JP4227384B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer.
[0002]
[Prior art]
Prior art will be described. FIG. 9 shows an example of a conventional intermediate transfer belt type color image forming apparatus. Reference numeral 1 denotes a photosensitive drum as an image carrier, which is configured by applying an organic photoreceptor (OPC) or a photoconductor made of A-Si, CdS, Se or the like to the outer peripheral surface of a cored bar made of aluminum or the like. Rotate in the direction of arrow C1 at an outer peripheral speed V (hereinafter referred to as process speed). Reference numeral 3 denotes an exposure apparatus for forming a latent image on the surface of the photosensitive drum 1, and reference numeral 3a denotes an exposure position.
[0003]
60 is an intermediate transfer belt as an intermediate transfer member, such as EPDM, NBR, urethane, silicone rubber, or PI, PC, PVDF, ETFE, PET, PC / PAT, ETFE / PC, ETFE / PAT, PC / PAT. Made of resin. The intermediate transfer belt 60 is stretched on two rollers, ie, a driving roller 6b and a stretching roller 6c, which are also secondary transfer counter rollers, and the driving roller 6b is rotated by a motor (not shown) to move in the direction of the arrow C3. Driven at process speed V. Further, the intermediate transfer belt 60 is provided with a position detection member 5a that can be distinguished from the surface of the intermediate transfer belt 60 by the optical sensor 5 at one end in the circumferential direction and at an end in a direction perpendicular to the circumferential direction. Recognizes the rotational phase by detecting the position detection member 5a passing through the detection unit 5b by the optical sensor 5 (hereinafter referred to as TOP detection) and counting the time inside the main body based on the detection. it can.
[0004]
T1 is a contact portion between the photosensitive drum 1 and the intermediate transfer belt 60, that is, a primary transfer portion T1. L1 is a distance from the exposure position 3a of the photosensitive drum 1 to the primary transfer portion T1 counterclockwise, and S is a position at a distance L1 upstream from the primary transfer portion T1 on the intermediate transfer belt 60. Reference numeral 7 b denotes a primary transfer roller as a primary transfer unit provided with a conductive sponge layer on a shaft, and is in contact with the photosensitive drum 1 through an intermediate transfer belt 60.
[0005]
Reference numerals 100b and 101b are charging rollers (first charging means 100b and second charging means 101b) as charging means that are driven by the intermediate transfer belt 60 and rotate at the same peripheral speed. The peripheral lengths are 100L and 101L. It has a contact / separation mechanism (not shown) with respect to 60 and can contact at a desired time. Reference numerals 100a and 101a denote a DC voltage power source and an alternating voltage power source for applying a voltage to the charging rollers 100b and 101b, respectively. By using the driving roller 6b as a counter electrode, the charging efficiency when charging by these charging rollers 100b and 101b is increased.
[0006]
L2 and L3 are distances between the charging rollers 100b and 101b on the intermediate transfer belt 60 and the roller adjacent to the primary transfer roller 7b, respectively. It is assumed that the maximum image circumference of the image forming apparatus is Lx1.
[0007]
The image forming operation will be described below with reference to FIG. The photosensitive drum 1 is driven in the direction of the arrow C1 by a driving unit (not shown), and is uniformly charged to a predetermined potential by the charging roller 2. Exposure is started by the exposure device 3 at the timing when the TOP of the intermediate transfer belt 60 is detected, and light by a signal according to the yellow image pattern is scanned onto the photosensitive drum 1 whose surface is uniformly charged, and a latent image is obtained. Is formed.
[0008]
When the photosensitive drum 1 further rotates in the direction of arrow C1 after the latent image formation is started, the developing device 4a containing yellow toner among the developing devices 4a, 4b, 4c, and 4d supported by the support 4 is the photosensitive drum. The support 4 rotates in the direction of the arrow C2 so as to face 1 and is visualized by the negative polarity toner of the selected developing device 4a.
[0009]
In the developed toner image, when the photosensitive drum 1 further rotates in the direction of the arrow C1 and reaches the primary transfer portion T1, the high-voltage power supply 7a is used as the counter transfer electrode with the cored bar of the photosensitive drum 1 as the primary transfer roller 7b. Is applied to the intermediate transfer belt 60 by applying a positive bias. The transfer residual toner on the photosensitive drum 1 is cleaned by the photosensitive drum cleaner 13.
[0010]
After (L1 / V) has elapsed from the start of exposure, an image writing start point on the photosensitive drum 1 and a point 6S (not shown) that has passed S at the start of exposure on the intermediate transfer belt 60 are T1. Match at the position. That is, the image is formed counterclockwise on the intermediate transfer belt 60 with 6S as the leading edge.
[0011]
When the development of the yellow toner image is completed, the developing device is switched. When the time has elapsed (Lx1 / V) after the leading edge of the image reaches the developing portion and the development is completed, the support 4 rotates counterclockwise, and the developing device 4b containing the next magenta toner becomes the photosensitive drum. 1 is positioned at a position opposite to 1. Further, when the next TOP detection is performed, the same operation is repeated, and development and transfer are performed for magenta, cyan, and black colors, and toner images of a plurality of colors are formed on the intermediate transfer belt 60.
[0012]
At this time, since all the four color images are transferred with 6S as the leading edge of the image, the registration of the four color toner images is taken. When the four color toner images are transferred onto the intermediate transfer belt 60, the transfer material P is conveyed from the registration roller R in synchronization with the movement of the intermediate transfer belt 60, and has the same configuration as the primary transfer roller 7b. A secondary transfer roller 9 as a secondary transfer means contacts the intermediate transfer belt 60 via the transfer material P, and a positive bias is applied from a high voltage power supply (not shown) using the secondary transfer counter roller 6d as a counter electrode. The four color toner images on the intermediate transfer belt 60 are secondarily transferred onto the transfer material P all at once.
[0013]
The transfer material P onto which the four color toner images have been transferred is melted and fixed by a conventionally known heating and pressure fixing device 11 to obtain a color image. A monocolor image is obtained by developing and primary transferring only one color for the above process, and similarly performing secondary transfer and fixing. (Hereafter, mono color printing mode)
Next, FIG. 9 shows a cleaning process of the toner remaining on the intermediate transfer belt 60 without being transferred during the secondary transfer, that is, the secondary transfer residual toner. Here, an apparatus having two charging rollers is shown. In a conventional apparatus using only one charging roller, the secondary transfer residual toner is charged only with a positive alternating voltage, so that a toner with a small amount of charge to be held may be scattered. The toner scattering is suppressed and the charging performance is improved as described below.
[0014]
The secondary transfer residual toner is given a positive charge by a charging roller (first charging means) 100b to which a positive DC voltage is applied from a DC voltage power supply 100a. Although the charge amount of each toner particle after the charging is not uniform, charging can be performed while suppressing toner scattering.
[0015]
Subsequently, the secondary transfer residual toner is given positive charge again by the charging roller (second charging means) 101b to which a positive alternating voltage is applied from the alternating voltage power supply 101a. By this charging, the electric polarity of the toner particles maintains the positive polarity, and the charge amount of each particle is made uniform.
[0016]
Subsequently, the secondary transfer residual toner proceeds to the primary transfer portion T1, and is electrostatically transferred to the photosensitive drum by the primary transfer roller 7b to which a positive polarity bias is applied for the primary transfer of the first color of the next page. It is removed from the intermediate transfer belt 60. Then, the secondary transfer residual toner transferred to the photosensitive drum 1 is collected by the photosensitive drum cleaner 13, and the removal of the secondary transfer residual toner on the intermediate transfer belt 60 is completed.
[0017]
FIG. 10 shows the removal process of the secondary transfer residual toner between the above normal pages. In the figure, the development of the first to fourth colors is “Dev1 to 4”, the primary transfer is “Tr1-1 to 4”, the secondary transfer is “Tr2”, and the charge of the secondary transfer residual toner is “Ch2”. The recovery at the primary transfer portion is indicated by “RET”. A series of operations for forming an image, that is, a printing sequence includes a continuous image forming process in which an image forming process is repeated by repeating the above image forming process and secondary transfer residual toner removing process, and the continuous image forming process. Later, it comprises at least two strokes of a post-rotation stroke in which the intermediate transfer member is cleaned (see, for example, Patent Document 1).
[0018]
[Patent Document 1]
JP 9-44007 A (FIG. 20)
[Problems to be solved by the invention]
However, in the above conventional example, negative charge toner that could not be charged when the secondary transfer residual toner is charged adheres to the first charging unit, and further, when images are continuously formed over a plurality of pages, the adherence occurs. Toner accumulates. As the accumulation progresses, the toner falls and stains the inside of the device and the transfer material, or the adhering toner gradually lowers the charging performance of the first charging means, and the collection failure occurs due to the charging failure of the secondary transfer residual toner. The transferability of the transfer member was deteriorated and image defects were caused. This was particularly noticeable in the case where the amount of secondary transfer residual toner increases, the image printing rate is high, and in a high-temperature, high-humidity, low-humidity, low-humidity environment where the secondary transferability deteriorates.
[0019]
Therefore, an object of the present invention is to suppress problems such as image defects caused by accumulation of residual toner attached to the first charging unit.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, a typical configuration of the present invention is a toner image. Carry An image carrier; A rotatable intermediate transfer member and a toner image from the image carrier A primary transfer means for primary transfer onto the intermediate transfer member; Toner image from the intermediate transfer member Secondary transfer means for secondary transfer on the transfer material, and after secondary transfer Not transferred to transfer material Residual toner remaining on the intermediate transfer member To charge A first charging means; Arranged downstream of the first charging means in the rotational direction of the intermediate transfer member. The remaining toner Be charged A second charging means; A first voltage power source that switches and applies a DC voltage having the same polarity as the toner charging polarity and a DC voltage opposite to the toner charging polarity to the first charging means, and a toner charging polarity to the second charging means. A second voltage power supply for applying an alternating voltage of reverse polarity; A toner image is formed on the transfer material, The residual toner is transferred to the image carrier and collected. In the image forming apparatus,
When the first charging means charges the residual toner In order to retransfer the residual toner adhering to the first charging unit to the intermediate transfer member The first voltage power source applies a voltage having the same polarity as the charging polarity of the toner to the first charging means, The rotation period of the first charging unit is shorter than the rotation period of the second charging unit. It is characterized by .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the structure similar to a prior art, description is abbreviate | omitted by attaching | subjecting the same code | symbol.
[0022]
(First embodiment)
FIG. 1 is a diagram showing an example of an image forming apparatus according to the present invention, and shows a color image forming apparatus using an electrophotographic process. Reference numerals 102b and 103b denote charging rollers (first charging means 102b and second charging means 103b) as charging means, which are rotated at peripheral speeds Va and Vb, respectively, by a driving mechanism (not shown). It has a contact / separation mechanism (not shown) with respect to the intermediate transfer belt 60 as a transfer member, and can contact at a desired time. Reference numerals 102a and 103a denote a DC voltage power source and an alternating voltage power source for applying a voltage to the charging rollers 102b and 103b, respectively. The members indicated by other symbols are the same as those in FIG. There is the following relationship between Va and Vb.
[0023]
Va> Vb (1)
[0024]
FIG. 2 is a diagram showing the application timing of each bias in the post-rotation stroke as an example of the adhered toner removal stroke in the present invention. The print sequence according to the present invention employs the configuration unique to the present invention only in the image forming process and the secondary transfer residual toner removing process similar to the conventional example, and only the adhered toner removing process at the time of post-rotation. Hereinafter, the adhered toner removing process will be described with reference to FIG.
[0025]
In the charging roller 102b, after the secondary transfer residual toner is charged, the charging roller 102b is switched to the discharge bias, and the adhered toner is discharged from the entire surface of the charging roller 102b. In the charging roller 103b, an adhesion toner charging bias is applied during a time period in which the discharged toner passes through the nip. Further, the bias is continuously applied until the toner attached to the charging roller 103b is discharged by the charging of the attached toner. The collection bias is applied to the primary transfer roller 7b until the collection of the toner discharged from the charging roller 103b is completed.
[0026]
Specifically, the process speed V is 120 mm / s, the charging roller peripheral speeds Va and Vb are 200 mm / s and 150 mm / s, the charging roller peripheral length 102L is 60.0 mm, L2 and L3 are 12.0 mm and 94.2 mm. In the adhering toner removal process, the charging roller 102b discharges the secondary transfer residual toner and applies a discharge bias for a roller period (102L / Va) = 0.300s. Further, in the charging roller 103b, after L2 / V = 0.100 s from the discharge start of the charging roller 102b, application of a bias for discharging toner is started, and (discharge time) + (cycle of the charging roller 103b) = 102L × (1 / Va + 1 / Vb) = 0.700 s applied. The collection bias is applied to the primary transfer roller 7b from the end of discharge of the charging roller 103b until L3 / V = 0.785 s.
[0027]
In this configuration, the toner adhering to the charging roller 102b is ejected and ejected by bias, thereby suppressing the occurrence of image defects due to the accumulation of the adhering toner. In addition, this configuration has an advantage in that the discharge time of the toner from the charging roller 102b is shorter than the cycle of the charging roller 103b.
[0028]
Hereinafter, a description will be given with reference to FIG. FIG. 3A and FIG. 3C show the charging roller 102b when the discharge time of the toner from the charging roller 102b is longer (comparative example) and shorter (this embodiment) than the period of the charging roller 103b. 3 (b) and 3 (d) show how the discharged toner is charged by the charging roller 103b. 31 and 35 are toners before charging, 32 and 36 are charged toners, and 33 and 37 are toners that are not fully charged and adhere to the charging roller 103b. Reference numerals 34 and 38 denote nip portions between the charging roller 103 b and the intermediate transfer belt 60. H1 indicates the tip of the toner 37 attached to the charging roller 103b.
[0029]
When the discharge time of the toner from the charging roller 102b is longer than the period of the charging roller 103b, as shown in FIG. 3B, in the process of charging the toner discharged from the charging roller 102b by the charging roller 103b, In the present configuration, the adhering toner 33 obstructs charging of the uncharged toner 31 in the nip portion 34, resulting in poor recovery to the photosensitive drum as an image carrier, and further image failure. The toner discharge time from the charging roller 102b is shorter than the cycle of the charging roller 103b. For this reason, as shown in FIG. 3D, in the process of charging the toner discharged from the charging roller 102b by the charging roller 103b, the charged toner 37 is charged before the tip H1 of the adhering toner 37 enters the nip portion 38. The process ends. For this reason, all the toner discharged from the charging roller 102b can be reliably charged. Accordingly, the discharged toner can be reliably collected on the photosensitive drum, and the intermediate transfer belt can always provide high-quality printing without image defects regardless of the image printing rate and environment.
[0030]
This configuration is also advantageous because the voltage off timing of the charging roller 103b is after the toner is discharged from the charging roller 103b. Hereinafter, a description will be given with reference to FIG. FIGS. 4A, 4B, and 4C are diagrams in which voltage off timing of the charging roller 103b after the toner discharged from the charging roller 102b is charged by the charging roller 103b is divided into cases, respectively. The states before the toner adhering to the charging roller 103b enters the nip portion, when being discharged to the intermediate transfer belt through the nip portion (comparative example), and after being discharged (this embodiment) are shown.
[0031]
FIG. 4D shows the state after FIG. M1 is a charged toner, M2 is a toner that is attached without being charged, and M3 is a toner that is discharged after being attached. M5 is the toner remaining on the charging roller 103b when the voltage is turned off, and M6 is the residual toner M5 discharged. N1 indicates the toner that has passed through the nip portion when the voltage is off. N2 is the toner N1 remaining on the charging roller 103b, and N3 is the residual toner N2 discharged onto the intermediate transfer belt in the cycle of the charging roller 103b.
[0032]
As shown in FIG. 4C, when the toner adhering to the charging roller 103b passes through the nip portion, the voltage is turned off, and the toner N1 that has passed through the nip portion at that moment is N2 in FIG. As shown in FIG. 4, since the toner N3 remains on the charging roller 103b and continues to be discharged onto the intermediate transfer belt, and the discharged toner N3 is not collected on the photosensitive drum, the intermediate transfer belt is soiled and image defects are caused. appear. The residual toner M5 when the voltage is off is discharged at a time like M6 and collected on the photosensitive drum, as in M3.
[0033]
On the other hand, in this configuration, as shown in FIG. 4B, the toner attached to the charging roller 103b is discharged like M3 and then the voltage is turned off, and all the toner is collected on the photosensitive drum. Can be provided. Further, as shown in FIG. 4A, even if the toner adhering to the charging roller 103b is turned off before entering the nip portion, the adhering toner M2 is discharged and collected on the photosensitive drum. Can provide easy printing. Even when the bias is switched or separated instead of the voltage off, the same effect can be obtained by performing the timings of FIGS. 4 (a) and 4 (b). Therefore, in the present embodiment, the post-rotation is completed in the adhered toner removing process. However, the voltage applied to the charging rollers 102b and 103b and the primary transfer roller 7b is further switched to clean the intermediate transfer belt. It can also be used when the post-rotation is finished or the printing sequence is continued.
[0034]
(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 5 is a diagram showing a color image forming apparatus using an electrophotographic process as an example of the image forming apparatus according to the present invention. 104b and 105b are charging rollers (first charging means 104b and second charging means 105b) as charging means that are driven by the intermediate transfer belt 60 and rotate at the same peripheral speed. The peripheral lengths are 104L and 105L. It has a contact / separation mechanism (not shown) with respect to the belt 60 and can contact at a desired time. 104a and 105a are a DC voltage power source and an alternating voltage power source for applying a voltage to the charging rollers 104b and 105b, respectively. The members indicated by other symbols are the same as those in FIG. Note that there is the following relationship between 104L and 105L.
[0035]
105L> 104L (2)
[0036]
FIG. 6 is a diagram showing the application timing of each bias in the post-rotation stroke as an example of the adhered toner removal stroke in the present invention. The print sequence according to the present invention employs a configuration unique to the present invention as an adhering toner removal process at the time of post-rotation in addition to an image forming process and a secondary transfer residual toner removing process similar to the conventional example. Hereinafter, the adhered toner removing process will be described with reference to FIG.
[0037]
In the charging roller 104b, after the secondary transfer residual toner is charged, the charging roller 104b is switched to the discharge bias, and the adhered toner is discharged from the entire surface of the charging roller 104b. In the charging roller 105b, a bias for charging the attached toner is applied in a time zone in which the discharged toner passes through the nip. Further, the bias is continuously applied until the toner attached to the charging roller 105b is discharged by the charging of the attached toner. The collection bias is applied to the primary transfer roller 7b until the collection of the toner discharged from the charging roller 105b is completed.
[0038]
Specifically, in the process of removing the adhered toner when the process speed V is 120 mm / s, the charging roller circumferential lengths 104L and 105L are 48.0 mm, 60.0 mm, and L2 and L3 are 12.0 mm and 94.2 mm, In the charging roller 104b, after the secondary transfer residual toner is charged, a discharge bias is applied for a roller period (104L / V) = 0.400s. Further, in the charging roller 105b, application of a bias for discharging toner is started after L2 / V = 0.100 s from the discharge start of the charge roller 104b, and (discharge time) + (cycle of the charging roller 105b) = ( 104L + 105L) /V=0.900s. The collection bias is applied to the primary transfer roller 7b from the end of discharge of the charging roller 105b until L3 / V = 0.785 s.
[0039]
In this configuration, the same effect as in the first embodiment can be obtained without using a drive source for the charging roller.
[0040]
(Third embodiment)
A third embodiment of the present invention will be described. FIG. 7 is a diagram showing a color image forming apparatus using an electrophotographic process as an example of the image forming apparatus according to the present invention. Reference numerals 106b and 107b are charging rollers (first charging means 106b and second charging means 107b) as charging means that are driven by the intermediate transfer belt 60 and rotate at the same peripheral speed. The peripheral lengths are 106L and 107L. It has a contact / separation mechanism (not shown) with respect to the belt 60 and can contact at a desired time. Reference numerals 106a and 107a denote a DC voltage power source and an alternating voltage power source for applying a voltage to the charging rollers 106b and 107b, respectively. The members indicated by other symbols are the same as those in FIG. The following relationship exists between 106L and 107L.
[0041]
106L> 107L ・ ・ ・ ▲ 3 ▼
[0042]
FIG. 8 is a diagram showing the application timing of each bias in the post-rotation stroke as an example of the adhered toner removal stroke in the present invention. The printing sequence in the present invention employs a configuration unique to the present invention only in the adhered toner removal process during the post-rotation in the image forming process and secondary transfer residual toner removing process similar to the conventional example. Hereinafter, the adhered toner removing process will be described with reference to FIG.
[0043]
In the charging roller 106b, after the secondary transfer residual toner is charged, the charging roller 106b is switched to the discharge bias, and the adhered toner is discharged for a time shorter than the cycle of the charging roller 107b. In the charging roller 107b, a bias for charging the attached toner is applied during a time period when the discharged toner passes through the nip. Further, the bias is continuously applied until the toner adhering to the roller due to this charging is completely discharged. When the discharge from the charging roller 107b is completed, the adhering toner that could not be discharged at the first discharge is further discharged from the charging roller 106b. Similarly, the charging roller 107b is charged and discharged. Do it. Thereafter, the process is performed until all the toner adhering to the charging roller 106b is discharged. The collection bias is applied to the primary transfer roller 7b until all the toner is collected.
[0044]
Specifically, in the process of removing the adhered toner when the process speed V is 120 mm / s, the charging roller circumferential lengths 106L and 107L are 72.0 mm, 60.0 mm, and L2 and L3 are 12.0 mm and 94.2 mm, In the charging roller 106b, after the secondary transfer residual toner is charged, a discharge bias is applied for a half of the roller cycle (106L / (2 × V)) = 0.300s. Further, in the charging roller 107b, application of a bias for discharging toner charging is started after L2 / V = 0.100 s from the discharge start of the charging roller 106b, and (discharge time) + (cycle of the charging roller 107b) = ( 106L / 2 + 107L) /V=0.800s. Further, starting from this timing, the bias application to the charging rollers 106b and 107b is repeated in the same manner, and the remaining adhered toner is discharged and charged. The recovery bias is applied to the primary transfer roller 7b from the end of discharge of the charging roller 107b until L3 / V = 0.785 s.
[0045]
In this configuration, the same effect as in the second embodiment can be obtained regardless of the relationship between the periods of the two charging units. Here, the configuration in which the toner adhering to the first charging unit is discharged twice over the entire surface of the roller is shown, but depending on the relationship between the cycle of the first and second charging units, it may not be performed twice. In some cases, it may not be possible to eject from the entire surface of the roller. In this case, it may be divided into several times as necessary.
[0046]
Further, here, a configuration is shown in which the entire surface of the first charging unit is cleaned at the time of one post-rotation. In short, since the accumulation amount of the adhered toner may be suppressed so that a defect such as an image defect does not occur. It is not always necessary to clean the entire surface of the roller every time it rotates, and it is possible to discharge only once in one post-rotation stroke and to clean the entire roller surface in several post-rotation strokes.
[0047]
Further, here, a configuration in which the cycle of the first charging unit is longer than that of the second charging unit, i.e., a configuration in which the entire roller surface cannot be cleaned in one discharge stroke, but regardless of the cycle, as in this configuration, The discharge may be performed for a time shorter than the rotation cycle of the second charging unit from the first charging unit in one discharge stroke.
[0048]
【The invention's effect】
As described above, in the present invention, When the first charging means charges the residual toner In order to retransfer the residual toner adhering to the first charging unit to the intermediate transfer member The first voltage power source applies a voltage having the same polarity as the charging polarity of the toner to the first charging means, The rotation period of the first charging unit is shorter than the rotation period of the second charging unit. It is characterized by Therefore, it is possible to suppress problems such as image defects caused by accumulation of residual toner attached to the first charging unit.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment.
FIG. 2 is a view showing the application timing of each bias in the attached toner removing process according to the first embodiment.
FIG. 3 is a diagram showing an outline of discharge of attached toner and charging thereof in the attached toner removal process.
FIG. 4 is a diagram showing an outline regarding discharge of attached toner and voltage off timing in an attached toner removing process;
FIG. 5 is a diagram illustrating a schematic configuration of an image forming apparatus according to a second embodiment.
FIG. 6 is a diagram illustrating application timings of biases in an attached toner removing process according to a second embodiment.
FIG. 7 is a diagram illustrating a schematic configuration of an image forming apparatus according to a third embodiment.
FIG. 8 is a diagram illustrating application timings of biases in an attached toner removing process according to a third embodiment.
FIG. 9 is a diagram illustrating an example of an image forming apparatus having a conventional unit for charging residual toner.
FIG. 10 is a diagram illustrating application timing of each bias in a conventional inter-page process.
[Explanation of symbols]
P: transfer material, R: registration roller, T1: primary transfer part, V: process speed,
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging roller, 3 ... Exposure apparatus, 3a ... Exposure position,
4 ... support, 4a ... developing device, 4b ... developing device, 4c ... developing device,
4d: developing device, 5: optical sensor, 5a: position detecting member,
5b: detecting unit, 6b: driving roller, 6c: stretching roller,
6d: secondary transfer counter roller, 7a: high voltage power supply, 7b: primary transfer roller,
9 ... Secondary transfer roller, 11 ... Fixing device, 13 ... Photosensitive drum cleaner,
31 ... Uncharged toner, 32 ... Charged toner, 33 ... Adhering toner,
34 ... Nip part, 35 ... Uncharged toner, 36 ... Charged toner, 37 ... Adhering toner,
38 ... nip part, 60 ... intermediate transfer belt,
102a ... DC voltage power supply, 102b ... charging roller,
103a ... alternating voltage power supply, 103b ... charging roller,
104a: DC voltage power supply, 104b: charging roller,
105a ... alternating voltage power supply, 105b ... charging roller,
106a ... DC voltage power supply, 106b ... charging roller,
107a: alternating voltage power source, 107b: charging roller,

Claims (4)

An image carrier for carrying a toner image, a rotatable intermediate transfer member, a primary transfer means for primarily transferring the toner image from the image carrier onto the intermediate transfer member, and a toner image for the intermediate transfer member a first charging means for charging the secondary transfer means for secondarily transferred onto the transfer material, the remaining residual toner on said intermediate transfer member without being transferred to the transfer material after the secondary transfer from the first charge A second charging unit disposed on the downstream side of the rotation direction of the intermediate transfer body relative to the unit and charging the residual toner; a DC voltage of the same polarity as the toner charging polarity and a charging polarity of the toner opposite to the first charging unit; A first voltage power source that switches and applies a DC voltage of polarity; and a second voltage power source that applies an alternating voltage having a polarity opposite to the charging polarity of the toner to the second charging means, and transfers a toner image. It is formed on the wood, and transferring the residual toner on the image bearing member In the image forming apparatus to yield,
When the first charging unit charges the residual toner, the first voltage power source is applied to the first charging unit in order to retransfer the residual toner attached to the first charging unit to the intermediate transfer member. Apply a voltage with the same polarity as the charging polarity of the toner,
The image forming apparatus according to claim 1, wherein a rotation period of the first charging unit is shorter than a rotation period of the second charging unit. The image forming apparatus according to claim 1.
2. An image forming apparatus according to claim 1, wherein a peripheral speed of the first charging unit is faster than a peripheral speed of the second charging unit. The image forming apparatus according to claim 1 or 2,
The image forming apparatus according to claim 1, wherein a circumference of the first charging unit is shorter than a circumference of the second charging unit. An image carrier for carrying a toner image, a rotatable intermediate transfer member, a primary transfer means for primarily transferring the toner image from the image carrier onto the intermediate transfer member, and a toner image for the intermediate transfer member a first charging means for charging the secondary transfer means for secondarily transferred onto the transfer material, the remaining residual toner on said intermediate transfer member without being transferred to the transfer material after the secondary transfer from the first charge A second charging unit disposed on the downstream side of the rotation direction of the intermediate transfer body relative to the unit and charging the residual toner; a DC voltage of the same polarity as the toner charging polarity and a charging polarity of the toner opposite to the first charging unit; A first voltage power source that switches and applies a DC voltage of polarity; and a second voltage power source that applies an alternating voltage having a polarity opposite to the charging polarity of the toner to the second charging means, and transfers a toner image. It is formed on the wood, and transferring the residual toner on the image bearing member In the image forming apparatus to yield,
When the first charging unit charges the residual toner, the first voltage power source is applied to the first charging unit in order to retransfer the residual toner attached to the first charging unit to the intermediate transfer member. Apply a voltage with the same polarity as the charging polarity of the toner,
2. An image forming apparatus according to claim 1, wherein said first voltage power source applies a voltage having the same polarity as the toner charging polarity to said first charging means shorter than a rotation period of said second charging means.

Images