JP3184012B2 - Image forming device - Google Patents

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 such as a copying machine, a printer, and a facsimile, and more particularly to an image forming apparatus suitable for forming a color image by transferring a plurality of developer images in multiple colors.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a full-color image on a transfer material such as paper, a toner image is formed on a photoreceptor which is an image carrier by electrophotography, and the toner image is formed on a transfer material. A method of sequentially performing transfer in accordance with a predetermined color order has been put to practical use.

An image forming apparatus using this method is disclosed, for example, in JP-B-63-34467. In this apparatus, the transfer material is held on a transfer drum made of an insulating sheet capable of holding electric charge such as plastic, and is conveyed to a transfer section on the photoreceptor. High voltage is applied by the charger. By this voltage application, the back side of the transfer drum is charged to form an electrostatic field, and the toner image on the photoconductor charged to a predetermined polarity is transferred to the transfer material. The image formation is completed by rotating the transfer drum a plurality of times in accordance with the predetermined color.

An image forming apparatus using the above method is disclosed in Japanese Patent Application Laid-Open No. 55-74037. This apparatus includes a plurality of photoconductors, and holds a transfer material on a transfer belt made of an insulating sheet capable of holding electric charge such as plastic, and sequentially conveys the transfer materials to transfer units on the plurality of photoconductors. During this transfer, the back surface of the transfer belt at the transfer portion of each photoconductor is charged by applying a high voltage by, for example, a non-contact type corona charger to form an electrostatic field, and a plurality of photosensitive members charged to a predetermined polarity are formed. The toner image on the body is sequentially transferred to the transfer material by one transfer of the transfer material.

In the above-described image forming apparatus, a transfer material carrier such as a transfer drum or a transfer belt for holding a transfer material adheres to a toner of a non-image portion on a photoreceptor, that is, fog toner. The toner image on the photoreceptor is directly contacted without the intermediary of the transfer material due to the occurrence of the paper jam, and the toner adheres thereto, and further, the toner is stained by the adhesion of the floating toner in the apparatus.

As described above, when the transfer material carrier is soiled by the toner, the toner adheres to the back surface of the transfer material and stains the back surface of the transfer material, or causes transfer failure.
For this reason, a cleaning device such as a blade cleaning device or a fur brush cleaning device is used to remove and collect the toner adhering to the transfer material carrier to perform cleaning.

In recent years, a printer used as an output device of a computer or the like has been required to be maintenance-free. Therefore, a photosensitive member which is an image forming process, and a charger, a developing device, The cleaner and the like are made into an integrated unit, and the user replaces the unit when a certain life period comes.

However, in the color image forming apparatus having the transfer material carrier, a cleaning device for the transfer material carrier is specially required, so that the user replaces the toner collection container of the cleaning device, and In addition, it is necessary to replace consumable parts of the cleaning device.

The replacement of the toner collecting container and the replacement of the consumable parts of the cleaning device may cause toner scattering inside and outside the device, which is a troublesome operation for the user.

[0010]

As described above, conventionally, in an image forming apparatus having a transfer material carrier, a cleaning device for the transfer material carrier is specially required, and the toner of the cleaning device is required. There is a drawback that it is necessary to exchange the collection container and further exchange the consumable parts of the cleaning device, which takes time.

Accordingly, the present invention provides a maintenance-free image forming apparatus capable of cleaning the transfer material conveying means without specially requiring a cleaning device for the transfer material conveying means. With the goal.

[0012]

Since SUMMARY OF THE INVENTION The present invention is to solve the above problems, a plurality of image forming means for forming a developer image at predetermined intervals arranged to image bearing member, the image formation of the plurality
Means for forming the developer image on the plurality of image carriers
On the other hand , a transfer material conveying means for sequentially carrying and transferring the transfer material on the supporting surface, a plurality of power supply members arranged opposite to the image carrier via the transfer material conveyance means, and a bias voltage applied to these power supply members. by applying to a bias voltage application means for the developer image is transferred onto the transfer material on said image bearing member, after the image transfer to the transfer material, removing recovered developer remaining on the image bearing member A plurality of removing means, and a developer charging means for charging the developer adhered to the carrying surface of the transfer material conveying means to the same polarity as the bias voltage,
An image of the developer on the transfer material transporting unit charged by the developer charging unit is located at the most downstream side in the transport direction of the transfer material.
When the transfer material is not interposed between the carrier and the power supply member facing the image carrier, the transfer to the image carrier is performed by applying a bias voltage to the power supply member by the bias voltage applying unit.

[0013]

[0014]

When a bias voltage is applied by a bias voltage applying means to a power supply member which opposes the image carrier via the transfer material conveying means, a transfer electric field is formed, and the developer image formed on the image carrier is transferred to the transfer material. It is transferred to the transfer material conveyed by the means.

The developer on the image carrier may directly adhere to the carrying surface of the transfer material conveying means, or a floating developer may adhere. The developer to be attached includes both a positively charged one and a negatively charged one, but the developer is charged to the same polarity as the transfer bias voltage by the developer charging means. The charged developer is formed by applying a bias voltage to the power supply member by the bias voltage applying unit when the transfer material is not interposed between the image bearing member and the transfer material conveying unit during non-transfer. It is transferred to the image carrier by the electric field. The developer transferred to the image carrier is removed and collected by a removing unit in the image forming unit. By this collection, the transfer material conveying means can be cleaned without requiring a special cleaning device for the transfer material conveying means.

Further, the developer adhering to the transfer material conveying means is transferred to a plurality of image forming means arranged at predetermined intervals.
By transferring to the image carrier of the image forming means located on the most downstream side in the transfer material transport direction, the developer accommodating capacity of the removing means of the image forming means other than the image forming means located on the most downstream side is reduced. Be able to do it .

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in FIGS. FIG. 1 is a schematic configuration diagram showing an image forming apparatus of the present invention. The image forming apparatus includes a plurality of process units 1a to 1 as image forming means corresponding to each color.
1d, and the toner images (developer images) formed on the respective photosensitive drums 10a to 10d in the process units 1a to 1d are sequentially multiplexed on a sheet P as a transfer material by one paper pass. Transcribe. Therefore, a color image can be formed at a high speed even at a low process speed.

In FIG. 1, a transfer belt 17 as a transfer material conveying means is stretched between a pair of holding rollers 20 and 21 and is driven to rotate in a direction indicated by an arrow in the figure. The flat part on the upper side of the transfer belt 17 is
The process units 1a, 1b, 1c, and 1d are sequentially arranged at predetermined intervals in the traveling direction of the transfer belt 17. The process unit 1a forms a yellow toner image, the process unit 1b forms a magenta toner, the process unit 1c forms a cyan image, and the process unit 1d forms a black toner image.

The above four process units 1a, 1
b, 1c and 1d are composed of common parts other than the cleaner 14d (removal means) of the last process unit 1d. That is, the photosensitive drums 10a, 10b, 10c having a photosensitive layer on the surface and rotating in the direction of the arrow shown in the drawing.
10d, and these photosensitive drums 10a, 10b,
A laser for irradiating the laser beams 12a, 12b, 12c, and 12d to the charging rollers 11a, 11b, 11c, and 11d, which are ozone-less chargers, and the photosensitive drums 10a, 10b, 10c, and 10d, around the portions 10c and 10d. Optical systems 16a, 16b, 16c, 16d, non-magnetic one-component developing units 13a, 13b, 13c, 13d, cleaners (removing means) 14a, 14b, 14c using blades,
14d and static elimination lamps 15a, 15b, 15c, 1
5d are arranged. The developing units 13a, 13b, 1
3c and 13d contain black, yellow, magenta and cyan non-magnetic toners (developers), respectively. The cleaner 14d of the last process unit 1d is the cleaner 14a of the other process units 1a, 1b, 1c,
The storage capacity of the collected toner is larger than 14b and 14c, and is about four times as large.

In addition, the above four process units 1
a, 1b, 1c, and 1d are photosensitive drums 10a to 10d, respectively.
10d, charging rollers 11a to 11d, developing units 13a to 1
3d, cleaners 14a to 14d, static elimination lamps 15a to 1
5d are integrated, and when each reaches a predetermined number of prints, the unit is replaced.

On the other hand, inside the transfer belt 17, four power supply rollers (power supply members) 19 constituting transfer means corresponding to the respective process units 1a, 1b, 1c and 1d.
a, 19b, 19c, and 19d are provided. These four power supply rollers 19a, 19b, 19c, and 19d abut against the back side of the transfer belt 17 to move the front side of the transfer belt 17 to the four photosensitive drums 10a, 10b, 10c, and 10d.
d, and is driven to rotate as the transfer belt 17 travels.

Each of the power supply rollers 19a, 19b, 19
Reference numerals c and 19d denote transfer bias voltages applied to the transfer belt 17 in a transfer portion which is a contact portion. As shown in FIG. 2, the power supply rollers 19a, 19b, 19c, and 19d each include a metal core 32, and an elastic layer 33d made of conductive urethane and provided on the outer periphery of the metal core 32.
The core metal 32 is connected to a bias power supply 34 as a bias voltage applying means.

In the vicinity of the holding roller 20 on the upstream side of the transfer belt 17, a toner charging brush 35 is provided as developer charging means for charging the toner adhered on the transfer belt 17 to a predetermined polarity. Have been. The toner charging brush 35 is in contact with the surface of the transfer belt 17.

Further, on the upstream side of the transfer belt 17, a paper feed cassette 24 for storing paper P as a transfer material is provided.
The paper feed cassette 24 is provided with a rotatable pickup roller 23 for picking up the paper P one by one. A registration roller pair 22 composed of an upper roller 22a and a lower roller 22b is rotatably provided on the paper loading side of the transfer belt 17 in the transport direction of the paper P taken out by the pickup roller 23.
The registration roller pair 22 feeds the conveyed sheet P to the transfer belt 17 at a timing such that the leading ends of the toner images formed on the photosensitive drums 10a, 10b, 10c, and 10d come to the leading ends of the sheet P.

A heat roller type fixing device 25 is provided on the downstream side of the transfer belt 17, and the toner image is fixed by heating and pressing the sheet P by the fixing device 25. After the fixing, the sheet P is transferred to the discharge tray 26.
Is discharged to

The transfer belt 17 is made of polycarbonate in which carbon having a thickness of 140 μm is uniformly dispersed, and its electric resistance per cm ^{2 in} the thickness direction is 10 ^9.
Ω.

In this apparatus for forming a transfer electric field by applying a bias voltage to the transfer belt 17, the electric resistance of the transfer belt 17 has an important influence on transfer characteristics. When the electric resistance per 1 cm ^{2 in} the thickness direction of the transfer belt 17 becomes 10 ⁶ Ω or less, an electric charge is applied from the transfer belt 17 to the paper P, and this electric charge is applied to the toner image on the photoconductor, and Since the charging polarity of the image becomes the opposite polarity, the transfer efficiency is lowered, which is not preferable.

When the electric resistance per 1 cm ^{2 in} the thickness direction of the transfer belt 17 becomes 10 ¹² Ω or more, a high transfer bias voltage is required to obtain a sufficient transfer electric field, and after the transfer, the photosensitive drums 10a to 10a to When the paper P is peeled off from 10d, a peeling discharge is generated, and the charging polarity of the toner image becomes the reverse polarity, thereby lowering the transfer efficiency, which is not preferable.

On the other hand, the present apparatus has a black printing mode for forming an image of only black and a color printing mode for forming a color image, and performs the last printing in the black printing mode or during warm-up or after printing. As shown in FIG. 7, the photosensitive drums 10a, 10b, and 10c other than the photosensitive drum 10d of the black process unit 1d and the transfer belt 17 are kept out of contact with each other.

In FIG. 7, the transfer belt 17 is in the non-contact state.
The transfer belt 17 is inclined by moving the holding roller 20 on the upstream side downward. In the color printing mode, the transfer belt 17 is moved so as to be in a horizontal state.
All four photoconductor drums 10a, 10b, 10c, and 10d are in contact with the transfer belt 17.

The transfer belt 17 is held by a belt unit frame 61 as shown in FIG. The lower surface of the belt unit frame 61 has two
Two feed-side compression springs 62, 62 and discharge-side compression springs 63, 63 are provided and are constantly urged upward. With this bias, the intermediate portion of the transfer belt 17 is biased to a position where it comes into contact with the image forming units 100a, 100b, 100c, and 100d that form an image of a color corresponding to the color image.

An arm 64 composed of a cut-and-raised piece is provided on the lower surface of one end of the belt unit frame 61, and a solenoid 65 is connected to the arm 64. .

When the solenoid 65 is excited, the belt unit frame 61 is inclined downward against the urging force of the paper-side compression springs 62, 62, and the transfer belt 17 is moved to a photosensitive drum other than the photosensitive drum 10d. 10a, 10
b, 10c.

Also, by demagnetizing the solenoid 65,
The belt unit frame 61 is raised so as to be in a horizontal state by the urging force of the paper supply side compression springs 62, 62, and the transfer belt 17 is moved to the four photosensitive drums 10a.
10b, 10c, and 10d are all brought into contact.

Next, an image forming process in the black printing mode will be described by taking the last process unit as an example. In the black printing mode, the photosensitive drums 10a, 10b, and 10c other than the photosensitive drum 10d of the last black process unit 1d are not in contact with the transfer belt 17.

As shown in FIG. 2, the surface of the photosensitive drum 10d having the organic photoconductive layer 31d on the base 30d is uniformly charged to, for example, -500V by the charging roller 11d. The charged charges on the photosensitive drum 10d are partially erased by the laser beam 12d which is image-modulated and emitted from the laser optical system 16d, and an electrostatic latent image is formed. This electrostatic latent image is inverted by the black toner charged to the negative polarity by the developing device 13d, that is, the black toner adheres to the portion where the charged charge is erased by irradiating the laser beam 12d, and the black toner adheres to the photosensitive drum 10d. A toner image T is formed on the image. The toner image T formed on the photoreceptor drum 10d comes into contact with the transfer unit at the same speed as the paper P carried on the transfer belt 17 at the transfer unit. Also,
At this time, a bias voltage is applied to the power supply roller 19d from the bias power supply 34, and a bias voltage having a polarity opposite to that of the toner image T, for example, a voltage of + 1100V is applied to the transfer belt 10d from the power supply roller 19d.
Is transferred to The paper P on which the toner image T is formed is sent from the transfer belt 17 to the fixing device 25 and is heated and pressurized. As a result, the toner image T is fixed on the paper P. On the other hand, after the transfer, the toner remaining on the photoconductor drum 10d is removed and collected by the cleaner 14d, and the photoconductor drum 10d is discharged by the discharge lamp 15d and used for the next image formation.

On the other hand, in the color printing mode, all four photosensitive drums 10a, 10b, 10c, and 10d are in contact with the transfer belt 17, and the photosensitive drum 1
The surfaces of 0a to 10d are uniformly charged to, for example, -500V by the charging rollers 11a to 11d. Then, the charged charges on the photosensitive drums 10a to 10d are partially erased by the laser beams 12a to 12d which are image-modulated and irradiated from the laser optical systems 16a to 16d, and the respective electrostatic latent images are formed. These electrostatic latent images are stored in the developing device 13
a to 13d, the reversal phenomenon is caused by the toner of each color charged to the negative polarity, that is, the laser beams 12a to 1d.
The toner of each color adheres to the portion where the charge is erased by the irradiation of 2d, and the toner image T of each color is formed on the photosensitive drums 10a to 10d. These toner images are transferred onto a sheet P conveyed while being carried on a transfer belt 17 by the photosensitive drum 1.
Multiple transfer is sequentially performed in the order of 0a, 10b, 10c, and 10d. The paper P thus multiply transferred is sent from the transfer belt 17 to the fixing device 25 and heated and pressurized. As a result, the toner image T is fixed on the paper P. On the other hand, after the transfer, the toner remaining on the photosensitive drums 10a to 10d is removed and collected by the cleaners 14a to 14d, and the photosensitive drums 10a to 10d are discharged by the discharge lamps 15a to 15d and used for the next image formation. You.

Next, the cleaning process of the transfer belt 17 will be described. The cleaning of the transfer belt 17 is performed by the photosensitive drums 10a, 10b, and 1 other than the photosensitive drum 10d of the last black process unit 1d.
0c, when the transfer belt 17 is in a non-contact state, at the time of warming up of the apparatus, at the end of printing, and in the continuous black printing.
This is performed during non-printing when there is no paper P, such as when the paper P passes through the transfer unit.

As shown in FIG. 4, the toner T 'adhered to the transfer belt 17 has a positive polarity and a negative polarity mixedly. The toner T' is opposed to the holding roller 20 of the transfer belt 17 which is made of metal and is grounded. The transfer belt 17 is charged by the toner charging brush 35 with the same polarity as the transfer bias voltage, that is, in the present embodiment, to the plus polarity.

The toner charging brush 35 is a conductive fiber 36 fixed to a metal holder 37 and made of rayon fiber in which carbon is dispersed. A voltage of, for example, 400 V is applied to the metal holder 37 from a power supply 38. .

The toner T 'charged to the positive polarity by the toner charging brush 35 is carried to the transfer portion on the photosensitive drum 10d of the subsequent black process unit 1d as the transfer belt 17 moves. . As shown in FIG. 3, in the transfer portion, the photosensitive drum 10d is in a non-image portion state, and the front surface of the photosensitive drum 10d is substantially -500V.
Is charged. A voltage of +200 V having the same polarity as the transfer bias voltage is applied to the transfer belt 17 that does not carry the sheet P by the power supply roller 19d.

As a result, as shown in FIG. 6, an electric field for cleaning the transfer belt 17 is formed,
The upper toner T 'is transferred to the photosensitive drum 10d. Then, the transferred toner T 'is removed and collected by the cleaner 14d of the black process unit 1d.

The bias voltage at the time of cleaning is
Good cleaning can be performed by changing the bias voltage value so that the potential difference between the non-image portion potential of the photoconductor and the bias voltage is lower than that during transfer.

FIGS. 5 and 6 are diagrams schematically showing the potential relationship between the transfer and the cleaning in the reversal phenomenon process. In FIG. 5, the electric field is applied via the paper P at the time of the transfer. It is necessary to apply a relatively high bias voltage to obtain excellent transfer characteristics.

On the other hand, since there is no paper at the time of cleaning, air discharge easily occurs between the photosensitive drum 10d and the transfer belt 17 at the same bias voltage as at the time of transfer.
Therefore, it is better to change the bias voltage so that the potential difference between the non-image portion potential of the photoconductor and the bias voltage is lower than that at the time of transfer. Depending on the value of the electric resistance of the transfer belt 17, the bias voltage may be 0V.

FIGS. 8 and 9 are diagrams schematically showing the potential relationship between the time of transfer and the time of cleaning in the normal development process. As can be seen from FIG.
By charging the toner T 'adhered thereon with the same polarity as that of the transfer bias voltage, cleaning can be performed in the same manner as in the inversion process. As for the bias voltage at the time of cleaning, better cleaning can be performed by changing the bias voltage value so that the potential difference between the non-image portion potential of the photoconductor and the bias voltage becomes lower than at the time of transfer.

As the toner charging means for charging the toner T 'adhered to the transfer belt 17 with a predetermined polarity, the conductive brush 35 is used.
0, the charging blade 4 includes a holder 42 and a conductive blade 41 fixed to the holder 42.
0, or as shown in FIG.
Alternatively, a corona charger 50 including a corona wire 52 and a corona wire 52 may be used.

As the transfer belt 17 adjusted to an appropriate electric resistance value in the present embodiment, in addition to the above-described one in which carbon is dispersed in polycarbonate, polyethylene terephthalate, polyimide, polytetrafluoroethylene (Teflon), etc. The conductive sheet such as carbon may be dispersed in the high-resistance dielectric sheet described above.

Also, a polymer film whose electric resistance is adjusted by adjusting the composition without using conductive particles, a polymer film mixed with an ionic conductive substance, or a silicon film having a relatively low electric resistance. Rubber materials such as rubber and urethane rubber may be used.

Further, the present invention is not limited to the above-described embodiment, but can be variously modified. In the above embodiment,
The photosensitive drum 1 of the last black process unit 1d
0d, the photoconductive drums 10a, 10b, and 10c and the transfer belt 17 are maintained in a non-contact state.
However, the present invention is not limited to this, and the transfer belt 17 may be fixed and the process units 1a, 1b, and 1c other than the black process unit 1d may be separated from the transfer belt 17.

In the above-described embodiment, the plurality of photoreceptor drums 10a to 10d and the transfer belt 17 are arranged in parallel, but a plurality of developing units are disposed around the photoreceptor drums 10a to 10d. The present invention can be applied to a case where a transfer belt is provided, and may be applied to a monochrome image forming apparatus as a matter of course.

[0052]

As described above, according to the present invention,
The developer adhering to the carrying surface of the transfer material conveying means is charged to the same polarity as the bias voltage by the developer charging means. When the transfer material does not intervene between the image carrier and the power supply member, the bias is applied to the developer. By applying a bias voltage to the power supply member by the voltage applying means, the developer is transferred to the image carrier. Therefore, the developer transferred to the image carrier can be removed and removed by the removing means.

Therefore, a cleaning device for cleaning the developer adhering to the transfer surface of the transfer material conveying means is not required for exclusive use, and the device can be reduced in size and used. This eliminates the need for the user to replace the developer collection container or replace consumable parts as in the related art, and thus has the effect of reducing labor.

Further, the developer adhering to the transfer material conveying means is transferred to a plurality of image forming means arranged at predetermined intervals.
To transfer to the image carrier of the image forming unit located on the most downstream side in the transfer material transport direction, the developer accommodating capacity of the removing unit of the image forming unit other than the image forming unit located on the most downstream side is set.
Can be smaller. Therefore, the distance between each of the plurality of image forming means and each image carrier can be shortened, and the apparatus can be downsized.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram illustrating an image transfer state of the image forming apparatus of FIG. 1;

FIG. 3 is an explanatory diagram illustrating a cleaning state of a transfer belt of the image forming apparatus of FIG. 1;

4 is an explanatory diagram showing a state in which toner on a transfer belt of the image forming apparatus of FIG. 1 is charged.

FIG. 5 is a diagram schematically showing a potential relationship at the time of image transfer in a reversal development process of the image forming apparatus of FIG. 1;

FIG. 6 is a diagram schematically showing a potential relationship during cleaning of a transfer belt in a reversal development process of the image forming apparatus of FIG. 1;

FIG. 7 is a configuration diagram illustrating a state in which a transfer belt of the image forming apparatus in FIG. 1 is inclined in a direction away from a photosensitive drum.

FIG. 8 is a diagram schematically showing a potential relationship at the time of image transfer in a normal development process as another embodiment of the development process.

FIG. 9 is a diagram schematically showing a potential relationship at the time of cleaning of a transfer belt in a regular developing process as another embodiment of the developing process.

FIG. 10 is a configuration diagram showing another embodiment of a developer charging unit.

FIG. 11 is a configuration diagram showing another embodiment of a developer charging unit.

FIG. 12 is a perspective view showing a unit frame for holding a transfer belt of the image forming apparatus of FIG. 1;

[Explanation of symbols]

1a to 1d: process unit (image forming means), 10a
10 to 10d: photosensitive drum (image carrier), P: paper (transfer material), 15a to 15d: cleaner (removal means), 17 ...
Transfer belt (transfer material transporting means), 19a to 19d: power supply roller (power supply member), 34: bias power supply (bias voltage applying means), 35: toner charging brush (developer charging means).

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Haruhiko Ishida 70 Yanagimachi, Yuki-ku, Kawasaki-shi, Kanagawa Examiner, Toshiba Yanagicho Plant Co., Ltd. Fumio Komiyama (56) References JP-A-3-167579 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/01 114

Claims (3)

(57) [Claims] 1. A plurality of image forming means for forming a developer image at predetermined intervals arranged to image carrier, before the developer image is formed by the plurality of image forming means
Serial sequence against a plurality of image bearing members, opposed of the transfer material and the transfer material conveying means for carrying and conveying the carrying surface, the image bearing member via the transfer material transport unit
A plurality of feeding members, by applying a bias voltage to the power supply member,
Bias voltage applying means for transferring the developer image on the image carrier to the transfer material; and a plurality of removing means for removing and collecting the developer remaining on the image carrier after transferring the image to the transfer material. And a developer charging means for charging a developer adhered to the support surface of the transfer material transporting means to the same polarity as the bias voltage, comprising: a transfer means on the transfer material transporting means charged by the developer charging means. An image of the developer positioned at the most downstream side in the transport direction of the transfer material
When the transfer material is not interposed between the carrier and the power supply member facing the image carrier, the transfer to the image carrier is performed by applying a bias voltage to the power supply member by the bias voltage application unit. Characteristic image forming apparatus. 2. The method according to claim 2, wherein the transfer material is carried out of the plurality of removing means.
Developing the removing means of the image forming means located at the most downstream side in the feeding direction
Make the developer capacity larger than the developer capacity of other removal means.
The image forming apparatus according to claim 1, wherein the a. 3. The image forming apparatus according to claim 2, wherein said transfer material transporting means is provided with said plurality of
A first position in contact with all of the body and the plurality of image carriers;
Contacting only one of the image carriers from other image carriers
Is provided with a driving means for moving between the separated second position.
The image forming apparatus according to claim 1, wherein the was e.