Image forming apparatus

Abstract

An image forming apparatus is disclosed. The image forming apparatus controls a number of rotations of a photosensitive drum based on usage history information about the photosensitive drum and a suspension time after a rotation operation of rotating the photosensitive drum after a suspension time between a first image forming operation of forming an image on a transfer material and a second image forming operation performed after the first image forming operation.

Description

[0001] This application is a divisional application of the application for patent application number 202210696764.3, filed on June 20, 2022, with the title of “Image forming apparatus”. TECHNICAL FIELD

[0002] The present application relates to an image forming apparatus using an electrophotographic recording method, such as a laser printer, a copier, and a facsimile. BACKGROUND

[0003] An electrophotographic image forming apparatus uniformly charges a photosensitive drum serving as an image bearing member, and then exposes the photosensitive drum based on an image pattern to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image on the photosensitive drum is then developed and visualized with toner, and the resulting image is transferred onto a recording material such as a sheet. Then, residual toner that is not transferred on the photosensitive drum is removed from the photosensitive drum and recycled. Although various cleaning methods for removing the residual toner that is not transferred are known, a method using a brush is widely known as an effective method.

[0004] Japanese Patent Application Laid-Open No. 2007-65580 discusses a structure having a brush for cleaning toner on a photosensitive drum, and the brush is located upstream of a charging unit and downstream of a transfer unit in a moving direction of the photosensitive drum. According to this document, in a case where image formation is interrupted, for example, due to jamming, the brush is charged to a predetermined polarity to prevent the residual toner on the photosensitive drum from being deposited on the brush and maintain the cleaning performance.

[0005] However, the technology discussed in Japanese Patent Application Laid-Open No. 2007-65580 has the following problem. Specifically, in a case where a recording material is fed through the image forming apparatus having the brush disclosed in Japanese Patent Application Laid-Open No. 2007-65580, moisture in the image forming apparatus adheres to the brush. As time elapses from the interruption, the moisture accumulated on the brush gathers on the surface of the photosensitive drum, forming many water droplets. In a case where the next image forming operation is performed in this state, the many water droplets on the brush move onto the photosensitive drum. This changes the state of the surface of the photosensitive drum, and in some cases, causes image defects. For example, the many water droplets on the photosensitive drum attract toner at a developing abutment portion that is a contact portion between the photosensitive drum and a developing member, and this sometimes causes toner contamination. SUMMARY

[0006] The present application is directed to reducing image defects caused by toner contamination originating from water droplets on a brush.

[0007] An image forming apparatus includes a photosensitive drum that rotates; a charging member configured to charge a surface of the photosensitive drum at a charging portion; a developing member configured to supply toner onto the surface of the photosensitive drum charged by the charging member and form a toner image on the photosensitive drum; a transfer member configured to contact the photosensitive drum to form a transfer portion and transfer the toner image formed on the photosensitive drum to a transfer material at the transfer portion; a brush member that contacts the surface of the photosensitive drum at a position downstream of the transfer portion and upstream of the charging portion in a rotation direction of the photosensitive drum; a driving unit configured to rotate the photosensitive drum; a storage unit configured to store information about use of the photosensitive drum; and a control unit configured to control the driving unit, wherein the control unit controls a rotation operation of rotating the photosensitive drum so that the rotation operation is performed after a suspension time between a first image forming operation in which an image is formed on the transfer material and a second image forming operation performed after the first image forming operation, and before the second image forming operation is performed, and wherein the control unit controls a number of rotations of the photosensitive drum in the rotation operation based on the information and the suspension time.

[0008] Further features of the present application will become apparent from the following description of example embodiments with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a view illustrating an image forming apparatus according to a first example embodiment.

[0010] Figure 2A and Figure 2B is a view illustrating a brush member according to the first example embodiment.

[0011] Figure 3 is a control block diagram according to the first example embodiment.

[0012] Figure 4A , Figure 4B and Figure 4C is a view illustrating a state of moisture attached to the brush member during an image output operation according to the first example embodiment.

[0013] Figure 5A , Figure 5B and Figure 5C are views illustrating a state of a portion around the photosensitive drum during an image output operation according to the first example embodiment.

[0014] Figure 6 is a table illustrating an extension time of a pre-rotation process according to the first example embodiment.

[0015] Figure 7 FIG. 13 is a table illustrating toner contamination results according to a first exemplary embodiment.

[0016] Figure 8 FIG. 14 is a timing chart illustrating a pre-rotation process according to the first exemplary embodiment.

[0017] Figure 9 FIG. 15 is a view illustrating toner and moisture on a brush member according to the first exemplary embodiment.

[0018] Figure 10 FIG. 16 is a table illustrating an extended time of a pre-rotation process according to a second exemplary embodiment.

[0019] Figure 11A Figure 11B FIG. 17 is a view illustrating a process of measuring a water absorption amount of a brush member according to a fourth exemplary embodiment.

[0020] Figure 12 FIG. 18 is a view illustrating a state of a portion around a photosensitive drum during an image forming process according to a fifth exemplary embodiment.

[0021] Figure 13 FIG. 19 is a view illustrating a state of toner first recovered by a brush member according to the fifth exemplary embodiment. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present application will be described below in detail with reference to the accompanying drawings based on examples. It should be noted that the size, material, shape, and relative positions of the components described in the exemplary embodiments will be appropriately changed depending on the structure and various conditions of the apparatus to which the present application is applied. In other words, the scope of the present application is not limited to the exemplary embodiments described below.

[0023] 1. Image forming apparatus

[0024] Figure 1 FIG. 1 is a schematic view illustrating a structure of an image forming apparatus 100 according to a first exemplary embodiment.

[0025] The image forming apparatus 100 according to the present exemplary embodiment is a monochrome laser beam printer using a cleanerless method and a contact charging method. The image forming apparatus 100 includes a photosensitive drum 1. The photosensitive drum 1 is a drum-shaped (cylindrical) electrophotographic photosensitive member serving as a rotatable image bearing member. When an image output operation is started, the photosensitive drum 1 is driven by a driving motor (driving unit) of a driving unit 110 ( Figure 3 ) and rotates in the direction of an arrow R1 in Figure 1 . The outer diameter of the photosensitive drum 1 is 24 mm, and the peripheral speed (surface speed) of the photosensitive drum 1 is 140 mm / sec. ​

[0026] The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a normal polarity (negative polarity according to the present exemplary embodiment) by the charging roller 2 in the vicinity of a charging portion a at which the photosensitive drum 1 and the charging roller 2 contact each other. The charging roller 2 is a roller type charging member that is a charging unit. More specifically, the surface of the photosensitive drum 1 is charged by discharge occurring in at least one of minute spaces between the charging roller 2 and the photosensitive drum 1 formed upstream and downstream of a contact portion of the photosensitive drum 1 in a rotation direction of the photosensitive drum 1 that contacts the photosensitive drum 1. In the present exemplary embodiment, the abutting portion of the charging roller 2 and the photosensitive drum 1 in the rotation direction of the photosensitive drum 1 will be described as the charging portion a.

[0027] The charging roller 2 is an elastic roller that includes an electrically conductive elastic layer around a core metal. The charging roller 2 is disposed in contact with the photosensitive drum 1 and is driven and rotated in the direction of the arrow R2 in FIG. 1 by a drive motor (not shown). Figure 1

[0028] Although the charging roller 2 is driven and rotated according to the present exemplary embodiment, the charging roller 2 can be rotated by rotation of the photosensitive drum 1. A charging power source E1 (to be described later) that functions as a charging voltage application unit applies a predetermined charging voltage to the charging roller 2. Figure 3 The predetermined charging voltage is a direct current voltage of a negative polarity. According to the present exemplary embodiment, a direct current voltage of a negative polarity as a charging voltage is applied to the charging roller 2 during a charging process. An example of the charging voltage according to the present exemplary embodiment is -1200 V. Thus, according to the present exemplary embodiment, the surface of the photosensitive drum 1 is uniformly charged to a dark area potential Vd of -600 V.

[0029] The charged surface of the photosensitive drum 1 is scanned and exposed by a laser beam L modulated based on image data by an exposure device (laser exposure unit) 4 that is an exposure unit (electrostatic image forming unit). The exposure device 4 forms an electrostatic latent image on the photosensitive drum 1 by repeatedly exposing the photosensitive drum 1 with the laser beam L in a main scanning direction (rotation axis direction) while also performing exposure in a sub-scanning direction (surface movement direction). According to the present exemplary embodiment, the absolute value of the dark area potential Vd of the surface of the photosensitive drum 1 formed by uniform charging is reduced to a light area potential Vl of -100 V due to exposure by the exposure device 4. The position on the photosensitive drum 1 in the rotation direction of the photosensitive drum 1 that is exposed by the exposure device 4 is an image exposure portion b. The exposure device 4 is not limited to a laser scanner device. For example, an LED array having a plurality of light emitting diodes (LEDs) arranged along the length direction of the photosensitive drum 1 can be used.

[0030] ​The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) into a toner image using toner as a developer by a developing device 3 serving as a developing unit. The toner as a developer according to the present exemplary embodiment is a spherical non-magnetic toner having an average particle diameter of 6.4 μm and an average circularity of 0.98. The non-magnetic toner used in the present exemplary embodiment desirably has a high average circularity, specifically 0.96 or more. The average circularity according to the present exemplary embodiment is used as a simple way of quantitatively expressing particle shape. The particle shape is measured using a flow-type particle image analyzer FPIA-2100 manufactured by TOA Medical Electronics Co., Ltd., and the circularity is calculated using the following formula (1).

[0031]

[0032] In addition, as expressed by the following formula (2), the average circularity is defined as a value obtained by dividing the sum of the measured circularities of all the particles by the total number of the particles.

[0033]

[0034] The developing device 3 includes a developing roller 31 serving as a developer bearing member, a toner supply roller 32 serving as a developer supply unit, a developer storage chamber 33 storing toner, and a developing blade 34. The toner stored in the developer storage chamber 33 is agitated by an agitation member 35 and supplied to the surface of the developing roller 31 by the toner supply roller 32. The toner supplied to the surface of the developing roller 31 is transported by the contact portion of the developing roller 31 with the developing blade 34. Thus, the toner is shaped into a uniform thin layer and charged to a negative polarity by triboelectric charging. Although a single-component non-magnetic contact developing method is used in the present exemplary embodiment, the method is not limited thereto, and a two-component non-magnetic contact method or a non-contact developing method can also be used. In addition, a magnetic developing method can be used. In addition, although the normal polarity of the toner is a negative polarity according to the present exemplary embodiment, the normal polarity is not limited to the negative polarity. The normal polarity can be a positive polarity, and in this case, the voltage relationship described below is appropriately reversed to the opposite polarity. The developing roller 31 is counterclockwise-rotated and driven in the direction of the arrow R3 in FIG. 1 by a drive motor 110, so that the surface of the photosensitive drum 1 and the surface of the developing roller 31 move in the same direction at a developing portion c at which the photosensitive drum 1 and the developing roller 31 contact each other. The drive motor as a drive unit 110 that drives the developing roller 31 can be the same main motor as the drive unit 110 of the photosensitive drum 1, or a corresponding different drive motor can rotate the photosensitive drum 1 and the developing roller 31. A developing power source E2 (not shown) serving as a developing voltage application unit is connected to the developing roller 31, and a developing voltage is applied to the developing roller 31 from the developing power source E2. Figure 1 The developing roller 31 is counterclockwise-rotated and driven in the direction of the arrow R3 in FIG. 1 by a drive motor 110, so that the surface of the photosensitive drum 1 and the surface of the developing roller 31 move in the same direction at a developing portion c at which the photosensitive drum 1 and the developing roller 31 contact each other. The drive motor as a drive unit 110 that drives the developing roller 31 can be the same main motor as the drive unit 110 of the photosensitive drum 1, or a corresponding different drive motor can rotate the photosensitive drum 1 and the developing roller 31. A developing power source E2 (not shown) serving as a developing voltage application unit is connected to the developing roller 31, and a developing voltage is applied to the developing roller 31 from the developing power source E2. Figure 3) predetermined developing voltage (developing bias) is applied to the developing roller 31. According to the present exemplary embodiment, a direct current voltage of a negative polarity is applied to the developing roller 31 as the developing voltage during development, and the developing voltage is set to -300 V. According to the present exemplary embodiment, toner charged to the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity according to the present exemplary embodiment) adheres to the exposed surface (image portion) that has a reduced absolute value of potential due to being exposed after being uniformly charged as the image forming portion on the photosensitive drum 1. This development method is called reverse development.

[0035] In addition, according to the present exemplary embodiment, although the developing roller 31 is always in contact with the photosensitive drum 1 at the developing section c, the developing roller 31 and the photosensitive drum 1 can be in an abutting state and a separated state. In this case, a developing abutting / separating mechanism can be separately provided. The photosensitive drum 1 can rotate with the developing roller 31 separated from the photosensitive drum 1 during a rotation operation as a pre-rotation process described below.

[0036] The toner image formed on the photosensitive drum 1 is conveyed to the transfer section d. The transfer section d is a contact section of the photosensitive drum 1 and a transfer roller 5 serving as a transfer unit. The transfer roller 5 is a roller type transfer member. The transfer roller 5 according to the present exemplary embodiment uses a roller including a conductive nitrile rubber (NBR) alcohol-based sponge rubber and has an outer diameter of 12 mm and a hardness (Asker-C, 500 gf load) of 30°. The transfer roller 5 according to the present exemplary embodiment is pressed against the photosensitive drum 1 with a predetermined pressure. At the same time, in synchronization with the toner image on the photosensitive drum 1, a recording material P that is a transfer material to which the toner image is to be transferred is conveyed from the storage section 6 to the transfer section d by a conveyance roller 8. Then, the toner image on the photosensitive drum 1 is transferred to the recording material P picked up and conveyed by the photosensitive drum 1 and the transfer roller 5 at the transfer section d under the action of the transfer roller 5. At this time, a transfer power source E3 Figure 3 ) applies a predetermined transfer voltage to the transfer roller 5. The predetermined transfer voltage is a direct current voltage having a polarity opposite to a normal polarity of the toner (positive polarity according to the present exemplary embodiment). Thus, an electric field is formed between the transfer roller 5 and the photosensitive drum 1, and the toner image is electrostatically transferred from the photosensitive drum 1 to the recording material P. According to the present exemplary embodiment, the transfer voltage during transfer is, for example, +1000 V. The toner image is electrostatically transferred from the photosensitive drum 1 to the recording material P by the action of the electric field formed between the transfer roller 5 and the photosensitive drum 1.

[0037] The recording material P with the transferred toner image is conveyed to a fixing device 9 serving as a fixing unit. The fixing device 9 applies heat and pressure to the recording material P, thereby fixing the toner image on the recording material P.

[0038] Meanwhile, the untransferred residual toner that is not transferred to the recording material P and remains on the photosensitive drum 1 is conveyed to the brush member 10 located downstream of the transfer roller 5 in the rotation direction of the photosensitive drum 1. The brush member 10 used in the present exemplary embodiment will be described below.

[0039] 2. Configuration of brush member

[0040] Next, the paper dust removing mechanism according to the present exemplary embodiment will be described below. As shown in Figure 1 The image forming apparatus 100 according to the present exemplary embodiment includes the brush member 10 (a recovery member) as shown in FIG. 1. The brush member 10 is a contact member as the paper dust removing mechanism. According to the present exemplary embodiment, the image forming apparatus 100 includes the brush member 10, and the brush member 10 is in contact with the surface of the photosensitive drum 1 and forms a brush contact portion (a brush contact position) downstream of the transfer portion d and upstream of the charging portion a in the rotation direction of the photosensitive drum 1. According to the present exemplary embodiment, the contact portion of the brush member 10 and the photosensitive drum 1 in the rotation direction of the photosensitive drum 1 will be described as the brush contact portion.

[0041] Figure 2A is a schematic view of the brush member 10 alone along its length direction (substantially parallel to the rotation axis direction of the photosensitive drum 1). In addition, Figure 2B is a schematic view of the brush member 10 along its length direction in a state where the brush member 10 abuts against the photosensitive drum 1.

[0042] The fixed brush 11 constitutes the brush portion of the brush member 10. The fixed brush 11 is fixed and has conductivity. As shown in FIG. 2, the brush member 10 includes a pile yarn (also referred to as a conductive yarn) 11a and a base fabric 11b that supports the pile yarn 11a. The pile yarn 11a is constituted by a plurality of conductive nylon 6 hairs and scrapes the surface of the photosensitive drum 1. As described above, the brush member 10 is disposed to be in contact with the photosensitive drum 1 downstream of the transfer portion d and upstream of the charging portion a in the moving direction (the rotation direction) of the photosensitive drum 1.

[0043] The brush member 10 is disposed so that the length direction of the brush member 10 is substantially parallel to the rotation axis direction of the photosensitive drum 1. According to the present exemplary embodiment, the fixed brush 11 includes the conductive yarn 11a constituted by a nylon fiber containing a conductive substance and the base fabric 11b made of a synthetic fiber containing carbon as a conductive agent, and the conductive yarn 11a is woven in the base fabric 11b. In addition to nylon, rayon, acrylic, and polyester can be used as the material of the conductive yarn 11a.

[0044] As Figure 2AL1 is the distance from the base fabric 11b to the trailing edge of the conductive yarn 11a exposed from the base fabric 11b in a state where the brush member 10 is alone (i.e., in a state where no external force is applied to bend the conductive yarn 11a). According to the present exemplary embodiment, the distance L1 is 6.5 mm. The base fabric 11b is fixed to a support member (not illustrated) disposed at a predetermined position on the image forming apparatus 100 by a fixing material such as double-sided tape, and the brush member 10 is disposed so that the trailing edge of the conductive yarn 11a is pressed against and warped against the photosensitive drum 1. According to the present exemplary embodiment, the gap between the support member and the photosensitive drum 1 is fixed. The distance L2 is the minimum distance from the base fabric 11b of the brush member 10 fixed to the support member to the photosensitive drum 1. According to the present exemplary embodiment, the difference between the distances L2 and L1 is defined as the amount of warping of the brush member 10 with respect to the photosensitive drum 1. According to the present exemplary embodiment, the amount of warping of the brush member 10 with respect to the photosensitive drum 1 is 1 mm. In addition, according to the present exemplary embodiment, as Figure 2A illustrated in FIG. 6, the length L3 of the brush member 10 in the circumferential direction (hereinafter referred to as the "width direction") of the photosensitive drum 1 in a state where the brush member 10 is alone is 5 mm. In addition, according to the present exemplary embodiment, the length of the brush member 10 in the lengthwise direction thereof is 216 mm. Thus, the brush member 10 is in contact with the entire image forming area (an area in which a toner image can be formed) on the photosensitive drum 1 in the direction of the rotation axis of the photosensitive drum 1. In addition, according to the present exemplary embodiment, the conductive yarn 11a has a thickness of 2 denier and a density of 280 kF / inch 2 (kF / inch 2 is a unit of brush density and represents the number of filaments per square inch). As described above, the brush member 10 is supported by a support member (not illustrated), disposed at a fixed position with respect to the photosensitive drum 1, and scrapes the surface of the photosensitive drum 1 as the photosensitive drum 1 moves.

[0045] The brush member 10 captures (recovers) substances such as paper dust that move from the recording material P to the photosensitive drum 1 at the transfer portion d to reduce the amount of paper dust that moves to the charging portion a and the developing portion c downstream of the brush member 10 in the moving direction of the photosensitive drum 1.

[0046] Although the length L3 of the brush member 10 according to the present exemplary embodiment in the circumferential direction (hereinafter referred to as the "width direction") of the photosensitive drum 1 is set to L3 = 5 mm, the length L3 is not limited to this value. The length L3 can be appropriately changed for the lifetime of the image forming apparatus 100 or the process cartridge, for example. Obviously, a brush member 10 having a longer length in the width direction can capture paper dust for a longer period of time.

[0047] Although the length of the brush member 10 in the length direction is set to 216 mm according to the present exemplary embodiment, the length is not limited to this value. For example, the length can be appropriately changed according to the maximum width of the sheet to be fed in the image forming apparatus 100.

[0048] Although the brush member 10 according to the present exemplary embodiment has a fineness of 220T / 96F (indicating a bundle of 96 yarns each having a fineness equal to 220 g / 10000 m), the fineness is desirably set in consideration of the passing property of paper dust. The brush member 10 having a smaller fineness has a poor blocking ability against paper dust, and paper dust easily slips through. This inhibits the charging roller 2 from charging the photosensitive drum 1 and causes image defects. On the other hand, the brush member 10 having an excessively large fineness cannot recover toner and fine paper dust. This causes uneven density due to uneven toner adhesion along the length of the charging roller 2 and image defects due to charging defects at portions having paper dust.

[0049] Although the density of the brush member 10 according to the present exemplary embodiment is set to 280 kF / inch 2 (kF / inch 2 , which is a unit of brush density and indicates the number of filaments per square inch), the density is desirably set in consideration of the toner permeation property and the paper dust capturing property. Specifically, the brush member 10 having an excessively high density causes toner to less permeate, and toner sticks. The stuck toner spreads and causes defects such as contamination in the apparatus. In addition, the brush member 10 having an excessively low density is difficult to capture paper dust. Therefore, from the viewpoint of the paper dust capturing property, the conductive wire 11a preferably has a fineness of 1 denier to 6 denier and a density of 150 kF / inch 2 to 350 kF / inch 2 . From the viewpoint of long life, the length of the brush member 10 in the width direction is preferably 3 mm or more. In addition, a brush power source E4 Figure 3 , which functions as a brush voltage application unit, is connected to the brush member 10.

[0050] 3. Image output operation

[0051] The image forming apparatus 100 according to the present exemplary embodiment performs an image output operation (job) which is a series of operations for forming an image on a single recording material P or a plurality of recording materials P based on a single start instruction from an external device (not shown) such as a personal computer. The job generally includes an image forming process (print process), a pre-rotation process, a sheet separation process in forming an image on a plurality of recording materials P, and a post-rotation process. The image forming process is a period in which an electrostatic image is formed on the photosensitive drum 1, the electrostatic image is developed (a toner image is formed), the toner image is transferred, and the toner image is fixed, and the image forming period refers to this period. More specifically, the timing of the image forming period differs at the positions of electrostatic image formation, toner image formation, toner image transfer, and toner image fixation. Therefore, the image forming operation can be defined as an operation until the toner image transfer or an operation until the toner image fixation. The above definition can be employed because the image forming operation performed on the photosensitive drum 1 ends and the switching of the operation of the photosensitive drum 1 from the image forming operation to the non-image forming operation does not affect the image that has been transferred to the recording material P. The pre-rotation process is a period in which a preparation operation is performed before the image forming process. The sheet separation process is a period between recording materials P when the image forming process (continuous image forming period) is continuously performed on a plurality of recording materials P. The post-rotation process is a period in which an arrangement operation (preparation operation) is performed after the image forming process. The non-image forming period refers to a period that does not include the image forming period but includes the pre-rotation process, the sheet separation process, the post-rotation process, and the pre-rotation process. The pre-rotation process is a preparation operation when the image forming apparatus 100 is turned on or recovers from a sleep state.

[0052] 4. Control Configuration

[0053] Figure 3is a schematic block diagram illustrating a control configuration of main parts for controlling the image forming apparatus 100 according to the present exemplary embodiment. The image forming apparatus 100 includes a control unit 150. The control unit 150 includes a central processing unit (CPU) 151, a memory (storage element) 152, and an input / output unit (not shown). The CPU 151 serving as a calculation control unit is a central element that performs calculation processing. The memory 152 is a storage unit such as a read only memory (ROM) and a random access memory (RAM). The input / output unit controls transmission and reception of signals between various components connected to the control unit 150. The RAM stores sensor detection results and calculation results, and the ROM stores a control program and a data table obtained in advance. According to the present exemplary embodiment, the memory 152 stores the number of rotations of the photosensitive drum 1 as the usage history information about the photosensitive drum 1. In other words, the memory 152 stores the number of rotations of the photosensitive drum 1 as the information about the usage of the photosensitive drum 1. The usage history information about the photosensitive drum 1 is not limited to the above information, and can be any information that changes as the photosensitive drum 1 is used, such as the rotation time of the photosensitive drum 1, the number of printed recording materials P, and layer thickness information about the photosensitive drum 1. The control unit 150 also includes a measurement unit 153. The measurement unit 153 measures the suspension time for determining the condition for performing the following pre-rotation process.

[0054] The control unit 150 is a control unit that controls the operation of the image forming apparatus 100 as a whole. The control unit 150 controls transmission and reception of various electric information signals and driving timing, and performs a predetermined image forming sequence. The components of the image forming apparatus 100 are connected to the control unit 150. For example, with the present exemplary embodiment, the charging power supply El, the developing power supply E2, the transfer power supply E3, the brush power supply E4, the driving motor 110, and the exposure unit 4 are connected to the control unit 150. In particular, with the present exemplary embodiment, the control unit 150 controls the on / off and output value of the various power supplies El, E2, E3, and E4, and performs the operation of extending the following pre-rotation process. According to the present exemplary embodiment, the normal pre-rotation process time is set to 2 seconds. The pre-rotation process time is appropriately set.

[0055] 5. Operation of extending the pre-rotation process

[0056] In a case where the normal pre-rotation process is performed when a job of continuously feeding the recording material P is performed using the image forming apparatus 100, and then the next job is performed after suspension for a predetermined time, toner contamination can occur. This is due to moisture attached to the brush member 10 during sheet feeding in the previous job. Specifically, Figure 4A The moisture on the brush member 10 shown in FIG. 6 begins to accumulate as time elapses immediately after suspension Figure 4B), and finally an aggregate of water droplets is formed on the surface of the photosensitive drum 1 Figure 4C ) Depending on the environment in which the image forming apparatus 100 is used and the number of sheets fed in the previous job, the water droplets have different sizes. For example, in a high-temperature high-humidity environment, the water content of the recording material P is high, and thus the size of the water droplets increases as the number of sheets fed in the previous job increases. In addition, after a predetermined time elapses, the water droplets evaporate over time due to the atmospheric temperature in the image forming apparatus 100. Specifically, immediately after the suspension of the feeding of the recording material P, the moisture is aggregated over time and forms an aggregate of water droplets, and after a predetermined time elapses, the water droplets evaporate and disappear over time. In the case where the brush member 10 according to the present exemplary embodiment is used, thirty seconds after the suspension of the driving of the photosensitive drum 1, a water droplet of the maximum size exists on the surface of the photosensitive drum 1. The suspension time varies depending on the length (L1), width, and density of the brush member 10, because the speed at which the water droplets are formed, the speed at which the water droplets evaporate, and the size of the water droplets formed vary according to the length (L1), width, and density of the brush member 10.

[0057] Figure 5A to Figure 5C Fig. 7 illustrates the state of the portion around the photosensitive drum 1 in the case where the next job is executed while the water droplets are aggregated on the surface of the photosensitive drum 1. When the job starts, Figure 5A The aggregate of the water droplets shown in Fig. 7 moves in the direction of the arrow R1 as the photosensitive drum 1 rotates, and at the charging section a, a part of the aggregate of the water droplets adheres to the charging roller 2. In addition, the water droplets that have passed through the charging section a attract toner on the developing roller 31 at the developing section c Figure 5B Due to this phenomenon, an image defect occurs due to a charging defect, and the toner that adheres to the photosensitive drum 1 is transferred to the recording material P that is conveyed to the transfer section d and is visualized as toner contamination Figure 5C

[0058] Therefore, according to the present exemplary embodiment, when the next job is executed after the suspension for a predetermined time after the job of continuously feeding the recording material P is executed, the operation of extending the pre-rotation process is executed. Specifically, the number of rotations of the photosensitive drum 1 in the pre-rotation process is controlled based on the suspension time between the first image forming operation of forming an image on the recording material P and the second image forming operation that is executed after the first image forming operation.

[0059] The condition for executing the operation of extending the pre-rotation process and the extension time will be described below.

[0060] Figure 6 Fig. 8 illustrates the extension time of the pre-rotation process according to the present exemplary embodiment. As Figure 6 ​As shown in Table 1, according to the first exemplary embodiment, the condition of the pre-rotation process is determined based on the number of fed sheets in the previous job, and the extended time of the pre-rotation process is set to be longer for the larger number of fed sheets. Specifically, the number of rotations of the photosensitive drum 1 is controlled to be larger as the number of fed sheets increases. In addition, it is understood that the extended time of the pre-rotation process reaches the longest time at the 30-second stop time after the previous job, and thereafter decreases. The reason for this will be described below.

[0061] Figure 6 Each of the stop times in Table 1 indicates a case where the stop time is the maximum value, and Figure 6 Each of the number of fed sheets in Table 1 indicates a case where the number of fed sheets is the maximum value. Specifically, the stop time 5 seconds indicates that the stop time is 0 seconds to 5 seconds, and the stop time 10 seconds indicates that the stop time is longer than 5 seconds and does not exceed 10 seconds. In addition, linear interpolation can be performed on the rotation time values between the stop times and between the number of fed sheets. In addition, although not shown, the same fixing temperature control as the image forming process is applied to the fixing device 9 during the pre-rotation process. According to the present exemplary embodiment, the temperature is controlled to be 180°C during the pre-rotation and image forming processes. The fixing temperature control during the pre-rotation process can be appropriately changed from the fixing temperature control during the image forming.

[0062] Figure 7 Fig. 6 illustrates the results of occurrence of toner contamination when feeding sheets having a high moisture content according to the first exemplary embodiment and the results of occurrence of toner contamination when feeding sheets having a high moisture content and the pre-rotation process is not extended (comparative example). In Figure 7 In Table 1, the symbol "O" indicates "none", which indicates that there is no occurrence of toner adhesion to the surface of the photosensitive drum 1 on the image, the symbol "Δ" indicates "slight", which indicates that there is slight toner adhesion to the surface of the photosensitive drum 1 but no adverse effect on the image, and the symbol "X" indicates "significant", which indicates that there is a significant adverse effect on the image. In the sheet feeding experiment, Xerox Vitality Multipurpose sheets of 75 g / m 2 of letter size were used as the recording medium, and before use, the sheets were taken out of the wrapping paper and left for two days in an environment of 30°C in temperature and 80% in humidity. The moisture content of the sheets was measured with a moisture analyzer Moistrex MX-8000 manufactured by NDC Infrared Engineering Co., Ltd., and the result was 9.2%. In addition, for comparison, the moisture content immediately after being taken out of the wrapping paper was measured, and the result was 5.7%. As Figure 7As shown in FIG. 6, the greater the number of sheets fed in the previous job, the worse the toner contamination level in the comparative example. In addition, the toner contamination level is at the lowest level when the pause time is 30 seconds and improves thereafter. This is due to the following reasons. Specifically, as the pause time increases, the water droplets form aggregates, but after a predetermined time, which is 30 seconds or more according to the present example embodiment, the water droplets start to evaporate. Therefore, the influence of the water droplets decreases as the elapsed time increases. Thus, the period of the most severe toner contamination level is about 30 seconds after the sheet feeding. In addition, in the case where the number of sheets fed is 100 or more, the toner contamination level remains unchanged because the moisture generated due to the sheet feeding evaporates due to the atmospheric temperature in the image forming apparatus 100. In contrast, in the first example embodiment, although slight toner contamination occurs in the case where the number of sheets fed in the previous job is 50 or more and the pause time is about 30 seconds, toner contamination does not occur in other cases. This is due to the extended time of the pre-rotation process set based on the number of sheets fed in the previous job and the pause time after the previous job.

[0063] 6. Effects of the Present Example Embodiment

[0064] As described above, according to the present example embodiment, the pre-rotation process is extended for the necessary time based on the number of sheets fed in the previous job and the pause time after the previous job. This promotes the evaporation of the water droplets on the surface of the photosensitive drum 1 and provides stable images without image defects such as toner contamination.

[0065] Although the image forming apparatus 100 to which the present application is applied is described as an example in the present example embodiment using a direct current (DC) charging method, the present application can also be applied to an image forming apparatus using an alternating current (AC) charging method in which an oscillating voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed is used as a charging voltage.

[0066] In addition, although only the direct current component of the developing voltage is described in the present example embodiment, the developing voltage can be an oscillating voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed.

[0067] In addition, although the toner, which is a non-magnetic single-component developer, is used as the developer in the present example embodiment, a magnetic single-component developer can also be used.

[0068] Further, although a "cleanerless system" that does not use a unit for cleaning the photosensitive drum 1 is used according to the present exemplary embodiment, the system is not limited thereto. For example, a "blade cleaning system" that uses a blade as a cleaning unit disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveying direction of the photosensitive drum 1 can be used.

[0069] Further, although the extension time is changed based on the number of fed sheets in the previous job according to the present exemplary embodiment, the configuration is not limited thereto. For example, the extension time can be changed based on the time or distance that the recording material P passes over the photosensitive drum 1.

[0070] As a result of the above description, the configuration described below is adopted according to the present exemplary embodiment.

[0071] The image forming apparatus 100 according to the present exemplary embodiment includes a photosensitive drum 1 configured to rotate and a charging roller 2 configured to charge a surface of the photosensitive drum 1 at a charging section a. The image forming apparatus 100 includes a developing roller 31 configured to supply toner to the surface of the photosensitive drum 1 charged by the charging roller 2 and form a toner image. The image forming apparatus 100 includes a transfer roller 5 configured to contact the photosensitive drum 1 to form a transfer section d and transfer the toner image formed on the photosensitive drum 1 to a recording material P at the transfer section d. The image forming apparatus 100 includes a brush member 10 configured to contact the surface of the photosensitive drum 1 downstream of the transfer section d and upstream of the charging section a in a rotation direction of the photosensitive drum 1 and a drive motor 110 configured to rotate the photosensitive drum 1. The image forming apparatus 100 includes a memory 152 configured to store usage history information about the photosensitive drum 1 and a control unit 150 configured to control the drive motor 110. The image forming apparatus 100 includes a measurement unit 153 configured to measure a suspension time between a first image forming operation of forming an image on the recording material P and a second image forming operation performed after the first image forming operation.

[0072] After the suspension time between the first image forming operation of forming an image on the recording material P and the second image forming operation performed after the first image forming operation, a rotation operation of rotating the photosensitive drum 1 is controlled to be performed before the second image forming operation is performed. The number of rotations of the photosensitive drum 1 in the rotation operation performed before the second image forming operation is controlled based on the usage history information about the photosensitive drum 1 and the suspension time. The target of the control is not limited to the number of rotations of the photosensitive drum 1 and can be a rotation time of the photosensitive drum 1.

[0073] In addition, in a case where the number of recording materials P conveyed by the transfer section d in the first image forming operation is a first value, the number of rotations of the photosensitive drum 1 in the rotation operation is controlled to be smaller than in a case where the number of recording materials P is a second value that is larger than the first value.

[0074] In addition, the suspension time is a time from when the photosensitive drum 1 changes from a driven state in which the photosensitive drum 1 rotates to a suspended state in which the rotation of the photosensitive drum 1 is suspended after the first image forming operation, to when the photosensitive drum 1 changes from the suspended state to the driven state in order to start the second image forming operation. The suspension time according to the present exemplary embodiment is not limited to those described above, and can be a time that is correlated with the accumulation phenomenon of the water droplets on the brush member 10. For example, the suspension time can be a time from a time point immediately after the end of the first image forming operation to a time point immediately before the start of the second image forming operation. The suspension time can be any period of time as long as the suspension time includes a time during which the photosensitive drum 1 is suspended.

[0075] In addition, the suspension time can be predicted not only by the measurement unit 153 but also from the decay condition of the surface potential of the photosensitive drum 1, the temperature transition of the image forming apparatus 100, and the temperature change of the fixing device 9.

[0076] In addition, although according to the present exemplary embodiment, as Figure 6 In addition, although according to the present exemplary embodiment, as

[0077] Next, another exemplary embodiment of the present application will be described below. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are similar to those of the image forming apparatus 100 according to the first exemplary embodiment. Therefore, components of the image forming apparatus according to the present exemplary embodiment that have functions or configurations similar to or corresponding to those of the components of the image forming apparatus 100 according to the first exemplary embodiment are assigned the same reference numerals as those of the components of the image forming apparatus 100 according to the first exemplary embodiment, and a redundant detailed description thereof is omitted.

[0078] 1. Features of the second exemplary embodiment

[0079] The second exemplary embodiment is characterized in that the duration of the pre-rotation process is variable based on the operating environment of the image forming apparatus 100. The image forming apparatus 100 in the second exemplary embodiment includes an environmental sensor 300, and the duration of the pre-rotation process described in the first exemplary embodiment is determined based on environmental information as the detection result of the environmental sensor 300. The environmental information includes absolute moisture content information about the environment calculated by the CPU 151 based on the detection results of the temperature sensor and humidity sensor (both not shown) of the environmental sensor 300. According to the second exemplary embodiment, the absolute moisture content obtained from the environmental sensor 300 is 0.1 g / m³. 3 The data is stored in the memory 152 of the control unit 150. Then, when the image forming apparatus 100 receives an image output operation (work) signal, the control unit 150 determines whether the absolute moisture content is higher or lower than the threshold of 10.5 g / m³. 3 When the absolute moisture content is higher than the threshold of 10.5 g / m³ 3 In this case, the same operation of extending the forward rotation process as in the first exemplary embodiment is performed. The extension time of the forward rotation process is the same as that in the first exemplary embodiment. Figure 6 The described extension times are similar, so a repetition of that description is omitted. On the other hand, when the absolute moisture content is below the threshold of 10.5 g / m³... 3 In such cases, the extended pre-rotation process is not performed. This prevents unnecessary rotation of the photosensitive drum 1 in environments other than those with high absolute moisture content. The absolute moisture content used to determine whether to change the extension time of the pre-rotation process based on the usage environment is not limited to the values ​​mentioned above and can be appropriately changed.

[0080] 2. Functional effects of the second exemplary embodiment

[0081] As described above, according to the second exemplary embodiment, the control described below is performed based on the absolute moisture content obtained from the detection result of the environmental sensor 300. Control is only applied when the absolute moisture content is higher than 10.5 g / m³. 3 In certain circumstances, the pre-rotation process is extended by the necessary time based on the amount of sheet fed in the previous operation and the stop time after the previous operation. This prevents unnecessary rotation of the photosensitive drum 1 in environments other than those with high absolute moisture content, and allows for the effective evaporation of water droplets on the surface of the photosensitive drum 1 as needed.

[0082] As a result of the above description, the configuration described below is adopted according to the second exemplary embodiment.

[0083] The image forming apparatus 100 includes the environment sensor 300 configured to detect an installation environment of the image forming apparatus 100, and controls the number of rotations based on the installation environment. As used herein, the term "installation environment" refers to temperature or humidity and absolute moisture content detected by the environment sensor 300. The absolute moisture content can be calculated from the temperature and humidity detection results. In addition, the absolute moisture content can be calculated by predicting the temperature or humidity.

[0084] According to the second exemplary embodiment, based on the absolute moisture content obtained from the detection results of the environment sensor 300, the use environment of the image forming apparatus 100 is divided into two environments, i.e., an environment having a high absolute moisture content and an environment other than the environment having a high absolute moisture content, thereby determining whether to extend the pre-rotation process. However, this configuration is not limited thereto. For example, the use environment of the image forming apparatus 100 can be divided into a plurality of environments, e.g., three environments, based on the absolute moisture content, and the extension time of the pre-rotation process can be appropriately changed for the environments. Specifically, a plurality of threshold values can be set. In addition, the extension time of the pre-rotation process can be appropriately changed based on the absolute moisture content. In other words, in a case where the absolute moisture content is detected as a first absolute moisture content, the number of rotations of the photosensitive drum 1 can be controlled to be greater than in a case where a second absolute moisture content lower than the first absolute moisture content is detected.

[0085] In addition, although the environment sensor 300 is used as a unit for detecting the use environment of the image forming apparatus 100 according to the second exemplary embodiment, this is not a limiting configuration. For example, the use environment can be determined based on detection of the resistance value of the transfer roller 5 (transfer automatic transfer voltage control (transfer ATVC) result).

[0086] 1. Brush voltage control

[0087] The present exemplary embodiment is characterized in that, Figure 3 The brush power source E4 in the brush power source E4 applies a brush voltage to the brush member 10 during the pre-rotation process. The brush voltage control in the pre-rotation process will be described below.

[0088] According to the present exemplary embodiment, the control unit 150 applies a predetermined brush voltage to the brush member 10. The predetermined brush voltage is a direct current voltage of negative polarity. The brush voltage application unit E4, for example, can apply a voltage on which a direct current component and an alternating current component are superimposed. According to the present exemplary embodiment, the brush voltage during the image forming process is -300 V. Meanwhile, the surface potential of the photosensitive drum 1 after the transfer section d is approximately -50 V. Therefore, the untransferred residual toner that is transported from the transfer section d and charged to positive polarity is first recovered by the brush member 10 due to the potential difference between the brush voltage at the brush section e and the surface potential of the photosensitive drum 1. On the other hand, the toner charged to negative polarity is attracted toward the photosensitive drum 1 at the brush section e and passes through the brush section e. The toner that passes through the brush section e has a desired negative polarity charge due to the uniform discharge at the charging section a and is transported to the developing section c. Among the toner transported to the developing section c, the toner in the non-image area (non-exposed area) moves to the developing roller 31 due to the potential difference between the dark area potential (Vd) of the surface of the photosensitive drum 1 and the developing bias (Vdc) and is recovered by the developing device 3. According to the present exemplary embodiment, as in the first exemplary embodiment, the dark area potential (Vd) is approximately -600 V and the developing bias (Vdc) is -300 V. On the other hand, the toner in the image area (exposed area) is not moved to the developing roller 31 due to the potential difference between the bright area potential (Vl) of the surface of the photosensitive drum 1 and the developing bias (Vdc) and is transported to the transfer section d as an image portion with the rotation of the photosensitive drum 1 and is transferred to the recording material P. As in the first exemplary embodiment, the bright area potential (Vl) according to the present exemplary embodiment is approximately -100 V.

[0089] 2. Pre-rotation process extension operation

[0090] Figure 8 is a timing chart illustrating the pre-rotation process according to the present exemplary embodiment. In Figure 8 , timing A is the timing at which the image forming apparatus 100 receives an image output operation (job) signal from an external device and starts the pre-rotation process. At this time, the control unit 150 determines the extension time of the pre-rotation process based on the number of fed sheets in the previous job and the suspension time after the previous job. Then, at timing A, the driving of the driving motor 110 is started, and the output of the charging voltage and the output of the brush voltage are turned on. In addition, the fixing device 9 starts the output, thereby controlling the fixing temperature to be the same as the image forming process (180°C). Depending on the power-on time, the timing at which the charging voltage and the brush voltage are turned on can be earlier or later. In addition, depending on the responsiveness of the fixing device 9, the timing at which the fixing temperature control is output can be earlier or later.

[0091] The output value of the charging voltage is the same as during the image forming process, -1200V, so that the surface potential of the photosensitive drum 1 is uniformly equal to the dark area potential (-600V). While the surface potential of the photosensitive drum 1 is maintained at the value of the dark area potential (-600V), the surface of the photosensitive drum 1 passes through the developing section c and reaches the transfer section d. At this time, no transfer voltage is applied to the transfer roller 5, so the surface of the photosensitive drum 1 reaches the brush section e in a state of maintaining the dark area potential (-600V). The output value of the brush voltage is the same as during the image forming process, -300V. Therefore, the positive polarity toner remaining on the brush member 10 is discharged to the surface of the photosensitive drum 1 due to the potential difference between the brush voltage and the dark area potential (-600V) of the photosensitive drum 1.

[0092] While the cleaning operation of discharging the untransferred residual toner first recovered by the brush member 10 during the image forming process is performed during the post-rotation process according to the present exemplary embodiment, some toner remains on the brush member 10 even thereafter. Therefore, the residual toner having a positive polarity on the brush member 10 is actively discharged after timing A and thereafter. At this time, moisture is present around the toner, and the toner is discharged from the brush member 10 together with the moisture. Figure 9 The state of the toner and the moisture in the brush member 10 at this time is illustrated. From Figure 9 It is understood that the moisture adheres to the toner on the brush member 10 and is discharged together with the toner discharged from the brush member 10. As described above, the discharge of the residual toner on the brush member 10 promotes the discharge of the moisture adhering to the brush member 10.

[0093] According to the present exemplary embodiment, while no transfer voltage is applied at timing A, the brush voltage (-300V) will be set to a value that does not lower the surface potential of the photosensitive drum 1, i.e., a voltage value having the same negative polarity as the surface potential of the photosensitive drum 1 and having a small absolute value.

[0094] Next, at timing B in Figure 8 the output of the transfer voltage is turned on. The output value of the transfer voltage at this time is +1000V. Therefore, the surface potential of the photosensitive drum 1 after passing through the transfer section d is approximately -50V. At the same time, the output value of the brush voltage is still maintained at -300V, so that the negative polarity toner remaining on the brush member 10 at this time is discharged to the surface of the photosensitive drum 1 due to the potential difference between the brush voltage and the surface potential of the photosensitive drum 1 (-50V). Then, similarly, the discharge of the moisture adhering to the brush member 10 is promoted. Timing B is set to secure time to discharge the positive polarity toner in the brush member 10, and according to the present exemplary embodiment, timing B is set 500ms after timing A.

[0095] As described above, the brush voltage is applied and the positive and negative polarity residual toner in the brush member 10 is discharged due to the potential difference from the surface potential of the photosensitive drum 1 to promote the discharge of moisture.

[0096] Figure 8 Timing C in FIG. 12 is a timing at which the image forming process starts without extension of the pre-rotation process. In the case where timing A determines that the pre-rotation process is to be extended, the extension operation is started from timing C, and the image forming process is started from timing D. Specifically, in the case where timing A determines that the pre-rotation process is to be extended, the extension operation is started from timing C, and the image forming process is started from timing D. Figure 8 The period from timing C to timing D in FIG. 12 is the extension time of the pre-rotation process.

[0097] Figure 10 The extension time of the pre-rotation process according to the present exemplary embodiment is illustrated. From Figure 10 It is understood that the extension time of the pre-rotation process is shorter than the extension time of the pre-rotation process according to the first exemplary embodiment (t2). Figure 6 This is because according to the third exemplary embodiment, moisture is actively discharged together with the residual toner in the brush member 10 by the brush voltage, thereby promoting the evaporation of the water droplets in the pre-rotation process.

[0098] 3. Effects of the Present Exemplary Embodiment

[0099] As described above, according to the present exemplary embodiment, the residual toner in the brush member 10 is discharged by the brush voltage at the same time as the start of the pre-rotation process, and at the same time, the pre-rotation process is extended for the necessary time based on the number of fed sheets in the previous job and the suspension time since the previous job. Since moisture is discharged together with the residual toner in the brush member 10, the water droplets on the surface of the photosensitive drum 1 evaporate effectively and the extension time of the pre-rotation process is reduced.

[0100] Thus, while increasing the life of the image forming apparatus 100, a stable image with reduced image defects such as toner contamination is provided.

[0101] As a result of the above description, the configuration described below is adopted according to the third exemplary embodiment.

[0102] The image forming apparatus 100 includes a brush power source (brush voltage application unit) E4 configured to apply a brush voltage to the brush member 10. The brush member 10 is a conductive brush, and the brush voltage application unit E4 is controlled to cause the brush voltage having the same polarity as the toner charged to the normal polarity to be applied to the brush member 10 while the rotation operation is performed.

[0103] The brush voltage application unit E4 is controlled so that the potential difference between the brush voltage applied to the brush member 10 and the surface potential of the photosensitive drum 1 gradually increases at the brush portion e in which the surface of the photosensitive drum 1 and the brush member 10 contact each other while the rotation operation is performed.

[0104] The brush voltage application unit E4 is controlled so that the brush voltage applied to the brush member 10 and the surface potential of the photosensitive drum 1 have the same polarity, and the absolute value of the brush voltage is larger than the absolute value of the surface potential of the photosensitive drum 1. Alternatively, the brush voltage application unit E4 is controlled so that the brush voltage applied to the brush member 10 and the surface potential of the photosensitive drum 1 have the same polarity, and the absolute value of the brush voltage is smaller than the absolute value of the surface potential of the photosensitive drum 1.

[0105] In addition, the image forming apparatus 100 includes a transfer power source (transfer voltage application unit) E3 configured to apply a transfer voltage to the transfer roller 5. The transfer voltage application unit E3 is controlled so that the brush voltage applied to the brush member 10 and the surface potential of the photosensitive drum 1 at the transfer portion d have the same polarity, and the surface potential of the photosensitive drum 1 at the transfer portion d is lower than the brush voltage applied to the brush member 10.

[0106] Although the surface potential of the photosensitive drum 1 is controlled by changing the transfer voltage and the brush voltage according to the present exemplary embodiment, this is not a limiting configuration. For example, the transfer voltage and the brush voltage can be changed in a case where the photosensitive drum 1 is grounded to set the surface potential to ground (0 V). In addition, the potential relationship of the transfer roller 5 and the brush member 10 can be controlled by directly applying a voltage to the photosensitive drum 1.

[0107] Although an image forming apparatus 100 using a direct current (DC) charging method is described as an example in the present exemplary embodiment, the present application can also be applied to an image forming apparatus using an alternating current charging method in which an oscillation voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed is used as a charging voltage.

[0108] In addition, although only the direct current component of the developing voltage is described according to the present exemplary embodiment, the developing voltage can be an oscillation voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed.

[0109] In addition, although toner, which is a magnetic single-component developer, is used as the developer according to the present exemplary embodiment, a non-magnetic single-component developer can also be used.

[0110] In addition, although a "cleanerless system" that does not use a unit for cleaning the photosensitive drum 1 is used according to the present exemplary embodiment, this is not a limiting configuration. For example, a "blade cleaning system" that uses a blade as a cleaning unit disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveyance direction of the photosensitive drum 1 can be used.

[0111] In addition, although the extension time is changed based on the number of fed sheets in the previous job according to the present exemplary embodiment, this is not a limiting configuration. For example, the extension time can be changed based on the time or distance of the sheet passing through the photosensitive drum 1.

[0112] In addition, although the recording material P that is the transfer material to which the toner image is to be transferred is conveyed to the transfer section d and undergoes transfer as a toner image according to the present exemplary embodiment, a conveyance belt for conveying the recording material P to the transfer section d can be provided.

[0113] In addition, according to the present exemplary embodiment, a pre-exposure unit for exposing the surface of the photosensitive drum 1 at a position downstream of the transfer section d and upstream of the charging section a in the rotation direction of the photosensitive drum 1 can be provided. The pre-exposure unit can be disposed upstream or downstream of the brush section (contact section) e in which the brush member 10 and the photosensitive drum 1 contact each other. In the case where the pre-exposure unit is disposed upstream of the contact section e, the surface potential of the photosensitive drum 1 can be controlled by the pre-exposure unit.

[0114] Next, a fourth exemplary embodiment will be described below. As Figure 1 As shown in FIG. 1, the image forming apparatus 100 according to the present exemplary embodiment includes a paper dust capturing mechanism and a brush member 10 that constitutes a contact member as a moisture recovery mechanism (recovery member). In the image forming apparatus 100 according to the present exemplary embodiment, the brush member is disposed to contact the surface of the photosensitive drum 1 at a position downstream of the transfer section d and upstream of the charging section a in the rotation direction of the photosensitive drum 1. In the present exemplary embodiment, the brush contact section refers to the contact section of the brush member 10 and the photosensitive drum 1 in the rotation direction of the photosensitive drum 1.

[0115] Figure 1 And Figure 12 The layout in a state where the image forming apparatus 100 is placed on a flat installation surface as a normally expected installation state is illustrated. The left-right direction of the drawing sheet corresponds to the horizontal direction of the image forming apparatus 100, and the up-down direction of the drawing sheet corresponds to the up-down direction (gravity direction, vertical direction) of the image forming apparatus 100.

[0116] Comparison of water absorption amount of brush and image evaluation

[0117] Next, the water absorption amount and the image evaluation of the brush member 10 according to the present exemplary embodiment will be described in detail below together with comparative examples. The water absorption amount of the brush member 10 according to the present exemplary embodiment is measured by the following manner. The measurement manner is not limited to these manners described herein.

[0118] Measurement of water absorption amount

[0119] A stationary brush 11 including a plurality of conductive yarns 11a made of various materials and fibers of different densities and woven in a base cloth 11b as shown in FIG. 2 is used. The shape and size of the stationary brush 11 are similarly L1 = 6.5 mm, L3 = 5 mm, and the length in the length direction = 216 mm.

[0120] FIG. 11 illustrates the measurement of the water absorption amount of the brush member 10 according to the present exemplary embodiment. After measuring the initial weight (W0) of the stationary brush 11, the contact surface of the stationary brush 11 to be contacted with the photosensitive drum 1 is moved toward the water surface of 20°C so that the contact surface is parallel to the water surface ( Figure 11A ), and only the tail edge of 1 mm of the stationary brush 11 is immersed in the water for 10 seconds ( Figure 11B ). The contact surface of the stationary brush 11 to be contacted with the photosensitive drum 1 is a term for the collective edge of the plurality of conductive yarns 11a to be cut to substantially the same length as a surface. The contact surface can be understood as a virtual surface including each tail edge of the plurality of fiber yarns 11a. Specifically, the stationary brush 11 (contact surface) is brought close to the water surface while keeping the contact surface parallel to the water surface so that the tail edges of the plurality of fiber yarns 11a enter the water at substantially the same timing and the degree of immersion of the plurality of fiber yarns 11a is not different. Even if they are different, the difference is not large because only the area of 1 mm from the tail edge of each fiber yarn 11a is reliably immersed in the water. Thereafter, the stationary brush 11 is lifted from the water surface, and the weight (W) of the sample is measured at the timing at which the water droplets no longer drop from the sample. Then, the water absorption amount is calculated using the following formula.

[0121] Water absorption amount (g) = W - W0

[0122] Comparison of water absorption amount

[0123] A test for comparing the water absorption amount is performed using the conductive yarns 11a of the following materials and densities as the fiber material of the conductive yarns 11a.

[0124] (Table 1)

[0125]

[0126] From items A, B, C, and F in Table 1, it can be understood that, from the perspective of the fiber material, the water absorption amount of the SFCP and This shows a tendency corresponding to the magnitude of the water absorption rate (rate of change in weight of a sample immersed in water at 23°C for 24 hours) measured according to the American Society for Testing Materials (ASTM) D570 test procedure, and the higher the water absorption rate of the fibrous material, the greater the amount of water absorbed by the fibrous material.

[0127] In addition, it is understood from items C, D, E, F, and G that the higher the density of the conductive filaments 11a, the greater the amount of water absorbed, using the same fibrous material. This is because the surface area of the conductive filaments 11a is greater the higher the density, and the amount of attached moisture per unit area increases.

[0128] Although 6 nylon is used as the fibrous material according to the present exemplary embodiment, the fibrous material is not limited to 6 nylon. Any fibrous material having a high water absorption can be used, and the water absorption rate measured according to the ASTM D570 test procedure desirably is 0.5% or more, more desirably 1.1% or more.

[0129] Image Evaluation Comparison

[0130] Next, a comparative image evaluation test was performed in the case where a plurality of recording materials fed in a high-temperature high-humidity environment were stored. In the image evaluation, Xerox Vitality Multipurpose Sheets of a sheet size of letter paper having a grammage of 75 g / m 2 were used, which were taken out of a wrapping paper and left for two days in an environment of an ambient temperature of 30°C and an ambient humidity of 80%. The moisture content of the sheets was measured with a moisture analyzer Moistrex MX-8000 manufactured by NDC Infrared Engineering Co., Ltd., and the result was 9.2%. In addition, for comparison, the moisture immediately after being taken out of the wrapping paper was measured, and the result was 5.7%.

[0131] (Table 2)

[0132]

[0133]

[0134] Table 2 illustrates the results of occurrence of toner contamination images when 100 of the above recording materials were continuously fed. In Table 2, “none” indicates that no toner contamination occurred on the image, “slight” indicates that a slight toner contamination image occurred on the image, and “significant” indicates that a significant toner contamination image occurred on the image.

[0135] It is understood from items A, B, C, and F in Table 2 that using the SFCP and a significant toner contamination image occurred when 10 of the sheets were continuously fed, while using the And 6nylon greatly reduces toner contamination images.

[0136] In addition, from items C, D, and E, F, and G in Table 2, it can be understood that toner contamination images occur at different timings for different densities. In the case of 6nylon at a density of 70 kF, a slight toner contamination image occurred on the 50th sheet. In the case of 6nylon at a density of 150 kF, a slight toner contamination image occurred on the 100th sheet. In the case of 6nylon at a density of 240 kF, no toner contamination image occurred even on the 100th sheet. This indicates that the higher the density, the less likely it is that a toner contamination image will occur. This is for the following reason. Specifically, the higher the density, the greater the water absorption amount, and therefore even in the case of feeding recording material having a high water content, the brush member 10 can store moisture therein.

[0137] In the present exemplary embodiment, in the case of recording material expected to have a high water content, the measured water absorption amount of the fixed brush 11 desirably is 2.4 g or more, and the water absorption amount per unit area desirably is 2.2 mg / mm 2 or more. Therefore, in the case of using (0.5% of water absorption rate), the density of the conductive filaments 11a desirably is 240 kF or more, and in the case of using 6nylon (1.1% of water absorption rate), the density of the conductive filaments 11a desirably is 150 kF or more.

[0138] Here, the water absorption amount per unit area refers to a value obtained by dividing the measured water content of the fixed brush 11 by the contact area of the fixed brush 11 and the photosensitive drum 1. The abutment area of the fixed brush 11 and the photosensitive drum 1 is the set of abutment areas of the trailing edges of the plurality of conductive filaments 11a and the photosensitive drum 1, and at a microscopic level, there is a gap area between adjacent trailing edges of the plurality of conductive filaments 11a that does not contact the surface of the photosensitive drum 1. Therefore, it is technically difficult to define the abutment area of the fixed brush 11 and the photosensitive drum 1 as a single area. However, a single area can be defined by, for example, ignoring the gap area and determining the overall profile of the set of abutment areas of the plurality of conductive filaments 11a and the photosensitive drum 1 as an approximate abutment area, and the area of this area can be used as the contact area.

[0139] According to the present exemplary embodiment, the contact area is determined to be 1 mm x 5 mm x 216 mm = 1080 mm 2 According to the present exemplary embodiment, the water absorption per unit area of items A, B, C, D, E, F, and G is 0.27 mg / mm 2 , 0.74 mg / mm 2 , 1.38 mg / mm 2 , 2.22 mg / mm 2 , 1.85 mg / mm 2 , 2.22 mg / mm 2 , and 2.68 mg / mm 2 , respectively. The above-described manner for defining the contact area is not the only manner, and any other manner can be used.

[0140] Effects in the Present Exemplary Embodiment

[0141] As described above, according to the present exemplary embodiment, the brush member 10 having a water absorption per unit area of 2.2 mg / mm 2 is disposed in the rotation direction of the photosensitive drum 1 downstream of the transfer section d and upstream of the charging section a. Therefore, even in the case of continuously feeding the recording material having a high water content, the brush member 10 can sufficiently recover moisture adhering to the surface of the photosensitive drum 1. This prevents image defects, such as toner smearing images, caused by moisture.

[0142] Although the image forming apparatus 100 to which the present application is applied using a direct current (DC) charging method is described as an example in the present exemplary embodiment, the present application can also be applied to an image forming apparatus using an alternating current charging method in which an oscillation voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed is used as a charging voltage.

[0143] In addition, although only the direct current component of the developing voltage is described according to the present exemplary embodiment, the developing voltage can be an oscillation voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed.

[0144] In addition, although toner as a non-magnetic single-component developer is used as the developer according to the present exemplary embodiment, a magnetic single-component developer can also be used.

[0145] In addition, although a "cleaner-less system" that does not have a unit for cleaning the photosensitive drum 1 is used according to the present exemplary embodiment, this is not a limiting manner. For example, a "doctor blade cleaning system" that uses a doctor blade as a cleaning unit disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveying direction of the photosensitive drum 1 can be used.

[0146] In addition, although the density of the conductive yarn 11a is determined in consideration of the case where the recording material having a high water content is continuously fed according to the present exemplary embodiment, this is not a limiting configuration. Based on the use environment (e.g., a high humidity environment) of the image forming apparatus 100, the time between sheets during continuous sheet feeding can be set longer than normal. In this case, even if the water absorption amount of the brush member 10 is low, toner from contaminating the image is prevented, and thus the density of the conductive yarn 11a can be appropriately set according to the time between sheets.

[0147] Next, a fifth exemplary embodiment of the present application will be described below. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are similar to those of the image forming apparatus 100 according to the fourth exemplary embodiment. Therefore, components of the image forming apparatus according to the present exemplary embodiment that have functions or configurations similar to or corresponding to those of the components of the image forming apparatus 100 according to the fourth exemplary embodiment are assigned the same reference numerals as those of the components of the image forming apparatus 100 according to the fourth exemplary embodiment, and a redundant detailed description thereof is omitted.

[0148] The present exemplary embodiment is characterized in that Figure 3 The brush power source E4 applies a brush voltage to the brush member 10 as shown in FIG. 8. Control of the brush voltage during the image forming process will be described below.

[0149] 1. Brush voltage control

[0150] According to the present exemplary embodiment, the control unit 150 controls the brush power supply E4 to apply a predetermined brush voltage to the brush member 10. The predetermined brush voltage is a direct current voltage of negative polarity. The brush power supply E4 serving as a brush voltage application unit can apply, for example, a voltage having a direct current component and an alternating current component superimposed thereon. According to the present exemplary embodiment, the brush voltage during the image forming process is -300 V. Meanwhile, the surface potential of the photosensitive drum 1 after the transfer section d is approximately -50 V. Thus, due to the potential difference between the brush voltage at the brush section e and the surface potential of the photosensitive drum 1, the untransferred residual toner charged to positive polarity, which is transported from the transfer section d, is first recovered by the brush member 10. On the other hand, the toner charged to negative polarity is attracted to the photosensitive drum 1 at the brush section e and passes through the brush section e. The toner passing through the brush section e has a desired negative polarity charge due to the uniform discharge at the charging section a and is transported to the developing section c. Among the toner transported to the developing section c, the toner in the non-image area (non-exposed area) moves to the developing roller 31 due to the potential difference between the dark area potential (Vd) of the surface of the photosensitive drum 1 and the developing bias (Vdc) and is recovered by the developing device 3. According to the present exemplary embodiment, as in the fourth exemplary embodiment, the dark area potential (Vd) is approximately -600 V and the developing bias (Vdc) is -300 V. On the other hand, the toner in the image area (exposed area) does not move to the developing roller 31 due to the potential difference between the light area potential (Vl) of the surface of the photosensitive drum 1 and the developing bias (Vdc), is transported to the transfer section d as an image portion with the rotation of the photosensitive drum 1, and is transferred to the recording material P. The light area potential (Vl) according to the present exemplary embodiment is approximately -100 V, as in the fourth exemplary embodiment.

[0151] Figure 12 Fig. 6 illustrates the state of a portion around the photosensitive drum 1 during the image forming process. From Figure 12 It is understood that the untransferred residual toner having positive polarity is first recovered by the brush member 10, while the untransferred residual toner having negative polarity passes through the brush section e and the charging section a and moves to the developing roller 31.

[0152] Figure 13 Fig. 7 illustrates the state of the toner first recovered by the brush member 10. From Figure 13 It is understood that moisture adheres to the toner first recovered by the brush member 10. As described above, the moisture adhering to the surface of the photosensitive drum 1 is not only recovered by the brush member 10 together with the untransferred residual toner, but also is transported toward the base fabric 11b (opposite to the trailing edge of the brush) of the brush member 10 together with the toner due to the brush voltage. Thus, compared to a configuration in which no brush voltage is applied, the brush member 10 can recover a large amount of moisture.

[0153] 2. Image evaluation comparison

[0154] A test for comparing image evaluations in a case where a plurality of recording materials that have been stored in a high-temperature high-humidity environment are fed was performed as in the fourth exemplary embodiment. The detailed conditions were similar to those in the fourth exemplary embodiment, and thus a repeated description thereof is omitted.

[0155] (Table 3)

[0156]

[0157]

[0158] Table 3 shows the occurrence results of toner contamination images when 200 of the above recording materials were continuously fed. The image ranks in Table 3 are similar to those according to the fourth exemplary embodiment.

[0159] From Table 3, it can be understood that the occurrence time of toner contamination images is delayed for all the fiber materials, that is, toner contamination images originating from an increase in the number of continuously fed sheets are reduced. This is for the following reason. Specifically, since the brush voltage moves moisture together with toner toward the base fabric 11b of the brush member 10 (opposite to the trailing edge of the brush), a large amount of moisture is recovered compared to a case where the brush voltage is not applied.

[0160] 3. Effects of the Present Exemplary Embodiment

[0161] As described above, according to the present exemplary embodiment, the brush voltage moves moisture adhering to the surface of the photosensitive drum 1 together with residual toner that is not transferred toward the base fabric 11b of the brush member 10. Therefore, the brush member 10 can recover a large amount of moisture, and toner contamination images originating from an increase in the number of continuously fed sheets are reduced.

[0162] As a result of the above description, the configuration described below is adopted according to the fifth exemplary embodiment.

[0163] The image forming apparatus 100 includes a brush power source E4 as a brush voltage application unit that applies a brush voltage to the brush member 10. The brush member 10 is a conductive brush, and the control unit 150 controls the brush voltage applied from the brush power source E4 to the brush member 10 so that the brush voltage having the same polarity as the toner charged to a normal polarity is applied to the brush member 10 while the image forming operation is performed.

[0164] The control unit 150 controls the voltage applied from the brush power source E4 to the brush member 10 so that the brush voltage applied to the brush member 10 has the same polarity as the surface potential of the photosensitive drum 1 and the absolute value of the brush voltage is greater than the absolute value of the surface potential of the photosensitive drum 1.

[0165] Further, the image forming apparatus 100 includes a transfer power source E3 as a transfer voltage application unit that applies a transfer voltage to the transfer roller 5. The control unit 150 controls the transfer power source E3 so that the brush voltage applied to the brush member 10 has the same polarity as the surface potential of the photosensitive drum 1 at the transfer portion d, and the surface potential of the photosensitive drum 1 at the transfer portion d is lower than the brush voltage applied to the brush member 10.

[0166] Although the surface potential of the photosensitive drum 1 is controlled by changing the transfer voltage or the brush voltage according to the present exemplary embodiment, this is not a limiting configuration. For example, the transfer voltage and the brush voltage can be changed in a case where the photosensitive drum 1 is grounded to set the surface potential to ground (0 V). Further, the potential relationship of the transfer roller 5 and the brush member 10 can be controlled by directly applying a voltage to the photosensitive drum 1.

[0167] Although the present application is described as an example in the image forming apparatus 100 using a direct current (DC) charging method in the present exemplary embodiment, the present application can also be applied to an image forming apparatus using an alternating current charging method in which an oscillation voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed is used as a charging voltage.

[0168] Further, although only the direct current component of the developing voltage is described according to the present exemplary embodiment, the developing voltage can be an oscillation voltage in which a direct current voltage (DC component) and an alternating current voltage (AC component) are superimposed.

[0169] Further, although toner as a non-magnetic single-component developer is used as the developer according to the present exemplary embodiment, a magnetic single-component developer can also be used.

[0170] Further, although the “cleanerless method” that does not use a unit for cleaning the photosensitive drum 1 is used according to the present exemplary embodiment, this is not a limiting method. For example, a “doctor blade cleaning method” that uses a doctor blade as a cleaning unit that is disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveyance direction of the photosensitive drum 1 can be used.

[0171] Further, although the recording material P that is a transfer material on which a toner image is transferred is conveyed to the transfer portion d and undergoes transfer according to the present exemplary embodiment, a conveyance belt for conveying the recording material P to the transfer portion d can be provided.

[0172] Further, according to the present exemplary embodiment, it is possible to provide a pre-exposure unit for exposing the surface of the photosensitive drum 1 at a position downstream of the transfer portion d and upstream of the charging portion a in the rotation direction of the photosensitive drum. The pre-exposure unit can be disposed upstream or downstream of the contact portion e in which the brush member 10 and the photosensitive drum 1 contact each other. In the case where the pre-exposure unit is disposed upstream of the contact portion e, the surface potential of the photosensitive drum 1 can be controlled by the pre-exposure unit.

[0173] Further, although the density of the conductive yarn 11a is determined in consideration of the case where the recording material having a high water content is continuously fed according to the present exemplary embodiment, this is not a limiting configuration. Based on the use environment (e.g., a high humidity environment) of the image forming apparatus 100, the time between the sheets during continuous sheet feeding can be set longer than normal. In this case, even if the water absorption amount of the brush member 10 is low, toner contamination images are prevented, so that the density of the conductive yarn 11a can be appropriately set according to the time between the sheets.

[0174] While the present application has been described with reference to exemplary embodiments, it is to be understood that the application is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus, comprising: The image-carrying component is configured to be rotated and driven; A charged component is configured to charge the surface of the image-carrying component at the charged part; The developing member is configured to supply toner to an electrostatic latent image formed on the surface of an image-carrying member that is charged by the charged member, and to form a toner image; The transfer member is configured to form a transfer section for holding the recording material between the transfer member and the image carrier member, and to transfer the toner image from the image carrier member to the recording material at the transfer section. as well as The brush component includes a base fabric and multiple fiber yarns woven into the base fabric. These fiber yarns have trailing edges extending from the base fabric and contact the surface of the image carrier component in the rotational direction of the image carrier component, downstream of the transfer section and upstream of the charged section. Specifically, when the 1mm area from the tail edge of the multiple fiber yarns that will contact the image-carrying component is immersed in water at 20°C for 10 seconds, the water absorption per unit area of ​​the brush component is 2.2 mg / mm². 2 Or larger.

2. The image forming apparatus according to claim 1, wherein, The water absorption per unit area is a value obtained by dividing the water content of the brush component by the contact area between the brush component and the image carrier component, with the virtual surface of the trailing edge of the multiple fiber yarns, including the multi-fiber yarns abutting the image carrier component, being kept parallel to the water surface at 20°C, and then the multi-fiber yarns being brought close to the water surface, and then only a 1 mm area from the trailing edge of the multi-fiber yarns being immersed in the water for 10 seconds.

3. The image forming apparatus according to claim 1 or 2, wherein, The fiber yarn material has a water absorption rate of 0.5% or higher as measured according to the American Society for Testing and Materials (ASTM) D570 test procedure.

4. The image forming apparatus according to claim 3, wherein, The multi-fiber yarn has a density of 240kF or higher.

5. The image forming apparatus according to claim 1 or 2, wherein, The fiber yarn material has a water absorption rate of 1.1% or higher as measured according to the ASTM D570 test procedure.

6. The image forming apparatus according to claim 5, wherein, The multi-fiber yarn has a density of 150kF or higher.

7. The image forming apparatus according to claim 1 or 2, further comprising: The brush voltage application unit is configured to apply a brush voltage to the brush component; as well as The control unit is configured to control the brush voltage application unit. The brush component is a conductive brush, and The control unit controls the brush voltage application unit so that during the execution of the image forming operation, the brush voltage applied to the conductive brush by the brush voltage application unit has the same polarity as the surface potential of the image carrier component, and the absolute value of the brush voltage is greater than the absolute value of the surface potential of the image carrier component.

8. The image forming apparatus according to claim 7, further comprising: A transfer voltage application unit, controlled by a control unit, applies a transfer voltage to the transfer member. The control unit controls the transfer voltage application unit so that the brush voltage has the same polarity as the surface potential of the image carrier member at the transfer section, and the surface potential of the image carrier member at the transfer section is lower than the brush voltage.

9. The image forming apparatus according to claim 1 or 2, wherein, The developing component recovers toner that was not transferred from the image carrier component to the transfer material and remained on the image carrier component at the transfer section.

10. The image forming apparatus according to claim 1 or 2, wherein, Toner is a single-component developer.

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