Imaging equipment

Abstract

An imaging apparatus includes a rotatable image carrier member; a developing unit for developing an electrostatic latent image at a developing portion; a transfer unit for transferring a developer image to a recording member at a transfer portion; and a brush having a plurality of fibers that contact the image carrier member downstream of the transfer portion and upstream of the developing portion in the rotational direction of the image carrier member. The average contact pressure of each fiber of the brush on the image carrier member is less than the deposition force of developer not transferred to the recording member on the image carrier member. When the brush is viewed from its free end in a state not in contact with the image carrier member, the average number of the fibers included in a circumference with a diameter of 100 μm is greater than one.

Description

Technical Field

[0001] The present invention relates to an imaging apparatus for forming images on recording materials. Background Technology

[0002] In electrophotographic imaging apparatus using a direct transfer method, a cleaner-free method (developing and cleaning simultaneously) is known, in which toner (developer) that has not been transferred from the photosensitive drum, which serves as the image-carrying component, to the recording material and remains on the photosensitive drum is collected at the developing section into the developing apparatus and reused. In cleaner-free methods, it is necessary to reduce the possibility of foreign matter such as paper fibers and fillers (hereinafter referred to as paper dust) adhering to the photosensitive drum and potentially causing undesirable effects on subsequent imaging processes. Japanese Patent Application Publication No. (JP-A) 2000-112312 describes a method in which a brush member contacting the surface of the photosensitive drum collects paper dust from the photosensitive drum to reduce the amount of paper dust reaching the charging and developing sections located downstream of the transfer section.

[0003] When using the brush component described in the aforementioned literature, if a large amount of toner accumulates on the brush component, there is a possibility that the brush component will eject toner blocks at some point (such as when the contact state of the brush component changes or when a large potential fluctuation occurs between the brush component and the photosensitive drum). There is a possibility that the toner blocks ejected from the brush component will not be completely collected in the developing apparatus and transferred to the recording material, which can cause image defects.

[0004] Furthermore, in the configuration described in the aforementioned literature, the brush component may be able to remove larger pieces of paper dust; however, there are cases where the brush component fails to adequately remove small pieces of paper dust. Paper dust passing through the brush component can have undesirable effects on subsequent imaging processes, such as the possibility of image defects (dark spots) caused by preventing uniform charging of the photosensitive drum surface during the charging step. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide an imaging device that improves the paper dust collection performance of the brush component while reducing image defects caused by toner discharge.

[0006] 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 image carrier member at a developing portion using a developing agent; a transfer member configured to transfer a developing agent image developed by the developing member from the image carrier member to the developing member at a transfer portion; and a brush having a plurality of fibers that contact the image carrier member at a position downstream of the transfer portion and upstream of the developing portion relative to the rotation direction of the image carrier member, wherein the developing agent retained on the surface of the image carrier member is collected in the developing portion, wherein the average contact pressure of each fiber of the brush on the image carrier member is less than the deposition force of the developing agent retained on the surface of the image carrier member, and wherein when the brush is viewed from the free end side of the fibers in a state not in contact with the image carrier member, the average number of fibers included in a circumference with a diameter of 100 μm is greater than one.

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

[0008] Figure 1 This is a schematic diagram of an imaging device related to its implementation.

[0009] Figure 2 Part (a) is a schematic diagram of the brush component related to its implementation form, and Figure 2 Part (b) is an enlarged view of a portion of the brush component.

[0010] Figure 3 Part (a) is a diagram showing the brush component in a separate state related to the implementation form. Figure 3 Part (b) is a diagram showing the brush component in contact with the photosensitive drum.

[0011] Figure 4 Parts (a) and (b) are graphs showing the measurement results of the deposition force of the transfer residual toner on the photosensitive drum. Detailed Implementation

[0012] The implementations relating to this disclosure will be described in detail below with reference to the illustrations.

[0013] Figure 1 A schematic structure of an imaging device 100 is shown in relation to an example implementation of this disclosure (Embodiment 1). The imaging device 100 of this embodiment is a monochrome printer.

[0014] The imaging apparatus 100 includes a cylindrical photosensitive component, which serves as an image carrier; in other words, it is a photosensitive drum 1. Near the photosensitive drum 1, a charging roller 2 serves as a charging device, and a developing device 3 serves as a developing device. Additionally, an exposure device 4 is provided between the charging roller 2 and the developing device 3. Furthermore, a transfer roller 5, as a transfer device, makes pressure contact with the photosensitive drum 1.

[0015] The photosensitive drum 1 in this embodiment is a negatively charged organic photosensitive component. The photosensitive drum 1 includes a photosensitive layer located above an aluminum drum-shaped substrate. The photosensitive drum 1 is rotatable about an axis and is driven by a drive device (not shown) in the direction indicated by arrow A in the figure (clockwise in the figure) at a predetermined processing speed. In this embodiment, the processing speed is equal to the peripheral speed (surface movement speed) of the photosensitive drum 1.

[0016] The charging roller 2 contacts the photosensitive drum 1 with a predetermined contact pressure and forms a charging portion P1. During imaging, a predetermined charging voltage is applied to the charging roller 2 by a high-voltage charging power supply (not shown) that serves as a charging voltage source supply device, so as to uniformly charge the surface of the photosensitive drum 1 with the predetermined voltage. In this embodiment, the photosensitive drum 1 is charged with a negative polarity by the charging roller 2, and the charging potential of the photosensitive drum (the surface potential of the photosensitive drum 1 immediately after it passes through the charging portion P1, i.e., the dark portion potential) is approximately -700 [V].

[0017] The exposure device 4 in this embodiment is a laser scanner that outputs a laser beam corresponding to image data input from an external device (such as a host computer) and scans and exposes the surface of the photosensitive drum 1. Through this exposure, an electrostatic latent image (electrostatic image) corresponding to the image data is formed on the surface of the photosensitive drum 1. Incidentally, the potential of the exposed portion (bright portion potential) in this embodiment is approximately -100 [V]. Incidentally, the exposure device 4 is not limited to a laser scanner; for example, an LED array having multiple LEDs arranged along the longitudinal direction (axial direction of the cylinder) of the photosensitive drum 1 can be used.

[0018] In this embodiment, a contact development method is used as the development method. The development apparatus 3 includes a developing roller 31 as a developer carrier, a toner supply roller 32 as a developer supply device, a developer container chamber 34 containing toner, a stirring member 33 for stirring the toner in the developer container chamber 34, and a developing blade 35. The toner (developer) supplied from the developer container chamber 34 to the developing roller 31 by the toner supply roller 32 is charged to a predetermined polarity through the contact portion between the developing blades 35. Incidentally, this embodiment uses a toner having a particle size of 7 μm and a negative polarity as the normal charging polarity (normal polarity). In addition, in this embodiment, a single-component non-magnetic developer composed of toner is used as the developer; however, a two-component developer including a non-magnetic toner and a magnetic carrier can be used as the developer. Alternatively, a two-component non-magnetic contact / non-contact development method can also be used.

[0019] The electrostatic latent image formed on the photosensitive drum 1 is developed into a toner image (developer image) in the opposite portion (developing portion P2) opposite to the developing roller 31 and the photosensitive drum 1 by the toner conveyed by the developing roller 31. During imaging, a -400V developing voltage is applied to the developing roller 31 by a developing voltage power supply, which serves as a developing voltage application device. In this embodiment, the electrostatic latent image is developed using a reverse developing method. In other words, the electrostatic latent image is developed into a toner image by attaching toner with the same polarity as the charging polarity of the photosensitive drum 1 to a portion of the surface of the photosensitive drum 1 after the charging process, the charge of which is attenuated due to exposure by the exposure apparatus 4 (bright portion).

[0020] For the transfer roller 5, a material composed of an elastic member (such as sponge rubber formed by polyurethane elastomer, EPDM (ethylene-propylene-diene rubber), or NBR (nitrile rubber)) can be suitably used. The transfer roller 5 is pressed toward the photosensitive drum 1 to form a transfer portion N in which the photosensitive drum 1 and the transfer roller 5 are in pressure contact. A high-voltage power supply (not shown) for transfer, acting as a transfer voltage application device, is connected to the transfer roller 5, and a predetermined transfer voltage is applied to the transfer roller 5 at a predetermined timing. Incidentally, for example, a corona discharge transfer device can be used as a direct transfer device.

[0021] Based on the timing of the arrival of the toner image formed on the photosensitive drum 1 at the transfer section N, the transfer material S stored in the cartridge 6 is fed by the feed unit 7 and transferred to the transfer section N via the alignment roller pair 8. Incidentally, various sheet materials of different sizes and materials, including paper (such as plain paper and thick paper), plastic film, fabric, sheet materials whose surfaces have been treated (such as coated paper), and sheet materials with special shapes (such as envelopes and index paper), can be used as the transfer material S, which is a recording material. The toner image formed on the photosensitive drum 1 is transferred by the transfer roller 5 to which a transfer voltage has been applied to the transfer material S, which serves as the transfer body.

[0022] The transfer material S, to which the toner image has been transferred, is conveyed to the fixing device 9, which serves as a fixing unit. In this embodiment, the fixing device 9 employs a film heating method and includes: a fixing film 91 containing a fixing heater and a thermistor (not shown) for measuring the temperature of the fixing heater; and a pressing roller 92 for pressurizing the fixing film 91. The fixing device 9 performs the fixing process of the toner image by heating and pressing the transfer material S. The fixed transfer material S passes through the discharge roller pair 10 and is discharged outside the imaging device 100.

[0023] Between the transfer section N and the charging section P1, a pre-exposure device 12 is provided as a device to destaticate the surface potential of the photosensitive drum 1. This is done to obtain a uniform charging potential by balancing abnormal potentials in the photosensitive drum 1 after it passes through the transfer section N, thereby stabilizing the discharge in the charging section P1.

[0024] Furthermore, the residual toner that was not transferred to the transfer material S and remains in the photosensitive drum 1 is removed through the following process. The residual toner contains toner with a positive charge and toner that, although charged with a negative charge, does not contain sufficient charge. Due to discharge, the residual toner is recharged to a negative charge in the charging section P1. The residual toner recharged to a negative charge in the charging section P1 reaches the developing apparatus 3 as the photosensitive drum 1 rotates.

[0025] Here, as described above, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 1 that reaches the developing apparatus 3. The effect of the transfer residual toner reaching the developing apparatus 3 will be described separately for the exposed and unexposed portions of the photosensitive drum 1.

[0026] The residual toner adhering to the unexposed portion of the photosensitive drum 1 is transferred to the developing roller 31 in the developing apparatus 3 due to the potential difference between the unexposed portion of the photosensitive drum 1 and the developing voltage, and is then collected in the developer chamber 34. Incidentally, the toner collected in the developer chamber 34 is reused for imaging.

[0027] On the other hand, the residual toner adhering to the exposed portion of the photosensitive drum 1 is not transferred from the photosensitive drum 1 to the developing roller 31 in the developing apparatus 3; instead, the residual toner moves from the developing roller 31 to the transfer portion N together with the developed toner and is transferred to the transfer material S, and then removed from the photosensitive drum 1. Therefore, the brush member described below is different from the brush member used as a cleaning device (drum cleaner) for removing the residual toner from the photosensitive drum 1.

[0028] Furthermore, the static charge on the photosensitive drum 1 is removed by the pre-exposure device 12 after the transfer, and the residual toner is charged to a negative polarity by generating a uniform discharge during discharge, thereby stabilizing the residual toner. Therefore, there is less toner that cannot be sufficiently recharged to a negative polarity, which makes it possible to collect the residual toner in the developing device 3 more reliably.

[0029] Imaging apparatus 100 may include a control unit 70. The control unit 70 is configured with data processing means including a processor and processing circuitry (such as an FPGA and an ASIC), and processes data related to the operation of imaging apparatus 100 based on programs and user instructions. The control unit 70 performs controls, such as voltage application device control and voltage control (such as charging voltage, developing voltage, transfer voltage, and collection voltage), exposure control based on pre-exposure and image data, and control of driving components (such as a photosensitive drum and various rollers). The control unit 70 may be configured to coordinate the operation of multiple data processing means to perform these various processes.

[0030] [Paper Dust Collection Organization]

[0031] Next, the paper dust collection mechanism of this embodiment will be described.

[0032] When toner is transferred from photosensitive drum 1 to transfer material S in transfer section N, foreign matter (such as paper fibers and fillers) (in other words, paper dust) included in transfer material S can adhere to photosensitive drum 1. In the cleanerless method used in this embodiment, if the paper dust already attached to photosensitive drum 1 is not treated at all, the paper dust will be collected by developing unit 3. In this case, the paper dust will cause image defects. For example, the paper dust collected by developing unit 3 can get stuck between developing blade and developing roller 31, and the toner on developing roller 31 can be torn off, resulting in stripes in the image, or the paper dust collected by developing unit 3 can prevent toner charging.

[0033] Furthermore, when paper dust on the photosensitive drum 1 passes through the charging section P1, there is a possibility that the paper dust may prevent the charging roller 2 from charging the photosensitive drum 1, and the photosensitive drum 1 may not be fully charged. In this case, toner can adhere from the developing roller 31 to the insufficiently charged surface area of ​​the photosensitive drum 1 and can be transferred to the transfer material S in the transfer section N, thereby causing image defects with black spots. In particular, paper dust with a length of about 100 μm or more that has adhered to the photosensitive drum 1 can cause image defects with black spots of 100 μm or larger that are visible to the human eye; therefore, it is preferable to remove such paper dust from the photosensitive drum 1.

[0034] Therefore, this embodiment includes a brush component 11 as a paper dust collection component to remove paper dust that has adhered to the photosensitive drum 1. Figure 1 As indicated, the brush member 11 is positioned downstream of the transfer portion N and upstream of the charging portion P1 in the rotational direction (arrow A) of the photosensitive drum 1, so as to contact the photosensitive drum 1. In other words, in this embodiment, the brush member 11 contacts the image carrier member in the rotational direction of the image carrier member, downstream of the transfer portion N and upstream of the developing portion P2.

[0035] Figure 2 Part (a) is a schematic diagram of the brush member 11 in a standalone state, not in contact with the photosensitive drum 1, as viewed from the free end side of the brush member 11 (the free end side of the brush fiber 11a, i.e. the side in contact with the photosensitive drum 1). Figure 2 Part (b) is as Figure 2A magnified view of region A1 in part (a). In this embodiment, the plane on the free end side of the brush member 11 has a length of 5 mm in the circumferential direction (lateral direction of the brush member 11) of the photosensitive drum 1 and a length of 216 mm in the rotational axial direction (longitudinal direction of the brush member 11) of the photosensitive drum 1. Furthermore, brush fibers 11a (base material, bristle material) are implanted such that the free end sides of the brush fibers 11a are distributed substantially uniformly on the free end sides of the brush member 11. The lengths of the brush member 11 in the longitudinal and lateral directions are not limited to these lengths and can, for example, be varied according to the maximum paper feed width of the imaging device. The maximum paper feed width of the imaging device is the maximum width of the transfer material in the rotational axial direction of the photosensitive drum 1 in the transfer material that allows the imaging device to form an image (paper feed).

[0036] The brush component 11 includes brush fibers 11a (such as conductive nylon 6) as a base material for the surface of the triboelectric drum 1, a base fabric supporting the brush fibers 11a, and a support member (such as sheet metal) for bonding and fixing the base fabric. Incidentally, in addition to nylon, rayon, acrylic, and polyester can also be used as materials for the brush fibers 11a. In this embodiment, conductive brush fibers 11a are used; however, non-conductive brush fibers 11a can also be used. Furthermore, regarding the brush manufacturing method, a cloth brush or a brush made using an electrostatic flocking method can be used.

[0037] For the support member of the brush member 11, the brush power supply 13, which acts as a voltage application device, can be used during the rotation of the photosensitive drum 1. Figure 1 A -400V bias voltage (brush voltage) is applied. Because this brush voltage has the same polarity as the normal charging polarity of the toner already attached to the photosensitive drum 1, this helps the toner on the photosensitive drum 1 pass through without being collected. Preferably, the value of the brush voltage is the same polarity as the normal charging polarity of the toner relative to the surface potential of the photosensitive drum 1 over which the transfer portion N has passed. Incidentally, the configuration may be such that the brush voltage is not applied to the brush member 11.

[0038] The brush member 11 is supported by a support member and positioned in a fixed position, such that the brush member 11 is in complete contact with the photosensitive drum 1. As the photosensitive drum 1 rotates, the brush member 11 is rubbed against the surface of the photosensitive drum 1, and paper dust on the photosensitive drum 1 is collected by capturing paper dust on the photosensitive drum 1 using the brush fibers 11a of the brush member 11.

[0039] However, if the brush fiber 11a scrapes away residual toner or hazy toner from the photosensitive drum 1, toner accumulates on the brush member 11. Furthermore, when the toner accumulated on the brush member 11 is discharged into the photosensitive drum 1 and transferred from the photosensitive drum 1 to the recording material in the next transfer, image defects may occur due to toner contamination.

[0040] To prevent residual toner and hazy toner on the photosensitive drum 1 from being scraped off by the brush member 11, it is sufficient to reduce the contact pressure of each brush fiber 11a (each base material) of the brush member 11 on the photosensitive drum 1. Therefore, each brush fiber 11a of the brush member 11 can individually suppress the scraping of residual toner and hazy toner on the photosensitive drum 1. In particular, if the contact pressure of each brush fiber 11a of the brush member 11 on the photosensitive drum 1 is less than the deposition force of the residual toner and hazy toner on the photosensitive drum 1, the scraping of the residual toner and hazy toner on the photosensitive drum 1 can be more easily suppressed.

[0041] In addition, the brush component 11 is required to collect paper dust with a length of about 100 μm or more from the photosensitive drum 1, because the paper dust can cause visible image defects as described above.

[0042] In order for the brush member 11 to collect paper dust with a length of 100 μm or greater from the photosensitive drum 1, it would be sufficient to increase the possibility that the brush fibers 11a of the brush member 11 capture (contact) paper dust with a length of 100 μm on the photosensitive drum 1. In addition, it would be better if the paper dust could be scraped off from the photosensitive drum 1 and the brush fibers 11a captured by the paper dust would not be removed by the paper dust.

[0043] Figure 2 Part (b) is region A1, that is, by Figure 2 A magnified view of the rectangle surrounded by the dashed line shown in part (a). To increase the possibility of the brush fiber 11a capturing paper dust with a length of 100 μm on the photosensitive drum 1, Figure 2 It would be sufficient for more than one brush fiber 11a to exist on average within region A2 of the circle on the free end side (free end side of the base material) of the brush member 11 shown in part (b). Region A2 is a region within a circumference of 100 μm diameter. In other words, Figure 2 Part (b) is a schematic diagram of a projection of the free end of each brush fiber 11a onto a plane perpendicular to the protruding direction of the brush fiber 11a (the normal direction of the base fabric) by a parallel ray parallel to the protruding direction relative to the base fabric. In this projection diagram, when the brush member 11 is viewed from the free end side of the base material (brush fiber 11a), the average number of free ends of the brush fibers 11a positioned within a circumference of 100 μm diameter (within region A2) should be the average number of base materials included in the circumference of 100 μm diameter. Incidentally, the brush fibers 11a have a thickness; therefore, the position of the free end should be based on the center (plane center) of the free end.

[0044] In this manner, if there is an average of more than one brush fiber 11a within a 100μm diameter circumference on the free end side (free end side of the base material) of the brush member 11, then the multiple brush fibers 11a of the brush member 11 will come into contact with paper dust with a length of 100μm on the photosensitive drum 1. Therefore, the multiple brush fibers 11a capture paper dust with a length of 100μm on the photosensitive drum 1.

[0045] Furthermore, it is preferable that multiple brush fibers 11a are present on average within a circumference with a diameter of 100 μm. Therefore, paper dust can be scraped off by the combined force of the multiple brush fibers 11a, making it easier for the brush member 11 to scrape off paper dust with a length of 100 μm from the photosensitive drum 1.

[0046] This embodiment has the configuration of the brush member 11 indicated in Table 1; therefore, the contact pressure f1, which is the average contact pressure of each brush fiber 11a against the photosensitive drum 1, is approximately 0.98 (nN). Furthermore, the contact pressure f2, which is the product of the average number of brush fibers 11a present in a 100 μm diameter circumference on the free end side (free end side of the base material) of the brush member 11 and the contact pressure f1, is set to approximately 2.85 (nN).

[0047] [Table 1]

[0048]

[0049] Next, each item in Table 1 will be described.

[0050] The fiber length L1 in Table 1 is as follows: Figure 3 Part (a) shows the length (basic length) of the brush fiber 11a when the brush member 11 is in a stand-alone state and not in contact with the photosensitive drum 1, etc. The entry amount L3 in Table 1 indicates the depth to which the base member 11 contacts the photosensitive drum 1. Figure 3 Part (b) is a schematic diagram of the brush member 11 in contact with the photosensitive drum 1. The entry amount L3 is defined as the difference between the fiber length L1 and the distance L2 when the brush member 11 is in a standby state. The distance L2 is the distance from the fixed bearing surface of the base fabric on the support member 11c to the surface of the photosensitive drum 1, as measured in the protruding direction of the brush fiber 11a toward the base fabric (the normal direction of the base fabric).

[0051] The fineness in Table 1 is an indicator of the coarseness of brush fibers 11a, and denier is a unit of weight (g) per 9,000 meters of brush fiber. Fineness indicates that if brush fibers 11a are made of the same material, brush fibers 11a become coarser as the fineness increases.

[0052] The density indicators in Table 1 are set on the brush fibers 11a (e.g., ...) on the contact surface of the brush member 11 that contacts the photosensitive drum 1. Figure 2 The density shown is (F / inch)2 1 kf / inch is a unit indicating the number of brush fibers (11a) per square inch. Incidentally, 1 kf / inch... 2 This indicates a density of 1,000 brush fibers 11a per square inch. Additionally, 1 inch... 2 It is approximately 645mm 2 Therefore, the density of the number of brush fibers 11a per square millimeter can be obtained by dividing the density values ​​in Table 1 by 645.

[0053] The brush contact pressure in Table 1 is the contact pressure of the brush member 11 on the photosensitive drum 1 when only a predetermined amount of the brush member 11 penetrates into the photosensitive drum 1. In this embodiment, the brush contact pressure is measured using an EZ-S device manufactured by Shimazu Corporation that only allows a predetermined amount of the brush member 11 to penetrate into the photosensitive drum 1.

[0054] The contact pressure f1 in Table 1 is the average contact pressure of each brush fiber 11a of the brush member 11 against the photosensitive drum 1, as described above. The contact pressure f1 is determined based on the density of the brush fibers 11a of the brush member 11 (kF / inch). 2 The total number of brush fibers 11a in the brush component 11 is calculated by dividing the total number by the brush contact pressure.

[0055] For the configuration of brush member 11 in this embodiment, the brush density is 240 (kF / inch). 2 The value is converted to approximately 372 (brush fibers / mm²). For this reason, the contact pressure is calculated as: Contact pressure f1 = 392 (N) / {372 (brush fibers / mm²) × width 5 (mm) × length 216 (mm)} ≒ 0.98 (nN).

[0056] The contact pressure f2 in Table 1 will be included as described above. Figure 2 The average number of brush fibers 11a in a 100 μm diameter circumference on the free end side (free end side of the base material) of the brush member 11 indicated in the middle is obtained by multiplying the contact pressure f1.

[0057] For the configuration of the brush member 11 in this embodiment, the average number of brush fibers 11a of the brush member 11 including a circumference with a diameter of 100 μm can be calculated by multiplying 372 (brush fibers / square millimeter) as the brush density by the area of ​​the circle with a diameter of 100 μm. Specifically, the contact pressure f2 is calculated as: Contact pressure f2 = f1 (nN) × 372 (brush fibers / square millimeter) × π × (50 μm) × (50 μm) ÷ 10^6 ≒ 2.85 (nN).

[0058] (Verification Method)

[0059] The following experiments were conducted to verify the paper dust collection efficiency of the brush component 11 in this embodiment and the suppression of toner malfunctions caused by the accumulation of residual toner and misty toner on the photosensitive drum 1 in the brush component 11.

[0060] For each embodiment and each comparative example configuration, CenturyStar paper was used for the transfer material S to print 5,000 jobs, with each job printing 10 pages; in other words, 50,000 pages were printed.

[0061] The dust collection rate is determined by confirming the frequency of occurrence of black spots with a diameter of 0.1 mm or larger on the transfer material S after printing. Some black spots with a diameter of 0.1 mm or larger occur due to paper dust passing through the brush member 11; therefore, it can be determined that the dust collection rate of the brush member 11 increases as the frequency of black spot occurrence decreases.

[0062] Furthermore, toner malfunctions are determined by confirming the frequency of toner smudging on the transfer material S after printing. Toner smudging occurs when toner discharged from the brush member 11 is transferred onto the transfer material S; therefore, it can be determined that as the frequency of toner smudging decreases, the brush member 11 causes fewer toner malfunctions. In Table 1, if no black spots occur, the paper dust collection rate is indicated as ◎ (good); if no black spots occur most of the time, it is indicated as ○ (acceptable); if black spots occur occasionally, it is indicated as △ (unacceptable); and if black spots occur frequently, it is indicated as × (poor). Incidentally, since the number of pages printed per task is typically 10 pages or less, the number of pages printed per task is 10 pages according to the inventor's inspection.

[0063] Furthermore, for the imaging apparatus in this embodiment, the deposition force of the residual toner attached to the photosensitive drum 1 is measured twice: once at the beginning of the experiment and once after the experiment. The measurement of the deposition force of the residual toner on the photosensitive drum 1 is based on the acceleration of the residual toner that flies out of the photosensitive drum 1 after the photosensitive drum 1 has been vibrated to apply a predetermined acceleration to the residual toner on the photosensitive drum 1. In other words, the deposition force of the toner particles of the residual toner on the photosensitive drum 1 should be the product of the acceleration of the toner particles when they fly out of the photosensitive drum 1 and the average mass of each toner particle.

[0064] Furthermore, the same experiments were conducted for the cases in Examples 2 to 7 and Comparative Examples 1 to 4 shown in Table 1 where the brush member 11 was used. For each embodiment and comparative example of the imaging device, the configuration of the imaging device was the same as in Example 1, except for the configuration of the brush member 11; therefore, the description will be omitted.

[0065] (result)

[0066] As shown in Table 1, we can see that in the configuration of the brush component 11 in Examples 1 to 7, the brush component 11 has a high paper dust collection degree and can prevent image defects caused by hazy toner and transfer residue toner.

[0067] This is believed to be because, in each of the configurations in Examples 1 to 7, the contact pressure f1 of each brush fiber 11a as a brush member 11 to the photosensitive drum 1 is generally less than the deposition force of the transfer residue toner on the photosensitive drum 1. If the deposition force of the contact pressure f1 of each brush fiber 11a is less than the deposition force of the toner, the transfer residue toner and hazy toner on the photosensitive drum 1 can be more easily scraped off from the photosensitive drum 1 by the brush fibers 11a.

[0068] In other words, less toner passes through the brush member 11 while brush fibers 11a are being removed. For this reason, it is believed that less toner accumulates on the brush member 11, and image defects caused by toner discharge occur less frequently.

[0069] Figure 4 Parts (a) and (b) show the measurement results of the deposition force of the transfer residual toner on the photosensitive drum 1, measured at the beginning and after the experiment. The horizontal axis represents the number of transfer residual toners whose deposition force was measured, while the vertical axis represents the measurement result of the deposition force of each transfer residual toner on the photosensitive drum 1. Figure 4 As can be seen from parts (a) and (b), at the beginning of the experiment and after the experiment, we can see that a small amount of residual toner on the photosensitive drum 1 has a deposition force of less than 2 (nN) on the photosensitive drum 1, and almost no residual toner on the photosensitive drum 1 has a deposition force of less than 1 (nN).

[0070] Therefore, in the configurations of Examples 1 to 7, the contact pressure f1 is less than the deposition force on the photosensitive drum 1 for most of the transfer residual toner on the photosensitive drum 1. For this reason, the transfer residual toner on the photosensitive drum 1 can pass through the brush member 11 without being scraped off by the brush fibers 11a, and it is assumed that no image defects due to toner discharge will occur.

[0071] Conversely, in the configurations of Comparative Examples 1 to 4, the contact pressure f1 is greater than the deposition force of some residual toner on the photosensitive drum 1. For this reason, we can see that image defects occur as the brush fibers 11a of the brush member 11 scrape away the residual toner on the photosensitive drum 1.

[0072] Here, the deposition force of each toner particle of the residual toner on the photosensitive drum 1 varies depending on conditions such as the mass and charge of the toner particles. Therefore, if the contact pressure f1 of each brush fiber 11a is less than the lower 15% (15 / 100th percentile) of the distribution of the deposition force of the residual toner on the photosensitive drum 1, then the contact pressure f1 should be less than the deposition force of the residual toner. On the other hand, if the contact pressure f1 of each brush fiber 11a is equal to or greater than the lower 15% (15 / 100th percentile) of the distribution of the deposition force of the residual toner on the photosensitive drum 1, then the contact pressure f1 should be equal to or greater than the deposition force of the residual toner. The distribution of the deposition force of the residual toner on the photosensitive drum 1 is the distribution of deposition force measured at the beginning of the experiment and after the end of the experiment using the experimental and measurement methods described above.

[0073] The contact pressure f1 in Example 4, which has the highest contact pressure f1 among Examples 1 to 7, is 2.27 nN, and the contact pressure f1 in Comparative Example 4, which has the highest contact pressure f1 among Comparative Examples 1 to 4, is 2.81 nN. Furthermore, for in Figure 4 The two measurement results shown in parts (a) and (b) indicate that among the 60 toner particles targeted for measurement, 5 toner particles had a deposition force of 2.27 nN (5 / 60 ≒ 8.3%) or less on the photosensitive drum 1; and 11 toner particles had a deposition force of 2.81 nN (11 / 60 ≒ 18.3%) or less on the photosensitive drum 1.

[0074] Therefore, using the above standard, if the contact pressure f1 of each brush fiber 11a is less than the deposition force of the transfer residual toner on the photosensitive drum 1, we can see that the occurrence of image defects caused by the brush fiber 11a scraping off the transfer residual toner on the photosensitive drum 1 and subsequently expelling the toner block can be suppressed.

[0075] Furthermore, as can be seen from the evaluation of the toner discharge properties of Examples 1 to 7, in order to reduce image defects caused by toner discharge from the brush member 11, a contact pressure f1 of 2.3 nN or less is preferred. Additionally, in order to reduce image defects caused by toner discharge from the brush member 11, a contact pressure f1 of 1.2 nN or less is preferred.

[0076] Next, the paper dust collection efficiency will be described. The high paper dust collection efficiency indicated by the configurations in Examples 1 to 7 is due to the presence of multiple brush fibers 11a within a 100 μm diameter circumference on the free end side (free end side of the base material) of the brush member 11. In other words, in Examples 1 to 7, it is considered that paper dust with a length of 100 μm or greater on the photosensitive drum 1 is more reliably collected by the brush member 11 because the paper dust is captured by the multiple brush fibers 11a.

[0077] Furthermore, as can be seen from the evaluation of the higher dust collection efficiency of Examples 1 to 7, in order to achieve a higher dust collection efficiency, it is preferable that the contact pressure f1 in a circumference with a diameter of 100 μm is 1.9 nN or greater; furthermore, it is more preferable that the contact pressure f2 is 2.8 nN or greater.

[0078] Furthermore, the greater the average number of brush fibers 11a within a 100 μm diameter circumference, the more reliably paper dust that could cause visible image defects could be prevented from passing through. If the average number of brush fibers 11a within a 100 μm diameter circumference in Table 1 is 2.4, the assessment of paper dust collection efficiency is inconsistent; however, generally speaking, favorable results regarding paper dust collection efficiency are obtained if the average number of brush fibers is 2.4 or more. More preferably, the average number of brush fibers 11a within a 100 μm diameter circumference is 2.9 or more.

[0079] As described above, in this embodiment, the contact pressure f1, which is the average contact pressure of each brush fiber 11a on the photosensitive drum 1, is less than the deposition force of the residual toner on the photosensitive drum 1. Furthermore, in this embodiment, multiple brush fibers 11a exist within a 100 μm diameter circumference on the free end side (free end side of the base material) of the brush member 11. With this configuration, both improved paper dust collection performance of the brush member 11 and reduced image defects caused by toner discharge can be achieved.

[0080] The examples described above use a monochrome printer; however, this technology can also be applied to color printers using a direct transfer method. A color printer using a direct transfer method is, for example, an imaging device equipped with multiple processing units, each of which includes an image-bearing member (photosensitive drum) arranged along a transport path of the recording material. In this case, a color image is formed on the recording material by sequentially transferring toner images of each color formed in each processing unit onto the recording material.

[0081] Furthermore, the above implementation describes a direct transfer method that directly transfers the toner image from the photosensitive drum 1 (image carrier) to the transfer material (recording material) that serves as the transfer body. However, this technology can also be applied to imaging devices using an intermediate transfer method. In the intermediate transfer method, the transfer carrier is, for example, a transfer roller (primary transfer roller), which transfers the toner image from the photosensitive drum 1 (image carrier) to the intermediate transfer body (transfer body) in one pass. For the intermediate transfer body, an annular belt of a belt member extending across multiple rollers can be used. The toner image transferred to the intermediate transfer body in one pass is then transferred a second time from the intermediate transfer body to the sheet (recording material) via an intermediate transfer method (such as a secondary transfer roller forming a secondary transfer clamping portion between the intermediate transfer bodies). In this configuration of the intermediate transfer method, the same effect as the above implementation can be obtained by replacing the transfer roller in the above implementation with a primary transfer roller.

[0082] According to the present invention, both the paper dust collection performance of the brush component and the image defects caused by toner discharge can be improved.

[0083] 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 appended claims is to be given the broadest interpretation in order to cover all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus comprising: a rotatable image bearing member; a developing member configured to develop an electrostatic latent image formed on the image bearing member with a developer at a developing portion; a transfer member configured to transfer a developer image developed by the developing member from the image bearing member to a developing member at a transfer portion; and a brush provided with a plurality of fibers that contact the image bearing member at a position downstream of the transfer portion and upstream of the developing portion with respect to a direction of rotation of the image bearing member, wherein developer remaining on a surface of the image bearing member is collected in the developing portion, wherein an average contact pressure of each fiber of the brush against the image bearing member is less than a depositing force of the developer remaining on the surface of the image bearing member, and wherein, when the brush in a state not in contact with the image bearing member is viewed from a free end side of the fibers, an average number of fibers included in a circumference of 100 pm in diameter is greater than one.

2. The image forming apparatus according to claim 1, wherein the average contact pressure is equal to or greater than 2.3 nN.

3. The image forming apparatus according to claim 1, wherein the average contact pressure is equal to or greater than 1.2 nN.

4. The image forming apparatus according to claim 1, wherein a product of the average contact pressure and the average number is equal to or greater than 1.9 nN.

5. The image forming apparatus according to claim 1, wherein a product of the average contact pressure and the average number is equal to or greater than 2.8 nN.

6. The image forming apparatus according to claim 1, wherein the average number is equal to or greater than or greater than 2.

4.

7. The image forming apparatus according to claim 1, wherein the fibers of the brush have an electrical conductivity, and the image forming apparatus further comprises a voltage applying member configured to apply a voltage to the brush, the voltage having a same polarity with respect to a surface potential of the image bearing member passing through the transfer portion as a normal charging polarity of the developer.

8. The image forming apparatus according to claim 1, wherein a transfer material is a recording material.

9. The image forming apparatus according to claim 1, wherein the transfer member is an intermediate transfer member, and the image forming apparatus further comprises a secondary transfer member configured to transfer a toner image transferred on the intermediate transfer member to a recording material. a charging member configured to charge a surface of the image bearing member, 10. The imaging device of claim 1, further comprising: wherein the charging member charges the surface of the image bearing member by contacting the surface of the image bearing member. ​ 11. The imaging device of claim 1, wherein a density of the fibers of the brush is equal to or greater than 120 kF / inch 2 .

12. The imaging device of claim 1, wherein a density of the fibers of the brush is equal to or greater than 240 kF / inch 2 .

Images