JP2002221862A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily clean an intermediate transfer body and a recording material carrier by introducing an electrostatic system and also suppressing damage due to a discharge. SOLUTION: Conductive recovering rollers 21 and 31 as a cleaning means are arranged on the downstream side of a secondary transfer part with reference to the intermediate transfer belt 5 of the image forming device, a bias having a negative polarity is applied on one recovering roller 21 by a power source 24, and a bias having a positive polarity is applied on the other recovering roller 31 by a power source 34, and the remaining toner having the positive polarity and the remaining toner having the negative polarity on the intermediate transfer belt 5 are separately and electrostatically attracted by the recovering rollers 21 and 31. By applying such the bias that does not cause the discharge, the intermediate transfer belt 5 is satisfactorily cleaned without causing the damage due to the discharge, and the remaining toner is removed.

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 using an electrophotographic method or the like, and more particularly to cleaning of an intermediate transfer member and a recording material carrier of the image forming apparatus.

[0002]

2. Description of the Related Art In a color image forming apparatus such as an electrophotographic copying machine or a laser beam printer, each of the image forming units of yellow (Y), magenta (M), and cyan (C) is advantageous for speeding up. In some cases, a black (K) image forming unit is further arranged in a straight line, and an image is formed almost simultaneously for each color.

On the other hand, in response to recent demands for toner improvement and space saving of the apparatus, waste toner which is not transferred to a recording material and remains on a photosensitive drum is sent to a developing device again for reuse. A method called toner reuse, which does not require a container, is being adopted. In particular, when the toner reuse method is applied to the in-line method, there is no need for a waste toner container prepared for each color, so that the advantage is great.

[0004] As a method for realizing toner reuse,
A method in which the transfer residual toner on the photosensitive drum is collected by a blade or the like and transported to a developing device, or the transfer residual toner is charged to a predetermined charge amount, sent to a developing unit and used again for development, or There is a method of collection.

In an in-line type image forming apparatus using a belt as an intermediate transfer body, toner images of each color formed by each image forming unit are superimposed on the intermediate transfer belt and primary-transferred, and then each color on the intermediate transfer belt is transferred. Is collectively secondary-transferred onto a recording material to form a full-color image on the recording material. After the secondary transfer, the intermediate transfer belt is cleaned.

As a method of cleaning the intermediate transfer belt after the secondary transfer, there is a method of scraping off the transfer residual toner on the intermediate transfer belt with a blade or a brush.
The surface of the intermediate transfer belt continues to be rubbed, which has the disadvantage of shortening the life of the intermediate transfer belt.In addition, a small particle size toner or spherical toner for the purpose of improving the reproducibility of thin lines and the transfer efficiency etc. It is difficult to completely remove them.

Therefore, the secondary transfer residual toner is charged to a positive polarity (or may be a negative polarity) by a charging means, and is transferred to a collection roller to which a negative bias (a positive bias when the toner is positively charged) is applied. A method has been proposed in which toner is scraped from a collecting roller by a blade, a brush, or the like after being electrostatically attracted.

[0008]

However, in order to reliably electrostatically attract toner to the collection roller, it is necessary to increase the charging bias applied to the charging means. As a result, the intermediate transfer belt is damaged, causing problems such as a reduction in the belt resistance value and cracks on the belt surface.

[0009] The above problems also occur when a transport belt or a transfer drum is used as a recording material carrier for carrying a recording material and transporting the photosensitive material to the photosensitive drum, and also when cleaning the transport belt or the transfer drum. Occurs.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of cleaning an intermediate transfer member and a recording material supporting member by an electrostatic method in a favorable manner and by suppressing damage due to discharge.

[0011]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image carrier on which a toner image is formed, an intermediate transfer member on which the toner image on the image carrier is transferred, and the intermediate transfer member after the toner image on the intermediate transfer member is transferred to a recording material. An electrostatically cleaning device having a cleaning unit to which a voltage is applied, the cleaning device having two or more cleaning units, wherein a voltage applied to at least one of the cleaning units has a positive polarity; An image forming apparatus is characterized in that a voltage applied to another cleaning unit is negative.

According to the present invention, the voltage applied to the cleaning means is set to a value within a range in which a discharge phenomenon does not occur between the cleaning device and the intermediate transfer member. A peripheral speed difference is provided between the intermediate transfer member and the cleaning unit. The cleaning unit is a conductive roller that contacts the intermediate transfer member. A plurality of color toner images sequentially formed on the image bearing member are transferred onto the intermediate transfer member in a superimposed manner. A plurality of the image carriers are provided, and a plurality of color toner images on the plurality of image carriers are transferred onto the intermediate transfer member in a superimposed manner. The intermediate transfer member is formed in a belt shape. The intermediate transfer member is formed in a drum shape.

According to another aspect of the present invention, there is provided an image carrier on which a toner image is formed, a recording material carrier for carrying and transporting a recording material, and a recording material on which the toner image is transferred on the image carrier after being separated. An electrostatic cleaning means for electrostatically cleaning the recording material carrier, wherein the cleaning means to which a voltage is applied comprises two or more cleaning means, and at least one of the cleaning means An image forming apparatus is characterized in that the voltage applied is positive and the voltage applied to another cleaning means is negative.

According to the present invention, the voltage applied to the cleaning means is set to a value within a range in which a discharge phenomenon does not occur between the cleaning member and the recording material carrier. A peripheral speed difference is provided between the recording material carrier and the cleaning unit. The cleaning unit is a conductive roller that contacts the recording material carrier. A plurality of color toner images sequentially formed on the image carrier are transferred in a superimposed manner on a recording material on the recording material carrier. A plurality of the image carriers are provided, and a plurality of color toner images on the plurality of image carriers are transferred in a superimposed manner on a recording material on the recording material carrier. The recording material carrier is formed in a belt shape. The recording material carrier is formed in a drum shape.

[0015]

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 FIG. 1 is a schematic view showing an embodiment of the image forming apparatus of the present invention. The image forming apparatus has a plurality of image forming units M, C, Y, and K along an intermediate transfer belt 5, and each of the image forming units M, C, Y, and K has a photosensitive drum as an image carrier. (Drum-shaped electrophotographic photosensitive member) 1 m, 1
c, 1y and 1k are installed so as to be rotatable in the direction of the arrow.

The photosensitive drums 1m, 1c, 1y and 1k are spaced apart from the photosensitive drums by a predetermined distance, respectively.
m, 2c, 2y, 2k are arranged, and the chargers 2m, 2c,
Exposure devices 3m, 3c, 3y, and 3k are arranged above the photosensitive drum rotation direction downstream from 2y and 2k, and further downstream, a developing device 4m that contains magenta, cyan, yellow, and black developers, respectively. 4c, 4y, and 4k are arranged.

Each of the photosensitive drums 1m to 1k is provided with a charge generation layer, a charge transfer layer, a charge injection layer and the like on the outer peripheral surface of an aluminum cylinder. Drum charger 2m
Reference numerals 2k to 2k denote charging devices of an injection charging system using a magnetic brush as a contact charging member, disclosed in JP-A-6-3921.

The intermediate transfer belt 5 has three support rollers 5
a, 5b, and 5c, the intermediate transfer device 5A is configured to have a trajectory along the photosensitive drums 1m to 1k.
One of the support rollers 5a to 5c is a driving roller, and the other two are driven rollers. The rotation of the driving roller by a driving unit (not shown) rotates the intermediate transfer belt 5 in the direction of the arrow.

The intermediate transfer belt 5 has a thickness of 0.3 to 0.3 mm.
Acrylonitrile butadiene rubber (NBR) having a resistance adjusted to about 2 mm and a volume resistivity of about 10 ⁶ to 10 ¹² Ωcm,
Rubber belts such as styrene butadiene rubber, butadiene rubber, ethylene propylene rubber, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, acrylic rubber, fluorine rubber, urethane rubber, or PVd
A resin belt of F, PET, polycarbonate, polyethylene, silicone or the like is preferable. In this embodiment, carbon is dispersed in hydrin rubber to obtain a volume resistivity of 10 ⁷ Ωcm.
10 ¹³ Ωcm on the base layer surface with a thickness of 0.5 mm adjusted to
The intermediate transfer belt 5 was provided with a surface layer of a fluororesin having a resistance of 20 μm and a thickness of 20 μm.

Inside the intermediate transfer belt 5, transfer rollers 6m, 6c, 6y and 6k are arranged opposite to the photosensitive drums 1m, 1c, 1y and 1k.
A primary transfer section is formed between each of 1c, 1y, and 1k and the intermediate transfer belt 5. A transfer roller 7 is disposed outside the intermediate transfer belt 5 at a position facing the support roller 5b, and a secondary transfer unit is configured between the transfer roller 7 and the intermediate transfer belt 5.

According to the present invention, in the rotational direction of the intermediate transfer belt 5, a position between the downstream of the secondary transfer portion and the upstream of the primary transfer portion, specifically, a position following the upstream of the support roller 5c. , A cleaning device 20 and a downstream cleaning device 30 are provided.

The two cleaning devices 20 and 30 have the same configuration, and include conductive recovery rollers 21 and 31 as cleaning means. The cleaning devices 20 and 30 contact the collecting rollers 21 and 31, that is, the surface of the intermediate transfer belt 5, and
Collection rollers 21 and 31 for electrostatically attracting the upper secondary transfer residual toner, and collection rollers 21 and 31 for collecting the collected toner.
The cleaning device includes cleaning blades 22 and 32 made of urethane rubber scraped from above, waste toner containers 23 and 33 containing the scraped toner, and bias power supplies 24 and 34 for applying a cleaning bias to the collection rollers 21 and 31. The power supplies 24 and 34 have opposite polarities.

The collecting rollers 21 and 31 are preferably coated with a urethane resin, a fluorine resin, a nylon resin, a polyimide resin or the like to provide a surface layer for ensuring releasability from the toner. In this example, a 20-mm-diameter aluminum cylinder whose surface was coated with a fluororesin at 20 μm was used as the collection rollers 21 and 31.

An image forming operation of the image forming apparatus having the above-described configuration will be described with reference to the first color magenta image forming unit M as an example. The photosensitive drum 1m is rotated, and during the rotation process, the surface is uniformly charged by the charger 2m, and then exposed by the exposure device 3m to form an electrostatic latent image corresponding to the document on the surface of the photosensitive drum 1. . The developing device 4m employs a two-component developing method using a two-component developer in which a magnetic carrier and a toner are mixed. The developer is charged to a negative polarity and the developer is charged to a magnetic pole having a predetermined magnetic force. SU with built-in magnet
It is carried on a developing sleeve made of S and transported to a developing section facing the photosensitive drum 1m to be used for developing an electrostatic latent image on the photosensitive drum 1m.

The charge amount of the toner (magenta) of the developing device 4m is about -30 μC / g. Other developing units 4c, 4
Similarly, the charge amounts of cyan, yellow and black toners of y and 4k are about -30 [mu] C / g. During development,
At a predetermined timing, a developing bias in which a DC voltage and an AC voltage are superimposed is applied to the developing sleeve from a developing power source (not shown), whereby toner flies from the developing sleeve onto the photosensitive drum 1m and adheres to the latent image, and Is developed and visualized as a yellow toner image.

The yellow toner image thus formed on the photosensitive drum 1m is transferred to the intermediate transfer belt 5 by a positive primary transfer bias having a polarity opposite to that of the toner applied to the primary transfer roller 6m from a primary transfer power source (not shown). Is primarily transferred to the surface of On the other hand, the transfer residual toner remaining on the photosensitive drum 1m after the primary transfer is recharged by applying a charge by a drum charger 2m which is a magnetic brush charger in accordance with a method described in JP-A-9-96997. It is collected at the developing unit with the photosensitive drum 1 at 4 m and reused.

An image forming process similar to the above is performed for the second color,
The image forming units C, Y, and K of the third color and the fourth color of cyan, yellow, and black are repeatedly used to form the intermediate transfer belt 5.
The toner images of four colors of magenta, cyan, yellow, and black are superimposed and transferred thereon. 4 on the intermediate transfer belt 5
The color toner images are collectively transferred onto a recording material (not shown) sent to the secondary transfer unit by a secondary transfer bias having a positive polarity opposite to that of the toner applied to the secondary transfer roller 7 from a secondary transfer power supply (not shown). Then, the recording material is sent to the fixing device 9 where the toner image of four colors is melted and fixed by applying heat and pressure, and a full-color fixed image of four colors is obtained on the recording material.

After the completion of the secondary transfer, the secondary transfer residual toner on the intermediate transfer belt 5 is removed by cleaning.
A major feature of the present invention is that cleaning is performed by the two cleaning devices 20 and 30. Hereinafter, the cleaning according to the present invention will be described in detail.

Although the toner image on the intermediate transfer belt 5 is negatively charged before the secondary transfer, the secondary transfer receives a positive charge due to the transfer bias after the secondary transfer, so that the secondary transfer remaining on the intermediate transfer belt 5 is performed. The remaining toner is in a state where negatively charged toner and positively charged toner are mixed. Therefore, two cleaning devices 20 and 30 are used, and for example, a plus bias is applied as a cleaning bias to a collection roller (first collection roller) 21 of the cleaning device 20, and a collection roller (first collection roller) of the other cleaning device 30 is used. A negative bias is applied to the (second collection roller) 31.

Then, the negatively charged residual toner on the intermediate transfer belt 5 is electrostatically attached to the collection roller 21 to which the plus bias is applied, and the intermediate transfer belt is applied to the collection roller 31 to which the minus bias is applied. Since the positively charged residual toner on the transfer belt 5 adheres electrostatically, both the positive and negative residual toner on the intermediate transfer belt 5 can be removed. Also, the bias applied at this time may be used at a level at which no discharge occurs.
As a result, damage to the intermediate transfer belt 5 due to discharge can be reduced.

In this embodiment, the collecting rollers 21 and 31
The relationship between the bias applied to the intermediate transfer belt 5 and the cleaning property and the deterioration property of the intermediate transfer belt 5 was examined. Test environment temperature 23
° C and a humidity of 60%. A negative bias was applied to the first recovery roller 21, and a positive bias was applied to the second recovery roller 31. Table 1 shows the results. In Table 1, the symbol before "/" indicates the belt cleaning property, and the symbol after "/" indicates the belt deterioration property. In each case, ○ indicates no problem and X indicates a problem.

[0033]

[Table 1]

As shown in Table 1, the applied bias is 0
In the case of V, the residual toner is not electrostatically attracted to the collecting rollers 21 and 31, so that the cleaning property of the intermediate transfer belt is poor. When the applied bias was 900 V or more in absolute value, discharge occurred between the collection rollers 21 and 31 and the intermediate transfer belt 5, and the resistance of the intermediate transfer belt decreased. Further, the bias applied to the second collection roller 31 is set to +900 V.
If it is larger than this, the cleaning property is poor. This is because the intermediate transfer belt 5 of the second collection roller 31
This is because discharge occurs in the nip portion on the upstream side of the contact portion, and the minus toner, which should originally adhere to the collection roller 31, is positively charged, so that the toner does not adhere to the collection roller 31. I think that the.

As described above, according to this embodiment, the two cleaning means of the collecting rollers 21 and 31 are used, and biases having different polarities are applied to the two cleaning means to remove the residual toner on the intermediate transfer belt 5. Since the cleaning is performed electrically, unlike the case of cleaning using mechanical means such as a blade or a brush, even when a small particle size toner or a spherical toner is used, the residual toner on the intermediate transfer belt 5 can be satisfactorily removed. Can be removed. In addition, since a bias is applied at a level at which no discharge occurs between the belt and the intermediate transfer belt 5,
Damage to the intermediate transfer belt can be reduced. Further, the sliding of the intermediate transfer belt is prolonged because the friction caused by the mechanical means is reduced.

In the above description, a minus bias is applied to the collecting roller 21 as the first cleaning means, and a plus bias is applied to the collecting roller 31 as the second cleaning means. In addition, the intermediate transfer belt can be satisfactorily cleaned.

Further, there may be three or more collection rollers,
A negative bias may be applied to at least one of the recovery rollers, and a positive bias may be applied to the other recovery roller, and a negative or positive appropriate bias may be applied to the remaining recovery rollers. Further, the cleaning means may be not only a conductive roller such as a collection roller but also a conductive brush roller.

Although the cleaning of the intermediate transfer belt of the image forming apparatus has been described above, the present invention can also be applied to an image forming apparatus using an intermediate transfer drum as an intermediate transfer member. The same effect can be obtained by doing the same.

Embodiment 2 The feature of this embodiment is that when the intermediate transfer belt 5 is cleaned by the collecting rollers 21 and 31 of the cleaning devices 20 and 31, the peripheral speed of the collecting rollers 21 and 31 and the peripheral speed of the intermediate transfer belt 5 are changed. In that a difference is provided between them.

Table 2 shows the result of examining the relationship between the peripheral speed difference and the average amount of the secondary transfer residual toner that can ensure the cleaning performance. In Table 2, the plus sign of the numerical value of the peripheral speed difference indicates a case where the peripheral speed of the collection roller is higher than the peripheral speed of the intermediate transfer belt, and the minus sign indicates a case where the peripheral speed is slower.

[0041]

[Table 2]

As shown in Table 2, when the peripheral speed difference is provided between the first and second collection rollers 21 and 31 and the intermediate transfer belt 5, more secondary transfer residual toner can be obtained. On the other hand, it can be seen that the cleaning property is ensured. Normal,
The secondary transfer residual toner amount is 0.4 mg / cm ² or less, so there is no need to provide a peripheral speed difference. However, if a recording material jam occurs before the secondary transfer, the intermediate transfer belt A situation occurs in which the amount of toner remaining on the top is as ^{high as} about 1.5 mg / cm ² . Therefore, if cleaning is performed without providing a peripheral speed difference, it is necessary to rotate the intermediate transfer belt three times or more and perform cleaning three times or more, with the toner amount of one cleaning being about 0.5 mg / cm ² . However, if the peripheral speed difference is provided, two cleanings are sufficient, and there is an advantage that the restart of the image forming apparatus after the jam is quick.

In a low-temperature and low-humidity environment, the resistance value of the intermediate transfer belt 5 and the charge amount of the toner are increased. Although it is necessary to increase the bias, the secondary transfer bias cannot be increased because an image defect due to abnormal discharge is likely to occur. Therefore, the amount of the secondary transfer residual toner tends to increase in a low-temperature and low-humidity environment. Therefore, providing a peripheral speed difference is useful when such environmental fluctuations occur.

FIG. 2 shows an image forming apparatus according to the present embodiment in which a temperature and humidity sensor 10 is added to the apparatus shown in FIG. 2, the same reference numerals as those shown in FIG. 1 indicate the same members.

In this embodiment, as shown in FIG. 2, a temperature / humidity sensor 10 is provided at an appropriate place in the image forming apparatus.
When cleaning the intermediate transfer belt 5 by applying biases having different polarities to the collection rollers 21 and 31 of the cleaning devices 20 and 30 at a level at which no discharge occurs between the recovery rollers 21 and 31 and the intermediate transfer belt 5, the image is detected by the sensor 10. The temperature and humidity of the atmosphere of the environment where the forming apparatus is placed are detected, and the peripheral speed of the collection rollers 21 and 31 is changed by the CPU 11 in the apparatus main body based on the detection result. Control the difference.

According to this embodiment, the peripheral speed difference is provided between the two recovery rollers and the intermediate transfer belt even if the secondary transfer residual toner amount increases due to environmental fluctuations. The toner remaining after transfer can be removed by satisfactorily cleaning the intermediate transfer belt while minimizing damage.

Embodiment 3 FIG. 3 is a schematic view showing still another embodiment of the image forming apparatus of the present invention. In this embodiment, the image forming apparatus is provided with control means for detecting the primary transfer current and controlling the primary transfer bias, and the temperature and humidity of the environment atmosphere are measured using this control means.

As shown in FIG. 3, the transfer bias control means is connected to a primary transfer bias power supply 12 (only the primary transfer roller 6m is shown in the figure, but is connected to each of the primary transfer rollers 6m to 6k so as to be switchable. ) Is connected to the primary transfer current detection circuit 13.
A primary transfer bias is applied from a power supply 12 to one of the primary transfer rollers 6m to 6k, for example, the transfer roller 6m, with the photosensitive drum 1m as an opposite pole by constant voltage control, and a primary transfer current flowing at that time is detected by a current detection circuit 13. The detection signal is sent to the CPU 11 of the apparatus main body, and the CPU 11 controls the power supply 12 at a constant voltage so that the primary transfer bias becomes appropriate.

If such a transfer bias control means is provided, the resistance value of the intermediate transfer belt 5 can be measured indirectly from the applied voltage and the flowing current without using a temperature / humidity sensor. The temperature and humidity in the atmosphere can be estimated and detected. Therefore, the peripheral speed difference between the collecting rollers 21 and 31 and the intermediate transfer belt 5 may be controlled based on the detection result. The measurement of the resistance value of the intermediate transfer belt 5 can be performed at any time other than during the image forming sequence.

In this embodiment, as described above, the change in the environment is detected by using the transfer bias control means. Therefore, even if a temperature and humidity sensor is not installed, the amount of the secondary transfer residual toner due to the change in the environment can be reduced. By controlling the peripheral speed difference between the two recovery rollers and the intermediate transfer belt, the intermediate transfer belt can be cleaned satisfactorily to remove transfer residual toner while minimizing damage to the intermediate transfer belt. can do.

In the above, the resistance value of the intermediate transfer belt 5 was measured by applying a primary transfer bias to the primary transfer roller with the photosensitive drum as the opposite pole, but the primary transfer bias was applied with the secondary transfer roller 7 as the opposite pole. Then, the resistance of the intermediate transfer belt may be measured. Further, since it is sufficient that the resistance value of the intermediate transfer belt 5 can be measured, the primary transfer bias may be applied by constant current control, and the voltage at that time may be monitored to measure the resistance value.

Embodiment 4 Still another embodiment of the present invention will be described with reference to FIG. The image forming apparatus according to the present embodiment has a transport belt 14 as a recording material carrier that carries a recording material (not shown) and transports the recording material to each of the image forming units M to K. Shows a case where the present invention is applied to cleaning of a sheet. 4, the same reference numerals as those shown in FIG. 1 denote the same members.

The transport belt 14 includes drive rollers 14a, 2
The transfer device 14A is configured to be suspended on a total of four support rollers, namely, the driven rollers 14b and 14c and the suction opposing roller 14d as a driven roller, and has a track along the photosensitive drums 1m to 1k. The transport belt 14 is rotationally driven in the direction of the arrow by the rotation of the driving roller 14a by a driving unit (not shown).

The conveyor belt 14 is made of a resin material such as urethane resin, fluorine resin, nylon resin, polyimide resin, rubber material such as silicone rubber or hydrin rubber, or carbon or What carried out resistance adjustment by dispersing conductive powder can be used. Of course, a plurality of structures such as two layers may be used.

The resistance of the transport belt 14 is 1 in volume resistivity.
0 ⁷ 10 ¹¹ about Ωcm is preferable. Although depending on the material, the tension of the conveyor belt 14 is preferably set so that the elongation percentage is within 1% so that the belt is not broken or permanent distortion occurs. In this example, the transport belt 1
4 is set so that a tension of about 150 N is applied.

Inside the conveyor belt 14, the photosensitive drum 1
m, 1c, 1y, and 1k, the transfer roller 6
m, 6c, 6y and 6k are arranged, and the photosensitive drums 1m and 1m
Transfer portions are formed between c, 1y, and 1k and the conveyor belt 14, respectively. The transfer rollers 6m to 6k are formed by coating a core with an elastic material. In addition, on the outer side of the transport belt 14, upstream of the image forming unit M for the first color, the attraction roller 15b and the attraction roller 15 with the transport belt 14 interposed therebetween.
Is installed.

The recording material (not shown) supplied to the transport belt 14 is electrostatically attracted onto the transport belt 14 by an attraction roller 15 to which an attraction bias is applied, and the rotation of the transport belt 14 causes the image forming units M to K to rotate. It is sequentially conveyed to the transfer section. Then, the toner images of the respective colors formed on the photosensitive drums 1m to 1k are transferred at a predetermined timing onto the recording material by transfer rollers 6m to 6k to which a positive transfer bias is applied from a transfer power supply (not shown). .

The recording material on which the toner images of the four colors have been superimposedly transferred in this manner is separated from the conveying belt 14 at the downstream end in the conveying direction and sent to the fixing device 9, where the toner image is heated and pressed to thereby form the toner image. To form a full-color fixed image.

In the normal printing as described above, the toner image is not transferred onto the conveyor belt 14, but in the case of the in-line system such as the present image forming apparatus, the conveyor belt 1
4, the reference image of each color is directly transferred and formed, and the position of the reference image is detected by an optical sensor 16 provided on the downstream side of the image forming unit K of the final color, and the image writing position on the photosensitive drum Generally, by controlling (exposure start position) and the like, registration correction (color shift correction) of an image of each color is performed. Therefore, it is necessary to clean the toner of the reference image on the conveyor belt 14 after correcting the color misregistration.

Even during normal printing, the photosensitive drum 1 m
A small amount of toner is present in the non-image area of 1 k to 1 k, and in the non-image area of the conveyance belt 14 where there is no recording material, the photosensitive drums 1 m to 1 k are in contact with the conveyance belt 14. Accumulate little by little. For this reason, the transport belt 14 needs to be cleaned even during normal printing.

Therefore, in this embodiment as well, in the direction of rotation of the conveyor belt 14, an appropriate portion between the rear portion of the recording material and the recording material suction portion, for example, a portion near the support roller 14b between the support roller 14c and the support roller 14c. At the position, collecting rollers 21 and 31 are installed as cleaning means,
The cleaning belt 31 is electrostatically cleaned by applying cleaning biases having different polarities to each other and setting the bias to a level at which no discharge occurs between the cleaning belt 31 and the conveyance belt 14.

In the present embodiment, as described above, the residual toner can be removed by cleaning the transport belt satisfactorily without reducing the print throughput (productivity), while suppressing the damage to the transport belt.

In the above, there is no particular description about providing a peripheral speed difference between the collection rollers 21 and 31 and the transport belt 14, but as in the second embodiment, a peripheral speed difference is provided between them. In this case, the cleaning property of the transport belt is improved.

Although the case where a conveying belt is used as the recording material carrier has been described, the present invention is not limited to this, and the cleaning is similarly performed when a drum-shaped recording material carrier, that is, a transfer drum is used. By doing so, a similar effect can be obtained.

In each of the first to fourth embodiments, an image forming apparatus having a plurality of photosensitive drums as image carriers has been described as an example. However, the present invention has one photosensitive drum, and An image forming apparatus in which a plurality of color toner images are sequentially formed on the photosensitive drum, the plurality of color toner images on the photosensitive drum are transferred onto the intermediate transfer member in a superimposed manner, and then transferred to a recording material. The present invention can also be applied to an image forming apparatus in which the toner image is directly superimposed and transferred onto a recording material on a recording material carrier.

[0066]

As described above, according to the present invention,
In electrostatically cleaning the intermediate transfer body and the recording material carrier, a plurality of cleaning means are used, a positive cleaning bias is applied to at least one of the cleaning means, and a negative cleaning bias is applied to another cleaning means. The cleaning bias is applied to electrostatically clean the intermediate transfer member and the recording material carrier, so that residual toner can be removed and damage due to electric discharge can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a schematic view showing another embodiment of the image forming apparatus of the present invention.

FIG. 3 is a schematic view showing still another embodiment of the image forming apparatus of the present invention.

FIG. 4 is a schematic view showing still another embodiment of the image forming apparatus of the present invention.

[Explanation of symbols]

 1 m to 1 k Photosensitive drum 5 Intermediate transfer belt 6 m to 6 k Transfer roller 7 Transfer roller 14 Recording material transport belt 20, 30 Cleaning device 21, 31 Collection roller 24, 34 Bias power supply

Claims (16)

[Claims] 1. An image bearing member on which a toner image is formed, an intermediate transfer member on which the toner image on the image bearing member is transferred, and an image transfer member after the toner image on the intermediate transfer member is transferred onto a recording material. An image forming apparatus, comprising: a cleaning unit to electrostatically clean the intermediate transfer body, to which a voltage is applied, wherein the cleaning unit includes two or more cleaning units,
An image forming apparatus, wherein a voltage applied to at least one of the cleaning units has a positive polarity, and a voltage applied to the other cleaning unit has a negative polarity. 2. The image forming apparatus according to claim 1, wherein the voltage applied to the cleaning unit is set to a value within a range in which a discharge phenomenon does not occur between the cleaning unit and the intermediate transfer body. 3. The image forming apparatus according to claim 1, wherein a peripheral speed difference is provided between the intermediate transfer member and the cleaning unit. 4. The image forming apparatus according to claim 1, wherein the cleaning unit is a conductive roller that contacts the intermediate transfer member. 5. The image according to claim 1, wherein a plurality of color toner images sequentially formed on the image bearing member are transferred in an overlapping manner on the intermediate transfer member. Forming equipment. 6. The image forming apparatus according to claim 1, further comprising a plurality of image carriers, wherein a plurality of color toner images on the plurality of image carriers are transferred in an overlapping manner on the intermediate transfer member. An image forming apparatus according to any of the above items. 7. The image forming apparatus according to claim 1, wherein the intermediate transfer member is formed in a belt shape. 8. The image forming apparatus according to claim 1, wherein said intermediate transfer member is formed in a drum shape. 9. An image carrier on which a toner image is formed, a recording material carrier for carrying and transporting a recording material, and the recording after separating the recording material on which the toner image on the image carrier has been transferred. An image forming apparatus comprising: a cleaning unit to electrostatically clean a material carrier; and a cleaning unit to which a voltage is applied, wherein the cleaning unit includes two or more cleaning units,
An image forming apparatus, wherein at least one of the cleaning units has a positive voltage and another of the cleaning units has a negative voltage. 10. The image forming apparatus according to claim 9, wherein the voltage applied to the cleaning unit is set to a value within a range in which a discharge phenomenon does not occur between the cleaning unit and the recording material carrier. 11. A peripheral speed difference is provided between said recording material carrier and said cleaning means.
Or 10 image forming apparatuses. 12. The image forming apparatus according to claim 9, wherein the cleaning unit is a conductive roller that contacts the recording material carrier. 13. The image forming apparatus according to claim 9, wherein a plurality of color toner images sequentially formed on the image carrier are transferred onto a recording material on the recording material carrier. An image forming apparatus according to claim 1. 14. The image forming apparatus according to claim 1, wherein a plurality of image carriers are provided, and a plurality of color toner images on the plurality of image carriers are transferred to a recording material on the recording material carrier in a superimposed manner. 9 ~
13. The image forming apparatus according to any one of the above items 12. 15. The image forming apparatus according to claim 9, wherein the recording material carrier is formed in a belt shape. 16. The image forming apparatus according to claim 9, wherein said recording material carrier is formed in a drum shape.