JP2004302128A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent printing soil by recovering toner lying in an unexposed part and an exposed part on a photoreceptor 1 and unnecessary for printing before a transfer process, and to reuse the recovered toner. <P>SOLUTION: A toner recovery part is arranged adjacent to the photoreceptor 1, and a DC bias and an AC bias are applied on the toner recovery part. Alternatively, the recovery part is constituted of a recovery belt and a carrying roller for carrying/driving the recovery belt, and the toner is recovered by applying the DC bias and the AC bias. Alternatively, when a low-duty printing continues, the AC bias is applied on the toner recovery part and the toner discharge operation is periodically performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that generates an electrostatic latent image on a photoreceptor by a light source, transfers toner attached to the latent image to a print medium, and performs printing.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as shown in FIG. 7, an image forming apparatus, for example, an electrophotographic apparatus, includes a photoreceptor 1, a charging unit 2 for negatively charging the surface of the photoreceptor 1, and a photoreceptor by partially exposing the surface of the photoreceptor 1. A light source 3 for forming an electrostatic latent image (electric potential 0 V), a developing roller 4 for attaching a negative potential toner 9 to the formed electrostatic latent image, and a toner supply for negatively charging the toner 9 and conveying the toner 9 to the developing roller 4 A roller 5, a developing blade 6 for forming a uniform toner layer on the developing roller 4, a transfer unit 7 for transferring a toner image developed on the photoreceptor 1 to a print medium 10, a photoreceptor without being transferred 1 was composed of a cleaning unit 8 for collecting the residual toner remaining on the surface 1.
[0003]
In the conventional electrophotographic apparatus, toner charged to a negative potential by the toner supply roller 5, the developing roller 4, and the like is electrostatically attracted to an electrostatic latent image formed on the photoconductor 1, and Printing is performed by transferring the attracted toner to the print medium 10 by the transfer unit 7 and fixing the toner by a fixing unit (not shown). At this time, if the toner can be uniformly charged to a constant negative potential by the toner supply roller 5, the developing roller 4, and the like, the portion other than the portion where the electrostatic latent image is formed on the photoconductor 1, that is, the portion other than the exposed portion Since the unexposed portion is negatively charged, the negatively charged toner repels electrostatically, and the toner does not adhere. (For example, refer to Patent Document 1).
[0004]
[Patent Document 1]
JP-A-5-27567
[0005]
[Problems to be solved by the invention]
However, generally, in the image forming apparatus, there are a positively charged toner, a weakly negatively charged toner and a toner that is excessively charged to a negative potential, and these toners are transferred from the developing roller 4 to the unexposed portion of the photoconductor 1. The toner cannot be collected before the transfer process, so it is transferred to a print medium, causing not only staining but also collecting and reusing toner unnecessary for these printings. .
[0006]
[Means for Solving the Problems]
The present invention employs the following configuration in order to solve the above-described problems. That is, in the image forming apparatus of the first invention, a photoreceptor that rotates during image formation, a charging unit that charges a surface of the photoreceptor, an exposure unit that forms an electrostatic latent image on the surface of the charged photoreceptor,
An image forming apparatus including a developing unit that applies a developer to an electrostatic latent image formed by an exposing unit to perform development, and a transfer unit that transfers the developer adhered to the surface of the photoconductor by the developing unit to a transfer material And a member arranged downstream of the developing means and upstream of the transfer means in the rotation direction of the photoreceptor and to which an AC voltage is applied.
[0007]
In the image forming apparatus according to a second aspect, in the image forming apparatus according to the first aspect, a DC voltage is applied corresponding to a surface potential of the photoconductor.
[0008]
In an image forming apparatus according to a third aspect, in the image forming apparatus according to the first aspect, a transport unit that transports the developer attached to the member to the developing unit is provided.
[0009]
In an image forming apparatus according to a fourth aspect, in the image forming apparatus according to the first aspect, the developing means transfers a predetermined amount of the developing roller adjacent to the photoconductor and the developer attached to the developing roller to the photoconductor side. It consisted of means.
[0010]
In an image forming apparatus according to a fifth aspect of the present invention, in the image forming apparatus according to the second aspect of the present invention, the AC voltage applied to the member is in a range including the surface potential of the photoconductor.
[0011]
In an image forming apparatus according to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, the AC voltage applied to the member is applied to a developing roller adjacent to the photoconductor and to a charging unit. The voltage range was set.
[0012]
In an image forming apparatus according to a seventh aspect, in the image forming apparatus according to the first aspect, the frequency of the AC voltage applied to the member is approximately 1 kHz or more.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Elements common to the drawings are denoted by the same reference numerals.
[0014]
<< First Embodiment >>
The image forming apparatus according to the first embodiment is provided with a toner collecting roller, and applies a DC bias and an AC bias to the toner collecting roller to collect toner unnecessary for printing attached to the surface of the photoconductor 1. It was done.
[0015]
(Constitution)
As shown in FIG. 1, the image forming apparatus according to the first embodiment includes a photoconductor 1 on which an electrostatic latent image is formed on a drum surface, and a charging unit 2 for setting the surface of the photoconductor 1 to a predetermined potential. A light source 3 for forming an electrostatic latent image on the photoreceptor 1, a developing roller 4 for transferring the toner 9 to an electrostatic latent image formed on the photoreceptor 1 for development, and a toner appropriately supplied from a toner cartridge (not shown) 9, a toner supply roller 5 for transferring the toner 9 to the developing roller 4, a toner blade 6 for forming a toner layer having a predetermined thickness on the developing roller 4, and printing of toner adhered on an electrostatic latent image formed on the photoconductor 1. The transfer unit 7 includes a transfer unit 7 for transferring the image onto the medium 10, a cleaning unit 8 for removing the transferred toner remaining on the surface of the photoconductor 1, and a collection roller 11 for collecting the toner, and is arranged as shown in FIG. ing.
[0016]
The collection roller 11 is connected in series with a DC bias set by a DC voltage setting unit 27a and an AC bias whose amplitude of an AC voltage is set by an AC voltage setting unit 27b. The control is performed by the collection roller voltage setting unit 27 in accordance with the instruction 24. A passage for feeding the collected toner to the toner supply roller 5 is provided below the collecting roller 11.
[0017]
Here, the collecting roller 11 is formed by heating a semiconductive rubber to form a roll on the outer periphery of a metal shaft, and using silicon rubber, urethane rubber, or the like as a base material of the rubber. It is formed by adding a conductive agent such as carbon black and molding, and forming a coat layer on the surface of the elastic layer. It is desirable to use a material having good releasability, such as a fluororesin, for the coat layer. Since the scraping blade 12 is a part to be worn, it is preferable that the scraping blade 12 is made of elastic rubber, and urethane rubber having good durability is used as the rubber base material.
[0018]
Further, detailed description is omitted because it is not directly related to the present invention. However, as shown in the figure, the developing roller 4, the toner supply roller 5, and the charging unit 2 are respectively provided with Vg, Vs, and Ve by voltage setting units (not shown). , And a positive bias voltage Vt is applied to the transfer unit 7 by a voltage setting unit (not shown). Of course, the positive and negative polarities may be exchanged.
[0019]
Next, FIG. 2 shows a configuration diagram of a control system of the image forming apparatus according to the first embodiment. As shown in the figure, the control system of the image forming apparatus 21 of the first embodiment is based on an interface unit 23 for receiving print data from the host device 22 and an output result of a print medium detection sensor (not shown). A control unit 24 that performs printing control and drive control of a print medium conveying motor. Under control of the control unit 24, a motor (not shown) is rotationally driven to convey the print medium 10 and rotationally drive each roller and the photoconductor 1. It comprises a motor drive circuit 25, a light source 3 for forming an electrostatic latent image on the photoconductor 1, such as images and characters, which are print data from the host device 22, and a collection roller voltage setting unit 27 for setting a bias voltage of the collection roller 11. Are connected as shown in FIG.
[0020]
(motion)
With the above configuration, the image forming apparatus of the first embodiment performs the printing operation as follows. The operation will be described with reference to the configuration diagram of the image forming apparatus in FIG. 1, the configuration diagram of the control system in FIG. 2, and the relationship diagram between the bias voltage and the toner potential of each section in FIG. FIG. 3A is a diagram for explaining the relationship between the bias voltage and the toner potential of each unit related to printing, and FIG. 3B is a diagram illustrating the relationship between the bias voltage of each unit and the toner potential related to toner recovery before transfer, which will be described in detail below. It is a figure for explaining a relation.
[0021]
(Development process)
First, when a voltage of, for example, Ve = -1150 V is applied to the charging roller of the charging unit 2, a potential drop occurs due to a gap between the charging roller and the photoconductor 1, and the surface of the photoconductor 1 is charged to approximately −700 V. . Then, the light source 3 eliminates the charge of the exposed portion of the surface of the photoconductor 1 corresponding to the image, characters, etc. to be printed, sets the potential to 0 V, and forms an electrostatic latent image on the surface of the photoconductor 1.
[0022]
On the other hand, the toner 9 is charged to a negative potential by rubbing the toner 9 supplied from a toner cartridge or the like (not shown) between the toner supply roller 5 and the developing roller 4. Here, a bias voltage Vs is applied to the toner supply roller 5, and a bias voltage Vg = −300 V is applied to the developing roller 4.
[0023]
Then, the toner 9 conveyed to the surface of the developing roller 4 is formed as a uniform toner layer by the toner blade 6. Then, the toner on the developing roller 4 charged to the negative potential is attracted to the exposed portion where the surface potential of the photoreceptor 1 is 0 V, and since the portion other than the exposed portion is -700 V, the toner is Are repelled, a toner image is formed on the electrostatic latent image on the photoconductor 1. At this time, as shown in FIG. 3A, the toner 9a charged to the positive potential, the toner 9b weakly negatively charged, and the toner 9c excessively charged to the negative potential adhere to the unexposed portion.
[0024]
(Toner collection process)
On the other hand, as shown in FIG. 1 and FIG. 3B, a −700 V DC bias is generated in the collection roller 11 by the DC voltage setting unit 27 a of the collection roller power setting unit 27, and the collection is performed by the AC voltage setting unit 27 b. A bias potential Vk in which an AC bias having an amplitude of 600 V and a frequency of about 1 kHz is applied to the DC bias is applied.
[0025]
As described above, by applying a DC bias and an AC bias to the collection roller 11, any one of the positively charged toner 9a, the weakly negatively charged toner 9b, and the excessively negatively charged toner 9c adhered to the unexposed portion. Can also be recovered. That is, since a bias is generated by the DC bias applied to the collection roller 11 and an oscillating electric field is generated, the positively charged toner 9a attached to the unexposed portion has a bias potential Vk of the collection roller 11 of more negative. The toner 9b having a weak negative charge and the excessively negatively charged toner 9c are attracted to the collection roller 11 when the electric potential is changed to the electric potential (at −1000 V in the figure), and are applied to the positive electric potential (−400 V in the figure). At this time, the toner is attracted to the collecting roller 11, so that the toner can be attached to the collecting roller 11.
[0026]
At the same time, Coulomb force also acts on the positively charged toner 9f attached to the exposed portion, so that the collecting roller 11 is attracted to the collecting roller 11 when the potential is negative (-400V to -1000V in the drawing). Therefore, it can be attached to the collection roller 11. Further, the negatively charged toner 9g adhered to the exposed portion of the photoconductor 1 to be printed repels and is not collected because the bias potential Vk of the collection roller 11 is a negative potential.
[0027]
The amplitude of the AC voltage is set such that the lower limit of the bias voltage Vk is -300 V applied to the developing roller 4 so as not to affect the halftone density, and the upper limit is -1150 V applied to the charging unit 2. However, it is preferable to set the upper and lower limits with a margin. For example, the lower limit is set to −400 V with a margin of 100 V, and the upper limit is set to 600 V with a margin of 150 V. Of course, the margin may be set to a value other than the above according to the shape, material, use environment, and the like of each part of the image forming apparatus.
[0028]
According to the experiment, when the frequency of the AC bias applied to the collecting roller 11 is set to a certain value or less, the AC voltage applied to the collecting roller 11 significantly affects the toner developed on the surface of the photoconductor 1, Since the printing unevenness may occur, the frequency of the AC voltage is preferably set to a certain value or more, for example, about 1 kHz or more.
[0029]
As described above, the toner collected by the collection roller 11 to which the bias voltage Vk is applied is scraped off by the scraping blade 12, pushed into the lower part of the toner supply roller 5, and conveyed to the upper part of the toner supply roller 5. It becomes a reusable toner.
[0030]
(Transfer process)
On the other hand, the toner on the exposed portion of the photoreceptor 1 is transferred to the print medium 10 because a bias of Vt = + 2000 V is applied to the transfer portion 7, and printing is performed by fixing the toner in a fixing portion (not shown). Is In FIG. 3A, the positively charged toner 9a repels the transfer unit 7 biased to a positive potential, and is not transferred. The toner collected by the collection roller 11 but not collected is attracted and transferred to the transfer unit 7 biased to a positive potential. Similarly, the positively charged toner 9d adhering to the exposed portion of the photoreceptor 1 is almost collected by the collecting roller 11 as described above. However, even if there is uncollected toner, it repels the transfer unit 7 biased to a positive potential. Will not be transcribed. Further, the negatively charged toner 9e attached to the exposed portion of the photoconductor 1 to be printed is attracted and transferred to the transfer portion 7 biased to a positive potential. Then, the toner on the photoconductor 1 that has not been transferred to the print medium is scraped off by the cleaning unit 8.
[0031]
(Effects of the First Embodiment)
As described above in detail, according to the image forming apparatus of the first embodiment, since the toner collecting roller is provided and the DC voltage and the AC voltage are applied to the toner collecting roller, the toner collecting roller adheres to the unexposed portion. Unnecessary toner for printing, such as weakly negatively charged toner and positively charged toner, can be collected before transfer, so high-quality printing with less contamination can be performed, and toner can be efficiently collected. Can be reused.
[0032]
<< Second Embodiment >>
The image forming apparatus according to the second embodiment is configured to convey the toner collected by a collection belt.
[0033]
(Constitution)
FIG. 4 shows the configuration of the image forming apparatus according to the second embodiment. For the sake of simplicity, a description of the same components as those of the image forming apparatus of the first embodiment will be omitted. That is, the photoconductor 1, the charging unit 2, the light source 3, the developing roller 4, the toner supply roller 5, the toner blade 6, the transfer unit 7, and the cleaning unit 8 have the same configuration as the image forming apparatus of the first embodiment. Yes, and the detailed description is omitted.
[0034]
As shown in the lower right side of FIG. 4, in the image forming apparatus according to the second embodiment, a toner collecting section for collecting and reusing toner is arranged in contact with the photoconductor 1 and the toner supply roller 5. I have to. Here, the toner collecting unit conveys the collected belt 31a that conveys the collected toner, a collection belt roller 31b that conveys and drives the collection belt 31a, a collection belt support roller 31c that rotatably supports the collection belt 31a, and a conveyance belt 31a. And a scraping blade 32 for scraping off the toner. Then, a passage is secured below the collection belt 31a in order to smoothly send the collected toner to the toner supply roller 5 side.
[0035]
Although not shown, a seal for preventing toner leakage may be appropriately disposed in a gap between the photosensitive member 1 and the like in order to prevent the toner from leaking below the toner collecting portion.
[0036]
The collection belt 31a is driven to be conveyed by a collection belt roller 31b that is driven to rotate counterclockwise by a motor drive circuit 35 controlled by a control unit described below. The collection belt 31a is formed of silicone resin, and the collection belt roller 31b is formed by heating semiconductive rubber and forming a roll on the outer periphery of a metal shaft. Silicon rubber, urethane rubber, or the like is used as the base material of the semiconductive rubber, and a conductive agent such as carbon black is added at the time of kneading before molding in order to impart semiconductivity. The collection belt support roller 31c is hollow by metal molding. Since the scraping blade 32 is a part to be worn, it is preferable to use a highly durable urethane rubber as a base material of the rubber.
[0037]
Further, similarly to the image forming apparatus of the first embodiment, the DC bias set by the DC voltage setting unit 37a and the amplitude of the AC voltage set by the AC voltage setting unit 37b are set on the collection belt roller 31b. An AC bias is connected in series, and these voltages are controlled by the recovery unit voltage setting unit 37.
[0038]
Although not directly related to the present invention, detailed description is omitted, but negative bias voltages Vg, Vs, and Ve are applied to the developing roller 4, the toner supply roller 5, and the charging unit 2 by voltage setting units (not shown). A positive bias voltage Vt is applied to the transfer unit 7 by a voltage setting unit (not shown). Of course, the positive and negative polarities may be exchanged.
[0039]
Next, FIG. 5 shows a configuration diagram of a control system of the image forming apparatus according to the second embodiment. As shown in the drawing, the control system of the image forming apparatus 41 according to the second embodiment includes an interface unit 23, a control unit 24, and the light source 3, similarly to the image forming apparatus according to the first embodiment. Further, under the control of the controller 24, a motor (not shown) is rotated to drive the conveyance of the print medium 10 and to rotate the respective rollers, the photoconductor 1, and the collection belt roller 31b. It comprises a recovery section voltage setting section 37 for setting the bias voltage Vk of 31b, and is connected as shown in FIG.
[0040]
(motion)
With the above configuration, in the image forming apparatus of the second embodiment, similarly to the operation of the image forming apparatus of the first embodiment, the toner collecting unit prints an unexposed portion or an exposed portion on the surface of the photoconductor 1. Unnecessary toner is collected, and the collected toner is conveyed by a collection belt 31 a using a lower path of the toner collection unit, scraped by a scraping blade 32, and reused by the toner supply roller 5.
[0041]
The operation of collecting the toner on the photoconductor 1 by the toner collecting unit (the relationship between the bias voltage and the toner potential of each unit) is the same as that of the image forming apparatus of the first embodiment described with reference to FIG. The description is omitted for simplification.
[0042]
In the description of the present embodiment, an example is shown in which the collection belt roller 31a is driven, the collection belt support roller 31c is rotationally supported, and the collection belt 31a is conveyed. For example, a configuration may be adopted in which a support roller is further provided between the collection belt roller 31a and the collection belt support roller 31c to prevent the collection belt from hanging. Further, the example in which the DC bias and the AC bias for collection are applied to the collection belt roller 31a has been described.
[0043]
(Effect of Second Embodiment)
As described in detail above, according to the image forming apparatus of the second embodiment, in addition to the effects of the image forming apparatus of the first embodiment, the toner collected by the toner collecting unit is transported by the collecting belt. With this configuration, the collected toner can be smoothly conveyed and reused without the passage of the collected toner being blocked due to the condensation of the toner below the toner supply roller 5.
[0044]
<< Third Embodiment >>
In the image forming apparatus according to the third embodiment, an AC bias is applied to the toner collecting unit to collect toner in a toner discharging operation appropriately performed to prevent deterioration of the toner.
[0045]
(Constitution)
The configuration of the image forming apparatus and the configuration of the control system according to the third embodiment are the same as those of the first and second embodiments, and therefore, detailed description thereof will be omitted.
[0046]
(motion)
The operation of the image forming apparatus according to the third embodiment will be described below. Among the operations of the image forming apparatus according to the third embodiment, the developing step, the recovering step, and the fixing step, which are normal printing steps, are the same as the operations of the image forming apparatuses according to the first and second embodiments. Therefore, the description is omitted for simplification.
[0047]
In general, when low-duty printing is performed continuously, the toner on the developing roller 4 is rubbed many times, the toner is deteriorated, and filming on the developing roller 4 and the developing blade 6 is caused by accumulation of frictional heat. Has been found to be more likely to occur.
[0048]
For this reason, in the third embodiment, the operation of periodically discharging the toner on the developing roller 4 (hereinafter, referred to as “toner discharging operation”) in order to prevent the above-described toner deterioration and filming is described below. To do.
[0049]
That is, as shown in the time chart of the bias voltage of each part in FIG. 6, first, when the printing operation is started (Ta) and it is determined that the low duty printing with a small number of printing parts is performed continuously, the control unit 24 determines Then, the printing operation is completed, and the toner discharging operation is started (Tb). During the printing operation, as described with reference to FIG. 3 in the first embodiment, the surface of the photoconductor 1 is set to −700 V, the bias voltage Vg of the developing roller 4 is set to −300 V, and the toner is collected. The bias voltage Vk of the unit is an AC bias having a DC bias of -700 V and an amplitude of 600 V.
[0050]
When the toner discharging operation is started, first, the entire surface is exposed so that the surface potential of the photoconductor 1 becomes 0 V, no voltage is applied to the developing roller 4 (that is, 0 V), and 0 V is applied to the toner collecting section. As the bias, an AC bias having an amplitude of 600 V and a frequency of about 1 kHz is applied.
[0051]
Then, since both the surface potential of the photosensitive member 1 and the applied bias of the developing roller 4 are 0 V, the toner having the 0 V potential is transferred to the photosensitive member 1 only by a mechanical force. Then, the alternating bias applied to the toner collecting unit generates an electric field of positive and negative alternately, and a Coulomb force acts on the toner having the potential of 0 V. The Coulomb force causes the toner to adhere to the toner collecting unit and be collected. be able to.
[0052]
After the toner discharging operation is performed for a predetermined time, the operation is switched to the printing operation again (Tc), and the printing operation is performed.
[0053]
Here, when the amount of toner to be discharged is large, that is, when the amount of toner transferred to the photoconductor 1 (hereinafter referred to as “developing efficiency”) is large among the amount of toner adhering to the developing roller 4 (developing efficiency 30%). In the above), it is experimentally known that the toner cannot be completely collected by the toner collecting unit. However, when the toner is transferred to the photoconductor 1 only by the mechanical force as described above, the developing efficiency is 10 to 25. %, Almost all the toner can be collected and reused.
[0054]
The toner collected by the toner collecting unit as described above is conveyed to the toner supply roller 5 and reused.
[0055]
In the above description, an example in which the DC bias of the photoconductor 1 and the developing roller 4 is 0 V and the DC bias of 0 V and the AC bias having an amplitude of 600 V are applied to the toner collecting unit in the toner discharging operation has been described. Even if the DC bias of the body 1 and the developing roller 4 is set to a voltage other than 0 V, and the DC bias of the toner collecting section is set to the same voltage as these bias voltages, the toner can be collected. The amplitude of the AC bias applied to the unit may be arbitrarily set instead of 600 V.
[0056]
(Effects of Third Embodiment)
As described above in detail, according to the image forming apparatus of the third embodiment, when low-duty printing is continued, an AC bias is applied to the toner collecting unit to perform the toner discharging operation. It is possible to prevent toner deterioration, filming, and the like, and to collect and reuse the toner.
[0057]
《Other modifications》
In addition to the embodiment described above, the same operation and effect of the present invention can be obtained in the following modified embodiment. That is,
[0058]
(1) In the description of the image forming apparatus according to the embodiment, an image forming apparatus that forms one color image by a printing mechanism including one light source, a photosensitive drum, a developing roller, and the like has been described. In an image forming apparatus that performs multi-color printing using a plurality of printing mechanisms, such as a color electrophotographic apparatus, the present invention can be applied to each printing mechanism of each color as appropriate.
[0059]
(2) Further, in the description of the image forming apparatus of the embodiment, the example in which the toner image is directly transferred from the photoreceptor 1 to the print medium has been described. The present invention can also be applied to an image forming apparatus that transfers a toner image from the photoreceptor 1 to an intermediate transfer drum or an intermediate transfer belt, such as an electrophotographic printing apparatus.
[0060]
(3) In the description of the image forming apparatus according to the first embodiment, the recovery roller is described as having a rotary shape. May be. Also, in the image forming apparatus of the second embodiment, a collecting piece to which a DC voltage and an AC voltage can be applied may be provided separately from the collecting section.
[0061]
(4) In the description of the image forming apparatus according to the embodiment, the frequency of the AC bias applied to the toner collecting unit is described as about 1 kHz. However, a number of frequencies higher than about 1 kHz are set, and this is selected and repeated. Alternatively, a frequency range may be determined, and the frequency in this range may be increased or decreased. The AC bias does not need to be a sine wave, and may be a rectangular wave or a triangular wave.In addition, instead of controlling the DC bias and the AC bias separately, for example, when generating a rectangular wave, You may make it generate | occur | produce including a bias.
[0062]
(5) In the description of the image forming apparatus according to the embodiment, an example has been described in which the frequency of the AC bias applied to the collection roller or the collection unit is set regardless of the rotation speed of the photoconductor 1. The frequency of the AC bias may be increased or decreased according to the transport speed or the rotation speed of the photoconductor 1. For example, when the rotation speed of the photoconductor 1 is low, the frequency of the AC bias may be lowered to more reliably collect the toner within a range where the toner on the photoconductor 1 is less affected.
[0063]
(6) In the image forming apparatus according to the embodiment, the example in which the amplitude of the AC bias applied to the toner collecting unit is simply set to a constant value has been described. Control may be performed so that the amplitude of the AC bias is increased to increase the efficiency, and the amplitude of the AC bias is reduced when the unexposed portion is small. Also, in the image forming apparatus of the third embodiment, the recovery efficiency may be improved by increasing or decreasing the amplitude of the AC bias in accordance with the development efficiency.
[0064]
【The invention's effect】
As described in detail above, according to the image forming apparatus of the present invention, since the toner collecting unit is provided and the AC bias is applied to the toner collecting unit, the toner on the photoreceptor unnecessary for printing can be efficiently removed. The toner can be collected, high-quality printing with less contamination can be performed, and the toner can be efficiently collected and reused.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image forming apparatus according to a first embodiment.
FIG. 2 is a configuration diagram of a control system according to the first embodiment.
FIG. 3 is a diagram illustrating a relationship between a bias voltage of each section and a toner potential.
FIG. 4 is a configuration diagram of an image forming apparatus according to a second embodiment.
FIG. 5 is a configuration diagram of a control system according to a third embodiment.
FIG. 6 is a time chart of a bias voltage of each part according to the third embodiment.
FIG. 7 is a configuration diagram of a conventional image forming apparatus.
[Explanation of symbols]
1 Photoconductor
2 Charging part
3 light source
4 Developing roller
5 Toner supply roller
7 Toner blade
8 Cleaning section
9 Toner
11 Collection roller
27 Collection roller voltage setting section
37 Recovery unit voltage setting unit

Claims (7)

A photoreceptor that rotates during image formation;
Charging means for charging the photoreceptor surface,
Exposure means for forming an electrostatic latent image on the surface of the charged photoconductor,
Developing means for developing by attaching a developer to the electrostatic latent image formed by the exposure means,
An image forming apparatus including a transfer unit configured to transfer a developer attached to the surface of the photoconductor by the developing unit to a transfer material,
An image forming apparatus comprising: a member that is disposed downstream of the developing unit and upstream of the transfer unit in a rotation direction of the photoconductor and to which an AC voltage is applied. 2. The image forming apparatus according to claim 1, wherein a DC voltage is applied corresponding to a surface potential of the photoconductor. 2. The image forming apparatus according to claim 1, further comprising a transport unit that transports the developer attached to the member to the developing unit. 2. The image forming apparatus according to claim 1, wherein the developing unit includes a developing roller adjacent to the photoconductor, and a unit configured to transfer a predetermined amount of developer adhered to the developing roller to the photoconductor. 3. The image forming apparatus according to claim 2, wherein the AC voltage applied to the member is in a range including a surface potential of the photoconductor. 6. The image forming apparatus according to claim 5, wherein the AC voltage applied to the member is in a range of a voltage applied to the developing roller adjacent to the photoconductor and a voltage applied to the charging unit. apparatus. 2. The image forming apparatus according to claim 1, wherein the frequency of the AC voltage applied to the member is approximately 1 kHz or more.

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