explanation of symbols

Y Yellow image forming portion M Magenta image forming portion C Cyan image forming portion K Black image forming portion 11 Photoconductor 12 Charging device 13 Image exposing device 14 Developing device 141 Developing roller 2 Primary transfer roller 31 Driving roller 32 Opposing roller 4 Intermediate transfer Belt CL Cleaner 5 Secondary transfer roller 6 Fixing device 61 Fixing roller 62 Pressure roller 70 Timing roller pair 71 Conveying roller pair 72 Discharge roller pair T Discharge tray 8 Recording medium storage cassette 81 Medium supply roller SE1 Timing roller pre-sensor SE2 Medium Supply sensor SE3 Discharge sensor 4D Intermediate transfer belt drive unit PW Secondary transfer roller voltage application device PA Operation panel

Claims (3)

An image forming apparatus that primarily transfers a toner image formed on an image carrier onto the surface of a traveling intermediate transfer member, and secondarily transfers the toner image on the intermediate transfer member to a recording medium.
A secondary transfer member for secondary transfer of a toner image on the intermediate transfer member to the recording medium, the recording medium being pressed together with the intermediate transfer member while pressing the recording medium from the back side to the surface of the intermediate transfer member. A rotatable secondary transfer member for conveying a medium;
A transfer voltage for secondary transfer of the toner image on the intermediate transfer member to the recording medium to the secondary transfer member, a cleaning reverse polarity voltage having a polarity opposite to the transfer voltage, or a cleaning having the same polarity as the transfer voltage A voltage application device for a secondary transfer member capable of applying the same polarity voltage;
A control unit of the voltage application device for the secondary transfer member,
In the printing operation of the image forming apparatus, the control unit applies the cleaning reverse polarity voltage to the secondary transfer member in a time zone before the recording medium enters the nip portion between the intermediate transfer member and the secondary transfer member. Is applied for a period of time T1, and then the cleaning voltage application process in which the same polarity voltage for cleaning is applied to the secondary transfer member for a period of time T2 is performed at least once, and then the recording medium is transferred to the intermediate transfer member and the secondary transfer member. The secondary transfer member voltage application device is controlled so that a reverse polarity voltage opposite to the transfer voltage is applied to the secondary transfer member until it enters the nip portion with the transfer member. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the control unit causes the secondary transfer member voltage application device to perform the cleaning voltage application process at least once according to a contamination factor of the secondary transfer member.   The control unit adopts whether or not jam processing is performed before the printing operation as a contamination factor of the secondary transfer member, and when the jam processing is performed before the printing operation, the voltage for the secondary transfer member When the cleaning device has been subjected to the cleaning voltage application process a plurality of times, and the jam processing has not been performed, the cleaning voltage application processing has been performed on the secondary transfer member voltage application device, and the jam processing has been performed. The image forming apparatus according to claim 2, wherein the image forming apparatus is executed less than the number of times.