Image forming apparatus

Abstract

The present disclosure relates to an image forming apparatus. The image forming apparatus includes an image bearing member, a brush, and a controller. The controller controls so that, in a case where a region of the image bearing member in the conveyance direction in which the recording material is held is a first region and a region of the image bearing member in the conveyance direction in which the recording material is not held is a second region in a state where a trailing end of the recording material is held at the transfer portion in the conveyance direction, a first potential difference formed between a surface potential formed on the second region when the second region reaches the brush based on first information and a brush voltage is different from a second potential difference formed between the surface potential formed on the second region and the brush voltage based on second information.

Description

Technical Field

[0001] This disclosure relates to an image forming apparatus, such as a laser printer, copier, and fax machine, which obtains a recorded image by transferring a toner image formed electrophotographically on an image carrier member to a recording material. Background Technology

[0002] Electrophotographic systems are known as image recording systems used in image forming apparatuses such as printers and copiers. In an electrophotographic system, an electrostatic latent image is formed on a photosensitive drum (hereinafter referred to as the drum) using a laser beam through an electrophotographic process, and a toner image is formed by developing the electrostatic latent image with a charged color material (hereinafter referred to as toner). The toner image is then transferred to a recording material and fixed for image formation. To reduce the size of image forming apparatuses, cleaner-free systems have recently been discussed. A cleaner-free system refers to a system that removes and collects toner residue on the drum surface after the transfer process by cleaning the toner during development in the developing unit, and reuses the collected toner.

[0003] For the aforementioned cleanerless system, since paper dust adheres to the photosensitive drum during the transfer to the recording material, the lack of a cleaning unit that is normally deployed on the photosensitive drum will cause image defects.

[0004] In view of this, Japanese Patent Application Publication No. 2003-271030 discusses a configuration in which a fixed brush is deployed downstream of the transfer section and upstream of the charged section in the rotation direction of the photosensitive drum to collect paper dust adhering to the photosensitive drum during the transfer process.

[0005] However, the configuration discussed in Japanese Patent Application Publication No. 2003-271030 raises the following problems. When the toner is new and not sufficiently charged at the developing section due to friction, as an initial characteristic of the toner, many atomized toners develop on the non-image areas of the drum. Most of these atomized toners have a polarity opposite to the normal polarity. As the number of printed sheets increases after the initial use of the new toner, and the toner's charge stabilizes, the proportion of the normal polarity toner in the atomized toner increases.

[0006] Since the cleanerless system discussed in Japanese Patent Application Publication No. 2003-271030 does not use a cleaner, some of the toner remaining on the drum surface after the transfer process accumulates on the brush. It has been found that, in the initial stage of using a new toner, the polarity of the toner accumulated on the brush also changes with the aforementioned change in the polarity of the atomized toner.

[0007] As the polarity of the toner accumulated on the brush changes, the electrostatic sensitivity of the toner discharged from the brush changes due to variations in drum potential. Therefore, image defects can occur due to the toner inadvertently transferring from the brush to the drum. Summary of the Invention

[0008] This disclosure relates to an image forming apparatus including a brush in contact with a photosensitive drum, wherein image defects caused by toner accumulated on the brush are prevented.

[0009] According to one aspect of this disclosure, an image forming apparatus includes: a rotatable image carrier member; a charging member configured to charge the surface of the image carrier member at a charged portion opposite to the surface of the image carrier member; a developing member configured to supply toner charged to its normal polarity to the surface of the image carrier member; a transfer member configured to contact the image carrier member to form a transfer portion, and to hold and transport recording material at the transfer portion and transfer the toner supplied to the image carrier member to the recording material; a transfer voltage applying unit configured to apply a transfer voltage having a polarity opposite to the normal polarity to the transfer member; a brush configured to contact the surface of the image carrier member downstream of the transfer portion and upstream of the charged portion in the rotation direction of the image carrier member to form a brush portion; a brush voltage applying unit configured to apply a brush voltage of normal polarity to the brush; a storage unit configured to store information about the use of toner; and a control unit configured to control the transfer voltage applying unit and the brush voltage applying unit, wherein, when the toner is supplied to the image carrier member... After the toner on the surface of the image carrier member is transferred to the recording material at the transfer section, the developing member is configured to collect the toner remaining on the surface of the image carrier member. In a situation where the leading edge or trailing edge of the recording material in the transport direction of the recording material is clamped at the transfer section, and the area at the transfer section where the image carrier member in the transport direction of the recording material is clamped in a direction perpendicular to the transport direction is a first region, and the area at the transfer section where the image carrier member in the transport direction of the recording material is not clamped in a direction perpendicular to the transport direction is a second region, the control unit is configured to execute control such that a first potential difference formed between the surface potential and the brush voltage in the second region when the second region reaches the brush section, based on first information stored in the storage unit and different from the first information, is different from the second potential difference formed between the surface potential and the brush voltage in the second region when the second region reaches the brush section.

[0010] Further features of this disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0011] Figure 1 This is an explanatory diagram illustrating an image forming apparatus according to a first exemplary embodiment.

[0012] Figure 2 This is a schematic block diagram illustrating the control mode of the main part of the image forming apparatus according to a first exemplary embodiment.

[0013] Figure 3A and 3B This is a cross-sectional view of the brush according to a first exemplary embodiment.

[0014] Figure 4 This is a diagram illustrating the electrostatic movement of toner caused by drum potential and brush voltage according to a first exemplary embodiment.

[0015] Figure 5 This is a graph illustrating the change in atomization characteristics depending on the cumulative amount of printing sheet after the use of a new toner under new conditions according to a first exemplary embodiment.

[0016] Figure 6 This is a diagram illustrating the roller gap region as the recording material passes through the transfer roller gap portion according to a first exemplary embodiment.

[0017] Figure 7 It is a cross-sectional view of the transfer section as the recording material passes through the transfer section according to a first exemplary embodiment, and a graph showing the relationship between the drum potential and the brush voltage after transfer.

[0018] Figure 8A and 8B This is a diagram illustrating the drum potential near the trailing edge of the recording material according to a first exemplary embodiment and the toner discharge from the brush.

[0019] Figure 9A and 9B It is a diagram illustrating the cumulative quantity of printed sheets, the transition of atomized toner, and the control of the trailing edge voltage of the recording material according to a first exemplary embodiment.

[0020] Figure 10A and 10B This is a graph illustrating the relationship between the transfer voltage and the drum potential according to a first exemplary embodiment.

[0021] Figure 11 This is a diagram illustrating the amount of developing roller used and the movement of atomized toner according to a second exemplary embodiment.

[0022] Figure 12A and 12B This is a diagram illustrating the amount of developing roller used, the movement of atomized toner, and the control of the trailing edge voltage of the recording material according to a second exemplary embodiment.

[0023] Figure 13 This is an explanatory diagram illustrating an image forming apparatus according to a third exemplary embodiment.

[0024] Figure 14A and 14B This is a diagram illustrating the amount of developing roller used, the movement of atomized toner, and the control of the trailing edge voltage of the recording material according to a third exemplary embodiment. Detailed Implementation

[0025] Exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The dimensions, materials, shapes, and relative arrangements of the components described in the exemplary embodiments may be appropriately varied depending on the configuration of the apparatus to which the exemplary embodiments are applied and various conditions. In other words, the following exemplary embodiments are not intended to limit the scope of the present disclosure.

[0026] 1. Image forming apparatus

[0027] Figure 1 The illustration shows a schematic configuration of an image forming apparatus 100 according to a first exemplary embodiment of the present disclosure.

[0028] The image forming apparatus 100 according to this exemplary embodiment is a monochrome laser beam printer that uses a cleaner-free contact system with an electrified system.

[0029] The image forming apparatus 100 according to this exemplary embodiment includes a cylindrical photosensitive member, namely, a photosensitive drum 1, which serves as an image carrying member. A charged roller 2, serving as a charging unit, and a developing device 3, serving as a developing unit, are deployed near the photosensitive drum 1. Figure 1 In this setup, the exposure unit 4, which serves as the exposure unit, is located between the charged roller 2 and the developing unit 3 in the rotational direction of the photosensitive drum 1. The transfer roller 5, which serves as the transfer unit, is pressed onto the photosensitive drum 1.

[0030] According to this exemplary embodiment, the photosensitive drum 1 is a negatively charged organic photosensitive component. This photosensitive drum 1 includes a photosensitive layer located on an aluminum drum-shaped substrate, and a drive motor (drive unit) 110 serving as a drive unit. Figure 2 The drive rotates at a predetermined processing speed in the direction of the arrow (clockwise) in the figure. In this exemplary embodiment, the processing speed corresponds to the circumferential speed (surface movement speed) of the photosensitive drum 1, which is 140 mm / sec. The outer diameter of the photosensitive drum 1 is 24 mm.

[0031] The charged roller 2, acting as a charged component, contacts the photosensitive drum 1 with a predetermined pressure contact force and is driven to rotate on the photosensitive drum 1 while forming a charged portion. The charged voltage power supply 120 serves as the charged voltage application unit. Figure 2A desired charging voltage is applied to the charging roller 2, thereby uniformly charging the surface of the photosensitive drum 1 to a predetermined potential. In this exemplary embodiment, the surface of the photosensitive drum 1 is charged to a negative polarity by the charging roller 2. During the charging process, a charging voltage power supply 120, which serves as a charging voltage application unit, applies a predetermined charging voltage to the charging roller 2. In this exemplary embodiment, during the charging process, a negative polarity DC voltage is applied to the charging roller 2 as the charging voltage. The surface of the photosensitive drum 1 is thus uniformly charged to a dark potential Vd. More specifically, the charging roller 2 charges the surface of the photosensitive drum 1 by using discharges that occur upstream and downstream of the contact portion with the photosensitive drum in the rotational direction of the photosensitive drum 1 in at least one of the small gaps between the charging roller 2 and the photosensitive drum 1. In the following description, the contact portion between the charging roller 2 and the photosensitive drum 1 in the rotational direction of the photosensitive drum 1 is assumed to be the charged portion.

[0032] In this exemplary embodiment, the exposure device 4, used as the exposure unit, is a laser scanner device. The exposure device 4 outputs a laser corresponding to image information input from an external device such as a host computer, and uses this laser to scan and expose the surface of the photosensitive drum 1. This exposure forms an electrostatic latent image (electrostatic image) on the surface of the photosensitive drum 1 based on the image information. In this exemplary embodiment, the exposure by the exposure device 4 reduces the dark potential Vd formed on the surface of the photosensitive drum 1 by uniform charging to a bright potential Vl in absolute value. Here, the position of the photosensitive drum 1 exposed by the exposure device 4 in the rotational direction of the photosensitive drum 1 is referred to as the exposure portion (exposure position). The exposure device 4 is not limited to a laser scanner device. For example, an array of light-emitting diodes (LEDs) including a plurality of LEDs arranged along the longitudinal direction of the photosensitive drum 1 can be used.

[0033] In this exemplary embodiment, a contact developing system is used as the developing system. The developing apparatus 3 includes a developing roller 31 serving as a developing component and a developing agent carrying component, a toner supply roller 32 serving as a developing agent supply unit, a developing agent receiving chamber (developing agent container, developing agent receiving unit) 33 for containing toner, and a developing scraper 34.

[0034] The toner supplied from the developer chamber 33 to the developing roller 31 by the toner supply roller 32 is charged to a predetermined polarity through the scraper roller gap, which serves as the contact portion between the developing roller 31 and the developing scraper 34. At the developing section, the toner carried on the developing roller 31 moves from the developing roller 31 to the photosensitive drum 1 according to an electrostatic image. Here, the developing section refers to the contact portion between the developing roller 31 and the photosensitive drum 1 in the rotational direction of the photosensitive drum 1. In this exemplary embodiment, the developing roller 31 and the photosensitive drum 1 are always in contact with each other. In this exemplary embodiment, the developing roller 31 is driven to rotate counterclockwise, causing the photosensitive drum 1 and the developing roller 31 to move in the forward direction at the developing section. As in this exemplary embodiment, the drive motor 110 used as the drive unit for driving the developing roller 31 may be a main motor 110 shared with the drive unit of the photosensitive drum 1. Alternatively, the photosensitive drum 1 and the developing roller 31 may be rotated by corresponding different drive motors, such as a photosensitive drum drive unit and a developing roller drive unit. During development, the developing voltage power supply 140, which serves as the developing voltage application unit, is used... Figure 2 A predetermined developing voltage is applied to the developing roller 31. The control unit 200 controls the application of a -400V DC voltage, Vdc, from the developing voltage power supply 140 to the core of the developing roller 31 during image formation operation, in which the developing roller 31 and the photosensitive drum 1 rotate in contact with each other. During image formation, the electrostatic force caused by the potential difference between the developing voltage Vdc = -400V and the image formation potential (brightness potential) Vl = -100V causes the toner carried on the developing roller 31 to develop in the portion of the photosensitive drum 1 having the image formation potential V1.

[0035] In the following description, a potential or applied voltage with a large absolute value (e.g., -1350V relative to -800V) of negative polarity will be referred to as a high potential. A potential or applied voltage with a small absolute value (e.g., -400V relative to -800V) of negative polarity will be referred to as a low potential. The reason is that in this exemplary embodiment, a toner with negative charging capability is assumed to be used as a reference.

[0036] In this exemplary embodiment, voltage is expressed as a potential difference from ground potential (0V). Since the developing voltage applied to the core of the developing roller 31, the developing voltage Vdc = -400V is therefore interpreted as having a potential difference of -400V from ground potential. The same applies to charged voltage and transfer voltage.

[0037] In this exemplary embodiment, a toner with the same polarity as the photosensitive drum 1 (negative polarity in this exemplary embodiment) is attached to the exposure surface (image portion) of the image forming portion of the photosensitive drum 1, wherein the absolute value of the potential is reduced by exposure after uniform charging treatment. This development system is called a reverse development system. In this exemplary embodiment, the normal polarity of the toner's charge polarity during development is negative. Although a single-component nonmagnetic contact development method is used in this exemplary embodiment, this disclosure is not limited thereto. A two-component nonmagnetic contact development method, a non-contact development method, or a magnetic development method can be used. A two-component nonmagnetic contact development method refers to a method that uses a two-component developer comprising a nonmagnetic toner and a magnetic carrier as the developer, and the developer (magnetic brush) carried on a developer carrier member is in contact with the photosensitive drum 1 for development. A non-contact development method refers to a method that performs development by discharging the toner from the developer carrier member opposite the photosensitive member to the photosensitive member in a non-contact manner. Magnetic development method refers to a method of performing development by magnetically carrying a magnetic toner on a developer carrier member, the developer carrier member including a built-in magnet serving as a magnetic field generating unit and being opposite to a photosensitive member in a contact or non-contact manner. In this exemplary embodiment, a toner having an average median particle size of 6 μm and a negative polarity as its normal polarity is used.

[0038] The transfer roller 5, used as a transfer component, suitably comprises an elastic member made of sponge rubber such as polyurethane rubber, ethylene propylene diene monomer (EPDM) rubber, and nitrile butadiene rubber (NBR). The transfer roller 5 presses against the photosensitive drum 1 to form a transfer portion where the photosensitive drum 1 and the transfer roller 5 press against each other. During transfer, a transfer voltage power supply 160, serving as a transfer voltage application unit, (… Figure 2 A predetermined transfer voltage is applied to the transfer roller 5. In this exemplary embodiment, during the transfer, a DC voltage with a polarity opposite to the normal polarity of the toner (positive polarity in this exemplary embodiment) is applied to the transfer roller 5 as the transfer voltage.

[0039] By means of the electric field formed between the transfer roller 5 and the photosensitive drum 1, the toner image is electrostatically transferred from the photosensitive drum 1 to the recording material (hereinafter referred to as the sheet) S.

[0040] The recording material S stored in the cartridge 6 is fed synchronously by the feeding unit 7 with the arrival time of the toner image formed on the photosensitive drum 1 at the transfer section. The recording material S passes between the registration roller pairs 8 and is transported to the transfer section. The toner image formed on the photosensitive drum 1 is transferred to the recording material S by the transfer roller 5, and a predetermined transfer voltage is applied to the transfer roller 5 by the transfer voltage power supply 160, which serves as a transfer voltage application unit.

[0041] After the toner image is transferred, the recording material S is conveyed to the fixing device 9. The fixing device 9 is a film heating fixing device, including a fixing heater (not shown), a fixing film 91 containing a built-in thermistor (not shown) for measuring the temperature of the fixing heater, and a pressure roller 92 pressing on the fixing film 91. The recording material S is heated and pressurized to fix the toner image, and is discharged outside the image forming apparatus 100 by the discharge roller pair 12.

[0042] In this exemplary embodiment, a brush 10 (brush component) serving as a paper dust removal component is deployed to contact the photosensitive drum 1 downstream of the transfer section. As the recording material S passes through the transfer section, the brush 10 removes the paper dust transferred to the photosensitive drum 1 from the photosensitive drum 1.

[0043] In this exemplary embodiment, a pre-exposure device 13, serving as a pre-charged exposure unit, is deployed downstream of the contact portion between the photosensitive drum 1 and the brush 10 and upstream of the charged portion in the rotational direction of the photosensitive drum 1 to homogenize the potential of the photosensitive drum 1 after transfer. In this exemplary embodiment, an LED (not shown) deployed on the side surface of the main body operates as the pre-exposure device 13, such that the photosensitive drum 1 is illuminated in a direction parallel to the main scanning direction of the photosensitive drum 1. A light guide, serving as a light guide member, may also be used to reduce illumination non-uniformity in the main scanning direction.

[0044] Transfer residue toner remaining on the photosensitive drum 1 and not transferred to the recording material S passes through the contact portion with the brush 10. After the potential of the photosensitive drum 1 is homogenized by the pre-exposure device 13, the charged roller 2 recharges the transfer residue to negative polarity at the charged portion using discharge. As the photosensitive drum 1 rotates, the transfer residue toner, recharged to negative polarity by the charged roller 2, reaches the developing portion. The transfer residue toner that has reached the developing portion moves to the surface of the developing roller 31 and is collected in the developer container 33.

[0045] 2. Control Unit

[0046] Next, the control unit 200 will be described. Figure 2This is a schematic control block diagram illustrating the main control mode of the image forming apparatus 100 according to this exemplary embodiment. The controller 202 transmits / receives various types of electrical information to / from the host device and centrally controls the image forming operation of the image forming apparatus 100 via interface 201 using the control unit 200 based on a predetermined control program and reference table. The control unit 200 includes a central processing unit (CPU) 155 and a memory 154 serving as a storage unit. The CPU 155 is the central element performing various types of computational processing, and the memory 154 includes storage elements such as read-only memory (ROM) and random access memory (RAM). The memory 154 stores information about the use of toners, which is a feature of this exemplary embodiment. The RAM stores sensor detection results, counter counts, and calculation results. The ROM stores the control program and a data table obtained in advance through experiments. Various control targets, sensors, and counters of the image forming apparatus 100 are connected to the control unit 200. The control unit 200 controls a predetermined image forming sequence by controlling the transmission and reception of various electrical information signals and the driving timing of various components.

[0047] For example, the control unit 200 controls the applied voltage and exposure amount of the live voltage power supply 120, the developing voltage power supply 140, the exposure device 4, the transfer voltage power supply 160, the pre-exposure device 13, and the brush power supply 130. The control unit 200 also controls the main motor (drive unit) 110. The image forming apparatus 100 forms an image on the recording material S based on an electrical image signal input from the host device to the controller 202. Examples of host devices include image readers, personal computers, fax machines, and smartphones. The image forming operation and other controls according to this exemplary embodiment will now be described.

[0048] 3. Brush Construction

[0049] The image forming apparatus 100 includes a brush 10 that contacts the surface of a photosensitive drum 1 at a brush portion. In a first exemplary embodiment, the brush 10 collects paper dust adhering to the surface of the photosensitive drum 1. The brush 10 contacts the surface of the photosensitive drum 1 to form a contact portion downstream of the transfer portion and upstream of the charged portion in the rotational direction of the photosensitive drum 1.

[0050] Figure 3A This is a cross-section of the brush 10 in its independent state (not in contact with the photosensitive drum 1) taken along an imaginary plane perpendicular to the rotation axis of the photosensitive drum 1. Figure 3B This is a diagram showing the aforementioned cross-section of the brush 10 in contact with the photosensitive drum 1.

[0051] like Figure 3A and 3BAs shown, the brush 10 is a pile fabric comprising a thread portion 11 and a base fabric 11b supporting the thread portion 11. The thread portion 11 includes multiple conductive nylon threads 11a serving as multiple bristle members that contact and slide on the surface of the photosensitive drum 1. The threads 11a extend from the base fabric 11b in a vertical direction when not in contact with the photosensitive drum 1. The threads 11a are evenly arranged on the base fabric 11b. The brush 10 is positioned to contact the photosensitive drum 1 downstream of the transfer portion and upstream of the charged portion in the direction of rotation of the photosensitive drum 1.

[0052] The brush 10 is positioned such that its longitudinal direction is parallel to the rotation axis of the photosensitive drum 1. Except... In addition, wire 11a can also be made of rayon, acrylic, and polyester materials. Although a conductive wire is used as wire 11a in the first exemplary embodiment, an insulated wire can be used. Wire 11a can be any wire-like material, and is not limited to a wire-like material formed by twisting fibers.

[0053] like Figure 3A As shown, when the brush 10 is in its independent state, i.e., in its natural state (without external bending force acting on the line 11a), the distance from the base fabric 11b to the end of the line 11a is L1. The brush 10 is fixed by fixing the base fabric 11b to a support member (not shown) located at a predetermined position on the image forming apparatus 100 using a fixing member such as double-sided tape. The brush 10 is fixed such that the minimum distance L2 from the base fabric 11b of the brush 10 fixed to the support member to the surface of the photosensitive drum 1 is less than the length L1 of the line 11a in the independent state. The gap between the support member and the photosensitive drum 1 is constant. The difference between L2 and L1 is called the amount of intrusion of the brush 10 relative to the photosensitive drum 1. Since L2 < L1, when the brush 10 is in use (i.e., in the state where the brush 10 is fixed to the image forming apparatus 100 and in contact with the surface of the photosensitive drum 1), the end of the line 11a bends in the rotational direction of the photosensitive drum 1, as shown. Figure 3B As shown in the diagram, the contact portion between the end of the upstream line 11a in the curved state and the surface of the photosensitive drum 1 is the upstream end of the contact area. The contact portion between the end of the downstream line 11a in the curved state and the surface of the photosensitive drum 1 is the downstream end of the contact area. The contact between the brush 10 and the surface of the photosensitive drum 1 refers to the state in which each line 11a contacts the surface of the photosensitive drum 1. Microscopically, the "contact area" includes the area between adjacent lines 11a where the surface of the photosensitive drum 1 and the brush 10 do not contact each other. The surface of the photosensitive drum 1 in the contact area and the brush 10 in contact with the surface of the photosensitive drum 1 form a contact portion.

[0054] The dimension of brush 10 in the longitudinal direction (in the direction parallel to the rotation axis of photosensitive drum 1) is set such that brush 10 contacts the entire image forming area (the area where toner image can be formed) of photosensitive drum 1 in the direction of rotation axis of photosensitive drum 1. The dimension of brush 10 in the transverse direction (in the direction parallel to the circumferential direction or the rotation direction of photosensitive drum 1) is appropriately set based on the lifespan of image forming apparatus 100 or processing cartridge.

[0055] The brush 10 is fixed in a constant position relative to the photosensitive drum 1 and slides on the surface of the photosensitive drum 1 as the photosensitive drum 1 moves (rotates). The brush 10 captures (collects) adhering substances such as paper dust transferred from the recording material S to the photosensitive drum 1 at the transfer section, thereby reducing the amount of paper dust that moves to the charged section and the developing section downstream of the brush 10 in the moving direction (rotation direction) of the photosensitive drum 1.

[0056] In the first exemplary embodiment, the length L1 of the line 11a of the brush 10 in its natural state is 4.8 mm. The penetration of the brush 10 relative to the photosensitive drum 1 is 1.5 mm (L2 = 3.3 mm). The brush 10 has a lateral length L3 of 5 mm and a longitudinal length of 230 mm. The fineness (thickness) of the line 11a is 2 denier (expressing the thickness of 9000 meters of line weighing 2 grams) and the density is 240 kF / inch. 2 (kF / inch 2This is a unit of brush density, indicating the number of filaments per square inch. The filaments 11a are arranged almost uniformly from the bottom of the base fabric 11b to the tip, which is the contact portion with the surface of the photosensitive drum 1. The lateral length of the brush 10 is merely an example and not limited to the foregoing. The greater the lateral length of the brush 10, the longer the brush 10 can collect paper dust. The longitudinal length of the brush 10 is merely an example and not limited to the foregoing. For example, the longitudinal length of the brush 10 can be set based on the maximum sheet width of the image forming apparatus 100. Moreover, the fineness of the filaments 11a of the brush 10 is merely an example and not limited to the foregoing. The fineness of the filaments 11a can be determined considering the permeability of paper dust. A brush 10 with too small a fineness has low adsorption capacity for paper dust, and paper dust may pass through. Paper dust that has passed through the brush 10 can interfere with the charging of the photosensitive drum 1 by the charged roller 2 and cause image defects. On the other hand, if the fineness of the filaments 11a of the brush 10 is too large, then toner and paper dust cannot be collected. This will cause the amount of attached toner to be uneven in the longitudinal direction of the charged roller 2, and will result in image defects due to uneven image density and insufficient charging in areas with attached paper dust. The density of the line 11a of the brush 10 is merely an example and is not limited to the foregoing. The density of the line 11a can be set with consideration for toner permeability and paper dust collection. If the density of the line 11a of the brush 10 is too high, the toner will stick due to low toner permeability, and the stuck toner will scatter and contaminate the interior of the image forming apparatus 100. If the density of the line 11a of the brush 10 is too low, then sufficient paper dust collection performance cannot be provided. In view of paper dust collection performance, the fineness and density of the line 11a are expected to be 1 to 6 denier and 150 to 350 kF / inch, respectively. 2 Given its long lifespan, the lateral length L3 of brush 10 is expected to be 3 mm or greater.

[0057] A brush power supply 130, which serves as a brush voltage application unit, is connected to the brush 10. During image formation, the brush power supply 130 applies a negative DC voltage as the brush voltage to the brush 10.

[0058] 4. Image output operation

[0059] The image forming apparatus 100 performs a series of operations to form an image on one or more recording materials S based on instructions from an external device (not shown) such as a personal computer to begin an image output operation (job). The job typically includes a pre-rotation step, an image forming step (printing step), a sheet spacing step (in the case of forming images on multiple recording materials S), and a post-rotation step. The image forming step includes forming an electrostatic image on the photosensitive drum 1, developing an electrostatic image (forming a toner image), transferring a toner image, and fixing a toner image. The period during which the image forming steps are performed is called the image forming period. During the image forming period, operations such as the formation of an electrostatic image, the formation of a toner image, the transfer of a toner image, and the fixing of a toner image are performed at correspondingly different times. The pre-rotation step is a step that performs preparation operations before the image forming step. The sheet spacing step is a step performed between the image forming step on the first recording material S and the image forming step on the second recording material S following the first recording material S when image forming operations are performed continuously on multiple recording materials (during continuous image forming). The post-rotation step is a step that performs a rearrangement operation (preparation operation) after the image forming step. The time period outside the image forming period, that is, the time period including the pre-rotation step, the sheet spacing step, and the post-rotation step, will be referred to as the non-image forming period. The preparatory rotation step, which performs the preparation operation when the image forming apparatus 100 is powered on or resumes from a sleep state, is also included in the non-image forming period.

[0060] 5. Control method in this exemplary embodiment

[0061] The control unit 200 is a control unit that centrally controls the operation of the image forming apparatus 100. The control unit 200 controls the transmission and reception of various electrical information signals and drives timing, and executes a predetermined image forming sequence. Various components of the image forming apparatus 100 are connected to the control unit 200. For example, in this exemplary embodiment, the power supply 120, the developing power supply 140, the transfer power supply 160, and the brush power supply 130 are connected to the control unit 200.

[0062] Next, in order to facilitate understanding of the problems to be described below and the control according to this exemplary embodiment, the basic control of various voltages, surface potentials formed on the photosensitive drum 1, and transfer voltage will be described.

[0063] In this exemplary embodiment, a charging voltage of -1350V is applied to the charging roller 2 to uniformly charge the surface of the photosensitive drum 1. This charges the photosensitive drum 1 to a dark area potential Vd or non-image area potential of -800V. Next, through exposure by the exposure apparatus 4, the dark area potential Vd formed by the uniform charging process is reduced in absolute value to an image area potential or bright area potential Vl. In this exemplary embodiment, the bright area potential Vl is -100V. Next, in this exemplary embodiment, a developing voltage of -400V Vdc is applied to the developing roller 31 to develop the portion having the bright area potential Vl. Furthermore, in this exemplary embodiment, a brush voltage of -400V is applied to the brush 10.

[0064] Next, the transfer control during the printing operation will be described. If a print job is input, the photosensitive drum 1 and the developing roller 31 are first driven to rotate, and the aforementioned electrical voltage and developing voltage are applied.

[0065] After the rotational speed and surface potential formed on the photosensitive drum 1 stabilize, the transfer voltage power supply 160 applies a positive voltage to the transfer roller 5. Here, the output voltage value from the transfer voltage power supply 160 is adjusted and sampled so that the current value flowing through the transfer roller 5, detected by a current detection circuit (not shown), converges to a target current value. The resistance detection voltage value V0 during the non-sheet passage is then calculated. The control unit 200 then switches to constant voltage control synchronously with the timing of the entry of the leading edge of the recording material S (referred to as the recording material leading edge) into the transfer section in the transport direction of the recording material S. This constant voltage control includes applying a voltage (recording material leading edge voltage), the value of which is determined by a calculation process that multiplies the resistance detection voltage value V0 by a predetermined coefficient.

[0066] Then, when the leading edge of the recording material has traveled a certain distance from the transfer section, the control unit 200 switches to constant current control. In this exemplary embodiment, the target current value for constant current control during sheet passage is 15 μA. During this constant current control interval, the resistance detection voltage value V1 during sheet passage is calculated. Next, the control unit 200 switches to constant voltage control at a predetermined time before the trailing edge of the recording material S (referred to as the recording material trailing edge) enters the transfer section in the transport direction of the recording material S. This constant voltage control includes applying a voltage (recording material trailing edge voltage), the value of which is determined by multiplying the resistance detection voltage value V1 by a predetermined coefficient. At the timing when the recording material trailing edge has traveled a predetermined distance from the transfer section, the recording material trailing edge voltage is switched to the sheet interval voltage. In the case of continuous sheet passage operations, the recording material leading edge voltage is applied again synchronously with the subsequent recording material leading edge, and the aforementioned control is repeated. After the transfer operation of the last image of the operation is completed by such operation, the post-rotation operation is performed and stopped.

[0067] In this exemplary embodiment, the sheet-to-sheet distance is 70 mm, which is shorter than the circumference of the photosensitive drum 1.

[0068] 6. Mechanism for dispensing toner from the brush

[0069] Next, to facilitate understanding of control according to this exemplary embodiment, the toner transfer operation from the brush 10 to the surface of the photosensitive drum 1, or the mechanism for discharging toner from the brush 10, will be described.

[0070] First, the accumulation of toner on brush 10 will be described. There are two types of toner that accumulate on brush 10: atomized toner and transfer residue toner. Atomized toner is a portion of the toner coated on the developing roller 31, which is transferred to the non-image potential portion (the portion with dark potential Vd) formed on the surface of the photosensitive drum 1. Transfer residue toner is the toner remaining on the surface of the photosensitive drum 1 after the toner developed in the image potential portion (the portion with bright potential Vl) is transferred to the recording material S at the transfer portion. The two types of toner differ in the amount and polarity ratio collected on brush 10, depending on the following factors: electrostatic factors due to the potential difference between the surface potential formed on the photosensitive drum 1 and the brush voltage, and physical factors due to the contact pressure of the lines 11a held in the gap between them.

[0071] For example, this exemplary embodiment employs an image forming apparatus 100 in which the brush voltage is set sufficiently lower than the non-image portion potential Vd and higher than the image portion potential Vl. Figure 4 As shown, if the surface potential formed on the photosensitive drum 1 is lower (smaller in absolute value) than the brush voltage, then the positively polarized toner tends to move towards the brush 10. Conversely, if the surface potential of the photosensitive drum 1 is higher (larger in absolute value), then the negatively polarized toner tends to electrostatically move towards the brush 10; the greater the potential difference, the more pronounced this tendency. However, the potential difference with the brush voltage is not the only determinable factor, because the surface potential of the photosensitive drum 1 entering the brush 10 after transfer varies depending on the difference between the potential Vl of the image portion and the potential Vd of the non-image portion, as well as the setting of the transfer voltage at the transfer portion.

[0072] Therefore, the two types of toners, the positively polarized toner and the negatively polarized toner, always accumulate on the brush 10, and the ratio depends on the polarity of the atomized toner and the transfer residue toner.

[0073] Next, the trend of the atomized toner at the developing portion according to this exemplary embodiment will be described. In order to examine the trend of the atomized toner at the developing portion of the image forming apparatus 100 according to this exemplary embodiment, the concentration (%) of the atomized toner on the surface of the photosensitive drum 1 is measured in the following manner.

[0074] First, the image forming apparatus 100 according to this exemplary embodiment is activated in the same manner as the printing operation. The desired latent image is set by setting the charging voltage and developing voltage to the conditions described above. Then, the rotation drive of the photosensitive drum 1 is stopped. After the rotation drive of the photosensitive drum 1 is stopped, polyester tape (manufactured by NICHIBAN Ltd., No. 5511) is attached to the surface of the photosensitive drum 1 between the developing section and the transfer section in the rotation direction of the photosensitive drum 1. The attached tape is peeled off to sample the atomized toner on the surface of the photosensitive drum 1. The atomized toner on the surface of the photosensitive drum 1 is sampled multiple times under different latent image settings, wherein the difference between the surface potential of the photosensitive drum 1 at the back contrast Vback or developing section and the developing voltage is appropriately set from 50V to 500V in 50V steps. The tape from which the atomized toner has been sampled from the surface of the photosensitive drum 1 is attached to Xerox Vitality Multipurpose Paper (letter size, 20 lbs). The whiteness D1 (%) of the area where the strip is attached and the whiteness D2 (%) of the area where the strip is not attached were measured using a fogging meter (product name: REFLECTOMETER MODEL TC-6DS, manufactured by Tokyo Denshoku Co., Ltd.). From the measurements, "D2 (%) - D1 (%)" was calculated as the fogging toner concentration (%).

[0075] In this way, when the image forming apparatus 100 according to this exemplary embodiment is new, that is, when the toner is new, after printing a total of 30 sheets and after printing a total of 100 sheets, the concentration (%) of the atomized toner on the surface of the photosensitive drum 1 is measured.

[0076] Figure 5 The illustration shows the measurement results of the concentration (%) of the hazy toner on the surface of the photosensitive drum 1 of the image forming apparatus 100 according to this exemplary embodiment. Figure 5 As shown, in the new toner state corresponding to when the image forming apparatus 100 is new, the fogged toner on the surface of the photosensitive drum 1 increases with the increase of back contrast Vback. Therefore, it can be seen that fogging (hereinafter referred to as reverse fogging) caused by the toner (hereinafter referred to as inverted toner) being charged to a positive polarity opposite to the normal polarity of the toner easily occurs on the surface of the photosensitive drum 1. Figure 5 As shown, as the cumulative number of sheets printed by the image forming apparatus 100 increases, reverse fogging occurs less even under high back contrast (Vback). This is because if the conditions of the image forming apparatus 100 or the toner are closer to the new conditions, the proportion of toner not sufficiently charged to its normal polarity is higher, and such toner is more likely to become reverse toner due to the potential difference at the developing portion.

[0077] like Figure 5 As shown, when the image forming apparatus 100 is in a new state, it is unlikely that the toner atomization on the surface of the photosensitive drum 1 will increase under low back contrast Vback. In other words, it can be seen that atomization caused by the toner being charged to the negative polarity, which is the normal polarity (hereinafter referred to as normal atomization), is unlikely to occur on the surface of the photosensitive drum 1. Figure 5 As shown, it can also be seen that as the cumulative number of sheets printed by the image forming apparatus 100 increases, normal fogging becomes more likely to occur at the same Vback, within a range where Vback is below approximately 200V. This is because the longer the image forming apparatus 100 (i.e., the toner) is used, the more fully the toner is charged to its normal polarity, and toner reversal is less likely to occur due to the potential difference at the developing portion.

[0078] As described above, the closer the image forming apparatus 100 or the toner is to its initial state, the more likely reverse fogging is to occur and the less likely normal fogging is to occur. It can be seen that the longer the image forming apparatus 100 (i.e., the toner) is used, the less likely reverse fogging is to occur and the more likely normal fogging is to occur.

[0079] Transfer residue toners are thought to exhibit a similar trend in polarity reversal as atomized toners. Specifically, if the same transfer voltage is applied, transfer residue toners are more likely to reverse and contain a higher proportion of positively polarized toner when the toner conditions are closer to the new conditions. The likelihood of transfer residue toner reversal decreases as the cumulative number of printed sheets increases. In other words, negatively polarized toners become more likely to remain as the cumulative number of printed sheets increases.

[0080] When the image forming apparatus 100 is new, the polarity of the toner accumulated on the brush 10 changes with the aforementioned changes in the atomized toner and the transfer residue toner in the initial stage. Specifically, if the conditions of the image forming apparatus 100 are closer to the new conditions, the proportion of positive polarity toner accumulated on the brush 10 is higher. As the cumulative number of printed sheets increases, the proportion of negative polarity toner increases.

[0081] Next, the transfer (toner discharge) of the toner accumulated on the brush 10 to the surface of the photosensitive drum 1 will be described. In this exemplary embodiment, reference will be made to... Figure 6 and 7 The description describes the toner discharge caused by the change in surface potential of the photosensitive drum 1 when the trailing edge of the recording material S passes through the transfer section.

[0082] First, refer to Figure 6Describes the roller gap region when the trailing edge of the recording material S passes through the transfer portion (transfer roller gap portion) according to this exemplary embodiment. Figure 6 This is a cross-sectional view near the transfer roller gap portion when the trailing edge of the recording material S passes through the transfer roller gap portion. In this exemplary embodiment, the transfer roller gap region between the photosensitive drum 1 and the transfer roller 5 in the transport direction of the recording material S will be referred to as the first roller gap region (first region). The transfer roller gap region where no recording material S is inserted will be referred to as the second roller gap region (second region).

[0083] In this exemplary embodiment, whether the recording material S is inserted in the conveying direction of the recording material S is determined based on whether the recording material S exists in the longitudinal direction perpendicular to the conveying direction of the recording material S within the surface of the transfer roller gap.

[0084] like Figure 6 As shown, the second roller gap region is divided into a gap wall portion D formed at the end of the recording material S and a contact portion where the photosensitive drum 1 and the transfer roller 5 come into contact with each other.

[0085] Next, we will refer to Figure 7 Describe the relationship between the surface potential of the photosensitive drum 1 after transfer and the brush voltage when the recording material S passes through the transfer section. Figure 7 It is a diagram showing a cross-sectional view of the transfer section when the recording material S passes through the transfer section, and a diagram showing the relationship between the surface potential of the photosensitive drum 1 and the brush voltage after the transfer. Figure 7 The surface potential of the photosensitive drum 1 after transfer, as shown, indicates the potential during the constant current control interval when the sheet passes through and the potential during the interval of applying the recording material trailing edge voltage (recording material trailing edge voltage interval). During the interval of applying the recording material trailing edge voltage, at the timing of the recording material trailing edge passage, i.e., when the first roll gap region switches to the second roll gap region, the surface potential of the photosensitive drum 1 temporarily jumps to the negative polarity side. This is because the physical step difference at the trailing edge of the recording material S creates a small gap wall portion D between the surface of the photosensitive drum 1 and the transfer roller 5, where the surface potential of the photosensitive drum 1 is unlikely to decay locally. The surface potential of the photosensitive drum 1 after transfer, corresponding to the gap wall portion D, will be represented by Va.

[0086] During the voltage interval along the trailing edge of the recording material, a constant voltage is maintained to create a surface potential difference in the photosensitive drum 1 before and after the trailing edge of the recording material passes through the transfer section. This is because the resistance of the transfer section varies depending on the presence or absence of the recording material S. The recording material S transfers current from the photosensitive drum 1 to the transfer roller 5 through the subsequent contact section. The surface potential of the photosensitive drum 1 in the contact section therefore decreases. The post-transfer surface potential on the surface of the photosensitive drum 1 corresponding to the contact section will be represented by Vb.

[0087] The brush voltage applied to brush 10 will be represented by Vc.

[0088] In view of the foregoing, the discharge of toner from the brush 10 due to the change in surface potential of the photosensitive drum 1 will be described.

[0089] Figure 8A The diagram illustrates the potential relationship when the trailing edge of the recording material passes through the transfer section, and a small gap wall portion D exists between the surface of the photosensitive drum 1 and the transfer roller 5 due to the step difference of the recording material S. Figure 8A The illustration shows how toner is expelled from the region of surface potential Va formed by the presence of the gap wall portion D, where the surface potential of the photosensitive drum 1 is unlikely to decay, as it passes through the contact point with the brush 10.

[0090] Due to the potential difference VA (=Va-Vc) between the photosensitive drum 1 and the surface potential Va, which is locally higher than the brush voltage Vc, most of the positive polarity toner accumulated on the brush 10 is discharged. The discharged positive polarity toner then adheres to the charged roller 2, located downstream of the photosensitive drum 1 in the direction of rotation, and the charged roller 2 rotates temporarily while still coated with toner. Therefore, white stripe-like image defects (hereinafter referred to as transverse white stripes) appear during the rotation of the charged roller 2. The greater the potential difference VA on the negative polarity side (the higher the surface potential Va on the negative polarity side), the more toner is discharged from the brush 10, and the more severe the transverse white stripes become. The more positive polarity toner accumulates on the brush 10, the more toner is discharged onto the surface of the photosensitive drum 1.

[0091] Figure 8B The figure illustrates the potential relationship when the potential difference VB (=Vb-Vc) between the surface potential of the photosensitive drum 1 and the brush voltage is large after the trailing edge of the recording material S passes through the transfer section. Figure 8B The illustration shows how toner is expelled when the area of ​​the photosensitive drum 1 with a surface potential of Vb passes through the contact position with the brush 10. In the area of ​​the photosensitive drum 1 with a surface potential of Vb, most of the negative-polarity toner accumulated on the brush 10 is expelled. If too much toner that cannot be collected at the developing section is expelled, as in this exemplary embodiment, and the distance between the sheets is less than the outer perimeter of the photosensitive drum 1, then image defects (hereinafter referred to as leading-edge ejection) occur in the image transferred near the leading edge of the subsequent recording material S. The greater the potential difference VB on the positive side (the higher the surface potential Vb on the positive side), the more toner is expelled and the worse the leading-edge ejection becomes. The more negative-polarity toner accumulated on the brush 10, the more toner is expelled onto the surface of the photosensitive drum 1.

[0092] If the polarity ratio of the toner accumulated on brush 10 remains constant, the transfer voltage can be uniquely controlled to ensure that the photosensitive drum 1 has an optimal surface potential, preventing lateral white streaks or leading edge ejection. On the other hand, if the polarity ratio of the toner accumulated on brush 10 changes with the cumulative amount of printed sheet due to the aforementioned polarity change of the atomized toner, then the optimal surface potential of the photosensitive drum 1 will not change, preventing lateral white streaks or leading edge ejection. Therefore, it is necessary to control the potential difference between the surface potential of the photosensitive drum 1 and the brush voltage.

[0093] 7. Control and effects of this exemplary embodiment

[0094] In view of the aforementioned problems, in this exemplary embodiment, to address the electrostatic sensitivity of toner discharge from the brush 10, which changes with the potential of the photosensitive drum 1, the following control is performed, wherein the change in the potential of the photosensitive drum 1 is caused by a change in the polarity of the toner accumulated on the brush 10. The feature is that the surface potential of the photosensitive drum 1 is controlled by switching the transfer voltage to be applied to the trailing edge of the recording material based on the cumulative number of sheets printed by the image forming apparatus 100, which serves as information about toner usage.

[0095] The following will refer to Figure 9A and 9B Details of this exemplary embodiment are described below. Figure 9A The diagram is based on Figure 5 The graph shown represents the shifts in normal and reverse atomized toner concentrations predicted based on the atomization characteristics of the cumulative amount of printed sheets, with the horizontal axis representing the cumulative amount of printed sheets. In this exemplary embodiment, as... Figure 9A As shown, as the sheet passes through, reverse atomization (atomization of positive polarity toner) tends to decrease, while normal atomization (atomization of negative polarity toner) tends to increase. Specifically, the trend of each type of atomization stabilizes at approximately 100 sheets. As mentioned above, the polarity ratio of the toner accumulated on brush 10 shifts similarly to the polarity ratio of the atomized toner. Specifically, from the time the image forming apparatus 100 is new until approximately 100 sheets are printed, due to the higher ratio and amount of positive polarity toner, lateral white stripes may occur. After approximately 100 sheets, the ratio of negative polarity toner increases. This promotes the occurrence of leading edge ejection. In this exemplary embodiment, as... Figure 9B As shown, when the cumulative number of printed sheets reaches a threshold of 100, the recording material trailing edge voltage is switched. More specifically, the transfer voltage at the trailing edge of the recording material is set to a relatively high transfer voltage capable of preventing lateral white stripes up to the 100th sheet, and switches to a relatively low transfer voltage capable of preventing leading edge ejection on the 101st sheet and thereafter. Figure 9A and9B In this embodiment, the toner state up to the point where the cumulative number of printed sheets reaches 100 is referred to as the first state, and the toner state after the 101st sheet, which uses toner longer than the first state, is referred to as the second state. Although the foregoing description has been given regarding the number of sheets printed after the use of the new image forming apparatus 100, this exemplary embodiment can be similarly applied to the case where the developer container 33 is new or the developer container 33 is replenished with new toner, as will be described in the third exemplary embodiment.

[0096] 8. Effects

[0097] Next, the results of the sheet pass test performed to check the effectiveness of this exemplary embodiment will be described. The sheet pass test was performed under the following conditions. The following test was conducted using Xerox Vitality Multipurpose Paper (letter size, 20 lbs) as the recording material S in an environment with a temperature of 23°C and a relative humidity of 50%. A double-sheet intermittent printing job left the entire first sheet blank and printed a 50% density halftone image on the second sheet. This double-sheet intermittent printing job was repeated to print a total of 200 sheets, and the second sheet of each job was checked for lateral white streaks and leading edge extrusion. Here, as... Figure 9B As shown, the transfer voltage at the trailing edge of the recording material according to this exemplary embodiment is set to approximately 1750V up to the 100th sheet, and to approximately 1200V after the 101st sheet. In this sheet-pass test, the resistance detection voltage V1 during the sheet-pass is approximately 1100V. The output value of the corresponding trailing edge voltage of the recording material is calculated by multiplying the resistance detection voltage V1 by 1.59 up to the 100th sheet, and by 1.09 after the 101st sheet.

[0098] Table 1 illustrates the results of a first comparative example with a fixed transfer voltage of 1750V at the trailing edge of the recording material, a second comparative example with a fixed transfer voltage of 1200V, and the aforementioned sheet passing test conducted under this exemplary embodiment.

[0099] Table 1

[0100]

[0101] The results in Table 1 show that in the first comparative example, leading edge ejection occurred when the number of printed sheets was between 101 and 200. In the second comparative example, horizontal white stripes appeared after the image forming apparatus 100 was in a new state but before the number of printed sheets reached 100. In contrast, no image defects were observed in this exemplary embodiment.

[0102] In this exemplary embodiment, when the cumulative number of printed sheets is 100, the material trailing edge voltage is recorded from... Figure 10A The trailing edge voltage in the middle switches to Figure 10B The trailing edge voltage in the middle. Figure 10A and 10B The lower half of the diagram illustrates the surface potential of the photosensitive drum 1 corresponding to the position where the transfer voltage shown in the upper half is applied. Figure 10A The lateral white stripes and leading edge discharge OK potential shown are potentials immediately following the new conditions. In this exemplary embodiment, a relatively high recording material trailing edge voltage (+1750V) is applied to control the surface potential of the photosensitive drum 1 after transfer within the OK potential range. Figure 10B The lateral white stripes and leading edge discharge OK potential shown are the potentials after 150 sheets. In this exemplary embodiment, a relatively low recording material trailing edge voltage (+1200V) is applied to control the drum potential after transfer within the OK potential range. Therefore, the change in the charge polarity of the toner held on the brush 10, depending on the number of printed sheets, can be addressed by switching the recording material trailing edge voltage based on the number of printed sheets. The closer the toner conditions are to the new conditions, the higher the proportion of toner not sufficiently charged to the normal polarity. Due to the potential difference at the developing portion, this toner may be a reverse toner, and the reverse toner accumulates on the brush 10. In the state where the number of sheets printed from the new conditions is relatively small, control is therefore performed to form an electric field to prevent the reverse toner (i.e., the positive polarity toner in this exemplary embodiment) from moving from the brush 10 to the surface of the photosensitive drum 1. Figure 10A As shown, the border of the horizontal white stripes is therefore smaller than Figure 10B The margin in the middle, Figure 10B The diagram illustrates the potential relationship after 100 sheets have been printed, as will be described below. The longer the toner is used, the more fully it is charged to its normal polarity, and the less likely it is that toner reversal will occur due to the potential difference at the developing section. Since reverse fogging becomes less likely and normal fogging is more likely, the proportion of normal polarity toner accumulating on brush 10 increases. With a sufficient number of sheets already printed from the new conditions, control is therefore implemented to create an electric field to prevent normally fogged toner (i.e., the normal polarity toner in this exemplary embodiment) from moving from brush 10 to the surface of photosensitive drum 1. Figure 10B As shown, the margin of the leading edge is therefore smaller than Figure 10A The margin in the middle, Figure 10A The diagram illustrates the potential relationship up to a print count of 100.

[0103] As described above, the polarity of the toner accumulated on brush 10 changes, and the range of the lateral white stripe and leading edge ejection OK potential shifts with the cumulative amount of printed sheet. This shift in the range of the lateral white stripe and leading edge ejection OK potential cannot be addressed by a constant transfer voltage setting as in the comparative example. In this exemplary embodiment, the occurrence of lateral white stripes and leading edge ejection can be prevented by switching the trailing edge voltage of the recording material based on the cumulative amount of printed sheet.

[0104] The image forming apparatus 100 according to the first exemplary embodiment has the following structure and features.

[0105] The image forming apparatus 100 includes a rotatable photosensitive drum 1, a charged roller 2 that charges the surface of the photosensitive drum 1 at a charged portion opposite to the surface of the photosensitive drum 1, and a developing roller 31 that supplies toner charged to the normal polarity to the surface of the photosensitive drum 1. The image forming apparatus 100 also includes a transfer roller 5 that contacts the photosensitive drum 1 to form a transfer portion, and clamps and transports recording material S at the transfer portion and transfers the toner supplied to the photosensitive drum 1 to the recording material S; and a transfer voltage application unit (transfer voltage power supply) 160 that applies a transfer voltage with a polarity opposite to the normal polarity to the transfer roller 5. The image forming apparatus 100 also includes a brush 10 that contacts the surface of the photosensitive drum 1 downstream of the transfer portion and upstream of the charged portion in the rotational direction of the photosensitive drum 1 to form a brush portion; and a brush voltage application unit (brush power supply) 130 that applies a brush voltage of normal polarity to the brush 10. The image forming apparatus 100 also includes a memory 154 for storing information about the use of toner, and a control unit 200 for controlling the transfer voltage application unit 160 and the brush voltage application unit 130. The developing roller 31 is configured to collect the toner remaining on the surface of the photosensitive drum 1 after the toner supplied to the photosensitive drum 1 has been transferred to the recording material S at the transfer section.

[0106] When the recording material S is held at the transfer section at either the leading edge or the trailing edge in the transport direction of the recording material S, the area in the transfer section that holds the photosensitive drum 1 in the transport direction of the recording material S perpendicular to the transport direction is called the first region. The area in the transfer section that does not hold the photosensitive drum 1 in the transport direction of the recording material S perpendicular to the transport direction is called the second region. The potential difference between the surface potential formed on the second region and the brush voltage when the second region reaches the brush section, determined based on the first information stored in the memory 154, is called the first potential difference.

[0107] The potential difference between the surface potential formed on the second region and the brush voltage when the second region reaches the brush portion, determined based on second information stored in memory 154 and different from the first information, is called the second potential difference. In this case, the control unit 200 performs control to make the first potential difference different from the second potential difference.

[0108] The second region includes a gap wall portion D formed at the leading edge or trailing edge of the recording material S, and a contact portion where the photosensitive drum 1 and the transfer roller 5 contact each other. The surface potential of the first surface, which is the surface of the photosensitive drum 1 forming the gap wall portion D, when it reaches the brush portion is represented by Va. The surface potential of the second surface, which is the surface of the photosensitive drum 1 forming the contact portion, when it reaches the brush portion is represented by Vb, and the brush voltage is represented by Vc. In this case, the potential difference (i.e., Va-Vc) formed between the surface potential of the first surface of the brush portion and the brush voltage is represented by VA. The potential difference (i.e., Vb-Vc) formed between the surface potential of the second surface of the brush portion and the brush voltage is represented by VB. The control unit 200 can sequentially control the switching of the transfer voltage or the brush voltage to control the potential differences VA and VB. Here, compared to when using the first information, the control unit 200 desires to make the potential difference VA larger and the potential difference VB smaller when using the second information. In this exemplary embodiment, the control unit 200 controls the trailing edge voltage of the recording material including the first and second regions to set the potential differences VA and VB within a suitable range.

[0109] The second information pertains to a toner that has been used longer than the toner in the first information. When a first potential difference is formed based on the second information, the control unit 200 executes control such that the surface potential formed on the second region has an absolute value smaller than the absolute value of the brush voltage. The control unit 200 executes control such that the transfer voltage when a second potential difference is formed at the contact portion is lower than the transfer voltage when a first potential difference is formed at the contact portion. In this exemplary embodiment, if a transfer portion is formed in the second region, the control unit 200 executes control such that the first transfer voltage applied based on the first information stored in the memory 154 is different from the second transfer voltage applied based on the second information stored in the memory 154. Specifically, the control unit 200 executes control such that the absolute value of the first transfer voltage is greater than the absolute value of the second transfer voltage.

[0110] In this exemplary embodiment, the recording material trailing voltage is switched to handle the toner discharge from brush 10. However, it should be understood that if the brush voltage is variable, a similar effect can be achieved by switching the brush voltage to control the potential difference between the surface potential of the photosensitive drum 1 after transfer and the brush voltage. Control unit 200 can perform control such that the brush voltage when forming the second potential difference is lower than the brush voltage when forming the first potential difference. Control unit 200 can perform control such that the first brush voltage applied based on the first information stored in memory 154 is different from the second brush voltage applied based on the second information stored in memory 154. Specifically, control unit 200 can perform control such that the first brush voltage is higher than the second brush voltage.

[0111] Although the control performed when the trailing edge of the recording material S passes through the transfer roller gap portion is described in this exemplary embodiment, it will be understood that a similar effect can be obtained by performing the control when the leading edge of the recording material S passes through the transfer roller gap portion.

[0112] The aforementioned configuration of the first exemplary embodiment can prevent image defects caused by toner accumulating on the brush 10.

[0113] Although in this exemplary embodiment the recording material trailing edge voltage is switched based on the cumulative number of a predetermined number of printed sheets as a threshold, this is not limiting. For example, the recording material trailing edge voltage could be continuously changed based on the cumulative number of printed sheets.

[0114] Although the recording of the trailing edge voltage of the material is switched based on the cumulative number of printed sheets in this exemplary embodiment, this is not limiting. For example, the cumulative number of revolutions of the developing roller 31 can be used. Since the change in the polarity of the atomized toner is caused by the change in the charged state of the toner due to friction in the developing container 33, the cumulative number of revolutions is more direct than the cumulative number of printed sheets, and is even more desirable in terms of accuracy. The cumulative number of revolutions of the developing roller 31 will be described in detail in the second exemplary embodiment.

[0115] Alternatively, information about the remaining level of toner in the developer container 33 containing the toner can be used.

[0116] Next, a second exemplary embodiment of the present disclosure will be described. The basic construction and operation of the image forming apparatus according to the second exemplary embodiment are similar to those of the image forming apparatus 100 according to the first exemplary embodiment. Therefore, components of the image forming apparatus of the second exemplary embodiment having functions or constructions similar to or corresponding to those of the image forming apparatus 100 of the first exemplary embodiment are indicated by the same reference numerals as those of the image forming apparatus 100 of the first exemplary embodiment. Detailed descriptions thereof will be omitted.

[0117] In the first exemplary embodiment, switching control of the trailing edge voltage of the recording material based on the change in polarity of the atomized toner under new conditions has been described. In this exemplary embodiment, switching control of the trailing edge voltage of the recording material based on the change in polarity of the atomized toner due to toner degradation will be described.

[0118] The toner in the developer chamber 33 gradually deteriorates due to mechanical damage caused by agitation and sliding friction with the developing blade 34. Specifically, the toner's charge decreases due to the loss or embedding of additives that contribute to its charge-carrying capacity, or due to deformation of the toner itself. This toner deterioration worsens as the cumulative rotational speed of the developing roller 31 increases under new conditions.

[0119] In this exemplary embodiment, the amount of developing roller 31 used is used as an indicator to determine the cumulative number of revolutions of developing roller 31. It should be understood that the cumulative amount of printing sheet can be used, as described in the first exemplary embodiment.

[0120] The amount of developing roller 31 used is defined by the following equation 1:

[0121] The usage of developing roller 31 = the cumulative number of revolutions of developing roller 31 ÷ the total number of revolutions of developing roller 31 that may cause image defects x 100 (%). (Equation 1)

[0122] Here, the amount of new developing roller 31 used is 0%, and the amount of developing roller 31 used that can produce image defects such as blank spots and vertical stripes is 100%.

[0123] Next, a sheet pass test performed according to this exemplary embodiment to check the usage of the developing roller 31 and changes in the characteristics of the atomized toner will be described. The sheet pass test was performed under the following conditions: 5000 images with a print ratio of 4% were printed intermittently in a dual-sheet manner using Xerox Vitality Multipurpose Paper (letter size, 20 lbs) as the recording material S at a temperature of 23°C and a relative humidity of 50%. The amount of toner in the new developing chamber 33 was 100 g. It is assumed that the usage of the developing roller 31 is 100% when 80 g of toner is consumed during the sheet pass test.

[0124] During the aforementioned test, when the amount of developing roller 31 used reached 100%, the concentration of atomized toner was measured using the same measurement method as in the first exemplary embodiment. Figure 11 The measurement results are illustrated. Similar to the first exemplary embodiment, Figure 11 The concentration of the atomized toner in the image was measured using a back contrast of 400V (Vback). For example... Figure 11As shown, during the sheet passage test, the concentration of the atomized toner shifts upwards and continues to increase until 100% after the cumulative revolutions of the developing roller 31 increase due to the sheet passage and the usage of the developing roller 31 exceeds approximately 80%. Similar to the toner under the new conditions according to the first exemplary embodiment, most of this atomized toner in this exemplary embodiment is a reverse atomized toner, therefore most of the toner accumulated on the brush 10 is positively polar. Therefore, the following occurs: Figure 8A The toner shown is discharged.

[0125] As from Figure 11 As can be seen from the results, in this exemplary embodiment, the shift in the concentration of the atomizing toner relative to the amount used in the developing roller 31 is a shift in reverse atomization, such as... Figure 12A As shown. Figure 12B As shown, the trailing edge voltage of the recording material is therefore switched based on the amount of developing roller 31 used. This prevents Figure 8A The toner emission shown is illustrated. Figure 12A and 12B The state in which the developing roller 31 is used up to 80% is shown as the second state. The state in which the developing roller 31 is used beyond the second state (i.e., more than 80% usage) is shown as the third state.

[0126] The image forming apparatus 100 according to the second exemplary embodiment has the following structure and features.

[0127] The control unit 200 performs the following control when controlling a third potential difference formed between the surface potential and the brush voltage in the second region when the second region reaches the brush portion, determined based on third information regarding the use of a toner that has been used longer than the toner in the second information. The information regarding the use of the toner may be information regarding the use of the developing roller 31. When the third potential difference is formed, the control unit 200 performs control such that the absolute value of the surface potential formed in the second region is less than the absolute value of the brush voltage. Importantly, the transfer voltage when the third potential difference is formed at the contact portion is controlled to be higher than the transfer voltage when the second potential difference is formed at the contact portion. Therefore, the control unit 200 performs control such that the third transfer voltage applied based on the third information is higher than the second transfer voltage. Here, the control unit 200 may perform control such that the third brush voltage when the third potential difference is formed is higher than the second brush voltage when the second potential difference is formed.

[0128] In this exemplary embodiment, toner degradation is associated with the amount of toner used in the developing roller 31. However, this is not limiting. For example, the remaining toner level in the developing chamber 33 can be used. This is because as the amount of toner in the developing chamber 33 decreases, the agitation frequency of individual toner particles and the sliding friction against the developing blade 34 become relatively high, causing degradation to occur. Examples of units for detecting the remaining toner level generally fall into two categories. One is a hardware prediction unit that predicts the remaining level by detecting changes in toner behavior in the developing chamber 33 through changes in transmittance. The other is a software prediction unit that predicts the remaining toner level based on the consumption predicted by integrating multiple pixel signals of image information.

[0129] In this way, toner degradation can be correlated with the cumulative number of rotations of the developing roller 31 or the remaining toner level. It will be understood that both can be used in combination to improve accuracy.

[0130] The aforementioned configuration of the second exemplary embodiment can prevent image defects caused by toner accumulating on the brush 10 at the end of its lifespan.

[0131] Next, a third exemplary embodiment of this disclosure will be described. Figure 13 The illustration shows an image forming apparatus 300 according to a third exemplary embodiment, which has a basic configuration and operation similar to that of the image forming apparatus 100 according to a first exemplary embodiment. Therefore, components of the image forming apparatus 300 of the third exemplary embodiment, having functions or configurations similar to or corresponding to those of the image forming apparatus 100 of the first exemplary embodiment, are indicated by the same reference numerals as those of the image forming apparatus 100 of the first exemplary embodiment. Detailed descriptions thereof will be omitted.

[0132] In this exemplary embodiment, control of a toner-replenishing type image forming apparatus 300 in which toner is replenished in the developer reservoir 33 will be described. The method for replenishing toner in the developer reservoir 33 when the remaining toner level in the developer reservoir 33 is detected to have decreased to near a predetermined value will be described. Figure 13 The toner container 21 outside the main body of the image forming apparatus 300 shown is used to replenish toner. This exemplary embodiment is also applicable to a toner replenishment system in which the developer chamber 33 is continuously replenished with toner from an external toner supply container connected to the developer chamber 33 by means of a screw conveyor, so that the remaining toner level is maintained at a substantially constant level.

[0133] In the second exemplary embodiment, switching control of the trailing edge voltage of the recording material based on the change in polarity of the atomized toner due to toner degradation has been described. In this exemplary embodiment, control performed after the remaining level of toner in the developer chamber 33 is equal to or less than a predetermined level and then toner is replenished to the developer chamber 33 again will be described.

[0134] If a large amount of toner is added to the developer container 33 after the remaining toner level has decreased, the ratio of new toner increases. In this case, the atomized toner is expected to exhibit behavior similar to that described in the first exemplary embodiment when the toner is under new conditions. For example, suppose that the amount of developing roller 31 used reaches 100% in a sheet pass-through test according to the second exemplary embodiment, and then 80g of toner is added. Figure 14A The diagram illustrates the shift in toner concentration relative to the amount used in the developing roller 31 after toner replenishment. Figure 14A As shown, the concentration of atomized toner after toner replenishment shifts similarly to the situation under new conditions according to the first exemplary embodiment. In this exemplary embodiment, reverse atomization decreases when the amount of developing roller 31 used is approximately 2%. Therefore, as... Figure 14B As shown, by performing control to switch the trailing edge voltage of the recording material, toner leakage from brush 10 can be prevented.

[0135] As described above, in the toner replenishment system according to this exemplary embodiment, when toner replenishment is detected, the amount of toner used on the developing roller 31 is calculated and referenced from 0% after replenishment, unlike the amount calculated before replenishment. The recording material trailing edge voltage can therefore be appropriately switched based on the change in polarity of the atomized toner corresponding to the amount of toner used on the developing roller 31 after replenishment, and image defects caused by toner discharge from the brush 10 can be prevented.

[0136] As described above, according to exemplary embodiments of the present disclosure, image defects caused by toner accumulation on the brush can be prevented.

[0137] Embodiments of this disclosure can also be implemented by a computer that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a "non-transitory computer-readable storage medium") to perform the functions of one or more embodiments of the above embodiments and / or includes one or more circuits (e.g., application-specific integrated circuits (ASICs)) for performing the functions of one or more embodiments of the above embodiments, and by a method executed by a computer of a system or device, for example, by reading and executing computer-executable instructions from a storage medium to perform the functions of one or more embodiments of the above embodiments and / or controlling one or more circuits to perform the functions of one or more embodiments of the above embodiments. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessor unit (MPU)) and may include a network of individual computers or individual processors to read and execute computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, a hard disk, random access memory (RAM), read-only memory (ROM), a storage device for a distributed computing system, an optical disc (such as a CD, DVD, or Blu-ray disc), or a digital versatile disc (BD). TM One or more of the following: flash memory devices, memory cards, etc.

[0138] Other embodiments

[0139] The embodiments of the present invention can also be implemented by providing software (programs) that perform the functions of the above embodiments to a system or device via a network or various storage media, and the computer or central processing unit (CPU) or microprocessor unit (MPU) of the system or device reads out and executes the program.

[0140] While this disclosure has been described with reference to exemplary embodiments, it should be understood that this disclosure is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus, characterized in that, include: Rotatable image-carrying component; A charged component is configured to charge the surface of the image carrier component at a charged portion opposite to the surface of the image carrier component; The developing element is configured to supply toner charged to normal polarity to the surface of the image carrier element; The transfer component is configured to contact the image carrier component to form a transfer portion, and to hold and deliver recording material at the transfer portion and transfer toner supplied to the image carrier component to the recording material; A transfer voltage application unit is configured to apply a transfer voltage having a polarity opposite to the normal polarity to the transfer member; A brush is configured to contact the surface of the image carrier member downstream of the transfer portion and upstream of the charged portion in the rotational direction of the image carrier member to form a brush portion; A brush voltage application unit is configured to apply the normal polarity brush voltage to the brush; The storage unit is configured to store information about the use of the toner; as well as The control unit is configured to control the transfer voltage application unit and the brush voltage application unit. In this process, after the toner supplied to the surface of the image carrier is transferred to the recording material at the transfer section, the developing member is configured to collect the toner remaining on the surface of the image carrier. In a situation where the leading edge or trailing edge of the recording material in the transport direction is clamped at the transfer portion, and the area of ​​the image carrier member in the transport direction clamped in the transfer portion in a direction perpendicular to the transport direction is a first region, and the area of ​​the image carrier member in the transport direction not clamped in the transfer portion in a direction perpendicular to the transport direction is a second region, the control unit is configured to perform control such that a first potential difference between the surface potential and the brush voltage formed on the second region when the second region reaches the brush portion, based on first information stored in the storage unit and different from the first information, is different from the second potential difference between the surface potential and the brush voltage formed on the second region when the second region reaches the brush portion, and such that when the area in the second region corresponding to the space formed between the surface of the image carrier member and the transfer member at the trailing edge of the recording material reaches the brush portion, the absolute value of the surface potential of that area is less than the absolute value of the brush voltage.

2. The image forming apparatus according to claim 1, The second piece of information relates to toners that have been used for a longer period of time than the toners mentioned in the first piece of information, and in, When the first potential difference is formed, the control unit is configured to perform control such that the absolute value of the surface potential formed in the second region is less than the absolute value of the brush voltage.

3. The image forming apparatus according to claim 2, The second region includes a region corresponding to the space formed at the leading edge or trailing edge between the surface of the image carrier member and the transfer member, as well as the contact portion where the image carrier member and the transfer member contact each other. The control unit is configured to perform control such that the transfer voltage when a second potential difference is formed at the contact portion is lower than the transfer voltage when a first potential difference is formed at the contact portion.

4. The image forming apparatus according to claim 2, wherein the control unit is configured to perform control such that the brush voltage when forming the second potential difference is lower than the brush voltage when forming the first potential difference.

5. The image forming apparatus according to claim 2, wherein, When controlling a third potential difference between the surface potential formed on the second region and the brush voltage in the case where the second region reaches the brush portion, determined based on third information related to a toner that has been used longer than the toner in the second information, the control unit is configured to perform control such that the absolute value of the surface potential formed on the second region when the third potential difference is formed is less than the absolute value of the brush voltage.

6. The image forming apparatus according to claim 5, The second region includes a region corresponding to the space formed at the leading edge or trailing edge between the surface of the image carrier member and the transfer member, as well as the contact portion where the image carrier member and the transfer member contact each other. The control unit is configured to perform control such that the absolute value of the transfer voltage when a third potential difference is formed at the contact portion is greater than the absolute value of the transfer voltage when a second potential difference is formed at the contact portion.

7. The image forming apparatus according to claim 5, wherein the control unit is configured to perform control such that the absolute value of the brush voltage when forming the third potential difference is greater than the absolute value of the brush voltage when forming the second potential difference.

8. The image forming apparatus according to claim 1, wherein the cumulative number of sheets passing through the image forming apparatus is used as information regarding the use of toner.

9. The image forming apparatus according to claim 1, wherein the cumulative revolutions of the developing member of the image forming apparatus are used as information regarding the use of toner.

10. The image forming apparatus of claim 1, further comprising a developing device, the developing device including a developing member and a developing agent receiving unit configured to receive a toner. Information regarding the remaining level of toner contained in the developer container unit is used as information about the use of the toner.

11. An image forming apparatus, characterized in that, include: Rotatable image-carrying component; A charged component is configured to charge the surface of the image carrier component at a charged portion opposite to the surface of the image carrier component; The developing element is configured to supply toner charged to normal polarity to the surface of the image carrier element; The transfer component is configured to contact the image carrier component to form a transfer portion, and to hold and deliver recording material at the transfer portion and transfer toner supplied to the image carrier component to the recording material; A transfer voltage application unit is configured to apply a transfer voltage having a polarity opposite to the normal polarity to the transfer member; A brush is configured to contact the surface of the image carrier member downstream of the transfer portion and upstream of the charged portion in the rotational direction of the image carrier member to form a brush portion; The storage unit is configured to store information about the use of the toner; as well as The control unit is configured to control the transfer voltage application unit. In this process, after the toner supplied to the surface of the image carrier is transferred to the recording material at the transfer section, the developing component is configured to collect the toner remaining on the surface of the image carrier. Wherein, in a state where the leading edge or trailing edge of the recording material in the transport direction is clamped at the transfer portion, and the area of ​​the transfer portion where the image carrier member in the transport direction clamps the recording material in a direction perpendicular to the transport direction is a first region, and the area of ​​the transfer portion where the image carrier member in the transport direction does not clamp the recording material in a direction perpendicular to the transport direction is a second region, the control unit is configured to perform control when a transfer portion is formed in the second region, such that a first transfer voltage applied based on first information stored in the storage unit is different from a second transfer voltage applied based on second information stored in the storage unit, and In the case where the third potential difference is controlled based on third information relating to a toner that has been used longer than the toner in the second information, the control unit is configured to perform control such that the absolute value of the third transfer voltage applied based on the third information stored in the storage unit is greater than the absolute value of the second transfer voltage.

12. The image forming apparatus according to claim 11, The second piece of information relates to toners that have been used for a longer period of time than the toners mentioned in the first piece of information, and The control unit is configured to perform control such that the absolute value of the first transfer voltage is greater than the absolute value of the second transfer voltage.

13. An image forming apparatus, characterized in that, include: Rotatable image-carrying component; A charged component is configured to charge the surface of the image carrier component at a charged portion opposite to the surface of the image carrier component; The developing element is configured to supply toner charged to normal polarity to the surface of the image carrier element; The transfer component is configured to contact the image carrier component to form a transfer portion, and to hold and deliver recording material at the transfer portion and transfer toner supplied to the image carrier component to the recording material; A brush is configured to contact the surface of the image carrier member downstream of the transfer portion and upstream of the charged portion in the rotational direction of the image carrier member to form a brush portion; A brush voltage application unit is configured to apply the normal polarity brush voltage to the brush; The storage unit is configured to store information about the use of the toner; as well as The control unit is configured to control the brush voltage application unit. In this process, after the toner supplied to the surface of the image carrier is transferred to the recording material at the transfer section, the developing component is configured to collect the toner remaining on the surface of the image carrier. Wherein, in a state where the leading edge or trailing edge of the recording material in the transport direction is clamped at the transfer portion, and the area of ​​the transfer portion where the image carrier member in the transport direction clamps the recording material in a direction perpendicular to the transport direction is a first region, and the area of ​​the transfer portion where the image carrier member in the transport direction does not clamp the recording material in a direction perpendicular to the transport direction is a second region, the control unit is configured to perform control when the transfer portion forms a transfer portion in the second region, such that the first brush voltage applied based on the first information stored in the storage unit is different from the second brush voltage applied based on the second information stored in the storage unit, and The control unit is configured to perform control when controlling a third potential difference based on third information relating to a toner that has been used longer than the toner in the second information, such that the absolute value of the third brush voltage applied based on the third information stored in the storage unit is greater than the absolute value of the second brush voltage.

14. The image forming apparatus according to claim 13, The second piece of information relates to toners that have been used for a longer period of time than the toners mentioned in the first piece of information, and The control unit is configured to perform control such that the absolute value of the first brush voltage is greater than the absolute value of the second brush voltage.

Images