JP2017122850A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that, according to a change in electric resistance of a cleaning member electrostatically removing a toner on an intermediate transfer body, can adjust a bias applied to the cleaning member to a necessary and sufficient value.SOLUTION: The image forming apparatus comprises control means that adjusts a cleaning bias applied from power supplies 50 and 60 to cleaning members 31 and 32 for removing a toner on an intermediate transfer body 20. The control means causes the cleaning members 31 and 32 to remove a predetermined toner image formed on the intermediate transfer body 20, acquires information on the amount of toner in the predetermined toner image removed by the cleaning members 31 and 32 from a result of detection performed by detection means, and adjusts the cleaning bias on the basis of the information so that the amount of toner in the predetermined toner image removed by the cleaning members 31 and 32 becomes close to a predetermined reference value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system or an electrostatic recording system, and more particularly to an intermediate transfer type image forming apparatus.

  Conventionally, as an image forming apparatus using an electrophotographic system or an electrostatic recording system, an intermediate transfer type image forming apparatus is known. In this image forming apparatus, after the toner image is secondarily transferred from the intermediate transfer member to the recording material, the toner remains on the intermediate transfer member. The toner remaining on the intermediate transfer member (secondary transfer residual toner) is removed from the intermediate transfer member by the intermediate transfer member cleaning unit and collected.

  Patent Document 1 proposes to provide a toner charging unit that charges the secondary transfer residual toner on the intermediate transfer member with a polarity opposite to the normal charging polarity of the toner as an intermediate transfer member cleaning unit. In this case, the secondary transfer residual toner is electrostatically charged from the intermediate transfer member to the photosensitive member in the primary transfer portion of the image forming portion immediately after that by being charged with a polarity opposite to the normal charging polarity of the toner. It is transferred and collected by the photoconductor cleaning means.

  Japanese Patent Application Laid-Open No. H10-228561 proposes providing a temporary collection member that electrostatically and temporarily collects secondary transfer residual toner as an intermediate transfer member cleaning unit. The secondary transfer residual toner recovered on the temporary recovery member is discharged to the intermediate transfer member in a post-rotation process after the image forming process. Then, the discharged toner is electrostatically transferred from the intermediate transfer member to the photosensitive member in the primary transfer portion of the image forming unit immediately thereafter, and is collected by the photosensitive member cleaning unit.

  Here, a method of electrostatically cleaning the toner on the intermediate transfer member using an electrostatic cleaning unit such as a toner charging unit or a temporary recovery member is referred to as an “electrostatic cleaning method”.

Japanese Patent No. 3267507 JP 09-197750 A

  However, it has been found that the electrostatic cleaning method has the following problems. The toner charging unit will be described as an example.

  As the toner charging means, a toner charging member such as a conductive rubber roller or brush is used. In such a toner charging member, the electrical resistance of the toner charging member increases as the number of printed sheets increases. Therefore, in order to flow a desired current through the toner charging member, it may be necessary to increase the value of the bias applied to the toner charging member. Also, when the toner charging member deteriorates due to deterioration of the rubber or resin constituting the toner charging member, or due to the discharge product or toner adhering to the toner charging member, the portion where the electrical resistance is relatively low on the toner charging member. And mottled spots. Even when the same current as before the deterioration is supplied to the toner charging member, the current concentrates at a location where the electrical resistance is relatively low, and the current does not easily flow at a high location. As a result, the charge amount of the toner that has passed through the position corresponding to the portion having a relatively high electrical resistance of the toner charging member becomes small, and cleaning failure may occur. Therefore, as the electric resistance of the toner charging member increases, it is necessary to increase the target value of the current flowing through the toner charging member so that a sufficient current flows also in a portion having a relatively high electric resistance. is there.

  However, if the bias value applied to the toner charging member is increased unnecessarily or the target value of the current flowing through the toner charging member is increased, the deterioration of the toner charging member is promoted and the increase in electrical resistance is accelerated. Will do. Also, if the electrical resistance of the toner charging member continues to increase and the bias value applied to the toner charging member reaches the upper limit output of the high voltage power source, the desired current cannot flow thereafter, and the toner is not sufficiently charged. As a result, a cleaning failure may occur. For this reason, the increase in the electrical resistance of the toner charging member prevents a desired current from flowing through the toner charging member and the occurrence of a cleaning failure is a limitation on the product life, which is a problem from the viewpoint of extending the life.

  Here, as a countermeasure for the above problem, it is conceivable to increase the performance of the high-voltage power supply and increase the upper limit output. However, in this case, a transformer having a high output withstand voltage is required, which may cause problems such as an increase in circuit area of the electric substrate and an increase in cost.

  The toner charging member has been described above as an example, but the temporary recovery member has the same problem as described above.

  Therefore, an object of the present invention is to adjust the bias applied to the cleaning member to a necessary and sufficient value in accordance with a change in electric resistance of the cleaning member that electrostatically cleans the toner on the intermediate transfer member. An image forming apparatus is provided.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to an image carrier that carries a toner image, a toner image forming unit that forms a toner image on the image carrier, and a toner that is primarily transferred from the image carrier in a primary transfer portion. A rotatable intermediate transfer member transported for secondary transfer of the image to the recording material at the secondary transfer unit; and downstream of the secondary transfer unit and upstream of the primary transfer unit in the rotational direction of the intermediate transfer member. A cleaning member that contacts the intermediate transfer member and cleans the toner on the intermediate transfer member; a power source that applies a bias to the cleaning member; a detection unit that detects toner on the intermediate transfer member; Control means for adjusting a cleaning bias applied to the cleaning member to clean the toner on the intermediate transfer body, and the control means is formed on the intermediate transfer body. A predetermined toner image is cleaned by the cleaning member, and information on the amount of toner of the predetermined toner image cleaned by the cleaning member is detected by the detection unit to detect the toner of the predetermined toner image on the intermediate transfer member. And the cleaning bias is adjusted so that the amount of toner of the predetermined toner image cleaned by the cleaning member approaches a predetermined reference value based on the information. It is.

  According to the present invention, the bias applied to the cleaning member can be adjusted to a necessary and sufficient value in accordance with the change in the electrical resistance of the cleaning member that electrostatically cleans the toner on the intermediate transfer member.

1 is a schematic sectional view of an image forming apparatus. It is a schematic diagram of a belt cleaning device. FIG. 6 is a graph showing a relationship between a current value flowing through a conductive brush and a toner recovery amount. It is a graph which shows the current voltage characteristic and cleaning performance of a charging roller. It is a schematic diagram of an optical sensor. FIG. 6 is a graph showing the relationship between the output of an optical sensor and the amount of applied toner. It is a schematic diagram which shows the image pattern for a calibration. It is a flowchart figure of adjustment operation. 6 is a graph illustrating an example of toner detection results in an adjustment operation. FIG. It is a graph showing another example of the toner detection result in the adjustment operation. It is a flowchart figure of lifetime detection control. It is a graph for demonstrating the judgment method of the lifetime of an electroconductive brush. It is a graph for demonstrating the determination method of the lifetime of a charging roller.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

[Example 1]
1. Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a schematic sectional view of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 according to the present exemplary embodiment is a laser beam printer that employs an inline method or an intermediate transfer method that can form a full-color image using an electrophotographic method.

  The image forming apparatus 100 includes first, second, third, and fourth image forming units 1a, 1b, 1c, and 1d as a plurality of image forming units (stations). The first, second, third, and fourth image forming units 1a, 1b, 1c, and 1d are for forming yellow, magenta, cyan, and black color images, respectively. These image forming units 1a, 1b, 1c, and 1d are arranged in a line at regular intervals. In this embodiment, the basic configuration and operation of each of the image forming units 1a to 1d are substantially the same except that the color of the toner used in the developing process described later is different. Therefore, hereinafter, unless it is particularly necessary to distinguish, elements at the end of a symbol indicating that the element is provided for one of the colors is omitted, and the element is generally described. To do.

  The photosensitive drum 2, which is an image carrier that carries a toner image, is rotationally driven at a predetermined process speed (circumferential speed) in the direction of arrow R1 in the figure. The surface of the rotating photosensitive drum 2 is uniformly charged to a predetermined potential having a predetermined polarity (negative polarity in this embodiment) by the drum charging roller 3. During the charging process of the photosensitive drum 2, a photosensitive member charging bias (photosensitive member charging voltage) is applied to the drum charging roller 3 from a photosensitive member charging power source (high voltage power supply circuit) as a photosensitive member charging bias applying unit. The charged surface of the photosensitive drum 2 is scanned and exposed by the exposure device 7 according to the image information. Thereby, an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the photosensitive drum 2. The electrostatic latent image formed on the photosensitive drum 2 is developed (visualized) by the developing device 4 using toner as a developer. As a result, a toner image corresponding to the image information is formed on the photosensitive drum 2. In this embodiment, the same polarity as the charging polarity of the photosensitive drum 2 (negative polarity in this embodiment) is applied to the exposed portion on the photosensitive drum 2 where the absolute value of the potential is reduced by exposure after uniform charging. ) Is charged with charged toner (reverse development). In this embodiment, the normal charging polarity of the toner, which is the charging polarity of the toner at the time of development, is negative, and the toner that forms the toner image has mainly negative charge.

  The image forming apparatus 100 includes an endless belt-shaped intermediate transfer belt 20 disposed so as to face all of the photosensitive drums 2a to 2d of the image forming units 1a to 1d. The intermediate transfer belt 20 is an example of a rotatable intermediate transfer member that conveys the toner image primarily transferred from the image carrier at the primary transfer portion for secondary transfer onto the recording material at the secondary transfer portion. The intermediate transfer belt 20 is stretched around a driving roller 21, a cleaning counter roller 22, and a secondary transfer counter roller 23 as a plurality of support members (stretching rollers), and is stretched with a predetermined tension. The intermediate transfer belt 20 rotates (circulates) in the direction of the arrow R3 in the drawing at a speed substantially equal to the circumferential speed of the photosensitive drum 2 when the driving roller 21 is driven to rotate in the direction of the arrow R2 in the drawing. On the inner peripheral surface side of the intermediate transfer belt 20, the primary transfer rollers 5a to 5d described above are arranged corresponding to the photosensitive drums 2a to 2d of the image forming units 1a to 1d. The primary transfer roller 5 is biased (pressed) toward the photosensitive drum 2 via the intermediate transfer belt 20, and a primary transfer portion (primary transfer portion) that is a contact portion between the photosensitive drum 2 and the intermediate transfer belt 20. Nip) N1 is formed. Further, on the outer peripheral surface side of the intermediate transfer belt 20, a secondary transfer roller 24 that is a roller-type secondary transfer member as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 23. . The secondary transfer roller 24 is biased (pressed) toward the secondary transfer counter roller 23 via the intermediate transfer belt 20, and is a secondary transfer that is a contact portion between the intermediate transfer belt 20 and the secondary transfer roller 24. Part (secondary transfer nip) N2 is formed.

  The toner image formed on the photosensitive drum 2 as described above is transferred (primary transfer) onto the rotating intermediate transfer belt 20 by the action of the primary transfer roller 5 in the primary transfer portion N1. The During the primary transfer process, the primary transfer roller 5 receives a primary transfer bias (with a polarity opposite to the normal charging polarity of toner) from a primary transfer power supply (high voltage power supply circuit) 40 serving as a primary transfer bias application unit. Primary transfer voltage) is applied. For example, when forming a full-color image, yellow, magenta, cyan, and black toner images formed on the photosensitive drums 2a to 2d are sequentially transferred onto the intermediate transfer belt 20 so as to overlap each other.

  The toner image formed on the intermediate transfer belt 20 is conveyed between the intermediate transfer belt 20 and the secondary transfer roller 24 by the action of the secondary transfer roller 24 in the secondary transfer portion N2. Transfer (secondary transfer) is performed on the recording material P. During the secondary transfer process, the secondary transfer roller 24 is supplied with a secondary transfer bias (with a polarity opposite to the normal charging polarity of the toner) from a secondary transfer power supply (high voltage power supply circuit) 44 as a secondary transfer bias applying unit. Secondary transfer voltage) is applied. The recording material P is conveyed to the secondary transfer portion N2 by the registration roller 13 in accordance with the timing at which the leading edge of the toner image on the intermediate transfer belt 20 moves to the secondary transfer portion N2.

  The recording material P onto which the toner image has been transferred is conveyed to a fixing device 12 as a fixing unit, and is heated and pressed at a fixing nip portion between a fixing roller 12A and a pressure roller 12B provided in the fixing device 12. As a result, the toner image is thermally fixed (melted and fixed) on the surface of the recording material P, and, for example, a full-color image is formed on the recording material P. Thereafter, the recording material P is discharged to the outside of the image forming apparatus 100.

  The toner remaining on the photosensitive drum 2 after the primary transfer step (primary transfer residual toner) is removed from the photosensitive drum 2 by the drum cleaning device 6 and collected. The drum cleaning device 6 scrapes the primary transfer residual toner from the rotating photosensitive drum 2 and collects it in the recovered toner container 10 by the cleaning blade 8 which is a plate-like member formed of an elastic body as a cleaning member. The toner remaining on the intermediate transfer belt 20 after the secondary transfer step (secondary transfer residual toner) is transferred onto the intermediate transfer belt 20 by an electrostatic cleaning method using a belt cleaning device 30 as an intermediate transfer member cleaning unit. Removed and recovered. The configuration and operation of the belt cleaning device 30 will be described in detail later.

Here, in this embodiment, the intermediate transfer belt 20 is formed of PEN (polyethylene naphthalate) resin. The surface resistivity of the intermediate transfer belt 20 is 5.0 × 10 ¹¹ Ω / □, and the volume resistivity is 8.0 × 10 ¹¹ Ωcm. In addition, as the intermediate transfer belt 20, a resin such as PVDF (vinylidene fluoride resin), ETFE (tetrafluoroethylene-ethylene copolymer resin), polyimide, PET (polyethylene terephthalate), or polycarbonate is formed in an endless belt shape. May be used. Alternatively, the intermediate transfer belt 20 may be an endless belt formed by coating a rubber base layer such as EPDM with a fluorine resin such as PTFE dispersed in urethane rubber, for example.

  In this embodiment, the primary transfer roller 5 has an elastic layer made of sponge rubber or the like as an elastic member on a core metal (core material). The primary transfer roller 5 rotates following the movement of the intermediate transfer belt 20. In this embodiment, the primary transfer power source 40 connected to the primary transfer roller 5 can select positive and negative biases and apply them to the primary transfer roller 5.

The secondary transfer roller 24 has an elastic layer made of sponge rubber or the like as an elastic member on a core metal (core material). In the present embodiment, a secondary transfer roller was used in which a nickel-plated steel rod having a diameter of 6 mm was coated with NBR hydrin rubber with a thickness of 6 mm. The electrical resistance value of the secondary transfer roller 24 is 3. When the secondary transfer roller 24 is pressed on the aluminum cylinder with a force of 9.8 N and 1000 V is applied with the aluminum cylinder rotated at 50 mm / sec. 0 × 10 ⁷ Ω. The secondary transfer roller 24 rotates following the movement of the intermediate transfer belt 24. In this embodiment, the secondary transfer power source 24 connected to the secondary transfer roller 24 can select positive and negative biases and apply them to the secondary transfer roller 24.

  In this embodiment, a toner image forming unit that forms a toner image on the photosensitive drum 2 is configured by the charging roller 3, the exposure device 7, the developing device 4, and the like of each image forming unit 1.

2. Belt Cleaning Device Next, the belt cleaning device 30 in this embodiment will be described. FIG. 2 is a schematic configuration diagram of the belt cleaning device 30.

  On the outer peripheral surface side of the intermediate transfer belt 20, a belt cleaning device 30 as an intermediate transfer member cleaning unit is disposed at a position facing the cleaning counter roller 22. In the present embodiment, the belt cleaning device 30 includes, as electrostatic cleaning means, a conductive brush 31 that is a first cleaning member (temporary recovery member) and a charging roller 32 that is a second cleaning member (toner charging member). And having. As will be described in detail later, the conductive brush 31 has a function of temporarily collecting the toner on the intermediate transfer belt 20 and a function of charging. The charging roller 32 has a function of charging the toner on the intermediate transfer belt 20 and a function of temporarily collecting the toner. The cleaning counter roller 22 is electrically grounded (connected to the ground).

  The conductive brush 31 and the charging roller 32 are first and second downstream of the secondary transfer portion N2 and upstream of the primary transfer portion N1 (the most upstream primary transfer portion N1a) in the rotational direction of the intermediate transfer belt 20. The contact portions CL1 and CL2 are disposed so as to come into contact with the intermediate transfer belt 20, respectively. That is, the conductive brush 31 is located upstream of the charging roller 32 and downstream of the secondary transfer portion N2 in the rotational direction of the intermediate transfer belt 20. The charging roller 32 is located downstream of the conductive brush 31 and upstream of the primary transfer portion N1 (the most upstream primary transfer portion N1a) in the rotational direction of the intermediate transfer belt 20.

In this embodiment, the conductive brush 31 is composed of a brush-like member having conductivity. In particular, in this embodiment, the conductive brush 31 is formed using nylon as the material, the fineness is 7 dtex, the pile length is 5 mm, and the brush width is 5 mm. The electric resistance value of the conductive brush 31 is 1.0 when 500 V is applied while the conductive brush 31 is pressed onto the aluminum cylinder with a force of 9.8 N and the aluminum cylinder is rotated at 50 mm / sec. × 10 ⁸ Ω. The conductive brush 31 is biased (pressed) toward the cleaning counter roller 22 via the intermediate transfer belt 20. The conductive brush 31 is fixedly disposed and rubs the surface of the moving intermediate transfer belt 20.

The conductive brush 31 can be connected to a first cleaning power supply (high-voltage power supply circuit) 50 serving as a first cleaning bias application unit via a first current detection circuit 70 serving as a current detection unit. The first cleaning power supply 50 is also referred to as a first positive bias output unit 51 that outputs a positive polarity bias (herein also referred to as “positive bias”) and a negative polarity bias (here as “negative bias”). ) To output a first negative bias output unit 52. The first positive bias output unit 51 and the first negative bias output unit 52 are selectively connected to the conductive brush 31 via the first current detection circuit 70 by switching elements SW1 and SW2, respectively. That is, the first cleaning power supply 50 can selectively apply positive and negative biases to the conductive brush 31. In the present embodiment, the upper limit outputs of the first positive bias output unit 51 and the first negative bias output unit 52 of the first cleaning power supply 50 are 4000 V and −4000 V, respectively. Bias applied to the conductive brush 31 is a DC voltage, the output is controlled based on a current first current detection circuit 70 detects, as current value becomes the brush target current value I _B previously set Constant current control. In this embodiment, the initial brush target current value I _B = 10 μA is used. The initial use means a state that is functionally equivalent to that of a new product (no adjustment is required in the cleaning bias adjustment operation described later).

In this embodiment, the charging roller 32 is composed of a roller-like member having conductivity. In particular, in this embodiment, the charging roller 32 is an elastic body layer formed of a solid rubber in which carbon is dispersed in EPDM rubber as an elastic member on a nickel-plated steel rod having a diameter of 6 mm as a core metal (core material). Was coated with a thickness of 5 mm. The electric resistance value of the charging roller 32 is 5.0 × 10 when 500 V is applied while the charging roller 32 is pressed onto the aluminum cylinder with a force of 9.8 N and the aluminum cylinder is rotated at 50 mm / sec. ⁷ Ω. The charging roller 32 is urged (pressed) with a total pressure of 9.8 N toward the cleaning counter roller 22 via the intermediate transfer belt 20. The charging roller 32 rotates following the movement of the intermediate transfer belt 20.

The charging roller 32 can be connected to a second cleaning power supply (high-voltage power supply circuit) 60 serving as a second cleaning bias application unit via a second current detection circuit 80 serving as a current detection unit. The second cleaning power supply 60 includes a second positive bias output unit 61 that outputs a positive bias, and a second negative bias output unit 62 that outputs a negative bias. The second positive bias output unit 61 and the second negative bias output unit 62 are selectively connected to the charging roller 32 via the second current detection circuit 80 by switching elements SW3 and SW4, respectively. That is, the second cleaning power source 60 can selectively apply positive and negative biases to the charging roller 32. In the present embodiment, the upper limit outputs of the second positive bias output unit 61 and the second negative bias output unit 62 of the second cleaning power supply 60 are 4000 V and −4000 V, respectively. Bias applied to the charging roller 32 is a DC voltage, the output is constant so that the second current detection circuit 80 is controlled based on the current detected, rollers target current current value preset value I _R Current controlled. In this embodiment, the initial roller target current value I _{R is} 10 μA.

  The toner on the intermediate transfer belt 20 before the secondary transfer step has a negative polarity having the same polarity as the charged charge on the surface of the photosensitive drum 2 (same polarity as the normal charging polarity of the toner), and there is a variation in charge distribution. It is charged in a relatively small state. On the other hand, the secondary transfer residual toner on the intermediate transfer belt after the secondary transfer step has a relatively wide charge distribution and peaks on the positive polarity side, which is opposite to the normal charge polarity of the toner. Is charged while moving. As a result, the secondary transfer residual toner is in a state where a negatively charged toner, a hardly charged toner, and a positively charged toner are mixed.

  At the time of the cleaning operation for cleaning the secondary transfer residual toner on the intermediate transfer belt 7 by the belt cleaning device 30, the switching elements SW1 and SW3 are turned on as shown in FIG. The conductive brush 31 has a positive bias (first cleaning bias) from the first positive bias output unit 51, and the charging roller 32 has a positive bias (second cleaning bias) from the second positive bias output unit 61. ) Is applied. The conductive brush 31 located on the upstream side electrostatically collects (temporarily collects) the negatively charged toner of the secondary transfer residual toner. Thereby, during the cleaning operation of the intermediate transfer belt 20, the amount of secondary transfer residual toner that reaches the charging roller 32 positioned on the downstream side can be reduced. In addition, the conductive brush 31 also acts to charge (pre-charge) the secondary transfer residual toner to the positive polarity side by discharging between the conductive brush 31 and the secondary transfer residual toner.

  On the other hand, during the cleaning operation of the intermediate transfer belt 20, the charging roller 32 positioned on the downstream side uniformly discharges the secondary transfer residual toner that has passed through the conductive brush 31 due to discharge due to a potential difference with the intermediate transfer belt 20. Charge to positive polarity. In this embodiment, the secondary transfer residual toner charged to the positive polarity by the charging roller 32 is transferred to the intermediate transfer belt at the primary transfer portion N1a of the most upstream first image forming portion 1a in the rotation direction of the intermediate transfer belt 20. 20 is transferred to the photosensitive drum 2a. At this time, a bias having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the primary transfer roller 5a of the first image forming unit 1a. The transfer of the secondary transfer residual toner from the intermediate transfer belt 20 to the photosensitive drum 2a can be performed simultaneously with the transfer of the toner image from the photosensitive drum 2a to the intermediate transfer belt 20. The secondary transfer residual toner transferred to the photosensitive drum 2a is removed from the photosensitive drum 2a by the drum cleaning device 6a and collected.

  In this way, the secondary transfer residual toner on the intermediate transfer belt 20 is positively charged by the belt cleaning device 30 and then collected on the photosensitive drum 2a by the primary transfer portion N1a, whereby the secondary transfer residual toner is collected. It can be removed from the intermediate transfer belt 20. If a large amount of secondary transfer residual toner reaches the charging roller 32 at once, the positive charge is not sufficiently applied to the secondary transfer residual toner, resulting in poor cleaning. For this reason, the conductive brush 31 is expected to temporarily collect the secondary transfer residual toner. However, if the secondary transfer residual toner is temporarily collected with the conductive brush 31, it is necessary to increase the frequency of the discharge process described later. Therefore, the amount of the toner passing through the conductive brush 31 is made substantially constant with an appropriate amount. It is important to keep. It is also important to keep the charging performance of the charging roller 32 substantially constant in order to suppress poor cleaning. That is, it is important that the functions of the conductive brush 31 and the charging roller 32 are maintained in good balance even when the number of printed sheets increases.

  The cleaning member is not limited to the conductive brush 31 and the charging roller 32 in this embodiment. For example, instead of the conductive brush 31 or the charging roller 32 in this embodiment, a pad-like member (for example, formed of urethane rubber or NBR hydrin rubber) formed of a foam sponge or the like that is fixedly arranged is used. May be. Further, instead of the charging roller 32 or the conductive brush 31 in this embodiment, a rotatable fur brush roller, a rotatable foam sponge roller, or the like may be used.

Next, the amount of toner collected on the intermediate transfer belt 20 by the conductive brush 31 will be described. FIG. 3 shows the result of examining the relationship between the current flowing through the conductive brush 31 and the amount of toner collected on the intermediate transfer belt 20 by the conductive brush 31. The horizontal axis in FIG. 3 indicates the value of the current flowing through the conductive brush 31 detected by the first current detection circuit 70. Also, the vertical axis in FIG. 3 indicates the amount of toner collected on the intermediate transfer belt 20 by the conductive brush 31, and the amount collected at the initial brush target current value I _B = 10 μA is normalized to 1. Yes. In FIG. 3, the solid line indicates the measured data, the dotted line indicates the approximate line, and the approximate line also indicates the equation.

  As shown in FIG. 3, the amount of toner collected on the intermediate transfer belt 20 by the conductive brush 31 correlates with the value of the current flowing through the conductive brush 31. When the current value is small, the recovery amount is small, and when the current value is increased, the recovery amount increases and eventually becomes saturated.

  Next, the cleaning performance of the charging roller 32 will be described. FIG. 4 shows the result of examining the relationship between the positive bias applied to the charging roller 32 and the current. In FIG. 4, the horizontal axis indicates the value of the positive bias applied to the charging roller 32, and the vertical axis indicates the current value flowing through the charging roller 32 detected by the second current detection circuit 80. FIG. 4 also shows the results of examining the cleaning performance of the charging roller 32.

  The cleaning performance was evaluated according to the following procedure. GFC-081 (Canon Marketing Japan, trade name) was used for the recording material P. A solid image (maximum density level image), a halftone image, and a character thin line image are represented by C (cyan), M (magenta), Y (yellow), K (black), R (red), B (blue), and G, respectively. Three sheets were output in each (green) color. The sampled evaluation images were evaluated for occurrence of image defects due to cleaning defects. Specifically, the evaluation was performed by observing whether an image of one cycle before the intermediate transfer belt 20 was generated in the sampled evaluation image. As the evaluation criteria, a case where an image defect does not occur is indicated as ◯, and a case where an image defect occurs is indicated as ×.

  As shown in FIG. 4, the cleaning performance correlates with the current value flowing through the charging roller 32. If the current value is smaller than 10 μA, a cleaning failure occurs. The current flowing through the charging roller 32 depends on the magnitude of the positive bias applied to the charging roller 32, and the current value increases as the bias increases.

3. Control Mode In this embodiment, the operation of each unit of the image forming apparatus 100 is controlled by a control unit 150 (FIG. 1) as a control unit provided in the apparatus main body of the image forming apparatus 100. The control unit 150 includes a calculation control unit (CPU), a storage unit (ROM, RAM), and the like, and the calculation control unit controls the operation of each unit of the image forming apparatus 100 according to programs and data stored in the storage unit. To control. In relation to this embodiment, the control unit 150 executes the image forming operation and controls the first and second cleaning power supplies 50 and 60 (switching elements SW1 to SW4) to clean the intermediate transfer belt 20. Run the action.

  Here, the image forming apparatus 100 executes a series of image output operations (jobs, print operations) that form and output an image on a single or a plurality of recording materials P, which is started by one start instruction. In general, a job includes an image forming process, a pre-rotating process, a paper-to-paper process when images are formed on a plurality of recording materials P, and a post-rotating process. The image forming process is a period in which an electrostatic latent image of an image actually formed and output on the recording material P, a toner image, a primary transfer and a secondary transfer of the toner image are performed. Refers to this period. More specifically, the timing at which the image is formed differs depending on the position at which the electrostatic latent image formation, toner image formation, toner image primary transfer and secondary transfer steps are performed. The pre-rotation process is a period for performing a preparatory operation before the image forming process from when the start instruction is input until the actual image formation is started. The inter-sheet process is a period corresponding to the interval between the recording material P and the recording material P when image formation is continuously performed on a plurality of recording materials P (continuous image formation). The post-rotation process is a period during which an organizing operation (preparation operation) after the image forming process is performed. The non-image forming period is a period other than the image forming time, and is a preparatory operation at the time of turning on the power of the image forming apparatus 100 or returning from the sleep state. This is included during the previous multi-rotation process. The cleaning bias adjustment operation described later is executed during non-image formation.

4). Discharging Process Next, the discharging process, which is a process of transferring (discharging) the secondary transfer residual toner attached to the conductive brush 31 and the charging roller 32 to the intermediate transfer belt 20, will be described.

  During the cleaning operation of the intermediate transfer belt 20, a positive bias is applied to the conductive brush 31 and the charging roller 32, and a positive electric field is formed toward the cleaning counter roller 22. That is, at this time, in the first contact portion CL1, between the intermediate transfer belt 20 and the conductive brush 31, toner charged with a normal charging polarity is directed from the intermediate transfer belt 20 side to the conductive brush 31 side. An electric field to be applied (energized) is formed. Further, at this time, in the second contact portion CL2, between the intermediate transfer belt 20 and the charging roller 32, the toner charged to the normal charging polarity is directed from the intermediate transfer belt 20 side to the charging roller 32 side ( An electric field is formed. Then, a part of the toner having the normal charging polarity (negative polarity) in the secondary transfer residual toner adheres to the conductive brush 31 and the charging roller 32 by electrostatic attraction without being charged to the positive polarity. . The toner adhering to the conductive brush 31 accumulates, and when it reaches a predetermined amount, it becomes impossible to collect and hold any more toner, and the cleaning performance deteriorates. Similarly, when toner adheres to the surface of the charging roller 32 and the amount of adhesion increases, the charging performance of the charging roller 32 becomes unstable and the cleaning performance deteriorates.

  Therefore, the toner adhering to the conductive brush 31 and the charging roller 32 is transferred (discharged) to the intermediate transfer belt 20, and the toner is transferred to the photosensitive drum 2 and discharged by the drum cleaning device 6. A process is performed. The discharging process is executed at a timing when image formation is not performed (during non-image formation), such as during a post-rotation process or during a processing operation after occurrence of a jam (recording material P is jammed in the conveyance path). As a result, the amount of toner adhering to the conductive brush 31 and the charging roller 32 is reduced, and the deterioration of the cleaning performance is suppressed.

  Most of the toner held on the conductive brush 31 and the charging roller 32 is negatively charged, but a small amount of toner that has become positive due to discharge is also attached. Therefore, in this embodiment, in the discharging process, negative bias and positive bias are alternately switched and applied to the conductive brush 31 and the charging roller 32, respectively. That is, at this time, between the intermediate transfer belt 20 and the conductive brush 31, the toner charged to the normal charging polarity and the toner charged to the opposite polarity are respectively transferred from the conductive brush 31 side to the intermediate transfer belt. Electric fields directed (energized) toward the 20 side are alternately formed. At this time, between the intermediate transfer belt 20 and the charging roller 32, the toner charged to the normal charging polarity and the toner charged to the opposite polarity are respectively transferred from the charging roller 32 side to the intermediate transfer belt 20 side. Electric fields that are directed toward (energized) are alternately formed. That is, the following two states are switched alternately. First, as shown in FIG. 2B, the switching elements SW2 and SW4 are turned on, and the negative bias is applied to the conductive brush 31 and the charging roller 32 from the first and second negative bias output units 52 and 62, respectively. It is a state to be applied. Secondly, as shown in FIG. 2A, the switching elements SW1 and SW3 are turned on, and the positive bias is applied to the conductive brush 31 and the charging roller 32 from the first and second positive bias output units 51 and 61, respectively. It is a state to be applied. Thus, during the discharging process, the electric field between the conductive brush 31 and the cleaning counter roller 22 and the electric field between the charging roller 32 and the cleaning counter roller 22 are alternately reversed positively and negatively. As a result, the toner accumulated on the conductive brush 31 and the toner adhering to the charging roller 32 are discharged onto the intermediate transfer belt 20.

In the discharging process, the conductive brush 31, the absolute value of the current flowing through both the positive bias and a negative bias to be brush target current value I _B is applied. Further, in the discharging step, the charging roller 32, the absolute value of the current flowing through either there is a positive bias and a negative bias to be roller target current value I _R is applied.

  During the discharging process, the intermediate transfer belt 20 is rotationally driven in the direction of the arrow R3 in FIG. In this embodiment, the toner discharged onto the intermediate transfer belt 20 (also referred to as “discharge toner” here) is mainly the primary of the first image forming unit 1a which is the most upstream in the rotation direction of the intermediate transfer belt 20. At the transfer portion N1a, the intermediate transfer belt 20 is transferred to the photosensitive drum 2a. At this time, a bias having the same polarity (negative polarity in this embodiment) as the normal charging polarity of the toner is applied to the primary transfer roller 5a of the first image forming unit 1a. As a result, the discharged toner that is charged mainly in the negative polarity is collected on the photosensitive drum 2a of the first image forming unit 1a. The discharged toner transferred to the photosensitive drum 2a is removed from the photosensitive drum 2a by the drum cleaning device 6a and collected. The discharged toner charged to the positive polarity can be collected on the photosensitive drum 2a of the same first image forming unit 1a, or can be collected on the photosensitive drum 2 of another image forming unit 1. At that time, a bias having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the primary transfer roller 5 of the image forming unit 1.

5. Optical Sensor Next, the optical sensor 9 as a detection unit included in the image forming apparatus 100 will be described. The optical sensor 9 is used for image density correction and registration correction, and is used for a cleaning bias adjustment operation described later in detail.

  The optical sensor 9 can detect toner on the intermediate transfer belt 20 downstream of the primary transfer portion N1 (the most downstream primary transfer portion N1a) and upstream of the secondary transfer portion N2 in the rotation direction of the intermediate transfer belt 20. Is arranged. In the present embodiment, the width direction (main scanning direction) is such that the toner on the intermediate transfer belt 20 can be detected at both ends with respect to the center in the width direction (direction substantially orthogonal to the moving direction) of the intermediate transfer belt 20. Two optical sensors 9 are arranged (see FIG. 7).

FIG. 5 is a schematic diagram of the optical sensor 9. The optical sensor 9 includes a light emitting element 91 such as an LED and a light receiving element 92 such as a photodiode. The optical sensor 9 irradiates the toner T on the intermediate transfer belt 20 with infrared light from the light emitting element 91, and measures the specular reflection light with the light receiving element 92, whereby the position and density of the toner T (per unit area). The amount of toner and the amount of toner applied (mg / cm ² ) can be detected.

  FIG. 6 shows the output characteristics of the optical sensor 9. The output of the optical sensor 9 (the amount of light received by the photodiode 92) decreases as the amount of applied toner increases. This is because when the amount of applied toner on the intermediate transfer belt 20 is increased, the irradiation light is diffused by the toner, and the surface of the intermediate transfer belt 20 as a base is hidden, so that the regular reflection light from the intermediate transfer belt 20 is reduced. Because it does.

  In the image forming apparatus 100, the density and position of the obtained image may fluctuate if there are fluctuations in each part of the apparatus due to environmental changes or prolonged use. Therefore, it is necessary to periodically perform image density correction and registration correction (also referred to as “calibration” here) for the purpose of correcting density and position fluctuations. In this embodiment, the calibration is executed when the environmental temperature fluctuates by 5 ° C. or more from the previous calibration, or every time the number of printed sheets exceeds 1000 sheets.

  FIG. 7 is a schematic diagram illustrating an image pattern for calibration in the present embodiment. In this embodiment, the following image patterns are formed at positions that can be detected by the optical sensors 9 and 9 on both ends in the width direction of the intermediate transfer belt 20. First, for registration correction in the moving direction (sub-scanning direction) of the intermediate transfer belt 20, linear registration patterns PY, PM, PC, and PK extending in the main scanning direction are yellow, It is formed in the order of magenta, cyan, and black. Next, for registration correction in the main scanning direction, substantially L-shaped registration patterns SY, SM, SC, and SK inclined with respect to the sub-scanning direction are yellow, magenta, cyan, and black. Are formed in this order. Next, for image density correction, 8 mm square patches are changed at 10-step intervals, and the image print rate (density gradation degree) is changed in five steps for each color in the order of yellow, magenta, cyan, and black (5 patches for each color). 20 pieces in total are formed. The correspondence between each patch and the printing rate (gradation) is Y1, M1, C1, K1 = 20%, Y2, M2, C2, K2 = 40%, Y3, M3, C3, K3 = 60%, Y4, M4. , C4, K4 = 80%, Y5, M5, C5, K5 = 100%.

6). Cleaning Bias Adjustment Operation Next, a cleaning bias adjustment operation using the optical sensor 9 in this embodiment (herein, simply referred to as “adjustment operation”) will be described. FIG. 8 shows a flowchart of the adjustment operation.

  First, in STEP 1, the control unit 150 executes image density correction and registration correction (calibration). At the time of calibration, an image pattern for calibration shown in FIG. 7 is formed on the intermediate transfer belt 20, the image pattern is detected by the optical sensor 9, and image density correction and registration correction are performed. At the time of calibration, substantially the same image pattern is formed every time, so that the amount of toner placed on the intermediate transfer belt 20 at each time of calibration is substantially constant.

Next, in STEP 2, the control unit 150 causes the intermediate transfer belt 20 to be cleaned. In order to charge the image pattern for calibration on the intermediate transfer belt 20 to the positive polarity, a positive bias is applied to the conductive brush 31 and the charging roller 32, respectively, and the brush target current value I _B before adjustment and the roller are adjusted. target current value _{I R} flows. In this description, as an example, it is assumed that the brush target current value I _B before adjustment (current) I _B = 14 μA and the roller target current value I _R before adjustment (current) I _R = 14 μA. The positively charged toner of the calibration image pattern is transferred to the photosensitive drum 2a of the first image forming unit 1a and collected by the drum cleaning device 6a. On the other hand, the negative polarity toner of the image pattern for calibration is temporarily collected by the conductive brush 31 and the charging roller 32. At the time of calibration, the image pattern for calibration on the intermediate transfer belt 20 is cleaned substantially by using the belt cleaning device 30 without being transferred onto the recording material P. Therefore, the amount of toner on the intermediate transfer belt 20 that reaches the belt cleaning device 30 is larger at the time of calibration than at the time of normal image formation. For example, when the transfer efficiency in the secondary transfer process is 95%, 95% is transferred to the recording material P, and only the remaining 5% remains on the intermediate transfer belt 20, but 100% is transferred during calibration. It will remain on the belt 20.

  Next, in STEP 3, the control unit 150 causes the discharge process to be executed. During the discharging process after the calibration, more toner is charged in the conductive brush 31 and the charging than the discharging process of the secondary transfer toner collected during normal image formation (also referred to as “normal discharging process” here). Collected by the roller 32. Therefore, a relatively large amount of toner is discharged during the discharging process after calibration. That is, since the toner is discharged at each post-rotation process or the like, only a relatively small amount of toner is discharged from the conductive brush 31 and the charging roller 32 during the normal discharge process. On the other hand, during the discharging process after calibration, more toner is discharged from the conductive brush 31 and the charging roller 32 than during the normal discharging process. Therefore, by using this toner, it is possible to accurately determine the degree of deterioration of the conductive brush 31 and the charging roller 32. This is because data on the degree of deterioration of the conductive brush 31 and the charging roller 32 over a relatively wide range can be acquired. In the adjustment operation, the detection result by one of the two optical sensors 9 provided in the main scanning direction may be used, or the detection results by both are subjected to statistical processing such as summation processing and average processing. It may be used.

Then, in STEP4, the control unit 150, by measuring the amount of toner discharged in the first lap of the rotation of the intermediate transfer belt 20 (toner discharge), it is performed to optimize the brush target current value I _B.

In this embodiment, schematically, to set as follows (adjustment), and the optimization of the brush target current value I _B. That is, the brush target current is set so that the amount of toner collected by the conductive brush 31 at the time of the adjustment operation approaches the amount of toner collected by the conductive brush 31 in the initial stage of use (typically substantially the same). it is to set the value I _B.

The conductive brush 31 is expected to reduce the amount of toner reaching the downstream charging roller 32 and suppress the occurrence of defective cleaning by electrostatically collecting the negatively charged toner temporarily. Has been. However, when the function of the conductive brush 31 is deteriorated due to deterioration of energization or adhesion of discharge products, the amount of toner that can be collected decreases. To compensate for the decrease of this feature, the brush target current value it is necessary to increase the I _B, because it causes a further energization degradation excessively raised, conductive degradation in accordance with the degree appropriate brush target current value of the brush 31 it is desirable to select the I _B.

In this embodiment, The greater than the amount that initial use of the toner conductive brush 31 could be recovered in STEP2, a brush target current value I _B is greater than the appropriate value for the degree of deterioration of the conductive brush 31 to decide. Conversely, the amount of toner that could conductive brush 31 in STEP2 is recovered the less than initial use, it is determined that the brush target current value I _B is smaller than the proper value for the degree of deterioration of the conductive brush 31.

Further illustrate the process of setting the brush target current value I _B. When the discharging process is started in STEP 3, the toner is discharged from the conductive brush 31 and the charging roller 32 in the first rotation of the intermediate transfer belt 20. The amount of toner discharged at this time is governed by the amount of toner discharged from the conductive brush 31. Therefore, the amount of toner temporarily collected by the conductive brush 31 can be estimated from the amount of discharged toner, and the temporary collection performance of the conductive brush 31 at the time of the adjustment operation can be estimated. Therefore, the amount of discharged toner is detected by the optical sensor 9, and the amount of discharged toner, that is, the amount of toner temporarily collected by the conductive brush 31 and the charging roller 32 (mainly the conductive brush 31) is measured. .

  Here, in the normal discharging process, the discharged toner is transferred to the photosensitive drum 2 and collected by the drum cleaning device 6. On the other hand, in STEP4, the discharged toner in STEP3 is passed through the primary transfer portions N1a to N1d of the image forming portions 1a to 1d. In this embodiment, the image forming apparatus 100 is provided with a separation mechanism (not shown) that separates the intermediate transfer belt 20 from the photosensitive drums 2a to 2d of the image forming units 1a to 1d. During the adjustment operation, the intermediate transfer belt 20 is separated from the photosensitive drums 2a to 2d of all the image forming units 1a to 1d. Thus, the discharged toner in STEP 3 passes through the positions corresponding to the primary transfer portions N1a to N1d, and the amount thereof can be measured by the optical sensor 9.

FIG. 9 shows the state of the optical sensor 9 when the discharged toner in STEP 3 is detected by the optical sensor 9 when the conductive brush 31 is used until the latter half of its life (herein after also referred to as “after durability”). Indicates the output. In the initial stage of use, the amount of toner that can be temporarily collected by the conductive brush 31 is large, and the output of the optical sensor 9 is relatively small. On the other hand, after the endurance, the amount of toner that can be temporarily collected by the conductive brush 31 is reduced due to deterioration due to energization or adhesion of discharge products, and the output of the optical sensor 9 is relatively increased. In this example, I set the (substantially the same typically) such brush target current value I _B closer to the output of the optical sensor 9 outputs the initial use of the optical sensor 9 after the durability test. Accordingly, unnecessarily raise the brush target current value I _B, without accelerating the increase in the electrical resistance of the conductive brush 31, to obtain a temporary recovery performance of substantially constant conductive brush 31 after the durability and initial use be able to.

In this embodiment, the average value (average output value) of the output of the optical sensor 9 when the discharged toner area (discharge toner detection range) on the intermediate transfer belt 20 is detected is the same between the endurance and the initial use. as set brush target current value I _B after adjustment. Specifically, in this embodiment, by using each of the following information, it performs optimization of the brush target current value I _B. 9, the average output value at the initial use brush target current value I _B = 10 μA acquired in advance, the average output value after endurance acquired in STEP 4, the relationship between the current value and the toner recovery amount shown in FIG. This is the relationship between the output of the optical sensor 9 shown in FIG. The average output value at the initial stage of use, the relationship of FIG. 3, and the relationship of FIG. 6 are acquired in advance and stored in the storage unit of the control unit 150.

First, the control unit 150 calculates the average output value after durability shown in FIG. Next, the control unit 150 determines from the conductive brush 31 and the charging roller 32 (mainly the conductive brush 31) based on the calculated average output value and the relationship between the output of the optical sensor 9 and the amount of applied toner shown in FIG. The amount of discharged toner (per unit area) is calculated. Next, the control unit 150 calculates the ratio of the amount of discharged toner after the initial use and after the endurance using the following information. The amount of discharged toner (per unit area) at the initial brush target current value I _B = 10 μA and the amount of discharged toner (per unit area) after the endurance (current) brush target current value I _B = 14 μA is there. For example, the ratio is calculated such that the amount of discharged toner at the beginning of use: the amount of discharged toner after endurance = 1.0: 0.9.

Next, the control unit 150, as the amount of toner conductive brush 31 the amount of toner discharged is collected to calculate the brush target current value I _B using an approximate expression shown in FIG. For example, a brush target current value I _B is calculated as follows.

First, from the above description, the following equation holds.
1.0 (amount of discharged toner at the beginning of use) −0.9 (amount of discharged toner after endurance)
= 0.1

Further, since the approximate expression shown in FIG. 3 the slope is 0.05, the following formula, brush target current value I _B it is seen that may be increased by 2 [μA].
0.1 / 0.05 = 2 [μA]

Therefore, the following equation, brush target current value I _B can be calculated as 16 [μA].
14 [μA] (Brush target current value I _B before adjustment) + 2 = 16 [μA] (Brush target current value I _B after adjustment)

Next, in STEP 5, the control unit 150 measures the amount of toner collected on the photosensitive drum 2 from the discharged toner in STEP 3 from the second rotation of the intermediate transfer belt 20 after starting the discharging process. performing optimization of rollers target current value I _R.

In this embodiment, schematically, to set as follows (adjustment), and the optimization of the roller target current value I _R. In other words, the charging performance of the charging roller 32 at the time of adjustment operation, (typically substantially identical) to close the charging performance of the initial use of the charging roller 32 so as to set the rollers target current value I _R That is.

In STEP 5, no bias is applied to the conductive brush 31, and substantially all of the discharged toner in STEP 3 passes through the charging roller 32. The discharged toner is given a positive charge by the charging roller 32, is transferred to the photosensitive drum 2a of the first image forming unit 1a, and is collected by the drum cleaning device 6a. As described above, it is assumed that the roller target current value I _R = 14 μA flows through the charging roller 32 at this time. Since the amount of discharged toner in the discharging process after calibration is relatively large, substantially all of the discharged toner cannot be made positive by applying positive charge once by the charging roller 32. Therefore, it is necessary to rotate the intermediate transfer belt 20 a plurality of times, and the optical sensor 9 detects toner that cannot be charged positively and cannot be collected on the photosensitive drum 2a. In this embodiment, the image forming apparatus 100 has a separation mechanism that separates the secondary transfer roller 24 from the intermediate transfer belt 20, and the toner passes through a position corresponding to the secondary transfer portion N2 during the adjustment operation. In doing so, the secondary transfer roller 24 is separated from the intermediate transfer belt 20.

Here, the amount of toner discharged during the normal discharging process is relatively small. Therefore, when the normal discharging process, as the toner discharge by rotating the number of times the intermediate transfer belt 20 is less than the time step discharging after calibration can be recovered sufficiently photosensitive drums 2a, the roller target current value I _R It is preferable to set. In this embodiment, when the normal discharging process, by rotating the single intermediate transfer belt 20, so as to be substantially recovered all discharged toner to the photosensitive drum 2a, sets the rollers target current value I _R. Thereby, the energization deterioration of the charging roller 32 can be suppressed.

In this embodiment, the initial use of the roller target current value I _R is 10 .mu.A. In this case, in the initial stage of use of the charging roller 32, substantially all the discharged toner on the intermediate transfer belt 20 is collected on the photosensitive drum 2a by rotating the intermediate transfer belt 20 four times in the discharge process after calibration. be able to.

Then, in this embodiment, The greater than the amount that initial use of the toner can be recovered to the photosensitive drum 2a in STEP5, the roller target current value I _R is larger than the proper value for the degree of deterioration of the charging roller 32 to decide. Conversely, the amount of toner that could be recovered to the photosensitive drum 2a in STEP5 is the less than the initial use, the roller target current value I _R is determined to be smaller than the proper value for the degree of deterioration of the charging roller 32.

Further illustrate the process of setting the roller target current value I _R. In STEP 5, first, the discharged toner remaining on the intermediate transfer belt 20 without being collected on the photosensitive drum 2 a by the first rotation of the intermediate transfer belt 20 is detected by the optical sensor 9. Then, when the intermediate transfer belt 20 is rotated for the second time, the third time, the fourth time, and the second time, it is possible to detect the process in which the discharged toner on the intermediate transfer belt 20 is reduced by the optical sensor 9, and the intermediate transfer belt can be detected from the output of the optical sensor 9. The amount of toner on 20 can be estimated.

10, the output of the optical sensor 9 when shook using initial roller target current value I _R (solid line, broken line, dashed line) and, (two-dot chain line) the output of the optical sensor 9 acquired in STEP5 after durability Indicates. The horizontal axis in FIG. 10 indicates the number of rotations of the intermediate transfer belt 20. Further, the vertical axis in FIG. 10 represents the optical when the discharged toner area (discharge toner detection range) on the intermediate transfer belt 20 is detected when the output of the optical sensor 9 with respect to the background of the intermediate transfer belt 20 is 100. The average value (average output value) of the output of the sensor 9 is shown.

Larger rollers target current value I _R, since the toner is caused to positively charged in one charging process by the charging roller 32 is increased, increasing the toner collected in the photosensitive drums 2a, increases the output of the optical sensor 9 . Conversely, reducing the roller target current value I _R, since the toner is caused to positively charged is reduced by one charging process by the charging roller 32 reduces the toner to be collected on the photosensitive drum 2a, the output of the optical sensor 9 Becomes smaller. Further, it can be seen that the output of the optical sensor 9 after the endurance does not become 100, which is the output of the optical sensor 9 with respect to the background of the intermediate transfer belt 20, even in the fourth rotation of the intermediate transfer belt 20.

From this result, it is possible to estimate the ability of the charging roller 32 after the endurance to charge the toner on the intermediate transfer belt 20 to the positive polarity as compared with the initial use. In this embodiment, the amount of discharged toner that can be collected on the photosensitive drum 2 by one positive charge application is used as a measure of the charging performance of the charging roller 32. In particular, in this embodiment, the charging performance of the charging roller 32 is estimated from the amount of discharged toner collected on the photosensitive drum 2 by the second positive charge application. In FIG. 10, this corresponds to estimating the charging performance of the charging roller 32 from the difference in the output of the optical sensor 9 between the first time and the second time. In other words, in this embodiment, the difference in the output after the endurance approaches the difference in the output at the initial use roller target current value I _R = 10 μA (typically the same) so that the roller target current value is the same. to set the I _R. Accordingly, unnecessarily raise the roller target current value I _R, without accelerating the increase in the electrical resistance of the charging roller 32, it can be in after the durability and use initial obtain charging performance of the substantially constant charge roller 32 . The charging performance of the charging roller 32 is not limited to estimation from the amount of discharged toner collected on the photosensitive drum 2 by the second positive charge application, and may be the first, third, or fourth time. In this embodiment, since the amount of toner that can be collected at the second time is relatively large, adjustment accuracy can be improved by using the amount of toner that can be collected at the second time.

This will be further described with an example of a specific calculation method. In FIG. 10, the output of the first optical sensor 9 is 10 and the output of the second optical sensor 9 is 50 at the initial roller target current value I _R = 10 μA. Therefore, the charging performance of the charging roller 32 in the initial stage of use is 50 (output of the second optical sensor 9) −10 (output of the first optical sensor 9) = 40. Information on the charging performance at the initial stage of use is acquired in advance and stored in the storage unit of the control unit 150. In the same manner as described above, the charging performance of the charging roller 32 after durability is 35 (= 55-20). This result is a charging performance difference 5 (= 40-35) to fill in the, it is understood that it is sufficient to set the roller target current value I _R.

The charging performance at the initial roller target current value I _R = 20 μA is 80 (= 90−10) in the same manner as described above. Then, in the case of initial use of the roller target current value I _{R =} 10 .mu.A, the difference between the outputs of the optical sensors 9 in the case of rollers the target current value I _{R =} 20 .mu.A, the output and the roller target current value I _R of the optical sensor 9 Can be calculated. That is, the difference in the output of the optical sensor 9 when the roller target current value I _R = 10 μA is 40, and the difference in the output of the optical sensor 9 when the roller target current value I _R = 20 μA is 80. Therefore, the increase / decrease (slope, change rate) of the output of the optical sensor 9 per roller target current value I _R = 1 μA can be calculated to be 4. Information on this relational expression is acquired in advance and stored in the storage unit of the control unit 150. Thus, the roller target current value I _R is calculated as follows. First, from the above description, the following equation holds.
Y (optical sensor output increases or decreases) = 4 × X (roller target current value _{I R} increases or decreases)

Further, by using this relationship, in order to fill the difference between 5 the output of the optical sensor 9 after initial use and durability, as follows, the rollers target current value I _R only 1.25 [.mu.A] You can see that it should be raised.
5 (optical sensor output difference) ÷ 4 = 1.25 [μA]

Therefore, the following equation, the roller target current value _{I R} can be calculated as 15.25 [μA].
14 [μA] (Roller target current value I _R before adjustment) +1.25 [μA] = 15.25 [μA] (Roller target current value I _R after adjustment)

7). Verification of the effect of the present embodiment The presence or absence of a cleaning defect is confirmed when the above-described adjustment operation is performed in the image forming apparatus 100 shown in FIG. 1 (this embodiment) and when it is not performed (comparative example). did. Except for not performing the adjustment operation described above, the configuration and operation of the image forming apparatus 100 of the comparative example are substantially the same as those of the present embodiment. Table 1 shows the results of the comparative example, and Table 2 shows the results of this example.

Here, we perform evaluation of cleaning performance for each 5000 sheets printed sheets were recorded voltage was required to flow that time brush target current I _B, the roller target current I _R. In the comparative example, as cleaning failure does not occur even when the conductive brush 31 and the charging roller 32 the number of prints is increased is energized deteriorated, the embodiment of the brush target current value I _B and the roller target current I _R from the beginning of use It was set to 20 μA, which was larger than the example. The cleaning performance evaluation method and evaluation criteria are the same as the above-described evaluation method and evaluation criteria from which the evaluation results of FIG. 4 were obtained.

  As shown in Table 1, in the comparative example, the cleaning failure occurs at the 35,000th sheet, but as shown in Table 2, the occurrence of the cleaning failure can be delayed up to the 50000th sheet in this embodiment. This is considered due to the following reasons.

First, in the comparative example, since the current value flowing through the conductive brush 31 and the charging roller 32 is 20 μA from the beginning of use, the deterioration of energization of the conductive brush 31 and the charging roller 32 easily proceeds. Therefore, the value of the bias applied to the conductive brush 31 reaches 4000 V that is the upper limit voltage of the first cleaning power supply 50 at the 20000th sheet. Further, the value of the bias applied to the charging roller 32 reaches 4000 V, which is the upper limit voltage of the second cleaning power supply 60, at the 25000th sheet. In the present embodiment and the comparative example, after the outputs of the first and second cleaning power supplies 50 and 60 reach the upper limit voltage, the upper limit voltage is applied to the conductive brush 31 and the charging roller 32. Then, after reaching the upper limit voltage, the flow brush target current value I _B and the roller target current value I _R of 20μA for the output of the power supply is insufficient, and lowered current. Further, when the electrical resistance of the conductive brush 31 and the charging roller 32 continues to increase and the current flowing through the conductive brush 31 drops to 14 μA and the current flowing through the charging roller 32 to 16 μA at the 35000th sheet, a cleaning failure occurs. End up.

On the other hand, in this embodiment, the cleaning bias adjustment operation is executed when calibration is executed for every 1000 printed sheets. Then, the charging performance of the temporary collecting performance and the charging roller 32 of the conductive brush 31 so as to use the initial substantially the same, optimization of the brush target current I _B and the roller target current I _R is performed. Therefore, as compared with Comparative Example, it is possible to suppress the energization degradation for it is possible to reduce the brush target current value I _B and the roller target current value I _R of initial use, the conductive brush 31 and the charging roller 32. Thereafter, the value of the bias applied to the conductive brush 31 reaches 4000 V which is the upper limit voltage of the first cleaning power supply 50 at the 35,000th sheet. The value of the bias applied to the charging roller 32 reaches 4000 V, which is the upper limit voltage of the second cleaning power supply 60, at the 4th sheet. Finally, if the current flowing through the conductive brush 31 drops to 14 μA and the current flowing through the charging roller 32 to 17 μA at the 50,000th sheet, cleaning failure occurs.

  In this embodiment, the number of prints until the occurrence of a cleaning failure can be increased from 35,000 sheets in the comparative example to 50000 sheets. In other words, in this embodiment, good cleaning of the secondary transfer residual toner on the intermediate transfer belt 20 can be maintained for a longer period than before. Further, in this embodiment, it is possible to reduce the necessity of increasing the upper limit output of the first and second cleaning power supplies 50 and 60, which is advantageous in terms of downsizing and cost reduction of the apparatus. In this embodiment, since the temporary collection performance of the conductive brush 31 and the charging performance of the charging roller 32 are measured using the calibration image pattern, it is not necessary to form a dedicated image pattern, and the toner The time required for consumption and adjustment can be reduced.

  As described above, in this embodiment, the image forming apparatus 100 includes the control unit 150 that adjusts the cleaning bias applied to the cleaning members 31 and 32 from the power sources 50 and 60 to clean the toner on the intermediate transfer member. The control means 150 executes the following adjustment operation. That is, the predetermined toner image formed on the intermediate transfer member is cleaned by the cleaning members 31 and 32. Further, information regarding the toner amount of the predetermined toner image cleaned by the cleaning members 31 and 32 is acquired from the result of detecting the toner of the predetermined toner image on the intermediate transfer member by the detection unit 9. Based on the information, the cleaning bias is adjusted so that the amount of toner of the predetermined toner image cleaned by the cleaning members 31 and 32 approaches a predetermined reference value. In the present embodiment, the predetermined reference value is the amount of toner of a predetermined toner image that is cleaned by the cleaning members 31 and 32 at the initial stage of use. In this embodiment, the control unit 150 uses the detection unit to detect the toner of a predetermined toner image discharged to the intermediate transfer body 20 after being collected by the first cleaning member (conductive brush) 31. The above information is acquired from the detected result. Further, in this embodiment, the control unit 150 determines the predetermined toner remaining on the intermediate transfer member without being transferred to the image carrier 2 after being charged by the second cleaning member (charging roller) 32. The above information is acquired from the result of detecting the toner of the image by the detecting means 9. In this embodiment, the predetermined toner image is formed on the intermediate transfer body 20 for adjustment of at least one adjustment item other than the cleaning bias. In this embodiment, the at least one adjustment item is image density and registration.

  As described above, according to the present exemplary embodiment, the bias applied to the conductive brush 31 and the charging roller 32 that electrostatically clean the toner on the intermediate transfer belt 20 according to changes in the electric resistance is a necessary and sufficient value. It becomes possible to adjust to. As a result, good cleaning of the toner on the intermediate transfer belt 20 can be continued for a longer period of time than before.

[Example 2]
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, in the image forming apparatus of the present embodiment, elements having the same or corresponding functions or configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

1. Outline of the present embodiment In the present embodiment, the lifetimes of the conductive brush 31 and the charging roller 32 are judged and notified to an operator such as a user before the occurrence of defective cleaning. A method for prompting the exchange of 32 will be described.

  In the present embodiment, when the cleaning bias adjustment operation described in the first embodiment is performed in general, sufficient conductive cleaning performance (typically substantially the same cleaning performance as in the initial use) cannot be satisfied. The life of the charging roller 32 is determined. Then, in the display device of the operation unit 200 (FIG. 1) of the image forming apparatus 100 or the display device of an external device such as a personal computer connected to the image forming apparatus 100 in a communicable manner, the conductive brush 31 and the charging roller 32 are provided. Information about the lifetime is notified to the operator. For example, it is possible to display a warning that the service life is near or a prompt for replacement. The notification method is not limited to display, and may be notified by voice, for example. As a result, it is possible to replace the conductive brush 31 and the charging roller 32 before the cleaning failure occurs, and the occurrence of the cleaning failure can be suppressed.

  The conductive brush 31 and the charging roller 32 may be individually detachable from the apparatus main body of the image forming apparatus 100, or may be a unit that can be integrally attached and detached. Further, at least one of the conductive brush 31 and the charging roller 32 may be integrally formed with other elements as a unit that can be attached to and detached from the apparatus main body of the image forming apparatus 100.

2. Life Detection Control Next, life detection control using the optical sensor 9 in the present embodiment will be described. FIG. 11 shows the flowchart.

  In FIG. 11, the operations from STEP 1 to STEP 5 are the same as the adjustment operations described in the first embodiment, and thus description thereof is omitted. Hereinafter, STEP 6 and after will be described.

  In STEP 6, the control unit 150 determines whether the outputs of the first and second cleaning power supplies 50 and 60 that apply biases to the conductive brush 31 and the charging roller 32 have reached the upper limit voltage, respectively. Here, it is determined whether or not the outputs of the first and second cleaning power supplies 50 and 60 have reached the upper limit voltage as a result of the adjustment operation one time before the current adjustment operation. If not, the next adjustment operation is performed as described in the first embodiment. If so, go to STEP7. In the present embodiment, the outputs of the first and second cleaning power supplies 50 and 60 both reach the upper limit voltage of 4000 V when the number of printed sheets is 45,000 (Table 3 described later).

Next, in STEP 7, the control unit 150 determines whether or not a desired cleaning performance can be satisfied. First, when the output of the second cleaning power 50 and 60 has reached the upper limit voltage, the brush target current I _B, even if the optimization of the roller target current I _R, increasing the current actually flowing Can not. Accordingly, the output of the optical sensor 9 in STEP 4 is relatively large (the amount of discharged toner is reduced), and the output of the optical sensor 9 in STEP 5 is relatively small (the amount of toner collected on the photosensitive drum 2a). Less). In this embodiment, when the output of the optical sensor 9 in STEP 4 is 20% larger than that in the initial stage of use and the output of the optical sensor 9 in STEP 5 is 20% smaller than that in the initial stage of use, there is a concern about the occurrence of defective cleaning. In this embodiment, it is determined whether or not the cleaning performance is satisfied after both the outputs of the first and second cleaning power supplies 50 and 60 reach the upper limit voltage. This is because the configuration may cause a cleaning failure in this case.

  More specifically, FIG. 12 shows the output of the optical sensor 9 similar to FIG. 9 in STEP 4 at the initial use and the 46000th sheet. In FIG. 12, an output (average output value) that is 20% larger than the initial use is shown as a life judgment line. FIG. 13 shows the output of the optical sensor 9 similar to FIG. 10 in STEP 5 at the initial use and the 47000th sheet. In FIG. 13, for the fourth rotation of the intermediate transfer belt 20, an output (average output value) that is 20% smaller than the initial use is shown as a life judgment line. The lifetime of the charging roller 32 is not limited to the determination based on the output of the optical sensor 9 for the fourth time, and may be the first time, the second time, or the third time.

  As shown in FIG. 12, with respect to the conductive brush 31, since the output of the optical sensor 9 exceeds the life judgment line at the 46000th sheet, it is assumed that the temporary collection performance is insufficient, and is judged to be the life. be able to. Further, as shown in FIG. 13, the charging performance of the charging roller 32 is insufficient at the 47000th sheet because the output of the optical sensor 9 at the fourth rotation number of the intermediate transfer belt 20 exceeds the life judgment line. It can be estimated that it is a lifetime. In this embodiment, when it is determined that both the conductive brush 31 and the charging roller 32 are at the end of their life based on the output of the optical sensor 9 in STEP 4 and STEP 5 of the current adjustment operation, the process proceeds to STEP 8. When it is determined that the conductive brush 31 or the charging roller 32 (normal charging roller 32 in the configuration of this embodiment) has not reached the end of its life, the next adjustment operation is performed in the same manner as described in the first embodiment. Do.

  Next, in STEP 8, the control unit 150 performs processing for notifying the user that both the conductive brush 31 and the charging roller 32 are near the end of their lives.

  The presence or absence of cleaning failure was confirmed when the above-described life detection control was performed (this example) and when it was not performed (example 1). Table 3 shows the results of this example. The results of Example 1 are as shown in Table 2 above.

  As shown in Table 2, in Example 1, cleaning failure occurred at the 50,000th sheet. In contrast, in this embodiment, the lifespans of the conductive brush 31 and the charging roller 32 are determined when the change from the output of the optical sensor 9 at the initial use is 20% or more. This assumes that there is a grace period of one month before replacement, and that the average number of prints per month is set to 3000 so that no cleaning failure occurs during that time. As a result, in this embodiment, as shown in Table 4, it is determined that both the conductive brush 31 and the charging roller 32 have reached the functional lifetime before the cleaning failure has occurred, and Users can be notified. Thereby, before a cleaning failure occurs, it is possible to give the user time to prepare the replacement conductive brush 31 and the charging roller 32 (or a unit including them).

  The lifetime determination timing (corresponding to the lifetime determination line with respect to the output of the optical sensor 9) is not limited to that of the present embodiment, and is appropriate for the configuration of the image forming apparatus to which the present invention is applied. What is necessary is just to set to a time.

  Further, in the present embodiment, the information about the lifetime is notified when it is determined that both the conductive brush 31 and the charging roller 32 have the lifetime, but the present invention is not limited to this. The life of each of the conductive brush 31 and the charging roller 32 may be determined independently, and information regarding the life may be notified independently.

  As described above, in this embodiment, the control unit 150 performs a process of notifying information on the lifetime of the cleaning members 31 and 32 in the following case. That is, by adjusting the cleaning bias in a direction in which the outputs of the power supplies 50 and 60 increase, the outputs of the power supplies 50 and 60 reach a predetermined output value, and the toner of the predetermined toner image to be cleaned by the cleaning members 31 and 32 is obtained. This is a case where the amount becomes a predetermined value or less. In the present embodiment, the predetermined output value is the upper limit output value of the power supplies 50 and 60, but is not limited to this, and the cleaning members 31 and 32 may not satisfy the desired cleaning performance. As an arbitrary output value obtained in advance. In the present embodiment, the predetermined value of the toner amount is a toner amount corresponding to a case where the detection result of the detection unit 9 changes by a predetermined value (20%) compared to the initial use. However, it is not limited to this.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, the lifetimes of the conductive brush 31 and the charging roller 32 can be determined, and the user can be made conductive before the cleaning failure occurs. The brush 31 and the charging roller 32 can be exchanged.

[Others]
As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned Example.

  In the above-described embodiment, the example in which the bias applied to both of the configurations having the conductive brush and the charging roller is adjusted has been described, but the present invention is not limited to such an embodiment. In the electrostatic cleaning method, the secondary transfer residual toner is charged to a polarity opposite to the normal charging polarity of the toner by using a single toner charging member (charging roller, charging brush, etc.), and then in the primary transfer portion. There is also a configuration in which the intermediate transfer member is transferred to the photosensitive member and collected. The electrostatic cleaning method uses a single temporary collection member (conductive brush, sponge roller, etc.) to temporarily collect secondary transfer residual toner during the image forming process, and this is used as an intermediate transfer body during the non-image forming process. There is also a configuration in which the ink is discharged and transferred to a photoconductor. The present invention can be applied to any of the above configurations as long as it has a cleaning member that electrostatically cleans the toner on the intermediate transfer member. In the former case, for example, the following adjustment operation can be performed. In the above-described embodiment, the toner of the image pattern for calibration was cleaned, and the charging performance when the toner discharged in the subsequent discharging process was charged by the toner charging member was measured using an optical sensor. On the other hand, the charging performance of the toner charging member when cleaning the toner of the image pattern for calibration can be measured using an optical sensor. Also in this case, normally, the toner of the image pattern for calibration that gradually decreases while rotating the intermediate transfer member a plurality of times is detected by the optical sensor, and the charging performance of the toner charging member is improved in the same manner as in the above-described embodiment. Can be measured. In the latter case, the temporary collection performance of the temporary collection member can be measured in substantially the same manner as in the above-described embodiment, except that the operation for measuring the charging performance of the toner charging member is not provided.

Further, the method of calculating the brush target current I _B, the roller target current I _R is not intended to be limited to those described in the above embodiments. Information regarding the amount of toner cleaned by the cleaning member may be acquired by detecting the toner on the intermediate transfer member by the detection unit.

  In the above-described embodiment, the cleaning bias is adjusted by changing the current value (target current value) of the power supply output. However, the present invention is not limited to this, and the voltage value (target voltage value) of the power supply output is not limited thereto. ) May be changed and adjusted. In the above-described embodiment, the cleaning bias is controlled with a constant current, but this may be controlled with a constant voltage.

  In the above-described embodiment, the calibration bias is adjusted using the calibration image pattern when performing calibration. However, the present invention is not limited to this. For example, a dedicated image pattern can be formed independently of the calibration image pattern in order to adjust the cleaning bias. Further, the operation of adjusting the cleaning bias can be performed at a timing independent of the execution of calibration.

  In the above-described embodiment, in order to discharge toner from the cleaning member, a positive / negative bias is applied to the cleaning member. However, the present invention is not limited to this. Only a bias having the same polarity as the charge polarity (typically normal charge polarity) of the toner collected by the cleaning member may be applied as desired according to the required discharge performance. In this case, ON / OFF of bias application may be repeated. Further, in some cases, the toner may be discharged by turning off the bias applied to the cleaning member.

  In the above-described embodiment, the intermediate transfer member is separated from the photosensitive member so that the toner can pass through the position corresponding to the primary transfer portion during the adjustment operation. However, the present invention is not limited to this. An electric field may be formed in the primary transfer portion in a direction that attracts toner to be passed through a position corresponding to the primary transfer portion from the photosensitive member side to the intermediate transfer member side. Similarly, in the above-described embodiment, the secondary transfer roller is separated from the intermediate transfer member so that the toner can pass through the position corresponding to the secondary transfer portion during the adjustment operation. However, the present invention is not limited to this. An electric field may be formed in the secondary transfer portion in a direction that attracts toner to be passed through a position corresponding to the secondary transfer portion from the secondary transfer roller side to the intermediate transfer member side.

DESCRIPTION OF SYMBOLS 1 Image formation part 2 Photosensitive drum 9 Optical sensor 20 Intermediate transfer belt 30 Belt cleaning apparatus 31 Conductive brush 32 Charging roller

Claims (12)

An image carrier for carrying a toner image;
Toner image forming means for forming a toner image on the image carrier;
A rotatable intermediate transfer member that conveys a toner image that has been primarily transferred from the image carrier in a primary transfer unit in order to perform secondary transfer to a recording material in a secondary transfer unit;
A cleaning member that contacts the intermediate transfer member downstream of the secondary transfer unit and upstream of the primary transfer unit in the rotation direction of the intermediate transfer member and cleans the toner on the intermediate transfer member;
A power source for applying a bias to the cleaning member;
Detecting means for detecting toner on the intermediate transfer member;
Control means for adjusting a cleaning bias applied to clean the toner on the intermediate transfer member from the power source to the cleaning member;
Have
The control unit causes the predetermined toner image formed on the intermediate transfer member to be cleaned by the cleaning member, and information on the toner amount of the predetermined toner image cleaned by the cleaning member is acquired by the detection unit. Obtained from the result of detecting the toner of the predetermined toner image on the intermediate transfer body, and based on the information, the amount of toner of the predetermined toner image cleaned by the cleaning member approaches a predetermined reference value. An image forming apparatus, wherein the cleaning bias is adjusted.   The image forming apparatus according to claim 1, wherein the predetermined reference value is an amount of toner of the predetermined toner image cleaned by the cleaning member in an initial use.   The control unit obtains the information from a result of detection by the detection unit of toner of the predetermined toner image discharged from the cleaning member to the intermediate transfer member after being collected by the cleaning member. The image forming apparatus according to claim 1 or 2.   The control means detects the toner of the predetermined toner image remaining on the intermediate transfer member without being transferred from the intermediate transfer to the image carrier in the primary transfer unit after being charged by the cleaning member. The image forming apparatus according to claim 1, wherein the information is acquired from a result detected by a unit.   The control means adjusts the cleaning bias in a direction in which the output of the power supply increases, whereby the output of the power supply reaches a predetermined output value, and the amount of toner of the predetermined toner image to be cleaned by the cleaning member 5. The image forming apparatus according to claim 1, wherein a process of notifying information on a life of the cleaning member is performed when the value becomes equal to or less than a predetermined value. 6. The cleaning member includes a first cleaning member disposed on the upstream side in the rotation direction of the intermediate transfer member, and a second cleaning member disposed on the downstream side, and the cleaning power source includes the first cleaning member. Having first and second power supplies for applying a bias to the first and second cleaning members,
The control means acquires first and second information regarding the amount of toner of the predetermined toner image cleaned by the first and second cleaning members as the information, and based on the first information. Adjusting the cleaning bias applied to the first cleaning member so that the amount of toner of the predetermined toner image cleaned by the first cleaning member approaches the first predetermined reference value, The cleaning applied to the second cleaning member such that the amount of toner of the predetermined toner image cleaned by the second cleaning member based on the second information approaches the second predetermined reference value. The image forming apparatus according to claim 1, wherein the bias is adjusted.   The first predetermined reference value is an amount of toner of the predetermined toner image that is cleaned by the first cleaning member in an initial use, and the second predetermined reference value is the first reference value in the initial use. The image forming apparatus according to claim 6, wherein the amount of toner in the predetermined toner image is cleaned by two cleaning members.   The control means is configured to detect the first toner image discharged from the first cleaning member to the intermediate transfer member after being collected by the first cleaning member, based on a result of detection by the detection means. The intermediate transfer member without being transferred from the intermediate transfer member to the image carrier in the primary transfer unit after being discharged from the first cleaning member and charged by the second cleaning member. The image forming apparatus according to claim 6, wherein the second information is acquired from a result of detecting the toner of the predetermined toner image remaining on the detection unit by the detection unit.   The control means adjusts the cleaning bias in a direction in which the outputs of the first and second power sources increase, so that the outputs of the first and second power sources reach predetermined output values, respectively. 1. When the amount of toner of the predetermined toner image to be cleaned by the first and second cleaning members is equal to or less than a predetermined value, a process for notifying information on the lifetime of the first and second cleaning members is performed. The image forming apparatus according to claim 6, wherein the image forming apparatus is an image forming apparatus.   10. The predetermined toner image is formed on the intermediate transfer body for adjustment of at least one adjustment item other than the cleaning bias. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the control unit adjusts the cleaning bias by changing a current value or a voltage value of an output of the power source.   The image forming apparatus according to claim 1, wherein the detection unit is an optical sensor.

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