Imaging equipment

Abstract

This disclosure relates to an imaging apparatus. A control unit performs control such that, during an imaging operation, the direction of the electric field generated in the first region of the image carrier forming a transfer portion, in a state where the first region passes through a contact portion, is different from the direction of the electric field generated in the second region of the image carrier forming a contact portion, relative to the voltage applied to the brush member, during a non-imaging operation different from the imaging operation, specifically during a second operation where the operation changes from a first operation where the image carrier rotates at a first speed to a second operation where the image carrier rotates at a second speed different from the first speed.

Description

Technical Field

[0001] This disclosure relates to imaging devices that use electrophotographic systems, such as laser printers, copiers, and fax machines. Background Technology

[0002] Electrophotographic systems, also known as image recording systems, are used in imaging devices such as printers and copiers. An electrophotographic system is a system in which an electrostatic latent image is formed on a photosensitive drum using a laser beam through electrophotographic processing, and the latent image is developed with a charged toner to form a developer image. The developer image is then transferred and fixed onto a recording medium to form an image.

[0003] A cleaner-free system is known in which transfer-residual toner that has not been transferred onto the film and remains on the photosensitive drum is recovered by the developing unit instead of by the cleaning unit, and the toner is reused. Japanese Patent Application Publication No. 2007-65580 discusses a cleaner-free imaging apparatus. This cleaner-free imaging apparatus has a configuration in which a brush member for recovering deposits attached to the photosensitive drum rests against the photosensitive drum, instead of cleaning the surface of the photosensitive drum by the cleaning unit.

[0004] However, the structure discussed in Japanese Patent Application Publication No. 2007-65580 has the following problems. Toner not used for imaging (e.g., transfer-residual toner remaining on the surface of the photosensitive drum) accumulates on the brush members that abut against the photosensitive drum. If toner accumulates on the brush members, the brush members cannot retain the toner, and the toner passing through the brush members adheres to the charging roller. This can lead to poor charging, resulting in defective images. Summary of the Invention

[0005] This disclosure relates to an imaging apparatus that prevents defective images by performing control to effectively expel toner adhering to a brush component abutting against a photosensitive drum.

[0006] According to one aspect of the present invention, an imaging apparatus for performing an imaging operation to form an image on a transfer receiving member includes: a rotatable image carrier; a charging member configured to charge a surface of the image carrier at a charging portion facing the image carrier; an exposure unit configured to expose the surface of the image carrier charged by the charging member to form an electrostatic latent image on the surface of the image carrier; a developing member configured to develop the electrostatic latent image into a developing image by supplying a developing agent charged to normal polarity to the surface of the image carrier; a transfer member configured to form a transfer portion by contacting the image carrier and transferring the developing image from the image carrier to the transfer receiving member at the transfer portion; a brush member configured to form a contact portion downstream of the transfer portion and upstream of the charging portion in the rotational direction of the image carrier and to contact the image carrier at the contact portion; a voltage applying unit configured to apply a voltage to the brush member; a driving unit configured to rotatably drive the image carrier; and a control unit configured to control the voltage applying unit and the driving unit. After the developer image formed on the surface of the image carrier is transferred to the transfer receiving unit at the transfer portion, the developer remaining on the surface of the image carrier is recovered by the developing unit. The control unit executes control so that the direction of the electric field generated in the first region of the image carrier forming the transfer portion, in a state where the first region of the image carrier forms the contact portion, is in a state where it passes through the contact portion, is different from the direction of the electric field generated in the second region of the image carrier forming the contact portion, relative to the voltage applied to the brush member, during a non-imaging operation different from the imaging operation, when the operation changes from a first operation where the image carrier rotates at a first speed to a second operation where the image carrier rotates at a second speed different from the first speed.

[0007] Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0008] Figure 1 This is a schematic cross-sectional view of an imaging device according to a first exemplary embodiment.

[0009] Figure 2A and Figure 2B This is a schematic diagram of a brush component according to a first exemplary embodiment.

[0010] Figure 3 This is a control block diagram according to a first exemplary embodiment.

[0011] Figure 4A and Figure 4B This is a diagram illustrating the movement of toner through the brush component according to a first exemplary embodiment.

[0012] Figures 5A to 5CThis is a diagram illustrating the force applied to the brush member according to a first exemplary embodiment.

[0013] Figure 6 It is a graph illustrating the potential relationships during each operation in the printing process according to the first exemplary embodiment.

[0014] Figure 7 This is a timing diagram according to the first exemplary embodiment, showing the start-up of the photosensitive drum and the transition from imaging operation to stopping the photosensitive drum operation.

[0015] Figure 8 This is a schematic cross-sectional view of the brush component and photosensitive drum during control execution according to the second exemplary embodiment.

[0016] Figure 9 This is a schematic cross-sectional view of the brush component and photosensitive drum during control execution according to a third exemplary embodiment. Detailed Implementation

[0017] Some embodiments of this disclosure are described in detail with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described in the exemplary embodiments should be appropriately varied depending on the construction of the device to which this disclosure is applied and various conditions. In other words, the dimensions, materials, shapes, relative arrangements, etc., of the components described in the exemplary embodiments are not intended to limit the scope of this disclosure.

[0018] 1. Imaging equipment

[0019] Figure 1 A schematic configuration of an imaging device 100 according to a first exemplary embodiment of the present disclosure is shown.

[0020] The imaging device 100 according to the first exemplary embodiment is a monochrome laser beam printer employing a cleaner-free system and a contact charging system.

[0021] The imaging apparatus 100 according to the first exemplary embodiment includes a cylindrical photosensitive component, namely a photosensitive drum 1, which serves as an image carrier. A charging roller 2, serving as a charging unit, and a developing apparatus 3, serving as a developing unit, are disposed around the photosensitive drum 1. Figure 1 As shown, the exposure device (exposure unit) 4 is disposed between the charging roller 2 and the developing device 3 in the rotational direction of the photosensitive drum 1. The transfer roller 5, which serves as the transfer unit, is in pressure contact with the photosensitive drum 1.

[0022] According to the first exemplary embodiment, the photosensitive drum 1 is a negatively charged organic photosensitive component. The photosensitive drum 1 includes a photosensitive layer on a drum-shaped base component made of aluminum, and the photosensitive drum 1 is driven by a drive motor as a drive unit 110. Figure 3The photosensitive drum 1 is driven to rotate at a predetermined processing speed in the direction of the arrow (clockwise) in the figure. In the first exemplary embodiment, the processing speed corresponds to the circumferential speed (surface movement speed) of the photosensitive drum 1 at 140 mm / ses, and the outer diameter of the photosensitive drum 1 is 24 mm.

[0023] The charging roller 2, serving as a charging component, contacts the photosensitive drum 1 with a predetermined pressure contact force, thereby forming a charging section. The charging roller 2 is powered by a high-voltage charging power supply E1, which serves as a charging voltage application unit. Figure 3 The charging roller 2 receives a desired charging voltage and uniformly charges the surface of the photosensitive drum 1 to a predetermined potential. In the first exemplary embodiment, the surface of the photosensitive drum 1 is negatively charged by the charging roller 2. During the charging process, a predetermined charging voltage (charging bias) is applied to the charging roller 2 from the charging power supply E1. In the first exemplary embodiment, a negative polarity DC voltage is applied to the charging roller 2 as the charging voltage during the charging process. As an example, the charging voltage according to the first exemplary embodiment is set to -1300V (volts). In the first exemplary embodiment, the surface of the photosensitive drum 1 is thus uniformly charged with a dark zone potential Vd of -700V. More specifically, the charging roller 2 charges the surface of the photosensitive drum 1 by using a discharge generated in at least one of the gaps formed between the charging roller 2 and the photosensitive drum 1 on the upstream and downstream sides along the rotation direction of the photosensitive drum 1 at the portion where the charging roller 2 contacts the photosensitive drum 1. However, in this example, the description is given based on the assumption that the portion where the charging roller 2 and the photosensitive drum 1 abut against each other in the rotation direction of the photosensitive drum 1 is the charging portion.

[0024] Exposure unit 4 is a laser scanner device in the first exemplary embodiment. Exposure unit 4 outputs a laser beam corresponding to image information input from an external device such as a host, thereby scanning and exposing the surface of photosensitive drum 1. By using this exposure, an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the surface of photosensitive drum 1. In the first exemplary embodiment, the dark area potential Vd formed on the surface of photosensitive drum 1 by uniform charging processing is reduced in absolute value by exposure by exposure unit 4, and becomes a bright area potential Vl of -100V. In this example, the position on photosensitive drum 1 exposed by exposure unit 4 along the rotation direction of photosensitive drum 1 is regarded as the exposure portion (exposure position). Exposure unit 4 is not limited to a laser scanner device, and may be, for example, an array of light-emitting diodes (LEDs) arranged along the longitudinal direction of photosensitive drum 1.

[0025] In a first exemplary embodiment, a contact developing system is used as the developing system. The developing apparatus 3 includes a developing roller 31 as a developing component or developer carrier, a toner supply roller 32 as a developer supply unit, a developer receiving chamber 33 for containing toner, and a developing blade 34. The toner supplied from the developer receiving chamber 33 to the developing roller 31 by the toner supply roller 32 is charged to a predetermined polarity by passing through the blade clamping portion (which is the portion where the developing roller 31 and the developing blade 34 contact each other). The toner carried on the developing roller 31 moves from the developing roller 31 to the photosensitive drum 1 at the developing portion based on an electrostatic image. In this example, the portion where the developing roller 31 and the photosensitive drum 1 contact each other in the rotational direction of the photosensitive drum 1 is considered the developing portion. In the first 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 portion. The drive motor 110, which serves as the drive unit for driving the developing roller 31, can be a main motor shared with the drive motor 110 for the photosensitive drum 1, or different drive motors can be used to rotate the photosensitive drum 1 and the developing roller 31 separately. During development, a predetermined developing voltage (developing bias voltage) is applied from the developing power supply E2, which serves as the developing voltage application unit. Figure 3 A negative DC voltage is applied to the developing roller 31 during development, and the developing voltage is set to -380V. In the first exemplary embodiment, toner charged to the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in the first exemplary embodiment) adheres to the exposure surface (image portion), which is the imaging portion on the photosensitive drum 1 where the absolute value of the potential decreases upon exposure after undergoing uniform charging. This developing system is called a reverse developing system. In the first exemplary embodiment, the normal polarity of the toner's charging polarity during development is negative. In the first exemplary embodiment, a single-component non-magnetic contact developing method is employed. However, this disclosure is not limited thereto; a two-component non-magnetic contact developing method, a non-contact developing method, a magnetic developing method, or other methods may be employed. A two-component non-magnetic contact developing method is a method in which a two-component developer comprising a non-magnetic toner and a magnetic carrier is used as the developing agent, and the developing agent (magnetic brush) carried on the developing agent carrier contacts the photosensitive drum 1 to perform developing. Non-contact development is a method of dispersing toner from a developer carrier disposed non-contactly facing the photosensitive element to the photosensitive element. Magnetic development is a method in which development is performed while a magnetic toner is carried on a developer carrier by magnetic force, the developer carrier being disposed in a contact or non-contact manner facing the photosensitive element and including a magnet as a magnetic field generating unit. In a first exemplary embodiment, the toner has a center average particle size of 6 μm (micrometers), and the normal charging polarity of the toner is negative.

[0026] As for the transfer roller 5, which is the transfer component, a roller including an elastic component can be appropriately used. This elastic component is, for example, a sponge rubber made of polyurethane rubber, ethylene propylene diene monomer (EPDM), or nitrile rubber (NBR). The transfer roller 5 is pressed against the photosensitive drum 1, thereby forming a transfer portion where the photosensitive drum 1 and the transfer roller are in pressure contact with each other. During transfer, a predetermined transfer voltage (transfer bias voltage) is applied from the transfer power supply E3, which is the transfer voltage application unit. Figure 3 A DC voltage with a polarity (positive in the first exemplary embodiment) opposite to the normal polarity of the toner is applied to the transfer roller 5 during transfer. In the first exemplary embodiment, as an example, the transfer voltage during transfer is +1000V.

[0027] The toner image is electrostatically transferred from the photosensitive drum 1 to the recording medium S by the electric field formed between the transfer roller 5 and the photosensitive drum 1.

[0028] Synchronizing with the arrival of the toner image formed on the photosensitive drum 1 at the transfer section, the transfer medium (recording medium) S stored in the cartridge 6 is fed by the sheet feed unit 7 and transported to the transfer section via the alignment roller pair 8. The toner image formed on the photosensitive drum 1 is transferred onto the recording medium S by the transfer roller 5, which is supplied with a predetermined transfer voltage from the transfer high-voltage power supply E3.

[0029] The recording medium S, with the toner image already transferred, is fed to the fuser 9. The fuser 9 is a film-heated fuser that includes a fuser film 91 and a pressure roller 92. The fuser film 91 includes a fuser heater (not shown) and a thermistor (not shown) for measuring the temperature of the fuser heater. The pressure roller 92 brings the recording medium S into pressure contact with the fuser film 91. When the recording medium S is heated and pressurized, the toner image is fixed, and then the recording medium S is discharged to the outside of the imaging device 100 through the discharge roller pair 12.

[0030] Transfer-residual toner remaining on the photosensitive drum 1 and not transferred to the recording medium S is removed in the following process.

[0031] The transfer-residual toner comprises a mixture of toner charged to a positive polarity and toner charged to a negative polarity but with insufficient charge. The transfer-residual toner is recharged to a negative polarity by discharge at the charging section of the charging roller 2. As the photosensitive drum 1 rotates, the transfer-residual toner, recharged to a negative polarity by the charging roller 2, reaches the developing section. At this time, there are cases where an imaging portion forms on the surface of the photosensitive drum 1 that has reached the developing section, and cases where a non-imaging portion forms on the surface of the photosensitive drum 1 that has reached the developing section. The imaging portion is the portion where an electrostatic latent image is formed, and the non-imaging portion is the portion where no electrostatic latent image is formed. The behavior of the transfer-residual toner that has reached the developing section in the cases of the imaging portion and the non-imaging portion of the photosensitive drum 1 will be described separately.

[0032] The transfer-residual toner attached to the imaging portion of the photosensitive drum 1 is not transferred from the photosensitive drum 1 to the developing roller 31 at the developing portion. The transfer-residual toner, together with the developed toner, moves from the developing roller 31 to the transfer portion and is transferred onto the recording medium S to form an image.

[0033] Conversely, the transfer-residual toner adhering to the non-imaging portion of the photosensitive drum 1 is recharged to the negative polarity, i.e., the normal polarity, via the charging section. Then, through the potential difference between the potential at the non-imaging portion of the photosensitive drum 1 and the developing voltage, the transfer-residual toner is transferred to the developing roller 31 at the developing section and is recovered into the developer chamber 33. The toner recovered into the developer chamber 33 is reused for imaging.

[0034] 2. Structure of the brush component

[0035] A paper dust removal mechanism according to a first exemplary embodiment will now be described. Figure 1 As shown, the imaging apparatus 100 according to the first exemplary embodiment includes a brush member 10 (recycling member), which serves as a contact member of a paper dust removal mechanism. In the first exemplary embodiment, the imaging apparatus 100 includes a brush member 10 that contacts the surface of the photosensitive drum 1 downstream of the transfer portion and upstream of the charging portion in the rotational direction of the photosensitive drum 1 to form a brush contact portion (brush contact position). In this example, the portion in which the brush member 10 and the photosensitive drum 1 contact each other in the rotational direction of the photosensitive drum 1 is considered the brush contact portion (hereinafter referred to as the contact portion).

[0036] Figure 2A This is a schematic diagram showing a single brush component 10 when viewed along its longitudinal direction (generally parallel to the rotation axis of the photosensitive drum 1). Figure 2B This is a schematic diagram showing the brush component 10 resting against the photosensitive drum 1 when viewed along its longitudinal direction.

[0037] The brush portion of the brush component 10 includes conductive fixed brushes 11 arranged in a fixed manner. For example... Figure 2A and 2B As shown, the brush component 10 includes a pile yarn 11a and a base fabric 11b. The pile yarn 11a is made of conductive nylon 6 and is the bristle material for brushing the surface of the photosensitive drum 1. The base fabric 11b supports the pile yarn 11a. As described above, the brush component 10 is arranged to contact the photosensitive drum 1 downstream of the transfer section and upstream of the charging section in the moving direction (rotation direction) of the photosensitive drum 1.

[0038] The brush component 10 is arranged such that its longitudinal direction is substantially parallel to the axis of rotation of the photosensitive drum 1. Examples of materials for the conductive yarn 11a include rayon, acrylic fiber, and polyester, in addition to nylon.

[0039] like Figure 2A As shown, in the state of a single brush member 10, i.e., without applying an external force to bend the conductive yarn 11a, the distance from the base fabric 11b to the tip of the conductive yarn 11a extending from the base fabric 11b is represented by L1. In the first exemplary embodiment, the distance L1 is 6.5 mm. The brush member 10 is arranged such that the base fabric 11b is fixed to a support member (not shown) arranged at a predetermined position in the imaging device 100 by a fixing member such as double-sided tape, and the tip of the conductive yarn 11a penetrates the photosensitive drum 1. In the first exemplary embodiment, the gap between the support member and the photosensitive drum 1 is fixed. The shortest distance from the base fabric 11b of the brush member 10 fixed to the support member to the photosensitive drum 1 is represented by L2. In the first exemplary embodiment, the difference between the shortest distance L2 and the distance L1 is defined as the penetration amount of the brush member 10 into the photosensitive drum 1. In the first exemplary embodiment, the penetration amount of the brush member 10 into the photosensitive drum 1 is 1 mm. Furthermore, in the first exemplary embodiment, as Figure 2A As shown, in the state of a single brush member 10, the length L3 of the brush member 10 in the circumferential direction (hereinafter referred to as the transverse direction) of the photosensitive drum 1 is 5 mm. Furthermore, in the first exemplary embodiment, the length of the brush member 10 in the longitudinal direction is 216 mm. The brush member 10 can thus contact the entire imaging area (the area where the toner image can be formed) on the photosensitive drum 1 along the rotation axis direction of the photosensitive drum 1. In the first exemplary embodiment, the thickness of each conductive yarn 11a is 2 denier, and the density of the conductive yarn 11a is 240 kF / inch. 2 (kF / inch 2 It is a unit of brush density, indicating the number of filaments per square inch. As described above, the brush member 10 is supported by a support member (not shown), arranged in a fixed position relative to the photosensitive drum 1, and the brush member 10 brushes the surface of the photosensitive drum 1 as the photosensitive drum 1 moves.

[0040] The brush component 10 captures (recovers) deposits (e.g., paper dust) transferred from the recording medium S to the photosensitive drum 1 at the transfer section, thereby reducing the amount of paper dust that moves to the charging section and the developing section downstream of the brush component 10 in the moving direction of the photosensitive drum 1.

[0041] In the first exemplary embodiment, the length of the brush member 10 in the circumferential direction (hereinafter referred to as the transverse direction) of the photosensitive drum 1 is set to 5 mm; however, the length L3 is not limited to this. For example, the length L3 can be appropriately changed according to the lifespan of the imaging device or processing cartridge. Of course, the longer the length of the brush member 10 in the transverse direction, the longer the brush member 10 can capture paper dust.

[0042] In the first exemplary embodiment, the length of the brush member 10 in the longitudinal direction is set to 216 mm; however, this length is not limited to this. For example, the length can be appropriately changed according to the maximum sheet width of the imaging device 100.

[0043] In the first exemplary embodiment, the brush member 10 has a fineness of 220T / 96F (meaning each strand is a bundle of 96 yarns with a thickness of 220 grams per 10,000 meters); however, the fineness of the brush member 10 is ideally determined taking into account the slippage characteristics of paper dust. When the fineness of the brush member 10 is small, the strength to prevent paper dust is weak, and paper dust easily slips over the brush member 10. This inhibits the charging of the photosensitive drum 1 by the charging roller 2, which may result in defective images. Conversely, when the fineness of the brush member 10 is too large, the brush member 10 cannot recover the toner and fine paper dust. As a result, density unevenness may occur due to uneven adhesion of the toner in the longitudinal direction of the charging roller 2, or defective images may occur due to charging failure at the portions where paper dust adheres.

[0044] In the first exemplary embodiment, the density of the brush component 10 is 240 kF / inch. 2 However, the density is ideally determined by considering both toner permeability and dust-trapping performance. More specifically, when the density of the brush component 10 is high, toner permeability deteriorates, and toner may accumulate (clump). Accumulated toner may scatter, causing defects such as contamination in the imaging device. Conversely, when the density of the brush component 10 is low, dust-trapping performance is reduced.

[0045] Regarding paper dust capture performance, the fineness and density of the conductive yarn 11a are preferably 1 to 6 denier and 150 to 350 kF / inch, respectively. 2 In terms of long lifespan, the length of the brush component 10 in the lateral direction is preferably 3 mm or longer.

[0046] The brush power supply E4 serves as the brush voltage application unit. Figure 3The brush is connected to the brush assembly 10. During imaging, a predetermined brush voltage (brush bias) is applied to the brush assembly 10 from the brush power supply E4. In the first exemplary embodiment, a negative DC voltage is applied to the brush assembly 10 as the brush voltage during imaging. In the first exemplary embodiment, as an example, the brush voltage during imaging is -350V.

[0047] 3. Image output operation

[0048] In a first exemplary embodiment, the imaging apparatus 100 performs an image output operation (job) in response to a start command from an external device (not shown), such as a personal computer. This image output operation is a series of operations that form an image on one or more recording media S. The job typically includes imaging processing (printing processing), pre-rotation processing, inter-sheet processing in the case of forming images on multiple recording media S, and post-rotation processing. Imaging processing is the period during which the formation of an electrostatic image on the photosensitive drum 1, the development of the electrostatic image (formation of a toner image), the transfer of the toner image, and the fixing of the toner image are actually performed. The term "during imaging" refers to this period. More specifically, the timing of imaging processing varies depending on the position where the formation of the electrostatic image, the formation of the toner image, the transfer of the toner image, and the fixing of the toner image are performed. Pre-rotation processing is the period of preparation operations performed before the imaging processing is performed. Inter-sheet processing is the period corresponding to the interval between recording media S and the next recording media S when imaging processing is performed continuously on multiple recording media S (during continuous imaging). Rotational post-processing is the period during which setup operations (preparation operations) are performed after imaging processing. The term "non-imaging period" refers to periods other than "imaging period," including rotational pre-processing, inter-sheet processing, and rotational post-processing, and also includes multiple rotational pre-processing. Multiple rotational pre-processing is a preparation operation performed when the imaging device 100 is turned on or resumed from a sleep state.

[0049] 4. Control Mode

[0050] Figure 3 This is a schematic block diagram illustrating the control mode of the main units of an imaging device 100 according to a first exemplary embodiment. The imaging device 100 includes a control unit 150. The control unit 150 includes a central processing unit (CPU) 151 (which is a computing control unit as a central device performing computational processing), a memory (storage device) 152 as a storage unit such as read-only memory (ROM) and random access memory (RAM), and an input / output unit (not shown) for controlling the transmission / reception of various elements connected to the control unit 150. The RAM stores, for example, sensor detection results and calculation results, and the ROM stores, for example, control programs and predetermined data tables.

[0051] The control unit 150 controls the overall operation of the imaging device 100. The control unit 150 controls, for example, the transmission / reception and timing of various electrical information signals to execute a predetermined imaging sequence. The control unit 150 is connected to various units of the imaging device 100. In a first exemplary embodiment, examples of units connected to the control unit 150 include a charging power supply E1, a developing power supply E2, a transfer power supply E3, a brush power supply E4, an exposure unit 4, and a drive motor 110.

[0052] 5. The effect of toner on brush components

[0053] Next, refer to Figure 4A and Figure 4B The behavior of the transfer-residual toner passing through the brush member 10 is described. First, the relationship between the potential difference between the potential of the brush member 10 and the surface potential of the photosensitive drum 1 at the contact portion and the polarity of the transfer-residual toner will be described.

[0054] like Figure 4A As shown, when the percentage of toner R (hereinafter referred to as normal polarity toner) charged to the normal polarity in the transfer-residual toner is high, and when the potential relationship of the electric field generated in the direction in which the normal polarity toner R adheres to the brush member 10 is such that the toner continuously accumulates on the brush member 10. Conversely, as Figure 4B As shown, when the percentage of toner R in the transfer-residual toner is high, and when there is a potential relationship where an electric field is generated in the direction where the normal polarity toner R does not adhere to the brush member 10, the normal polarity toner R passes through the brush member 10 without being held by it. The case where an electric field is generated in the direction where the normal polarity toner R does not adhere to the brush member 10 represents the case where an electric field is generated in the direction where the normal polarity toner R moves towards the photosensitive drum 1. In this case, the normal polarity toner R passes through the contact portion. Under this relationship, even when the polarity of the toner is reversed, only the polarity of the potential difference described above is reversed, and a phenomenon similar to the above-described phenomenon occurs. In the first exemplary embodiment, the control will be described when the percentage of the normal polarity toner R in the transfer-residual toner is high, as described below; however, this control is also applicable to the case where the percentage of toner charged to the opposite polarity (hereinafter referred to as the reverse polarity toner) is high.

[0055] As in the first exemplary embodiment, when the polarity is almost not reversed, for example, when the transfer bias applied to the transfer portion is relatively low, the percentage of toner charged to the normal polarity in the transfer-residual toner tends to increase. Conversely, when the polarity is easily reversed, for example, when the transfer bias is high, the percentage of anti-polarity toner in the transfer-residual toner tends to increase.

[0056] In the first exemplary embodiment, most of the transfer-residual toner is a normal polarity toner with a weakly negative (i.e., normal polarity) charge; however, due to the discharge between the transfer bias voltage and the surface potential of the photosensitive drum 1 at the transfer portion, a positively charged reverse polarity toner is partially mixed. The behavior of the normal polarity toner and the reverse polarity toner in the transfer-residual toner remaining on the surface of the photosensitive drum 1 at the contact portion will now be described.

[0057] During imaging, the surface of the photosensitive drum 1 is charged to a dark zone potential Vd of -700V.

[0058] The imaging portion on the photosensitive drum 1 is exposed by the exposure unit 4 to a bright area potential Vl of -100V. The non-imaging portion on the photosensitive drum 1 is also charged to approximately -100V through the transfer portion due to the discharge between the photosensitive drum 1 and the transfer roller 5, which is subjected to a transfer voltage of +1000V. Accordingly, the surface potential of the photosensitive drum 1 reaching the contact portion during imaging is approximately -100V. In the transfer-residual toner, the normally polar toner, charged to a negative polarity, passes through the contact portion and is electrostatically attracted to the photosensitive drum 1 due to the potential difference between the brush voltage (-350V) at the contact portion and the surface potential of the photosensitive drum 1 (approximately -100V). Conversely, in the transfer-residual toner, the reverse polarity toner, charged to the positive polarity, is electrostatically attracted to the brush member 10 after transfer due to the potential difference between the brush voltage (-350V) at the contact portion and the surface potential (approximately -100V) of the photosensitive drum 1, and adheres to the brush member 10.

[0059] As the photosensitive drum 1 rotates, the negative polarity toner, which has already passed through the charging section, is delivered to the developing section. In the non-imaging section, the negative polarity toner delivered to the developing section moves to the developing roller 31 due to the potential difference between the dark area potential (Vd) and the developing bias voltage (Vdc) on the surface of the photosensitive drum 1, and is then returned to the developing apparatus 3. Conversely, in the imaging section, the negative polarity toner delivered to the developing section does not move to the developing roller 31 due to the potential difference between the bright area potential (Vl) and the developing bias voltage (Vdc) on the surface of the photosensitive drum 1. As the photosensitive drum 1 rotates, the toner, as toner for the imaging section, is delivered to the transfer section and transferred to the recording medium S. As described above, the developing bias voltage is set to the potential between the dark area potential Vd and the bright area potential Vl.

[0060] The imaging apparatus 100 may further include a pre-exposure device, serving as a charge elimination unit, located downstream of the transfer portion and upstream of the charging portion in the rotational direction of the photosensitive drum 1, for eliminating charges on the surface of the photosensitive drum 1. The pre-exposure device optically eliminates the surface potential of the photosensitive drum 1 before the target portion of the photosensitive drum 1 enters the charging portion, thereby generating a stable discharge at the charging portion. Charge elimination includes removing (attenuating) at least a portion of the charge. In this example, the location exposed (subjected to charge elimination processing) by the pre-exposure device in the rotational direction of the photosensitive drum 1 is the charge elimination portion. It is desirable to perform charge elimination processing on the surface of the photosensitive drum 1 downstream of the contact portion and upstream of the charging portion in the rotational direction of the photosensitive drum 1, such that the toner that has passed through the contact portion passes through the charge elimination portion and is stably charged to a negative polarity by uniform discharge at the charging portion.

[0061] The effect of toner accumulation on the brush unit 10 on the image will now be described with reference to Table 1. In the image evaluation, an Office70 (trade name, manufactured by Canon) was used as the recording medium S, and a full-page halftone image was printed on 100 sheets. To check the amount of toner accumulated on the brush unit 10, the occurrence of defective images was examined. Defective images specifically indicate poor charging caused by toner slippage due to toner accumulation on the brush unit 10, or poor development caused by paper dust slippage. Poor charging is caused, for example, by toner slipping across the brush unit 10 and adhering to the charging roller 2. Poor development is caused, for example, by thin density and the appearance of streaks. Thin density occurs when paper dust that has slipped across the brush unit 10 is recycled to the developing unit 3 and inhibits toner charging. Streaks occur when paper dust adheres to the developing blade.

[0062] As shown in Table 1, when the normal polarity toner constitutes the majority of the transfer-residual toner as in the first exemplary embodiment, no defective images appear under the potential relationship where the transfer-residual toner passes through the contact portion, i.e., when the brush voltage is on the negative polarity side relative to the surface potential of the photosensitive drum 1. Conversely, under the potential relationship where the normal polarity toner adheres to the brush member 10, i.e., when the brush voltage is on the positive polarity side relative to the surface potential of the photosensitive drum 1, defective images appear.

[0063] Table 1

[0064] Surface potential of the photosensitive drum at the contact area brush voltage The occurrence of defective images -100V +350V NG -100V -350V OK

[0065] In a first exemplary embodiment, based on the above results, control is performed during imaging to achieve a potential relationship whereby the residual toner passes through the contact portion of the photosensitive drum 1 and contacts the brush member 10 without adhering to the brush member 10. This prevents the occurrence of defective images due to excessive accumulation of toner on the brush member 10.

[0066] 6. Control of toner discharge from brush parts

[0067] As described above, the transfer-residual toner contains a normal polarity toner and a reverse polarity toner charged to the opposite polarity. Therefore, for transfer-residual toners with a high percentage of normal polarity toner, even if a potential relationship is formed at the contact portion where the normal polarity toner passes through the contact portion, the reverse polarity toner may still accumulate on the brush member 10. Therefore, it is necessary to periodically transfer (discharge) the toner adhering to the brush member 10 onto the photosensitive drum 1 at appropriate timing.

[0068] As a method for discharging toner from the brush member 10 to the surface of the photosensitive drum 1, methods utilizing potential difference and methods utilizing changes in the orientation of the brush member 10 can be employed. The method using potential difference enables the toner to be discharged from the brush member 10 by establishing a potential relationship that generates an electric field in the direction in which the polarity of the primary toner held by the brush member 10 moves from the brush member 10 to the photosensitive drum 1. This is considered a method utilizing electricity.

[0069] Conversely, the method of changing the posture of the brush component 10 is a method of using physical force. More specifically, this is a method of removing toner adhering to the brush component 10 by intentionally causing a change in the posture of the brush component 10 at the timing of a change in the speed of the photosensitive drum 1, such as when the drive of the photosensitive drum 1 starts or stops. During the drive stop, no force is applied to the brush component 10 in the rotational direction of the photosensitive drum 1, such as... Figure 5A As shown, the brush member 10 receives only the reaction force from the photosensitive drum 1. Therefore, the brush member 10 adopts a posture that is substantially perpendicular to the photosensitive drum 1. When the photosensitive drum 1 is driven at a state where there is no potential difference between the brush member 10 and the photosensitive drum 1, the brush member 10 receives a static frictional force μN (where μ is the coefficient of static friction and N is the perpendicular resistance) along the rotation direction of the photosensitive drum 1, as shown. Figure 5B As shown, the brush member 10 is positioned in a downward-facing posture in the rotational direction of the photosensitive drum 1. Therefore, the posture of the brush member 10 during drive stop differs from that during rotary drive. Even when the operation changes from rotary drive to drive stop, a similar change in posture occurs. Figure 5B The posture shown becomes Figure 5AThe phenomenon shown is due to the posture. Changing the posture makes it possible to expel toners that are almost impossible to expel using only electricity (e.g., a potential difference). However, the surface of the photosensitive drum 1 is smooth in most cases and has a low coefficient of static friction μ, so the movement of the brush member 10 is minimal simply by utilizing the rotational drive and stopping of the photosensitive drum 1. According to this exemplary embodiment, the amount of movement of the tip of the brush member 10 is approximately 100 μm.

[0070] When the photosensitive drum 1 is driven with a potential difference existing between the brush component 10 and the photosensitive drum 1, in addition to the electrostatic force μN, the brush component 10 also receives an electrostatic attraction proportional to the potential difference ΔV between the brush component 10 and the photosensitive drum 1. Therefore, the brush component 10 adopts a posture that is more downstream in the rotational direction of the photosensitive drum 1 than when there is no potential difference, such as... Figure 5C As shown. Therefore, if a potential difference exists between the brush member 10 and the photosensitive drum 1 during drive stop and rotary drive, the posture change is significant. In this exemplary embodiment, the tip of the brush member 10 moves by approximately 1 mm, and the amount of toner discharged increases. Even when the operation changes from rotary drive to drive stop, a similar posture change occurs. Figure 5C The posture shown becomes Figure 5A The phenomenon shown is due to the posture. For toner accumulated on the base of the brush part 10 away from the photosensitive drum 1, the posture change makes it possible to effectively remove toner that is difficult to remove by static friction alone.

[0071] The effectiveness of toner ejection from the brush component 10 will now be described. To confirm the effectiveness of toner ejection, an Office70 (trade name, manufactured by Canon) was used as the recording medium S, and intermittent single-sheet printing operations of full-sided halftone images were repeated using the imaging device 100. A total of 500 sheets were printed, and the occurrence of defective images was checked. The ejection amount by utilizing potential difference and by utilizing changes in the posture of the brush component 10 were checked by attaching a semi-transparent polyester tape (manufactured by Nichiban Co., Ltd.) to the measurement target portion of the photosensitive drum 1. More specifically, the toner ejected onto the surface of the photosensitive drum 1 was transferred to the tape, and the toner was quantified by density when the tape was peeled off and attached to the paperboard. The density of the tape directly attached to the paperboard without being attached to the photosensitive drum 1 and the density of the tape attached to the paperboard after being attached to the measurement target portion were measured using a reflectance densitometer (TC-6MC-D, manufactured by Tokyo Denshoku Co., Ltd.), and the difference between the measured values ​​was recorded as density. Therefore, a high density value indicates a large amount of toner discharged.

[0072] Figure 6The potential relationships in the first comparative example, the second comparative example, and the first exemplary embodiment are shown. In the first comparative example, during the time period from the start of driving to the stop of driving, the potential relationship between the brush member 10 and the photosensitive drum 1 remains unchanged, and the discharge of the reverse polarity toner accumulated on the brush member 10 is not actively performed. In other words, in the first comparative example, the potential relationship between the brush member 10 and the photosensitive drum 1 is the potential relationship of normal polarity toner continuously passing through the contact portion.

[0073] In the second comparative example, the potential relationship between the brush member 10 and the photosensitive drum 1 is set as follows: the potential relationship in the section where the transfer-residual toner passes through the contact portion during imaging is opposite to the potential relationship in other sections (i.e., the section where the transfer-residual toner passes through the transfer portion of the photosensitive drum 1 and then through the contact portion during non-imaging periods). In other words, in the second comparative example, the potential relationship is set to the potential relationship of normal polarity toner accumulated on the brush member 10 passing through the contact portion in the section where the transfer-residual toner passes through the contact portion, and the potential relationship is set to the potential relationship of normal polarity toner adhering to the photosensitive drum 1 during non-imaging periods. In other words, in the second comparative example, the potential relationship is set to the potential relationship of reverse polarity toner being discharged to the surface of the photosensitive drum 1. However, in the second comparative example, the timing when the potential relationship is opposite to the potential relationship of the section where the transfer-residual toner passes through the contact portion does not include the drive start time and drive stop time. In other words, in the first comparative example, there is no moment when the reverse polarity toner is electrically discharged at the contact portion, while in the second comparative example, there is a moment when the reverse polarity toner is electrically discharged at the contact portion. Furthermore, in both the first and second comparative examples, the potential relationship for the electrical discharge of the reverse polarity toner at the contact portion is not realized during the rotation drive when physical discharge occurs and during the stop rotation drive. Therefore, in both the first and second comparative examples, the timing of the electrical discharge of the reverse polarity toner is not considered when the speed of the photosensitive drum 1 is switched. In the second comparative example, discharge is considered only when the photosensitive drum 1 rotates at a constant speed.

[0074] In contrast, in the first exemplary embodiment, except in the case of the second comparative example, the potential relationship between the brush member 10 and the photosensitive drum 1 at the start and stop of the drive is opposite to the potential relationship during imaging. At the start and stop of the drive, the reverse polarity toner accumulated on the brush member 10 in the area where the transfer-residual toner passes through the contact portion is thus discharged to the photosensitive drum 1. At this time, the brush voltage to be applied is set to +150V.

[0075] In the first comparative example, the second comparative example, and the first exemplary embodiment, when the transfer voltage is adjusted and the percentage of normal polarity toner in the transfer-residual toner is high, the toner discharge effect is confirmed. The potential relationship between the brush member 10 and the photosensitive drum 1 in the area where the transfer-residual toner passes through the contact portion is set to the potential relationship where the normal polarity toner passes through the contact portion.

[0076] Figure 7 It is a timing diagram of the voltage applied from the start of the driving of the photosensitive drum 1 through the imaging operation until the driving of the photosensitive drum 1 stops in the first exemplary embodiment.

[0077] Figure 7 From top to bottom, the following are shown in sequence: the on / off state of the drive motor 110's rotation drive of the photosensitive drum 1, the charging voltage applied from the charging power supply E1 to the charging roller 2, and the laser emission of the exposure unit 4 to the photosensitive drum 1. Figure 7 The time transition of (A) the brush voltage (brush component potential) applied to the brush component 10 from the brush power supply E4, (B) the surface potential of the photosensitive drum 1 at the contact portion, and the difference between the brush voltage at the contact portion and the surface potential of the photosensitive drum 1 ((A)-(B)) is also shown.

[0078] When in Figure 7When a print command is received before time T1, a brush voltage is applied to the brush member 10 at time T1. In the first exemplary embodiment, the brush voltage is set to +150V. At time T2, the rotation drive of the photosensitive drum 1 begins simultaneously with the application of the brush voltage. Subsequently, at time T3, a charging voltage of -1200V is applied to the charging roller 2 to charge the surface of the photosensitive drum 1. At time T4, when the surface of the photosensitive drum 1 charged at time T3 reaches the contact portion, the brush voltage switches from +150V to -350V. The potential difference between the potential of the brush member 10 formed at the contact portion and the potential of the surface of the photosensitive drum 1 is equal to the brush voltage until time T4. Therefore, the discharge of toner from the brush member 10 can be controlled by switching the brush voltage. In the first exemplary embodiment, an operation to promote the discharge of negative polarity toner adhering to the brush member 10 is performed until time T4. After time T4, a brush voltage of -350V is applied to the brush member 10 until time T10 when imaging ends. During this period, a transfer bias voltage is applied, and the normal polarity toner reaches the contact portion as the transfer-residual toner. Therefore, the brush voltage is controlled to be negative polarity to allow the transfer-residual toner to pass through the contact portion. At time T5, imaging begins, and exposure for imaging is performed appropriately. At time T6, when the photosensitive drum 1 exposed at time T5 reaches the contact portion, the transfer-residual toner has essentially reached the contact portion. At this time, as described above, a negative polarity brush voltage has been applied to the brush member 10, thereby allowing the transfer-residual toner to pass through the contact portion. Subsequently, imaging ends at time T7. At time T8, when the photosensitive drum 1 exposed at time T7 reaches the contact portion, the transfer-residual toner has essentially not reached the contact portion. Imaging ends at time T8, and therefore, post-image rotation operation is performed after time T8. At time T9, the charging voltage is turned off. At time T10, when the surface of the photosensitive drum 1, whose charging voltage was turned off at time T9, reaches the contact portion, the brush voltage switches from -350V to +150V. Subsequently, at time T11, the drive motor 110 is turned off. At this time, with a brush voltage of +150V applied, a positive potential difference is formed at the contact portion between the potential of the brush component 10 and the surface potential of the photosensitive drum 1. Accordingly, through the rotational stop operation of the photosensitive drum 1 and the aforementioned potential difference, the reverse polarity toner can be actively discharged from the brush component 10. At time T12, the brush voltage is turned off.

[0079] Since the surface potential of the photosensitive drum 1 is not formed at the contact portion until time T3, it is unnecessary to adjust the surface potential of the photosensitive drum 1 before time T3. During the time period from time T3 to time T12, the surface potential of the photosensitive drum 1 can be adjusted by controlling the pre-exposure device, transfer bias, etc.

[0080] Table 2 shows the determination results of toner discharge from the brush member 10 to the surface of the photosensitive drum 1 in the first comparative example, the second comparative example, and the first exemplary embodiment.

[0081] Table 2

[0082]

[0083] As shown in Table 2, in the first comparative example, the reverse polarity toner was discharged from the brush member 10 onto the surface of the photosensitive drum 1 only when the posture changed during drive start and stop, and the density of the discharged portion was 10. The results show that even without considering electrical effects, a small amount of reverse polarity toner was discharged when the posture changed during drive start and stop. However, in the first comparative example, a sufficient amount of toner accumulated on the brush member 10 in the 125th sheet, resulting in defective images.

[0084] In the second comparative example, as in the first comparative example, when the posture changes during drive start and stop, the reverse polarity toner is discharged from the brush member 10 to the surface of the photosensitive drum 1. Furthermore, to discharge the reverse polarity toner, the potential difference between the photosensitive drum 1 and the brush member 10 is reversed during non-imaging periods (excluding drive start and stop). As in the first comparative example, the density of the discharged portion during posture change discharge is 10. Furthermore, the density of the discharged portion during the interval using the potential difference is 22. Compared to discharge by posture change alone, a large amount of reverse polarity toner is discharged, but a defective image appears in the 256th sheet. Therefore, it is determined to be NG (Not Good). When the interval for discharge performed by using the potential difference becomes longer, i.e., when non-imaging is performed for a long time, the discharge amount discharged from the brush member 10 increases, but the rotation time of the photosensitive drum 1 during non-imaging periods increases, which reduces productivity.

[0085] Conversely, in the first exemplary embodiment, except in the case of the second comparative example, potential difference and posture change at the start and stop of the drive were used to discharge the reverse polarity toner from the brush member 10. In addition to the posture change at the start and stop of the drive, the total density of the discharge using the potential difference was 55. After 500 sheets, no defective images appeared. Therefore, it was determined to be OK.

[0086] The results obtained from Table 2 are summarized below. From the results of the first and second comparative examples, it can be seen that the method of using the potential difference between the reverse brush member 10 and the photosensitive drum 1 is effective in discharging toner from the brush member 10. However, comparing the second comparative example with the first exemplary embodiment, the discharging performance in the second comparative example is insufficient. The toner discharged from the brush member 10 using the potential difference is the toner accumulated on the brush member 10 that adheres to the tips of the brush bristles near the photosensitive drum 1, and the potential difference has almost no effect on the toner accumulated in the area near the root of the photosensitive drum 1. Conversely, when toner is discharged only by changing the posture, the toner accumulated in the area far from the photosensitive drum 1 also moves; however, the amount of toner discharged is small because no potential difference is formed that causes the toner to move from the brush member to the photosensitive drum 1. Therefore, as in the first exemplary embodiment, when a potential difference for discharging accumulated toner is formed while the toner attached to the brush member 10 is moved as a whole by changing the posture of the brush member 10, the toner can be effectively discharged.

[0087] As described above, the construction according to the first exemplary embodiment includes the following components. An imaging apparatus 100 that performs an imaging operation to form an image on a recording medium S includes a rotatable photosensitive drum 1 and a charging roller 2 configured to charge the surface of the photosensitive drum 1 at a charging portion facing the photosensitive drum 1. The imaging apparatus 100 includes an exposure unit 4 configured to expose the surface of the photosensitive drum 1 charged by the charging roller 2 to form an electrostatic latent image on the surface of the photosensitive drum 1. The imaging apparatus 100 includes a developing roller 31 and a transfer roller 5. The developing roller is configured to develop the electrostatic latent image into a developing image by supplying a developer charged to normal polarity to the surface of the photosensitive drum 1. The transfer roller is configured to form a transfer portion by contacting the photosensitive drum 1 and to transfer the developing image from the photosensitive drum 1 to the recording medium S at the transfer portion. Imaging apparatus 100 includes a brush member 10 and a brush voltage application unit (brush power supply) E4. The brush member is configured to form a contact portion downstream of the transfer portion and upstream of the charging portion in the rotational direction of the photosensitive drum 1, and to contact the photosensitive drum 1 at the contact portion. The brush voltage application unit is configured to apply a brush voltage to the brush member 10. Imaging apparatus 100 includes a drive motor 110 configured to rotatably drive the photosensitive drum 1, and a control unit 150 configured to control the brush power supply E4 and the drive motor 110. After the developer image formed on the surface of the photosensitive drum 1 is transferred to the recording medium S at the transfer portion, the developer remaining on the surface of the photosensitive drum 1 is recovered by the developing roller 31. During imaging operation, the control unit 150 controls the direction of the electric field generated in the first region of the photosensitive drum 1 where the transfer portion is formed by timing the contact portion in the following manner. The direction of the electric field generated in the first region is different from the direction of the electric field generated in the second region of the contact portion of the photosensitive drum 1 during non-imaging operations when the operation changes from a first operation where the photosensitive drum 1 rotates at a first speed to a second operation where the photosensitive drum 1 rotates at a second speed. At this time, the control unit 150 can rotate the photosensitive drum 1 at the first speed and stop it at the second speed during imaging operations, or it can start rotating the photosensitive drum 1 at the first speed and then rotate it at the second speed during imaging operations. Furthermore, even after the photosensitive drum 1 stops, it is desirable to maintain the aforementioned relationship of the potential difference between the brush member 10 and the photosensitive drum 1. It is desirable to maintain the aforementioned relationship of the potential difference between the brush member 10 and the photosensitive drum 1 before the photosensitive drum 1 is driven.

[0088] In a first exemplary embodiment, when the first region of the photosensitive drum 1 forming the transfer portion passes the contact portion during imaging operation, the control unit 150 preferably performs control in such a manner as follows: The control unit 150 performs control such that the electric field generated in the first region relative to the brush voltage applied to the brush member 10 is directed in the direction along which the developer charged to normal polarity moves from the brush member 10 to the surface of the photosensitive drum 1.

[0089] In the above configuration, the control is performed to effectively discharge the toner adhering to the brush member 10 that abuts against the photosensitive drum 1, thereby preventing defective images.

[0090] In the first exemplary embodiment, the potential difference in the contact area between the transfer-residual toner is opposite to the potential difference at the start and stop of the drive; however, the timing of the potential difference reversal is not limited to the start or stop of the drive. For example, when the speed between the photosensitive drum 1 and the brush member 10 changes, the posture of the brush member 10 changes, so the potential relationship between the photosensitive drum 1 and the brush member 10 can be reversed when the speed changes. For example, when the speed decreases from the speed in normal imaging mode (1 / 1 speed) to the speed in a low-speed mode (e.g., thick sheet printing mode) (1 / 2 speed) or vice versa, the discharge operation according to the first exemplary embodiment can be employed. In the first exemplary embodiment, the brush member 10 is used as a primary toner recovery component; however, the brush member 10 can also be used as a recovery component for temporarily recovering toner and discharging toner onto the surface of the photosensitive drum 1 at a specific timing.

[0091] A second exemplary embodiment of this disclosure will now be described. The basic construction and operation of the imaging device according to the second exemplary embodiment are substantially the same as those according to the first exemplary embodiment. Therefore, elements having the same or equivalent functions and constructions as those in the imaging device according to the first exemplary embodiment are indicated by the same reference numerals, and detailed descriptions of these elements are omitted.

[0092] In the first exemplary embodiment, a configuration using a drive start operation and a drive stop operation accompanying a general printing operation is described. In the second exemplary embodiment, under the potential relationship of the reverse polarity toner being discharged from the brush member 10 to the photosensitive drum 1, as... Figure 8 The drive start operation and drive stop operation are repeated as shown. In the first exemplary embodiment, the discharge at drive start and the discharge at drive stop are each performed once per printing operation, while in the second exemplary embodiment, the discharge operation can be performed multiple times. Therefore, the discharge volume per printing operation can be increased. Considering the lateral length of the brush member 10, the effect can be achieved by moving the photosensitive drum 1 by a length substantially equal to the lateral length of the brush member 10 each time. More specifically, in the second exemplary embodiment, the lateral length L3 of the brush member 10 is 5 mm. Therefore, the moving distance of the surface of the photosensitive drum 1 each time is set to 5 mm. The moving distance is preferably about 1 mm to about 8 mm. Furthermore, it is necessary to move the photosensitive drum 1 a sufficient number of times to achieve the effect of scattering the toner in the brush member 10.

[0093] When the photosensitive drum 1 moves five times, toner can be effectively discharged from the brush member 10. In the second exemplary embodiment, the photosensitive drum 1 is moved five times during non-imaging periods when it stops in operation after rotation. Furthermore, when the recording medium is jammed, the photosensitive drum 1 is moved ten times because a large amount of toner adheres to the brush member 10.

[0094] As described above, in the second exemplary embodiment, performing control to more effectively discharge toner adhering to the brush member 10 abutting against the photosensitive drum 1 makes it possible to prevent defective images.

[0095] A third exemplary embodiment of this disclosure will now be described. The basic construction and operation of the imaging device according to the third exemplary embodiment are substantially the same as those according to each of the first and second exemplary embodiments. Therefore, elements having the same or equivalent functions and constructions as those in the imaging devices according to the first and second exemplary embodiments are indicated by the same reference numerals, and detailed descriptions of these elements are omitted.

[0096] In the first and second exemplary embodiments, configurations using drive start and drive stop operations accompanying general printing operations are described. In the third exemplary embodiment, under the potential relationship of the reverse polarity toner discharged from the brush member 10 to the photosensitive drum 1, as... Figure 9 The same forward and reverse rotation operations as in the printing operation are performed. In the first and second exemplary embodiments, discharge is performed by driving and stopping the forward rotation, while in the third exemplary embodiment, driving and stopping the reverse rotation is performed in addition to the forward rotation. Therefore, the posture change of the brush member 10 in the reverse direction can also be used. This makes it possible to increase the amount of toner discharged. In the third exemplary embodiment, the forward and reverse rotation operations of the photosensitive drum 1 are performed alternately to enhance the effect of discharging toner from the brush member 10. More specifically, after performing the forward rotation of the photosensitive drum 1, a reverse rotation is performed, and then the forward rotation is performed again. The number of forward rotations and the number of reverse rotations can be appropriately set, but it is preferred that each be set to two. Furthermore, the movement distance in the second rotation is less than the movement distance in the first rotation, which makes it possible to achieve a large toner discharge effect. In other words, maximizing the movement distance in the first rotation makes it possible to increase the discharge volume. The toner discharged in the rotation operation slides over the contact portion when the photosensitive drum 1 is started again. Therefore, the toner can be discharged more efficiently.

[0097] As described above, in the third exemplary embodiment, performing control to more effectively discharge toner adhering to the brush member 10 abutting against the photosensitive drum 1 makes it possible to prevent defective images.

[0098] Implementing controls to effectively remove toner adhering to the brush components that rest against the photosensitive drum prevents defective images.

[0099] While the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. An imaging apparatus that performs an imaging operation to form an image on a transfer receiving component, the imaging apparatus comprising: Rotatable image carrier; A charging component is configured to charge the surface of the image carrier at a charging portion facing the image carrier. A charging voltage application unit is configured to apply a charging voltage to a charging component, wherein the charging voltage is a DC voltage. An exposure unit is configured to expose the surface of an image carrier charged by a charging component to form an electrostatic latent image on the surface of the image carrier. The developing unit is configured to develop an electrostatic latent image into a developer image by supplying a developer agent charged to normal polarity to the surface of an image carrier. A transfer unit is configured to form a transfer portion by contacting an image carrier, and to transfer a developer image from the image carrier to a transfer receiving unit at the transfer portion. The brush component is configured to form a contact portion on the downstream side of the transfer portion and the upstream side of the charging portion in the rotational direction of the image carrier, and to contact the image carrier at the contact portion. A brush voltage application unit configured to apply a brush voltage to a brush component; A driving unit configured to rotatably drive an image carrier; and The control unit is configured to control the charging voltage application unit, the brush voltage application unit, and the drive unit. In this process, the developer image formed on the surface of the image carrier is transferred to the transfer receiving unit at the transfer section, and the developer remaining on the surface of the image carrier is recovered by the developing unit. The control unit performs control such that, during an imaging operation, when the first region of the image carrier forming the transfer portion passes through the contact portion, the direction of the electric field generated in the first region relative to the brush voltage applied to the brush member is different from the direction of the electric field generated in the second region of the image carrier forming the contact portion relative to the brush voltage applied to the brush member during a non-imaging operation different from the imaging operation, specifically during a second operation where the operation changes from a first operation where the image carrier rotates at a first speed to a second operation where the image carrier rotates at a second speed different from the first speed. The control unit performs control such that, during imaging operation, while the first region passes through the contact portion, the electric field generated in the first region relative to the brush voltage applied to the brush member points in the direction along which the developer charged to normal polarity moves from the brush member to the surface of the image carrier.

2. The imaging device of claim 1, wherein, The control unit performs control to make the second speed lower than the first speed.

3. The imaging device of claim 1, wherein, The control unit performs control to make the second speed higher than the first speed.

4. The imaging device of claim 2, wherein, During the imaging operation, the control unit performs control to rotate the image carrier at a first speed.

5. The imaging device of claim 3, wherein, During the imaging operation, the control unit performs control to rotate the image carrier at a second speed.

6. The imaging device of claim 1, wherein, The interval between the operation and the second operation is either the interval between the state of the first state where the rotation of the image carrier stops and the state of the image carrier being driven, or the interval between the state of the second state and the state of the first state.

7. The imaging device of claim 1, wherein, The control unit performs control to make the rotation direction of the image carrier rotating at the first speed opposite to the rotation direction of the image carrier rotating at the second speed.

8. The imaging device according to claim 1, wherein, The developer is a single-component developer.

Images