JP6780569B2 - Image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile. In particular, after primary transferring a toner image formed on an image carrier to an intermediate transfer belt, the present invention further transfers the toner image from the intermediate transfer belt to a recording medium. The present invention relates to an intermediate transfer type image forming apparatus that secondarily transfers a toner image on the top.

Conventionally, an endless intermediate transfer belt that is rotated in a predetermined direction and a plurality of image forming portions provided along the intermediate transfer belt are provided, and each image forming portion puts a toner image of each color on the intermediate transfer belt. An intermediate transfer type image forming apparatus is known in which images are sequentially superposed and first-transferred, and then secondarily transferred onto a recording medium.

In the intermediate transfer type image forming apparatus, when the intermediate transfer belt has an elastic layer, a cleaning brush (cleaning member) that mechanically and electrically recovers the toner remaining on the surface of the intermediate transfer belt and toner are removed from the cleaning brush. A cleaning device equipped with a recovery roller for collecting, a scraper for scraping toner from the surface of the recovery roller, and a transport spiral for transporting the toner scraped from the surface of the recovery roller to a waste toner recovery container is used. There are many.

In the configuration provided with the cleaning brush, the residual toner after the secondary transfer is accumulated in the cleaning brush when the intermediate transfer belt is stopped. This residual toner has a broad charge distribution in which both positive and negative polarities exist. Therefore, when printing is started in this state, there is a problem that the negatively charged (backcharged) toner accumulated in the cleaning brush is transferred to the intermediate transfer belt at the moment when the voltage is applied to the cleaning brush. In particular, when the time from the start of driving the intermediate transfer belt to the start of image formation is short, the toner transferred from the cleaning brush onto the intermediate transfer belt overlaps the first image transfer region on the intermediate transfer belt, and is lateral to the image transfer area. Band-shaped image stains occur.

Therefore, a method of suppressing the movement of toner from the cleaning member to the intermediate transfer belt at the start of image formation has been proposed, and Patent Document 1 describes the rotational movement of the intermediate transfer belt and the rotational drive of the brush roller (cleaning member). And the application of the cleaning voltage are started at the same time, and an image forming apparatus is disclosed in which the rotation speed at the start of rotation of the brush roller is made smaller than the rotation speed at the time of recovery operation.

Japanese Unexamined Patent Publication No. 2015-25950

However, even when the rotation speed at the start of rotation of the cleaning member is made smaller than the rotation speed at the time of recovery operation as in Patent Document 1, the back-charged toner is transferred from the cleaning member to the intermediate transfer belt depending on the timing of applying the cleaning voltage. The phenomenon occurs.

Further, a pre-brush (pre-cleaning member) is provided which is arranged on the upstream side of the cleaning member with respect to the rotation direction of the intermediate transfer belt and aligns the polarity of the residual toner on the intermediate transfer belt by applying a voltage having the same polarity as the toner. In the configuration, when a voltage having the same polarity as the toner is applied to the prebrush, a phenomenon occurs in which the positively charged toner accumulated in the prebrush is transferred to the intermediate transfer belt.

In view of the above problems, the present invention provides an image forming apparatus capable of suppressing the occurrence of image stains due to the toner adhering to the cleaning member retransferring onto the intermediate transfer belt in the intermediate transfer type image forming apparatus. The purpose is.

In order to achieve the above object, the first configuration of the present invention includes an image carrier, an intermediate transfer belt, a primary transfer member, a secondary transfer member, a cleaning member, a power supply device, a drive device, and control. It is an image forming apparatus provided with a unit. A toner image is formed on the image carrier. The intermediate transfer belt is endless and is placed adjacent to the image carrier. The primary transfer member is arranged so as to face the image carrier with the intermediate transfer belt interposed therebetween, and the toner image formed on the image carrier is primarily transferred onto the intermediate transfer belt. The secondary transfer member contacts the intermediate transfer belt to form a secondary transfer nip portion, and the toner image primaryly transferred on the intermediate transfer belt is secondarily transferred to a recording medium passing through the secondary transfer nip portion. The cleaning member cleans the residual toner on the intermediate transfer belt. The power supply applies a cleaning voltage of the opposite polarity to the toner to the cleaning member. The drive device rotates and drives the intermediate transfer belt. The control unit controls the drive device and the power supply device. The control unit rotates and drives the intermediate transfer belt at the start of image formation, and sets the cleaning voltage to 0 or the first voltage until the first image transfer region on the intermediate transfer belt passes through the cleaning member. Raises the cleaning voltage to a second voltage higher than the first voltage after passing through the cleaning member.

According to the first configuration of the present invention, by adjusting the timing and voltage value of applying the cleaning voltage to the cleaning member at the start of image formation, the toner accumulated in the cleaning member is transferred to the first sheet on the intermediate transfer belt. It can be moved to a position that does not overlap with the image transfer area. Therefore, it is possible to effectively prevent image stains on the first printed sheet.

Sectional drawing which shows the schematic structure of the color printer 100 which concerns on one Embodiment of this invention. Side sectional view showing the configuration around the intermediate transfer unit 30 mounted on the color printer 100. Block diagram showing the control path of the color printer 100 A timing chart showing on / off control of the cleaning voltage and the prebrush voltage of the first print sheet in the color printer 100 according to the first embodiment of the present invention. A flowchart showing an example of application control of a cleaning voltage and a pre-brush voltage of the first print sheet in the color printer 100 of the first embodiment. A timing chart showing on / off control of the cleaning voltage and the prebrush voltage of the first print sheet in the color printer 100 according to the second embodiment of the present invention. A flowchart showing an example of application control of the cleaning voltage and the prebrush voltage of the first print sheet in the color printer 100 of the second embodiment. Side sectional view showing the configuration around the intermediate transfer unit 30 mounted on the intermediate transfer type monochrome printer.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention, and here shows a tandem color printer. In the main body of the color printer 100, four image forming portions Pa, Pb, Pc and Pd are arranged in order from the upstream side in the transport direction (left side in FIG. 1). These image forming units Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and are cyan, magenta, and yellow, respectively, depending on each step of charging, exposure, development, and transfer. And black images are formed in sequence.

Photoreceptor drums 1a, 1b, 1c and 1d carrying visible images (toner images) of each color are disposed on these image forming portions Pa to Pd, respectively, and further, in the counterclockwise direction in FIG. A rotating intermediate transfer belt 8 is provided adjacent to each image forming portion Pa to Pd.

When image data is input from a host device such as a personal computer, first, the surfaces of the photoconductor drums 1a to 1d are uniformly charged by the charging devices 2a to 2d. Next, the exposure apparatus 5 irradiates light according to the image data to form an electrostatic latent image corresponding to the image data on the photoconductor drums 1a to 1d. The developing devices 3a to 3d are filled with a predetermined amount of a two-component developer (hereinafter, also simply referred to as a developing agent) containing toners of each color of cyan, magenta, yellow and black by the toner containers 4a to 4d. The toner in the developer is supplied onto the photoconductor drums 1a to 1d by 3a to 3d and adheres electrostatically. As a result, a toner image corresponding to the electrostatic latent image formed by the exposure from the exposure apparatus 5 is formed.

Then, an electric field is applied between the primary transfer rollers 6a to 6d and the photoconductor drums 1a to 1d by the primary transfer rollers 6a to 6d at a predetermined transfer voltage, and cyan, magenta, yellow, and cyan, magenta, yellow, and cyan, magenta, yellow, and cyanide, magenta, and yellow on the photoconductor drums 1a to 1d are applied. The black toner image is primarily transferred onto the intermediate transfer belt 8. Toner and the like remaining on the surfaces of the photoconductor drums 1a to 1d after the primary transfer are removed by the cleaning devices 7a to 7d.

The transfer paper P on which the toner image is transferred is housed in the paper cassette 16a arranged at the lower part of the color printer 100, or is placed on the bypass tray 16b arranged on the side surface of the color printer 100. .. The transfer paper P in the paper cassette 16a or on the bypass tray 16b is provided adjacent to the intermediate transfer belt 8 in the paper transport path 17 at a predetermined timing via the paper feed roller 12a and the resist roller pair 12b. The paper is conveyed to the nip portion of the transfer roller 9 and the intermediate transfer belt 8 (secondary transfer nip portion N, see FIG. 2). The transfer paper P on which the toner image is secondarily transferred is conveyed to the fixing portion 13. Toner and the like remaining on the surface of the intermediate transfer belt 8 are removed by the belt cleaning unit 19.

The transfer paper P conveyed to the fixing portion 13 is heated and pressurized by the fixing roller pair 13a to fix the toner image on the surface of the transfer paper P, and a predetermined full-color image is formed. The transfer paper P on which the full-color image is formed is directly (or after being distributed to the reversing transport path 18 by the branch portion 14 and the images are formed on both sides) from the paper transport path 17 via the discharge roller pair 15 and the discharge tray 20. Is discharged to.

FIG. 2 is a side sectional view showing the configuration around the intermediate transfer unit 30 mounted on the color printer 100 of the present embodiment. As shown in FIG. 2, the intermediate transfer unit 30 includes the intermediate transfer belt 8 spanned by the tension roller 10 on the upstream side and the drive roller 11 on the downstream side, and the photoconductor drums 1a to the intermediate transfer belt 8 via the intermediate transfer belt 8. It has primary transfer rollers 6a to 6d that come into contact with 1d, backup rollers 21a and 21b, a belt cleaning unit 19, a pre-brush 31 and a roller attachment / detachment mechanism 32. A belt drive motor 40 is connected to the drive roller 11 via a gear train (not shown).

The belt cleaning unit 19 includes a fur brush 23, a recovery roller 25, a scraper 27, and a transport spiral 29 in a housing. The fur brush 23 is arranged to face the tension roller 10 via the intermediate transfer belt 8. The fur brush 23 rotates in the counter direction (counterclockwise direction in FIG. 2) with respect to the moving direction of the intermediate transfer belt 8, so that foreign matter such as toner and paper dust remaining on the intermediate transfer belt 8 (hereinafter, toner). Etc.) are scraped off. The brush portion of the fur brush 23 in contact with the recovery roller 25 is made of conductive fibers having an electric resistance value of about 1 to 900 MΩ.

The recovery roller 25 collects toner and the like adhering to the fur brush 23 by rotating in the direction opposite to the fur brush 23 (clockwise in FIG. 2) while contacting the surface of the fur brush 23. A cleaning voltage power supply 55 is connected to the recovery roller 25, and a cleaning voltage having a polarity opposite to that of the toner (here, negative electrode property) is applied when cleaning the intermediate transfer belt 8. Further, the tension roller 10 is grounded to the ground. As a result, the toner or the like scraped from the intermediate transfer belt 8 is electrically and mechanically recovered by the brush portion of the fur brush 23, and further electrically transferred to the recovery roller 25. The transport spiral 29 transports the toner or the like scraped off from the recovery roller 25 by the scraper 27 to a waste toner recovery container (not shown) outside the housing.

The pre-brush 31 is arranged on the upstream side of the belt cleaning unit 19 with respect to the moving direction of the intermediate transfer belt 8. A pre-brush voltage power supply 56 is connected to the pre-brush 31, and by applying a pre-brush voltage having the same polarity as the toner (here, positive electrode property) to the pre-brush 31, the charge amount of the residual toner on the intermediate transfer belt 8 is made uniform. .. As a result, the residual toner on the intermediate transfer belt 8 can be easily removed by the fur brush 23.

The roller contact / disengagement mechanism 32 has a color mode in which the four primary transfer rollers 6a to 6d are pressed against the photoconductor drums 1a to 1d via the intermediate transfer belt 8, and the intermediate transfer belt 8 is used only for the primary transfer roller 6d. It is possible to switch between a monochrome mode in which the photoconductor drum 1d is pressed against the photoconductor drum 1d and a primary transfer separation state in which all four primary transfer rollers 6a to 6d are separated from the intermediate transfer belt 8.

FIG. 3 is a block diagram showing an example of a control path used in the color printer 100. Since various controls are performed on each part of the device when the color printer 100 is used, the control path of the entire color printer 100 becomes complicated. Therefore, here, the part of the control path required for carrying out the present invention will be mainly described.

The control unit 90 includes a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only storage unit, a RAM (Random Access Memory) 93 as a read / write storage unit, and a temporary storage unit. A plurality of (here, two) control signals are transmitted to each device in the temporary storage unit 94, the counter 95, and the color printer 100 for storing image data and the like, and input signals from the operation unit 60 are received. It has at least an I / F (interface) 96. Further, the control unit 90 can be arranged at any place inside the main body of the apparatus.

The ROM 92 contains data such as a control program for the color printer 100 and numerical values required for control that are not changed during use of the color printer 100. The RAM 93 stores necessary data generated during the control of the color printer 100, data temporarily required for the control of the color printer 100, and the like. For example, as will be described later, when image formation (primary transfer) is performed at a position where the fur brush 23 and the pre-brush 31 of the intermediate transfer belt 8 are in contact with each other at the start of image formation, a voltage is applied to the recovery roller 25 and the pre-brush 31. The timing etc. are stored. The counter 95 integrates and counts the number of printed sheets.

Further, the control unit 90 transmits a control signal from the CPU 91 to each part and the device of the color printer 100 through the I / F 96. Further, a signal indicating the state and an input signal from each part and the device are transmitted to the CPU 91 through the I / F 96. Examples of the parts and devices controlled by the control unit 90 include image forming units Pa to Pd, exposure devices 5, primary transfer rollers 6a to 6d, secondary transfer rollers 9, voltage control circuit 51, operation unit 70, and the like. Be done.

The voltage control circuit 51 is connected to a charging voltage power supply 52, a developing voltage power supply 53, a transfer voltage power supply 54, a belt cleaning voltage power supply 55, and a pre-brush voltage power supply 56, and operates each of these power supplies by an output signal from the control unit 90. In each of these power supplies, the charging voltage power supply 52 is made to the charging roller in the charging devices 2a to 2d, and the developing voltage power supply 53 is magnetic in the developing devices 3a to 3d by the control signal from the voltage control circuit 51. For rollers and developing rollers, the transfer voltage power supply 54 is for the primary transfer rollers 6a to 6d and the secondary transfer roller 9, the belt cleaning voltage power supply 55 is for the recovery roller 25 of the belt cleaning unit 19, and the prebrush voltage power supply 56 is for the prebrush 31. A predetermined voltage is applied to each.

The operation unit 70 is provided with a liquid crystal display unit 71 and LEDs 72 indicating various states. The user operates the stop / clear button of the operation unit 70 to stop image formation, and operates the reset button to color. Set various settings of the printer 100 to the default state. The liquid crystal display unit 61 is designed to indicate the state of the color printer 100, the image formation status, and the number of printed copies. Various settings of the color printer 100 are performed from the printer driver of the personal computer.

As described above, when a cleaning voltage having a polarity opposite to that of the toner is applied to the recovery roller 25 at the start of image formation, the back-charged toner accumulated in the fur brush 23 moves onto the intermediate transfer belt 8. Further, when a voltage having the same polarity as the toner is applied to the prebrush 31, the positively charged toner accumulated in the prebrush 31 moves onto the intermediate transfer belt 8. When the toner is transferred to the region (image transfer region) where the first image printed on the intermediate transfer belt 8 is first transferred, a problem occurs in which a horizontal band-shaped image stain appears.

Therefore, the color printer 100 according to the first embodiment of the present invention is characterized in that the toner accumulated in the fur brush 23 and the pre-brush 31 is transferred to a position that does not overlap with the first image area on the intermediate transfer belt 8. There is. Specifically, a voltage is applied to the recovery roller 25 and the prebrush 31 at the timing when the first image transfer region on the intermediate transfer belt 8 passes through the fur brush 23 and the prebrush 31.

FIG. 4 is a timing chart showing on / off control of the cleaning voltage and the pre-brush voltage of the first printing sheet of the color printer 100 of the first embodiment, and FIG. 5 is the printing 1 of the color printer 100 of the first embodiment. It is a flowchart which shows the application control example of the cleaning voltage and the prebrush voltage of the 1st sheet. The procedure for applying the cleaning voltage and the pre-brush voltage will be described along the steps of FIG. 5 with reference to FIGS. 1 to 4 as necessary.

When printing is started by receiving a printing command from a higher-level device such as a personal computer (step S1), a control signal is transmitted from the CPU 91 to the belt drive motor 40, and is intermediate at a predetermined timing (time T1 in FIG. 4). The drive of the transfer belt 8 is started (step S2). On the other hand, the control unit 90 determines whether or not the image transfer region of the first print sheet on the intermediate transfer belt 8 has passed through the fur brush 23 (step S3).

Then, at the timing when the image transfer region of the first print sheet passes through the fur brush 23 (time T2 in FIG. 4), a control signal is transmitted from the CPU 91 to the voltage control circuit 51, and the cleaning voltage power supply 55 of the belt cleaning unit 19 A cleaning voltage is applied to the recovery roller 25 (step S4). Further, a pre-brush voltage is applied from the pre-brush voltage power supply 56 to the pre-brush 31 (step S5). The cleaning voltage power supply 55 is controlled by a constant current, and a voltage is applied here so that the current value becomes −11 μA. Further, the pre-brush voltage power supply 56 is controlled by a constant voltage, and + 350V is applied here.

Specifically, the circumference of the intermediate transfer belt 8 from the fur brush 23 to the photoconductor drum 1a located on the most upstream side in the moving direction of the intermediate transfer belt 8 is L1, the rotation speed of the intermediate transfer belt 8 is V, and the intermediate is intermediate. When t is the time from the start of driving the transfer belt 8 to the end of the primary transfer of the toner image on the photoconductor drum 1a, the cleaning voltage and the prebrush voltage are set at the time T2 that satisfies T2> t−L1 / V. Apply.

After that, image formation is performed in the image forming units Pa to Pd (see FIG. 1), and the toner images formed on the photoconductor drums 1a to 1d are sequentially primarily transferred onto the intermediate transfer belt 8 (step S6). Further, the transfer paper P is conveyed from the paper cassette 16a or the manual feed tray 16b to the secondary transfer roller 9 via the paper feed roller 12a and the resist roller pair 12b, and the toner image on the intermediate transfer belt 8 is secondary to the transfer paper P. It is transferred (step S7).

Then, the post-transfer region of the first image on the intermediate transfer belt 8 reaches the pre-brush 31 (step S8), and the charge amount of the residual toner on the intermediate transfer belt 8 is made uniform. The residual toner having a uniform charge amount is cleaned by the fur brush 23 (step S9).

According to the control of FIG. 5, the toner accumulated in the fur brush 23 and the pre-brush 31 is adjusted by adjusting the timing of applying the cleaning voltage to the fur brush 23 (recovery roller 25) and the timing of applying the pre-brush voltage to the pre-brush 31. Is moved to a position on the intermediate transfer belt 8 that does not overlap with the image transfer area of the first sheet, so that image stains on the first image of the printed sheet can be effectively prevented.

By the way, even when the pre-brush voltage is not applied to the pre-brush 31, toner transfer from the pre-brush 31 to the intermediate transfer belt 8 may occur depending on the amount of toner accumulated in the pre-brush 31 and the distribution of the amount of charge. In the control of the first embodiment described above, since the cleaning voltage is not applied to the fur brush 23 (recovery roller 25) at the start of driving the intermediate transfer belt 8, the toner transferred from the pre-brush 31 to the intermediate transfer belt 8 is fur. In some cases, it could not be recovered by the brush 23, and the image stain could not be completely removed.

FIG. 6 is a timing chart showing on / off control of the cleaning voltage and the pre-brush voltage of the first print sheet in the color printer 100 according to the second embodiment of the present invention, and FIG. 7 is the color printer of the second embodiment. It is a flowchart which shows the application control example of the cleaning voltage and the pre-brush voltage of the first printing sheet in 100. The procedure for applying the cleaning voltage and the pre-brush voltage will be described along the steps of FIG. 7 with reference to FIGS. 1 to 3 and 6 as necessary.

When printing is started by receiving a printing command from a higher-level device such as a personal computer (step S1), a control signal is transmitted from the CPU 91 to the belt drive motor 40, and is intermediate at a predetermined timing (time T1 in FIG. 6). The drive of the transfer belt 8 is started (step S2). Cleaning voltage A cleaning voltage is applied from the power supply 55 to the recovery roller 25 of the belt cleaning unit 19 in accordance with the drive start timing of the intermediate transfer belt 8 (step S3). The cleaning voltage applied in step S4 is a voltage V1 (first voltage) lower than the normal cleaning voltage V2 (second voltage), and here, a voltage such that the current value is −5 μA is applied. To.

Next, the control unit 90 determines whether or not the region (image transfer region) on which the first image to be printed on the intermediate transfer belt 8 is primarily transferred has passed through the fur brush 23 (step S4). Then, at the timing when the image transfer region of the first print sheet passes through the fur brush 23 (time T2 in FIG. 6), a control signal is transmitted from the CPU 91 to the voltage control circuit 51, and the cleaning voltage is set to a voltage V1 (time T2 lower than usual). The voltage is increased from −5 μA) to the normal cleaning voltage V2 (-11 μA) (step S5). Further, a pre-brush voltage (here, +350 V) is applied from the pre-brush voltage power supply 56 to the pre-brush 31 (step S6). The timing at which the image transfer region of the first print sheet passes through the fur brush 23 is determined in the same manner as in the first embodiment.

After that, image formation is performed in the image forming units Pa to Pd (see FIG. 1), and the toner images formed on the photoconductor drums 1a to 1d are sequentially primaryly transferred onto the intermediate transfer belt 8 (step S7). Further, the transfer paper P is conveyed from the paper cassette 16a or the manual feed tray 16b to the secondary transfer roller 9 via the paper feed roller 12a and the resist roller pair 12b, and the toner image on the intermediate transfer belt 8 is secondary to the transfer paper P. It is transferred (step S8).

Then, the first post-transfer region on the intermediate transfer belt 8 reaches the pre-brush 31 (step S9), and the charge amount of the residual toner on the intermediate transfer belt 8 is made uniform. The residual toner having a uniform charge amount is cleaned by the fur brush 23 (step S10).

According to the control of FIG. 7, the fur brush 23 is adjusted by adjusting the timing of applying the cleaning voltage to the fur brush 23 (recovery roller 25) and the timing of applying the pre-brush voltage to the pre-brush 31 as in the first embodiment. Since the toner accumulated in the pre-brush 31 is transferred to a position on the intermediate transfer belt 8 that does not overlap with the image transfer area of the first image, it is possible to effectively prevent image stains on the first image of printing.

Further, by applying a cleaning voltage lower than the normal cleaning voltage to the fur brush 23 (recovery roller 25) at the same time as the operation of the intermediate transfer belt 8 is started, the discharge of the back-charged toner from the fur brush 23 is suppressed while suppressing the discharge of the back-charged toner. A small amount of positively charged toner transferred from the pre-brush 31 onto the intermediate transfer belt 8 can be recovered by the fur brush 23. Therefore, it is possible to more effectively suppress image stains on the first printed sheet as compared with the first embodiment.

Others The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the above embodiments, the fur brush 23 for collecting the residual toner on the intermediate transfer belt 8 and the pre-brush 31 for equalizing the charge amount of the residual toner on the intermediate transfer belt 8 are provided. It is also possible to apply the present invention to a configuration that does not use. Even in this case, the cleaning voltage applied to the fur brush 23 (recovery roller 25) is set to 0 or a voltage lower than usual until the first image transfer region on the intermediate transfer belt 8 passes through the fur brush 23. By raising the image transfer area to a normal cleaning voltage after passing through the fur brush 23, it is possible to suppress image stains on the first print sheet due to the back-charged toner adhering to the fur brush 23 moving to the image transfer area.

Further, in each of the above embodiments, the cleaning voltage is applied (or increased) and the pre-brush voltage is applied at the same time after the first image transfer region on the intermediate transfer belt 8 has passed through the fur brush 23. However, the timing of applying the pre-brush voltage may be after the first image transfer region on the intermediate transfer belt 8 has passed through the pre-brush 31. Therefore, the pre-brush voltage can be applied after the image transfer region has passed through the pre-brush 31, and the cleaning voltage can be applied (or increased) after the image transfer region has passed through the fur brush 23.

Since the pre-brush 31 is usually arranged close to the upstream side of the fur brush 23, the cleaning voltage is applied (or increased) and the pre-brush voltage is applied at the same time after the image transfer region passes through the fur brush 23. Therefore, the control can be simplified.

Further, in each of the above embodiments, the fur brush 23 is used as a cleaning member for collecting the residual toner on the intermediate transfer belt 8, but a cleaning roller can be used instead of the fur brush 23.

Further, the present invention is not limited to the color printer 100 as shown in FIG. 1, and of course, the present invention can be applied to various intermediate transfer type image forming devices such as color copiers, digital multifunction devices, and facsimiles. Is.

Further, as shown in FIG. 8, one photoconductor drum 1d on which a black image is formed and one primary transfer roller 6d facing the photoconductor drum 1d are arranged with the intermediate transfer belt 8 interposed therebetween. It is also applicable to an intermediate transfer type monochrome printer provided with the unit 30.

The present invention can be used in an intermediate transfer type image forming apparatus provided with a cleaning member for removing residual toner on the surface of the intermediate transfer belt. By utilizing the present invention, it is possible to provide an image forming apparatus capable of suppressing the occurrence of image stains due to the toner adhering to the cleaning member being retransferred to the image transfer region on the intermediate transfer belt.

1a-1d Photoreceptor drum (image carrier)
6a-6d Primary transfer roller (primary transfer member)
8 Intermediate transfer belt 9 Secondary transfer roller (secondary transfer member)
23 Fur brush (cleaning member)
31 Pre-brush (pre-cleaning member)
40 Belt drive motor (drive device)
51 Voltage control circuit (power supply)
55 Cleaning voltage power supply (power supply device)
56 Pre-brush voltage power supply (power supply device)
90 Control unit 100 Color printer (image forming device)

Claims (5)

An image carrier on which a toner image is formed and
An endless intermediate transfer belt placed adjacent to the image carrier,
A primary transfer member which is arranged so as to face the image carrier with the intermediate transfer belt interposed therebetween and primary transfers a toner image formed on the image carrier onto the intermediate transfer belt.
A secondary transfer member that contacts the intermediate transfer belt to form a secondary transfer nip portion and secondarily transfers the toner image primaryly transferred onto the intermediate transfer belt to a recording medium that passes through the secondary transfer nip portion. When,
A cleaning member that cleans the residual toner on the intermediate transfer belt, and
A power supply device that applies a cleaning voltage of the opposite polarity to the toner to the cleaning member,
A drive device that rotationally drives the intermediate transfer belt and
A control unit that controls the drive device and the power supply device,
In an image forming apparatus equipped with
The control unit does not apply the cleaning voltage when the intermediate transfer belt is stopped, drives the intermediate transfer belt to rotate at the start of image formation , and first transfers the first image on the intermediate transfer belt. image transfer region, said a 0 or a 1 voltage the cleaning voltage to pass through the cleaning member before the primary transfer, the cleaning voltage after the image transfer region before the primary transfer has passed through the cleaning member An image forming apparatus, characterized in that the voltage is raised to a second voltage higher than the first voltage. A pre-cleaning member arranged on the upstream side of the cleaning member with respect to the moving direction of the intermediate transfer belt and controlling the amount of charge of toner on the intermediate transfer belt is provided.
The power supply device can apply a pre-cleaning voltage having the same polarity as the toner to the pre-cleaning member.
The control unit sets the pre-cleaning voltage to 0 until the first image transfer region on the intermediate transfer belt passes through the pre-cleaning member, and after the image transfer region passes through the pre-cleaning member, the pre-cleaning voltage is set to 0. The image forming apparatus according to claim 1, wherein a cleaning voltage is applied. The second aspect of claim 2, wherein the control unit simultaneously raises the cleaning voltage to the second voltage and applies the pre-cleaning voltage after the image transfer region has passed through the cleaning member. Image forming device. Claim 2 or claim 3 is characterized in that the control unit applies the pre-cleaning voltage before the timing when the post-transfer region of the first image on the intermediate transfer belt reaches the pre-cleaning member. The image forming apparatus according to. Claim 1 is characterized in that the control unit raises the cleaning voltage to the second voltage before the timing when the post-transfer region of the first image on the intermediate transfer belt reaches the cleaning member. The image forming apparatus according to any one of claims 4.

Images