JP2003114561A - Image forming device - Google Patents

Abstract

(57) [Problem] To improve the productivity and extend the life of replacement of a photosensitive member by shortening a rotation step time after a cleaning step of an intermediate transfer member is performed. When a surface of an intermediate transfer member is cleaned during non-image formation after mono-color image formation, a bias is applied from a cleaning bias power supply to an AC bias and a DC bias having a polarity opposite to a normal charge polarity of toner of a toner image. The secondary transfer residual toner remaining on the rotating intermediate transfer body 6 is charged to a polarity opposite to the normal charging polarity by only applying the voltage to the roller 10 to electrostatically charge the primary transfer portion N. The transfer time can be shortened after cleaning the intermediate transfer member 6 when forming a monocolor image with a small amount of secondary transfer residual toner by transferring substantially all to the rotating photoreceptor 1 side. Therefore, the productivity can be improved and the exchange life of the photoconductor 1 can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which forms an image by utilizing an electrophotographic system or an electrostatic recording system, and more specifically, a toner image formed on an image carrier is once formed on an intermediate transfer body. Image forming apparatus, such as a copying machine, a printer, or a facsimile, which first-transfers the toner image onto the transfer medium, and secondarily transfers the toner image transferred onto the intermediate transfer member onto a transfer material by a secondary transfer member to form a full-color or mono-color image. Regarding

[0002]

2. Description of the Related Art A full-color image forming apparatus using an intermediate transfer member is, for example, as shown in FIG. 13, yellow, magenta, and cyan formed on a drum type electrophotographic photosensitive member (hereinafter referred to as photosensitive member) 100. , Black toner images are sequentially superposed on the drum-shaped intermediate transfer member 101 at the primary transfer nip portion N, and then the secondary transfer nip portion M is formed.
A secondary transfer belt 102 as a secondary transfer member that comes into contact with the intermediate transfer member 101 collectively transfers a full-color image onto a transfer material (not shown) such as a sheet conveyed to the secondary transfer nip M. Is formed.

In the mono-color mode, a toner image of only a single black color is formed on the photoconductor 100, transferred to the intermediate transfer member 101, transferred from the intermediate transfer member 101 to a transfer material, and fixed to a mono-color image. (Black monochrome image)
Can be obtained.

Further, after the above-mentioned image formation, the primary transfer residual toner remaining on the photosensitive member 100 is removed by the cleaning blade 104, and the intermediate transfer member 10 is removed.
The secondary transfer residual toner remaining at 1 is charged to the opposite polarity to the regular charging polarity by the bias applying roller 103 to which a bias is applied, and is electrostatically attached to the photoconductor 100 at the primary transfer nip portion N. Attached to the intermediate transfer member 101
Surface is cleaned. The secondary transfer residual toner attached to the photoconductor 100 is removed by the cleaning blade 104.

Next, the cleaning of the intermediate transfer member 101 in the above image forming apparatus will be described in detail.

The cleaning of the intermediate transfer member 101 is a step of removing the secondary transfer residual toner remaining on the surface of the intermediate transfer member 101. Intermediate transfer member 101 after passing through the secondary transfer process
On the surface, a few percent of the toner (secondary transfer residual toner) that could not be completely transferred to the transfer material adheres. If this secondary transfer residual toner is left as it is, it is secondarily transferred to a transfer material at the time of the next image formation, causing an image defect,
The transfer material may be scattered inside the device and stain the transfer material.

Therefore, in an image forming apparatus using an intermediate transfer body, it is important how to remove the secondary transfer residual toner remaining on the intermediate transfer body.

Therefore, conventionally, as described above, the bias applying roller 103 is arranged so as to be in contact with the surface of the intermediate transfer member 101, and the bias applying roller 103 has a bias having a polarity opposite to the charging polarity of the toner during image formation. Is applied to charge the secondary transfer residual toner remaining on the intermediate transfer member 101 to a polarity opposite to that at the time of image formation, and the potential difference between the surface potential of the photoconductor 100 and the surface potential of the intermediate transfer member 101 is caused. A method has been proposed in which the photoconductor 100 is adsorbed and collected.

Specifically, the bias applying roller 103 as a roller-shaped charging member made of general rubber or the like.
To use. When using negative toner with negative charge,
The secondary transfer residual toner remaining on the intermediate transfer member 101 after the secondary transfer is toner that is weakly plus or weakly less likely to be secondary-transferred.

Then, the bias applying roller 103 is brought into contact with the intermediate transfer member 101, and AC bias and positive DC are applied.
Bias applying roller 1 by applying a bias
The secondary transfer residual toner passing through 03 is charged to a positive polarity. The positively charged secondary transfer residual toner passes through the primary transfer nip portion N again while adhering to the surface of the intermediate transfer member 101.

At this time, when passing through the primary transfer nip portion N between the negatively charged photosensitive drum 100 and the positively charged intermediate transfer drum 101, the secondary transfer positively charged due to the potential difference between them. By transferring the residual toner to the photosensitive drum 100, the residual toner on the intermediate transfer member 101 is removed. The secondary transfer residual toner transferred to and collected on the photosensitive drum 100 is transferred to the photosensitive drum 10.
Cleaning blade 1 as 0 cleaning means
It is removed and collected by 04.

As described above, in the above-described method for cleaning the intermediate transfer member 101, since the cleaning blade for mechanically scraping the intermediate transfer member 101 is not used, the cleaning blade comes into contact with the intermediate transfer member 101. It has an advantage that it is released from the shock of separation, the abrasion of the intermediate transfer member 101, and the problem of processing the collected waste toner.

When a full-color image is formed by using toners of a plurality of colors (yellow, magenta, cyan, black) as described above, the amount of secondary transfer residual toner is large, which is 1 A single cleaning step may not be enough.

That is, in the cleaning process of the intermediate transfer member 101, the intermediate transfer member cleaning roller 1 is used.
If the amount of secondary transfer residual toner passing through 03 is large,
The secondary transfer residual toner that has passed through the bias applying roller 103 may be in a state in which positively charged toner and toner that is not sufficiently charged and remains weak positive or weak negative are mixed.

At this time, in the primary transfer nip portion N, only the positively charged toner is transferred to the photosensitive member 100, so that the other toner remains on the intermediate transfer member 101. In this case, the residual toner can be removed by passing the intermediate transfer member 101 through the bias applying roller 103 a plurality of times.

Further, in the cleaning process of the intermediate transfer member 101, the secondary transfer residual toner may adhere to and remain on the bias applying roller 103. For example, when the amount of secondary transfer residual toner passing through the bias applying roller 103 is large, or when the charge state of the secondary transfer residual toner is strong in the negative side, the positive DC bias applied to the bias applying roller 103 causes Toner does not pass through the bias applying roller 103 and the bias applying roller 1
03 may be attached.

Further, the secondary transfer residual toner may be fixed to the bias applying roller 103 and the charging performance of the toner may be deteriorated due to temperature rise in the image forming apparatus or long-term storage. Therefore, a so-called "discharging step" as described below, in which the secondary transfer residual toner attached to the bias applying roller 103 is transferred to the intermediate transfer body 101, is required.

Since many secondary transfer residual toners attached to the bias applying roller 103 are not positively charged and have a negative polarity, the intermediate transfer member 10 positively charged.
For example, the bias applied to the bias applying roller 103 is turned off, or the bias having the same polarity (minus) as that of the secondary transfer residual toner attached is applied to the secondary applying roller 103. The bias application roller 103 can be cleaned by setting the potential state in the direction in which the transfer residual toner is transferred to the intermediate transfer member 101.

The negative toner transferred to the intermediate transfer member 101 remains on the intermediate transfer member 101 without being collected by the photosensitive member 100 at the primary transfer nip portion N, and therefore, when passing through the bias applying roller 103 again, AC is applied. By applying a bias and a positive DC bias, it is positively recharged and is collected by the photoconductor 100 at the primary transfer nip portion N.

The cleaning process of the intermediate transfer member 101 by the bias applying roller 103 is performed in a so-called post-rotation process for preparing for the next image forming operation after the image forming operation is completed. In the post-rotation step, cleaning of the photoconductor 101 and the intermediate transfer member 101 described above, removal of residual charges on the photoconductor 101, discharge of the transfer material having the toner image transferred / fixed to the outside, and the like are performed.

[0021]

However, the above-described conventional method for cleaning the intermediate transfer member 101 has the following problems.

As described above, when the secondary transfer residual toner amount is large, the charging by the bias applying roller 103 is repeated, or when the secondary transfer residual toner adheres to the bias applying roller 103, the charging and discharging are performed. , And recharging had to be repeated.

Therefore, the post-rotation step time is lengthened by the cleaning step of the intermediate transfer member 101 by the bias applying roller 103 after the image forming operation is completed, and the next image forming operation can be started immediately after the image forming operation is completed. There is a problem that productivity is reduced because it cannot be done.

When the post-rotation process time is lengthened by the intermediate transfer member cleaning process, the total number of rotations of the photosensitive member 100 and the intermediate transfer member 101 is increased, so that the photosensitive member 100 is increased.
There is a problem in that abrasion and scratches of the intermediate transfer member 101 and the like are increased, the replacement life of these members is shortened, and the running cost is increased.

Therefore, according to the present invention, it is possible to improve the productivity and prolong the replacement life of the members such as the photoconductor and the intermediate transfer member by shortening the time of the rotation process after the intermediate transfer member cleaning process is performed. An object is to provide an image forming apparatus.

[0026]

In order to achieve the above object, the present invention provides at least one rotatable image carrier on which an electrostatic latent image is formed, and an electrostatic image formed on the image carrier. A plurality of developing devices that develop a latent image to form a toner image of a single color or a plurality of different colors are brought into contact with the image carrier at the primary transfer portion, and the toner image formed on the image carrier is A toner image transferred onto the intermediate transfer body, which is brought into contact with the rotatable intermediate transfer body which is primarily transferred at the primary transfer section by the application of the next transfer bias, and the intermediate transfer body at the secondary transfer section. A secondary transfer member that secondary-transfers at a secondary transfer portion to a transfer material that is conveyed to the secondary transfer portion by applying a secondary transfer bias, and the second transfer member along the rotation direction of the intermediate transfer body.
A bias applying member disposed on the intermediate transfer member on the downstream side of the next transfer unit and on the upstream side of the primary transfer unit so as to be freely contactable and separable, and bias applying means for applying a bias to the bias applying member. When a color image is formed, the toner images of different colors formed on the image carrier by the plurality of developing devices are superimposed and transferred onto the intermediate transfer member, and then transferred onto the transfer material by the secondary transfer member. At the time of batch transfer and formation of a single color image, the single color toner image formed on the image carrier by any one of the plurality of developing devices is transferred onto the intermediate transfer member and then the secondary transfer member. At the time of non-image formation after the toner image on the intermediate transfer body is secondarily transferred to the transfer material, the bias applying member is brought into contact with the intermediate transfer body to apply the bias. Bias sign from means The surface of the intermediate transfer body is controlled by electrostatically transferring the transfer residual toner remaining on the intermediate transfer body after the secondary transfer to the image carrier side at the primary transfer portion by controlling the charge polarity. In the image forming apparatus for cleaning the surface of the intermediate transfer member during the non-image formation after the monochromatic image formation, at least the DC bias of the polarity opposite to the normal charging polarity of the toner of the toner image is applied from the bias applying unit. Is applied to the bias applying member only, the transfer residual toner remaining on the rotating intermediate transfer member is charged to a polarity opposite to the regular charging polarity and electrostatically When the surface of the intermediate transfer body is cleaned during the non-image formation after the color image formation, the toner is transferred to the side of the image carrier rotating in the next transfer section. A DC bias of at least the opposite polarity to the regular charging polarity is applied to the bias applying member from the ass applying unit to charge the transfer residual toner remaining on the rotating intermediate transfer member to the regular charging. After being charged to a polarity opposite to the polarity and electrostatically transferred to the side of the image carrier rotating in the primary transfer portion, the bias applying means further applies a DC bias having the same polarity as the regular charging polarity. Is applied to the bias applying member to electrostatically eject a part of the transfer residual toner adhering to the bias applying member side from the intermediate transfer member to the intermediate transfer member side, and at least from the bias applying unit. A DC bias having a polarity opposite to the regular charging polarity is applied to the bias applying member to recharge the ejected toner to a polarity opposite to the regular charging polarity and electrostatically front the toner. It is characterized in that the image is transferred to the rotating image carrier side at the primary transfer portion.

In addition, the cumulative number of rotations of the image carrier during the cleaning of the surface of the intermediate transfer body during the non-image formation after the monochromatic image formation is the intermediate transfer body during the non-image formation after the color image formation. With respect to the cumulative number of rotations of the image carrier during surface cleaning, the transfer residual toner adhering to the bias applying member during cleaning of the surface of the intermediate transfer member during non-image formation after the color image formation It is characterized in that it is smaller by the amount corresponding to the cumulative number of rotations of the image carrier when the part is discharged to the side of the intermediate transfer member and when the discharged toner is recharged and transferred to the side of the image carrier. There is.

Further, the cumulative rotation time of the image carrier during the cleaning of the surface of the intermediate transfer body during the non-image formation after the formation of the monochromatic image is determined by the intermediate transfer body during the non-image formation after the color image formation. With respect to the cumulative rotation time of the image carrier during surface cleaning, the transfer residual toner adhering to the bias applying member during cleaning of the surface of the intermediate transfer member during non-image formation after the color image formation It is characterized in that it is short by an amount corresponding to an integrated rotation time of the image carrier when the part is discharged to the intermediate transfer body side and when the discharged toner is recharged and transferred to the image carrier side. There is.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows an image forming apparatus according to the first embodiment of the present invention (in the present embodiment, electrophotographic intermediate transfer full-color image formation and mono-color (black single color)). FIG. 1 is a schematic configuration diagram showing an image forming apparatus such as a laser printer capable of forming an image.

The image forming apparatus includes a photoconductor 1 as an image carrier. Around the photoconductor 1, a charging roller 2 that uniformly charges the surface of the photoconductor 1 in a negative polarity along the rotation direction of the photoconductor 1, and the photoconductor 1 is exposed L based on an input image signal. Exposure device (laser scanning unit) 3 for forming an electrostatic latent image on the photoconductor 1, developing devices 4 and 5 for developing toner by attaching toner to the electrostatic latent image on the photoconductor 1, a toner image formed on the photoconductor 1 A drum-shaped intermediate transfer member 6 for primary transfer of the toner and a cleaning device 9 for removing / collecting the residual toner remaining on the photosensitive member 1 are arranged.

The developing device 4 is a fixed developing device having black toner, and the developing device 5 is a rotary developing device having yellow, cyan, and magenta toners.

The intermediate transfer member 6 is in contact with the photosensitive member 1 at the primary transfer nip portion N, and is in contact with the secondary transfer belt 7 as a secondary transfer member at the secondary transfer nip portion M, and the upper surface of the belt. Moves (rotates) in the direction of the arrow. The intermediate transfer member 6 is cylindrical and has a roller shape having a metal cored bar as a conductive support and an elastic layer made of at least rubber, elastomer, and resin, and further has one or more coating layers on the elastic layer. It has a drum shape and is rotated at substantially the same speed as the photoconductor 1.

The intermediate transfer member 6 has a primary transfer bias power source 1
1 is connected, and a predetermined primary transfer bias is applied from the primary transfer bias power source 11 to the intermediate transfer member 6. Further, the bias applying roller 1 is provided on the outer peripheral surface of the intermediate transfer member 6.
0 is arranged so that it can be brought into contact with or separated from it, and a cleaning bias power source 12 is connected to the bias applying roller 10.

The secondary transfer belt 7 is a secondary transfer roller 7a.
The endless resin belt is stretched between the drive roller 7b and the drive roller 7b, and the upper surface of the belt is moved (rotated) in the arrow direction by the rotational drive of the drive roller 7b. A secondary transfer bias power source 13 is connected to the secondary transfer roller 7a. Also, 2
The secondary transfer belt 7 can be brought into contact with and separated from the intermediate transfer body 6 at a predetermined timing, and is transferred to the intermediate transfer body 6 via the secondary transfer belt 7 at the secondary transfer nip portion M during secondary transfer. Abut.

A fixing device 8 having a fixing roller 8a and a pressure roller 8b is arranged downstream of the secondary transfer belt 7 in the transfer material conveying direction. A heater 8c is built in the fixing roller 8a.

Next, the full-color image forming operation of the above-mentioned image forming apparatus will be described.

During image formation, the photosensitive member 1 is rotationally driven at a predetermined process speed by driving means (not shown),
The charging roller 2 to which a predetermined charging bias is applied from a charging bias power source (not shown) is uniformly charged to −550V.

Then, the exposure unit 3 gives an exposure L by a laser beam on the charged photosensitive member 1 to generate an electrostatic latent image corresponding to a first color component image (for example, a yellow component image) of a target color image. An image is formed. At this time, the surface of the photoreceptor 1 after exposure has an unexposed partial potential of −550V and an exposed partial potential of −150V. Then, by a developing roller (not shown) to which a developing bias (-550V) of the developing device 5 is applied, this electrostatic latent image is developed with yellow toner which is the first color and visualized.

The first color yellow toner image formed and carried on the photoconductor 1 passes through the primary transfer nip N between the intermediate transfer member 6 and the primary transfer nip. By the pressure at N and the electric field formed by the primary transfer bias (+300 V) applied from the primary transfer bias power source 11, the primary transfer is performed on the outer peripheral surface of the intermediate transfer member 6. 1 yellow toner image on the intermediate transfer member 6.
After the secondary transfer, the primary transfer residual toner remaining on the photoconductor 1 without being primary transferred to the intermediate transfer body 6 is removed and collected by the cleaning blade 9 a of the cleaning device 9.

Thereafter, similarly, by the developing devices 4 and 5, the magenta toner image of the second color, the cyan toner image of the third color, and the black toner image of the fourth color, which are respectively formed and carried on the photoconductor 1, are sequentially formed. A full-color toner image corresponding to a target color image is formed by being superimposed and transferred onto the intermediate transfer member 6.

Then, the secondary transfer belt 7 is connected to the intermediate transfer member 6.
The secondary transfer nip portion M is formed by applying pressure to the intermediate transfer member 6
The transfer material P such as paper is conveyed to the secondary transfer nip portion M in synchronization with the leading end of the upper full-color image. At this time, a secondary transfer bias (+1.5 kV) is applied from the secondary transfer bias power source 13 to the secondary transfer roller 7a, and a full-color toner image is collectively transferred from the intermediate transfer body 6 onto the transfer material P (secondary transfer). To be done.

Then, the transfer material P on which the full-color toner image is transferred is conveyed to the fixing device 8 and is nipped and conveyed at the fixing nip portion between the fixing roller 8a and the pressure roller 8b of the fixing device 8 and the fixing roller 8a. The full-color toner image is heated and pressed in the fixing nip portion between the pressure roller 8b and the pressure roller 8b to be fixed on the transfer material P, and then discharged to the outside.

The secondary transfer residual toner remaining on the intermediate transfer member 6 without being secondary-transferred is removed from the cleaning bias power source 12 in the above-described post-rotation step during non-image formation after the image forming operation. The bias applying roller 10 to which the bias is applied is charged to a polarity (plus) opposite to the regular charging polarity, and is electrostatically adsorbed to the photoconductor 1 at the primary transfer nip portion N, so that the intermediate transfer body 6 is charged. The surface is cleaned. The secondary transfer residual toner transferred onto the photoreceptor 1 is cleaned by the cleaning blade 9 a of the cleaning device 9.
Are removed and collected (the details of the step of cleaning the intermediate transfer member 6 at the time of forming the above-mentioned full-color image and in the case of a mono-color image will be described later).

When outputting a mono-color image (black monochromatic image), the black toner image formed on the photoconductor 1 by the developing device 4 is first transferred onto the intermediate transfer member 6 and then transferred onto the transfer material P. A black monochromatic image can be obtained by secondary transfer.

Next, the intermediate transfer member 6 in the present embodiment.
The cleaning step will be described in detail.

In the above-described image forming apparatus, in the present embodiment, when the diameter of the photosensitive member 1 is 60 mm, the diameter of the intermediate transfer member 6 is 180 mm (perimeter 565 mm), and the process speed is 113 mm / sec, the intermediate transfer member 6 is It takes about 5 seconds to clean one rotation of the photosensitive drum 1, and the photosensitive member 1 rotates 3 times during this period.

First, in the case of a monocolor image forming mode for obtaining a black and white print using black toner, A
4 size paper (transfer material) in the short side direction (length 210 m
m) to form an image of characters, line patterns, solid black, and the like, on the intermediate transfer body 6 after the secondary transfer, as shown in FIG.
a remained.

Then, as shown in FIG. 3, when cleaning the intermediate transfer member 6 in the post-rotation step, the bias applying roller 10 is brought into contact with the area where the transfer residual toner (black toner Ta) is attached. When a DC bias of +20 μA was applied from the cleaning bias power supply 12 in addition to an AC bias having a peak-to-peak voltage of 4.5 kV and a frequency of 2 kHz, the transfer residual toner (black toner Ta) on the intermediate transfer member 6 was positive in the opposite polarity. The toner was charged to become the toner Tb, and most of it was electrostatically transferred to the photosensitive member 1 as the toner Tc at the primary transfer nip portion N, and the surface of the intermediate transfer member 6 could be cleaned.

At this time, almost no toner adhesion was observed on the bias applying roller 10, and the post-rotation (cleaning process) could be completed in about 5 seconds. Further, since almost no transfer residual toner adheres to the bias applying roller 10, a “discharging process” for discharging the adhered toner from the bias applying roller 10 and a “recharging process” for recharging the discharged toner are performed, which will be described later. No need.

Even when the above-mentioned image forming process and cleaning process are repeated, toner does not accumulate on the intermediate transfer body 6 and the bias applying roller 10, and the transfer performance of the intermediate transfer body 6 and Bias applying roller 1
No change was observed in the charging performance of 0.

Next, four color toners (yellow, cyan,
In the full-color image forming mode to obtain a full-color print using magenta and black), A4 size paper (transfer material) is conveyed in the short side direction (length 210 mm) to print characters, line patterns, and solid color images. When formed, the transfer residual toner amount was the same as in the monocolor image forming mode for the yellow, magenta, cyan, and black single-color image portions, but an image in which two or more color toners such as red, green, and blue overlap was formed. A large amount of transfer residual toner was observed in the portion.

When the bias applying roller 10 is brought into contact with the intermediate transfer member 6 to apply the same bias as in the case of mono-color, the transfer residual toner Ta is positively charged with a reverse polarity as shown in FIG. Became toner Tb and transferred to the photoconductor 1 as toner Tc at the primary transfer nip portion N. However, as shown in FIGS.
Also, adhesion of the toner Td, which is a part of the transfer residual toner Ta, was observed.

Therefore, as a discharging step after charging the toner corresponding to the image area of the intermediate transfer member 6, a DC bias of -1 kV is applied to the bias applying roller 10 from the cleaning bias power source 12 as shown in FIG. When applied, the adhered toner Td was electrostatically discharged to the intermediate transfer body 6 as the toner Te. Since the discharged toner Te has a negative polarity, it remains on the surface of the intermediate transfer member 6 without being collected by the photosensitive member 1 at the primary transfer nip portion N.

Then, as shown in FIG.
When e passes through the bias applying roller 10 as a recharging step, it is positively charged by applying an AC bias and a positive DC bias from the cleaning bias power source 12, and is electrostatically exposed at the primary transfer nip portion N. Recovered by body 1. At this time, it takes 5 seconds to charge the transfer residual toner, 5 seconds to discharge the toner adhering to the bias applying roller 10, and 5 seconds to return the discharged toner to the position facing the bias applying roller 10, and 5 seconds to recharge. The rotation (cleaning process) required 15 seconds.

FIG. 8 shows the mono-color and full-color image forming row modes (including the post-rotation step (cleaning step)) and the conventional mono-color image forming row mode (rear) in the first embodiment of the present invention. FIG. 6 is a diagram showing an integrated rotation speed and an integrated rotation time of the photoconductor 1 during a rotation process (including a cleaning process).

As is clear from this figure, in the full-color image forming mode according to the first embodiment of the present invention, the pre-rotation is 5 seconds before the image forming operation is started, the image formation is 5 seconds per color, and the post-rotation is performed. It took 15 seconds, for a total of 40 seconds. Further, in the mono-color image forming mode according to the first embodiment of the present invention, it takes 5 seconds for the pre-rotation, 5 seconds for the image formation, and 5 seconds for the post-rotation before the image forming operation is started.
It was 5 seconds.

In the pre-rotation step, the photosensitive member 1, the intermediate transfer member 6, and the drive motor for transferring the transfer material are started up.
Start-up of a rotary motor of a polygon mirror (not shown) for image exposure, adjustment of laser light amount for image exposure, control of electric potential of photoconductor 1, toner agitation of developing devices 4 and 5, toner remaining amount detection, fixing device 8. This is the process of preparing for image formation such as temperature control.

On the other hand, when the same post-rotation as in the full-color image forming mode is performed in the mono-color image forming mode as in the prior art, the required time is 25 seconds, so that the operation time in the mono-color image forming mode is 10 seconds. It has become possible to shorten it. Further, as the time is shortened, the total number of rotations of the photoconductor 1 can be reduced to 9 from the conventional 15 rotations in the mono-color image forming mode.

Next, the life of the photoconductor 1 will be described with reference to FIG.

The photoconductor 1 used is a photoconductor due to scratches on the surface of the photoconductor 1 and a decrease in chargeability when the photoconductor 1 is endured by the one-sheet intermittent printing in the conventional mono-color image forming mode involving the above-mentioned discharging process. 1 life is 10
It was about a thousand. Similarly, in the full-color image forming mode, the life of the photoconductor 1 was about 6,000 sheets. Further, the number of images formed corresponding to the life of the photoconductor 1 according to the usage ratio of mono-color and full-color is as shown in FIG. 9, and according to the first embodiment of the present invention described above, in the mono-color image forming mode. Photoreceptor 1 for image formation
Since the number of rotations can be reduced by about 40%, the maximum service life of the photoconductor 1 is about 21,000 when the number of image formations is about 11,000 when used in the mono color mode.

As described above, in the present embodiment, in the full-color image forming mode in which the amount of secondary transfer residual toner is large, the intermediate transfer body 6 can be reliably cleaned and the amount of secondary transfer residual toner is small. In the color image forming mode, since it is possible to shorten the rotation time after cleaning the intermediate transfer member 6, it is possible to suppress an increase in the cumulative number of rotations of the photosensitive member 1 and the intermediate transfer member 6 to prevent the photosensitive member 1 and the intermediate transfer member 6 from rotating. The replacement life of the intermediate transfer member 6 can be extended.

Further, since the post-rotation time (intermediate transfer member cleaning time) in the mono-color image forming mode can be shortened, the time until the start of the next image forming operation can be shortened. Productivity can be improved.

<Second Embodiment> In the second embodiment, description will be made using the image forming apparatus of the first embodiment shown in FIG. The image forming operation is the same as that in the first embodiment, and in this embodiment, only the cleaning process of the intermediate transfer member 6 during the post-rotation process in this embodiment will be described.

In the above-described image forming apparatus, when the diameter of the photosensitive member 1 is 60 mm, the diameter of the intermediate transfer member 6 is 180 mm (peripheral length 565 mm), and the process speed is 113 mm / sec as described above, the intermediate transfer member 6 is The time required for cleaning one round is about 5 seconds, during which the photoconductor 1 rotates 3 times.

First, in the case of the monocolor image forming mode in which a black and white print using black toner is obtained, A
4 size paper (transfer material) in the short side direction (length 210 m
m) to form an image of characters, line patterns, solid black, etc., several percent of the black toner Ta remains on the intermediate transfer body 6 after the secondary transfer as shown in FIG. Was there.

Then, as shown in FIG. 3, when the intermediate transfer member 6 is cleaned in the post-rotation step, the bias applying roller 10 is brought into contact with the region to which the transfer residual toner (black toner Ta) is attached. Then, the cleaning bias power supply 12 adds an AC bias of 2.0 kV peak-to-peak voltage and a frequency of 1.5 kHz, and D of +20 μA.
When the C bias is applied, the transfer residual toner (black toner Ta) on the intermediate transfer body 6 is charged to the positive polarity of the opposite polarity to become the toner Tb, and most of the toner remains as the toner Tc at the primary transfer nip portion N. 1 was transferred, and the surface of the intermediate transfer member 6 could be cleaned.

At this time, almost no toner adhesion was observed on the bias applying roller 10, and the post-rotation (cleaning process) could be completed in about 5 seconds. Further, since almost no transfer residual toner adheres to the bias applying roller 10, the "exhausting step" for discharging the adhered toner from the bias applying roller 10 and the "recharging step" for recharging the discharged toner are performed. No need.

Next, four color toners (yellow, cyan,
In the full-color image forming mode to obtain a full-color print using magenta and black), A4 size paper (transfer material) is conveyed in the short side direction (length 210 mm) to print characters, line patterns, and solid color images. Formed and FIG.
As shown in FIG. 5, after the full-color toner image is collectively transferred (secondary transfer) onto the transfer material P, the bias applying roller 10 is brought into contact with the intermediate transfer body 6 to which the transfer residual toner Ta is attached, and the peak-to-peak voltage is similarly set. A DC bias of +20 μA was applied in addition to an AC bias of 2 kV and a frequency of 1.5 kHz.

Under this bias application condition, a part of the toner Tb charged by the bias application roller 10 is electrostatically charged on the photoconductor 1 at the primary transfer nip portion N.
The residual toner Tf collected as c remains on the intermediate transfer member 6. Furthermore, under this bias application condition,
No toner adhered to the bias applying roller 10.

Therefore, as shown in FIG. 11, the intermediate transfer body 6 is rotated once more and the AC bias and the DC bias are applied while the toner Tf on the intermediate transfer body 6 passes through the bias applying roller 10 again. As a result, the toner Tf was positively charged with the opposite polarity and electrostatically transferred to the photoconductor 1 at the primary transfer nip portion N, and all the toner on the intermediate transfer body 6 could be removed.

FIG. 12 shows the second embodiment of the present invention described above.
Of the photoreceptor 1 in the mono-color and full-color image forming mode (including the post-rotation step (cleaning step)) and the conventional mono-color image forming mode (including the post-rotation step (cleaning step)) It is a figure showing the number of rotations and the total rotation time.

As is clear from this figure, in the full-color image forming mode according to the second embodiment of the present invention, the pre-rotation is 5 seconds before the image forming operation is started, the image formation is 5 seconds per color, and the rear is 5 seconds. The rotation (cleaning process) took 10 seconds by rotating the intermediate transfer member 6 twice for charging the transfer residual toner, and was 35 seconds in total. Also,
In the mono-color image forming mode according to the second embodiment of the present invention, before the image forming operation is started, the pre-rotation is performed for 5 seconds, the image formation is performed for 5 seconds, and the transfer residual toner is removed during one rotation of the intermediate transfer member 6. Therefore, the post-rotation (cleaning process) required 5 seconds, which was 15 seconds in total.

On the other hand, when the same post-rotation (cleaning process) as in the full-color image forming mode is performed in the mono-color image forming mode as in the conventional case, the required time is 20 seconds. It has become possible to reduce the operating time in the color image forming mode by 5 seconds. Further, as the time is shortened, the total number of rotations of the photoconductor 1 can be reduced to 9 from the conventional 12 rotations in the monocolor image forming mode.

As described above, in the present embodiment, in the full-color image forming mode in which the secondary transfer residual toner amount is large, the intermediate transfer member 6 can be surely cleaned, and the secondary transfer residual toner amount is small. In the color image forming mode, since it is possible to shorten the rotation time after cleaning the intermediate transfer member 6, it is possible to suppress an increase in the cumulative number of rotations of the photosensitive member 1 and the intermediate transfer member 6 to prevent the photosensitive member 1 and the intermediate transfer member 6 from rotating. The replacement life of the intermediate transfer member 6 can be extended.

Further, since it is possible to shorten the post-rotation time (cleaning time) in the mono-color image forming mode, the time until the start of the next image forming operation can be shortened, so that the productivity is improved. It is possible to improve.

[0077]

As described above, according to the present invention, it is possible to reliably perform cleaning of the intermediate transfer member at the time of forming a full-color image having a large transfer residual toner amount, and to form a monochromatic image having a small transfer residual toner amount. Since it is possible to shorten the cleaning time for cleaning the intermediate transfer member at that time, it is possible to suppress the increase in the cumulative number of rotations of the image carrier as the proportion of monochromatic image formation increases, and to improve the replacement life of the image carrier. Can be long.

Further, since it is possible to shorten the cleaning time for cleaning the intermediate transfer member at the time of forming a monochromatic image, the time until the start of the next image forming operation can be shortened, and therefore the productivity is improved. It is possible to improve.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to first and second embodiments of the present invention.

FIG. 2 is a diagram for explaining a cleaning process of the intermediate transfer member according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining a cleaning process of the intermediate transfer member according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining a cleaning process of the intermediate transfer member according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining a cleaning process of the intermediate transfer member according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining a cleaning process of the intermediate transfer member according to the first embodiment of the present invention.

FIG. 7 is a diagram for explaining a cleaning process of the intermediate transfer member according to the first embodiment of the present invention.

FIG. 8 is a diagram for explaining the rotation speed of the photoconductor and the rotation time of the photoconductor in the mono color mode and the full color mode in the first embodiment of the present invention and the conventional example.

FIG. 9 is a diagram showing the usage ratios of the mono color mode and the full color mode in the first embodiment of the present invention and the conventional example, and the number of images formed according to the life of the photoconductor.

FIG. 10 is a diagram for explaining a cleaning process of the intermediate transfer member according to the second embodiment of the present invention.

FIG. 11 is a diagram for explaining a cleaning process of the intermediate transfer member according to the second embodiment of the present invention.

FIG. 12 is a diagram for explaining the rotation speed of the photoconductor and the rotation time of the photoconductor in the mono color mode and the full color mode in the second embodiment of the present invention and the conventional example.

FIG. 13 is a schematic diagram showing an image forming apparatus including an intermediate transfer member in a conventional example.

[Explanation of symbols]

1 Photoreceptor (Image Carrier) 2 Charging Roller 3 Exposure Device 4, 5 Developing Device 6 Intermediate Transfer Body 7 Secondary Transfer Belt (Secondary Transfer Member) 7a Secondary Transfer Roller (Secondary Transfer Member) 8 Fixing Device 8a Fixing Roller 8b Pressure roller 9 Cleaning device 9a Cleaning blade 10 Bias applying roller (bias applying member) 11 Primary transfer bias power supply 12 Cleaning bias power supply (bias applying means) 13 Secondary transfer bias power supply

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA41 ED02 ED24 EE01 EF13                       FA28 FA35                 2H030 AD08 AD17 BB02 BB23 BB25                       BB42 BB53 BB54 BB56 BB63                 2H200 FA02 FA09 GA14 GA34 GA44                       GA47 GA49 GA50 GA59 GB12                       GB22 GB25 HA02 HA28 HB12                       HB48 JA02 JA05 JA28 JA29                       JB06 JB16 JB18 JC02 JC12                       JC13 JC18 LA24 LB03 LB08                       LB15 LB18 LB38 LB39 NA02                       NA06 NA09 NA10 PA03 PA10                       PA26 PB34

Claims (3)

[Claims] 1. At least one rotatable image carrier on which an electrostatic latent image is formed, and a toner image of a single color or a plurality of different colors by developing the electrostatic latent image formed on the image carrier. A plurality of developing devices that form a toner image, and the toner image formed on the image bearing member is abutted against the image bearing member at the primary transfer portion.
A toner image transferred onto the intermediate transfer body, which is brought into contact with the rotatable intermediate transfer body which is primarily transferred at the primary transfer section by the application of the next transfer bias, and the intermediate transfer body at the secondary transfer section. Is secondarily transferred to the transfer material conveyed to the secondary transfer portion by the application of the secondary transfer bias in the secondary transfer portion 2
The secondary transfer member and the intermediate transfer body are disposed so as to be able to come into contact with and separate from the intermediate transfer body located downstream of the secondary transfer section and upstream of the primary transfer section along the rotational direction of the intermediate transfer body. A bias applying member and a bias applying unit for applying a bias to the bias applying member are provided, and when forming a color image, the toner images of different colors formed on the image carrier by the plurality of developing devices are transferred to the intermediate transfer. After being superimposed and transferred onto the body, it is collectively transferred onto the transfer material by the secondary transfer member, and at the time of forming a monochromatic image, a monochromatic image formed on the image carrier by an arbitrary developing device of the plurality of developing devices. At the time of non-image formation after the toner image is transferred onto the intermediate transfer body and then transferred onto the transfer material by the secondary transfer member, and the toner image on the intermediate transfer body is secondarily transferred onto the transfer material. The bias applying member to the intermediate The charge polarity of the transfer residual toner remaining on the intermediate transfer body after the secondary transfer is controlled by the bias application from the bias applying unit, and the charge is electrostatically transferred to the primary transfer portion. In the image forming apparatus, which transfers the toner to the image carrier side to clean the surface of the intermediate transfer body, at least the toner from the bias applying unit is used when cleaning the surface of the intermediate transfer body during non-image formation after the monochromatic image formation. Only by applying a DC bias having a polarity opposite to the normal charging polarity of the toner of the image to the bias applying member, the transfer residual toner remaining on the rotating intermediate transfer member is normally charged. At the time of non-image formation after the color image formation, the toner is charged to a polarity opposite to the polarity and electrostatically transferred to the side of the image carrier rotating in the primary transfer portion. At the time of cleaning the surface of the intermediate transfer member, at least a DC bias having a polarity opposite to the regular charging polarity is applied to the bias applying member from the bias applying unit and remains on the rotating intermediate transfer member. After the transfer residual toner is charged to a polarity opposite to the regular charging polarity and electrostatically transferred to the rotating image carrier side at the primary transfer portion, the bias applying means further A DC bias having the same polarity as the regular charging polarity is applied to the bias applying member to electrostatically transfer a part of the transfer residual toner adhered to the bias applying member from the intermediate transfer member to the intermediate transfer member. The discharged toner is applied to the bias applying member by applying a DC bias having at least the opposite polarity to the regular charging polarity from the bias applying means to the body, and discharging the discharged toner. Is allowed to transfer to the image bearing member which is rotating at charging polarity reversed polarity was re-charged electrostatically the primary transfer portion of the normal, the image forming apparatus characterized by. 2. The cumulative number of rotations of the image carrier during the cleaning of the surface of the intermediate transfer body during the non-image formation after the monochromatic image formation is the intermediate transfer body during the non-image formation after the color image formation. With respect to the cumulative number of rotations of the image carrier during surface cleaning, the transfer residual toner adhering to the bias applying member during cleaning of the surface of the intermediate transfer member during non-image formation after the color image formation A small amount corresponding to the cumulative number of revolutions of the image carrier when the part of the toner is discharged to the side of the intermediate transfer member and when the discharged toner is recharged and transferred to the side of the image carrier. The image forming apparatus according to claim 1. 3. The cumulative rotation time of the image carrier during the cleaning of the surface of the intermediate transfer body during the non-image formation after the monochromatic image formation is the intermediate transfer body during the non-image formation after the color image formation. With respect to the cumulative rotation time of the image carrier during surface cleaning, the transfer residual toner adhering to the bias applying member during cleaning of the surface of the intermediate transfer member during non-image formation after the color image formation It is short by the amount corresponding to the cumulative rotation time of the image carrier when a part of the toner is discharged to the intermediate transfer body side and when the discharged toner is recharged and transferred to the image carrier side. The image forming apparatus according to claim 1.