JP2007233049A - Image forming apparatus and drum cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a drum-cleaning method, that is superior in the removal of discharge products on a photoreceptor. <P>SOLUTION: The image forming apparatus is equipped with a developing device which develops a latent image on a photoreceptor drum with two or more kinds of toner and forcibly discharges the two or more kinds of toner onto the photoreceptor drum during refresh processing; a transfer roller which transfers the developed latent image to an intermediate transfer belt, cancels the transfer of a kind of toner from among the two or more kinds of toner forcibly discharged during the refresh processing to the intermediate transfer belt, and transfers the other kinds of toners to the intermediate transfer belt; and a drum cleaning unit which cleans the photoreceptor drum. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to an image forming apparatus having an improved cleaning force for a photosensitive drum.

  In recent years, due to the increase in environmental awareness, contact charging means that generate less corona discharge products such as ozone have been used in many cases, and among them, the charging roller system is particularly used.

  However, since the distance between the charging roller and the photosensitive drum is very close, the energy is large and the adhesion force of the discharge product (mainly nitrogen oxide) to the photosensitive member surface is increased. The discharge product adhering to the surface of the photosensitive drum lowers the electrical resistance of the photosensitive member and causes image flow in a high temperature and high humidity environment, or increases the frictional force between the photosensitive drum and the cleaning blade. This causes toner to slip through, squeal, turn over, etc. in the cleaning blade.

  The magnitude of such adverse effects due to the adhesion of discharge products is larger in the charging roller method than in the corona charging method, and the charging roller in which the AC voltage is superimposed on the DC voltage is more than the charging roller in which only the DC voltage is applied. Is also big. In addition, the magnitude of the adverse effect due to the adhesion of the discharge product becomes more prominent when using a photoconductor in which the photosensitive layer is not easily scraped, such as an amorphous silicon photoconductor.

  Measures to maintain the image quality by eliminating the influence of discharge products include methods of disassembling and invalidating discharge products on the photoconductor, methods of heating the photoconductor, brush shape, roller shape, web shape, etc. A method of controlling the amount of wear on the surface of the photoreceptor using a rubbing means is disclosed. A method of adding abrasive particles to the toner and rubbing the surface of the photoreceptor with the toner is also an effective means for removing the discharge products adhering to the surface of the photoreceptor.

  On the other hand, in Japanese Patent Application Laid-Open No. 2005-316085 and the like, if the average print rate of the toner image is less than a specified value, it is determined that the deteriorated toner is increasing in the developing device, and the toner in the developing device is not developed. A forcible discharge, that is, a refresh operation is disclosed.

Japanese Patent Application Laid-Open No. 2005-156929 and Japanese Patent Application Laid-Open No. 2005-134976 also provide means for forcibly consuming toner in the developing device such as drum refresh and developer refresh on the photoreceptor.
JP 2005-316085 A JP 2005-156929 A Japanese Patent Laid-Open No. 2005-134776

  By the way, when the toner image in the developing device is forcibly discharged during non-development when the average print ratio of the toner image is less than the specified value, the surface of the photoconductor is rubbed with the forcibly discharged toner and adhered to the surface of the photoconductor. It is possible to remove the generated discharge product. However, since the polishing ability of toners of each color of yellow (Y), magenta (M), cyan (C), and black (K) is different, if the surface of the photoreceptor is rubbed in a mixed state of these toners, the polishing effect The polishing effect becomes weaker than when the surface of the photoreceptor is rubbed only with a high toner (for example, black toner has many abrasive particles and strong polishing power).

  The present invention has been made to solve the above-described problems, and eliminates adverse effects on images caused by discharge products adhering to the surface of a photosensitive drum, and can provide a good image in the long term. An object is to provide an image forming apparatus and the like.

  The present invention employs the following means in order to achieve the above object. That is, an image forming apparatus according to the present invention develops a latent image on a photosensitive drum with a plurality of types of toner, and develops a developer that forcibly discharges the plurality of types of toner onto the photosensitive drum during a refresh process. The latent image is transferred to the intermediate transfer belt, and among the plurality of types of toner forcibly discharged during the refresh process, the transfer to the intermediate transfer belt is canceled for one toner type, and the intermediate transfer is performed for the other toner types. A transfer roller for transferring to the belt and a drum cleaning unit for cleaning the photosensitive drum are provided.

  In this configuration, when the toner remaining on the photosensitive drum is removed, the discharge product attached to the photosensitive drum is removed by rubbing the photosensitive drum with the cleaning roller and the cleaning blade through the toner. Done. Further, since the surface of the photosensitive drum is not rubbed in the mixed state of the toners of different colors with different polishing capabilities, but the surface of the photosensitive drum is rubbed only with the toner having a strong polishing power, efficient removal with sufficient polishing power becomes possible.

  Also, during the refresh process, a transfer signal for instructing transfer of the forcibly discharged toner to the intermediate transfer belt and a cancel signal for instructing cancel of transfer are transferred for each toner type forcibly discharged by the developing device. There is a configuration to transmit to the roller.

  In this configuration, since a plurality of toners having the same polishing power can be selectively used, more efficient removal is possible.

  Further, the transfer roller has a configuration for controlling application of a reverse transfer bias for transferring the toner in the direction of the photosensitive drum for each toner type forcibly discharged by the developing device.

  In this configuration, since the reverse transfer bias is applied only to the predetermined removed toner, transfer of the discharged toner to the intermediate transfer belt is suppressed, and efficient removal is possible.

  There is also a configuration in which the transfer roller is controlled to be pressed and separated from the photosensitive drum for each toner type forcibly discharged by the developing device.

  Even in this configuration, transfer of the discharged toner to the intermediate transfer belt is suppressed according to the toner type, and thus efficient removal is possible.

  One toner type is black toner. By using the black toner for removal, it is possible to suppress the influence of the tint on the output image by the abrasive.

  Further, at the time of the refresh process, there is a configuration in which the toner forcedly discharged from the developing device by the developing bias in the direction of the photosensitive drum is attached to the photosensitive drum without charging the photosensitive drum.

  Thereby, generation | occurrence | production of an unnecessary discharge product can be suppressed and it can contribute to the removal of a discharge product as a result.

  Rather than rubbing the surface of the photosensitive drum in a mixed state of toners having different polishing capabilities, the surface of the photosensitive drum is rubbed only with toner having a strong polishing power, so that efficient removal with sufficient polishing power becomes possible.

  In addition, since a reverse transfer bias for transferring the toner in the direction of the photosensitive drum is applied, transfer of the discharged toner to the intermediate transfer belt is suppressed, so that efficient removal is possible.

  In addition, for each toner type that is forcibly discharged by the developing device, the transfer roller is controlled to be pressed and separated from the photosensitive drum, so that transfer of discharged toner to the intermediate transfer belt is suppressed according to the toner type. This makes it possible to remove the water.

  In the configuration in which one toner type is black toner, the influence of color on the output image by the abrasive can be suppressed by using the black toner for removal.

  In addition, during the refresh process, toner that is forcibly discharged from the developing device by the developing bias in the direction of the photosensitive drum is attached to the photosensitive drum without charging the photosensitive drum, thereby suppressing generation of unnecessary discharge products. As a result, it can contribute to the removal of discharge products.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: It is not the thing of the character which limits the technical scope of this invention.

  FIG. 1 is a schematic diagram of the image forming apparatus 101. However, details of each part not directly related to the present invention are omitted. Specifically, the image forming apparatus 101 corresponds to a digital copying machine or a printer. Here, a color printer will be described as an example.

(Image formation processing)
First, image forming processing in the image forming apparatus 101 will be described with reference to FIGS. When the image forming apparatus 101 is turned on, a counter (N) for counting the number of printed sheets is initialized by the print control unit 401 shown in FIG. 4 (FIG. 5: S501). At this time, other various parameters, temperature sensing of the heating roller 108a in the fixing device 108, and the like are also performed. When various initializations are completed and the temperature of the heating roller 108a rises to a predetermined value or more, the following image forming process can be performed (FIG. 5: S502).

  That is, in this state, when image data is input from a computer (not shown) or the like, first, the photosensitive drum 102 is charged by the charging roller 109. When the photosensitive drum 102 is charged, the laser unit 104 forms a latent image on the photosensitive drum 102 based on the image data. The laser is bent by the reflecting mirror 110 according to the position of the laser unit 104.

  When a latent image is formed on the photosensitive drum 102 by the laser unit 104, a rotating drum type developing device (rotary developing device) 103 is rotated in a direction perpendicular to the drawing as shown in FIG. The developing unit 111 that is rotated in the circumferential direction 103b around the shaft 103a and stores the corresponding color toner is disposed at a position facing the photosensitive drum 102. In this state, the latent image on the photosensitive drum 102 is developed with toner stored in the developing unit, and transferred to the intermediate transfer belt 107 by the transfer roller 120. The rotary drum type developing device 103 includes four developing units 111 (Y), (C), (M), and (K) that store a plurality of toner types, that is, yellow, cyan, magenta, and black toners, respectively. have. The four developing units 111 have substantially the same configuration except that the positions of the opening units at the time of toner supply are different.

  By repeating the transfer to the intermediate transfer belt 107 for each color, a full color image is formed on the intermediate transfer belt.

  Note that untransferred toner and the like remaining on the photosensitive drum 102 after being transferred to the intermediate transfer belt 107 by the transfer roller 120 are removed by the cleaning roller 201 and the cleaning blade 202 constituting the drum cleaning unit 122, and are not shown. It is collected in a waste toner box.

  In synchronization with the transfer to the intermediate transfer belt 107, the paper taken out from the paper feed cassette 113 through the paper feed unit 114 is conveyed to the registration roller pair 116 through the conveyance path 115. Thereafter, the sheet is conveyed from the registration roller pair 116 to the intermediate transfer belt 107 in time with the developed image on the intermediate transfer belt 107 and guided to the secondary transfer roller 117.

  The secondary transfer roller 117 is configured to be capable of being pressed against and separated from the intermediate transfer belt 107, and is pressed against the intermediate transfer belt 107 after a full-color developed image is formed on the intermediate transfer belt 107. At the time of press contact, the developed image formed on the intermediate transfer belt 107 is transferred onto the sheet by the transfer bias applied to the secondary transfer roller 117.

  The sheet on which the developed image is transferred is guided to the fixing device 108 via the conveyance path 118, and the developed image is fixed on the sheet by the heating roller 108a and the pressure roller 108b. Thereafter, the sheet is discharged to the discharge unit 119.

  When the transfer of the developed image onto the paper is completed, the intermediate transfer belt 107 is cleaned by the cleaning unit 121. That is, when the intermediate transfer belt 107 is guided between the driving roller 123 and the conductive brush roller 124, the charged toner, that is, toner particles and external additives are applied to the cleaning bias in the direction of the conductive brush roller 124 and the conductive brush roller 124. As a result, the toner is electrically and physically removed from the intermediate transfer belt 107 and transferred to the conductive brush roller 124. The toner transferred to the conductive brush roller 124 is physically and electrically transferred to the recovery roller 125 by the biting of the conductive brush roller 124 into the recovery roller 125 and the cleaning bias.

  The toner adhering to the surface of the collection roller 125 is scraped off by a rubber blade, collected by a rotating body having a spiral shape provided on the back surface of the fixed member, and collected in a waste toner box.

  Through the above processing, the toner remaining on the surface of the intermediate transfer belt 107 is removed and collected.

  The above is the main image forming process in the image forming of the image forming apparatus 101 controlled by the print control unit 401 shown in the schematic functional block diagram of FIG. When the printing of one sheet is completed, the print control unit 401 increments the value of the counter N by 1.

  In the image forming apparatus 101, as shown in the schematic configuration diagram of FIG. 3, a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, an HDD (Hard Disk Drive). 304 and a driver 305 corresponding to each drive unit in the printing process are connected via an internal bus 306. The CPU 301 uses, for example, the RAM 302 as a work area, executes a program stored in the ROM 303, the HDD 304, and the like, and exchanges data and commands with the driver 305 based on the execution result, thereby printing control unit 401. As described above, the operation of each driving unit 307 shown in FIG. 1 is controlled.

(Refresh processing)
Next, operations of the cleaning control unit 402 and each driving unit 307 related to the refresh process will be described in detail. Here, the refresh process is a process for forcibly discharging the deteriorated toner increased in the developing unit without transferring it to the paper.

  First, when the above-described series of image forming processes (for one sheet) is completed, a message to that effect is transmitted from the print control unit 401 to the cleaning control unit 402. The cleaning control unit 402 that has received the signal indicating that the printing process has ended performs a refresh process determination following the printing process.

  In the above determination, the cleaning control unit 402 acquires the value of the counter N from the print control unit 401. The counter N indicates the number of sheets printed since the previous refresh process.

  The cleaning control unit 402 compares the value of the counter N with T serving as a threshold for shifting to the refresh process (FIG. 5: S503). T is a numerical value that varies depending on the performance of the image forming apparatus 101 and the like, and a small value is provided for T in a model that requires frequent refresh processing.

  If N ≧ T is not satisfied, the continuous printing process is repeated again (FIG. 5: S503 NO → S502).

  If N ≧ T, the cleaning control unit 402 performs a refresh process (FIG. 5: S503 YES).

  In the refresh process, first, the cleaning control unit 402 calculates an average printing rate A for each of the toners (Y) (M) (C) (K). The average printing rate can be calculated by obtaining the printing amount for the number of sheets determined by the above T for each toner from the printing rate printing control unit 401. Here, when the average printing rate A is smaller than a predetermined printing rate threshold B, it means that there is deteriorated toner in the developing device. For this reason, the cleaning control unit 402 discharges an amount of toner corresponding to ((printing rate threshold (B) −average printing rate (A)) × predetermined number (T)) to the developing device 103. A signal is transmitted (FIG. 5: S506). When discharging, the cleaning control unit 402 performs control so that the surface of the photosensitive drum 102 is not charged. As a result, the amount of discharged toner can be controlled by the application time of the developing bias from the developing unit 103 to the photosensitive drum 102.

  The toner is discharged for each toner (Y) (M) (C) (K). When each toner is discharged, the cleaning control unit 402 determines the discharged toner (FIG. 5: S507).

  When the discharged toner is not a predetermined toner (here, black), the cleaning control unit 402 transfers the toner on the photosensitive drum 103 to the intermediate transfer belt 107 with respect to the transfer roller 120. A signal to that effect is transmitted (FIG. 5: S507 NO → S508). Further, the secondary transfer roller 117 is separated from the intermediate transfer belt 107 and transmits a signal not to apply a transfer bias to the sheet. Further, a signal for cleaning the intermediate transfer belt 107 is transmitted to the cleaning unit 121.

  With the above processing, for toner other than black, the toner forcibly discharged onto the photosensitive drum 103 is cleaned by the cleaning unit 121 via the intermediate transfer belt 107.

  If the discharged toner is a predetermined black toner, the cleaning control unit 402 transmits a signal to the transfer roller 120 to apply a reverse transfer bias for transferring the toner in the direction of the photosensitive drum. (FIG. 5: S507 YES → S509). Based on the signal, the transfer roller 120 applies the reverse transfer bias.

  By the above processing, only the black toner, the toner forcibly discharged onto the photosensitive drum 103 is not transferred to the intermediate transfer belt 107, that is, the transfer is canceled and removed by the drum cleaning unit 122. Note that by selectively canceling the transfer in this way, for example, a plurality of toners such as black toner and yellow toner can be selected for polishing. That is, by selecting a plurality of toners having the same polishing power, efficient removal can be performed without reducing polishing efficiency.

  The cleaning control unit 402 confirms that the refresh process has been performed for all the toner types, resets the counter (N), and then returns the process to the print control unit 401 (FIG. 5: S510 YES → S501). . Thereafter, if there is a print output command, the image forming process is started (FIG. 5: S502).

  As described above, when the toner remaining on the photosensitive drum 102 is removed by the cleaning roller 201 and the cleaning blade 202, the cleaning roller 201 and the cleaning blade 202 rub the photosensitive drum 102 through the toner. Then, the discharge product adhering to the photosensitive drum 102 is removed.

  In addition, since the surface of the photosensitive drum is not rubbed in a mixed state of toners of different colors, the surface of the photosensitive drum is rubbed only with a toner having a strong polishing power, so that efficient removal with sufficient polishing power is possible.

  In the refresh process, a method of forming a developed image by the developing unit 103 after forming a latent image on the photosensitive drum 102 can also be used. However, the discharge product is also adhered during the formation of the latent image. It is preferable to discharge the toner without forming a latent image because it proceeds.

  Further, as a means for preventing the toner image on the photosensitive drum 103 from being transferred to the intermediate transfer belt 107, it is also possible to simply apply no voltage to the transfer roller 120. However, from the viewpoint of not transferring more toner, it is more effective to apply a voltage (reverse transfer bias) having a polarity opposite to that during normal image formation to the intermediate transfer belt 107 as described above. Further, when the transfer roller can be pressed against and separated from the photosensitive drum 102, the transfer roller may be separated from the photosensitive drum based on a signal indicating a refresh process.

  Furthermore, in order to rub the surface of the photosensitive drum 102 with the toner remaining on the photosensitive drum 102, only the cleaning blade 202 may be used, but the method of rubbing with the cleaning roller 201 and the cleaning blade 202 as described above is more suitable. Further, it is possible to more effectively remove the discharge product adhering to the surface of the photosensitive drum 102.

  Further, the toner that rubs the surface of the photosensitive drum 102 during the refresh process is not limited to black, and at least one of yellow, cyan, and magenta may be used. At this time, it is more effective for removing discharge products that the toner to be used contains abrasive particles such as titanium oxide, strontium titanate, cerium oxide, aluminum oxide, and zinc oxide.

  The toner suitable for the removal is preferably a toner having a circularity of 0.950 or less or added with abrasive fine particles.

Circularity a is a = L0 / L
L0: Perimeter length of a circle having the same projected area as the particle image L: Perimeter length of the projected image of the particle

  The toner suitable for removal preferably has a volume average particle diameter in the range of 4 to 10 μm, particularly 5 to 9 μm.

  Furthermore, the additive amount and particle size of the externally added abrasive are preferably from 0.1 to 3.0% by mass, particularly from 1.0 to 2.0% by mass, based on the toner weight. The volume average particle diameter is preferably in the range of 0.01 to 0.7 μm, particularly 0.1 to 0.4 μm.

  Still further, the photosensitive part constituting the photosensitive drum is preferably an amorphous silicon photosensitive member.

(Example)
The implementation conditions and results when the refresh process is actually performed are shown below. In consideration of the color change of the color image due to the addition of the abrasive to the toner, a part of titanium oxide is added as an abrasive to the black toner that is least affected by the addition of the abrasive. The color toner was used without adding an abrasive. In addition, a total of 10,000 color images were formed with a printing rate of 2% for each color. After the formation of 10,000 color images, image fogging, image flow, and cleaning blade noise were evaluated.

<Evaluation criteria>
-Image fog A color image was printed in a normal temperature and humidity environment of 23 ° C. and 50%, and the print state was visually evaluated in three ranks.

    Rank A: Fog is hardly observed in the background portion.

    Rank B: An acceptable level with a slight fog in the background.

    Rank C: Background fog is terrible.

-Image flow A character image was printed after being left in a high-temperature and high-humidity environment of 30 ° C and 85% for 12 hours, and the printed state was visually evaluated in three ranks.

    Rank A: Little character flow is observed.

    Rank B: An acceptable level with a slight character flow.

    Rank C: The character flow is bad.

-Cleaning blade squealing Each of the cleaning blades was allowed to stand for 12 hours in a normal temperature and humidity environment of 23 ° C and 50%, and a low temperature and low humidity environment of 10 ° C and 15%. A color image was printed continuously for 10 sheets, and whether or not abnormal noise was generated at the cleaning blade during printing was evaluated in three ranks.

    Rank A: No abnormal noise occurs in either environment.

    Rank B: Abnormal noise is generated in a low temperature and low humidity environment.

    Rank C: Abnormal noise is generated in a room temperature and humidity environment.

  As a comprehensive evaluation, fog, image flow, and blade crying were all rated as ◯, both ranked A or B as Δ, and at least one as C as x.

  FIG. 6 shows the conditions and results of the refresh process.

<Conditions for implementation>
Implementation condition 1
The predetermined number of sheets (T) to be refreshed is 100 sheets, and the printing rate threshold (B) is 3%. In the refresh process, a reverse transfer bias was applied to the primary transfer roller only during black toner image formation.

Implementation condition 2
The predetermined number (T) for performing the refresh process was 50. Other conditions are the same as Condition 1.

Implementation condition 3
The printing rate threshold (B) was set to 3.5%. Other conditions are the same as Condition 1.

Implementation condition 4
No reverse transfer bias is applied to the transfer roller during black toner image formation. Other conditions are the same as Condition 1.

Comparison condition 1
During the refresh process using black toner, a transfer bias having the same polarity as that during normal image formation was applied to the transfer roller. Other conditions are the same as Condition 1.

Comparison condition 2
The refresh process is not performed.

<Result>
-From the comparison condition 2 and other comparisons, it was confirmed that the image fog can be suppressed by performing the refresh process.

  -According to the comparison with the implementation condition 4 and other, it was possible to suppress the occurrence of image flow and crying of the cleaning blade by not performing the transfer at the time of the refresh process with the black toner having a high polishing power. In particular, by applying a reverse transfer bias to the transfer roller, it was possible to improve the level of suppression of the occurrence of image flow and crying of the cleaning blade.

  -From the implementation condition 2 and other comparisons, it was confirmed that increasing the frequency of the refresh process is more effective in suppressing fogging, image flow, and cleaning blade crying.

  -From the comparison with the execution condition 3, it was confirmed that setting the printing rate threshold value higher is more effective in suppressing fogging, image flow, and cleaning blade crying.

  The image forming apparatus according to the present invention is useful as an image forming apparatus capable of stably outputting a good image output over a long period of time because it is excellent in removing discharge products from the photoreceptor.

1 is a schematic diagram of an image forming apparatus according to the present invention. Schematic which shows the structure of the drum cleaning unit vicinity. 1 is a schematic configuration diagram of an image forming apparatus. 1 is a schematic functional block diagram of an image forming apparatus. The flowchart of a printing process and a refresh process. The figure which shows the conditions and result of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Image forming apparatus 102 Photosensitive drum 103 Rotating drum type developing device 103a Central axis 103b Circumferential direction 104 Laser unit 105 Toner storage unit stage 106 Toner supply unit 107 Intermediate transfer belt 108 Fixing device 109 Charging roller 110 Reflection mirror 111 Development unit 113 Supply Paper cassette 114 Paper feed unit 115, 118 Conveying path 116 Registration roller pair 117 Secondary transfer roller 119 Ejection unit 120 Transfer roller 121 Cleaning unit 122 Drum cleaning unit 123 Drive roller 124 Conductive brush roller 201 Cleaning roller 202 Cleaning blade 401 Print control unit 402 Cleaning control unit

Claims (10)

A developing unit that develops the latent image on the photosensitive drum with a plurality of types of toner and forcibly discharges the plurality of types of toner onto the photosensitive drum during a refresh process;
The developed latent image is transferred to the intermediate transfer belt, and among the plurality of types of toner forcibly discharged during the refresh process, the transfer to the intermediate transfer belt is canceled for one toner type, and the other toner types are canceled. Is a transfer roller for transferring to the intermediate transfer belt;
A drum cleaning unit for cleaning the photosensitive drum;
An image forming apparatus.   At the time of the refresh process, a transfer signal for instructing transfer of the forcibly discharged toner to the intermediate transfer belt and a cancel signal for instructing cancel of transfer for each toner type forcibly discharged by the developer. The image forming apparatus according to claim 1, further comprising a cleaning control unit that transmits to the transfer roller.   The image forming apparatus according to claim 1, wherein the transfer roller switches application of a reverse transfer bias for transferring the toner in the direction of the photosensitive drum for each toner type forcibly discharged by the developing device.   4. The image forming apparatus according to claim 1, wherein the transfer roller is capable of being pressed and separated from the photosensitive drum and controls the pressure and separated from the photosensitive drum for each toner type forcibly discharged by the developing device. .   The image forming apparatus according to claim 1, wherein the one toner type is a black toner, and the other toner type is a cyan toner, a magenta toner, and a yellow toner.   2. The image forming apparatus according to claim 1, wherein during the refresh process, the toner that is forcibly discharged from the developing device by a developing bias in the direction of the photosensitive drum is attached to the photosensitive drum without charging the photosensitive drum.   The image forming apparatus according to claim 1, wherein the one toner type is a toner having a circularity of 0.950 or less or a fine particle added.   The image forming apparatus according to claim 7, wherein the abrasive fine particles are one or more selected from titanium oxide, aluminum oxide, and zinc oxide.   The image forming apparatus according to claim 1, wherein the photosensitive portion configuring the photosensitive drum is configured by an amorphous silicon photosensitive member. Forcibly discharging the plurality of types of toner onto the photosensitive drum during the refresh process;
A step of canceling transfer to the intermediate transfer belt for one toner type among a plurality of types of toner forcibly discharged during the refresh process, and transferring to the intermediate transfer belt for the other toner types;
Cleaning the photosensitive drum for each toner type;
A drum cleaning method comprising:

Images