imaging device

Abstract

The present invention relates to an image forming apparatus comprising: a rotatable image bearing member; a developing member; a transfer member; and a brush which contacts a surface of the image bearing member at a contact portion located downstream of a transfer portion and upstream of a developing portion with respect to a rotation direction of the image bearing member. Toner which is not transferred onto a toner image receiving member is collected by the developing member. In a charging sequence, the toner is located on a same side as a normal charge polarity of the toner with respect to the brush. At the contact portion, a maximum value of a contact pressure is 0.7 gf / mm 2 The above and 3.5 gf / mm 2 Hereinafter, a maximum contact area ratio is 18% or more and 74% or less, and a Clark-Evans index of the brush is 1 or more.

Description

Technical Field

[0001] The present invention relates to an imaging apparatus for forming an image on a recording material. Background Technology

[0002] In electrophotographic imaging devices, there is a known configuration known as simultaneous development and cleaning or a cleaner-less type. Even after the toner image has been transferred from the image carrier (e.g., a photosensitive drum) to the toner image receiving component (recording material or intermediate transfer component), residual toner remaining on the surface of the image carrier is not collected by the cleaning equipment, but is collected by the developing component (e.g., a developing roller) during the subsequent development process.

[0003] Japanese Patent Application Publication No. (JP-A) 2010-14982 discloses a structure in which, in an imaging apparatus of the cleanerless type, a brush member for dispersing residual toner deposited on a photosensitive drum is positioned downstream of the transfer roller and upstream of the charging brush relative to the rotational direction of the photosensitive drum. According to JP-A 2010-14982, the residual toner, distributed in the same pattern as the toner image transferred onto the recording material, is dispersed by the brush member. Therefore, the behavior of the residual toner on the charging or developing equipment is homogenized, making it less likely for afterimages caused by the residual toner to appear on the recording material.

[0004] Typically, the residual toner remaining on the surface of the image-bearing component after the transfer process includes toner particles with the normal polarity (normal charge polarity), toner particles with the opposite polarity, and toner particles with near-zero charge. When the residual toner reaches the charging or developing component while in a state of wide charge distribution, various problems can occur, such as poor charging due to contamination of the charging roller and afterimages (hazy images) caused by poor collection of residual toner by the developing component.

[0005] Therefore, the brush member is positioned downstream of the transfer member and upstream of the charging member, relative to the rotation direction of the image carrier member. This is to stabilize the charge distribution of the residual toner in the normal polarity by placing it between the transfer and charging portions of the image carrier member. However, depending on the contact conditions between the brush member and the image carrier member, in some cases the residual toner is not sufficiently charged to the normal polarity. Alternatively, the residual toner is concentrated through a portion of the brush member and distributed in a stripe pattern, making it impossible to suppress the deposition of residual toner on the charging member in some cases. Summary of the Invention

[0006] Therefore, the main objective of this invention is to provide an imaging device capable of stabilizing the charge distribution of residual toner in the normal polarity.

[0007] Another object of the present invention is to provide an imaging apparatus that can suppress the occurrence of charging defects in a construction in which a brush member is provided in contact with an image-carrying member.

[0008] According to one aspect of the present invention, an imaging apparatus is provided, comprising: a rotatable image carrier member; a developing member configured to develop an electrostatic latent image formed on the surface of the image carrier member using a toner at a developing section; a transfer member configured to transfer a toner image obtained by developing the electrostatic latent image by the developing member from the image carrier member to a toner image receiving member at a transfer section; and a brush contacting the surface of the image carrier member at a contact portion located downstream of the transfer section and upstream of the developing section relative to the rotational direction of the image carrier member, wherein toner not transferred to the toner image receiving member is collected by the developing member, wherein in the charging sequence, the toner is located on the side with the same normal charge polarity as the toner relative to the brush, and wherein, at the contact portion, the maximum value of the contact pressure is 0.7 gf / mm. 2 Above and 3.5gf / mm 2 The following conditions apply: the maximum area ratio is 18% or higher and 74% or lower, and the Clark-Evans index is 1 or higher.

[0009] According to another aspect of the present invention, an imaging apparatus is provided, comprising: a rotatable image carrier member; a developing member configured to develop an electrostatic latent image formed on the surface of the image carrier member using a toner at a developing section; a transfer member configured to transfer a toner image obtained by developing the electrostatic latent image by the developing member from the image carrier member to a toner image receiving member at a transfer section; a brush contacting the surface of the image carrier member at a contact portion located downstream of the transfer member and upstream of the developing member relative to the rotational direction of the image carrier member; and a voltage applying device, wherein toner not transferred to the toner image receiving member is collected by the developing member, wherein the voltage applied to the brush by the voltage applying device is located on the same side as the normal charge polarity of the toner relative to the surface potential of the image carrier member, and wherein, at the contact portion, the maximum value of the contact pressure is 0.7 gf / mm. 2 Above and 3.5gf / mm 2 The following conditions apply: the maximum area ratio is 18% or higher and 74% or lower, and the Clark-Evans index is 1 or higher.

[0010] According to another aspect of the present invention, an imaging apparatus is provided, comprising: a rotatable image carrier member; a charging member that contacts the image carrier member to form a charging portion and is configured to charge the surface of the image carrier member at the charging portion; a developing member configured to develop an electrostatic latent image formed on the surface of the image carrier member using a toner; a transfer member configured to transfer a toner image obtained by developing the electrostatic latent image by the developing member from the image carrier member to a toner image receiving member at a transfer portion; and a brush disposed in a rotational direction relative to the image carrier member at the transfer portion. The contact portion at the downstream end of the brush and the upstream end of the charging end contacts the surface of the image carrier member and is configured to charge the toner that has not been transferred to the toner image receiving member, wherein the toner that has not been transferred to the toner image receiving member is collected by the developing member, wherein the contact pressure between the brush and the image carrier member at the upstream end of the brush in the contact portion is higher than the contact pressure between the brush and the image carrier member at the downstream end of the brush in the contact portion relative to the rotation direction, and wherein the contact area ratio between the brush and the image carrier member at the upstream end of the brush is greater than the contact area ratio between the brush and the image carrier member at the downstream end of the brush.

[0011] According to another aspect of the present invention, an imaging apparatus is provided, comprising: a rotatable image carrier member; a charging member that contacts the image carrier member to form a charging portion and is configured to charge the surface of the image carrier member at the charging portion; a developing member configured to develop an electrostatic latent image formed on the surface of the image carrier member using a toner; a transfer member configured to transfer a toner image obtained by developing the electrostatic latent image by the developing member from the image carrier member to a toner image receiving member at the transfer portion; and a brush disposed relative to the image carrier member. The rotation direction of the component is located at the contact portion downstream of the transfer section and upstream of the charging section, which contacts the surface of the image carrier member, and is configured to charge the toner that has not been transferred to the toner image receiving member, wherein the toner that has not been transferred to the toner image receiving member is collected by the developing member, and wherein the following relationship is satisfied when the amount of penetration of the brush into the surface of the image carrier member at the upstream end of the brush relative to the rotation direction is δ1 (mm) and the amount of penetration of the brush into the surface of the image carrier member at the downstream end of the brush relative to the rotation direction is δ2 (mm).

[0012] Other features of the invention will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings. Attached Figure Description

[0013] Figure 1 It is a graph showing the relationship between the peak pressure of the brush component and the maximum contact area ratio.

[0014] Figure 2 This is a schematic diagram of an imaging apparatus according to the first embodiment.

[0015] Figure 3 Part (a) is a front view of the brush component in the first embodiment. Figure 3 Parts (b) and (c) are cross-sectional views of the brush component in the first embodiment.

[0016] Figure 4 This is a schematic diagram illustrating a method for measuring the vertical resistance (normal reaction) received by the brush component.

[0017] Figure 5 This is a schematic diagram illustrating the observation method using a brush component with a glass plate.

[0018] Figure 6 This is a schematic diagram illustrating the calculation method for peak pressure.

[0019] Figure 7 Part (a) is a schematic diagram showing an example of the brush contact portion as viewed using a glass plate. Figure 7 Part (b) is a schematic diagram illustrating the calculation method for the contact area ratio. Figure 7 Part (c) is a schematic diagram illustrating the calculation method of the Clark-Evans index.

[0020] Figure 8 This is a schematic diagram of the imaging unit in Example 1.

[0021] Figure 9 yes Figure 8 A magnified view of a portion of it.

[0022] Figure 10 Part (a) is a schematic diagram of the brush contact portion in Example 2. Figure 10 Part (b) is a schematic diagram of the photosensitive drum surface passing through the brush contact portion in Reference Example 2.

[0023] Figure 11 This is a schematic diagram of the imaging unit in the first embodiment.

[0024] Figure 12 yes Figure 11 A magnified view of a portion of it.

[0025] Figure 13 This is a schematic diagram of the brush component in the second embodiment.

[0026] Figure 14 This is a schematic diagram of the brush component in the second embodiment.

[0027] Figure 15 This is a schematic diagram illustrating the state of increased intrusion of the brush member in the second embodiment.

[0028] Figure 16 This is a schematic diagram of the imaging unit in the third embodiment.

[0029] Figure 17 yes Figure 16 A magnified view of a portion of it.

[0030] Figure 18 This is a schematic diagram illustrating the arrangement of the brush components in the fourth embodiment.

[0031] Figure 19 This is a schematic diagram of an imaging apparatus according to the fourth embodiment.

[0032] Figure 20 This is a schematic diagram of the imaging unit in the fourth embodiment.

[0033] Figure 21 Parts (a) and (b) are perspective and sectional views of the latent image unit in the fourth embodiment, respectively. Figure 21 Part (c) is a schematic diagram of the brush contact portion viewed from the upstream side of the rotation direction of the photosensitive drum in the fourth embodiment.

[0034] Figure 22 Parts (a) and (b) are cross-sectional views showing the brush member in the fourth embodiment, wherein part (a) shows the state with only the brush member and part (b) shows the state with the brush member in contact with the photosensitive drum.

[0035] Figure 23 Parts (a) and (b) are schematic diagrams illustrating the calculation method of the Clark-Evans index.

[0036] Figure 24 Parts (a) and (b) are schematic diagrams illustrating the calculation method for the contact pressure of the brush component.

[0037] Figure 25 This is a schematic diagram illustrating the calculation method for the contact area ratio of brush components.

[0038] Figure 26 Part (a) is a graph showing the relationship between contact pressure and the short side (lateral) direction in the fourth embodiment. Figure 26 Part (b) is a graph showing the relationship between the contact area ratio and the short side direction in the fourth embodiment. Figure 26 Part (c) is a graph showing the relationship between contact pressure and contact area ratio in the fourth embodiment.

[0039] Figure 27 Parts (a) to (c) are schematic diagrams illustrating the situation where the toner passes through the brush component in a stripe shape.

[0040] Figure 28 Parts (a) to (d) are schematic diagrams illustrating the operation of the brush member in the fourth embodiment.

[0041] Figure 29 Part (a) is a schematic diagram of the brush member in the fifth embodiment as viewed from the free end side of the bristle material. Figure 29 Part (b) is a schematic diagram of the brush member in the fourth embodiment as viewed from the free end side of the bristle material.

[0042] Figure 30 Part (a) is a schematic diagram of the brush member in the sixth embodiment as viewed from the free end side of the bristle material. Figure 30 Part (b) is a schematic diagram of the brush member in the fourth embodiment as viewed from the free end side of the bristle material.

[0043] Figure 31 This is a schematic diagram illustrating the method for calculating the intrusion amount of the brush component in the seventh embodiment. Detailed Implementation

[0044] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0045] <First Embodiment>

[0046] The following will use Figure 2 An overview of the imaging apparatus 100 according to the first embodiment is described below. The imaging apparatus 100 is a monochrome printer for forming a monochrome image on a sheet S based on image information received from an external device. Various sheets of different sizes and materials can be used as the sheet S (which is the recording material), including paper such as plain paper or thick paper; plastic film; cloth; surface-treated sheet materials, such as coated paper; sheet materials of special shapes, such as envelopes or index paper; and so on.

[0047] like Figure 2 As shown, the imaging apparatus 100 includes an electrophotographic imaging unit 101 for forming an image on a sheet S, and a sheet feeding mechanism (6, 8, 12) for feeding and transporting the sheet S. The imaging unit 101 includes a photosensitive drum 1 as an image carrying member, a charging roller 2 as a charging device, an exposure device 3 as an exposure device, a developing device 4 as a developing device, a transfer roller 5 as a transfer device, a brush member 11, and a fixing device 9 as a fixing device.

[0048] The photosensitive drum 1 is an electrophotographic photosensitive component formed into a drum shape. The charging roller 2 is a charging component of an example contact structure, wherein the charging roller 2 contacts the photosensitive drum 1. The contact portion between the charging roller 2 and the photosensitive drum 1 is the charging portion P2 (charging position) in which charging of the surface of the photosensitive drum 1 is performed.

[0049] The developing apparatus 4 includes a developing roller 41, a supply roller 42, a stirring member 43, a developing blade 44, and a toner container 45. The developing roller 41 is a developing member or developer-carrying member used to supply toner T to the developing section P4 (developing position) where the developing roller 41 and the photosensitive drum are opposite each other, by rotating while carrying toner T. In this embodiment, a so-called contact developing type is used, where the toner layer carried on the developing roller 41 contacts the surface of the photosensitive drum 1 at the developing section P4. The developing roller 41 is arranged at the opening of the toner container 45, which is located opposite the photosensitive drum 1. The supply roller 42 supplies (applies) the toner T from the toner container 45 to the developing roller 41. The stirring member 43 is arranged in the toner container 45 and agitates the toner T in the toner container 45 by being rotated. The toner container 45 is a container for holding the toner T as a developer. The developing blade 44 contacts the surface of the developing roller 41, which rotates toward the developing section P4, from the inside of the toner container 45 with a predetermined pressing force. The developing blade 44 is formed of a material (e.g., iron or copper) that is on the positive polarity side (non-normal polarity side) relative to the main component of the toner (binder resin) in the charging sequence. As a result, the toner T is rubbed and charged to the normal polarity (normal charge polarity) by friction with the developing blade 44.

[0050] The transfer roller 5 is arranged to contact the surface of the photosensitive drum 1. The clamping part between the transfer roller 5 and the photosensitive drum 1 is the transfer part 5 in which the toner image is transferred from the photosensitive drum 1 to the sheet S.

[0051] The brush member 11 is arranged downstream of the transfer section P5 and upstream of the charging section P2 relative to the rotation direction R1 of the photosensitive drum 1. The brush member 11 is arranged to contact the surface of the photosensitive drum 1 under predetermined contact conditions. Details of the brush member 11 will be described later.

[0052] The fixing device 9 includes a fixing roller or flexible fixing film as a first rotatable member, a pressing roller as a second rotatable member that contacts the first rotatable member with a predetermined pressing pressure, and a heating device for heating an image on a sheet S through the first rotatable member. As the heating device, a halogen lamp that generates radiant heat or a heater substrate with a pattern of heating resistors formed on a ceramic substrate can be used.

[0053] The sheet feeding mechanism includes a cartridge 6, a feed (transfer) roller pair 8, and a discharge roller pair 12. The cartridge 6 is a stacking section in which stacked sheets S are formed. The feed roller pair 8 is a feeding member for feeding the sheet S fed from the cartridge 6 to the transfer section P5. The discharge roller pair 12 is a discharge member for discharging the sheet S on which the imaging section 101 forms an image.

[0054] The following is a summary of the imaging operation performed by the imaging device 100. When an execution command for the imaging operation is provided to the imaging device 100, the photosensitive drum 1 moves along... Figure 2 The photosensitive drum 1 is driven to rotate clockwise, and the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. The exposure device 3 exposes the surface of the photosensitive drum 1 by irradiating it with a laser L based on image information received from an external device. As a result, an electrostatic latent image is written (formed) on the surface of the photosensitive drum 1.

[0055] In this embodiment, a reverse development type is used. Therefore, the charging roller 2 charges the surface of the photosensitive drum 1 to a negative dark potential Vd by being supplied with a voltage (charging voltage) of the same negative polarity as the normal polarity of the toner T. After charging, the bright potential Vl of the area (image area) exposed by the exposure device 3 on the surface of the photosensitive drum is lower than the dark potential Vd. In the construction example of this embodiment, Vd = -700 (V) and Vl = -100 (V) are set.

[0056] In the developing apparatus 4, the toner T contained in the toner container 45 is homogenized by the stirring member 43 and supplied to the developing roller 41 by the supply roller 42. The toner T carried on the developing roller 41 is not only tribocharged to normal polarity through friction with the developing doctor blade 44, but is also controlled to a predetermined layer thickness during its passage through the developing doctor blade 44. By rotating the developing roller 41, the toner T with normal polarity is supplied to the developing section P4. Then, a voltage (developing voltage V) with the same normal polarity as the toner T is applied to the developing roller 41, thereby transferring the toner T onto the photosensitive drum 1 according to the potential distribution on the surface of the photosensitive drum 1. As a result, the electrostatic latent image on the surface of the photosensitive drum 1 is developed and visualized as a toner image. The toner image formed on the surface of the photosensitive drum 1 is fed to the transfer section P5 while the toner image is carried on the photosensitive drum 1.

[0057] In parallel with the above process, sheet S is fed one sheet at a time from cartridge 6 via a feed unit (not shown), and then sheet S is conveyed to transfer section P5 via feed (transfer) rollers 8. A voltage (transfer voltage) with a positive polarity opposite to the normal polarity of toner T is applied to transfer roller 5, so that the toner image is transferred from photosensitive drum 1 to sheet S at transfer section P5.

[0058] The sheet S, passing through the transfer unit P5, is conveyed to the fixing device 9. In the fixing device 9, while the sheet S is clamped and conveyed at the clamping part between the first rotatable member and the second rotatable member, the image on the sheet S is heated and fixed by the first rotatable member, which is heated by a heating device. The sheet S, passing through the fixing device 9, is discharged to the outside of the imaging apparatus 100 by the discharge roller pair 12.

[0059] (Brush type without cleaner)

[0060] Next, the operation specific to the cleanerless brush type using brush member 11 will be described. In this embodiment, a simultaneous development and cleaning type is employed, wherein residual toner that was not transferred to the toner image receiving member (sheet S) at the transfer section P5 is collected by the developing roller 41 when the residual toner next arrives at the developing section P4. In the simultaneous development and cleaning type, the residual toner collected by the developing roller 41 is stirred together with other toner in the toner container 45 and then reused for development.

[0061] In the simultaneous development and cleaning type, residual toner that was not transferred to the toner image receiving member at the transfer section P5 is collected by the developing roller 41, so the brush member 11 essentially allows residual toner to pass through it. Therefore, the "brush member" in this embodiment is different from the brush member used as a cleaning device (drum cleaner) for removing residual toner from the photosensitive drum 1. Incidentally, in the simultaneous development and cleaning type, no cleaning device is arranged for collecting residual toner, so this type is sometimes referred to as the brush type without a cleaner.

[0062] In brush types without a cleaner, and in the simultaneous developing and cleaning type, the brush member 11, used to disperse residual toner deposited on the surface of the photosensitive drum 1 passing through the transfer section P5, is arranged downstream of the transfer section P5 and upstream of the charging section P2 relative to the rotation direction R1. By arranging the brush member 11, the condition of a large amount of residual toner locally present on the photosensitive drum 1 can be alleviated. When a large amount of residual toner is locally present on the photosensitive drum 1, there is a possibility of poor charging due to residual toner contaminating the charging roller 2 and poor collection of residual toner in the developing section P4, which may cause image defects. On the other hand, in the brush type without a cleaner, the residual toner is dispersed by the brush member 11, and the behavior of the residual toner at the charging section P2 and the developing section P4 is homogenized, thereby suppressing the above-mentioned inconveniences.

[0063] (Operation unique to brush types without cleaners)

[0064] In brush-type systems without a cleaner, residual toner reaches the charging section P2 through the contact area between the brush member 11 and the photosensitive drum 1. A charging voltage of the same polarity as the normal polarity of the toner is applied to the charging roller 2, so toner particles with the normal polarity are pressed against the photosensitive drum 1 and pass through the charging section 2. On the other hand, toner particles with the abnormal polarity or those with a charge close to zero are partially deposited on the charging roller 2 at the charging section P2. When residual toner is deposited and accumulates on the charging roller 2, it prevents uniform charging of the photosensitive drum 1, making image defects caused by poor charging more noticeable.

[0065] In this embodiment, to reduce the deposition of residual toner on the charging roller 2, a circumferential speed difference is set between the charging roller 2 and the photosensitive drum 1. Specifically, the circumferential speed of the charging roller 2 is set to be at least 5% higher than the circumferential speed of the photosensitive drum 1. Furthermore, to charge the residual toner to the normal polarity through friction between the charging roller 2 and the photosensitive drum 1, the materials of the surface layers of the charging roller 2 and the photosensitive drum 1 are selected. That is, in the charging sequence, the materials of the surface layers of the charging roller 2 and the photosensitive drum 1 are at a higher level than the toner (positive polarity side, abnormal polarity side). By configuring the circumferential speed difference and materials as described above, at the charging section P2, the residual toner is charged to the normal polarity through friction with the charging roller 2 or the photosensitive drum 1, thereby suppressing the deposition of residual toner on the charging roller 2.

[0066] The residual toner from the charging section P2 reaches the developing section P4 as the photosensitive drum 1 rotates.

[0067] In the non-image area (non-exposure area), residual toner particles carried on the photosensitive drum 1, toner particles with normal polarity are transferred to the developing roller 41 and collected in the toner container 45 due to the potential difference between the dark area potential Vd and the developing voltage. On the other hand, in the image area (exposure area), residual toner particles carried on the photosensitive drum 1, toner particles with normal polarity are not transferred to the developing roller 41 due to the potential difference between the bright area potential Vl and the developing voltage, but remain on the photosensitive drum 1. In this case, the toner particles are sent to the transfer unit P5 as part of the toner image obtained by developing an electrostatic latent image. Incidentally, the developing voltage has the same polarity as the normal polarity of the toner, and is higher than the bright area potential Vl and lower than the dark area potential Vd.

[0068] Ideally, in residual toner particles, the polarity of toner particles with abnormal polarity and those with near-zero charge is changed to normal polarity, thus being collected by the developing roller 41 at the developing section P4 and not deposited on the charging roller 2. However, when a large amount of residual toner with abnormal polarity enters the charging section P2, residual toner whose polarity has not changed to normal polarity at the charging section P2 is prone to depositing on the charging roller 2. Furthermore, when residual toner whose polarity has not changed to normal polarity at the charging section P2 reaches the developing section P4, the residual toner passes through the developing section P4 without being collected by the developing roller 41. In this case, there is a possibility that the transfer roller 5 will be contaminated with residual toner and image defects such as pale toner images (white background haze) will form on the white background area (non-image area).

[0069] The components of the imaging device 100 will now be described in detail.

[0070] (Brush components)

[0071] First, the brush component 11 in this embodiment will be described. For example... Figure 2 As shown, relative to the rotation direction R1 of the photosensitive drum 1, the brush member 11 contacts the surface of the photosensitive drum 1 at a position downstream of the transfer section P5 and upstream of the charging section P2. That is, the imaging apparatus 100 includes a brush member 11 arranged downstream of the transfer section and upstream of the developing section relative to the rotation direction of the image carrying member, and in contact with the surface of the image carrying member. In the following text, the area where the brush member 11 contacts the photosensitive drum 1 is referred to as the "brush contact area".

[0072] Figure 3 Part (a) is a front view of the brush member 11 in its standalone state (viewed from the side about the short side). The standalone state is the state in which the brush member 11 is not installed in the imaging device 100, that is, the state in which no external force is acting on the brush member 11. Figure 3 Part (b) is a cross-sectional view of the brush member 11 in its single-unit state, cut along a plane perpendicular to the longitudinal direction of the brush member 11. Figure 3 Part (c) is a cross-sectional view of the brush member 11 in the state of contact with the photosensitive drum 1.

[0073] like Figure 3 As shown in parts (a) to (c), the brush member 11 includes a base fabric 11b as a base and conductive filaments (wires) 11a as bristle material (fibers) supported by the base fabric 11b. The base fabric 11b is formed of synthetic resin fibers containing carbon black as a conductive agent. The conductive filaments 11a are formed of, for example, nylon fibers with added conductive agents, and are woven and flocked onto the base fabric 11b. The material of the conductive filaments 11a is not limited to nylon, but other synthetic resin fibers such as rayon can be used.

[0074] The brush member 11 is a member that extends slenderly in a predetermined direction. In the following text, the direction of extension is referred to as the longitudinal direction LD of the brush member 11, and the direction along the base fabric 11b and perpendicular to the longitudinal direction LD is referred to as the short side direction SD of the brush member 11. Under the condition that no external force is acting on the brush member 11 ( Figure 3 Part (b) has a conductive wire 11a protruding in a direction substantially perpendicular to the longitudinal direction LD and the short side direction SD (the normal direction of the base fabric 11b).

[0075] like Figure 3 As shown in part (c), the brush member 11 is arranged in a posture in which the longitudinal direction LD is substantially parallel to the rotation axis of the photosensitive drum 1.

[0076] like Figure 3As shown in part (b), the distance from the base fabric 11c in the single-unit brush member 11 to the free end of the conductive filament 11a is the bristle height L1. In this embodiment, the bristle height L1 of the brush member 11 is 5.75 mm. The brush member 11 is supported by a support member 11c installed at a predetermined position in the imaging device 100, and the base fabric 11b is fixed to the support member by a fixing device such as double-sided tape. The position of the support member 11c is set such that the free end of the conductive filament 11a enters the photosensitive drum 1. For this purpose, the brush member 11 is in a state in which the free end of the conductive filament 11a is pressed against the surface of the photosensitive drum 1 and flexed (bent).

[0077] In this embodiment, the fixed surface of the base fabric 11c to the support member 11c is arranged substantially parallel to the surface of the photosensitive drum 1, such that the distance (gap) between the support member 11c and the photosensitive drum 1 is substantially constant. That is, when viewed along the longitudinal direction LD, a straight line from the rotation axis of the photosensitive drum 1 through the center position of the base fabric 11b relative to the short side direction SD is perpendicular to the fixed surface of the support member 11c.

[0078] Furthermore, in this embodiment, the minimum distance from the base fabric 11b of the brush member 11, which is fixed to the support member 11c, to the photosensitive drum 1 is taken as L2. In this embodiment, the difference between L2 and L1 is defined as the maximum intrusion amount of the brush member 11 into the photosensitive drum 1. However, L2 < L1 holds true.

[0079] In this embodiment, the maximum intrusion of the brush member 11 into the photosensitive drum 1 is, for example, 1.2 mm. Additionally, in this embodiment, as... Figure 3 As shown in part (b), for the brush member 11 in its single-unit state, the length of the brush member 11 relative to the short side direction SD (which is the short side (side) width L3) is, for example, 4 mm. Figure 3 As shown in part (c), with the brush member 11 pressed against the photosensitive drum 1, the width occupied by the conductive filament 11a relative to the short side direction SD is about 5 mm to about 6 mm.

[0080] Furthermore, in this embodiment, the length L4 of the brush member 11 relative to the longitudinal direction LD is 216 mm. The length L4 is set such that, relative to the longitudinal direction LD, the brush member 11 can contact the entire area of ​​the imaging region (the toner image formation area, the largest area of ​​the latent image formed by the exposure device 3) on the photosensitive drum 1. Furthermore, in this embodiment, the thickness of the conductive filament 11a is, for example, 2 denier, and the density of the conductive filament 11a is, for example, 240 kF / inch. 2The thickness and density of the conductive wire 11a can be appropriately varied, as long as the conductive wire 11a meets the functional requirements of the brush member 11. As an example, it is preferred that the thickness of the conductive wire 11a is 1 denier or more and 6 denier or less, and the density of the conductive wire 11a is 150 kF / inch. 2 Above and 350kF / inch 2 Below. Incidentally, 1kF / inch 2 This indicates a flocking density of 1000 fibers per square inch.

[0081] Incidentally, in the case of the nylon conductive yarn 11a used in this embodiment, when converting 1 to 6 denier (which is a unit of direct yarn count) to fiber diameter, 1 to 6 denier corresponds to approximately 10 μm to approximately 30 μm. Therefore, when using a bristle material other than nylon as the brush component, bristle materials with a thickness of 1 denier or more and 6 denier or less in terms of direct yarn count and a fiber diameter of 10 μm or more and 30 μm or less can be used.

[0082] "1 denier or higher and 6 denier or lower" can be described as "1.1 decitex or higher and 6.7 decitex or lower". Additionally, 1 inch 2 Approximately 6.45cm 2 Therefore, "150kF / inch" 2 Above and 350kF / inch 2 The following can be referred to as "23kF / mm". 2 Above and 54kF / mm 2 the following".

[0083] In this embodiment, the brush member 11 is configured to allow residual toner to pass through while dispersing the residual toner deposited on the surface of the photosensitive drum 1 that has passed through the transfer section P6. Therefore, if the conductive filament 11a is too thick, there is a possibility that the residual toner cannot be evenly dispersed and passes through the brush contact in a striped pattern, thus causing the residual toner to contaminate the charging roller 2 in a striped pattern. Furthermore, if the density of the conductive filament 11a is too high, the residual toner is blocked by the brush contact, thus not only creating an obstacle for the developing roller 41 to collect the residual toner, but also contaminating the interior of the imaging device due to the residual toner falling or scattering from the photosensitive drum 1. Furthermore, the brush member 11 is configured to tribocharge the residual toner at the brush contact. Therefore, if the conductive filament 11a is too thin, there is a possibility that even when the residual toner contacts the conductive filament 11a, the conductive filament 11a easily bends and bypasses the residual toner, thus preventing the toner particles from rolling and the residual toner from being sufficiently tribocharged. Furthermore, if the density of the conductive wire 11a is too low, the frequency of collisions with the conductive wire 11a will decrease, which may result in the residual toner not being able to be sufficiently charged through friction.

[0084] In the above description, the preferred range of thickness and density of the conductive wire 11a was described from the perspective of its function in dispersing residual toner and in causing residual toner to become triboelectrically charged. However, details such as thickness, density, material, and bristle height can be appropriately changed depending on the required function of the brush member 11. Incidentally, the brush member 11 in this embodiment may have the function of blocking foreign matter (e.g., paper dust) other than residual toner at the brush contact portion.

[0085] (Developer)

[0086] In this embodiment, toner T, a single-component developer, is used as the developer, and its normal polarity is negative. Therefore, in the following description of this embodiment, unless otherwise specified, "negative polarity" is synonymous with the normal polarity of toner T, and "positive polarity" is synonymous with the abnormal polarity of toner T.

[0087] The colorant T contains a binder resin and a colorant, and may also contain a release agent, a charge control agent, and external additives as needed. As the binder resin, styrene-acrylic resin and polyester resin are preferred, as their charge sequence positions (negative polarity side) are lower than those of nylon and rayon. That is, the main component of the colorant T (binder resin) can ideally be located on the positive polarity side (lower position) in the charge sequence relative to the fibrous material (bristle material) of the brush member 11. In this embodiment, styrene-acrylic resin is used as the binder resin for the colorant.

[0088] As a colorant, known colorants can be used. Examples include dyes and pigments. As a release agent, known charge control agents can be used. The charge control agent has an acid value or hydroxyl value, and preferably has a negative polarity equal to or greater than that of the binder resin. As an external additive, known external additives can be used. Examples include silica, alumina, titanium dioxide, titanium composite oxides, etc. The colorant and release agent can preferably be included in the binder resin so as not to affect the charge polarity of the colorant particle surface.

[0089] Furthermore, as a toner, a polymeric toner formed by a polymerization method can be used. A toner T with a particle size (volume average particle size) of 4 μm to 10 μm, preferably 6 μm to 8 μm, is preferred. In this embodiment, a spherical toner with a particle size of 7 μm prepared by a polymerization method is used. Furthermore, the toner T in this embodiment is a so-called non-magnetic single-component developer, which does not contain magnetic components and is mainly supported on the developing roller 41 by intermolecular forces or electrostatic forces (mirror forces). However, as a developer, a single-component developer composed of a toner containing magnetic components can be used. Furthermore, as a developer, a two-component developer composed of a non-magnetic toner and a magnetic carrier can be used. In the case of using a magnetic developer, a cylindrical developing sleeve in which a magnet is disposed is used, for example, as the developer carrier. In addition to the toner and carrier, additives (e.g., wax or fine silica particles) for adjusting the toner's flowability, charge properties, etc., can be added to the developer.

[0090] (Photosensitive drum)

[0091] The photosensitive drum 1 is prepared by sequentially layering a base coating, a charge generation layer, and a charge transport layer onto a cylindrical conductive support member (core metal) as the bottom layer. The charge transport layer is formed by coating and drying a paint prepared primarily by mixing a charge transport material and a binder resin in a solvent. Known charge transport materials can be used as the main charge transport material. Examples include various triarylamine compounds and hydrazone compounds. Furthermore, examples of binder resins include, for instance, polycarbonate resins and polyarylate resins.

[0092] The main component that becomes triboelectrically charged with the toner is the charge-transporting layer, which is the surface layer (outermost layer), and is primarily composed of the binder resin. Here, the polycarbonate resin or polyarylate resin is located on the non-normal polarity side (superior) relative to the styrene-acrylic resin (which is the binder resin for toner T) in the charge sequence. That is, the outermost layer of the image carrier member, when rubbed against the resin, which is the main component of toner T, can preferably be formed of a material capable of triboelectrically charging the toner T to its normal polarity. In this embodiment, polycarbonate resin is selected as the binder resin for the outermost layer.

[0093] Furthermore, in this embodiment, a cylindrical photosensitive drum with an outer diameter of 24 mm is used as the photosensitive drum 1. The contact (pressing) method of the brush member 11 is appropriately changed according to the outer diameter of the photosensitive drum 1 (for example, the amount of penetration described above or the angle described later in the third embodiment).

[0094] (Charging roller)

[0095] The charging roller 2 in this embodiment will be described. The charging roller 2 includes a core metal as a conductive support member, a 2 mm thick elastic layer disposed on the outer periphery of the core metal, and a 25 mm thick resin layer disposed on the outer periphery of the elastic layer as a surface layer. The surface of the surface layer is the surface that contacts the photosensitive drum 1 and causes discharge on the photosensitive drum 1.

[0096] The elastic layer is formed of an electronically conductive rubber material. This electronically conductive rubber material is, for example, a material in which carbon black, as conductive particles (electronically conductive agent), is dispersed in a binder polymer that is not conductive in itself, and where the resistance is adjusted. As the binder polymer, known binder polymers used in the conductive elastic layer of the charging roller for an electrophotographic device can be used. Examples include alcohol rubber and butadiene rubber. In this embodiment, alcohol rubber is selected.

[0097] The type of carbon black mixed in the elastic layer is not particularly limited, as long as the carbon black is conductive and can impart conductivity to the elastic layer. Furthermore, as needed, general-purpose agents such as fillers, processing aids, crosslinking aids, crosslinking inhibitors, softeners, dispersants, and colorants can be added to the elastic layer as compounding agents.

[0098] The resin used as the surface layer is a resin material that is located on the non-normal polarity side (superior position) in the charging sequence relative to the main component (binder resin) of the toner T. For example, the surface layer is formed by coating the outer periphery of the elastic layer with a conductive resin material (e.g., polycarbonate polyurethane). By forming the third layer of the photosensitive drum 1 and the third layer of the charging roller 2 with the above-described material, and by setting the circumferential speed difference between the charging roller 2 and the photosensitive drum 1 as described above, the residual toner can be tribocharged to the normal polarity at the charging section P2.

[0099] Furthermore, roughening particles with a certain polarity can be added to the surface layer of the charging roller 2 so as not to impair triboelectricity. For example, there are also methods that prepare polycarbonate polyurethane resin similar to the polycarbonate polyurethane resin of the surface layer into particles and disperse the particles. That is, the charging roller 2 does not need to be in close contact with the surface of the photosensitive drum 1 at the charging section P2, so a structure in which the charging roller 2 contacts the surface of the photosensitive drum 1 at the uneven peaks formed by the roughening particles can be adopted.

[0100] (Transfer roller)

[0101] The transfer roller 5 is a roller-type transfer component arranged opposite to the photosensitive drum 1. The transfer roller 5 presses against the photosensitive drum 1 with a predetermined pressure. In this embodiment, the transfer roller 5 is an elastic roller with an outer diameter of 12 mm, wherein a conductive nitrile rubber-alcohol rubber type sponge rubber is formed around the core metal.

[0102] (Contact conditions for brush components)

[0103] In this embodiment, the brush member 11 imparts charge to the residual toner through triboelectric charging, while simultaneously distributing the residual toner onto the photosensitive drum 1. To impart a negative charge to the residual toner through triboelectric charging, the material used for the brush bristles (conductive filament 11a) of the brush member 11 is a material that is located on the positive polarity side (superior position) relative to the main component of the toner T in the charging sequence. Furthermore, the contact pressure between the brush member 11 and the photosensitive drum 1 at the brush contact portion is ensured so that the conductive filament 11a rubs the residual toner with sufficient force.

[0104] Regarding the charge sequence, in this embodiment, the main component of the toner T is styrene-acrylic resin. The bristle material of the brush member 11 can ideally be a material such as nylon or rayon, with styrene-acrylic resin positioned on the negative polarity side (lower position) relative to this material, and the charge sequence difference between them is relatively large. In this embodiment, as described above, nylon resin is selected as the main component of the conductive filament 11a. Polyester and acrylic fibers are not ideal materials for the conductive filament 11a because styrene-acrylic resin is positioned on the positive polarity side relative to polyester and acrylic fibers in the charge sequence, and the charge sequence difference is also small. However, in cases where the main component of the toner T is different, polyester or acrylic fibers can be used as the material for the conductive filament 11a in some situations.

[0105] Incidentally, the surface layer of the photosensitive drum 1 can influence the triboelectric charging of the toner T at the brush contact portion. Therefore, the main component of the surface layer of the photosensitive drum 1 can preferably be a material located on the positive polarity side relative to the main component of the toner T in the charging sequence. In this embodiment, as described above, the main component of the surface layer of the photosensitive drum 1 is polycarbonate resin.

[0106] The contact conditions of the brush member 11 at the brush contact portion will be further described. To investigate the physical properties (parameters) representing the contact conditions of the brush member 11, four samples 1 to 4 with different bristle material coarseness and density were prepared. Sample 1 is a brush member 11 with coarse bristle material and low density. Sample 2 is a brush member 11 with fine bristle material and medium density. Sample 3 is a brush member 11 with fine bristle material and high density. Sample 4 is a brush member 11 with medium bristle material coarseness and low density. Then, the brush member 11 of each sample was brought into contact with the photosensitive drum 1, and the peak pressure and maximum contact area ratio at the brush contact portion were calculated as follows. Incidentally, the peak pressure is the maximum value of the average contact pressure in a region with a width of 1 mm relative to the short side direction of the brush contact portion, and the maximum contact area ratio is the contact area ratio between the brush member 11 and the photosensitive drum 1 in the region with a width of 1 mm where the peak pressure is obtained.

[0107] The peak pressure is calculated as follows. For example... Figure 4 As shown, using a compression test fixture on a small benchtop testing machine (Shimadzu Corporation's "EZtest"), the vertical resistance was measured when a pressing plate was pressed into the brush member 11 while adjusting the flow of the bristles (fibers) of the horizontally placed brush member 11. The relationship between the intrusion amount and the vertical resistance was then obtained. On the other hand, as... Figure 5 As shown, the glass plate is pressed against the brush member 11 in a manner that makes the flow of the brush bristles consistent while the glass plate is moved in the horizontal direction, and the contact width of the brush member 11 relative to the short side direction SD is measured by observation with a microscope.

[0108] When the brush member 11 is prepared to have uniform density and fineness of its bristle material, the peak pressure can be calculated using the following formulas (1) to (3). First, with the object pressing against the brush member 11 with a predetermined amount of penetration, the average value of the contact pressure at the brush contact portion (average pressure) can be represented by formula (1). In formula (1), the vertical resistance and contact width are defined by the pressing plate ( Figure 4 ) or glass plate ( Figure 5 The value measured under the condition of pressing the brush member 11 with a predetermined amount of intrusion.

[0109] (Formula 1) (Average Pressure) = (Vertical Resistance) / ((Contact Width) × (Longitudinal Width)) (gf / mm) 2 )

[0110] At the actual brush contact portion between the brush member 11 and the photosensitive drum 1, the contact pressure becomes maximum in the portion where the brush member 11 penetrates the photosensitive drum 1 to the greatest extent. This maximum contact pressure is called the peak pressure. The peak pressure is calculated using the average penetration amount (Formula 2) obtained from the maximum and minimum penetration amounts of the brush member 11 via Formula 3.

[0111] (Formula 2) (Average Invasion Amount) = ((Maximum Invasion Amount) + (Minimum Invasion Amount)) / 2 (mm)

[0112] (Formula 3) (Peak pressure) = (Average pressure) × (Maximum intrusion volume) / (Average intrusion volume) (gf / mm) 2 )

[0113] The above calculation method actually means applying to, for example Figure 6 The contact pressure on the surface of the photosensitive drum 1, drawn as an arc, is linearly approximated. Specifically, assuming a brush member 11 with a short side (side) width L3 of 4 mm contacts the photosensitive drum 1 with a diameter of 24 mm directly above it, the intrusion amount at the center of the photosensitive drum 1 in the direction relative to the short side SD becomes 1.2 mm. In this case, the maximum intrusion amount is 1.2 mm, the minimum intrusion amount is 1.03 mm, and the average intrusion amount is 1.115 mm, so the peak pressure can be calculated using (Equation 3).

[0114] Through such Figure 5 The contact area ratio is determined by the color tone between the portion of the brush member 11 that contacts the glass plate (contact portion) and the portion of the brush member 11 that does not contact the glass plate (non-contact portion) when the brush member 11 contacts the glass plate. Figure 7 Part (a) is an actual photograph observed through a microscope. Figure 7 Part (b) is by making Figure 7 The image in part (a) is binarized to make the contact area white and the non-contact area black. The contact area ratio is the ratio of the area of ​​the contact area to the area of ​​the observed object (i.e., the ratio obtained by dividing the number of white pixels by the total number of pixels). The maximum contact area ratio is obtained at the location where the peak pressure is obtained, that is, at the center of the SD direction relative to the short side.

[0115] In summary, regarding the imaging device including the brush member 11 as in this embodiment, the peak pressure and maximum contact area ratio can be determined in the following process.

[0116] 1) Measure the outer diameter of the photosensitive drum 1, the bristle height L1 and short side width L3 of the brush member 11, and the shortest distance L2 from the base fabric 11b of the brush member 11 to the surface of the photosensitive drum 1, and calculate the maximum intrusion amount (L1-L2) (see...). Figure 3Parts (b) and (c)).

[0117] 2) Based on the outer diameter of the photosensitive drum 1, the short side width L3 of the brush member 11, and the maximum intrusion amount measured in 1) above, based on Figure 6 The minimum intrusion amount is calculated based on the geometric relationship.

[0118] 3) Based on the maximum and minimum intrusion amounts obtained through 1) and 2) above, calculate the average intrusion amount based on (Formula 2).

[0119] 4) Using the average intrusion amount calculated in 3) above through Figure 4 and 5 The compression test of the brush component 11 is performed by the method, thereby obtaining the average pressure based on (Formula 1).

[0120] 5) Calculate the peak pressure based on (Formula 3) by using the maximum intrusion amount, average intrusion amount and average pressure obtained from 1), 3) and 4) above.

[0121] 6) Of the maximum intrusion amount obtained in 1) above, through Figure 5 The method involves pressing the brush component 11 against the glass plate, then observing the contact surface to calculate the maximum contact area ratio.

[0122] Furthermore, in order to make the peak pressure and maximum contact area ratio of the brush component 11 the desired value, parameters such as the outer diameter of the photosensitive drum 1, the bristle height L1 and the short side width L3 of the brush component 11, and the aforementioned shortest distance L2 are appropriately changed, so that the peak pressure and maximum contact area ratio can be checked only during the above process.

[0123] Figure 1 The graph shows the following: In the above method, peak pressure and maximum contact area ratio are calculated for each sample under multiple different conditions, and the peak pressure value is plotted on the vertical axis and the maximum contact area ratio value is plotted on the horizontal axis. Figure 1 In the diagram, black marks indicate points where no image defects are present, while white marks indicate points where image defects are present.

[0124] like Figure 1 As shown, when the peak pressure is less than 0.7 gf / mm 2Furthermore, image defects occurred when the maximum contact area ratio was less than 18%. This is believed to be because, under excessively low peak pressure, the contact between the brush bristle material of brush member 11 and the toner particles weakens, resulting in insufficient action to tribocharge the residual toner to the normal polarity. Additionally, this is also believed to be because, under excessively low maximum contact area ratio, the contact frequency between the toner particles and the brush bristle material of brush member 11 decreases in the region where tribocharging is most easily achieved and where peak pressure is applied, further reducing the effectiveness of tribocharging the residual toner to the normal polarity. In either case, when the residual toner reaches the charging section P2 without being adequately charged with a positive polarity at the brush contact section, residual toner with an abnormal polarity or a charge close to zero deposits on the charging roller 2, resulting in contamination of the charging roller 2.

[0125] Furthermore, at peak pressures above 3.5 gf / mm 2 Image defects occur when the peak pressure or maximum contact area ratio is higher than 74%. This is believed to be because, under either excessively high peak pressure or excessively high maximum contact area ratio, a portion of the brush contact is in a state where residual toner cannot pass through that portion of the brush contact, thus the residual toner concentrates on the portion that can pass through (where the contact pressure or density of the brush bristle material is relatively low). In this case, the surface of the photosensitive drum 1 through which the brush contact passes is in a state where residual toner is deposited in a stripe shape (a linear shape extending in the rotational direction), causing the charging roller 2 to be contaminated with residual toner in a stripe shape. Incidentally, in areas where the peak pressure or maximum contact area ratio is particularly high, residual toner is blocked by the brush member 11, thus creating the possibility that not only is the collection of residual toner by the developing roller 41 hindered, but the blocked toner also scatters and contaminates the interior of the imaging device with the scattered toner.

[0126] Therefore, it is desirable that the brush component 11 be configured such that the ratio of peak pressure to maximum contact area at the brush contact portion falls within the range determined by... Figure 1 The area enclosed by the dashed line below.

[0127] (Peak pressure): 0.7 gf / mm 2 Above and 3.5gf / mm 2 the following

[0128] (Maximum contact area ratio): 18% or more and 74% or less

[0129] Therefore, in a cleanerless brush type where residual toner deposited on the surface of the photosensitive drum 1 after passing through the transfer section P5 is dispersed by the brush member 11, the charge distribution of the residual toner can be stabilized at the normal polarity. In other words, the charge distribution of the residual toner after passing through the brush contact section can be made to have a peak on the normal polarity side (negative polarity side) of the toner T and be sharper than the charge distribution of the residual toner before entering the brush contact section.

[0130] Incidentally, in the area enclosed by the dotted line, the aforementioned image defects are less likely to occur at the center compared to the periphery. Therefore, it is preferable that the brush member 11 is configured such that the peak pressure and / or maximum contact area ratio further fall within the following ranges.

[0131] (Peak pressure): 1.4 gf / mm 2 Above and 2.8gf / mm 2 the following

[0132] (Maximum contact area ratio): 32% or more and 60% or less

[0133] Here, 1 gf is approximately equal to 9.8 × mN (milline Newtons), therefore "0.7 gf / mm 2 Above and 3.5gf / mm 2 The following can be referred to as "6.9 mN / mm". 2 Above and 34mN / mm 2 "The following." Similarly, "1.4gf / mm" 2 Above and 2.8gf / mm 2 The following can be referred to as "14mN / mm". 2 Above and 28mN / mm 2 the following".

[0134] Furthermore, in this embodiment, the Clark-Evans index is introduced as an index to indicate whether the brush member 11 contacts the photosensitive drum 1 uniformly. The Clark-Evans index indicates whether, when multiple points are distributed in a certain flat surface area, these points are either locally concentrated or distributed at intervals.

[0135] The calculation method of the Clark-Evans index will be described. First, when the distance from point i to its nearest neighbor is d_i and the number of points is n, the average distance from each point to its nearest neighbor (average nearest neighbor distance) W is represented by the following formula (Mathematical Formula 1).

[0136] (Mathematical Formula 1)

[0137]

[0138] Here, as an evaluation criterion, we will consider the case where points are randomly distributed on a flat surface of area S (according to a uniform Poisson distribution). In this case, the expected value E(W) of the average nearest neighbor distance W is expressed by the following equation (Mathematical Equation 2).

[0139] (Mathematical Formula 2)

[0140]

[0141] To compare cases where the number of points and density are different from each other, the value w obtained by standardizing the average nearest neighbor distance W with the expected value E(W), as expressed in the following formula (Mathematical Formula 3), is called the Clark-Evans index.

[0142] (Mathematical Formula 3)

[0143]

[0144] To obtain the Clark-Evans index for brush component 11, such as Figure 5 As shown, the brush member 11 is pressed against the surface of a glass plate, and the brush contact portion is observed through the glass plate surface from the side opposite to the side where the brush member 11 is pressed against the glass plate surface. In the brush contact portion, when a specific area (100mm)... 2 When the free ends of the bristle material in the diagram are represented by points, the following is obtained: Figure 7 The distribution of points is shown in part (c). Based on this distribution, the Clark-Evans index is calculated using the formulas (Mathematical Expressions 1 to 3) described above.

[0145] Incidentally, a portion of the bristle material even contacts the glass (plate) surface at a location closer to the base than the free end. The effect of the toner T being triboelectrically charged through this bristle material is considered to be largely due to the contribution of the portion of the bristle material in strongest contact with the glass surface (the strongest indentation point). However, the distribution of the strongest indentation points of the bristle material is generally the same as the distribution of the free ends of the bristle material, and the properties of the distribution remain essentially unchanged. Therefore, in this embodiment, the Clark-Evans index is calculated based on the distribution of the free ends of each bristle material contacting the glass surface.

[0146] Regarding the Clark-Evans index, it holds true for a random distribution where w = 1, for a concentrated distribution where w < 1, and for a regular distribution where w > 1. An extreme example of a regular distribution is a lattice-like distribution that covers the entire area of ​​the observed object. An extreme example of a concentrated distribution is a distribution where points are concentrated in a single part or several parts of the observed object's area.

[0147] The Clark-Evans index of the actual sample of brush component 11 is obtained as follows.

[0148] Sample 1: w = 1.01

[0149] Sample 2: w = 1.13

[0150] Sample 3: w = 1.15

[0151] Sample 4: w = 1.07

[0152] The sample obtained by intentionally twisting sample 2 into a bundle: w = 0.7

[0153] According to the properties of the Clark-Evans index, when w > 1, it can be said that the free ends of the bristle material of brush component 11 are loose and not bundled. On the other hand, when w < 1, it means that the bristle material of brush component 11 is bundled (aggregated, clumped) for some reason.

[0154] For the brush component to function properly, the bristles of the brush component 11 need to contact the surface of the photosensitive drum 1 in a loose and non-bundled state. In this embodiment, the brush component 11 is configured such that the Clark-Evans index is 1 or greater (w≥1). This state can be described as ensuring that the bristle material does not clump together for any reason.

[0155] Incidentally, based on the construction of the brush member 11, it is also possible to consider that even at the brush contact portion, the value of the Clark-Evans index varies depending on the location. In this case, the Clark-Evans index is greater than 1 at the portion of the brush member 11 where the penetration amount is the largest (the location where the contact pressure is the peak pressure). This is because at the portion with the largest penetration amount, it is easier to form a bristle bundle through the force received by the bristle material.

[0156] (Qualitative description of the phenomenon)

[0157] This will describe how the phenomenon changes based on the calculated peak pressure and the calculated maximum contact area ratio. Figure 8 and Figure 9 A schematic diagram is shown when the peak pressure or maximum contact area ratio is insufficient (refer to Example 1). Figure 8 This is a schematic diagram showing the main components of the imaging unit 101. Figure 9 yes Figure 8 A magnified view of a portion of the image, in which the charge of the toner is represented by three types: positive (+), negative (-), and weak charge (0).

[0158] like Figure 9As shown, toner particles with a wide charge distribution enter the brush member 11 as residual toner. In this example, the peak pressure or maximum contact area ratio of the brush member 11 is insufficient, resulting in low triboelectricity. Therefore, the residual toner passes through the brush contact while maintaining a wide charge distribution. Subsequently, when the residual toner reaches the charging section P2, as described above, in particular, the positively charged toner suffers poor charging due to its deposition on the charging roller 2, and in some cases, white background fogging occurs due to a failure of the developing roller 41 to collect the toner. Furthermore, when the amount of weakly charged toner is large, in some cases the toner cannot be sufficiently given a negative charge at the charging section P2, and in this case, the weakly charged toner is not easily collected by the developing roller 41.

[0159] Next, the phenomenon of excessively high peak pressure or maximum contact area ratio (see Example 2) will be described.

[0160] Figure 10 Part (a) is a schematic diagram of the model experiment, in which... Figure 5 In the process, a glass plate serving as a model is forcefully pressed against the brush member 11 (maximum intrusion: 3 mm) and then toner is supplied. As the glass plate moves, toner is supplied, thereby observing the state of toner T flow.

[0161] When the peak pressure or maximum contact area ratio is high, the brush component 11 presses forcefully against the photosensitive drum 1. In such cases... Figure 10 In part (a), at position X, at a portion of the brush contact area where the brush bristle material (conductive filament 11a) is bundled (aggregated), the brush member 11 presses more forcefully against the photosensitive drum 1, thereby strongly restricting the passage of toner T. On the other hand, at position Y, the conductive filaments do not form a bundle, and the flow of toner T is concentrated, causing a large amount of toner T to pass through this position.

[0162] exist Figure 10 At point x in part (b), on the surface of the photosensitive drum 1 passing through the brush contact portion, a deposition on the surface is schematically shown. Figure 10 The amount and charge of the toner on the portion corresponding to the position indicated by X in part (a). Figure 10 At point y in part (b), on the surface of the photosensitive drum 1 passing through the brush contact portion, a deposition on the surface is schematically shown. Figure 10The amount and charge of the toner on the portion corresponding to the position indicated by Y in part (a). At the position (X, x) where the toner T is difficult to pass through, the toner T passes through the position while strongly rubbing against the brush member 11, so a negative charge is assigned to most of the toner T. On the other hand, at the position (Y, y) where the toner passes through in a concentrated manner, a portion of the toner T passes through the position easily without strongly rubbing against the brush member 11, and the amount of toner increases. Therefore, the residual toner deposited in a stripe shape at the position (Y, y) where the toner passes through in a concentrated manner is deposited on the charging roller 2, making it easy for the residual toner to contaminate the example roller 2 in a stripe shape.

[0163] Figure 11 and 12 This is a schematic diagram illustrating this embodiment. Figure 11 This is a schematic diagram showing the main components of the imaging unit 101. Figure 12 yes Figure 11 A magnified image of a portion, in which... Figure 9 Similarly, the charge of the toner is represented by being divided into three types. Figure 8 and 9 In contrast, the contact conditions are set such that the brush member 11 presses forcefully against the photosensitive drum 1, without creating a state where the peak pressure and maximum contact area ratio are too high. Figure 10 ).

[0164] like Figure 12 As shown, the brush member 11 in this embodiment is configured to have an appropriate peak pressure and an appropriate maximum contact area ratio. Therefore, when residual toner passes through the brush contact portion, the residual toner with a wide charge distribution becomes tribocharged through friction with the bristle material (conductive wire 11a) of the brush member 11. Furthermore, the brush member 11 is configured such that the peak pressure and maximum contact area ratio do not become excessively high, and the Clark-Evans index satisfies w≥1, thus preventing residual toner from concentrating in a stripe shape through the brush contact portion. Therefore, it is less likely to cause contamination of the charging roller 2 by residual toner and failure to collect residual toner on the developing roller 41, thereby maintaining high image quality for a long period.

[0165] <Second Embodiment>

[0166] A second embodiment of the invention will be described. This embodiment differs from the first embodiment in that voltage is applied to the brush member 11. Hereinafter, the elements indicated by the reference numerals or symbols common to both the first and second embodiments have substantially the same construction and function as those described in the first embodiment, and the differences from the first embodiment will be primarily described.

[0167] like Figure 13As shown in the schematic diagram, in brush types without a cleaner, in some cases, toner particles are entangled and trapped near the base of the bristle material (conductive filament 11a) of the brush member 11. As new residual toner continuously reaches the brush contact portion, the toner T trapped therein is essentially pushed downstream in the direction of rotation of the photosensitive drum 1. However, compared to the toner T that rolls through the brush contact portion while rubbing against the free end of the bristle material of the brush member 11, the toner T that is pushed out after being trapped at the base of the bristle material tends to have an insufficient amount of normal polarity (negative polarity) charge.

[0168] Therefore, in this embodiment, in order to push the toner T toward the area where the bristle material of the brush member 11 contacts the surface of the photosensitive drum 1 (push toward the photosensitive drum 1 side), a voltage is applied to the brush member 11.

[0169] In this embodiment, during imaging, the surface of the photosensitive drum 1 is charged to a dark area potential Vd of -700V at the charging section P2. The image area on the photosensitive drum 1 is exposed by the exposure device 3 to a bright area potential Vl of -100V. Then, the surface of the photosensitive drum is subjected to a transfer voltage of +1000V at the transfer section P5 of the transfer roller 5, causing the dark area potential Vd to become approximately -200V and the bright area potential Vl to become approximately -50V. Therefore, the surface potential of the photosensitive drum 1 reaching the brush contact during imaging becomes approximately -20V to approximately -200V.

[0170] like Figure 14 As shown, a brush power supply E11, serving as a voltage application device, is electrically connected to the brush member 11. During imaging, a predetermined brush voltage E is applied to the brush member 11 via the brush power supply E11. The predetermined brush voltage E is a potential whose polarity relative to the surface potential of the photosensitive drum 1 reaching the brush contact portion during imaging (especially after passing through the transfer portion where the dark area potential is higher than the bright area potential) is the same as the normal polarity of the toner T. In this embodiment, a voltage of -400V is applied to the brush member 11.

[0171] In the residual toner entering the brush contact portion, the negatively charged (normal polarity) toner T is electrostatically pushed towards the photosensitive drum 1 at the brush contact portion due to the potential difference between the brush voltage E (-400V) and the surface potential (-50V to -200V) of the photosensitive drum 1. Thus, the negatively charged toner T is pressed against the photosensitive drum 1 and rolls simultaneously with the brush bristle material of the brush member 11 and the surface of the photosensitive drum 1, allowing the negatively charged toner T to be sufficiently tribocharged. As a result, the toner T is sufficiently tribocharged in the brush contact portion, stabilizing the charge distribution of the residual toner in the normal polarity. This prevents inconveniences such as residual toner contaminating the charging roller 2 and the developing roller 41 failing to collect the residual toner (poor collection).

[0172] Here, the brush voltage E is set to a value that prevents discharge between the brush member 11 and the photosensitive drum 1. This is because when unnecessary discharge is performed, the photosensitive drum 1 will be contaminated by discharge products and its degradation will be accelerated.

[0173] In this embodiment, similar to the first embodiment, the brush member 11 is arranged substantially parallel to the surface of the photosensitive drum 1. Therefore, as Figure 14 As shown, the contact pressure between the brush member 11 and the photosensitive drum 1 becomes the maximum (peak value) at the center of the brush contact portion relative to the short side direction.

[0174] Here, among the residual toner entering the brush contact portion, the toner T with a positive polarity (abnormal polarity) is easily attracted towards the base side of the bristle material during entry into the brush contact portion. The toner T attracted to the base side of the bristle material moves downstream by being pushed out by newly supplied toner T from the upstream side, and at this time, the moving toner T becomes triboelectrically charged to a negative polarity through friction with the bristle material. Therefore, during its movement through the inside of the brush member 11, the toner T, whose polarity becomes negative, is pressed against the photosensitive drum 1 by the brush voltage E, and becomes triboelectrically charged by rolling simultaneously with the bristle material of the brush member 11 and the surface of the photosensitive drum 1. However, the change of polarity of the toner T attracted to the base side of the bristle material to a negative polarity is delayed, and there is a possibility that the toner T in a state of insufficient charge passes through the brush contact portion.

[0175] Therefore, in order to quickly change the polarity of the toner attracted to the base side of the bristle material to a negative polarity, in this embodiment, it is desirable to set a lower limit for each of the peak pressure and contact area ratio of the brush member 11 at the upstream position of the brush contact portion in the rotation direction R1 relative to the photosensitive drum 1. As an example, the settings are made such that the penetration amount of the brush member 11 at the upstream position of the brush contact portion in the short side direction (rotation direction R1) relative to the brush contact portion is 1.2 mm, and the penetration amount of the brush member 11 at the center position of the brush contact portion is 1.34 mm. Thus, at the upstream position of the brush contact portion, the following relationship is satisfied.

[0176] (Contact pressure) ≥ 0.7 gf / mm 2

[0177] (Contact area ratio) ≥18%

[0178] The conditions for peak pressure, maximum contact area ratio, and Clark-Evans index are similar to those in the first embodiment.

[0179] When the contact pressure and contact area ratio at the upstream position of the brush contact are set as described above, such as Figure 15The polarity of the toner T shown can be rapidly changed to negative polarity at the upstream portion of the brush contact, thereby reducing the accumulation of toner T at the base of the bristle material in the brush contact. Then, the toner T is sufficiently tribocharged at the brush contact, allowing the charge distribution of the remaining toner to be further stabilized in the normal polarity.

[0180] Incidentally, in this embodiment, the toner T is pressed against the photosensitive drum 1 by the brush voltage E, so that even if the brush member 11 is not necessarily located on the positive polarity side (non-normal polarity side) relative to the toner T in the charging sequence, the polarity of the toner T can be changed to negative polarity at the brush contact portion. However, the configuration in which the brush member 11 is located on the positive polarity side relative to the toner T in the charging sequence is advantageous for changing the polarity of the toner T to negative polarity.

[0181] Furthermore, in this embodiment, the main function of the brush voltage E is described from the angle at which the toner T entering the brush member 11 is pressed towards the photosensitive drum 1. The invention is not limited thereto. When the brush voltage E is applied to the brush member 11, the change from polarity of the toner T to negative polarity can be accelerated by injecting (supplying) a normally polar charge into the toner T using the brush member 11. Furthermore, by applying the brush voltage E, the actions of pressing the toner T against the photosensitive drum 1 and injecting a charge into the toner T can be performed simultaneously.

[0182] <Third Embodiment>

[0183] A third embodiment of the present invention will be described. This embodiment differs from the second embodiment in that the brush member 11 is arranged at an angle relative to the photosensitive drum 1. Hereinafter, the elements indicated by the reference numerals or symbols common to the first to third embodiments have substantially the same structure and function as those described in the first or second embodiment; the parts that differ from the first or second embodiment will be mainly described.

[0184] Figure 16 and 17 This is a schematic diagram illustrating this embodiment. Figure 16 This is a view showing the main components of the imaging unit 101. Figure 17 yes Figure 16 A magnified image of a portion, in which... Figure 9 Similarly, the charge of toner T is represented by being divided into three types.

[0185] In this embodiment, the brush member 11 is arranged at an angle relative to the photosensitive drum 1, such that, relative to the rotation direction R1 of the photosensitive drum 1, the contact pressure and contact area ratio at the upstream portion of the brush contact portion become the peak pressure and the maximum contact area ratio, respectively. The tangent TL of the photosensitive drum 1 is the tangent line drawn perpendicularly from the center position of the brush member 11 in the short side direction SD (the direction along which the base fabric 11b extends when viewed in the longitudinal direction) at the intersection point 1a with the photosensitive drum. In this embodiment, the direction along which the brush member 11 is tilted is the tilting direction of the base fabric 11b of the brush member 11 downstream of the rotation direction R1, away from the tangent TL.

[0186] The angle between the short side direction D of the brush member 11 and the tangent TL is called the tilt angle. In this embodiment, the tilt angle is preferably set to 12 degrees, and the brush member 11 is arranged such that the intrusion amount (maximum intrusion amount) at the upstream end of the brush contact portion becomes 1.2 mm. Furthermore, in this embodiment, the following relationship is satisfied at the upstream position of the brush contact portion.

[0187] (Contact pressure) ≥ 0.7 gf / mm 2

[0188] (Contact area ratio) ≥18%

[0189] Incidentally, the tilt angle and invasive amount can be appropriately changed according to the outer diameter of the photosensitive drum 1, the necessary peak pressure, and the necessary contact area ratio.

[0190] The conditions for peak pressure, maximum contact area ratio, and Clark-Evans index are similar to those in the first embodiment.

[0191] In this embodiment, similar to the second embodiment, the toner T entering the brush contact portion is pressed against the photosensitive drum 1 side by the brush voltage E. As a result, the toner T is sufficiently tribocharged at the brush contact portion, so that the charge distribution of the residual toner can be stabilized in the normal polarity. Therefore, it is possible to suppress inconveniences such as residual toner contaminating the charging roller 2 and the failure of the developing roller 41 to collect residual toner (poor collection).

[0192] Additionally, in this embodiment, as Figure 17 As shown, a structure is adopted in which the contact pressure and contact area ratio become the largest at the upstream part of the brush contact portion. Therefore, in the residual toner entering the brush contact portion, the polarity of the toner T, which is positively charged (non-normal polarity), can be rapidly changed to negative polarity by rubbing the bristle material of the brush member 11 to become charged, thereby further stabilizing the charge distribution of the residual toner in the normal polarity.

[0193] In this embodiment, a configuration is adopted in which the contact pressure and contact area ratio are maximized at the upstream portion of the brush contact portion by arranging the brush member 11 in an inclined state. The invention is not limited to this. For example, by employing a configuration in which the bristle height of the brush member 11 decreases from one side (upstream side of the rotation direction R1) relative to the short side direction SD to the other side (downstream side of the rotation direction R1), the contact pressure and contact area ratio can be maximized at the upstream portion of the brush contact portion.

[0194] In the above embodiments, a configuration including a charging roller 2 as a contact-charging type charging member was described; however, a charging member of a type other than contact charging (e.g., corona discharge type) can be used. Even in this case, by applying the configuration described in the above embodiments, poor collection of residual toner by the developing roller 41 can at least be suppressed.

[0195] Furthermore, while the above embodiments describe a direct transfer type configuration where the toner image is directly transferred from the photosensitive drum 1 (image carrier) to the sheet (recording material) serving as the toner image receiving member, the present invention can be applied to an intermediate transfer type imaging apparatus. In the intermediate transfer type, the transfer member refers, for example, to a transfer roller (primary transfer roller) used to transfer the toner image from the photosensitive drum 1 (image carrier) to the intermediate transfer member (toner image receiving member) in one pass. An annular belt member tensioned by multiple rollers can be used as the intermediate transfer member. The toner image transferred initially to the intermediate transfer member is then transferred a second time from the intermediate transfer member to the sheet (recording material) via a secondary transfer device (e.g., a secondary transfer roller) that forms a secondary transfer clamp between itself and the intermediate transfer member. Even in this intermediate transfer type configuration, by replacing each transfer roller in the above embodiments with a primary transfer roller, effects similar to those in the above embodiments can be obtained.

[0196] According to the present invention, the charge distribution of residual toner can be stabilized in the normal polarity.

[0197] <Fourth Embodiment>

[0198] Will use Figure 19 and Figure 20 An overview of the imaging apparatus 100 according to the fourth embodiment is described. Figure 19 This is a schematic diagram of the imaging device 100. Figure 20This is an enlarged view of the imaging unit 101 installed in the imaging apparatus 100. The imaging apparatus 100 is a monochrome printer used to form a monochrome image on a sheet S based on image information received from an external device. The sheet S, as the recording material, can be made of various sizes and materials, including paper such as plain paper or thick paper; plastic film; cloth; surface-treated sheet materials, such as coated paper; specially shaped sheet materials, such as envelopes or index paper; and so on.

[0199] like Figure 19 and 20 As shown, the imaging apparatus 100 includes an electrophotographic imaging unit 101 in which an image is formed on a sheet S, and a sheet feeding mechanism (6, 8, 12) for feeding and transporting the sheet S. The imaging unit 101 includes a photosensitive drum 1 as an image carrier, a charging roller 2 as a charging device, an exposure device 3 as an exposure device, a developing device 4 as a developing device, a transfer roller 5 as a transfer device, a brush member 11, and a fixing device 9 as a fixing device. In the imaging unit 101, the latent image unit 1A, including the photosensitive drum 1, the charging roller 2, and the brush member 11, and the developing device 4 as a developing unit, are configured to be detachably mounted to a housing C of the main assembly 100A of the imaging apparatus.

[0200] The photosensitive drum 1 is an electrophotographic photosensitive component formed into a drum shape. The photosensitive drum 1 has a drum shape (cylindrical shape) with a diameter of, for example, 24 mm, and is driven to rotate at a circumferential speed (processing speed) of 100 mm / sec during imaging. The charging roller 2 is a charging component of a contact structure example type, wherein the charging roller 2 contacts the photosensitive drum 1. The contact portion between the charging roller 2 and the photosensitive drum 1 is the charging portion P2 (charging position), where charging of the surface of the photosensitive drum 1 is performed.

[0201] The developing apparatus 4 includes a developing roller 41, a supply roller 42, a stirring member 43, a developing blade 44, and a toner container 45. The developing roller 41 is a developing member or a developer-carrying member used to supply toner T to the developing section P4 (developing position) where the developing roller 41 and the photosensitive drum are opposite each other, by rotating while carrying toner T. In this embodiment, a so-called contact developing type is used, wherein the toner layer carried on the developing roller 41 contacts the surface of the photosensitive drum 1 at the developing section P4. The developing roller 41 is arranged at an opening in the toner container 45 located opposite the photosensitive drum 1. The supply roller 42 supplies (applies) toner T from the supply chamber 45a of the toner container 45 to the developing roller 41. The stirring member 43 is arranged in the toner container 45 and stirs the toner T in the toner container 45 by rotation, and supplies toner T into the supply chamber 45a. The toner container 45 is a container for holding the toner T, which is a developer. The developing blade 44 contacts the surface of the developing roller 41 rotating toward the developing section P4 from inside the toner container 45 with a predetermined pressing force. The developing blade 44 is formed of a material (e.g., iron or copper) that is on the positive polarity side (abnormal polarity side) relative to the main component of the toner (binder resin) in the charge sequence. Thus, the toner T is rubbed and becomes negatively charged (normal (charge) polarity) through friction with the developing blade 44.

[0202] The developing roller 41 is, for example, a roller including a conductive rubber layer (elastic layer) and having a diameter of 12 mm. The supply roller 42 is a roller including a sponge-like outer layer, for example, having a diameter of 10 mm.

[0203] The transfer roller 5 is arranged to contact the surface of the photosensitive drum 1. The clamping part between the transfer roller 5 and the photosensitive drum 1 is the transfer part 5 for transferring the toner image from the photosensitive drum 1 to the sheet S.

[0204] The brush member 11 is arranged downstream of the transfer section P5 and upstream of the charging section P2, relative to the rotation direction R1 of the photosensitive drum 1. The brush member 11 is arranged to contact the surface of the photosensitive drum 1 under predetermined contact conditions. Details of the brush member 11 will be described later.

[0205] The fixing device 9 includes a fixing roller 9a or a flexible fixing film as a first rotating member, a pressing roller 9b as a second rotating member that contacts the first rotating member with a predetermined pressing pressure, and a heating device for heating the image on the sheet S through the first rotating member. As the heating device, a halogen lamp that generates radiant heat or a heater substrate with a pattern of heating resistors formed on a ceramic substrate can be used.

[0206] The sheet feeding mechanism includes a cassette 6, a feed roller 7, a feed (transfer) roller pair 8, and a discharge roller pair 12. The cassette 6 is a stacking section where stacked sheets S are arranged. The feed roller 7 is a feed member for feeding sheets one by one from the cassette 6. The feed roller pair 8 is a feed member for feeding the sheets S fed from the cassette 6 to the transfer section P5. The discharge roller pair 12 is a discharge member for discharging the sheets S on which the imaging section 101 has formed an image.

[0207] The following will describe an overview of the imaging operation via the imaging device 100. When an execution command for the imaging operation is provided to the imaging device 100, the photosensitive drum 1 moves along... Figure 20 The photosensitive drum 1 is driven to rotate in a predetermined rotation direction R1, and the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. The charging roller 2 rotates along the rotation direction R2 in which the charging roller 2 rotates together with the photosensitive drum 1 at the charging section P2. The exposure device 3 exposes the surface of the photosensitive drum 1 by irradiating it with a laser L that passes through the window 3a between the latent image unit 1A and the developing device 4 based on image information received from an external device. As a result, an electrostatic latent image is written (formed) on the surface of the photosensitive drum 1.

[0208] In this embodiment, a reverse development type is used. For this purpose, the charging roller 2 charges the surface of the photosensitive drum 1 to a negative dark potential Vd by being supplied with a voltage (charging voltage) of the same negative polarity as the toner T. After charging, the bright potential Vl of the area (image area) exposed by the exposure device 3 on the surface of the photosensitive drum is lower than the dark potential Vd. In the construction example of this embodiment, for example, the surface of the photosensitive drum is charged to Vd = -500 (V) using a DC charging voltage of -1100V.

[0209] In the developing apparatus 4, the toner T contained in the toner container 45 is homogenized by the stirring member 43 and supplied to the developing roller 41 via the supply roller 42. The toner T carried on the developing roller 41 is not only tribocharged to normal polarity through friction with the developing blade 44, but is also controlled to a predetermined layer thickness during its passage through the developing blade 44. By rotating the developing roller 41, the toner T with normal polarity is supplied to the developing section P4. Then, a voltage (developing voltage V) with the same normal polarity as the toner T is applied to the developing roller 41, thereby transferring the toner T onto the photosensitive drum 1 according to the potential distribution on the surface of the photosensitive drum 1. As a result, the electrostatic latent image on the surface of the photosensitive drum 1 is developed and visualized as a toner image. The developing voltage is, for example, -350V. Furthermore, the developing roller 41 rotates at a circumferential speed (e.g., 140 mm / sec) faster than the circumferential speed of the photosensitive drum 1, along the rotation direction R4 in which the developing roller 41 rotates together with the photosensitive drum 1 at the developing section P4. With the toner image on the photosensitive drum 1, the toner image formed on the surface of the photosensitive drum 1 is fed to the transfer section P5.

[0210] In parallel with the above process, sheet S is fed one sheet at a time from cartridge 6 via feed roller 7, and then conveyed to transfer section P5 via feed (transfer) roller pair 8. A voltage (transfer voltage) with a positive polarity opposite to the normal polarity of toner T is applied to transfer roller 5, causing the toner image to be transferred from photosensitive drum 1 to sheet S at transfer section P5. The transfer voltage is, for example, +1000V.

[0211] The sheet S, passing through the transfer unit P5, is conveyed to the fixing device 9. In the fixing device 9, the image on the sheet S is heated and fixed by the first rotatable member heated by a heating device while the sheet S is held and conveyed at the clamping part between the first rotatable member and the second rotatable member. The sheet S passing through the fixing device 9 is discharged by the discharge roller pair 12 to the discharge tray 13 provided at the upper part of the imaging device 100.

[0212] (Brush type without cleaner)

[0213] Next, a cleanerless brush type using brush member 11 will be described. In this embodiment, a simultaneous development and cleaning type is employed, wherein residual toner that is not transferred to the toner image receiving member (sheet S) at the transfer section P5 is collected by the developing roller 41 when the residual toner next reaches the developing section P4. In the simultaneous development and cleaning type, the residual toner collected by the developing roller 41 is stirred together with other toner in the toner container 45 and then reused for development.

[0214] In the simultaneous development and cleaning type, no residual toner transferred to the toner image receiving member at the transfer section P5 is collected by the developing roller 41, so the brush member 11 essentially allows residual toner to pass through. Therefore, the "brush member" in this embodiment is different from the brush member used as a cleaning device (drum cleaner) for removing residual toner from the photosensitive drum 1. Incidentally, in the simultaneous development and cleaning type, no cleaning device is arranged for collecting residual toner, so this type is sometimes referred to as the brush type without a cleaner.

[0215] In brush types without a cleaner, and in the simultaneous developing and cleaning type, the brush member 11, used to disperse residual toner deposited on the surface of the photosensitive drum 1 after passing through the transfer section P5, is arranged downstream of the transfer section P5 and upstream of the charging section P2 relative to the rotation direction R1. By arranging the brush member 11, the condition of a large amount of residual toner locally present on the photosensitive drum 1 can be alleviated. When a large amount of residual toner is locally present on the photosensitive drum 1, there is a possibility that poor charging may occur due to residual toner contaminating the charging roller 2, and image defects may occur due to poor collection of residual toner at the developing section P4. On the other hand, in the brush type without a cleaner, the residual toner is dispersed by the brush member 11, and the behavior of the residual toner at the charging section P2 and the developing section P4 is uniformized, thereby suppressing the above-mentioned inconveniences.

[0216] Furthermore, preferably, a brush voltage power supply E11 can be provided for applying a bias voltage (brush voltage) of the same polarity as the normal polarity of the toner T to the brush member 11. Figure 20 By applying a brush voltage to the brush member 11, the toner T with an abnormal polarity is held on the brush member 11, while the toner T with a normal polarity is allowed to pass through. Furthermore, when the abnormal polarity toner T held by the brush member 11 changes its polarity to a normal polarity through friction with the bristle material of the brush member 11, the abnormal polarity toner T held on the brush member 11 moves towards the charging section P2 while being carried on the surface of the photosensitive drum 1.

[0217] In this embodiment, the brush voltage applied to the brush member 11 is of such magnitude that no discharge occurs between the brush member 11 and the photosensitive drum 1. However, by applying the brush voltage to the brush member 11, a normally polarized charge is injected from the brush member 11 into the residual toner, thereby changing the polarity of the residual toner to the normal polarity.

[0218] Incidentally, a configuration in which no brush voltage is applied to the brush member 11 can be adopted. Even in this case, the toner T becomes triboelectrically charged at the brush contact portion, allowing the polarity of the toner T to change to its normal polarity. Furthermore, in the configuration in which no brush voltage is applied to the brush member 11, the brush member 11 can be a member electrically connected to the ground potential.

[0219] (Operation unique to brush types without cleaners)

[0220] In brush-type systems without a cleaner, residual toner reaches the charging section P2 through the contact area between the brush member 11 and the photosensitive drum 1. A charging voltage with the same polarity as the normal polarity of the toner is applied to the charging roller 2, so that toner particles with the normal polarity of charge pass through the charging section 2 while pressing against the photosensitive drum 1. On the other hand, toner particles with the abnormal polarity of charge or toner particles with a charge close to zero are partially deposited on the charging roller 2 at the charging section P2. When residual toner is deposited and accumulates on the charging roller 2, it prevents uniform charging of the photosensitive drum 1, making image defects caused by poor charging more noticeable.

[0221] In this embodiment, to reduce the deposition of residual toner on the charging roller 2, a circumferential speed difference is set between the charging roller 2 and the photosensitive drum 1. Specifically, the circumferential speed of the charging roller 2 is set to be at least 5%, preferably at least 10%, higher than the circumferential speed of the photosensitive drum 1. Furthermore, to charge the residual toner to the normal polarity through friction between the charging roller 2 and the photosensitive drum 1, the materials of the surface layers of the charging roller 2 and the photosensitive drum 1 are selected. That is, in the charging sequence, the materials of the surface layers of the charging roller 2 and the photosensitive drum 1 are at a higher level (positive polarity side, non-normal polarity side) than the main component of the toner (binder resin). By configuring the circumferential speed difference and materials as described above, at the charging section P2, the residual toner is charged to the normal polarity through friction with the charging roller 2 or the photosensitive drum 1, thereby suppressing the deposition of residual toner on the charging roller 2.

[0222] The residual toner from the charging section P2 reaches the developing section P4 as the photosensitive drum 1 rotates.

[0223] In the non-image area (non-exposure area), residual toner particles carried on the photosensitive drum 1, toner particles with normal polarity are transferred to the developing roller 41 and collected in the toner container 45 due to the potential difference between the dark area potential Vd and the developing voltage. On the other hand, in the image area (exposure area), residual toner particles carried on the photosensitive drum 1, toner particles with normal polarity are not transferred to the developing roller 41 due to the potential difference between the bright area potential Vl and the developing voltage, but remain on the photosensitive drum 1. In this case, the toner particles are sent to the transfer unit P5 as part of the toner image obtained by developing an electrostatic latent image. Incidentally, the developing voltage has the same polarity as the normal polarity of the toner, and is higher than the bright area potential Vl and lower than the dark area potential Vd.

[0224] Ideally, in residual toner particles, the polarity of toner particles with abnormal polarity and those with near-zero charge is changed to normal polarity, thus being collected by the developing roller 41 at the developing section P4 and not deposited on the charging roller 2. However, when a large amount of residual toner with abnormal polarity enters the charging section P2, residual toner whose polarity has not changed to normal polarity at the charging section P2 is prone to depositing on the charging roller 2. Furthermore, when residual toner whose polarity has not changed to normal polarity at the charging section P2 reaches the developing section P4, the residual toner passes through the developing section P4 without being collected by the developing roller 41. In this case, there is a possibility that the transfer roller 5 will be contaminated with residual toner and image defects such as pale toner images (white background haze) will form on the white background area (non-image area).

[0225] The components of the imaging device 100 will now be described in detail.

[0226] (Brush components)

[0227] First, the brush component 11 in this embodiment will be described. For example... Figure 19 and 20 As shown, relative to the rotation direction R1 of the photosensitive drum 1, the brush member 11 contacts the surface of the photosensitive drum 1 at a position downstream of the transfer section P5 and upstream of the charging section P2. That is, the imaging apparatus 100 includes a brush member 11 arranged downstream of the transfer section and upstream of the developing section relative to the rotation direction of the image carrying member, and in contact with the surface of the image carrying member. In the following text, the area where the brush member 11 contacts the photosensitive drum 1 is referred to as the "brush contact area".

[0228] Figure 21 Part (a) is a perspective view of latent image unit 1A. Figure 21 Part (b) is a cross-sectional view of the latent image unit 1A in a plane perpendicular to the rotation axis of the photosensitive drum 1. Figure 21 Part (c) shows the direction of rotation of the photosensitive drum 1 along the upstream side R1. Figure 21 A schematic diagram of the state of the brush contact portion as seen in the direction of arrow 4C in part (b). The brush member 11 is fixed to and supported by the support surface 14a provided on the frame 14 of the latent image unit 1A (which is used to rotatably support the photosensitive drum 1 and the charging roller 2).

[0229] Figure 22 Part (a) is a cross-sectional view of the brush member 11 in its single-unit state, cut along a plane perpendicular to the longitudinal direction of the brush member 11. The single-unit state is the state in which the brush member 11 is not mounted on the frame 14, which serves as a support member of the latent image unit 1A, i.e., the state in which no external force is acting on the brush member 11. Figure 22Part (b) is a cross-sectional view of the brush member 11 in the state of contact between the brush member 11 and the photosensitive drum 1.

[0230] like Figure 22 As shown in parts (a) and (b), the brush member 11 includes a base fabric 11b as a base and conductive filaments (wires) 11a as bristle material (fibers) supported by the base fabric 11b. The base fabric 11b is formed of synthetic resin fibers containing carbon black as a conductive agent. The conductive filaments 11a are formed of, for example, nylon fibers (pile yarn) with added conductive agents, and are woven and flocked onto the base fabric 11b. The material of the conductive filaments 11a is not limited to nylon, but other synthetic resin fibers can be used, such as rayon, acrylic resin, or polyester resin fibers.

[0231] The brush member 11 is a member that extends elongatedly in a predetermined direction. In the following text, the direction of extension is referred to as the longitudinal direction LD of the brush member 11 (see also...). Figure 21 Part (a)), along the base fabric 11b and perpendicular to the longitudinal direction LD, is called the short side direction SD of the brush member 11. In the single-unit state where no external force acts on the brush member 11 ( Figure 22 Part (a) shows that the conductive wire 11a protrudes in a direction that is substantially perpendicular to both the longitudinal direction LD and the short side direction SD (the normal direction of the base fabric 11b).

[0232] like Figure 22 As shown in part (a), the distance from the base fabric 11c in the single-unit brush member 11 to the free end of the conductive filament 11a is the bristle height L1. In the example of this embodiment, the bristle height L1 of the brush member 11 is 5.75 mm. The brush member 11 is fixed to the frame 14 of the latent image unit 1A by a fixing device such as double-sided tape. Figure 21 Part (b)). The support surface of the frame 14 for the brush member 11 is configured such that the free end of the conductive wire 11a enters the photosensitive drum 1. For this purpose, the brush member 11 is in a state where the free end of the conductive wire 11a is pressed against the surface of the photosensitive drum 1 and flexed (bent).

[0233] like Figure 21 As shown in part (c), the brush member 11 is arranged in a posture in which its longitudinal direction LD is substantially parallel to the rotation axis of the photosensitive drum 1.

[0234] On the other hand, Figure 21Part (b) shows a schematic diagram of a brush member 11 arranged in a posture with its short side direction SD substantially parallel to the surface of the photosensitive drum 1; however, the angle of the brush member 11 is not limited to this. In this embodiment, the brush member 11 is arranged in an inclined state relative to the surface of the photosensitive drum 1. That is, the support surface 14a of the brush member 11 (and the base fabric 11b supported by the support surface 14a) is arranged in an inclined state relative to the tangential direction of the photosensitive drum 1, so as to move away from the surface of the photosensitive drum 1 in the downstream direction of the rotation direction R1 of the photosensitive drum 1. The definition and range of the tilt angle of the brush member 11 will be described later.

[0235] The minimum distance from the base fabric 11b of the brush member 11, which is fixed to the support surface 14a, to the photosensitive drum 1 is taken as L2. In this embodiment, the difference between L2 and L1 (L1-L2) is the maximum intrusion amount of the brush member 11 into the photosensitive drum 1. However, L2 < L1 holds true.

[0236] In this example embodiment, the maximum intrusion of the brush member 11 into the photosensitive drum 1 is, for example, 1.58 mm. Furthermore, in this embodiment, as... Figure 21 Part (b) and Figure 22 As shown in part (a), for the brush member 11 in its single-unit state, the length of the brush member 11 relative to the short side direction SD (the length within the range of the implanted conductive wire 11a), i.e., the short side (side) width L3, is, for example, 4 mm in this embodiment. The short side width L3 is preferably 3 mm or more to maintain the performance of the brush member 11 over a long period. Figure 22 As shown in part (b), when the brush member 11 is pressed against the photosensitive drum 1, the width occupied by the conductive wire 11a relative to the short side direction SD is slightly wider.

[0237] Furthermore, in this example, the longitudinal width L4 (representing the length of the brush member 11 relative to the longitudinal direction LD) Figure 21 Part (c) is 216 mm. The longitudinal width L4 is set such that, relative to the longitudinal direction LD, the brush member 11 can contact the entire area of ​​the imaging area (the toner image formation area, the largest area of ​​the latent image formed by the exposure device 3) on the photosensitive drum 1. Furthermore, in the example of this embodiment, the thickness of the conductive wire 11a is, for example, 2 denier, and the density of the conductive wire 11a is 240 kF / inch. 2 Here, 1kF / inch 2 This is a density of 1000 fibers per square inch. The thickness and density of the conductive filament 11a can be appropriately varied, as long as the conductive filament 11a meets the functional requirements of the brush component 11. As an example, it is preferred that the thickness of the conductive filament 11a is 1 denier or more and 6 denier or less, and the density of the conductive filament 11a is 150 kF / inch. 2 Above and 350kF / inch2 Below. Incidentally, 1kF / inch 2 This indicates a planting density of 1000 fibers per square inch.

[0238] Incidentally, in the case of the nylon conductive filament 11a used in this embodiment, when converting 1 to 6 denier (which is a unit of yarn count for a fixed length) to fiber diameter, 1 to 6 denier corresponds to approximately 10 μm to approximately 30 μm. Therefore, when using a bristle material other than nylon as the brush component, bristle materials with a thickness of 1 denier or more and 6 denier or less in terms of yarn count for a fixed length, and a fiber diameter of 10 μm or more and 30 μm or less can be used.

[0239] "1 denier or higher and 6 denier or lower" can be referred to as "1.1 points or higher and 6.7 points or lower". Additionally, 1 inch... 2 Approximately 6.45cm 2 Therefore, "150kF / inch" 2 Above and 350kF / inch 2 The following can be referred to as "23kF / mm". 2 Above and 54kF / mm 2 the following".

[0240] In this embodiment, the brush member 11 is configured to allow residual toner to pass through while dispersing the residual toner deposited on the surface of the photosensitive drum 1 that has passed through the transfer section P6. Therefore, if the conductive filament 11a is too thick, there is a possibility that the residual toner cannot be evenly dispersed and passes through the brush contact in a striped pattern, thus causing the residual toner to contaminate the charging roller 2 in a striped pattern. Furthermore, if the density of the conductive filament 11a is too high, the residual toner is blocked by the brush contact, thus not only creating an obstacle for the developing roller 41 to collect the residual toner, but also contaminating the interior of the imaging device due to the residual toner falling or scattering from the photosensitive drum 1. In addition, the brush member 11 has the function of triboelectrically charging the residual toner at the brush contact. Therefore, if the conductive filament 11a is too thin, there is a possibility that even when the residual toner contacts the conductive filament 11a, the conductive filament 11a easily bends and bypasses the residual toner, thus the toner particles cannot roll and the residual toner cannot be sufficiently triboelectrically charged. Furthermore, if the density of the conductive wire 11a is too low, the frequency of collisions with the conductive wire 11a will decrease, which may result in the residual toner not being able to be sufficiently charged through friction.

[0241] In the above description, the preferred range of thickness and density of the conductive wire 11a was described from the perspective of its function in dispersing residual toner and in causing residual toner to become triboelectrically charged. However, details such as thickness, density, material, and bristle height can be appropriately changed depending on the required function of the brush member 11. Incidentally, the brush member 11 in this embodiment may have the function of blocking foreign matter (e.g., paper dust) other than residual toner at the brush contact portion.

[0242] (Developer)

[0243] In this embodiment, toner T, a single-component developer, is used as the developer, and its normal polarity (normal charge polarity) is negative. Therefore, in the following description of this embodiment, unless otherwise specified, "negative polarity" is synonymous with the normal polarity of toner T, and "positive polarity" is synonymous with the abnormal polarity of toner T.

[0244] The toner T contains a binder resin and a colorant, and may also contain a release agent, a charge control agent, and external additives as needed. As the binder resin, styrene-acrylic resin and polyester resin are preferably used, as their charge sequence positions (negative polarity side) are lower than those of the nylon and rayon constituting the conductive filaments 11a of the brush member 11. That is, the main component of the toner T (binder resin) can ideally be located on the positive polarity side (lower position) in the charge sequence relative to the material of the brush bristles of the brush member 11. In this embodiment, styrene-acrylic resin is used as the binder resin for the toner.

[0245] As a colorant, known colorants can be used. Examples include dyes and pigments. As a release agent, known charge control agents can be used. The charge control agent has an acid value or hydroxyl value, and preferably has a negative polarity equal to or greater than that of the binder resin. As an external additive, known external additives can be used. Examples include silica, alumina, titanium dioxide, titanium composite oxides, etc. The colorant and release agent are preferably contained in the binder resin so as not to affect the polarity of the colorant particle surface.

[0246] Furthermore, as a toner, a polymeric toner formed by a polymerization method can be used. A toner T with a particle size (volume average particle size) of 4 μm to 10 μm, preferably 6 μm to 8 μm, is preferred. In this embodiment, a spherical toner with a particle size of 7 μm prepared by a polymerization method is used. Furthermore, the toner T in this embodiment is a so-called non-magnetic single-component developer, which does not contain magnetic components and is mainly supported on the developing roller 41 by intermolecular forces or electrostatic forces (mirror forces). However, as a developer, a single-component developer composed of a toner containing magnetic components can be used. Furthermore, as a developer, a two-component developer composed of a non-magnetic toner and a magnetic carrier can be used. In the case of using a magnetic developer, a cylindrical developing sleeve in which a magnet is disposed is used, for example, as the developer carrier. In addition to the toner and carrier, additives (e.g., wax or fine silica particles) for adjusting the toner's flowability, charge properties, etc., can be added to the developer.

[0247] (Photosensitive drum)

[0248] The photosensitive drum 1 is prepared by sequentially layering a base coating, a charge generation layer, and a charge transport layer onto a cylindrical conductive support member (core metal) as the bottom layer. The charge transport layer is formed by coating and drying a paint prepared primarily by mixing a charge transport material and a binder resin in a solvent. Known charge transport materials can be used as the main charge transport material. Examples include various triarylamine compounds and hydrazone compounds. Furthermore, examples of binder resins include, for instance, polycarbonate resins and polyarylate resins.

[0249] The main component that becomes triboelectrically charged with the toner is the charge-transporting layer, which is the surface layer (outermost layer), and is primarily composed of the binder resin. Here, the polycarbonate resin or polyarylate resin is located on the non-normal polarity side (superior) relative to the styrene-acrylic resin (which is the binder resin for toner T) in the charge sequence. That is, the outermost layer of the image carrier member, when rubbed against the resin, which is the main component of toner T, can preferably be formed of a material capable of triboelectrically charging the toner T to its normal polarity. In this embodiment, polycarbonate resin is selected as the binder resin for the outermost layer.

[0250] Furthermore, in this embodiment, a cylindrical photosensitive drum with an outer diameter of 24 mm is used as the photosensitive drum 1. The contact (pressing) method of the brush member 11 is appropriately changed according to the outer diameter of the photosensitive drum 1 (for example, the amount of penetration described above or the angle described later in the sixth embodiment).

[0251] (Charging roller)

[0252] The charging roller 2 in this embodiment will be described. The charging roller 2 includes a core metal as a conductive support member, a 2 mm thick elastic layer disposed on the outer periphery of the core metal, and a 25 mm thick resin layer disposed on the outer periphery of the elastic layer as a surface layer. The surface of the surface layer is the surface that contacts the photosensitive drum 1 and causes discharge on the photosensitive drum 1.

[0253] The elastic layer is formed of an electronically conductive rubber material. This electronically conductive rubber material is, for example, a material in which carbon black, as conductive particles (electronically conductive agent), is dispersed in a binder polymer that is not conductive in itself, and where the resistance is adjusted. As the binder polymer, known binder polymers used in the conductive elastic layer of the charging roller for an electrophotographic device can be used. Examples include alcohol rubber and butadiene rubber. In this embodiment, alcohol rubber is selected.

[0254] The type of carbon black mixed in the elastic layer is not particularly limited, as long as the carbon black is conductive and can impart conductivity to the elastic layer. Furthermore, as needed, general-purpose agents such as fillers, processing aids, crosslinking aids, crosslinking inhibitors, softeners, dispersants, and colorants can be added to the elastic layer as compounding agents.

[0255] The resin used as the surface layer of the charging roller 2 is a resin material that is located on the non-normal polarity side (upper position) relative to the main component (binder resin) of the toner T in the charging sequence. For example, the surface layer is formed by coating the outer periphery of the elastic layer with a conductive resin material (e.g., polycarbonate polyurethane). By forming the third layer of the photosensitive drum 1 and the third layer of the charging roller 2 with the above-described materials, and by setting the circumferential speed difference between the charging roller 2 and the photosensitive drum 1 as described above, the residual toner can be tribocharged to the normal polarity at the charging section P2.

[0256] Furthermore, roughening particles with a certain polarity can be added to the surface layer of the charging roller 2 so as not to impair triboelectricity. For example, there are also methods that prepare polycarbonate polyurethane resin similar to the polycarbonate polyurethane resin of the surface layer into particles and disperse the particles. That is, the charging roller 2 does not need to be in close contact with the surface of the photosensitive drum 1 at the charging section P2, so a structure in which the charging roller 2 contacts the surface of the photosensitive drum 1 at the uneven peaks formed by the roughening particles can be adopted.

[0257] (Transfer roller)

[0258] The transfer roller 5 is a roller-type transfer component arranged opposite to the photosensitive drum 1. The transfer roller 5 presses against the photosensitive drum 1 with a predetermined pressure. In this embodiment, the transfer roller 5 is an elastic roller with an outer diameter of 12 mm, wherein a conductive nitrile rubber-alcohol rubber type sponge rubber is formed around the core metal.

[0259] (Contact conditions for brush components)

[0260] In this embodiment, the brush member 11 imparts charge to the residual toner through triboelectric charging, while simultaneously dispersing the residual toner onto the photosensitive drum 1. To impart a negative charge to the residual toner through triboelectric charging, the material used for the brush bristles (conductive filament 11a) of the brush member 11 is a material that is located on the positive polarity side (superior position) relative to the main component of the toner T in the charging sequence. Furthermore, the contact pressure between the brush member 11 and the photosensitive drum 1 at the brush contact portion is ensured so that the conductive filament 11a rubs the residual toner with sufficient force.

[0261] Regarding the charge sequence, the main component of the toner T in this embodiment is styrene-acrylic resin. The bristle material of the brush member 11 can ideally be a material such as nylon or rayon, with styrene-acrylic resin located on the negative polarity side (lower position) relative to this material, and the charge sequence difference between them is relatively large. In this embodiment, as described above, nylon resin is selected as the main component of the conductive filament 11a. Polyester and acrylic fibers are not ideal materials for the conductive filament 11a because styrene-acrylic resin is located on the positive polarity side relative to polyester and acrylic fibers in the charge sequence, and the charge sequence difference is also small. However, in cases where the main component of the toner T is different, polyester or acrylic fibers can be used as the material for the conductive filament 11a in some situations.

[0262] Incidentally, the surface layer of the photosensitive drum 1 can influence the triboelectric charging of the toner T at the brush contact portion. Therefore, the main component of the surface layer of the photosensitive drum 1 can preferably be a material located on the positive polarity side relative to the main component of the toner T in the charging sequence. In this embodiment, as described above, the main component of the surface layer of the photosensitive drum 1 is polycarbonate resin.

[0263] The contact conditions of the brush member 11 at the brush contact portion will be further described. To investigate the physical properties (parameters) representing the contact conditions of the brush member 11, four samples 1 to 4 with different bristle material coarseness and density were prepared. Sample 1 is a brush member 11 with coarse bristle material and low density. Sample 2 is a brush member 11 with fine bristle material and medium density. Sample 3 is a brush member 11 with fine bristle material and high density. Sample 4 is a brush member 11 with medium bristle material coarseness and low density. Then, the brush member 11 of each sample was brought into contact with the photosensitive drum 1, and the peak pressure and maximum contact area ratio at the brush contact portion were calculated as follows. Incidentally, the peak pressure is the maximum value of the average contact pressure in a region with a width of 1 mm relative to the short side direction of the brush contact portion, and the maximum contact area ratio is the contact area ratio between the brush member 11 and the photosensitive drum 1 in the region with a width of 1 mm where the peak pressure is obtained.

[0264] The peak pressure is calculated as follows. For example... Figure 24 As shown in part (a), a compression test fixture for a small benchtop testing machine (Shimadzu Corporation's "EZtest") was used to measure the vertical resistance when the pressing plate 71 was pressed into the brush member 11 while adjusting the flow of the bristles (fibers) of the horizontally placed brush member 11. The relationship between the intrusion amount and the vertical resistance was then obtained. On the other hand, as... Figure 24 As shown in part (b), the glass plate is pressed against the brush member 11 in a manner that ensures the flow of the bristles of the brush member 11 is consistent while the glass plate is moved along the horizontal direction D. The contact width 73 of the brush member 11 relative to the short side direction SD is measured by observing the brush contact portion with a microscope from the side opposite to the glass plate 72. The horizontal direction D is one side of the short side direction SD corresponding to the rotation direction R1 of the photosensitive drum 1.

[0265] When the brush member 11 is prepared to have uniform density and thickness of its bristle material, the peak pressure can be calculated using the above-described formulas (Formulas 1 to 3). First, the average value of the contact pressure at the brush contact portion (average pressure) when the object presses against the brush member 11 with a predetermined amount of penetration can be represented by formula (Formula 1). In formula (Formula 1), the vertical resistance and contact width are values ​​measured when the pressing plate 71 or the glass plate 72 presses against the brush member 11 with a predetermined amount of penetration.

[0266] At the actual brush contact portion between the brush member 11 and the photosensitive drum 1, the contact pressure becomes maximum in the portion where the brush member 11 penetrates the photosensitive drum 1 to the greatest extent. This maximum contact pressure is called the peak pressure. The peak pressure is calculated using the average penetration amount (Formula 2) obtained from the maximum and minimum penetration amounts of the brush member 11 via Formula 3.

[0267] The above calculation method actually means applying to, for example Figure 6 The contact pressure on the surface of the photosensitive drum 1, drawn as an arc, is linearly approximated. Specifically, assuming a brush member 11 with a short side (side) width L3 of 4 mm contacts the photosensitive drum 1 with a diameter of 24 mm directly above it, the intrusion amount at the center of the photosensitive drum 1 in the direction relative to the short side SD becomes 1.2 mm. In this case, the maximum intrusion amount is 1.2 mm, the minimum intrusion amount is 1.03 mm, and the average intrusion amount is 1.115 mm, so the peak pressure can be calculated using (Equation 3).

[0268] Incidentally, when the density, thickness, etc. of the brush member 11 are not uniformly set relative to the short side direction SD, the brush member 11 is cut at a unit length (e.g., 1 mm) relative to the short side direction SD, and then the vertical resistance is measured to obtain the contact pressure in each unit length area (range). Then, the average value of the obtained contact pressure values ​​is taken as the average pressure, and the maximum value is taken as the peak pressure.

[0269] In order to perform calculations, such as Figure 25 As shown, the distinction is made by the color tone between the portion of the brush member 11 that contacts the glass plate g (contact portion) and the portion of the brush member 11 that does not contact the glass plate g (non-contact portion). Figure 7 Part (a) is an actual photograph observed through a microscope. Figure 7 Part (b) is by making Figure 7 The image in part (a) is binarized to make the contact area white and the non-contact area black. The contact area ratio is the ratio of the area of ​​the contact area to the area of ​​the object being observed. Typically, the contact area ratio becomes the largest (maximum contact area ratio) relative to the short side direction SD at the location where peak pressure is obtained.

[0270] In summary, regarding the imaging device including the brush member 11 as in this embodiment, the peak pressure and maximum contact area ratio can be determined in the following process.

[0271] 1) Measure the outer diameter of the photosensitive drum 1, the bristle height L1 of the brush member 11, the short side width L3 and the longitudinal width L4, and the shortest distance L2 from the base fabric 11b of the brush member 11 to the surface of the photosensitive drum 1, and calculate the maximum intrusion amount (L1-L2) (see...). Figure 20 Parts (b) and (c)).

[0272] 2) Based on the outer diameter of the photosensitive drum 1, the short side width L3 of the brush member 11, and the maximum intrusion amount measured in 1) above, based on Figure 6 The minimum intrusion amount is calculated based on the geometric relationship.

[0273] 3) Based on the maximum and minimum intrusion amounts obtained through 1) and 2) above, calculate the average intrusion amount based on (Formula 2).

[0274] 4) Using the average intrusion amount calculated in 3) above, through Figure 24 Compression tests of brush component 11 were performed using methods (a) and (b) to obtain the average pressure based on (Formula 1).

[0275] 5) Calculate the peak pressure based on (Formula 3) by using the maximum intrusion amount, average intrusion amount and average pressure obtained from 1), 3) and 4) above.

[0276] 6) Of the maximum intrusion amount obtained in 1) above, through Figure 25 The method involves pressing the brush component 11 against the glass plate, then observing the contact surface to calculate the maximum contact area ratio.

[0277] Furthermore, in order to make the peak pressure and maximum contact area ratio of the brush component 11 the desired value, parameters such as the outer diameter of the photosensitive drum 1, the bristle height L1 and the short side width L3 of the brush component 11, and the aforementioned shortest distance L2 are appropriately changed, so that the peak pressure and maximum contact area ratio can be checked only during the above process.

[0278] Figure 1 The graph shows the following: In the above method, peak pressure and maximum contact area ratio are calculated for each sample under multiple different conditions, and the peak pressure value is plotted on the vertical axis and the maximum contact area ratio value is plotted on the horizontal axis. Figure 1 In the diagram, black marks indicate points where no image defects are present, while white marks indicate points where image defects are present.

[0279] like Figure 1 As shown, when the peak pressure is less than 0.7 gf / mm 2 Furthermore, image defects occur when the maximum contact area ratio is less than 18%. This is believed to be because, under excessively low peak pressure, only a portion of the bristle material of the brush member 11 contacts the photosensitive drum 1, thus insufficient to tribocharge the residual toner to the normal polarity. Additionally, this is also believed to be because, under excessively low maximum contact area ratio, the contact frequency between the toner particles and the bristle material of the brush member decreases, further reducing the effectiveness of tribocharging the residual toner to the normal polarity. In either case, when the residual toner reaches the charging section P2 without being adequately charged with a positive polarity at the brush contact portion, residual toner with an abnormal polarity or a charge close to zero deposits on the charging roller 2, resulting in contamination of the charging roller 2.

[0280] Furthermore, at peak pressures above 3.5 gf / mm 2Image defects occur when the peak pressure or maximum contact area ratio is higher than 74%. This is believed to be because, under either excessively high peak pressure or excessively high maximum contact area ratio, a portion of the brush contact is in a state where residual toner cannot pass through that portion of the brush contact, thus the residual toner concentrates on the portion that can pass through (where the contact pressure or density of the brush bristle material is relatively low). In this case, the surface of the photosensitive drum 1 through which the brush contact passes is in a state where residual toner is deposited in a stripe shape (a linear shape extending in the rotational direction), causing the charging roller 2 to be contaminated with residual toner in a stripe shape. Incidentally, in areas where the peak pressure or maximum contact area ratio is particularly high, residual toner is blocked by the brush member 11, thus creating the possibility that not only is the collection of residual toner by the developing roller 41 hindered, but the blocked toner also scatters and contaminates the interior of the imaging device with the scattered toner.

[0281] Therefore, it is desirable that the brush component 11 be configured such that the ratio of peak pressure to maximum contact area at the brush contact portion falls within the range determined by... Figure 1 The area enclosed by the dashed line below.

[0282] (Peak pressure): 0.7 gf / mm 2 Above and 3.5gf / mm 2 the following

[0283] (Maximum contact area ratio): 18% or more and 74% or less

[0284] Therefore, in a cleanerless brush type where residual toner deposited on the surface of the photosensitive drum 1 after passing through the transfer section P5 is dispersed by the brush member 11, the charge distribution of the residual toner can be stabilized at the normal polarity. In other words, the charge distribution of the residual toner after passing through the brush contact section can be made to have a peak on the normal polarity side (negative polarity side) of the toner T and be sharper than the charge distribution of the residual toner before entering the brush contact section.

[0285] Incidentally, in the area enclosed by the dotted line, the aforementioned image defects are less likely to occur at the center compared to the periphery. Therefore, it is preferable that the brush member 11 is configured such that the peak pressure and / or maximum contact area ratio further fall within the following ranges.

[0286] (Peak pressure): 1.4 gf / mm 2 Above and 2.8gf / mm 2 the following

[0287] (Maximum contact area ratio): 32% or more and 60% or less

[0288] Here, 1 gf is approximately equal to 9.8 × mN (milline Newtons), therefore "0.7 gf / mm 2 Above and 3.5gf / mm 2 The following can be referred to as "6.9 mN / mm". 2 Above and 34mN / mm 2 "The following." Similarly, "1.4gf / mm" 2 Above and 2.8gf / mm 2 The following can be referred to as "14mN / mm". 2 Above and 28mN / mm 2 the following".

[0289] Furthermore, in this embodiment, the Clark-Evans index is introduced as an index to indicate whether the brush member 11 contacts the photosensitive drum 1 uniformly. The Clark-Evans index indicates whether, when multiple points are distributed in a certain flat surface area, these points tend to be locally concentrated or distributed at a distance from each other.

[0290] The calculation method of the Clark-Evans index will be described. First, when the distance from point i to its nearest neighbor is d_i and the number of points is n, the average distance from each point to its nearest neighbor (average nearest neighbor distance) W is expressed by the above formula (Mathematical Formula 1).

[0291] Here, as an evaluation criterion, we will consider the case where points are randomly distributed on a flat surface of area S (according to a uniform Poisson distribution). In this case, the expected value E(W) of the average nearest neighbor distance W is expressed by the above formula (Mathematical Equation 2).

[0292] To compare cases where the number of points and density differ from each other, the value w obtained by standardizing the average nearest neighbor distance W with the expected value E(W), as expressed in the above formula (Mathematical Formula 3), is called the Clark-Evans index.

[0293] To obtain the Clark-Evans index for brush component 11, such as Figure 23 As shown in part (a), the brush member 11 is pressed against the surface of a glass plate, and the brush contact portion is viewed through the glass plate surface from the side opposite to the side where the brush member 11 is pressed against the glass plate surface. In the brush contact portion, when a specific area (100mm) 2 When the free ends of the bristle material in the diagram are represented by points, the following is obtained: Figure 23 The distribution of points is shown in part (b). Based on this distribution, the Clark-Evans index is calculated using the formulas (Mathematical Formulas 1 to 3) described above.

[0294] Incidentally, a portion of the bristle material even contacts the glass (plate) surface at a location closer to the base than the free end. The triboelectric effect of the toner T through this bristle material is considered to contribute significantly to the portion of the bristle material that most strongly contacts the glass surface (the strongest pressure point). However, the distribution of the strongest pressure points of the bristle material is generally the same as the distribution at the free end of the bristle material, and the properties of the distribution remain essentially unchanged. Therefore, in this embodiment, the Clark-Evans index is calculated based on the distribution of the free ends of the bristles contacting the glass surface.

[0295] Regarding the Clark-Evans index, it holds true for a random distribution where w = 1, for a concentrated distribution where w < 1, and for a regular distribution where w > 1. An extreme example of a regular distribution is a lattice-like distribution that covers the entire area of ​​the observed object. An extreme example of a concentrated distribution is a distribution where points are concentrated in a single part or several parts of the observed object's area.

[0296] The Clark-Evans index of the actual sample of brush component 11 is obtained as follows.

[0297] Sample 1: w = 1.01

[0298] Sample 2: w = 1.13

[0299] Sample 3: w = 1.15

[0300] Sample 4: w = 1.07

[0301] The sample obtained by intentionally twisting sample 2 into a bundle: w = 0.7

[0302] According to the properties of the Clark-Evans index, when w > 1, it can be said that the free ends of the bristle material of brush component 11 are loose and not bundled. On the other hand, when w < 1, it means that the bristle material of brush component 11 is bundled (aggregated, clumped) for some reason.

[0303] For the brush member to function properly, it is preferable that the bristles of the brush member 11 contact the surface of the photosensitive drum 1 in a loose and non-bundled state. In this embodiment, the brush member 11 is configured such that the Clark-Evans index is 1 or higher (w≥1). This condition can be considered as a condition to ensure that the bristle material does not clump together for any reason.

[0304] Incidentally, based on the construction of the brush member 11, it is also possible to consider that even within the brush contact portion, the value of the Clark-Evans index varies depending on the location. In this case, the Clark-Evans index is greater than 1 at the portion of the brush member 11 where the penetration amount is the largest (the location where the contact pressure is the peak pressure). This is because at the portion with the largest penetration amount, it is easier to form a bristle bundle through the force received by the bristle material.

[0305] (Layout of brushed components)

[0306] Next, the arrangement of the brush member 11 relative to the photosensitive drum 1 will be described. In this embodiment, the brush member 11 is arranged in an inclined state, such that the contact pressure between the brush member 11 and the photosensitive drum 1 is higher at the brush tip (brush head end) than at the brush tail (brush tail end). Here, "brush tip" refers to the end of the brush member 11 in the rotation direction R1 relative to the photosensitive drum 1 on the upstream side, and "brush tail" refers to the end of the brush member 11 in the rotation direction R1 relative to the photosensitive drum 1 on the downstream side.

[0307] In the following text, we will use Figure 18 The specific layout of brush component 11 is described. Figure 18 This is a schematic diagram illustrating the arrangement of the brush member 11 relative to the photosensitive drum 1. Figure 18 The state of the brush member 11 and the photosensitive drum 1 when viewed along the rotation axis of the photosensitive drum 1 (the longitudinal direction LD of the brush member 11) is shown. Incidentally, the brush bristle material (conductive filament 11a) of the brush member 11 is actually shown in a state where the bristle material extends without interfering with the photosensitive drum 1 (single state).

[0308] exist Figure 18 In the diagram, the rotation axis of the photosensitive drum 1 is represented by "O". A straight line extending from the rotation axis O through the center position of the base fabric 11b of the brush member 11 relative to the short side direction SD (the first straight line) is represented by "m". A straight line perpendicular to line m is represented by "Lt". Line Lt is a straight line parallel to the tangent t at the intersection point p between line m and the surface of the photosensitive drum 1. Furthermore, a straight line drawn along the base fabric 11b (the third straight line extending along the short side direction SD) is represented by "n".

[0309] In this embodiment, the brush member 11 is arranged such that the straight line n drawn along the base fabric 11b is inclined with respect to the straight line Lt extending in the tangential direction on the surface of the photosensitive drum 1 about the direction that causes the base fabric 11b to approach the surface of the photosensitive drum 1 upstream of the rotation direction R1 toward the photosensitive drum 1.

[0310] The angle β (°) between lines n and Lt represents the tilt angle of brush member 11. The tilt angle β can be appropriately set in a range, for example, greater than 8° and less than 16°. When β is too large, the difference in intrusion amount between the brush tip and the brush back end becomes large, thus there is a possibility that the intrusion amount at the brush tip becomes too large, causing toner blockage, and the intrusion amount at the brush back end becomes negative (non-contact). When β is too small, as described below, it is difficult to provide an appropriate difference in contact pressure and contact area ratio between the brush tip and the brush back end.

[0311] In this example, β = 12° is set. In this case, the intrusion of the brush member 11 into the photosensitive drum 1 becomes the maximum at the brush tip, and its value (maximum intrusion) is 1.58 mm.

[0312] As described above, the brush member 11 is arranged in an inclined state, thereby making the contact pressure and contact area ratio at the brush tip higher than those at the brush rear end. That is, in the brush contact portion (the contact portion between the brush member and the image carrier member), the contact pressure at the first position is higher than the contact pressure at the second position located downstream of the first position relative to the rotation direction R1 of the image carrier member. Furthermore, the contact area ratio between the brush member and the image carrier member at the first position is higher than that at the second position.

[0313] In this example, the contact pressure at the brush tip is 2 gf / mm. 2 The contact pressure at the brush rear end is 1 gf / mm. 2 Furthermore, the contact area ratio at the brush tip is 50%, and the contact area ratio at the brush rear end is 20%. In this embodiment, Figure 26 Part (a) shows the relationship between the short-side position of the brush member 11 and the contact pressure. Figure 26 Part (b) shows the relationship between the short-side position of brush member 11 and the contact area ratio. Figure 26 The relationship between contact pressure and contact area ratio is shown in section (c). Here, the position of the brush member 11 in the short side direction is relative to the short side direction SD, with the brush tip as the reference (0).

[0314] Figure 26The examples shown in parts (a) and (b) are examples of constructions where the contact pressure to contact area ratio at a first position on the brush tip side is higher than that at a second position on the brush rear side compared to the first position. The curves plotted to represent the contact pressure to contact area ratio may differ. As in this example, it is preferred that the contact pressure to contact area ratio becomes maximum at the brush tip. Furthermore, it is preferred that the contact pressure to contact area ratio decreases monotonically from the brush tip to the brush rear, but this is acceptable as long as the contact pressure to contact area ratio at least at the brush tip is higher than that at the brush rear.

[0315] Preferably, the difference between the contact pressure (maximum value) at the brush tip and the contact pressure (maximum value) at the brush rear end is 0.6 gf / mm. 2 Above and 1.5gf / mm 2 Furthermore, it is preferable that the difference between the contact area ratio (maximum value) at the brush tip and the contact area ratio (maximum value) at the brush rear end is 15% or more and 40% or less.

[0316] Furthermore, in this embodiment, as will be described in detail later, the intrusion amount δ1 (mm) of the brush tip into the photosensitive drum 1 and the intrusion amount δ2 (mm) of the brush rear end into the photosensitive drum 1 satisfy the relationship: δ1>δ2>0.

[0317] (Brush applies bias voltage)

[0318] Additionally, the brush power supply E11, which serves as a voltage application device, Figure 20 The brush is connected to the brush member 11. During imaging, a predetermined voltage (brush bias) is applied to the brush member 11 via the brush power supply E11. In this embodiment, a negative DC voltage is applied to the brush member 11 as the brush voltage during imaging. In this embodiment, the brush voltage during imaging is -350V. On the other hand, the surface potential of the surface area of ​​the photosensitive drum 1, which moves through the transfer section P5 and toward the brush contact section, is 0 to -200V. Therefore, the brush voltage is set such that at the brush contact section, the surface of the photosensitive drum 1 is on the normal polarity side of the toner, and the brush member 11 is on the abnormal polarity side of the toner. With this brush voltage setting, the toner with the normal polarity charge is attracted to the photosensitive drum 1 side, and the toner with the abnormal polarity charge is attracted to the brush member 11 side.

[0319] (The behavior of the toner at the brush contact area)

[0320] The toner that was not transferred from the photosensitive drum 1 to the sheet by the transfer roller 5 is delivered to the brush contact part by the rotation of the photosensitive drum 1. At this time, when the contact pressure of the brush contact part is high, the toner particles easily roll by friction with the brush member 11 and the surface of the photosensitive drum 1, so that the normal polarity charge is easily imparted to the residual toner.

[0321] However, when the contact pressure is too high, in the brush contact area, at locations where the contact pressure is higher than at the outer periphery, or where the bristle material density is higher than at the outer periphery, most of the toner cannot pass through these locations. Instead, the toner concentrates at locations with lower contact pressure or density. As a result, such as Figure 27 As shown in part (a), the toner T is distributed in a stripe shape through the brush contact portion. Figure 27 Part (a) shows the state of the periphery of the brush member 11 as viewed from the outer peripheral side of the photosensitive drum 1, where residual toner is represented by gray portions (dot patterns) and areas where no residual toner is deposited are represented by uncolored (colorless) portions.

[0322] Will use Figure 27 Part (b) describes the state in which the toner T is distributed in a stripe shape through the brush contact area. Figure 27 Part (b) is a schematic diagram showing a cross-section of the surface of the photosensitive drum 1 passing through the brush contact portion along the longitudinal direction. The toner T passing through the brush contact portion contains toner particles with an abnormal polarity (+). Furthermore, when the toner T passes through the brush contact portion in a stripe pattern, at the location through which the toner T passes, there is a tendency for the brush member 11 to not contact a portion of the toner particles, and for the amount of toner particles passing through the brush contact portion to increase while remaining abnormally polar and not being rubbed-charged by the brush member 11.

[0323] At the charging section P2, a charging voltage of the same polarity as the toner T is applied to the charging roller 2. Therefore, as Figure 27 As shown in part (c), the toner T of normal polarity is pressed against the surface of the photosensitive drum 1 and passes through the charging section P2 without depositing on the charging roller 2. On the other hand, for the reasons described above, when the toner of abnormal polarity reaches the charging section P2, the toner T is attracted by the charging voltage and deposited on the charging roller 2. When the toner deposited on the charging roller 2 accumulates, there is a possibility of image defects due to poor charging. Therefore, as described above, the toner passing through the brush member 11 in a striped shape causes striped contamination of the charging roller 2 by the toner, and due to poor charging that eventually occurs at a specific position of the image relative to the main scanning direction, it presents as a striped image defect.

[0324] On the other hand, in this embodiment, a structure is adopted in which the contact pressure and contact area ratio of the brush tip side of the brush contact portion is higher than that of the brush rear side of the brush contact portion. Therefore, it is possible to impart a normally polar charge to the toner T while preventing the toner T from passing through the brush member (so that the toner T is uniformly dispersed). This will be described below.

[0325] Figure 28 Part (a) is a conceptual diagram showing the contact state between the brush member 11 and the photosensitive drum 1 in this embodiment. Figure 28 Part (b) is a cross-sectional view of the surface of the photosensitive drum 1 along the longitudinal direction of the photosensitive drum 1 at the brush tip. Figure 28 Part (c) is a cross-sectional view of the surface of the photosensitive drum 1 along the longitudinal direction of the photosensitive drum 1 at the center of the brush. Figure 28 Part (d) is a cross-sectional view of the surface of the photosensitive drum 1 along the brush rear end side of the photosensitive drum 1.

[0326] like Figure 28 As shown in part (a), the contact pressure and contact area ratio at the brush tip are high, causing many toner particles to roll at the brush tip, thereby imparting a normally polar charge to the toner particles through triboelectric charging. However, the toner passing through the brush tip is concentrated in a portion relative to the longitudinal direction.

[0327] Subsequently, through the rotation of photosensitive drum 1, as... Figure 28 As shown in parts (b) and (c), as the toner moves towards the rear end of the brush through the brush contact portion, the bristle material of the brush member 11 randomly contacts the toner. Furthermore, the contact pressure and contact area are lower towards the rear end of the brush, thus allowing the toner T to move freely in the longitudinal direction. The concentration of the toner T is reduced, and the bristle material of the brush member 11 contacts the toner T uniformly, thereby allowing a large portion of the polarity of the toner T to be changed to the normal polarity. Furthermore, a brush voltage is applied to the brush member 11, causing a portion of the non-normally polarized toner T to be attracted to the brush member 11.

[0328] Therefore, according to the structure of this embodiment, while imparting a normal polarity charge to the toner T through the brush member 11, the toner T is prevented from passing through the brush member 11 in a stripe shape and the toner is evenly dispersed, thereby suppressing the occurrence of poor charging over a long period of time.

[0329] (Verification Experiment)

[0330] To verify that the construction of this embodiment can prevent poor charging, experiments were conducted to check whether poor charging occurred in several construction examples with different constructions of the brush member 11 and contact conditions different from those of the photosensitive drum 1. Table 1 presented below shows the main contact conditions and whether poor charging occurred in each construction example, and Table 2 presented below shows the detailed construction of each construction example.

[0331] The construction described as an example in this embodiment is Construction Example 1-1.

[0332] In construction examples 1-2, the ratio of contact pressure to contact area is kept approximately constant from the front end of the brush towards the rear end of the brush.

[0333] In construction examples 1-3, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush to a degree similar to that in construction example 1-1, but the bristle material of the brush member 11 is coarser and has a lower density compared to construction example 1-1.

[0334] In construction examples 1-4, the contact pressure and contact area ratio decrease from the brush tip side to the brush rear side to a degree similar to that in construction example 1-1, but the density of the bristle material of the brush member 11 is higher than that in construction example 1-1.

[0335] In construction examples 1-5, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush to a degree similar to that in construction example 1-1, but the short side width of the brush member 11 is narrower than that in construction example 1-1.

[0336] In construction examples 1-6, the ratio of contact pressure to contact area decreases from the front end of the brush towards the rear end of the brush, but the change in the ratio of contact pressure to contact area is smaller compared to construction example 1-1.

[0337] In construction examples 1-7, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush to a degree similar to that in construction example 1-1, but the short side width of the brush member 11 is an intermediate value between the short side widths in construction examples 1-1 and 1-5.

[0338] In construction examples 1-8, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush, and their changes are intermediate values ​​between those in construction examples 1-1 and 1-6.

[0339] The experimental environment was a low-temperature, low-humidity environment (15℃ / 10%RH). In the experiment, images with a print ratio (coating ratio, image ratio) of 3% were intermittently output onto two sheets, and images were output on 10,000 sheets. Then, a pure white sample image was output. At this point, the presence of black dots (dot-like image defects) was checked. In Table 1, the observation of black dots indicates poor charging ("YES"), and the absence of black dots indicates no poor charging ("NO"). Incidentally, the change in contact pressure is the difference between the contact pressure at the brush tip and the contact pressure at the brush tip.

[0340] The change in the contact area ratio is the difference between the contact area ratio at the brush tip and the contact area ratio at the brush back. Additionally, constructions not specifically mentioned in construction examples (“CNS.EXS.”) 1-2 to 1-8 are the same as those in construction example (“CNS.EXS.”) 1-1.

[0341] Table 1

[0342]

[0343] *1: "PP" is the peak pressure.

[0344] *2: “MCAR” is the maximum contact area ratio.

[0345] *3: "CPCA" is the contact pressure change.

[0346] *4: "CARCA" is the change in contact area ratio. *5: "SW" is the width of the shorter side.

[0347] *6: "IC" indicates poor charging.

[0348] Table 2

[0349]

[0350] *1: "BT" refers to the brush thickness.

[0351] *2: "D" stands for density.

[0352] *3: "SW" is the width of the shorter side.

[0353] *4: "MAX" is the maximum amount of intrusion.

[0354] *5: "BLE" refers to the amount of intrusion that can be performed on the front end.

[0355] *6: "MIN" is the minimum intrusion amount.

[0356] *7: "BTE" refers to the amount of intrusion that is brushed onto the backend.

[0357] *8: "CW" is the range of change in intrusion amount.

[0358] As shown in Table 1, no black spots appeared in construction examples 1-1, 1-7, and 1-8, thus confirming that poor charging can be prevented. On the other hand, poor charging occurred in construction examples 1-2 to 1-6.

[0359] In Example 1-2, where the contact pressure and contact area ratio do not decrease from the brush tip to the brush rear end, the reason for poor charging is believed to be because the contact pressure and contact area ratio are high even at the brush rear end, causing the toner to pass through the brush contact portion in a stripe pattern. Therefore, it can be understood that a structure, as in Example 1-1, where the contact pressure and contact area ratio decreases from the brush tip to the brush rear end, is effective in preventing poor charging.

[0360] Furthermore, charging failure occurred in construction examples 1-6 where the changes in contact pressure and contact area ratio were small, while no charging failure occurred in construction examples 1-8 where the changes in contact pressure and contact area ratio were greater than those in construction examples 1-6 but less than those in construction example 1-1. Therefore, it can be understood that a larger change in contact pressure and contact area ratio can effectively suppress the occurrence of charging failure. Specifically, a change in contact pressure of 0.6 gf / mm is preferred. 2 The above, and the change in the contact area ratio is 15% or more (preferably 18% or more in construction examples 1-8), and more preferably they are 1.0 gf / mm. 2 Above and above 30%. However, the moment of poor charging in construction examples 1-6 is later than the moment in construction examples 1-2 in which the contact pressure and contact area ratio do not decrease, so that, depending on the specific construction of the imaging device (e.g., the life setting of the charging roller 2), in some cases the occurrence of poor charging can be suppressed even in construction examples 1-6.

[0361] Specifically, the differences between Construction Examples 1-2 and 1-6 will be described. In Construction Example 1-2, the intrusion amount at the upstream and downstream ends of the brush is the same, while in Construction Example 1-6, the intrusion amount at the upstream end of the brush is greater than that at the downstream end. Therefore, in Construction Example 1-6, the contact pressure and contact area ratio at the upstream end of the brush contact is at least higher than that at the downstream end of the brush contact. Therefore, the moment of poor charging in Construction Example 1-6 is later than that in Construction Example 1-2, where the contact pressure and contact area ratio do not decrease. Thus, it can be said that Construction Example 1-6 has a certain effect in suppressing poor charging. However, according to Table 2, in both Construction Examples 1-2 and 1-6, the maximum intrusion amount is obtained near the center rather than at the upstream end of the brush, which in some cases prevents sufficient toner dispersion from the upstream end of the brush towards the rear end.

[0362] The charging failure occurs in construction examples 1-5 because the brush member 11, with its extremely short side width, cannot adequately disperse the toner at the rear end of the brush. On the other hand, in construction examples 1-7 where the short side width of the brush member 11 is 3 mm, no charging failure occurs. Therefore, it can be understood that the short side width of the brush member 11 can preferably be 3 mm or more.

[0363] In construction examples 1-3, the cause of poor charging is considered to be that the minimum contact pressure of the brush member 11 (the contact pressure at the brush rear end) is too high, causing the toner to pass through the brush member 11 in a stripe pattern. Therefore, the contact pressure at the brush rear end can preferably be 1.5 gf / mm. 2 The following (more preferably 1.4 gf / mm in construction examples 1-8)2 the following).

[0364] In construction examples 1-4, the cause of poor charging is considered to be an excessively high contact area ratio at the brush tip, causing the toner to pass through the brush member 11 in a striped pattern. Therefore, it is preferable that the contact area ratio at the brush tip is, for example, 40% or less (more preferably 32% or less in construction example 18). Furthermore, the density of the bristle material of the brush member 11, as described above, is preferably 350 kF / inch. 2 the following.

[0365] As described above, in this embodiment, a structure is adopted in which the contact pressure and contact area ratio of the brush front end side is higher than that of the brush rear end side, thereby suppressing the occurrence of poor charging over a long period of time.

[0366] (Modified Implementation)

[0367] In this embodiment, the brush member 11, having a certain bristle height, is arranged at an angle relative to the tangential direction of the photosensitive drum 1, so as to achieve a structure in which the contact pressure and contact area ratio is higher at the brush tip side than at the brush rear side. The invention is not limited to this, but a structure can be adopted that reduces the contact pressure and contact area ratio by, for example, setting a step difference in bristle height between the brush tip and the brush rear side.

[0368] <Fifth Embodiment>

[0369] In the fifth embodiment, the brush member 11 is constructed such that the bristle material density varies depending on the location, so that the contact pressure and contact area are higher at the front end of the brush than at the rear end. In the following description, elements indicated by reference numerals or symbols common to the fourth and fifth embodiments have substantially the same construction and function as in the fourth embodiment; the differences from the fourth embodiment will be primarily described.

[0370] In the brush member 11 of this embodiment, the bristle material density at the brush tip side is higher than that at the brush rear end side. In this example, a conductive wire 11a with a thickness of 2 denier is used as the bristle material, and the bristle density is 240 kF / inch from the brush tip side to the brush rear end side. 2 200kF / inch 2 and 160kF / inch 2 These three stages reduce density. In this embodiment, the short side width of the brush member 11 is 6 mm.

[0371] exist Figure 29 Each of sections (a) and (b) shows a schematic diagram of the brush member 11 as viewed from the free end of the bristle material. Figure 29Part (a) shows an embodiment in which the density of the bristle material (conductive filament 11a) decreases toward the rear end of the brush (downstream of the rotation direction R1 of the photosensitive drum 1). On the other hand, in Figure 29 In the fourth embodiment shown in part (b), the density of the bristle material (conductive filament 11a) is constant.

[0372] Therefore, in this embodiment, a structure is adopted in which the bristle material density at the first position on the brush tip side is higher than the bristle material density at the second position on the brush rear side. This embodiment is an example of a structure in which the contact pressure to contact area ratio at the first position on the brush tip side is higher than the contact pressure to contact area ratio at the second position on the brush rear side.

[0373] Similarly, in this embodiment, the Clark-Evans exponent w of the brush component 11 can ideally be w≥1.

[0374] In this embodiment, unlike the fourth embodiment, it is not necessary to arrange the brush member 11 in an inclined state relative to the photosensitive drum 1. In the example of this embodiment, in Figure 1 The condition β = 0 holds true. In this example, the intrusion amount (maximum intrusion amount) of the brush component 11 into the photosensitive drum 1 is 1 mm.

[0375] In this example, the contact pressure between the brush component 11 and the photosensitive drum 1 is 2 gf / mm at the brush tip. 2 At the brush back end, it is 1gf / mm. 2 Furthermore, the contact area is 50% at the brush tip and 20% at the brush tip.

[0376] Similarly, in this embodiment, a brush voltage is preferably applied to the brush member 11. For example, as in the fourth embodiment, the brush voltage is set to -350V.

[0377] (Verification Experiment)

[0378] To verify that the construction of this embodiment can prevent charging defects, experiments were conducted to check whether charging defects occurred in multiple construction examples with different constructions of the brush member 11 and contact conditions different from those of the photosensitive drum 1. Table 3 below shows the main contact conditions and the occurrence of charging defects in each construction example, and Table 4 below shows the detailed construction of each construction example. The experimental environment, output images, sample images, and methods for evaluating charging defects are the same for the fourth and fifth embodiments.

[0379] The construction described as an example in this embodiment is Construction Example 2-1.

[0380] In construction example 2-2, the ratio of contact pressure to contact area is kept approximately constant from the front end of the brush toward the rear end of the brush.

[0381] In construction example 2-3, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush to a degree similar to that in construction example 2-1, but the bristle material of the brush member 11 is coarser and has a lower density compared to construction example 2-1.

[0382] In construction example 2-4, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush to a degree similar to that in construction example 2-1, but the bristle material of the brush member 11 has a higher overall density compared to construction example 2-1.

[0383] In construction example 2-5, the ratio of contact pressure to contact area decreases from the front end of the brush towards the rear end of the brush, but the change in the ratio of contact pressure to contact area is small compared to construction example 2-1.

[0384] In construction example 2-6, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush, and the amount of change is an intermediate value between the amounts of change in construction examples 2-1 and 2-5.

[0385] Table 3

[0386]

[0387] *1: "PP" is the peak pressure.

[0388] *2: "MCAR" is the maximum contact area ratio.

[0389] *3: "CPCA" is the change in contact pressure.

[0390] *4: "CARCA" is the change in contact area ratio.

[0391] *5: "SW" is the width of the shorter side.

[0392] *6: "IC" indicates poor charging.

[0393] Table 4

[0394]

[0395] *1: "BT" refers to the brush thickness.

[0396] *2: "Density" is measured at the front end ("LE"), center ("CT"), and rear end ("TE").

[0397] *3: "SW" is the width of the shorter side.

[0398] *4: "MAX" is the maximum amount of intrusion.

[0399] *5: "MIN" is the minimum intrusion amount.

[0400] *6: "CW" is the range of change in the amount of intrusion.

[0401] As shown in Table 3, no black spots appeared in construction examples 2-1 and 2-6, thus confirming that poor charging can be prevented. On the other hand, poor charging occurred in construction examples 2-2 to 2-5.

[0402] In construction example 2-2, where the contact pressure and contact area ratio do not decrease from the brush tip to the brush rear end, the reason for poor charging is believed to be because the contact pressure and contact area ratio are high even on the brush rear end side, causing the toner to pass through the brush contact portion in a stripe pattern. Therefore, it can be understood that, as in construction example 2-1, a structure where the contact pressure and contact area ratio decreases from the brush tip to the brush rear end is effective in preventing poor charging.

[0403] Furthermore, charging failure occurred in construction examples 2-5 where the changes in contact pressure and contact area ratio were small, while no charging failure occurred in construction examples 2-6 where the changes in contact pressure and contact area ratio were greater than those in construction examples 2-5 but less than those in construction examples 1-1. Therefore, it can be understood that a larger change in contact pressure and contact area ratio can effectively suppress the occurrence of charging failure. Specifically, a change in contact pressure of 0.6 gf / mm is preferred. 2 The change in the contact area ratio is 15% or more, and more preferably 1.0 gf / mm². 2 Above and above 30%. However, the moment of poor charging in construction examples 2-5 is later than the moment in construction example 2-2 in which the contact pressure and contact area ratio do not decrease, so that, depending on the specific construction of the imaging device (e.g., the life setting of the charging roller 2), in some cases the occurrence of poor charging can be suppressed even in construction example 2-6.

[0404] In construction examples 2-3, the cause of poor charging is considered to be that the minimum contact pressure of the brush member 11 (the contact pressure at the brush rear end) is too high, causing the toner to pass through the brush member 11 in a stripe pattern. Therefore, the contact pressure at the brush rear end can preferably be, for example, 1.5 gf / mm. 2 the following.

[0405] In construction examples 2-4, the cause of poor charging is considered to be an excessively high contact area ratio at the brush tip, resulting in the toner passing through the brush member 11 in a stripe pattern. Therefore, it is preferable to make the contact area ratio at the brush tip, for example, 40% or less. Furthermore, the density of the bristle material at the brush tip is preferably 200 kF / inch. 2 The following is preferred: 180 kF / inch 2 the following.

[0406] As described above, similarly, the construction of this embodiment can suppress the occurrence of charging defects for a long period of time.

[0407] (Modified Implementation)

[0408] In this embodiment, the density of the bristle material of the brush member 11 is changed in three stages, but a structure that reduces the contact pressure and contact area ratio by continuously decreasing the bristle material density from the front end to the rear end of the brush can be adopted. Furthermore, the bristle material density can be reduced in two, four, or more stages.

[0409] Furthermore, similar to the fourth embodiment, the brush member 11 in this embodiment can be arranged in an inclined state relative to the photosensitive drum 1.

[0410] <Sixth Embodiment>

[0411] In the sixth embodiment, the brush member 11 is constructed such that the bristle material has a different coarseness depending on its position, so that the contact pressure and contact area are higher at the front end of the brush than at the rear end. The elements indicated by the reference numerals or symbols common to both the fourth and sixth embodiments have substantially the same construction and function as those in the fourth embodiment; the differences from the fourth embodiment will be primarily described.

[0412] In the brush member 11 of this embodiment, the bristle material at the front end of the brush is coarser than that at the rear end. In this example, a density of 240 kF / inch is used. 2 The conductive wire 11a is used as the bristle material. The thickness of the conductive wire 11a decreases in three stages of 2 denier, 1.5 denier, and 1 denier every 2 mm from the front end of the brush to the rear end. In this embodiment, the short side width of the brush member 11 is 6 mm.

[0413] exist Figure 30 Each of sections (a) and (b) shows a schematic diagram of the brush member 11 as viewed from the free end of the bristle material. Figure 30 Part (a) illustrates this embodiment, wherein the bristle material (conductive filament 11a) tapers towards the rear end of the brush (downstream of the rotation direction R1 of the photosensitive drum 1). On the other hand, in Figure 30 In the fourth embodiment shown in part (b), the thickness of the bristle material (conductive filament 11a) is constant.

[0414] Therefore, in this embodiment, the bristle material at the first position on the front end of the brush is coarser than the bristle material at the second position on the rear end of the brush. This embodiment is an example of a structure in which the contact pressure to contact area ratio at the first position on the front end of the brush is higher than the contact pressure to contact area ratio at the second position on the rear end of the brush.

[0415] Similarly, in this embodiment, the Clark-Evans exponent w of the brush component 11 can ideally be w≥1.

[0416] In this embodiment, unlike the fourth embodiment, it is not necessary to arrange the brush member 11 in an inclined state relative to the photosensitive drum 1. In the example of this embodiment, in Figure 1 The condition β = 0 holds true. In this example, the intrusion amount (maximum intrusion amount) of the brush component 11 into the photosensitive drum 1 is 1 mm.

[0417] In this example, the contact pressure between the brush component 11 and the photosensitive drum 1 is 2 gf / mm at the brush tip. 2 At the brush back end, it is 1gf / mm. 2 Furthermore, the contact area is 50% at the brush tip and 20% at the brush tip.

[0418] Similarly, in this embodiment, it is preferable to apply a brush voltage to the brush member 11. For example, similar to the fourth embodiment, the brush voltage is set to -350V.

[0419] (Verification Experiment)

[0420] To verify that the construction of this embodiment can prevent charging defects, experiments were conducted to check whether charging defects occurred in multiple construction examples with different constructions of the brush member 11 and contact conditions different from those of the photosensitive drum 1. Table 5 below shows the main contact conditions and the occurrence of charging defects in each construction example, and Table 6 below shows the detailed construction of each construction example. The experimental environment, output images, sample images, and methods for evaluating charging defects are the same for the fourth and sixth embodiments.

[0421] The construction described as an example in this embodiment is Construction Example 3-1.

[0422] In construction example 3-2, the ratio of contact pressure to contact area is kept approximately constant from the front end of the brush toward the rear end of the brush.

[0423] In construction example 3-3, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush to a degree similar to that in construction example 3-1, but the bristle material of the brush member 11 is generally coarser and has a lower density compared to construction example 3-1.

[0424] In construction example 3-4, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush to a degree similar to that in construction example 3-1, but the bristle material of the brush member 11 has a higher overall density compared to construction example 3-1.

[0425] In construction example 3-5, the ratio of contact pressure to contact area decreases from the front end of the brush towards the rear end of the brush, but the change in the ratio of contact pressure to contact area is small compared to construction example 3-1.

[0426] In construction example 3-6, the contact pressure and contact area ratio decrease from the front end of the brush towards the rear end of the brush, and the amount of change is an intermediate value between the amounts of change in construction examples 3-1 and 3-5.

[0427] Table 5

[0428]

[0429] *1: "PP" is the peak pressure.

[0430] *2: "MCAR" is the maximum contact area ratio.

[0431] *3: "CPCA" is the change in contact pressure.

[0432] *4: "CARCA" is the change in contact area ratio. *5: "SW" is the width of the shorter side.

[0433] *6: "IC" indicates poor charging.

[0434] Table 6

[0435]

[0436] *1: "BT" refers to the brush thickness at the front ("LE"), center ("CT"), and back ("TE").

[0437] *2: "Density" is measured at the front end ("LE"), center ("CT"), and rear end ("TE").

[0438] *3: "SW" is the width of the shorter side.

[0439] *4: "MAX" is the maximum amount of intrusion.

[0440] *5: "MIN" is the minimum intrusion amount.

[0441] *6: "CW" is the range of change in the amount of intrusion.

[0442] As shown in Table 5, no black spots appeared in construction examples 3-1 and 3-6, thus confirming that poor charging can be prevented. On the other hand, poor charging occurred in construction examples 3-2 to 3-5.

[0443] In construction example 3-2, where the contact pressure and contact area ratio do not decrease from the brush tip to the brush rear end, the reason for poor charging is believed to be because the contact pressure and contact area ratio are high even on the brush rear end side, causing the toner to pass through the brush contact portion in a stripe pattern. Therefore, it can be understood that, as in construction example 3-1, a structure where the contact pressure and contact area ratio decreases from the brush tip to the brush rear end is effective in preventing poor charging.

[0444] Furthermore, charging failure occurred in construction examples 3-5 where the changes in contact pressure and contact area ratio were small, while no charging failure occurred in construction example 3-6 where the changes in contact pressure and contact area ratio were greater than those in construction example 3-5 but less than those in construction example 3-1. Therefore, it can be understood that a larger change in contact pressure and contact area ratio can effectively suppress the occurrence of charging failure. Specifically, a change in contact pressure of 0.6 gf / mm is preferred. 2 The change in the contact area ratio is 15% or more, and more preferably 1.0 gf / mm². 2 Above and 30% or more. However, in construction examples 3-5, the moment of poor charging occurs later than in construction example 3-2, where the contact pressure and contact area ratio do not decrease. Therefore, depending on the specific structure of the imaging device (e.g., the lifespan setting of the charging roller 2), in some cases, even in construction example 3-6, the occurrence of poor charging can be suppressed.

[0445] In construction example 3-3, the cause of poor charging is considered to be that the minimum contact pressure of the brush member 11 (the contact pressure at the brush rear end) is too high, causing the toner to pass through the brush member 11 in a stripe pattern. Therefore, the contact pressure at the brush rear end can preferably be, for example, 1.5 gf / mm. 2 the following.

[0446] In construction examples 3-4, the cause of poor charging is considered to be an excessively high contact area ratio at the brush tip, causing the toner to pass through the brush member 11 in a stripe pattern. Therefore, it is preferable to make the contact area ratio at the brush tip, for example, 40% or less.

[0447] As described above, similarly, the construction of this embodiment can suppress the occurrence of charging defects for a long period of time.

[0448] (Modified Implementation)

[0449] In this embodiment, the bristle material thickness of the brush member 11 varies in three stages, but a structure that reduces the contact pressure and contact area ratio by continuously decreasing the bristle material thickness from the front end to the rear end of the brush can be adopted. Furthermore, the bristle material thickness can be reduced in two stages or four or more stages.

[0450] Furthermore, similar to the fourth embodiment, the brush member 11 in this embodiment can be arranged in an inclined state relative to the photosensitive drum 1.

[0451] <Seventh Embodiment>

[0452] In the seventh embodiment, the structure in which the amount of intrusion of the brush member 11 into the photosensitive drum 1 decreases from the upstream side (brush front end side) to the downstream side (brush rear end side) relative to the rotation direction of the photosensitive drum 1 will be studied, along with its detailed conditions. The elements indicated by the reference numerals or symbols common to the fourth and seventh embodiments have substantially the same structure and function as those in the fourth embodiment; the differences from the fourth embodiment will be primarily described.

[0453] When the brush component 11 is arranged at an angle relative to the photosensitive drum 1, the positional relationship between the brush component 11 and the photosensitive drum 1 is as follows: Figure 31 As shown. Figure 31 This is a schematic diagram of the brush component 11 and the photosensitive drum 1 as viewed from the direction of the rotation axis of the photosensitive drum 1.

[0454] As the brush component 11 in this embodiment, the brush component 11 described in the example of the fourth embodiment is used. That is, as... Figure 22 As shown in part (a), the bristle height L1, density, and bristle material fineness of the brush member 11 are constant. Furthermore, as... Figure 22 As shown in part (b), the brush member 11 is actually in a state of flexing along the surface of the photosensitive drum 1, but in Figure 31 In this paper, interference between the brush component and the photosensitive drum 1 is not considered, and the state of the brush material entering the photosensitive drum 1 is shown. The relationship between the intrusion amount δ of the brush component 11 into the photosensitive drum 1 will be described. Figure 31 In the diagram, the rotation axis O of the photosensitive drum 1 is the origin of the coordinate system. The coordinate axis extending parallel to the short side direction SD of the brush member 11 is the X-axis, and the coordinate axis perpendicular to the X-axis (extending in a direction parallel to the normal direction of the base fabric 11b) is the Y-axis.

[0455] At the upstream end (front end) of the brush member 11 relative to the rotation direction R1 of the photosensitive drum 1, the amount of intrusion of the brush member 11 into the imaginary circle C1 defining the surface of the photosensitive drum 1 is represented by δ1. At the downstream end (rear end) of the brush member 11 relative to the rotation direction R1, the amount of intrusion of the brush member 11 into the imaginary circle C1 is represented by δ2. At the center between the front and rear ends of the brush member 11 relative to the short side direction SD, the amount of intrusion of the brush member 11 into the imaginary circle C1 is represented by δ3. At this time, the intrusion amounts δ1, δ2, and δ3 are represented by the following (Formula 4) to (Formula 6), respectively.

[0456] (Formula 4) δ1=r×sin(90-θ1)-P

[0457] (Formula 5)δ2=r×sin(90-θ2)-P

[0458] (Formula 6) δ3=r×sin(90-θ3)-P

[0459] Here, r is the radius of the photosensitive drum 1, and P is the distance from the rotation axis O of the photosensitive drum 1 to the free end of the bristle material of the brush member 11 relative to the Y-axis. In other words, P is the length obtained by subtracting the bristle height L1 of the brush member 11 from the distance L5 from the rotation axis O to the base fabric of the brush member 11 relative to the Y-axis. The first term on the right side of (Equation 4) to (Equation 6) represents the Y-coordinate of the intersection points A1, A2, and A3 between the imaginary circle C1 and the relevant bristle materials located at the front end, rear end, and center.

[0460] Furthermore, the angles θ1, θ2, and θ3 (°) formed by the straight lines extending from the rotation axis O of the photosensitive drum 1 through the intersection points A1, A2, and A3 between the brush member 11 and the imaginary circle C1, and the relevant straight lines parallel to the Y-axis, are respectively represented by the following formulas (Formula 7) to (Formula 9).

[0461] (Formula 7) θ1 = 90 - ACOS(Q1 / r)

[0462] (Formula 8) θ2=90-ACOS(Q2 / r)

[0463] (Formula 9) θ3 = 90 - ACOS(Q3 / r)

[0464] Here, Q1 is the distance from the rotation axis O to the front end of the brush member 11 in the X-axis direction. Q2 is the distance from the rotation axis O to the rear end of the brush member 11 in the X-axis direction. Q3 is the distance from the rotation axis O to the center of the brush member 11 in the X-axis direction. That is, Q3 = (Q1 + Q2) / 2 holds true. Furthermore, when the width of the shorter side (side) of the brush member 11 is L3, Q2 = Q1 + L3 and Q3 = Q1 + L3 / 2 hold true. In addition, ACOS is an inverse trigonometric function (the inverse function of cosine).

[0465] In this embodiment, the intrusion amount of the brush member 11 is δ1 = 1.6 mm at the brush tip, δ3 = 1.2 mm at the center, and δ2 = 0.45 mm at the brush rear end. That is, the configuration is such that the intrusion amount δ1 at the upstream end of the brush member 11 relative to the rotation direction R1 of the photosensitive drum 1 is greater than the intrusion amount δ2 at the downstream end of the brush member 11, and δ2 > 0. Furthermore, the radius r of the photosensitive drum 1 is 12 mm. Additionally, θ is the contact angle between the brush member 11 and the photosensitive drum 1. In this embodiment, the contact angle θ3 is set to 16°.

[0466] Similarly, in this embodiment, a brush voltage is preferably applied to the brush member 11. For example, similar to the fourth embodiment, the brush voltage is set to -350V. Furthermore, also in this embodiment, the Clark-Evans exponent w of the brush member 11 can ideally satisfy w≥1.

[0467] (Verification Experiment)

[0468] To verify that the construction of this embodiment can prevent charging defects, experiments were conducted to check whether charging defects occurred in several construction examples with different constructions of the brush member 11 and contact conditions different from those of the photosensitive drum 1. Table 7 presented below shows the contact conditions and the occurrence of charging defects in each construction example. The experimental environment, output images, sample images, and methods for evaluating charging defects are the same for the fourth and seventh embodiments.

[0469] The construction described as an example in this embodiment is Construction Example 4-1.

[0470] In construction example 4-2, the intrusion amount becomes constant from the front end to the rear end of the brush member 11 (δ1 = δ3 = δ2).

[0471] In construction example 4-3, the intrusion amount increases from the front end to the rear end of brush member 11 (δ1<δ3<δ2).

[0472] In construction example 4-4, the intrusion amount decreases from the front end to the rear end of the brush member 11, but the degree of reduction is more moderate compared to construction example 4-1.

[0473] The difference in the amount of intrusion between the various construction examples is set, for example, by setting the bristle height L1 to a different value in each region that trisects the short side width L3 of the brush member 11 relative to the short side direction SD (where the bristle height varies in three stages). For example, in construction example 4-3, the bristle height increases from the front end side of the brush towards the rear end side.

[0474] Table 7

[0475]

[0476] *1: "PA" represents the amount of intrusion at the front ("LE"), center ("CT"), and back ("TE").

[0477] *2: "SW" is the width of the short side.

[0478] *3: "IC" indicates a charging malfunction. "YES" indicates a charging malfunction has occurred. "NO" indicates no charging malfunction has occurred. "SL" indicates a minor charging malfunction has occurred.

[0479] As shown in Table 7, no black spots appeared in construction example 4-1, thus confirming that poor charging can be prevented. On the other hand, poor charging occurred in construction examples 4-2 and 4-3. In construction example 4-1, a slight poor charging occurred.

[0480] In construction examples 4-2 and 4-3, the intrusion amount δ2 at the brush rear end is equal to or greater than δ1. The cause of poor charging in construction examples 4-2 and 4-3 is considered to be due to excessively high contact pressure or contact area at the brush rear end, causing the toner to pass through the brush member 11 in a stripe shape.

[0481] On the other hand, the reason why poor charging does not occur or only slightly occurs in construction examples 4-1 and 4-4, in which the amount of intrusion δ2 at the brush rear end is less than the amount of intrusion δ1 at the brush front end, is considered to be because the contact pressure and contact area ratio at the brush rear end is low, so the toner can be dispersed.

[0482] Furthermore, in construction example 4-4, where the ratio of the intrusion amounts δ1 and δ2 at the brush tip and brush rear end is larger than in construction example 4-1, a slight charging defect occurs. Therefore, it is preferable that the ratio of the intrusion amounts δ1 and δ2 at the brush tip and brush rear end is smaller. For example, δ2 / δ1 < 0.69 is preferred. Moreover, since a slight charging defect occurs in construction example 4-4 where the difference between the intrusion amounts δ1 and δ2 (δ1-δ2) at the brush tip and brush rear end is smaller than in construction example 4-1, the difference between δ1 and δ2 (δ1-δ2) can preferably be larger. For example, (δ1-δ2) > 0.4 is preferred.

[0483] Table 7 above shows the ratio of two intrusion amounts δ1 to δ3 at the front, center, and rear ends of the brush member 11. When each ratio is less than 1, the ratio indicates that the intrusion amount of the brush member 11 decreases from the upstream side to the downstream side relative to the rotation direction R1 of the photosensitive drum 1. In this case, the closer the ratio is to 1, the more gradual the decrease in intrusion amount (the smaller the rate of decrease), while the closer the ratio is to 0, the more rapid the decrease in intrusion amount (the greater the rate of decrease).

[0484] In construction examples 4-1 and 4-4, poor charging is suppressed, so the relationship 1>δ3 / δ1>δ2 / δ3 can preferably be maintained. This relationship means that the rate of decrease in intrusion from the brush tip to the brush center is relatively small, while the rate of decrease in intrusion from the brush center to the brush rear end is relatively large. With this construction, the toner is appropriately tribocharged at the upstream portion located at the center of the brush member 11 (where the intrusion is large), allowing the polarity of the toner to change to normal polarity. Furthermore, the intrusion is smaller at the downstream portion of the center of the brush member 11, allowing the toner to be dispersed and preventing the toner from passing through the brush member 11 in a stripe pattern.

[0485] As described above, similarly, the construction of this embodiment can suppress the occurrence of charging defects for a long period of time.

[0486] <Eighth Embodiment>

[0487] In the eighth embodiment, the condition under which the brush member 11 contacts the photosensitive drum 1 with an appropriate amount of intrusion will be investigated even when the outer diameter of the photosensitive drum 1 changes. Hereinafter, the elements indicated by the reference numerals or symbols common to the first, fourth, seventh, and eighth embodiments have substantially the same structure and function as those in the first and fourth embodiments; the differences from the first and fourth embodiments will be mainly described.

[0488] As the brush component 11 in this embodiment, the brush component 11 described in the examples of the fourth and seventh embodiments is used. That is, as... Figure 22 As shown in part (a), the bristle height L1, density, and bristle material fineness of the brush member 11 are constant. The definitions of the intrusion amount δ1 to δ3 of the brush member 11 into the photosensitive drum 1 and the definition of the contact angle θ3 of the brush member 11 are the same as those described in the fourth embodiment.

[0489] In this embodiment, the intrusion amount of the brush member 11 is fixed at the brush tip at δ1 = 1.6 mm and at the brush center at δ3 = 1.2 mm. The intrusion amount δ2 at the brush rear end is controlled by adjusting the contact angle θ3 with the photosensitive drum 1, which has a different outer diameter. The radius r of the photosensitive drum 1 studied ranges from 6 mm to 24 mm.

[0490] Furthermore, in this embodiment, it is preferable to apply a brush voltage to the brush member 11. For example, similar to the fourth embodiment, the brush voltage is set to -350V. Additionally, also in this embodiment, the Clark-Evans exponent w of the brush member 11 can ideally satisfy w≥1.

[0491] (Verification Experiment)

[0492] To verify that the construction of this embodiment can prevent charging defects, experiments were conducted to check whether charging defects occurred in multiple construction examples with different outer diameters of the photosensitive drum 1. Table 8 below shows the contact conditions and whether charging defects occurred when the intrusion amount δ3 at the brush center was fixed at 1.2 mm and the contact angle θ3 was set to 16°. Table 9 below shows the contact conditions and whether charging defects occurred when δ1 = 1.6 and δ3 = 1.2 were set by adjusting the contact angle θ3. The experimental environment, output image, sample image, and charging defect evaluation method were the same for the fourth and eighth embodiments.

[0493] Table 8

[0494]

[0495] *1: "PDR" is the radius of the photosensitive drum.

[0496] *2: "BA" means brush corner.

[0497] *3: "PA" refers to the amount of intrusion at the front ("LE"), center ("CT"), and back ("TE").

[0498] *4: "SW" is the width of the short side.

[0499] *5: "IC" indicates a charging malfunction. "YES" indicates a charging malfunction has occurred. "NO" indicates no charging malfunction has occurred. "SL" indicates a minor charging malfunction has occurred.

[0500] Table 9

[0501]

[0502] *1: "PDR" is the radius of the photosensitive drum.

[0503] *2: "BA" means brush corner.

[0504] *3: "PA" refers to the amount of intrusion at the front ("LE"), center ("CT"), and back ("TE").

[0505] *4: "SW" is the width of the short side.

[0506] *5: "IC" indicates a charging malfunction. "YES" indicates a charging malfunction has occurred. "NO" indicates no charging malfunction has occurred. "SL" indicates a minor charging malfunction has occurred.

[0507] As shown in Table 8, when the angle θ3 of the brush member 11 is fixed at 16°, poor charging occurs when the radius r of the photosensitive drum 1 is less than 10 mm, and slight poor charging occurs when the radius r is 10 mm. On the other hand, no poor charging occurs when the radius r is greater than 10 mm.

[0508] The smaller the radius r of the photosensitive drum 1, the smaller the intrusion amount δ1 at the brush tip when the brush member 11 contacts the photosensitive drum 1 under the conditions of δ3 = 1.2 mm and θ3 = 16°. Therefore, the smaller the radius r of the photosensitive drum 1, the larger the ratio (δ3 / δ1) of the intrusion amount δ3 at the brush center to the intrusion amount δ1 at the brush tip. That is, as the radius r of the photosensitive drum 1 decreases, δ3 / δ1 approaches 1, making the contact state (contact pressure, contact area ratio) at the brush center closer to the contact state at the brush tip.

[0509] When the radius r of the photosensitive drum 1 is small, it is considered that the toner is concentrated at the tip of the brush where the penetration is greater, making it difficult to eliminate the toner concentration even at the center of the brush. Furthermore, the toner cannot be sufficiently dispersed by the tip of the brush alone, causing the toner to pass through the brush member 11 in a stripe pattern. As a result, it is considered that poor charging occurs when the radius r of the photosensitive drum 1 is less than 10 mm. On the other hand, when the radius r of the photosensitive drum 1 is greater than 10 mm, δ3 / δ1 is relatively small, thus the center of the brush helps disperse the toner, making it less likely for the toner to pass through the brush member 11 in a stripe pattern and suppressing poor charging.

[0510] Therefore, it can be considered that the ratio of the intrusion amount δ3 at the center of the brush to the intrusion amount δ1 at the tip of the brush (δ3 / δ1) can preferably be set such that δ3 / δ1≤0.77, and more preferably δ3 / δ1≤0.75.

[0511] Therefore, as shown in Table 9, when the contact angle θ3 is set to satisfy δ / δ1 = 0.75 for each of the photosensitive drums 1 with different radii r, no charging failure will occur even when the radii r are 8 mm and 10 mm.

[0512] Incidentally, regarding the brush member 11 used in the verification with a short side width L3 of 4 mm, when it was desired to satisfy the relationship δ3 / δ1≤0.75 with a radius r of 6 mm for the photosensitive drum 1, the rear end of the brush floated off the surface of the photosensitive drum 1. As a result, poor charging occurred when r = 6 mm.

[0513] Furthermore, according to the results in Table 9, the ratio (δ2 / δ1) of the intrusion amount δ2 at the brush rear end to the intrusion amount δ1 at the brush front end can preferably be in the range of 0.14 ≤ δ2 / δ1 ≤ 0.38. By making the intrusion amount at the brush rear end less than the intrusion amount at the brush front end so that it falls within this range, the toner is appropriately tribocharged on the front end side of the brush member 11 while being uniformly dispersed on the rear end side of the brush member 11.

[0514] (Other embodiments)

[0515] In the above embodiments, a direct transfer type configuration was described, in which the toner image is directly transferred from the photosensitive drum 1 (image carrier) to the sheet (recording material) serving as the toner image receiving member. However, the present invention can be applied to an intermediate transfer type imaging apparatus. In the case of the intermediate transfer type, the transfer member refers, for example, a transfer roller (primary transfer roller) for transferring the toner image from the photosensitive drum 1, which serves as the image carrier, to the intermediate transfer member, which serves as the toner image receiving member, in one pass. As the intermediate transfer member, an annular belt member tensioned by multiple rollers can be used. The toner image initially transferred to the intermediate transfer member is then transferred a second time from the intermediate transfer member to the sheet (recording material) by a secondary transfer device (e.g., a secondary transfer roller) for forming a secondary transfer clamping portion between itself and the intermediate transfer member. Even in this intermediate transfer type configuration, by replacing each of the transfer rollers in the above embodiments with a primary transfer roller, effects similar to those in the above embodiments can be obtained.

[0516] Furthermore, while the above embodiments primarily describe the application of charge through triboelectric charging caused by friction between the brush member and the toner, the method of applying charge is not limited to this. For example, a configuration in which charge injection is performed to inject charge into the toner via the brush member can be employed. That is, regardless of the charge application method, the brush member may only need to concentrate the charge distribution of the residual toner after passing through the brush contact and before reaching the charging section on the normal polarity side, compared to the charge distribution of the residual toner carried on the image carrier member but before reaching the brush contact.

[0517] According to the present invention, in the configuration where the brush member contacts the image carrier member, the occurrence of poor charging can be suppressed.

[0518] Although 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 device, comprising: Rotatable image-carrying component; The developing member is configured to develop an electrostatic latent image formed on the surface of the image carrier member at the developing section using a toner; A transfer member is configured to transfer a toner image obtained by developing an electrostatic latent image by a developing member from an image carrying member to a toner image receiving member at a transfer section. and The brush contacts the surface of the image carrier member at a contact point located downstream of the transfer section and upstream of the developing section, relative to the rotational direction of the image carrier member. Toner that was not transferred to the toner image receiving component was collected by the developing component. In the charged sequence, the toner is positioned relative to the brush on the side with the same polarity as the toner's normal charge, and At the contact area, The maximum contact pressure is 0.7 gf / mm. 2 Above and 3.5 gf / mm 2 the following, The maximum contact area ratio is above 18% and below 74%, and The Clark-Evans index is above 1.

2. The imaging device according to claim 1, wherein, At the contact point, the maximum contact pressure is 1.4 gf / mm. 2 Above and 2.8 gf / mm 2 The maximum contact area ratio is between 32% and 60%.

3. The imaging device according to claim 1, further comprising: The charging component is configured to charge the surface of the image-carrying component at the charging section. The brush is arranged downstream of the transfer section and upstream of the charging section in the direction of rotation relative to the image-carrying component.

4. The imaging device according to claim 3, wherein, The charging component is a charging roller that is arranged and rotates in contact with the image carrier component at the charging section.

5. The imaging device according to claim 3, wherein, In the charged sequence, the toner is located on the same side as the normal charge polarity of the toner, relative to the surface layer material of the charging component and the surface layer material of the image carrier component.

6. The imaging apparatus according to claim 1, wherein, The brush includes a base and bristle material supported by the base, and The bristles are made of synthetic resin fibers with a denier of 1 to 6 denier and a density of 150 kF / inch. 2 above.

7. The imaging apparatus according to claim 1, wherein, The toner image receiving component is the recording material.

8. The imaging apparatus according to claim 1, wherein, The toner image receiving component is an intermediate transfer component, and The imaging device also includes a secondary transfer device configured to transfer a toner image transferred to an intermediate transfer member onto a recording material.

9. An imaging device, comprising: Rotatable image-carrying component; The developing member is configured to develop an electrostatic latent image formed on the surface of the image carrier member at the developing section using a toner; A transfer member is configured to transfer a toner image obtained by developing an electrostatic latent image by a developing member from an image carrying member to a toner image receiving member at a transfer section. The brush contacts the surface of the image carrier member at a contact point located downstream of the transfer section and upstream of the developing section in the direction of rotation relative to the image carrier member; and A voltage-applying device configured to apply voltage to a brush. Toner that was not transferred to the toner image receiving component was collected by the developing component. The voltage applied to the brush by the voltage application device is located on the same side as the normal charge polarity of the toner relative to the surface potential of the image carrier component, and At the contact area, The maximum contact pressure is 0.7 gf / mm. 2 Above and 3.5 gf / mm 2 the following, The maximum contact area ratio is above 18% and below 74%, and The Clark-Evans index is above 1.

10. The imaging apparatus according to claim 9, wherein, In the charged sequence, the toner is located on the side with the same charge polarity as the toner relative to the brush.

11. The imaging apparatus according to claim 9, wherein, At the upstream part of the contact area relative to the direction of rotation, the contact pressure is 0.7 gf / mm. 2 The contact area ratio is above 18%, and the Clark-Evans index is above 1.

12. The imaging apparatus according to claim 9, wherein, At the upstream part of the contact area relative to the direction of rotation, the ratio of contact pressure to contact area is the largest.

13. The imaging apparatus according to claim 12, wherein, The brush includes a base extending in a longitudinal direction parallel to the rotation axis of the image-carrying member and in a short-side direction perpendicular to the longitudinal direction, and includes bristle material supported by the base. When viewed along the axis of rotation, the brush is tilted relative to the image carrier, such that the downstream of the base in the direction of rotation is separated from the tangent of the image carrier.

14. An imaging device, comprising: Rotatable image-carrying component; A charging member that contacts an image carrier member to form a charging section and is configured to charge the surface of the image carrier member at the charging section; The developing member is configured to develop an electrostatic latent image formed on the surface of the image carrier member using a toner; A transfer member is configured to transfer a toner image obtained by developing an electrostatic latent image by a developing member from an image carrying member to a toner image receiving member at a transfer section. and The brush is configured to contact the surface of the image carrier member at a contact portion located downstream of the transfer section and upstream of the charging section relative to the rotational direction of the image carrier member, and is configured to charge the toner that has not been transferred to the toner image receiving member. Toner that was not transferred to the toner image receiving component was collected by the developing component. Specifically, relative to the direction of rotation, the contact pressure between the brush and the image carrier at the upstream end of the brush in the contact portion is higher than the contact pressure between the brush and the image carrier at the downstream end of the brush in the contact portion. Wherein, the contact area ratio between the brush and the image carrier component at the upstream end of the brush is greater than the contact area ratio between the brush and the image carrier component at the downstream end of the brush.

15. The imaging apparatus according to claim 14, wherein, The ratio of contact pressure to contact area decreases monotonically from the upstream end to the downstream end relative to the direction of rotation.

16. The imaging apparatus according to claim 14, wherein, The difference between the maximum and minimum contact pressure is 0.6 gf / mm. 2 Above and 1.5 gf / mm 2 The following conditions apply, and the difference between the maximum and minimum contact area ratio is more than 15% and less than 40%.

17. The imaging apparatus according to claim 14, wherein, The difference between the maximum and minimum contact pressure is 0.7 gf / mm. 2 Above and 3.5 gf / mm 2 The following conditions apply, and the difference between the maximum and minimum contact area ratio is greater than 18% and less than 74%.

18. The imaging apparatus according to claim 14, wherein, The difference between the maximum and minimum contact pressure is 1.4 gf / mm. 2 Above and 2.8 gf / mm 2 The following conditions apply, and the difference between the maximum and minimum contact area ratio is more than 32% and less than 60%.

19. The imaging apparatus according to claim 14, wherein, The brush includes a base extending in a longitudinal direction parallel to the rotation axis of the image carrier and in a short-side direction perpendicular to the longitudinal direction, and includes bristle material supported by the base and in contact with the surface of the image carrier. The brush is tilted relative to the image carrier component, such that the base is spaced apart from the image carrier component in the direction of rotation downstream.

20. The imaging apparatus according to claim 19, wherein, When viewed along the axis of rotation, the straight line passing through the axis of rotation and the center of the base relative to the shorter side is the first straight line, and The angle between the second line perpendicular to the first line and the third line extending along the base in the short side direction is 8° or more and 16° or less.

21. The imaging apparatus according to claim 14, wherein, The brush includes bristle material that contacts the surface of the image-carrying component, and The density of the bristle material at the upstream end of the brush is higher than that at the downstream end of the brush.

22. The imaging apparatus according to claim 14, wherein, The brush includes bristle material that comes into contact with the surface of the image-carrying component. Among them, the thickness of the bristles at the upstream end of the brush is greater than that at the downstream end of the brush.

23. The imaging apparatus according to claim 14, wherein, When the amount of intrusion of the brush into the surface of the image carrier component at the upstream end relative to the rotation direction is δ1 (mm) and the amount of intrusion of the brush into the surface of the image carrier component at the downstream end relative to the rotation direction is δ2 (mm), the following relationship is satisfied: δ1 > δ2 > 0.

24. The imaging apparatus according to claim 23, wherein, When the intrusion amount at the center between the upstream and downstream ends of the brush in the direction perpendicular to the rotation axis of the image-carrying component of the brush is δ3 (mm), the following relationship is satisfied: 1 > δ3 / δ1 > δ2 / δ3.

25. The imaging apparatus according to claim 24, wherein, When the radius of the image-carrying component is r (mm), within the range of r > 6, the following relationship is satisfied: 0.14 ≤ δ2 / δ1 ≤ 0.38, and δ3 / δ1 ≤ 0.

75.

26. The imaging apparatus according to claim 24, wherein, In the region from the upstream end to the downstream end of the brush, the intrusion amount decreases monotonically.

27. The imaging apparatus of claim 14, further comprising a voltage application device configured to apply a voltage of the same polarity as the normal charge polarity of the toner to the brush.

28. The imaging apparatus according to claim 27, wherein, The voltage applied to the brush by the voltage applying device is on the same side as the normal charge polarity of the toner, relative to the surface potential of the image carrier component reaching the contact portion that contacts the brush.

29. The imaging apparatus according to claim 14, wherein, In the charged sequence, the toner is located on the side with the same charge polarity as the toner relative to the brush.

30. The imaging apparatus according to claim 29, wherein, The circumferential speed of the charging component is higher than that of the image-carrying component, and In the charged sequence, the toner material relative to the surface layer of the charging component and the surface layer of the image carrier component are located on the same side as the normal charge polarity of the toner.

31. The imaging apparatus according to claim 14, wherein, At the contact point between the brush and the image-carrying component, the Clark-Evans index of the brush is greater than 1.

32. The imaging apparatus according to claim 14, wherein, The length of the brush in the short side direction perpendicular to the axis of rotation is 3 mm or more. The brush bristles are made of synthetic resin fibers with a density of 1 denier or higher and 6 denier or lower. The density of the bristle material is 150 kF / inch. 2 above.

33. The imaging apparatus according to claim 14, wherein, The toner image receiving component is the recording material.

34. The imaging apparatus according to claim 14, wherein, The toner image receiving component is an intermediate transfer component, and The imaging device also includes a secondary transfer device configured to transfer a toner image transferred to an intermediate transfer member onto a recording material.

35. An imaging device, comprising: Rotatable image-carrying component; A charging member that contacts an image carrier member to form a charging section, and is configured to charge the surface of the image carrier member at the charging section; The developing member is configured to develop an electrostatic latent image formed on the surface of the image carrier member using a toner; A transfer member is configured to transfer a toner image obtained by developing an electrostatic latent image by a developing member from an image carrying member to a toner image receiving member at a transfer section. and The brush is configured to contact the surface of the image carrier member at a contact portion located downstream of the transfer section and upstream of the charging section relative to the rotational direction of the image carrier member, and is configured to charge the toner that has not been transferred to the toner image receiving member. In this process, the toner that was not transferred onto the toner image receiving component is collected by the developing component, and Wherein, when the amount of intrusion of the brush into the surface of the image carrier component at the upstream end of the brush relative to the rotation direction is δ1 (mm) and the amount of intrusion of the brush into the surface of the image carrier component at the downstream end of the brush relative to the rotation direction is δ2 (mm), the following relationship is satisfied: δ1 > δ2 > 0.

36. The imaging apparatus according to claim 35, wherein, When the intrusion amount at the center between the upstream and downstream ends of the brush in the direction perpendicular to the rotation axis of the image-carrying component of the brush is δ3 (mm), the following relationship is satisfied: 1 > δ3 / δ1 > δ2 / δ3.

37. The imaging apparatus according to claim 36, wherein, When the radius of the image-carrying component is r (mm), within the range of r > 6, the following relationship is satisfied: 0.14 ≤ δ2 / δ1 ≤ 0.38, and δ3 / δ1 ≤ 0.75.

Images