JP4474023B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes one or a plurality of image forming units, a transfer unit that transfers a toner image formed on an image carrier in the image forming unit to a transfer material or intermediate transfer member, and a transfer material carrier or intermediate The present invention relates to an image forming apparatus having a cleaning unit for removing unnecessary toner on a transfer body.
[0002]
[Prior art]
FIG. 5 shows an example of an image forming apparatus using a four-color full-color conventional electrophotographic system in which four process stations 2a, 2b, 2c, and 2d as image forming units are arranged side by side. The structure of the apparatus D is shown.
[0003]
The process stations 2a to 2d have photosensitive drums 21a to 21d as image carriers, and the surfaces of the photosensitive drums 21a to 21d are uniformly charged by a primary charger and then exposed to, for example, LEDs or lasers. An electrostatic latent image is formed by exposure based on image information by the apparatus. The electrostatic latent image is developed as a toner image by attaching toner of each color by a developing device.
[0004]
Each of the process stations 2a to 2d can be attached to and detached from the image forming apparatus D main body (not shown) as a process cartridge PC. As shown in FIG. 6, each process cartridge PC has a configuration in which photosensitive drums 21a to 21d, a primary charger 22, a developing device 24, and cleaning means 25 and 26 are integrated together.
[0005]
Referring to FIG. 5, in the case of the image forming apparatus D, the transfer material P is fed into the image forming apparatus D from the sheet feeding cassette 18 by the sheet feeding roller 14, conveyed to the registration roller 13 and the resist facing roller 10, and then The suction bias power source 12 is electrostatically attracted to the transfer belt 1 of the transfer material carrier by the suction roller 15 to which a positive suction bias is applied, and is carried and transported.
[0006]
In the image forming apparatus D, the conveying belt 1 is wound around four rollers, that is, a driving roller 7, a suction counter roller 6, and tension rollers 8 and 9.
[0007]
Process stations 2a, 2b, 2c, and 2d for black, magenta, cyan, and yellow are arranged in series in this order from the upstream along the moving direction of the conveyor belt 1 (the direction of arrow R1).
[0008]
The transfer material P adsorbed on the conveyance belt 1 sequentially passes through the process stations 2a to 2d of the respective colors, and the toner images of the respective colors on the photosensitive drums 21a to 21d are electrostatically transferred sequentially. Thereafter, these toner images are heated and pressed by the fixing device 16 to be fixed on the transfer material P, thereby forming a permanent image.
[0009]
The conveyor belt 1 that has completed a series of operations is neutralized by the neutralization charger 11 to prepare for the next image forming process.
[0010]
Since the above-described conveying belt 1 does not normally carry a toner image directly on its surface, it is less likely to be contaminated with toner. However, in the case of jamming or when the background fog toner adheres to the non-image area, or when using a system in which a registration mark or density detection pattern is directly formed on the conveyance belt 1 to detect this, the conveyance belt 1 The toner adheres directly to the surface.
[0011]
In order to remove this, a separate cleaning device 17 can be provided. Here, a method of applying a cleaning bias to the transfer blades 3a, 3b, 3c, and 3d constituting the transfer means will be described.
[0012]
The transfer blades 3a, 3b, 3c, and 3d are generally made of a low-resistance resin film as a material. The photosensitive drums 21a, 21b, 21c, and 21d in each of the process stations 2a, 2b, 2c, and 2d and the conveyance belt are used. When the toner image is transferred to the transfer material, a transfer bias is applied from the transfer bias power supplies 4a, 4b, 4c, and 4d.
[0013]
2. Description of the Related Art Conventional electrophotographic image forming apparatuses have, for example, a developing unit including a negative organic photoreceptor as the photosensitive drums 21a to 21d and a negative toner as a developer. Accordingly, a positive transfer bias is applied to the transfer blades 3a to 3d by the transfer bias power sources 4a to 4d during transfer.
[0014]
The transfer blades 3a to 3d function as a part of the transfer unit as described above, but also function as a cleaning unit for the transfer belt 1. In the case of the image forming apparatus D, when the transfer belt 1 is cleaned, the bias applied to the transfer blades 3a and 3c is switched from positive to negative by the bias changeover switches 5a and 5c. That is, the power source connected to 3a and 3c is switched from the power source 4a and 4c to which the positive polarity bias is applied to the power source 4a 'and 4c' to which the negative polarity bias is applied by the bias changeover switches 5a and 5c. Then, a cleaning bias is applied to the transfer blades 3a to 3d in the order of, for example, negative, positive, negative, and positive from the upstream station, and the toner adhering on the conveyance belt 1 is efficiently reversely transferred to the photosensitive drums 21a to 21d. Thus, proposals have already been made to remove the residual toner on the transfer belt 1.
[0015]
More specifically, for example, a cleaning bias (main cleaning bias) that forms an electric field opposite to that at the time of transfer is applied to the transfer blades 3a and 3c among the transfer blades 3a to 3d from the power source 4a'4c ', and normal polarity toner is applied. Reverse transfer is performed on the photosensitive drums 21a and 21c, and a cleaning bias (sub-cleaning bias) having the same polarity as that at the time of transfer is applied to the transfer blades 3b and 3d from the same power source 4b and 4d as that at the time of transfer, and toner having a reverse polarity is exposed The toner is reversely transferred to the drums 21b and 21d, and the toner adhering to the conveyance belt 1 is removed to the photosensitive drums 21a to 21d.
[0016]
The toner reversely transferred to the photosensitive drums 21a to 21d in the cleaning process of the transport belt 1 as described above is collected as waste toner in a waste toner container 26 (FIG. 6) provided in the process stations 2a to 2d. Has been.
[0017]
The cleaning means in the process stations 2a to 2d will be described with reference to FIG.
[0018]
FIG. 6 shows a schematic configuration of a process station (image forming unit) 2a of the image forming apparatus D. All the other three process stations 2b to 2d have the same structure.
[0019]
The process station 2a shown in the figure has a photosensitive drum 21a that rotates in the direction of arrow R21 as an image carrier, and the surface of the process station 2a is uniformly charged by a primary charger 22 during image formation. An electrostatic latent image is formed by exposure based on image information by an exposure device 23 such as an LED or a laser. The electrostatic latent image is developed as a toner image by the toner 19 attached thereto by the developing sleeve 24 'of the developing device 24 rotating in the direction of arrow R24. On the other hand, the toner 19 ′ (transfer residual toner) that is not transferred to the transfer material during the transfer of the toner image and remains on the surface of the photosensitive drum 21 a is removed by the cleaner cleaning blade 25 and collected in the waste toner container 26. The photosensitive drum 21a whose surface is thus cleaned is used for the next image formation.
[0020]
The toner reversely transferred to the photosensitive drums 21a to 21d at the time of cleaning is also provided in the respective process stations 2a to 2d in the same manner as the transfer residual toner 19 'of the photosensitive drums 21a to 21d at the time of image formation as described above. It is removed from the surface of the photosensitive drums 21 a to 21 d by the blade 25 and collected in the waste toner container 26.
[0021]
The cleaning of the transport belt 1 by the cleaning bias described above has an effect of reducing the load of the cleaning means and reducing waste toner (dispersion to the photosensitive drum cleaner) even when the transport belt 1 has a separate cleaning means.
[0022]
[Problems to be solved by the invention]
However, in the case of the cleaning means as described above, an effective cleaning performance can be maintained with a toner having a relatively low charge amount (for example, −5 to −30 μC / g). If the charge amount of the toner to be used is high, a sufficient effect may not always be obtained. For this reason, it may be necessary to increase the cleaning time, and there is a concern that problems such as deterioration of the image forming member may occur.
[0023]
According to another proposal, the peripheral speed of the conveying belt 1 is set to a photosensitive drum for toner having a high charge amount (for example, −40 to −80 μC / g) that cannot be removed only by applying the cleaning bias as described above. It has been proposed that the conveyor belt 1 be cleaned more efficiently by setting it faster than 21a to 21d.
[0024]
However, in this case, it is necessary to drive the transport belt 1 by a drive source different from the photosensitive drums 21a to 21d, leading to an increase in cost. In addition, wear deterioration due to rubbing due to a large speed of the conveyance belt 1 and the photosensitive drums 21a to 21d occurs, and thus the life of the photosensitive drums 21a to 21d may be shortened.
[0025]
As another conventional example, a toner image on an image carrier is primarily transferred to an intermediate transfer member, and the toner image transferred to the intermediate transfer member is secondarily transferred collectively to a transfer material to form an image. Also in the image forming apparatus, since the toner image is directly transferred to the intermediate transfer member, the same problem as described above exists.
[0026]
Accordingly, an object of the present invention is to effectively clean a transfer material carrier or an intermediate transfer member in a short time in an in-line type image forming apparatus having one or a plurality of image forming units, and thereby to carry an image. An object of the present invention is to provide an image forming apparatus capable of reducing deterioration of an image forming member such as a body.
[0027]
[Means for Solving the Problems]
  The above object is achieved by the image forming apparatus according to the present invention. In summary, according to the first aspect of the present invention, each of the first invention includes an image carrier on which a toner image is formed on the surface, and an image carrier cleaning means for removing unnecessary toner on the image carrier. An image forming unit and a second image forming unit,
  A first transfer unit that receives a transfer bias voltage and transfers a toner image on the image carrier of the first image forming unit to a transfer material;
  A second transfer means for receiving a transfer bias voltage and transferring a toner image on the image carrier of the second image forming unit to a transfer material;
  A transfer material carrier that rotates to contact and transfer the transfer material in the order of the image carrier of the first image forming unit and the image carrier of the second image forming unit;
  In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the transfer material carrier,
  In the cleaning operation mode, the residual toner is reversely transferred to the image carrier in one of the first transfer unit and the second transfer unit.DCA cleaning bias voltage is applied, and on the other hand, a cleaning static elimination bias voltage is applied to reduce the charge amount of the residual toner, alternating current or direct current superimposed on alternating current,
  The region on the transfer material carrier on which the cleaning neutralizing bias voltage is appliedDCBy rotating the transfer material carrier so that a cleaning bias voltage acts, the charge amount of the residual toner is reduced, and then the residual toner is reversely transferred to the image carrier and reversely transferred to the image carrier. The image forming apparatus is characterized in that the toner thus removed is removed by the image carrier cleaning means.
[0028]
  According to a second aspect of the present invention, each of the first image forming units includes an image carrier on which a toner image is formed on a surface, and an image carrier cleaning unit that removes unnecessary toner on the image carrier. And a second image forming unit,
  A first primary transfer means for receiving a primary transfer bias voltage and primarily transferring a toner image on the image carrier of the first image forming unit to an intermediate transfer body;
  Second primary transfer means for primary transfer of the toner image on the image carrier of the second image forming unit to the intermediate transfer body in response to application of a primary transfer bias voltage;
  Of the first image forming unitSaidAn image carrier of the second image forming unitSaidAn intermediate transfer member that rotates to contact the image carrier in order;
  Secondary transfer means for performing secondary transfer of the toner images primarily transferred from each of the image carriers onto the intermediate transfer body collectively onto a transfer material,
  In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the intermediate transfer member,
  In the cleaning operation mode, the residual toner is reversely transferred to the image carrier on one of the first primary transfer unit and the second primary transfer unit.DCA cleaning bias voltage is applied, and on the other hand, a cleaning static elimination bias voltage is applied to reduce the charge amount of the residual toner, alternating current or direct current superimposed on alternating current,
  The region on the intermediate transfer member on which the cleaning neutralizing bias voltage has actedDCBy rotating the intermediate transfer member so that a cleaning bias voltage acts, the charge amount of the residual toner is reduced, and then the residual toner is reversely transferred to the image carrier, and is reversely transferred to the image carrier. The toner is removed by the image carrier cleaning means.
[0029]
  According to a third aspect of the present invention, there is provided an image carrier on which a toner image is formed on the surface, an image carrier cleaning means for removing unnecessary toner on the image carrier, and a transfer material carrier that rotates while carrying a transfer material. A transfer means for transferring a toner image on the image carrier to the transfer material upon application of a transfer bias voltage,
  In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the transfer material carrier,
  In the cleaning operation mode, the residual toner is reversely transferred to the image carrier.DCA cleaning bias voltage application unit that selectively applies to the transfer unit a cleaning bias voltage and a cleaning neutralization bias voltage that reduces the charge amount of the residual toner, or alternating current or direct current is superimposed on the alternating current;
  Due to the rotation of the transfer material carrier, the region on the transfer material carrier on which the cleaning neutralizing bias voltage has acted is applied.DCSwitching means for switching the bias voltage applied to the transfer means by the bias voltage applying means during the cleaning operation so that the cleaning bias voltage acts,
  An image characterized in that after the charge amount of the residual toner is reduced, the residual toner is reversely transferred to the image carrier, and the toner reversely transferred to the image carrier is removed by the image carrier cleaning means. Forming device.
[0030]
  According to a fourth aspect of the present invention, there is provided an image carrier on which a toner image is formed, an image carrier cleaning means for removing unnecessary toner on the image carrier, a rotating intermediate transfer member, and a primary transfer bias voltage. The toner image on the image carrier is primarily transferred to the intermediate transfer member in response toonceThe transfer unit and the toner image primarily transferred to the intermediate transfer member are secondarily transferred to a transfer material.secondaryAnd a transfer means,
  In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the intermediate transfer member,
  In the cleaning operation mode, the residual toner is reversely transferred to the image carrier.DCThe cleaning bias voltage and the cleaning neutralizing bias voltage in which the charge amount of the residual toner is reduced, the AC or the AC is superimposed on the DC,onceA bias voltage applying means for cleaning operation selectively applied to the transfer means;
  Due to the rotation of the intermediate transfer member, the region on the intermediate transfer member to which the cleaning neutralizing bias voltage has acted is applied.DCThe bias voltage applying means during the cleaning operation causes the cleaning bias voltage to act.onceSwitching means for switching the bias voltage applied to the transfer means,
  An image characterized in that after the charge amount of the residual toner is reduced, the residual toner is reversely transferred to the image carrier, and the toner reversely transferred to the image carrier is removed by the image carrier cleaning means. Forming device.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to examples.
[0033]
Example 1
The image forming apparatus A shown in the schematic configuration diagram of FIG. 1 is a so-called in-line four-color full-color image forming having process stations 2a to 2d which are four image forming units that form toner images of different colors. Device.
[0034]
  The image forming apparatus A includes a conveyance belt (electrostatic adsorption conveyance belt) 1 that is a transfer material carrier. The process from when the transfer material P is fed to when it is transferred, fixed and discharged is shown in the figure.5Since this is the same as the conventional image forming apparatus D, the cleaning process will be described.
[0035]
As a method for collecting the toner adhering to the conveying belt 1 described above, among the transfer blades 3a to 3d constituting the transfer means, for example, in the transfer blades 3a and 3c, bias is applied to 3a and 3c by the bias changeover switches 5a and 5c. The power supply to be switched is switched from the power supply (transfer bias power supply) 4a, 4c for applying a positive polarity bias at the time of transfer to the power supply (main cleaning bias power supply) 4a ', 4c' for applying a reverse polarity bias. For example, −2 kv is applied as a cleaning bias (main cleaning bias) for forming an electric field, and toner of normal polarity is reversely transferred to the photosensitive drums 21a and 21c. Further, for example, +1 kv is applied as a cleaning bias (sub-cleaning bias) of the same polarity from the power supply 4b during transfer to the transfer blade 3b, and reverse polarity toner is reversely transferred to the photosensitive drum 21b, which is used as waste toner in the image forming unit. The waste toner containers 26 (FIG. 6) in the certain process stations 2a to 2d are collected. At this time, in order to reduce the toner charge amount and weaken the attracting force with the belt, the transfer blade 3d is switched from the transfer bias power supply 4d to the cleaning static elimination bias power supply 4d ′ by the changeover switch 5d. Switching is applied, and a cleaning static elimination bias (for example, AC voltage Vpp2 kv, frequency 500 Hz, DC voltage +500 v) in which DC is superimposed on AC is applied.
[0036]
Although the conveyance belt 1 is cleaned by the above-described operation, when the cleaning mode is provided, the conveyance belt 1 is rotated by a rotation distance equal to or greater than the rotation distance obtained by subtracting the distance between the transfer blades 3c to 3d from the two rotations. Since the main cleaning bias and the sub-cleaning bias can be applied to the entire surface transfer area of the belt 1 after applying the static elimination bias, all unnecessary toners on the conveyor belt 1, that is, normal polarity toner and opposite polarity toner Can be reversely transferred to the photosensitive drums 21a to 21d and recovered by the cleaning means 25 and 26 in the process stations 2a to 2d.
[0037]
In the present invention, in order to enhance the cleaning ability of the conveyor belt 1, when a cleaning bias is applied, an AC bias is applied to at least one process station to reduce the charge amount of the toner, and exhibit the cleaning performance of other process stations. And having a stable cleaning ability over a long period of time.
[0038]
When the cleaning neutralizing bias is applied to 3a, the main cleaning bias is applied to 3b and 3d, and the sub-cleaning bias is applied to 3c, the minimum distance of the conveying belt 1 rotated during cleaning is one rotation and the distance between the transfer blades 3a to 3d. Cleaning time can be shortened.
[0039]
There are several combinations of biases in each process station, but the above-mentioned cleaning static elimination bias is applied to at least one process station, and this is combined with the main cleaning bias and sub-cleaning bias so that all parts on the conveyor belt 1 are cleaned. By setting the cleaning rotation speed so as to pass through the main and sub-cleaning bias application units after passing through the static elimination bias application unit, effective cleaning can be performed.
[0040]
Example 2
FIG. 2 shows a configuration diagram of an image forming apparatus B using an intermediate transfer member according to another embodiment of the present invention.
[0041]
In the image forming apparatus A using the conveyance belt 1, the toner images of the respective colors formed at the process stations 2a to 2d are directly transferred to the transfer material P, whereas the image forming using the intermediate transfer member 50 shown in FIG. In the apparatus B, the toner images formed at each of the process stations 2a to 2d are temporarily transferred onto the intermediate transfer belt 50 as an intermediate transfer member and superimposed, and then transferred onto the transfer material P all at once. Yes.
[0042]
The image forming apparatus B of this example has an intermediate transfer belt 50 wound around three rollers, a driving roller 7, a tension roller 8, and a secondary transfer counter roller 51, and is driven to rotate in the direction of arrow R1 in the figure. Is done. In general, the intermediate transfer belt is made of synthetic resin, rubber, or a combination thereof. The intermediate transfer belt 50 used here uses a polyimide resin film as an example, and has a thickness of about 10⁹It has a single-layer structure having a volume resistance of Ω · cm and a thickness of 100 μm.
[0043]
Along the peripheral surface of the intermediate transfer belt 50, black, magenta, cyan, and yellow image forming units, that is, process stations 2a, 2b, 2c, and 2d for the respective colors are disposed.
[0044]
The latent images on the photosensitive drums 21 a to 21 d in the process cartridges are visualized with the toner of the developing device 24, and are sequentially transferred to the intermediate transfer belt 50, thereby forming a full color image on the intermediate transfer belt 50. The formed toner image is supplied from the paper feed cassette 18 by the paper feed roller 14 at a predetermined timing, and is collectively collected using the secondary transfer roller 52 on the transfer material P fed by the registration roller 13 and the resist facing roller 10. Secondary transferred. The transferred image is conveyed to the fixing device 16 where it is pressurized and heated to obtain a permanent image.
[0045]
In the case of this embodiment, the untransferred toner remains on the intermediate transfer belt 50 as unnecessary toner, and the toner adheres when jamming or when a registration mark or density detection pattern is formed, and it is necessary to clean it.
[0046]
Since this cleaning method can be thought of as replacing the conveyance belt 1 of the first embodiment with the intermediate transfer belt 50, the description thereof is omitted.
[0047]
When the cleaning bias method is used as the belt cleaning method of the inline type color image forming apparatus, there has been a problem that the cleaning process has a long time. However, according to the embodiment, the belt of a large amount of toner is used. Even when contamination occurs, cleaning can be performed in a short time (a time required for the conveyor belt 1 to make one or two revolutions).
[0048]
Example 3
In the first and second embodiments, the in-line method, that is, the image forming apparatus having a plurality of image forming units has been described. However, the present invention is also effective for an image forming apparatus having only one image forming unit. In this embodiment, an image forming apparatus C which is an example of such an image forming apparatus will be described. FIG. 3 is a schematic side view of the image forming apparatus C.
[0049]
In this apparatus, the transfer material P taken out from the cassette 18 is supplied to a transfer drum 30 which is a transfer material carrier via a registration roller 13 and a registration counter roller 10. As shown in FIG. 4, the transfer drum 30 is formed of a cylindrical body in which a dielectric film 33 is stretched in the circumferential direction in the airspace of a frame body having rings 31 and 32 arranged at both ends. A recording material gripper 34 is provided as necessary.
[0050]
When the transfer material P reaches the transfer drum 30, the transfer material P is adsorbed and fixed on the transfer drum 30 by an adsorption means (not shown) including an adsorption charging member and a counter electrode, and rotates together with the transfer drum 30. To do.
[0051]
On the other hand, an image signal of cyan component color obtained from an original is projected onto the surface of an image carrier 21 that is an electrophotographic photosensitive member uniformly charged by a primary charger 22, and is When an electrostatic latent image having a cyan component color is formed on the toner image, and the latent image reaches a developing portion where the image carrier 21 and the developing device 24a containing cyan toner face each other, cyan toner is supplied from the developing device 24a. The latent image is developed as a cyan toner image.
[0052]
When the cyan toner image reaches a transfer portion where the image carrier 21 and the transfer drum 30 face each other, the transfer material P arrives at the transfer portion so as to be synchronized with the transfer portion 30 and is disposed inside the transfer drum 30. A toner image on the image carrier 21 is transferred to the transfer material P by applying a transfer bias from the power supply 4g to the transfer blade 3 constituting the transfer means.
[0053]
Thereafter, the transfer material P rotates while being carried on the transfer drum 30 and reaches the transfer portion again. By this time, the developing device 24b containing magenta toner has rotated to the development site to form a magenta toner image on the image carrier 21, and this magenta toner image has reached the transfer site. The magenta toner image on the image carrier 21 is transferred from the cyan toner image that has already been transferred onto the transfer material P of the transfer drum 30 at the transfer portion. Thereafter, similarly, a yellow toner image developed by the developing device 24c and a black toner image developed by the developing device 24d are sequentially superimposed and transferred onto the recording material P.
[0054]
After the transfer of the four color toner images is completed, the transfer material P is neutralized by the neutralization chargers 35 and 36 and then separated from the transfer drum 30 to reach the fixing device 16 where the color toner images are mixed. Then, after being fixed on the transfer material P to form a full-color print image, it is discharged out of the apparatus.
[0055]
In the above, the dielectric film 33 on the surface of the transfer drum 30 is made of dielectric resin such as PET, polyvinylidene fluoride, (PVdF), polycarbonate resin (PC), polyurethane resin (PU), polyimide resin (PI), or rubber resin. In order to have appropriate electrical characteristics and strength, a conductive filler is appropriately mixed in these dielectric resins.
[0056]
In the case of this embodiment, the transfer drum 30 which is a transfer material carrier does not directly transfer the toner image as in the case of the conveyor belt 1 of the first embodiment, but at the time of jam, ground fog toner, registration mark, Depending on the density detection pattern or the like, unnecessary toner adheres and needs to be cleaned.
[0057]
The cleaning method can also be performed by the transfer blade 3 of the transfer means.
[0058]
The transfer blade 3 is disposed inside the transfer drum 30 and is in contact with the image carrier 21 via the transfer drum 30. At this time, the cleaning bias is applied by switching the bias switching switch 5 between positive, sub, and static elimination by switching means (not shown). For example, at the time of cleaning, the transfer drum 30 is rotated, and the bias power supply of the transfer blade 3 is connected to a power source 4e that is alternating current or a direct current superimposed on the alternating current for the first round. The positive cleaning bias is connected to the antipolar power supply 4f, the third rotation is connected to the positive power supply 4g of the transfer bias, the sub-cleaning bias is applied in the order of the fourth rotation, and the positive cleaning bias is applied in turn. That is, unnecessary toner on the transfer drum 30 is reversely transferred to the image carrier 21 by applying a positive and sub-cleaning bias after applying a cleaning charge removal bias to reduce the charge amount, and a waste toner container 26. To recover.
[0059]
By applying the cleaning neutralization bias to the transfer blade 3 and then adjusting the rotation speed of the transfer drum 30 so that the positive and sub-cleaning biases are applied at least once, unnecessary toner on the entire area of the transfer drum 30 is discarded. It can be removed to the toner container 26.
[0060]
In this embodiment, the image forming apparatus C is configured to use the drum-shaped transfer material carrier. However, after the toner image on the image carrier is primarily transferred to the drum-shaped intermediate transfer member, the intermediate transfer is performed. Even in an image forming apparatus configured to collectively transfer images formed on a body onto a transfer material, the cleaning unit of the present invention can be applied to an intermediate transfer body.
[0061]
The primary and secondary cleaning biases in the first to third embodiments are not simply determined by the positive and negative polarities, but are relative values with respect to the surface potential of the photosensitive drum. For example, when cleaning the photosensitive drum, Assuming that the potential is −600 V or less, the reverse polarity cleaning bias that forms an electric field opposite to that at the time of transfer here is −600 V or more.
[0062]
In the above embodiments, only the belt-shaped and drum-shaped transfer material carriers and intermediate transfer members have been described. However, the present invention is not particularly limited thereto. Moreover, although the example using a blade as the transfer means has been described, it is also possible to use a transfer roller, a transfer brush, or the like instead.
[0063]
In the above embodiments, only the full-color image forming apparatus has been described. However, the present invention is also effective for a single-color image forming apparatus.
[0064]
【The invention's effect】
  As explained above, the present inventionAccording to
(1) At least one image forming unit applies a cleaning neutralization bias to neutralize the toner, thereby reducing the charge amount of the toner and exhibiting the cleaning performance of other positive and negative cleaning biases. Toner can be efficiently reverse-transferred to the image carrier.
(2) Accordingly, it becomes possible to shorten the cleaning process and to suppress the wear of the image carrier and the developing device and other deterioration due to the transfer carrier rotating a plurality of times in the cleaning process.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment of the invention.
FIG. 3 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to Embodiment 3 of the present invention.
4 is a perspective view of a transfer drum used in Embodiment 3. FIG.
FIG. 5 is a longitudinal sectional view showing an example of a conventional image forming apparatus.
FIG. 6 is a longitudinal sectional view of a process station.
[Explanation of symbols]
1 Transfer material carrier (conveyor belt)
2a to 2d Image forming unit (process station)
3, 3a-3d Transfer blade
4a-4d, 4g Transfer bias power supply
4a'4c'4f Main cleaning bias power supply
4d'4e Cleaning neutralization bias power supply
5, 5a, 5c, 5d Bias switch
19 Toner
19 ’Waste toner
21, 21a to 21d Image carrier
25 Cleaner (cleaning blade)
26 Waste toner container
30 Transfer material carrier (transfer drum)
50 Intermediate transfer member (intermediate transfer belt)
51 Secondary transfer counter roller
52 Secondary transfer roller

Claims (8)

A first image forming unit and a second image forming unit each having an image carrier on which a toner image is formed on the surface and an image carrier cleaning means for removing unnecessary toner on the image carrier. When,
A first transfer unit that receives a transfer bias voltage and transfers a toner image on the image carrier of the first image forming unit to a transfer material;
A second transfer means for receiving a transfer bias voltage and transferring a toner image on the image carrier of the second image forming unit to a transfer material;
A transfer material carrier that rotates to contact and transfer the transfer material in the order of the image carrier of the first image forming unit and the image carrier of the second image forming unit;
In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the transfer material carrier,
In the cleaning operation mode, a DC cleaning bias voltage that reversely transfers the residual toner to the image carrier is applied to one of the first transfer unit and the second transfer unit. Applying a cleaning static elimination bias voltage that reduces the charge amount of the residual toner, alternating current or direct current superimposed on alternating current,
By rotating the transfer material carrier so that the DC cleaning bias voltage acts on the area on the transfer material carrier on which the cleaning charge-eliminating bias voltage acts, the charge amount of the residual toner is reduced. Then, the residual toner is reversely transferred to the image carrier, and the toner reversely transferred to the image carrier is removed by the image carrier cleaning means.   2. The image forming apparatus according to claim 1, wherein in the cleaning operation mode, the cleaning bias voltage is applied to the first transfer unit, and the cleaning discharge bias voltage is applied to the second transfer unit. .   2. The image forming apparatus according to claim 1, wherein in the cleaning operation mode, the cleaning neutralization bias voltage is applied to the first transfer unit, and the cleaning bias voltage is applied to the second transfer unit. . A first image forming unit and a second image forming unit each having an image carrier on which a toner image is formed on the surface and an image carrier cleaning means for removing unnecessary toner on the image carrier. When,
A first primary transfer means for receiving a primary transfer bias voltage and primarily transferring a toner image on the image carrier of the first image forming unit to an intermediate transfer body;
Second primary transfer means for primary transfer of the toner image on the image carrier of the second image forming unit to the intermediate transfer body in response to application of a primary transfer bias voltage;
An intermediate transfer body rotating said image bearing member of the first image forming unit, so as to contact the order of the image bearing member of said second image forming unit,
Secondary transfer means for performing secondary transfer of the toner images primarily transferred from each of the image carriers onto the intermediate transfer body collectively onto a transfer material,
In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the intermediate transfer member,
In the cleaning operation mode, a DC cleaning bias voltage that reversely transfers the residual toner to the image carrier is applied to one of the first primary transfer unit and the second primary transfer unit, and the other Applying a cleaning static elimination bias voltage that reduces the charge amount of the residual toner, alternating current or direct current superimposed on alternating current,
After the charge amount of the residual toner is reduced by rotating the intermediate transfer member so that the DC cleaning bias voltage acts on the region on the intermediate transfer member on which the cleaning neutralizing bias voltage acts. An image forming apparatus, wherein the residual toner is reversely transferred to the image carrier, and the toner reversely transferred to the image carrier is removed by the image carrier cleaning means.   5. The image according to claim 4, wherein, in the cleaning operation mode, the cleaning bias voltage is applied to the first primary transfer unit, and the cleaning discharge bias voltage is applied to the second primary transfer unit. Forming equipment.   5. The image according to claim 4, wherein, in the cleaning operation mode, the cleaning neutralization bias voltage is applied to the first primary transfer unit, and the cleaning bias voltage is applied to the second primary transfer unit. Forming equipment. An image carrier on which a toner image is formed, an image carrier cleaning means for removing unnecessary toner on the image carrier, a transfer material carrier that rotates while carrying a transfer material, and a transfer bias voltage And a transfer means for transferring the toner image on the image carrier to the transfer material upon application,
In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the transfer material carrier,
In the cleaning operation mode, a DC cleaning bias voltage that reversely transfers the residual toner to the image carrier, and a cleaning static elimination bias voltage that reduces the charge amount of the residual toner, or alternating current or alternating current with direct current, A bias voltage applying means for cleaning operation selectively applied to the transfer means;
The bias voltage applying means during the cleaning operation causes the DC cleaning bias voltage to act on the region on the transfer material carrier on which the cleaning neutralizing bias voltage is applied by the rotation of the transfer material carrier. Switching means for switching the bias voltage applied to the transfer means,
An image characterized in that after the charge amount of the residual toner is reduced, the residual toner is reversely transferred to the image carrier, and the toner reversely transferred to the image carrier is removed by the image carrier cleaning means. Forming equipment. An image carrier on which a toner image is formed, an image carrier cleaning means for removing unnecessary toner on the image carrier, a rotating intermediate transfer member, and a primary transfer bias voltage applied to receive the image. includes a primary transfer means for primarily transferring the toner image on the carrier to the intermediate transfer body, a secondary transfer means for secondarily transferring to a transfer material the intermediate transfer member to the primarily transferred toner image, and
In the image forming apparatus having a cleaning operation mode for removing residual toner remaining on the intermediate transfer member,
In the cleaning operation mode, a DC cleaning bias voltage that reversely transfers the residual toner to the image carrier, and a cleaning static elimination bias voltage that reduces the charge amount of the residual toner, or alternating current or alternating current with direct current, A bias voltage applying means for cleaning operation selectively applied to the primary transfer means;
The primary transfer is performed by the bias voltage applying means during the cleaning operation so that the DC cleaning bias voltage acts on the region on the intermediate transfer body on which the cleaning neutralization bias voltage is applied by the rotation of the intermediate transfer body. Switching means for switching the bias voltage applied to the means,
An image characterized in that after the charge amount of the residual toner is reduced, the residual toner is reversely transferred to the image carrier, and the toner reversely transferred to the image carrier is removed by the image carrier cleaning means. Forming equipment.

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