Image-forming device

Abstract

To suppress an external additive interposed between a sheet provided while abutting on a photoreceptor and the photoreceptor from intercepting an optical path of an exposing device when the photoreceptor is rotated inversely.SOLUTION: An image-forming device includes: a photoreceptor; an exposing device; a cleaning member provided while abutting on the photoreceptor; a drive section for rotatably driving the photoreceptor in a first rotary direction in a development operation; a control section capable of executing a mode for controlling the drive section so as to rotatably driving the photoreceptor in a second rotary direction opposite to the first rotary direction in a non-development operation; a sheet provided while abutting on the photoreceptor in a downstream side of a position in which a cleaning member abuts on the photoreceptor regarding the first rotary direction and in an upstream side of a development position; and a collecting section provided while opposing the photoreceptor without any contact in a lower portion of a gravity direction relative to the contact position in which the sheet abuts on the photoreceptor, and in an area between a contact position, and a position that is reached when the photoreceptor is rotatably drive in the second rotary direction with the contact position as a starting point in a mode regarding a horizontal direction.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an image forming apparatus including a developing device that develops an electrostatic latent image formed on an image carrier with a developer containing toner and a carrier.

Background Art

[0002] In an image forming apparatus using an electrophotographic method or the like, an electrostatic latent image formed on a photosensitive drum (image carrier) is developed into a toner image by a developing device. As such a developing device, one using a two-component developer containing toner and a carrier has been conventionally used.

[0003] The developing device includes a developing container that stores a developer containing toner and a carrier, a rotatable developing sleeve (developing rotating body) that carries the developer to develop the electrostatic latent image formed on the photosensitive drum, and a developer regulating member that regulates the amount of the developer carried on the developing sleeve.

[0004] The developer conveyed to a developing position (developing region) where the electrostatic latent image is developed by the developing sleeve forms magnetic spikes by standing up in the developing region. Then, the toner in the developer supplied from the magnetic spikes in the developing region is supplied to the electrostatic latent image, and the electrostatic latent image is developed into a toner image. On the other hand, a part of the toner in the developer supplied from the magnetic spikes in the developing region may scatter from the developing region without adhering to the electrostatic latent image. Therefore, particularly in the space downward in the gravitational direction from the developing region, the toner floating in the space tends to relatively increase due to the self-weight of the toner scattered from the developing region.

[0005] Therefore, the developing device described in Patent Document 1 includes a developer regulating member, a sheet member that contacts the photosensitive drum and captures the toner scattered downward in the gravitational direction from the developing region, and a sheet support member that supports the sheet member. Thereby, the space downward in the gravitational direction from the developing region is made into a closed space, and the toner scattered from the developing region without adhering to the electrostatic latent image in the developing region is captured.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The photosensitive drum transfers the toner image attached to the electrostatic latent image to the intermediate transfer belt. The transfer residual toner that has not been transferred to the intermediate transfer belt is scraped off by a cleaning blade pressed against the photosensitive drum. The cleaning blade is disposed such that the tip-side edge portion thereof contacts the photosensitive drum with a predetermined pressing force in the counterclockwise direction in the normal rotation direction during image formation on the photosensitive drum.

[0008] Since the tip-side edge portion of the cleaning blade contacts the photosensitive drum with a contact pressure and in the counterclockwise direction with respect to the normal rotation direction of the photosensitive drum, it is dragged by the photosensitive drum, causing distortion and adhering closely to the photosensitive drum. In front of the tip-side edge portion of the cleaning blade, toner is blocked by the cleaning blade, so toner accumulates. If the photosensitive drum is left in a rotation-stopped state with such a toner accumulation, the toner aggregates and becomes fixed on the photosensitive drum surface, and may pass through the edge portion of the cleaning blade when the photosensitive drum starts to rotate in the normal direction.

[0009] Therefore, the image forming apparatus of Patent Document 2 executes a refresh mode in which the photosensitive drum is rotated in a direction opposite to that during image formation. Thereby, the variation in the amount of abrasive (externally added agent mixed in the toner) at the edge portion of the cleaning blade is suppressed, and the aggregation of toner at the contact portion between the cleaning blade and the photosensitive drum is suppressed.

[0010] On the other hand, in the case of the configuration described in Patent Document 1, since the sheet member provided in the developing device is in contact with the photosensitive drum, fine external additives contained in the toner that has passed through the cleaning blade may adhere to the sheet member. The adhered external additives are interposed between the sheet member and the surface of the photosensitive drum. Therefore, in the configuration described in Patent Document 1, when the photosensitive drum is rotated in the reverse direction in the cleaning mode, there is a risk that the external additives will fall downward in the direction of gravity and block the optical path of the exposure member that exposes the photosensitive drum.

[0011] The present invention has been made in view of the above problems. An object of the present invention is to provide an image forming apparatus capable of suppressing the external additives interposed between the sheet provided in contact with the photoreceptor and the photoreceptor from blocking the optical path of the exposure device when the photoreceptor rotates in the reverse direction.

Means for Solving the Problems

[0012] To achieve the above object, an image forming apparatus according to an aspect of the present invention has the following configuration. That is, a rotatable photoreceptor, an exposure device that exposes the photoreceptor to form an electrostatic latent image on the photoreceptor, a developing container that houses a developer containing toner and a carrier, a developer carrier that carries and transports the developer to a developing position where the electrostatic latent image formed on the photoreceptor by the exposure device is developed, a cleaning member provided in contact with the photoreceptor to clean the photoreceptor, a driving unit that rotationally drives the photoreceptor in a first rotation direction during a developing operation in which the developing device develops the electrostatic latent image formed on the photoreceptor, and a control unit capable of executing a mode of controlling the driving unit so that the photoreceptor is rotationally driven in a second rotation direction opposite to the first rotation direction during a non-developing operation in which the developing operation is not performed. A sheet provided in contact with the photoreceptor at a position downstream of the position where the cleaning member is in contact with the photoreceptor and upstream of the developing position with respect to the first rotation direction, and a collecting unit provided to face the photoreceptor non-contactly in a region between a position below the contact position where the sheet is in contact with the photoreceptor in the gravitational direction and a position reached when the photoreceptor is rotationally driven in the second rotation direction starting from the contact position in the horizontal direction. It is characterized by comprising the above.

[0013] In addition, an image forming apparatus according to another aspect of the present invention for achieving the above object has the following configuration. That is, a rotatable photoreceptor, an exposure device for exposing the photoreceptor to form an electrostatic latent image on the photoreceptor, a developing container for storing a developer containing toner and a carrier, a developer carrier for carrying and transporting the developer to a developing position for developing the electrostatic latent image formed on the photoreceptor by the exposure device, a developing device having the above, a cleaning member provided in contact with the photoreceptor for cleaning the photoreceptor, a driving unit for rotationally driving the photoreceptor in a first rotation direction during a developing operation in which the developing device develops the electrostatic latent image formed on the photoreceptor, and a control unit capable of executing a mode for controlling the driving unit to perform a plurality of sets of rotating the photoreceptor in the first rotation direction after rotationally driving the photoreceptor in a second rotation direction opposite to the first rotation direction during a non-developing operation in which the developing operation is not performed, a sheet provided in contact with the photoreceptor downstream of a position where the cleaning member is in contact with the photoreceptor and upstream of the developing position with respect to the first rotation direction, and a collecting unit provided to face the photoreceptor without contact in a region between a contact position where the sheet is in contact with the photoreceptor and a position that reaches the most downstream with respect to the second rotation direction from the contact position when the photoreceptor is rotationally driven in the second rotation direction starting from the contact position in the mode, and below the contact position in the gravitational direction and with respect to the horizontal direction.

Advantages of the Invention

[0014] According to the present invention, it is possible to suppress an external additive interposed between a sheet provided in contact with the photoreceptor and the photoreceptor from blocking the optical path of the exposure device when the photoreceptor rotates in the reverse direction.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

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Figure 8

Figure 9

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention according to the claims, and not all combinations of the features described in the first embodiment are essential for the solution means of the present invention. The present invention can be implemented in various applications such as printers, various printing machines, copiers, FAX, multifunction machines, etc.

[0017] [First Embodiment] (Configuration of Image Forming Apparatus) FIG. 1 is a cross-sectional view of the image forming apparatus 100 in the first embodiment from the front direction.

[0018] The image forming apparatus 100 is a tandem type - intermediate transfer type four-color full-color printer using an electrophotographic process, and forms a toner image on a sheet S based on image information input from an external host device such as a personal computer to a control circuit unit.

[0019] In the cross-sectional view of FIG. 1, an image forming apparatus 100 includes an image forming unit that sequentially forms four-color toner images of yellow (Y), magenta (M), cyan (C), and black (K) added thereto, and is disposed at a substantially central portion of the image forming apparatus 100.

[0020] The image forming units for forming toner images of each color are substantially common. To avoid complexity in the drawing, the magenta image forming unit is typically denoted by reference numeral U, and the description of the other image forming units is omitted.

[0021] The four image forming units U each include a drum cartridge 3 as a photosensitive member unit including a rotary drum type electrophotographic photosensitive member (hereinafter referred to as photosensitive drum 1 (1Y, 1M, 1C, 1K)) as an image carrier. In this embodiment, the photosensitive drum 1 (1Y, 1M, 1C, 1K) is a metal tube on a cylinder having a diameter of φ30 mm. Further, in this embodiment, the process speed, which is the rotational speed of the photosensitive drum 1 (1Y, 1M, 1C, 1K), is 264 mm / sec. The four image forming units U also include a developing cartridge (hereinafter referred to as developing device 5) as a developing unit including a rotatable developing sleeve 51 (developing rotator) for developing the toner image. Thus, the four image forming units U are composed of two units (drum cartridge 3 as a photosensitive member unit and developing device 5 as a developing unit) that can be replaced and attached / detached.

[0022] The drum cartridge 3 includes a rotatable photosensitive drum 1, a charging roller 31 for charging the photosensitive drum 1, and a cleaning blade (cleaning member) that contacts the photosensitive drum 1 to clean the surface of the photosensitive drum 1.

[0023] The developing device 5 includes, in addition to the developing sleeve 51, a first conveying screw 59 that supplies toner to the developing sleeve 51 and stirs the toner.

[0024] An exposure device 4 including an LED light emitting element and an irradiation unit (not shown) that irradiates the LED emitted by the LED light emitting element is disposed between the drum cartridge 3 and the developing device 5.

[0025] Also, above the four image forming units U, an intermediate transfer belt 8 as an intermediate transfer member is disposed. Also, below the four image forming units U, a sheet cassette 12 is disposed. The sheet cassette 12 includes two cassettes, a cassette 12A disposed in the upper stage and a cassette 12B disposed in the lower stage. Four primary transfer rollers 6 are disposed opposite to the photosensitive drums 1 of respective colors with respect to the intermediate transfer belt 8.

[0026] Furthermore, toner bottles indicated by 22Y·22M·22C·22K are disposed above the intermediate transfer belt 8. This is a toner bottle unit that can be detachably exchanged and houses replenishing toner for the four image forming units U. Thereby, appropriate amounts of toner are replenished in a timely manner from the corresponding toner bottles to the developing sleeves 5 provided in the four image forming units U by a toner supply mechanism.

[0027] (Image forming process) In the image forming process, it is necessary to form a latent image on the photosensitive drums 1 of these four image forming units U. As a preparatory operation, a high voltage is applied to a charging roller 3 pressed against the photosensitive drum 1, and the surface thereof is uniformly charged as the photosensitive drum 1 rotates. In this embodiment, the surface of the photosensitive drum 1 is uniformly charged to -600V.

[0028] Next, toner charged inside the developing device 24 is uniformly coated on the surface of the developing sleeve 5. Here, inside the developing device 24, the toner is circulated and conveyed at high speed by a first conveying screw 59. The rotation speed of the first conveying screw 59 is relatively very high with respect to the rotation speeds of the developing sleeve 5 and the photosensitive drum 1, so that the coating on the developing sleeve 5 can be performed uniformly without unevenness.

[0029] Then, by the light emission and irradiation of the exposure device 4 disposed between the drum cartridge 32 and the developing device 24, an electrostatic latent image is formed due to the potential change on the surface of the photosensitive drum 1. By applying a high voltage to the developing sleeve 5 to provide a potential difference between the developing sleeve 5 and the photosensitive drum 1, the toner on the developing sleeve 5 develops the latent image on the photosensitive drum 1 as a toner image.

[0030] This toner image on the photosensitive drum 1 is primarily transferred to the surface of the intermediate transfer belt 8 in the order of the above respective colors according to the rotation of the intermediate transfer belt 8. Thereby, a toner image with four-color superposition of Y+M+C+K is formed on the intermediate transfer belt 8.

[0031] Inside the main body of the image forming apparatus 100 on the right side, a sheet conveyance path for conveying the sheet S from bottom to top is provided. In this conveyance path, a pair of feed rollers 13, a pair of registration rollers 15, a secondary transfer roller 16, a fixing device 19, and a pair of discharge rollers 20 are arranged in order from the lower side to the upper side. The secondary transfer roller 16 abuts against the belt driving roller 10 on the right side of the intermediate transfer belt 8 with a predetermined pressing force via the intermediate transfer belt 8, and forms a secondary transfer nip portion 17 with the intermediate transfer belt 8.

[0032] Here, at a predetermined control timing, the pair of feed rollers 13 is driven, and sheets (recording materials, papers) S are separated and fed one by one from the sheet cassette 12 and introduced into the sheet conveyance path. Then, by the pair of registration rollers 15, the sheet S is introduced into the secondary transfer nip portion 17 at a predetermined control timing and nipped and conveyed. Thereby, at the secondary transfer nip portion 17, the four-color superposed toner image on the intermediate transfer belt 8 is collectively secondarily transferred to the sheet S, and an unfixed toner image is formed on the sheet S. The toner remaining without being secondarily transferred from the intermediate transfer belt 8 to the sheet S is scraped off by the intermediate transfer belt cleaning blade 60 in contact with the intermediate transfer belt 8. The intermediate transfer belt cleaning blade 60 serves as a cleaning member for cleaning the surface of the intermediate transfer belt 8.

[0033] The sheet S that exits the secondary transfer nip portion 17 is introduced into the fixing device 19 and undergoes a fixing process of the toner image by heat and pressure. The sheet S that exits the fixing device 19 is discharged as an image formation product to a discharge tray 21 disposed above the toner bottle unit 22 by a pair of discharge rollers 20.

[0034] (Configuration of the developing device) Next, the detailed configuration of the developing device 24 will be described with reference to the cross-sectional view of FIG. 2.

[0035] The developing device 24 is a developing container 2 that houses a developer (two-component developer) composed of a magnetic carrier and a non-magnetic toner. The weight ratio of the non-magnetic toner in the two-component developer, that is, the toner concentration, is approximately 10 wt%. This ratio should be appropriately adjusted according to the charge amount of the toner, the carrier particle size, or the configuration and usage conditions of the image forming apparatus, and does not necessarily have to follow this numerical value.

[0036] As the magnetic carrier, for example, metals such as iron, nickel, cobalt, manganese, chromium, rare earths, etc. with surface oxidation or non-oxidation, and their alloys, or oxide ferrites, etc. can be preferably used, and the manufacturing method of these magnetic particles is not particularly limited. As the magnetic carrier of this embodiment, ferrite particles coated with silicone resin are used. This magnetic carrier has a saturation magnetization of 294 am2 / kg with respect to an applied magnetic field of 240 kA / m and a specific resistance of 1×107~8 Ω·cm at an electric field strength of 3000 V / cm. In addition, as the magnetic carrier, a resin magnetic carrier manufactured by a polymerization method using a binder resin, a magnetic metal oxide, and a non-magnetic metal oxide as starting materials may also be used.

[0037] The volume average particle size of the magnetic carrier is measured using a laser diffraction particle size distribution measuring device HEROS (manufactured by JEOL Ltd.) by logarithmically dividing the particle size range of 0.5 to 350 μm on a volume basis into 32 parts, measuring the number of particles in each channel, and using the median diameter of 50% of the volume as the volume average particle size from the measurement results. The volume average particle size of the magnetic carrier in this embodiment is 50 μm.

[0038] As the non-magnetic toner, it is composed of at least a binder, a colorant, and a charge control agent. In this embodiment, a styrene-acrylic resin is used as the binder resin, but resins such as styrene-based, polyester-based, and polyethylene can also be used. As the colorant, phthalocyanine blue is used in this embodiment, but carbon black, chrome yellow, Hansa yellow, benzidine yellow, threne yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, Vulcan orange, Watchung red, permanent red, brilliant carmine 3B, brilliant carmine 6B, Daypon oil red, pyrazolone red, resorcinol red, rhodamine B lake, lake red C, rose bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine green, malachite green oxalate, and other various pigments and various dyes can be used. The colorant may be used alone or in combination of multiple types.

[0039] As the charge control agent, a charge control agent for reinforcement may be contained as necessary. All known charge control agents for reinforcement can be used. For example, nigrosine-based dyes, triphenylmethane-based dyes, chromium-containing metal complex dyes, molybdic acid chelate pigments, rhodamine-based dyes, alkoxyamines, quaternary ammonium salts (including fluorine-modified quaternary ammonium salts), alkylamides, simple substances or compounds of phosphorus, simple substances or compounds of tungsten, fluorine-based activators, metal salts of salicylic acid, and metal salts of salicylic acid derivatives.

[0040] Also, the non-magnetic toner may contain wax or external additives. The wax is contained to improve the releasability from the fixing member and the fixability during fixing. As the wax, paraffin wax, carnauba wax, polyolefin, etc. can be used, and it is used by being kneaded and dispersed in the binder resin. In this embodiment, a resin obtained by kneading and dispersing a binder, a colorant, a charge control agent, and wax was pulverized by a mechanical pulverizer and used.

[0041] Examples of the external additive particles include those obtained by subjecting amorphous silica to a hydrophobic treatment, or inorganic oxide fine particles such as titanium oxide and titanium compounds. By externally adding these fine particles to the toner base, it is suitable to control the powder fluidity and charge amount of the toner. The particle size of the external additive particles is desirably about 1 nm to 100 nm. In this example, titanium oxide with an average particle size of 50 nm was externally added at 0.5 wt% by weight ratio, and amorphous silica with average particle sizes of 2 nm and 100 nm was externally added at 0.5 wt% and 1.0 wt% respectively.

[0042] Further, the developing device 24 has a developing sleeve 5 as a developer carrier that carries and conveys the developer in the developing container 2. The surface of the developing sleeve 5 is rotatably held, while a magnet roll 54 composed of a plurality of magnetic poles (lifting pole S3, regulating pole N1, developing pole S1, conveying pole N2, stripping pole S2) is non-rotatably arranged inside. In this example, the outer diameter of the developing sleeve 5 is φ18 mm.

[0043] The developing container 2 is partitioned by a partition wall 51 into a first conveyance path (agitation chamber) 52 as a first chamber and a second conveyance path (developing chamber) 53 as a second chamber, and the first conveyance path 52 and the second conveyance path 53 communicate with each other through communication ports at both ends. Thereby, a circulation path for the developer is formed by the first conveyance path 52 and the second conveyance path 53.

[0044] Two screw members are provided in the developing container 2 as conveyance members for agitating and conveying the developer. That is, the first conveyance path 52 is provided with a first conveyance screw 59, and the second conveyance path 53 is provided with a second conveyance screw (second conveyance part) 58. The first conveyance screw 59 has a rotation shaft 59a and blades 59b spirally provided around the rotation shaft 59a (on the rotation shaft). The second conveyance screw 58 has a rotation shaft 58a and blades 58b spirally provided around the rotation shaft 58a (on the rotation shaft). Note that the first conveyance screw 59 is a screw that agitates the developer and supplies the developer onto the developing sleeve 5.

[0045] When the first conveying screw 59 rotates around the rotation shaft 59a, the developer in the first conveying path 52 is conveyed in the first direction, which is one side in the longitudinal direction of the developing device 24 (the axial direction of the rotation shaft 59a), by the spiral blades 59b. When the second conveying screw 58 rotates around the rotation shaft 58a, the developer in the second conveying path 53 is conveyed in the second direction (the direction opposite to the first direction), which is the other side in the longitudinal direction of the developing device 24 (the axial direction of the rotation shaft 58a), by the spiral blades 58b. Thereby, the developer is circulated between the first conveying path 52 and the second conveying path 53.

[0046] The developer in the second conveying path 53 is lifted by the second conveying screw 58 installed below the developing sleeve 5 inside the second conveying path 53 into the magnetic force range of the lifting electrode S2 and is carried on the surface of the developing sleeve 5. The developer carried on the surface of the developing sleeve 5 is conveyed as the developing sleeve 5 rotates. In this embodiment, the rotation speed of the developing sleeve 5 is 475 mm / sec.

[0047] Near the regulating pole N1, a regulating blade 23 (developer regulating member) is arranged with a predetermined gap from the surface of the developing sleeve 5 as a member for forming a thin layer of the developer. That is, the regulating blade 23 is arranged to face the developing sleeve 5 in a non-contact manner. Generally, the gap between the developing sleeve 5 and the regulating blade 23 is set to about 200 to 500 μm. The wider the gap, the more the amount of the developer carried on the developing sleeve 5.

[0048] The conveyed developer forms a magnetic brush at the regulating pole N1, and a desired amount of the developer is formed into a thin layer on the surface of the developing sleeve 5 by the regulating blade 23 arranged at a predetermined interval from the developing sleeve 5. In this embodiment, the gap between the developing sleeve 5 and the regulating blade 23 is set to 280 μm, and the amount of the developer conveyed to the developing region R is regulated to a mass per unit area (M / S) of 28 mg / cm 2 Thereafter, the developer conveyed to the facing portion of the photosensitive drum 1 forms a magnetic brush again at the developing pole S1 and forms a developing nip with the photosensitive drum 1.

[0049] As described above, while the surface of the photosensitive drum 1 is charged to a constant potential by the charging roller 3, the image portion is exposed by the exposure device 4 to form an exposure potential. On the other hand, a developing bias is applied to the developing sleeve 5 through a high-voltage circuit. The developing bias is, for example, a bias in which a rectangular AC waveform is superimposed on a DC waveform of a constant voltage. The toner charged in the developing device 24 obtains a driving force due to the potential difference between the developing bias and the surface potential of the photosensitive drum 1 within the developing nip (developing region R) including the developing position where the electrostatic latent image on the surface of the photosensitive drum 1 is developed by the developing sleeve 5, and adheres to the image portion, thereby completing the developing process. In this embodiment, a voltage obtained by superimposing an AC component having a frequency of 10 kHz and a peak-to-peak voltage Vpp of 1.6 kV and a DC component (Vdc) of -450 V is applied from a developing high-voltage power supply (not shown), but the present invention is not limited to this numerical value.

[0050] The carrier and the toner that has not been developed are further conveyed downstream in the rotation direction of the developing sleeve 5 by the magnetic force of the conveying pole N2. Then, the carrier and the toner that has not been developed lose the magnetic restraint force in the zero Gaussian band (a region where the radial magnetic flux density of the developing sleeve 5 becomes 10 mT or less) formed between the stripping pole S2 and the pumping pole S3, and are recovered again into the second conveying path 53.

[0051] When the developing operation is performed, only the toner among the developer is consumed, so the weight ratio (T / D ratio) of the developer to the toner decreases. Therefore, the T / D ratio is controlled to a predetermined value by performing a toner replenishment operation. In the first embodiment, the predetermined T / D ratio is set to 8%.

[0052] Toner replenishment is performed through a toner replenishment port provided in the developing container 2. In the first embodiment, the toner replenishment port is provided above the upstream end of the first conveying screw 59 in the first direction and outside the conveying path of the first conveying path 52. However, the position of the toner replenishment port can be installed in various locations depending on the main body configuration of the image forming apparatus 100 and the like, and is not limited to this location. The replenished toner circulates while being agitated and conveyed together with the developer by the first conveying screw 59 and the second conveying screw 58 through the first conveying path 52 and the second conveying path 53.

[0053] (Configuration of Drum Cartridge) Next, the detailed configuration of the drum cartridge 32 will be described with reference to the cross-sectional view of FIG. 3.

[0054] The drum cartridge 32 has a configuration in which the photosensitive drum 1, a charging roller (not shown), a cleaning roller (not shown) as a cleaning member for cleaning the surface of the charging roller, and a cleaning blade 14 are integrally held by a drum container 11 as a frame body. Further, the drum cartridge 32 is configured to be detachable from the image forming apparatus 100 by sliding the drum cartridge 32 along the longitudinal direction from the apparatus main body of the image forming apparatus 100, and the drum cartridge 32 can be replaced for maintenance and the like.

[0055] In the drum container 11, the photosensitive drum 1 is rotatably held about a rotation axis via a bearing. The photosensitive drum 1 is provided with a coupling for receiving a driving force from a motor (driving unit) as a driving source provided in the apparatus main body of the image forming apparatus 100 and rotating in a state of being mounted on the image forming apparatus 100.

[0056] Further, in the drum container 11, a cleaning blade 14 is fixedly provided so as to abut against the surface of the photosensitive drum 1 in a counter direction to the rotation direction of the photosensitive drum 1 during the image forming operation. The cleaning blade 14 serves as a cleaning member for cleaning the surface of the photosensitive drum 1.

[0057] Further, in the drum cartridge 32, in the vicinity of the cleaning blade 14, a recovery unit 62 for recovering the transfer residual toner removed from the surface of the photosensitive drum 1 by the cleaning blade 14 is provided. Also, in the drum cartridge 32, a toner transfer screw 64 is provided as a transfer unit for transferring the toner recovered by the recovery unit 62 to the outside of the drum cartridge 32. The toner transferred outside the drum cartridge 32 by the toner transfer screw 64 is recovered in a recovered toner container provided in the apparatus main body of the image forming apparatus 100.

[0058] At the longitudinal end of the photosensitive drum 1, a gear is provided as a rotating member fixed so as to rotate integrally with the photosensitive drum 1 around the rotation axis of the photosensitive drum 1. When the photosensitive drum 1 rotates, the rotational force of the gear that rotates integrally is transmitted to the toner transfer screw 64, causing the toner transfer screw 64 to rotate, and the transfer residual toner recovered by the recovery unit 62 can be transferred outside the drum cartridge 32.

[0059] (Sheet member provided in the developing device) Next, the scattering of toner from the developing region R will be described with reference to FIG. 4. FIG. 4 is a cross-sectional view showing the arrangement of the sheet member provided in the developing device 24 according to the first embodiment.

[0060] During the image forming operation, as the developing sleeve 5 rotates, an air flow is generated on the surface of the developing sleeve 5. When the layer thickness of the developer passing between the developing sleeve 5 and the regulating blade 23 is regulated by the regulating blade 23, the toner held on the surface of the carrier by electrostatic force may ride on this air flow and be released from the surface of the carrier. As a result, in the region downstream of the position where the developing sleeve 5 is closest to the regulating blade 23 and upstream of the position where the developing sleeve 5 is closest to the photosensitive drum 1 with respect to the rotation direction E of the developing sleeve 5, the amount of toner scattering tends to increase. Note that the rotation direction E of the developing sleeve 5 is the normal rotation direction, which is the rotation direction of the developing sleeve 5 during the image forming operation. Also, the position where the developing sleeve 5 is closest to the photosensitive drum 1 corresponds to the developing position where the electrostatic latent image on the surface of the photosensitive drum 1 is developed by the developing sleeve 5.

[0061] Therefore, in the first embodiment, a first sheet member 25 for suppressing toner scattering is attached to a sheet attaching member 30 attached to the regulating blade 23.

[0062] The first sheet member 25 is a sheet material for capturing the toner scattered when the layer thickness of the developer passing between the developing sleeve 5 and the regulating blade 23 is regulated by the regulating blade 23. The first sheet member 25 has flexibility and is arranged in contact with the photosensitive drum 1 so as to face the photosensitive drum 1. In the first embodiment, a PET sheet having a thickness of 23 μm is adopted as the first sheet member 25.

[0063] As shown in FIG. 4, the first sheet member 25 is arranged to seal the region upstream of the position where the developing sleeve 5 is closest to the photosensitive drum 1 (developing position) with respect to the rotation direction A (normal rotation direction) of the photosensitive drum 1 during the image forming operation. Also, the first sheet member is provided in contact with the photosensitive drum 1 downstream of the developing position and upstream of the position where the cleaning blade 14 is in contact with the photosensitive drum 1 with respect to the rotation direction A (normal rotation direction) of the photosensitive drum 1.

[0064] And the first sheet member 25 has the other end side (fixed end) of the first sheet member 25 attached to the sheet attaching member 30 so that the gap with the photosensitive drum 1 becomes narrower from the upstream to the downstream in the rotation direction A of the photosensitive drum 1. Also, the first sheet member 25 has the other end side (fixed end) of the first sheet member 25 attached to the sheet attaching member 30 so that the free end on the side opposite to the fixed end of the first sheet member 25 contacts the photosensitive drum 1.

[0065] Further, the first sheet member 25 is provided to face the developing sleeve 5 over substantially the entire region of the developing sleeve 5 corresponding to the maximum image region among the image regions capable of forming an image on the surface of the photosensitive drum 1 with respect to the rotation axis direction of the developing sleeve 5.

[0066] Also, as shown in FIG. 4, with respect to the rotation direction E of the developing sleeve 5, a third sheet member 27 is provided which is arranged in contact with the developing sleeve 5 downstream of the position where the regulating blade 23 is closest to the developing sleeve 5 and upstream of the developing position. This is because when the developer passes through the gap between the regulating blade 23 and the developing sleeve 5, toner tends to scatter easily, so the third sheet member 27 is provided to play a role of capturing the toner. As shown in FIG. 4, the third sheet member 27 is attached to the sheet attaching member 30 in the same manner as the first sheet member 25.

[0067] In the first embodiment, a urethane sheet having a thickness of 100 μm is adopted as the third sheet member 27. As described above, in the first embodiment, a PET sheet having a thickness of 23 μm is adopted as the first sheet member 25. That is, the first sheet member 25 in contact with the photosensitive drum 1 has a smaller sheet thickness than the third sheet member 27 in contact with the developing sleeve 5. Thus, the contact pressure when the first sheet member 25 contacts the photosensitive drum 1 is set to be smaller than the contact pressure when the third sheet member 27 contacts the developing sleeve 5.

[0068] (Cleaning mode) Figs. 5(a) to 5(d) are schematic diagrams showing an enlarged view of the tip-side edge portion of the cleaning blade 14 when the photosensitive drum 1 is rotated in the normal direction. Note that Figs. 5(a), 5(b), 5(c), and 5(d) show the time series in this order. In Figs. 5(a) to 5(d), 1 represents the photosensitive drum, 14 represents the cleaning blade, and W represents the contact portion between the cleaning blade 14 and the photosensitive drum 1.

[0069] Fig. 5(a) shows the contact state of the cleaning blade 14 with respect to the photosensitive drum 1 when the image forming operation is being performed, and the photosensitive drum 1 is being driven to rotate in the normal direction indicated by the arrow A. The cleaning blade 14 is disposed such that the tip-side edge portion of the cleaning blade 14 is brought into contact with the photosensitive drum 1 with a predetermined pressing force.

[0070] That is, since the tip-side edge portion of the cleaning blade 14 is in contact with the photosensitive drum 1 with a contact pressure and in a counter direction to the normal rotation direction of the photosensitive drum 1, it is dragged by the photosensitive drum 1 and distorted, thereby adhering closely to the photosensitive drum 1. The surface of the photosensitive drum 1 is wiped by the tip-side edge portion of the cleaning blade 14 in this contact state, and the transferred residual toner is scraped off from the photosensitive drum 1.

[0071] On the other hand, in front of the tip-side edge portion of the cleaning blade 14, the toner t is blocked by the cleaning blade 14, so that the toner t accumulates (see Fig. 5(a)). If the photosensitive drum 1 is left in a rotation-stopped state with such an accumulation of the toner t, the toner t aggregates and becomes fixed to the surface of the photosensitive drum 1 (see Figs. 5(b) and 5(c)). As a result, when the photosensitive drum 1 is started to rotate in the normal direction next time, the toner t may pass through the tip-side edge portion of the cleaning blade 14 (see Fig. 5(d)).

[0072] Therefore, in the first embodiment, a mode of rotationally driving the photosensitive drum 1 in a direction opposite to the normal rotation direction (the direction of arrow A) (hereinafter referred to as the cleaning mode) is executed. Thereby, aggregation of the toner t at the contact portion between the cleaning blade 14 and the photosensitive drum 1 is suppressed.

[0073] Figs. 6(a) to 6(d) are schematic enlarged views of the tip-side edge portion of the cleaning blade 14 when the photosensitive drum 1 is rotated in the reverse direction. Note that Figs. 6(a), 6(b), 6(c), and 6(d) represent the time series in this order. As shown in Fig. 6(c), the photosensitive drum 1 is rotated in a direction B opposite to the normal rotation direction A during image formation. Thereby, the toner t accumulated in front of the edge portion of the cleaning blade 14 is removed from the tip-side edge portion of the cleaning blade 14 before it aggregates, and the photosensitive drum 1 is brought into a stopped state.

[0074] Furthermore, as shown in Fig. 6(d), the photosensitive drum 1 is rotated again in the normal rotation direction A during image formation. At this time, the driving distance for rotating the photosensitive drum 1 in the normal rotation direction A is made shorter than the driving distance for rotating it in the reverse direction B. Thereby, the cleaning blade 14 is stopped in the same contact state as during image formation, and the accumulation of the toner t stops upstream of the contact portion of the cleaning blade 14 with respect to the normal rotation direction A. As shown in Fig. 6(c), when left in a state where the distortion is released, when the photosensitive drum 1 rotates in the normal rotation direction A during the next image formation, the tip edge shape of the cleaning blade 14 does not become a state where distortion occurs as shown in Fig. 6(a). In the case of a state where distortion occurs as shown in Fig. 6(a), there is a possibility that the toner t may slip through or the cleaning blade 14 may make a noise. For this reason, at the end of image formation, the photosensitive drum 1 is stopped in a state of being driven in the normal rotation direction A.

[0075] The transfer residual toner on the photosensitive drum 1 is scraped off by the cleaning blade 14. However, since the external additive g externally added to the toner in the developer is finer than the toner t, a part of it may slip through the cleaning blade 14.

[0076] Here, the details of the external additive g in the toner t described above will be explained. The developer used in this example is a dry two-component developer containing toner t added with negatively charged fine particles (external additive g) having the same polarity as the charging polarity of the toner t and a carrier. In this example, the external additive g contains at least titanium oxide and amorphous silica (silica) in order to suitably control the powder flow characteristics and charging characteristics of the toner.

[0077] In the developing process of developing the electrostatic latent image formed on the photosensitive drum 1 using this developer, among the developer carried on the developing sleeve 5, the toner t is mainly developed on the image portion (bright portion potential portion of the electrostatic latent image). At this time, the negatively charged external additive g having the same polarity as the charging polarity of the toner t added to the toner t is also developed simultaneously. In addition, some of the external additives added to the toner are separated from the toner t because the adhesion force with the toner t becomes small due to being stirred in the developing container 2, and there are also external additives that separate from the toner t.

[0078] The toner t and the external additive g developed on the photosensitive drum 1 are primarily transferred onto the intermediate transfer belt 8 in the transfer process. However, a part of the toner t and the external additive g having a small particle size and a large non-electrostatic adhesion force remain on the photosensitive drum 1 without being transferred.

[0079] Subsequently, although the residual transfer toner and the external additive that have reached the cleaning process are cleaned by the cleaning blade 14 for the residual transfer toner, the external additive g remains on the photosensitive drum 1 without being completely cleaned because of its small particle size and large adhesion force with the photosensitive drum 1. As a result, the external additive g that has passed through the cleaning blade 14 rotates with the photosensitive drum 1 while adhering to the surface of the photosensitive drum 1, passes through the contact portion where the charging roller contacts the photosensitive drum 1, and reaches the developing nip formed between the developing sleeve 5 and the photosensitive drum 1.

[0080] Here, the behavior of the external additive g on the first sheet member 25 when the photosensitive drum 1 rotates in the reverse direction will be described with reference to the schematic diagrams of FIGS. 7(a) and 7(b). Note that FIGS. 7(a) and 7(b) show the time series in that order.

[0081] The external additive g that has passed through the cleaning blade 14 rotates together with the photosensitive drum 1 while adhering to the surface of the photosensitive drum 1. At this time, since the first sheet member 25 is in contact with the photosensitive drum 1, the external additive g adhering to the surface of the photosensitive drum 1 may adhere to the surface of the first sheet member 25. When the photosensitive drum 1 rotates in the reverse rotation direction B with the external additive g adhering to the surface of the first sheet member 25, there is a risk that the external additive g will fall downward in the gravitational direction and scatter onto the optical path of the exposure device 4.

[0082] Therefore, in the first embodiment, in addition to providing the first sheet member 25 that contacts the photosensitive drum 1, a second sheet member 26 (collection sheet) that faces the photosensitive drum 1 without contact is provided. The second sheet member 26 is arranged downstream of the exposure position where the surface of the photosensitive drum 1 is exposed by the exposure device 4 and upstream of the position where the first sheet member 25 contacts the surface of the photosensitive drum 1 in the normal rotation direction A of the photosensitive drum 1.

[0083] As shown in FIG. 7(b), the external additive g that has fallen downward in the gravitational direction and scattered when the photosensitive drum 1 rotates in the reverse rotation direction B is captured in the space (hereinafter referred to as space I) surrounded by the first sheet member 25, the second sheet member 26, and the sheet attaching member 30. That is, a collection portion for collecting the external additive g that has fallen downward in the gravitational direction and scattered when the photosensitive drum 1 rotates in the reverse rotation direction B is formed by the first sheet member 25, the second sheet member 26, and the sheet attaching member 30.

[0084] Here, in this embodiment, an example in which the collection unit is configured by three members, i.e., the first sheet member 25, the second sheet member 26, and the sheet attachment member 30, has been shown, but the present invention is not limited thereto. The collection unit may be configured by one member such as the second sheet member 26 or the sheet attachment member 30, or may be a modified example configured by two members such as the second sheet member 26 and the sheet attachment member 30.

[0085] Here, regarding the tip positions of the first sheet member 25 and the second sheet member 26 provided in the developing device 24 according to the first embodiment, an explanation will be given using the schematic diagram of FIG. 8.

[0086] As shown in FIG. 8, the second sheet member 26 is attached to the sheet attachment member 30 in the same manner as the first sheet member 25. The position of the free end of the second sheet member 26 on the side opposite to the fixed end fixed to the sheet attachment member 30 (the position where the second sheet member 26 is closest to the photosensitive drum 1) is defined as position K. Further, as shown in FIG. 8, from the position (point P) where the tip of the first sheet member 25 abuts on the photosensitive drum 1, the position (the position reached when the photosensitive drum 1 is reversely rotated and stopped starting from the position of point P) where the photosensitive drum 1 reversely rotates and stops in the cleaning mode is defined as position J (point Q). Also, as shown in FIG. 8, the exposure position where the surface of the photosensitive drum 1 is exposed by the exposure device 4 is defined as position L.

[0087] As shown in FIG. 8, with respect to the normal rotation direction A of the photosensitive drum 1, position K is located upstream of position J, and position K is located downstream of position L. In other words, with respect to the reverse rotation direction B of the photosensitive drum 1, position K is located downstream of position J, and position K is located upstream of position L.

[0088] That is, in the first embodiment, when the photosensitive drum 1 is reversely rotated and stopped in the cleaning mode from the position where the tip of the first sheet member 25 abuts on the photosensitive drum 1, the photosensitive drum 1 is stopped at a position before reaching the exposure position (position L).

[0089] Further, as shown in FIG. 8, the collection unit is provided to face the photoreceptor drum 1 in a non-contact manner in a region below the point P in the direction of gravity and between the position of the point P and the position of the point Q (position J) with respect to the horizontal direction.

[0090] One end side (fixed end) in the longitudinal direction of the second sheet member 26 is attached to the sheet attaching member 30, and the other end side (free end opposite to the fixed end) in the longitudinal direction of the second sheet member 26 is disposed in a non-contact manner with respect to the photosensitive drum 1. At this time, the fixed end of the second sheet member 26 is located below the free end of the second sheet member 26 in the direction of gravity.

[0091] Further, the free end of the second sheet member 26 is between the position J (point Q) and the exposure position (position L) with respect to the horizontal direction. More specifically, the free end of the second sheet member 26 is above the irradiation unit of the exposure device 4 in the direction of gravity and between the position J (point Q) and the irradiation unit of the exposure device 4 with respect to the horizontal direction. Thereby, when the photosensitive drum 1 rotates in the reverse rotation direction B with the external additive g attached to the surface of the first sheet member 25, it is possible to suppress the external additive g from dropping downward in the direction of gravity and scattering onto the optical path of the exposure device 4.

[0092] Further, the second sheet member 26 is provided to face the photoreceptor drum 1 over substantially the entire area of the region of the photoreceptor drum 1 corresponding to the maximum image area among the image areas where an image can be formed on the surface of the photoreceptor drum 1 with respect to the rotation axis direction of the developing sleeve 5.

[0093] Here, the detailed operation of the cleaning mode in the first embodiment will be described with reference to FIG. 9 and Table 1. FIG. 9 is a diagram showing a sequence related to the driving and stopping of the photoreceptor drum 1 during the cleaning mode. Table 1 shows the relationship between the speed of the photoreceptor drum 1 and the driving distance of the photoreceptor drum 1 when executing the sequence related to the driving and stopping of the photoreceptor drum 1 during the cleaning mode.

[0094] First, after the completion of normal image formation (S1) at 264 mm / sec, the drive of the photosensitive drum 1 is stopped, and the photosensitive drum 1 is switched to a state where it can rotate in the reverse direction (S2). Then, the photosensitive drum 1 is driven to rotate in the reverse direction at 60 mm / sec for a first predetermined time (the time described in Table 1) to remove the accumulation of toner t from the tip edge portion of the cleaning blade 14 (S3). After the photosensitive drum 1 is driven in the reverse rotation direction for the first predetermined time (the time described in Table 1), it stops again, and the photosensitive drum 1 is switched to a state where it can rotate in the forward direction (S4). And after the completion of the forward rotation drive (S5) of the photosensitive drum 1 at 264 mm / sec for a second predetermined time (the time described in Table 1), the drive of the photosensitive drum 1 is stopped (S6), and the sequence ends.

[0095]

Table 1

[0096] When the photosensitive drum 1 rotates in the reverse direction, driving the photosensitive drum 1 at a lower speed than during normal image formation is to make the driving distance of the photosensitive drum 1 more stable at a lower speed and easier to stop at a desired position. The relationship between the driving time of the photosensitive drum 1 and the moving distance of the photosensitive drum 1 during the sequence is as described in Table 1. The driving distance of the photosensitive drum 1 varies depending on the configuration of the driving device (not shown) and the configuration of the image forming unit U, and also varies depending on the delay time from when the driving start signal is input to the driving device until the photosensitive drum 1 actually starts to rotate, and the delay time from when the driving stop signal is input until the photosensitive drum 1 actually stops rotating.

[0097] In addition, in the first embodiment, an example has been described in which the sheet attaching member 30 and the regulating blade 23 are separate bodies, and the first sheet member 25, the second sheet member 26, and the third sheet member 27 are attached to the sheet attaching member 30 attached to the regulating blade 23. However, the present invention is not limited to this, and a modified example in which the sheet attaching member 30 and the regulating blade 23 are integrally formed may also be used.

[0098] As described above, the image forming apparatus 100 according to the first embodiment includes a photosensitive drum 1, a cleaning blade 14 that contacts the photosensitive drum 1 to clean the photosensitive drum 1, and an exposure device 4. Further, the image forming apparatus 100 includes a developing sleeve 5, a developing container 2 that stores a developer, a first sheet member 25 provided in contact with the photosensitive drum 1, and a second sheet member 26 provided to face the photosensitive drum 1 without contact, and a developing device 24 having the same. Further, the image forming apparatus 100 is capable of executing a mode (cleaning mode) in which the photosensitive drum 1 is rotated in a second rotation direction opposite to the direction (first rotation direction) in which the photosensitive drum 1 rotates when executing an image forming operation. The position (position K) where the second sheet member 26 is closest to the photosensitive drum 1 is upstream in the first rotation direction from the position where the first sheet member 25 is in contact with the photosensitive drum 1 to the position where the photosensitive drum 1 rotates and stops in the second rotation direction in the cleaning mode (position K).

[0099] According to such a first embodiment, it is possible to suppress the external additive g interposed between the first sheet member 25 provided in the developing device 24 and the photosensitive drum 1 from blocking the optical path of the exposure device 4 when the photosensitive drum 1 rotates reversely.

[0100] [Second Embodiment] In the first embodiment described above, an example of performing control to drive the photosensitive drum 1 in the reverse rotation after driving the photosensitive drum 1 in the reverse rotation and then driving the photosensitive drum 1 in the normal rotation to stop in the cleaning mode has been described. On the other hand, in the second embodiment, an example of performing control to perform a set of driving the photosensitive drum 1 in the reverse rotation and then driving the photosensitive drum 1 in the normal rotation a plurality of times and then stopping in the cleaning mode will be described.

[0101] In the example shown in Table 2, in the cleaning mode, control is performed to perform a set of driving the photosensitive drum 1 in the reverse rotation and then driving the photosensitive drum 1 in the normal rotation three times and then stopping.

[0102]

Table 2

[0103] When the photosensitive drum 1 is in contact with the intermediate transfer belt 8, when the intermediate transfer belt 8 is rotationally driven to remove the paper dust clogged between the intermediate transfer belt 8 and the contact portion of the intermediate transfer belt cleaning blade 60, the photosensitive drum 1 is also rotationally driven in conjunction. At this time, the stop position of the photosensitive drum 1 during reverse rotation driving is at a position J (point Q) in front of reaching the position K when the photosensitive drum 1 is reversely rotated and stopped in the cleaning mode, from the position (point P) where the tip of the first sheet member 25 contacts the photosensitive drum 1. Then, when performing a plurality of sets of driving the photosensitive drum 1 to rotate forward after driving the photosensitive drum 1 to rotate reversely, in the reverse rotation driving and forward rotation driving of the last set, the moving distance of the photosensitive drum 1 by forward rotation driving is made shorter than the moving distance of the photosensitive drum 1 by reverse rotation driving.

[0104] In the embodiment shown in Table 2, in the reverse rotation driving and forward rotation driving of the third time which is the last set, the moving distance of the photosensitive drum 1 by reverse rotation driving is set to 3.0 to 4.5 mm, while the actual moving distance of the photosensitive drum 1 by forward rotation driving is set to 0.3 to 2.9 mm. Thereby, the cleaning blade 14 can be stopped in the same contact state as during image formation, and the accumulation of the toner t can be stopped at the upstream portion with respect to the forward rotation direction A from the contact portion of the cleaning blade 14.

[0105] Also, as in the modified example shown in Table 3, when performing a plurality of sets of driving the photosensitive drum 1 to rotate forward after driving the photosensitive drum 1 to rotate reversely, it is also conceivable to make the moving distance of the photosensitive drum 1 by reverse rotation driving different for each set.

[0106]

Table 3

[0107] In the modification shown in Table 3, among the sets in which the photosensitive drum 1 is driven to rotate in the reverse direction and then driven to rotate in the forward direction, the set in which the moving distance of the photosensitive drum 1 due to the reverse rotation driving is the largest (when the photosensitive drum 1 is driven to rotate in the reverse direction starting from point P, it reaches the most downstream position from point P with respect to the reverse rotation direction B of the photosensitive drum 1) is the third set. In such a case, the stopping position of the photosensitive drum 1 during the reverse rotation driving in which the moving distance of the photosensitive drum 1 due to the reverse rotation driving is the largest (the position that reaches the most downstream from point P with respect to the reverse rotation direction B of the photosensitive drum 1 when the photosensitive drum 1 is driven to rotate in the reverse direction starting from point P) may be used as a reference. That is, in the reverse rotation driving of the third set, the photosensitive drum 1 is stopped at a position J (point Q) before reaching position K when the photosensitive drum 1 is rotated in the reverse direction and stopped in the cleaning mode, starting from the position (point P) where the tip of the first sheet member 25 contacts the photosensitive drum 1. Thereby, the cleaning mode can be executed without the external additive g reaching the exposure position L.

[0108] (Other Embodiments) The present invention is not limited to the above-described embodiments, and various modifications (including organic combinations of each embodiment) are possible based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0109] In the above-described embodiment, as shown in FIG. 1, the image forming apparatus 100 primarily transfers the toner images carried on each of the photosensitive drums 1 (1Y, 1M, 1C, 1K) to the intermediate transfer belt 8. Thereafter, the image forming apparatus 100 contacts the sheet S with the intermediate transfer belt 8 and secondarily transfers the toner image carried on the intermediate transfer belt 8 to the sheet S. In the above-described embodiment, the image forming apparatus 100 having such a configuration has been described as an example, but the present invention is not limited thereto. The present invention can also be applied to an image forming apparatus configured to directly transfer the toner images carried on each of the photosensitive drums 1 (1Y, 1M, 1C, 1K) to the sheet S by directly contacting the sheet S with the photosensitive drums 1 (1Y, 1M, 1C, 1K).

Description of Reference Numerals

[0110] 1 Photosensitive drum 2 Developing container 4 Exposure device 5 Developing sleeve 14 Cleaning blade 24 Developing device 25 First sheet member 26 Second sheet member 100 Image forming apparatus

Claims

1. A rotatable photoreceptor; an exposure device that exposes the photoconductor to light in order to form an electrostatic latent image on the photoconductor; a developing device including a developer container that contains a developer containing a toner and a carrier, and a developer carrier that carries and transports the developer to a developing position where the electrostatic latent image formed on the photoconductor by the exposure device is developed; a cleaning member provided in contact with the photoreceptor for cleaning the photoreceptor; a driving section that drives and rotates the photoconductor in a first rotation direction during a developing operation in which the developing device develops an electrostatic latent image formed on the photoconductor; a control unit capable of executing a mode in which the drive unit is controlled to rotate the photoconductor in a second rotation direction opposite to the first rotation direction during a non-development operation in which the development operation is not performed; a sheet provided in contact with the photoconductor downstream of a position where the cleaning member is in contact with the photoconductor and upstream of the developing position with respect to the first rotation direction; a collection section provided facing the photoconductor in a non-contact manner in a region below a contact position where the sheet is in contact with the photoconductor in a direction of gravity and between the contact position and a position where the photoconductor is reached when the sheet is rotationally driven in the second rotation direction in the mode starting from the contact position; An image forming apparatus comprising:

2. a collection sheet provided facing the photoconductor in a non-contact manner downstream of an exposure position where the photoconductor is exposed by the exposure device and upstream of the contact position with respect to the first rotation direction, The collection section includes the collection sheet, The free end of the trapping sheet is located above the fixed end of the trapping sheet in the direction of gravity, The free end of the collection sheet is located between a position reached when the photoconductor is rotated in the second rotation direction starting from the contact position in the mode and the exposure position in relation to the horizontal direction.

2. The image forming apparatus according to claim 1,

3. the exposure device includes a light-emitting element that emits an LED light, and an irradiation unit that irradiates the LED light emitted by the light-emitting element, The free end of the collection sheet is located above the light-emitting unit in the direction of gravity, The free end of the collection sheet is located between the irradiation unit and a position reached when the photoconductor is rotated in the second rotation direction starting from the contact position in the mode, in relation to the horizontal direction.

3. The image forming apparatus according to claim 2,

4. the developing device further includes a sheet attachment member to which the collection sheet is attached, The collection section is composed of the collection sheet and the sheet attachment member.

3. The image forming apparatus according to claim 2,

5. the developing device further includes a regulating member that regulates an amount of developer carried on the developer carrier, The sheet attaching member is integrally formed with the regulating member.

5. The image forming apparatus according to claim 4.

6. the developing device further includes a sheet attaching member to which the sheet and the collection sheet are attached, The collection section is composed of the sheet, the collection sheet, and the sheet attachment member.

3. The image forming apparatus according to claim 2,

7. the developing device further includes a regulating member that regulates an amount of developer carried on the developer carrier, The sheet attaching member is integrally formed with the regulating member.

7. The image forming apparatus according to claim 6,

8. The collecting section is provided over substantially the entire maximum image area in the direction of the rotation axis of the photoconductor.

2. The image forming apparatus according to claim 1,

9. The developer carrier is rotatable, The developing device further includes a regulating member that regulates an amount of developer carried on the developer carrier, and another sheet that is provided in contact with the developer carrier downstream of a position where the regulating member is closest to the developer carrier in the rotation direction of the developer carrier and upstream of the developing position.

2. The image forming apparatus according to claim 1,

10. The control unit controls the drive unit to rotate the photoconductor in the second rotation direction by a first movement distance in the mode, and then rotate the photoconductor in the first rotation direction by a second movement distance that is shorter than the first movement distance.

2. The image forming apparatus according to claim 1,

11. A rotatable photoreceptor; an exposure device that exposes the photoconductor to light in order to form an electrostatic latent image on the photoconductor; a developing device including a developer container that contains a developer containing a toner and a carrier, and a developer carrier that carries and transports the developer to a developing position where the electrostatic latent image formed on the photoconductor by the exposure device is developed; a cleaning member provided in contact with the photoreceptor for cleaning the photoreceptor; a driving section that drives and rotates the photoconductor in a first rotation direction during a developing operation in which the developing device develops an electrostatic latent image formed on the photoconductor; a control unit capable of executing a mode in which the drive unit is controlled so as to perform a set of rotating the photoconductor in a second rotation direction opposite to the first rotation direction during a non-developing operation in which the developing operation is not performed, and then rotating the photoconductor in the first rotation direction a plurality of times; a sheet provided in contact with the photoconductor downstream of a position where the cleaning member is in contact with the photoconductor and upstream of the developing position with respect to the first rotation direction; a collecting section provided facing the photoconductor in a non-contact manner in a region below a contact position where the sheet is in contact with the photoconductor in a direction of gravity and between the contact position and a position that reaches the most downstream from the contact position in the second rotation direction when the photoconductor is rotationally driven in the second rotation direction in the mode starting from the contact position; An image forming apparatus comprising:

12. a collection sheet provided facing the photoconductor in a non-contact manner downstream of an exposure position where the photoconductor is exposed by the exposure device and upstream of the contact position with respect to the first rotation direction, The collection section includes the collection sheet, The free end of the trapping sheet is located above the fixed end of the trapping sheet in the direction of gravity, A free end of the collection sheet is located between a position that reaches the most downstream from the contact position in the second rotation direction when the photoconductor is rotated in the second rotation direction starting from the contact position in the mode, and the exposure position in the horizontal direction.

12. The image forming apparatus according to claim 11.

13. the exposure device includes a light-emitting element that emits an LED light, and an irradiation unit that irradiates the LED light emitted by the light-emitting element, The free end of the collection sheet is located above the light-emitting unit in the direction of gravity, The free end of the collection sheet is located between the irradiation unit and a position that reaches the most downstream from the contact position in the second rotation direction when the photoconductor is rotated in the second rotation direction starting from the contact position in the mode.

13. The image forming apparatus according to claim 12.

14. the developing device further includes a sheet attachment member to which the collection sheet is attached, The collection section is composed of the collection sheet and the sheet attachment member.

13. The image forming apparatus according to claim 12.

15. the developing device further includes a regulating member that regulates an amount of developer carried on the developer carrier, The sheet attaching member is integrally formed with the regulating member.

15. The image forming apparatus according to claim 14.

16. the developing device further includes a sheet attaching member to which the sheet and the collection sheet are attached, The collection section is composed of the sheet, the collection sheet, and the sheet attachment member.

13. The image forming apparatus according to claim 12.

17. the developing device further includes a regulating member that regulates an amount of developer carried on the developer carrier, The sheet attaching member is integrally formed with the regulating member.

17. The image forming apparatus according to claim 16.

18. The collecting section is provided over substantially the entire maximum image area in the direction of the rotation axis of the photoconductor.

12. The image forming apparatus according to claim 11.

19. The developer carrier is rotatable, The developing device further includes a regulating member that regulates an amount of developer carried on the developer carrier, and another sheet that is provided in contact with the developer carrier downstream of a position where the regulating member is closest to the developer carrier in the rotation direction of the developer carrier and upstream of the developing position.

12. The image forming apparatus according to claim 11.

20. The control unit controls the drive unit to rotate the photoconductor in the first rotation direction by a second movement distance that is shorter than the first movement distance after rotating the photoconductor in the second rotation direction by a first movement distance in a final set of the multiple sets of the mode.

12. The image forming apparatus according to claim 11.

Images