JP2002006577A - Image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove toner on a transfer belt, without having to add a new member and to restrain damage given to the transfer belt in the midst of cleaning to the minimum. SOLUTION: By applying a bias, having both positive and negative polarities to transfer bias power sources 23 for 2nd and 3rd colors among the transfer bias power sources 23 of respective transfer rollers 4, the toner on the transfer belt 14 is transferred reversely to a photosensitive drum 1 and removed. Then, the image-forming device is provided with a 1st cleaning mode, in which the circumferential speed of the belt 14 is nearly equal to that of the drum 1 and a 2nd cleaning mode, in which the difference of the circumferential speed between them is 10%, and the 1st cleaning mode is carried out in the case of estimating that toner amount on the belt 14 is a minute amount and the 2nd cleaning mode is carried out when the toner amount on the belt 14 is expected to be large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a printer or a copying machine.

[0002]

2. Description of the Related Art In recent years, with the spread of electrophotographic color image forming apparatuses, there has been an increasing demand for high-speed color output in addition to a demand for high-quality color images. In order to meet this demand, several proposals have been made for image forming systems. Among them, a yellow (hereinafter, referred to as “Y”) toner and a magenta (hereinafter, referred to as “M”), which are called a tandem type, are proposed. ) Toner, cyan (hereinafter, referred to as
Toner) and black (hereinafter referred to as “B”).
k)), each of the toner images is formed on a drum-shaped image carrier, and is sequentially transferred to a transfer material conveyed by a transfer belt as a transfer material carrier by respective transfer means. There is a color image forming method for fixing.

FIG. 5 shows an example of a conventional tandem type color image forming apparatus.

When an image forming operation is started, photosensitive drums 101Y, 101M, 101C and 101 serving as image carriers are provided.
Bk and the transfer belt 114 serving as a transfer material carrier start to rotate in the direction of the arrow at a predetermined process speed. In the Y image forming station Pa, the photosensitive drum 101Y is uniformly negatively charged by the charging roller 102Y, and an electrostatic latent image is formed according to image information by the scanning beam 112Y from the exposure device 111Y.

The electrostatic latent image is developed by a developer (toner) charged to a negative polarity in a developing unit 108Y as a developing means, and a Y toner image, that is, a developer image is formed.

On the other hand, the transfer material P loaded on the transfer material cassette 115 is transported to the registration roller 119, where it is further transported onto the transfer belt 114 in synchronization with the toner image on the photosensitive drum 101Y. You.

The transfer material P is firstly transferred by the transfer belt 114.
When the toner image on the photosensitive drum 101Y is conveyed to the transfer unit of the color, the transfer roller 10 as a transfer unit to which a positive transfer bias is applied from the transfer bias power supply 122Y
4Y is transferred onto the transfer material P.

[0008] In synchronization with the transfer material P being conveyed by the transfer belt 114, M, C, and Bk toner images are formed by the downstream image forming stations Pb to Pd. Further, a transfer bias power supply 12
The transfer rollers 104M, 104C, and 104Bk to which positive biases are applied from 2M, 122C, and 122Bk are transferred onto the transfer material P in a superimposed manner. The image forming stations Pb, Pc, and Pd have the same configuration as the above-described image forming station Pa, and differ only in the color of the toner.

The transfer material P to which the Y, M, C, and Bk toner images have been transferred is separated from the transfer belt 114 and
Then, the toner image is melted and fixed to obtain a color image.

The photosensitive drums 101Y, 101M, 101
C, the toner remaining on 101Bk is a cleaning device 109Y, 109M, 1 such as a fur brush or a blade.
09C, 109Bk, waste toner container 1
10Y, 110M, 110C, and 110Bk.

[0011]

In the above-described color image forming apparatus, since the toner image is always formed on the transfer material, the transfer belt is not stained with the toner. However, if there is fogging toner, if the transfer material is not conveyed due to paper feed jam, and the image is formed, or if the specified transfer material and the image size are different, the transfer belt An image is formed as it is on the top.

Further, the color image forming apparatus may form a toner image on the transfer belt on a trial basis to control the image density. In such a case, if the transfer belt is not cleaned, This causes back contamination on the transfer material on which the image is transferred.

Therefore, a method of cleaning the toner on the transfer belt using a blade, a brush, or the like is considered. However, this method causes abrasion on the transfer belt, making it impossible to perform normal transfer and causing an image defect. become. In addition, a new waste toner container for storing waste toner collected by blades and brushes is required,
In addition to pressing down the space of the color image forming apparatus main body, the cost is increased.

Such a problem also applies to an image forming apparatus of a system in which a toner image formed on a photosensitive drum is primarily transferred to an intermediate transfer member and further secondary-transferred to a transfer material.

Accordingly, a main object of the present invention is to effectively clean the developer on the transfer material carrier without adding a new member, and to minimize damage to the transfer material carrier during cleaning. It is an object of the present invention to provide an image forming apparatus which can be reduced to a minimum.

Another object of the present invention is to effectively clean a developer on an intermediate transfer member without adding a new member, and to minimize damage to the intermediate transfer member during cleaning. It is an object of the present invention to provide an image forming apparatus capable of performing the following.

[0017]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A plurality of image carriers on which developer images are formed, a transfer material carrier for transferring a transfer material to the plurality of image carriers, and a developer image on the image carrier carried on the transfer material carrier And a plurality of transfer means for transferring to a transferred transfer material, wherein the developer on the transfer material carrier is reverse-transferred to at least one of the plurality of image carriers to perform cleaning. In the apparatus, a first cleaning mode in which the surface moving speed of the transfer material carrier and the surface moving speed of the image carrier are substantially constant, a surface cleaning speed of the transfer material carrier and a speed of the image carrier. A second cleaning mode having a different surface moving speed, wherein when the developer on the transfer material carrier is reversely transferred to the image carrier for cleaning, the first cleaning mode is performed under predetermined conditions. Cleaning mode or the second An image forming apparatus characterized by selecting and executing a training mode.

According to one embodiment of the present invention, in the second cleaning mode, the speed difference between the surface moving speed of the transfer material carrier and the surface moving speed of the image carrier is three.
%.

According to another embodiment of the present invention, the predetermined condition is an estimated remaining amount of the developer on the transfer material carrier.

According to another embodiment of the present invention, when a transfer material conveyance error occurs, the second cleaning mode is selected.

According to another aspect of the present invention, a plurality of image carriers on which a developer image is formed, an intermediate transfer member onto which the developer images on the plurality of image carriers are transferred, and the image carrier And a plurality of transfer means for transferring the developer image on the intermediate transfer body, and reversely transfers the developer on the intermediate transfer body to at least one of the plurality of image carriers. A first cleaning mode in which the surface transfer speed of the intermediate transfer member and the surface transfer speed of the image carrier are substantially constant; And a second cleaning mode in which the surface movement speed of the body is different, and when the developer on the intermediate transfer body is reverse-transferred to the image bearing member for cleaning, the first cleaning mode is performed under predetermined conditions. Cleaning mode or Image forming apparatus is provided, characterized in that selects and executes the serial second cleaning mode.

According to one embodiment of the present invention, the difference between the surface moving speed of the intermediate transfer member and the surface moving speed of the image carrier is more than 3%.

According to another embodiment of the present invention, the predetermined condition is an estimated residual amount of the developer on the intermediate transfer member.

According to another embodiment of the present invention, the developer image on the intermediate transfer member transferred from the image carrier is transferred to a transfer material.

According to another embodiment of the present invention, when a transfer material conveyance error occurs, the second cleaning mode is selected.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS. First, the color image forming apparatus of the present embodiment is shown in FIG.
This will be described below.

In FIG. 1, the color image forming apparatus of the present embodiment includes first, second, third, and fourth image forming stations Pa, Pb, Pc, and P as four image forming means.
“d” is juxtaposed along the moving direction of the transfer belt 14 as the transfer material carrier.

The transfer belt 14 has four rollers 13a, 1
3b, 13c, 13d is stretched, rotated in the direction of the arrow,
The transfer material P is transported. The transfer belt 14 has a thickness of 50 to 300 μm and a volume resistivity of 10 ⁹ to 10 ¹⁶ Ω · cm.
Resin material such as PVdP (polyvinylidene fluoride), polyamide, polyimide, PET (polyethylene terephthalate), polycarbonate, etc.
Rubber materials such as chloroprene rubber, EPDM (ethylene-propylene-diene terpolymer), NBR (nitrile butadiene rubber), and urethane rubber having a volume resistivity of about 2 mm and 10 ⁹ to 10 ¹⁶ Ω · cm are used.

In some cases, a conductive filling material such as carbon, ZnO, SnO ₂ , or TiO ₂ may be dispersed in these materials to provide a volume resistivity of 10 ⁷ to 10 ¹¹ Ω · cm.
It may be adjusted to the extent.

First to fourth image forming stations Pa to
Pd has the same structure, but differs in that an image is formed with toners (developers) of different colors, that is, yellow Y, magenta M, cyan C, and black Bk.

First to fourth image forming stations Pa to
Pd denotes photosensitive drums 1Y and 1Y serving as image carriers, respectively.
M, 1C, 1Bk, charging rollers 2Y, 2M, 2C, 2B
k, cleaners 9Y, 9M, 9C, 9Bk, a drum unit including waste toner containers 10Y, 10M, 10C, 10Bk, developing sleeves 5Y, 5M, 5C, 5Bk, developer applying rollers 6Y, 6M, 6C, 6Bk, and developing. Developing units 8Y, 8C, 8M, and 8Bk each including a yellow developer (toner) 3Y, a magenta toner 3M, a cyan toner 3C, and a black toner 3Bk, including the agent application blades 7Y, 7M, 7C, and 7Bk; Exposure device 11
Y, 11C, 11M, and 11Bk, and includes a drum unit and developing units 8Y, 8C, 8M, and 8Bk.
Are configured as an integrated process cartridge.

The exposure device 11Y is composed of a scanner unit or an LED array that scans a laser beam with a polygon mirror, and irradiates the photosensitive drum 1Y with a scanning beam 12Y modulated based on an image signal.

The photosensitive drums 1Y, 1Y
Transfer rollers 4Y, 4M, 4C, and 4Bk are provided as transfer units so as to face the transfer bias power supplies 23Y, 23M, and 23B.
C, 23Bk.

The transfer rollers 4Y to 4Bk are made of, for example, an EP in which a metal core is adjusted to a volume resistivity of 10 ⁵ to 10 ⁸ Ω · cm.
A configuration covered with an elastic body such as DM, urethane rubber, or NBR can be used.

In FIG. 1, suffixes Y, M, and suffixes indicating constituent members of each of the image forming stations Pa to Pd.
C and Bk represent the colors of the toner.

When the image forming operation is started, the photosensitive drums 1Y to 1Bk, the transfer belt 14, and the like start rotating at a predetermined process speed in the direction of the arrow. The photosensitive drum 1Y is uniformly charged to a negative polarity by the charging roller 2Y, and an electrostatic latent image according to image information is formed by the scanning beam 12Y from the exposure device 11Y.

The toner 3Y in the developing unit 8Y is negatively charged by the developer application blade 7Y and is applied to the developing sleeve 5Y. Then, when the photosensitive drum 1Y rotates and the electrostatic latent image formed on the photosensitive drum 1Y reaches the developing sleeve 5Y, the electrostatic latent image is visualized by the negative polarity toner by the reversal developing method, and the Y toner image is formed on the photosensitive drum 1Y. (Developer image) is formed.

On the other hand, the transfer material P loaded on the transfer material cassette 15 is picked up by a half-month paper feed roller 16, separated one by one by a sheet material separating roller 17, and registered by a conveying roller 18 to a registration roller 19.
Transported to The transfer material P is conveyed onto the transfer belt 14 by the registration roller 19 in synchronization with the toner image on the photosensitive drum 1Y.

The transfer material P includes a suction roller 20 and a roller 13
a, the toner image on the photosensitive drum 1Y is transferred onto the transfer material P by the transfer roller 4Y to which a positive transfer bias is applied. In synchronization with the transfer material P being conveyed by the transfer belt 14, M, C, and Bk toner images are formed by the second to fourth image forming stations Pb to Pd, and further, the transfer rollers 4M, The image is transferred to the transfer material P by 4C and 4Bk.

The transfer material P on which the Y, M, C, and Bk toner images have been transferred is separated from the transfer belt 14 and
, Where the toner image is fused and fixed to obtain a color image.

The toner remaining on the photosensitive drums 1Y, 1M, 1C and 1Bk is removed by cleaning devices 9Y, 9M, 9C and 9Bk such as fur brushes and blades.
The waste toner containers 10Y, 10M, 10C, and 10Bk are stored.

As shown in FIG. 1, the transfer bias power supplies 23Y, 23M, 23C and 23Bk of this embodiment
Transfer bias power supplies 23 for the most upstream side and the most downstream side in the transport direction, ie, for the first color (Y) and for the fourth color (Bk).
Y and 23Bk generate positive biases for normal image formation, and these first and fourth transfer bias power supplies 23 are used.
Y, for second color (M), third color (C) sandwiched between 23Bk
Transfer bias power supplies 23M and 23C can generate both positive and negative biases.

In this configuration, when a predetermined transfer belt cleaning timing is reached, for example, after the end of a print job, the end of image density control, the jam processing, or the power-on, the transfer rollers 4Y and 4Bk of the first and fourth colors are applied. Positive bias + from transfer bias power supplies 23Y and 23Bk
1.5 kV is applied, while the transfer bias power supplies 23M, 23C are applied to the transfer rollers 4M, 4C for the second and third colors.
A negative bias of -1.5 kV is applied from C.

The toner on the transfer belt 14 is mainly a negative polarity toner having a regular charging polarity, but some of the toners have been reversed to a positive polarity having the opposite charging polarity or non-polar toners. Exists. Therefore, first, a positive bias, which is the polarity at the time of transfer, is applied to the transfer roller 4Y of the first color,
The toner, which has become positive, is reversely transferred to the photosensitive drum 1Y and is collected by the cleaner 9Y, and the toner on the transfer belt 14 is charged to a negative polarity, which is a normal charge polarity. The mechanism of the charging to the negative polarity is considered as follows. FIG. 2 is an enlarged explanatory view of the transfer nip of the first color during transfer belt cleaning. During cleaning of the transfer belt, no latent image is formed on the photosensitive drum 1Y, and the surface potential of the photosensitive drum 1Y at the transfer nip remains as it was when charged negatively. Then, the potential difference between the negative surface potential of the photosensitive drum 1Y and the transfer roller 4Y to which the positive bias is applied exceeds the discharge threshold, and discharge occurs in the transfer nip. At this time, the generated positive charges and negative charges move due to the negative potential on the surface of the photosensitive drum 1Y and the positive potential applied to the transfer belt 14, respectively. The positive charges are transferred to the surface of the photosensitive drum 1Y, and the negative charges are transferred. The toner reaches the toner on the belt 14 and the transfer belt 14. The negative charge that has reached the toner charges the toner that has been inverted to a positive polarity or the nonpolar toner to a negative polarity.

Next, at the transfer position of the second color, a negative bias is applied from the transfer roller 4M to reversely transfer the negative toner passing through the first color to the photosensitive drum 1M of the second color. And collect with a cleaner 9M. The toner that has not been collected here has either positive polarity, non-polarity, or negative polarity.

Therefore, at the transfer position of the third color, by applying a negative bias from the transfer roller 4C,
Of the toner not collected in the second color, the negative polarity toner is reversely transferred to the photosensitive drum 1C and collected by the cleaner 9C. At this time, the photosensitive drum 1C has positive polarity, non-polarity, or negative polarity, but has a small charge amount.
Is not positively charged. The mechanism of charging to the positive polarity can be described in the same manner as the mechanism to charging to the negative polarity described above.

Therefore, by applying a positive bias to the transfer roller 4Bk in the fourth color, the transfer belt 14
The positive toner remaining on the upper surface is reversely transferred to the photosensitive drum 1Bk and collected by the cleaner 9Bk. Thus, the cleaning of the toner on the transfer belt 14 is completed.

Further, in this embodiment, when the toner on the transfer belt 14 is cleaned, the peripheral speed of each transfer portion of the transfer belt 14 and the peripheral speed of each transfer portion of each of the photosensitive drums 1Y to 1Bk are substantially constant. In the first transfer belt cleaning mode (hereinafter referred to as "cleaning mode"), when the toner on the transfer belt 14 is cleaned, the peripheral speed of the transfer belt 14 is about 10 times lower than the peripheral speed of each of the photosensitive drums 1Y to 1Bk. The switching control is performed by the CPU as the control means in the second cleaning mode in which the cleaning speed is increased by%. However,
In the first cleaning mode, the peripheral speed of the transfer belt 14 and the peripheral speed of the photosensitive drums 1Y to 1Bk do not completely match due to variations in mechanical accuracy of the components. In addition, a slight difference in peripheral speed may be provided in order to enhance the stability of transferability and transportability. In practice, however, there is a difference in peripheral speed of about 0 to ± 3%. . The peripheral speed of each photosensitive drum is not limited to the above, and may be 10% faster than the peripheral speed of the transfer belt.

In general, when a peripheral speed difference is provided between the photosensitive drum and the transfer belt, the toner on the transfer belt is forcibly moved by a frictional force generated by the peripheral speed difference, and the transfer belt and the toner are transferred. The effect of the van der Waals force is weakened, and the toner is more strongly affected by the electric field, so that the cleaning ability is dramatically improved. Therefore, the second cleaning mode 2 exhibits stronger cleaning performance than the first cleaning mode 1.

FIG. 3 shows the difference between the peripheral speed of the transfer belt and the peripheral speed of the photosensitive drum, and the residual toner remaining on the transfer belt after forming the M solid image on the transfer belt and then performing the toner cleaning. FIG. A border line of the toner concentration remaining on the transfer belt (BORDER) in FIG. 3 indicates a threshold value that can be practically used. If the border line is equal to or less than the border line, the cleaning is performed well.

Therefore, in order to efficiently clean the toner on the transfer belt, the peripheral speed difference between the photosensitive drum and the transfer belt must be at least + 6% or more (the peripheral speed of the transfer belt is faster than the peripheral speed of the photosensitive drum). ) Or -3% or less (the peripheral speed of the transfer belt is lower than the peripheral speed of the photosensitive drum).

Therefore, in order to obtain an advantage that the cleaning time can be shortened and a better cleaning performance, in the present embodiment, it is set to + 10%. If there is a peripheral speed difference between the photosensitive drum and the transfer belt, that is, if the peripheral speed difference exceeds 3%, the toner cleaning performance due to the peripheral speed difference is improved.
The same applies to toners of colors other than M.

While good cleaning performance can be obtained as described above, if the peripheral speed is varied, the transfer belt and the photosensitive drum rub against each other, so that the surfaces of the transfer belt and the photosensitive drum are scraped and damaged. There is a risk.

Therefore, when the toner on the transfer belt is expected to be extremely small, such as fog toner, such as when the print job ends normally or when the power is turned off and then turned on again after the print job has ended normally. The first cleaning mode is executed. On the other hand, in a density control mode or a color misregistration control mode for controlling the density of a toner image formed on the photosensitive drum, a sensor disposed near the upper side of the transfer belt 14
For example, after detecting the density or position (detection timing) of the test toner image transferred onto the photosensitive drum, or when the transfer material is not conveyed due to a jam after forming the toner image on the photosensitive drum. When it is expected that a large amount of toner has been transferred onto the transfer belt 14, the second cleaning mode is executed, so that the cleaning mode can be switched according to the required cleaning ability.

As described above, according to this embodiment, when the toner on the transfer belt is reversely transferred to the photosensitive drum for cleaning, the surface movement speed of the transfer belt and the surface movement speed of the photosensitive drum are substantially constant. By selecting and executing one of a certain first cleaning mode and a second cleaning mode having a different surface moving speed based on a predetermined condition, that is, an estimated toner amount on the transfer belt, The toner can be effectively cleaned, and damage to the transfer belt and the photosensitive drum can be minimized.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. The same members as those described above are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 4, the color image forming apparatus of this embodiment includes an intermediate transfer member 25 as a member corresponding to the transfer belt of the first embodiment. 4 image forming stations Pa to Pd, transfer rollers 4Y to 4Bk, and transfer bias power supplies 23Y to 23
Bk has a similar configuration.

The intermediate transfer member 25 of this embodiment is a belt member that rotates endlessly, and has a thickness of 50 to 300 μm, a volume resistivity of about 10 ⁹ to 10 ¹⁶ Ω · cm, PVdF, polyamide,
Resin material such as polyimide, PET, polycarbonate, etc. and thickness 0.5 to 2 mm, volume resistivity 10 ⁹ to 10 ¹⁶ Ω
For example, rubber materials such as chloroprene rubber, EPDM, NBR (nitrile butadiene rubber), and urethane rubber of about cm are used.

In some cases, a conductive filling material such as carbon, ZnO, SnO ₂ , or TiO ₂ may be dispersed in these materials to provide a volume resistivity of 10 ⁷ to 10 ¹¹ Ω · cm.
The degree may be adjusted. The belt is stretched around a driving roller 13a, a driven roller 13b, and a transfer opposing roller 13c.

First to fourth image forming stations Pa to P
The toner images of the respective colors formed on the respective photosensitive drums 1Y to 1Bk at d are overlap-transferred onto the intermediate transfer body 25 as the intermediate transfer body 25 moves.

On the other hand, the transfer material P is transferred from the paper feed cassette 15 to the feed roller 17, the transport roller pair 18, and the registration roller pair 19 in synchronization with the formation of the color image on the intermediate transfer body 25.
And is transported to the transfer section T2 via.

In the transfer section T 2, the transfer roller 26 is in pressure contact with the intermediate transfer body 25, and a transfer bias is applied when the transfer material P passes between the intermediate transfer body 25 and the transfer roller 26. The toner image primarily transferred to the body 25 is secondarily transferred to the transfer material P.

The transfer material P is conveyed to the fixing device 21, where the toner image is fused and fixed, and a color image is obtained.

Generally, in a color image forming apparatus of the intermediate transfer body type, the secondary transfer efficiency does not become 100%, and a slight amount of toner remains on the intermediate transfer body at the end of a print job. Further, when a toner image for controlling the image density is formed on the intermediate transfer member, or when a jam occurs, the toner image remains as it is.

For this reason, a roller similar to a transfer roller called an intermediate transfer member cleaning roller is disposed downstream of the secondary transfer position, and a bias is applied to the transfer roller so that the toner remaining on the intermediate transfer member has a specific polarity ( For example, positive polarity)
However, by applying the present invention described in the first embodiment, it is also possible to clean the residual toner on the intermediate transfer member.

That is, in the above configuration, as in the first embodiment, when a predetermined intermediate transfer belt cleaning timing is reached, for example, after the end of a print job, after the end of image density control, after a jam clearance, or when the power is turned on, the first and second timings are set. A transfer bias power supply 23 is provided to the transfer rollers 4Y and 4Bk of the fourth color.
A bias for the positive electrode of +1.5 kV is applied from Y and 23Bk, while the transfer rollers 4M and 4M for the second and third colors are applied.
A negative bias of -1.5 kV is applied to C from the transfer bias power supplies 23M and 23C.

At the time of this cleaning, a first intermediate transfer member cleaning mode (hereinafter referred to as a "cleaning mode") in which the peripheral speed of the intermediate transfer member 25 and the peripheral speed of the photosensitive drums 1Y to 1Bk are constant, and A second cleaning mode 2 is set in which the peripheral speed of the intermediate transfer body 25 is + 10% faster than the peripheral speed of the photosensitive drums 1Y to 1Bk when cleaning the toner on the body 25. However, in the first cleaning mode, the peripheral speed of the intermediate transfer body 25 and the photosensitive drum 1
The peripheral speeds of Y to 1Bk do not completely match due to variations in the mechanical accuracy of the components. In addition, a slight difference in peripheral speed may be provided in order to enhance the stability of transferability and running performance. Therefore, in practice, a difference in peripheral speed of about 0 to ± 3% is considered to be substantially constant here.

When the amount of toner on the intermediate transfer body 25 is expected to be extremely small, such as when the print job ends normally or when the power is turned off and then turned on again after the normal end of the print job, the first operation is performed. Execute the cleaning mode. On the other hand, when a toner image is formed on the intermediate transfer body 25 for image density control, etc.
The second cleaning mode is executed when a large amount of toner is expected to be transferred onto the intermediate transfer body 25, such as when the transfer material is not conveyed due to a jam after the toner image is transferred thereon. did.

In general, in a color image forming apparatus of the intermediate transfer body type, a toner image is formed on the intermediate transfer body 25, so that the surface of the intermediate transfer body is scraped by rubbing, and if toner fusion occurs or rubbing scratches increase, the intermediate transfer is performed. An appropriate image cannot be formed on the body, and the image quality may be greatly impaired.

Therefore, as in the present embodiment, the toner on the intermediate transfer member can be effectively cleaned by switching the cleaning mode in accordance with the required cleaning ability, and the intermediate transfer member, Damage to the photosensitive drum can be minimized.

The image forming apparatus according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. That is, the transfer unit is not limited to the transfer roller, but may be another unit such as a transfer blade, a transfer brush, or a corona charger, and the order of colors may be arbitrary. Further, the transfer bias and the charging potential of the photosensitive drum may be changed, and the four colors may have different values. In each of the above embodiments, the peripheral speed difference is 10%, but the optimum value of the peripheral speed difference varies depending on the process speed, the photosensitive drum diameter, the bias setting, and the like. Although the peripheral speed difference in each of the above embodiments was such that the cleaning time was shortened, the peripheral speed of the transfer belt and the intermediate transfer member was higher than the peripheral speed of the photosensitive drum. The peripheral speed difference may be provided by making the peripheral speed lower than the peripheral speed. Further, even when the amount of toner remaining on the transfer belt or the intermediate transfer member is predicted based on the image data, the switching between the first cleaning mode and the second cleaning mode is suppressed accordingly. Good.

In the above-described embodiment, the case where the number of cleaning modes is two has been described. However, it is also possible to provide a cleaning mode having a further difference in peripheral speed, and to finely switch the cleaning mode in accordance with the expected residual toner amount. .

[0074]

As is clear from the above description, according to the image forming apparatus of the present invention, the surface moving speed of the transfer material carrier and the surface moving speed of the image carrier are substantially constant. And a second cleaning mode in which the surface movement speed of the transfer material carrier and the surface movement speed of the image carrier are different. By performing the first cleaning mode or the second cleaning mode under predetermined conditions when performing reverse cleaning on the image carrier for cleaning, the effect can be obtained without adding a new member. The developer on the transfer material carrier can be cleaned, and damage to the transfer material carrier during cleaning can be minimized.

A first cleaning mode in which the surface moving speed of the intermediate transfer member and the surface moving speed of the image carrier are substantially constant; a surface cleaning speed of the intermediate transfer member and a surface moving speed of the image carrier; And a second cleaning mode, wherein the developer on the intermediate transfer member is reversely transferred to the image carrier for cleaning, and the first cleaning mode or the By selecting and executing the second cleaning mode, the developer on the intermediate transfer member can be effectively cleaned without adding a new member, and damage to the intermediate transfer member during cleaning is minimized. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is an enlarged explanatory view of a transfer nip during transfer belt cleaning.

FIG. 3 is a graph showing a relationship between a peripheral speed difference of a transfer belt with respect to a photosensitive drum and a residual toner density.

FIG. 4 is a schematic configuration diagram showing another embodiment of the image forming apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram illustrating an example of a conventional image forming apparatus.

[Explanation of symbols]

1Y, 1M, 1C, 1Bk Photosensitive drum (image carrier) 4Y, 4M, 4C, 4Bk Transfer roller (transfer means) 14 Transfer belt (transfer material carrier) 25 Intermediate transfer member

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA17 DA20 DC04 DC14 DD02 EA03 EA09 ED02 ED16 ED24 ED27 2H030 AB02 AD03 AD05 AD16 BB02 BB42 BB46 BB54 BB71 2H032 AA05 BA07 BA18 BA23 BA27 BA30 CA02

Claims (9)

[Claims] A plurality of image carriers on which a developer image is formed; a transfer material carrier for transporting a transfer material to the plurality of image carriers; and a transfer material carrying the developer image on the image carrier. And a plurality of transfer means for transferring to a transfer material carried on a carrier, wherein the developer on the transfer material carrier is reversely transferred to at least one of the plurality of image carriers. A first cleaning mode in which the surface moving speed of the transfer material carrier and the surface moving speed of the image carrier are substantially constant; and the surface moving speed of the transfer material carrier. And a second cleaning mode in which the surface moving speed of the image carrier is different, wherein a predetermined condition is satisfied when the developer on the transfer material carrier is reversely transferred to the image carrier for cleaning. The first cleaning mode or Image forming apparatus characterized by selecting and executing a serial second cleaning mode. 2. The image according to claim 1, wherein in the second cleaning mode, a speed difference between a surface movement speed of the transfer material carrier and a surface movement speed of the image carrier exceeds 3%. Forming equipment. 3. The image forming apparatus according to claim 1, wherein the predetermined condition is a predicted remaining amount of the developer on the transfer material carrier. 4. The image forming apparatus according to claim 1, wherein the second cleaning mode is selected when a transfer material conveyance error occurs. 5. A method according to claim 1, wherein a plurality of image carriers on which a developer image is formed, an intermediate transfer body onto which the developer images on the plurality of image carriers are transferred, and a developer image on the image carrier are formed. And a plurality of transfer means for transferring to the intermediate transfer member, wherein the developer on the intermediate transfer member is reverse-transferred to at least one of the plurality of image carriers and cleaned. A first cleaning mode in which the surface transfer speed of the intermediate transfer member and the surface movement speed of the image carrier are substantially constant, and the surface movement speed of the intermediate transfer member and the surface movement speed of the image carrier are A second cleaning mode different from the first cleaning mode or the second cleaning mode depending on predetermined conditions when the developer on the intermediate transfer member is reversely transferred to the image carrier for cleaning. Cleaning mode Image forming apparatus characterized by selecting and executing. 6. The image forming apparatus according to claim 5, wherein a speed difference between a surface moving speed of the intermediate transfer member and a surface moving speed of the image carrier exceeds 3%. 7. The image forming apparatus according to claim 5, wherein the predetermined condition is a predicted remaining amount of the developer on the intermediate transfer body. 8. The image forming apparatus according to claim 5, wherein a developer image on the intermediate transfer member transferred from the image carrier is transferred to a transfer material. 9. The image forming apparatus according to claim 8, wherein the second cleaning mode is selected when a transfer material conveyance error occurs.