JP2005321577A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus using a blade cleaning apparatus, capable of surely reducing a load fluctuation due to the reduction of the surface frictional coefficient μ of an image carrier caused by such a failure that the cleaning blade has been left in contact with the image carrier, then, capable of preventing the occurrence of a defective stripe image. <P>SOLUTION: The image forming apparatus is provided with an image carrier cleaning sequence SQ. The sequence SQ is as follows; when instructions to start an image forming processing is inputted after the image carrier 2 is stopped, the image carrier 2 is rotated by a prescribed angle, thereafter, the image carrier 2 is stopped again, then, a developer carrier 42 is brought in contact with the image carrier 2, then, the developer carrier 42 is rotated for a prescribed time in contact with the image carrier 2, thereafter, the image carrier 2 is rotated to shift to an image forming processing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image by an electrophotographic method or an electrostatic recording method, and more particularly to an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, and a cleaning blade or the like. The present invention relates to an image forming apparatus that removes the developer on an image carrier by bringing a cleaning member having elasticity or flexibility into contact with the image forming apparatus.

  In a general electrophotographic image forming apparatus typified by the Carlson process, a developer image formed on an image carrier is transferred onto a recording material such as paper in order to repeatedly use a photoreceptor as an image carrier. Various methods are known as cleaning devices for cleaning the transfer residue on the image carrier later. Among these, blade cleaning devices are widely used.

  The blade cleaning device has a flexible (rubber elasticity) cleaning blade as a cleaning member brought into contact with the image carrier in a predetermined pressure contact state and wipes the surface of the image carrier to transfer residual toner from the image carrier. Is removed by scraping.

  Further, in order to improve the cleaning efficiency, the cleaning blade is generally arranged in contact with the counter in the rotation direction when the image carrier is formed with respect to the image carrier.

  In the blade cleaning device as described above, when the image forming apparatus is stopped, that is, when the rotation of the image carrier is stopped, the slip of the image carrier surface area corresponding to the cleaning blade contact area (nip area) of the image carrier is stopped. The property (friction coefficient μ) changes to a different state as compared with other image carrier surface areas. It is known that this causes a streak or image blur (density fluctuation or the like) on the image at the next image formation.

  The slipperiness of the image carrier surface area corresponding to the cleaning blade contact area of the image carrier changes because the residue of fine powder toner or external additives remaining in the cleaning blade contact area is cleaned. It has been found that the cause is that the pressure contact force of the blade is pressed against the surface of the image carrier and aggregates. In general, the friction coefficient μ of the image carrier surface area corresponding to the cleaning blade contact area of the image carrier varies lower than the friction coefficient μ of the other image carrier surface areas.

  Therefore, when the image forming apparatus is re-driven, the image carrier rotates, and the image carrier surface area corresponding to the cleaning blade contact area having a reduced friction coefficient returns to the contact portion with the cleaning blade. The frictional force between the carrier and the cleaning blade changes. Then, the moment the image carrier surface area passes through the contact portion with the cleaning blade, the rotational speed of the image carrier changes faster. At this time, streaks of the image carrier and image blurring (change in density, etc.) occur in the part where the image is formed on the image carrier and the part where the image is transferred to the recording material.

  In order to fundamentally avoid the above technical problem, it is most certain to retract the cleaning blade from the image carrier surface when the image forming apparatus is stopped. However, in this case, the retraction mechanism is costly, it is difficult to ensure the accuracy of the contact state, which leads to poor cleaning, and eventually the quality of the image is deteriorated, and the cleaning blade is contacted again. Has a problem that, for example, it is necessary to abut the cleaned image carrier area before retraction in order not to create an uncleaned area.

  In addition, when means for finely moving the contact position at regular time intervals is used, it is necessary to always supply power to the control device for periodic control. Furthermore, since driving power is also required periodically for fine movement driving, power consumption during standby time increases.

  In the conventional example, it is proposed that the aggregated toner accumulated on the edge portion of the cleaning blade with the image carrier is removed from the edge portion of the cleaning blade by rotating the image carrier reversely when the image carrier is stopped ( Patent Document 1).

  FIGS. 10A and 10B are enlarged schematic views of the edge portion 51e of the cleaning blade 51 for explaining this conventional example. A rubber cleaning blade 51 is in contact with the image carrier 2 over the contact area width W.

  FIG. 10A shows that image formation is being performed, and the image carrier 2 and the cleaning blade 51 are in contact with each other. The image carrier 2 is driven to rotate in the direction of arrow A. The cleaning blade 51 is provided with a predetermined pressing force on the counter with respect to the forward rotation direction at the time of image formation of the image carrier 2 with respect to the image carrier 2 with the leading edge 51e.

  Since the leading edge 51e of the cleaning blade 51 is in contact with the image carrier 2 in the counter direction with the contact pressure against the image carrier 2, the edge 51 e is dragged by the image carrier 2. Distortion occurs and adheres to the image carrier 2. The surface of the image carrier 2 is wiped by the edge portion 51e of the cleaning blade 51 that is brought into contact, and the transfer residual toner is scraped off the image carrier 2.

  In front of the edge portion 51 e of the cleaning blade 51, the toner and the external additive t are accumulated by being blocked by the blade 51. If the image carrier 2 is stopped in a state where the toner and the external additive t are accumulated, the toner and the external additive t are aggregated and fixed on the surface of the image carrier 2. And the edge portion of the cleaning blade 51 may slip through when the next image carrier 2 starts to rotate forward. The part of the aggregated toner that has passed through becomes the slip change portion of the image carrier surface area corresponding to the cleaning blade contact area when the image forming apparatus is stopped.

  Therefore, in the conventional example, as shown in FIG. 10B, after the image carrier 2 is stopped, the image carrier 2 is rotated in the direction B opposite to the normal rotation direction A during image formation. The toner and the external additive t remaining before the edge portion of the cleaning blade 51 are removed from the edge portion 51e before agglomeration, and the image carrier 2 is stopped.

  However, as in the conventional example of FIGS. 10A and 10B, even if the image carrier 2 is reversely rotated B when the image carrier 2 is stopped, the fine powder stays in front of the edge portion of the cleaning blade 51. The toner and the external additive t may aggregate and pass through the edge 51e of the cleaning blade 51 when the next image carrier 2 starts to rotate forward, causing streak-like image defects. There wasn't.

  This cause will be described below.

  That is, as the printing speed of the image forming apparatus is increased, the rotation speed of the image carrier 2 is increased, and the contact pressure of the cleaning blade 51 is increased to clean the spherical and small-diameter toner for improving the image quality. 11 (a), the distortion of the blade tip 51e of the cleaning blade 51 has increased. This distortion occurs when the leading edge portion 51 e is dragged by the image carrier 2 because the image carrier 2 is in contact with the image carrier 2 in the counter direction. The fine toner and the external additive t removed from the image carrier 2 are also likely to enter the gaps of the image carrier 2.

  Here, the stop of the image carrier 2 was performed by rotating the image carrier 2 in the reverse direction B opposite to the normal rotation direction A during image formation as in the conventional example.

  FIG. 11B shows the moment when reverse rotation B is started. The fine toner and the external additive t remaining between the blade edge portion 51e and the image carrier 2 are pressurized by the pressure F by the kicking back of the distorted blade edge portion 51e and are aggregated.

  FIG. 11C shows a state after reverse rotation in the B direction. Aggregated fine powder toner and external additive t were fixed to the image carrier 2. At the time of starting the next rotation of the image carrier, the fixed fine toner and the external additive t pass through the cleaning blade 51, and as described above, the exposure blurs due to the rotational load fluctuation at this time. A streak-like image defect occurred.

  Further, as described above, a cleaning device configured to scrape the residue by pressing the edge 51e of the plate-like cleaning blade 51 made of an elastic material such as urethane rubber against the photosensitive drum as the image carrier may be used. When the charging member is left in contact with the photosensitive drum being stopped, the contact portion on the photosensitive drum is contaminated by adhesion of residual toner or paper dust on the surface of the charging member. Become. Contamination deposits on the photosensitive drum can hardly be visually confirmed, but white streaks corresponding to the contaminated portion appear during development, resulting in an image defect.

  In order to solve such a problem, in Patent Document 2, a pre-rotation operation is executed before image formation is started to drive the photosensitive drum, and the adhering matter on the contact portion is removed by friction of a cleaning blade or the like. Techniques to do this have been proposed.

  However, the above-described conventional example that removes deposits by friction of a cleaning blade or the like satisfies the image quality desired at that time, but in order to satisfy the image quality required in recent years, further higher image quality is required. It came to be required.

  In recent years, toner improvements that are not easily influenced by the environment in which the image forming apparatus is used, in particular external additives, have been improved, and stable image formation has become possible regardless of the use environment. As such an external additive, there is one in which the external additive is coated with silicon oil.

However, when the external additive thus treated is used, the coefficient of friction of the external additive itself is reduced. Furthermore, if the external additive silicone oil oozes out on the photosensitive drum at the cleaning blade contact position, the coefficient of friction of the photosensitive drum at that position is reduced, so cleaning is performed. Friction of the blade or the like makes it impossible to completely remove deposits. Then, when the photosensitive drum slides due to the reduction of the friction coefficient, the exposure becomes incomplete at the corresponding exposure position, and a white streak-like image defect occurs.
JP-A-8-63071 Japanese Patent Laid-Open No. 7-134454

  An object of the present invention has been made in view of the above problems, and in an image forming apparatus using a blade cleaning device, a reduction in the surface friction coefficient μ of the image carrier caused by leaving the cleaning blade in contact with the image carrier. It is an object of the present invention to provide an image forming apparatus that can reliably reduce the load fluctuation due to the occurrence of streak and prevent the occurrence of streak-like image defects.

The above object is achieved by the image forming apparatus according to the present invention. In summary, according to the first aspect of the present invention, an image carrier, a driving unit that rotationally drives the image carrier, a developer carrier that can contact and separate from the image carrier, and the image carrier. In an image forming apparatus having a cleaning blade that contacts a body to remove a developer,
When an instruction to start an image forming process is input after the image carrier is stopped, the image carrier is rotated again by a predetermined angle and then stopped again, and
The developer carrier is brought into contact with the image carrier, the developer carrier is rotated for a predetermined time, and then
The image carrier is rotated to shift to an image forming process.
An image forming apparatus having an image carrier cleaning sequence is provided.

According to the second aspect of the present invention, an image carrier, a driving means for rotationally driving the image carrier, a developer carrier capable of contacting and separating from the image carrier, and a contact on the image carrier. A cleaning blade for removing the developer, and after the image formation process start signal is input, the image carrier is separated from the developer carrier during the image formation process start preparation period. In an image forming apparatus for performing an image forming process by bringing the developer carrier into contact with the image carrier after performing a pre-rotation operation of the image carrier to be rotated for a predetermined time.
When an instruction to start an image forming process is input after the image carrier is stopped, the image carrier is rotated again by a predetermined angle and then stopped again, and
The developer carrier is brought into contact with the image carrier, the developer carrier is rotated for a predetermined time, and then
The rotation of the developer carrying member is stopped, and after the separation from the image carrier, the pre-rotation operation is performed.
An image forming apparatus having an image carrier cleaning sequence is provided.

According to a third aspect of the present invention, an image carrier, a driving means for rotationally driving the image carrier, a developer carrier that can contact and separate from the image carrier, and a contact on the image carrier. A cleaning blade for removing the developer, a transfer member abutting on the image carrier for transferring the image on the image carrier directly or onto a recording material carried thereon, and rotating the image carrier An image forming apparatus having a driving means for
When an instruction to start an image forming process is input after the image carrier is stopped, the image carrier is placed at a position where the cleaning blade abuts the image carrier. The image carrier is rotated in the rotational direction at the time of image formation, and a pre-rotation operation is performed in which a peripheral speed difference is provided between the image carrier and the transfer member before starting the image forming process. An image forming apparatus is provided.

  According to the present invention, it is possible to reduce the load fluctuation due to the partial reduction of the surface friction coefficient μ of the image carrier at low cost, and always output a good image without causing streak-like image defects due to blurring during exposure. be able to.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
An embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS. In this embodiment, the image forming apparatus is a printer that receives image information from a host computer and outputs an image, and a developing device that contains consumables such as a photosensitive drum 2 and a developer as an image carrier. 4 is integrated into the process cartridge 10 so that the image forming apparatus main body 100 can be attached and detached.

  FIG. 1 is a schematic configuration diagram of the image forming apparatus of the present embodiment, FIG. 2 is a cross-sectional view of a cleaning blade installed in the cleaning apparatus used in the present embodiment, and FIG. 3 is a diagram of the developing device used in the present embodiment. FIG.

  The photosensitive drum 2 is rotationally driven in the direction of arrow A in FIG. 1 by a driving means (not shown), and is uniformly charged by a primary charging device 3 serving as a charging roller. In this embodiment, the peripheral speed of the photosensitive drum 2 is 94.2 mm / sec, and the dark portion surface potential Vd of the photosensitive drum 2 uniformly charged by the primary charger 3 is Vd = −500V. The scanner unit 1 including a laser, a polygon mirror, and a lens system scans and outputs a laser beam modulated in accordance with an image signal. The laser beam is reflected by a folding mirror 11 and irradiated onto the photosensitive drum 2. The An electrostatic latent image is formed on the surface of the photosensitive drum 2 irradiated with the laser beam. In this embodiment, the bright portion surface potential Vl is set to Vl = −100V.

  The electrostatic latent image on the photosensitive drum 2 carries toner 41 carried and conveyed by a developing roller 42 as a developer carrying member in the developing device 4 that is rotationally driven in the direction of arrow B in FIG. Development is performed by the development bias applied from FIG. 3, and the toner image is visualized on the photosensitive drum 2.

  In this embodiment, the developing bias voltage Vdc is set to Vdc = −300 V, and the negatively charged toner 41 is reversely developed to form a visible image (toner image) using the toner 41 on the photosensitive drum 2. Further, the photosensitive drum 2 and the developing roller 42 can be contacted and separated as necessary by contact / separation means (not shown).

  On the other hand, the recording material 7 stored in the cassette 71 is supplied to the registration roller 73 in synchronization with the formation of the latent image on the photosensitive drum 2 by the paper feed roller 72. The recording material 7 is conveyed to a transfer charger 6 serving as a transfer roller constituting the transfer device in synchronization with the leading edge of the latent image formed on the photosensitive drum 2 by the registration roller 73, and transferred to the transfer charger. The toner image is transferred to the recording material 7 by the device 6.

  In this embodiment, a transfer process is performed by applying Vtr = 1000 V as a transfer bias voltage Vtr to the transfer charger 6 from a transfer high voltage power source (not shown).

  The recording material 7 to which the toner image has been transferred is permanently fixed to the toner image by the fixing device 8, and is finally discharged to the outside of the device.

  The toner remaining on the photosensitive drum 2 is removed by a cleaning device 5 using a cleaning blade 51 made of an elastic blade. The cleaning blade 51 is disposed such that the tip of the elastic blade is in the counter direction with respect to the rotation direction A of the photosensitive drum 2.

  A sectional view of the cleaning blade 51 used in this embodiment is shown in FIG. An elastic blade 51b made of a rubber elastic body made of urethane rubber was bonded to a holder 51a made of a metal sheet metal to form a cleaning blade 51. As the elastic blade 51b, an elastic body such as silicone rubber, nitrile rubber, and chloroprene rubber can be used in addition to the urethane rubber used in this embodiment.

  A timer 12 as a time measuring means is provided in the main body of the apparatus for measuring the stop time of the photosensitive drum 2, and is disposed in the vicinity of the cleaning apparatus 5 in this embodiment.

  In this embodiment, the photosensitive drum 2, the charging roller 3, the developing device 4, and the cleaning device 5 are collectively united to form a process cartridge 10. These components are assembled in the cartridge 10 so as to have a predetermined mutual arrangement relationship. The angle θ between the contact position of the cleaning blade 51 and the contact position of the developing roller 42 on the surface of the photosensitive drum 2 is as follows. 120 °. The cartridge 10 is inserted into and attached to a predetermined portion in the image forming apparatus main body 100 by a mounting means (not shown), and conversely, can be removed from the apparatus main body 100.

  Next, the developing device 4 of this embodiment will be described with reference to FIG.

  The developing device 4 according to the present embodiment includes a developer contained in a toner container 40, that is, a toner 41, and a developing roller 42 that carries the toner 41 on the outer peripheral surface and conveys it to a developing area where the photosensitive drum 2 is formed. A toner supply roller 43 that conveys and applies the toner 41 to the developing roller 42, and a developing blade that regulates the amount of toner so that the toner 41 applied by the toner supply roller 43 is carried on the developing roller 42 in an appropriate amount. 44, a blowout prevention sheet 45 that contacts the developing roller 42 on the downstream side in the rotation direction B of the developing roller 42 from the developing region and prevents toner leakage from the inside of the developing device 4, and a developing process in the developing region A developing high-voltage power source 46 is connected to the developing roller 42 and provided in the main body of the image forming apparatus.

  The developing roller 42 is configured by providing an elastic layer 42b composed of a base layer and a surface layer thereon around a cylindrical body 42a made of metal such as aluminum, an alloy thereof, and stainless steel. In this embodiment, the outer diameter is 16 mm. did. The base layer of the elastic layer 42b is made of rubber such as silicone rubber, polyurethane rubber, or NBR, and the surface layer is made of ether urethane, nylon, or the like. Of course, the structure is not limited thereto, and a structure in which a foam such as sponge is used for the base layer and a rubber elastic layer is formed on the surface layer is also possible. In this embodiment, the developing roller 42 is rotationally driven in the direction of arrow B in FIG. 3 at a peripheral speed of 141 mm / sec.

The developing blade 44 is formed by adhering or injection molding a polyamide elastomer elastic member having a thickness of 1 mm to a phosphor bronze plate having a spring elasticity as a metal thin plate and having a thickness of 0.1 mm, and developing the elastic member surface. The roller 42 is in contact with the surface at a predetermined linear pressure. The metal blade maintains the pressure contact force of the developing blade 44 against the developing roller 42, the polyamide elastomer is charged with negatively charged toner 41, and a toner layer having a predetermined thickness is formed on the developing roller 42. . In this embodiment, the developing blade 44 is set so that the amount of toner carried on the developing roller 42 after passing through the developing blade 44 is 0.4 mg / cm ² .

  The metal thin plate is not particularly limited as long as the pressure contact force of the developing blade 44 is maintained, and the elastic member can be selected in consideration of the charging property of the toner. Further, depending on the combination of the toner 41 and the developing roller 42 used, a configuration in which a metal thin plate having spring elasticity, such as a stainless steel thin plate or a phosphor bronze thin plate, is used as it is and the toner 41 is brought into contact with the developing roller 42 may be used. .

  The toner supply roller 43 is preferably a sponge structure or a fur brush structure in which fibers such as rayon and nylon are planted on a core metal from the viewpoint of conveying and applying toner to the developing roller 42 and stripping off the remaining toner. In this embodiment, the urethane foam 43b is provided on the metal core 43a and used as an elastic roller having a diameter of 16 mm. The toner supply roller 43 made of an elastic roller contacts the developing roller 42 with a predetermined intrusion amount, and is driven to rotate at a peripheral speed of 113 mm / sec in the same direction as the developing roller 42 (in the direction of arrow C in FIG. 3). The timing is driven and stopped in synchronization with the developing roller 42. In this embodiment, the penetration amount of the toner supply roller 43 with respect to the developing roller 42 is 1.5 mm.

  Next, the generation state of the streak image in the conventional apparatus will be described.

FIG. 4 shows the evaluation result of the streak image caused by leaving the cleaning blade in contact when the stop time of the photosensitive drum 2 is changed. At this time, the horizontal axis indicates the stop time of the photosensitive drum 2, and the vertical axis indicates the quality of the stripe. The evaluated image is the first halftone image after being stopped for 1 second to 6 minutes. The streak of the exposure blur due to the slip of the agglomerated toner portion caused by leaving the cleaning blade in contact with the blade was judged as follows.
◎ Nothing at all.
○ is slightly streaked when you look closely.
Δ indicates streaks.
X indicates streaks clearly.

  From this graph, it can be seen that streaks occur when the photosensitive drum 2 is stopped for 2 to 3 minutes or longer. When streaks are generated, fine powder toner and external additives are aggregated at the cleaning blade contact position on the photosensitive drum 2, and from this result, it can be seen that the longer the stop time, the more aggregated.

  FIGS. 5A to 5D are schematic views of the appearance of the contact portion W between the cleaning blade 51 and the photosensitive drum 2.

  FIG. 5A shows a state in which the photosensitive drum 2 rotates (forward rotation) in the arrow direction A during printing, and the tip 51 of the cleaning blade 51 is distorted. This distortion occurs when the leading edge 51 e of the cleaning blade 51 is in contact with the photosensitive drum 2 in the counter direction with respect to the positive rotation direction A of the photosensitive drum 2, so that the leading edge 51 e is dragged by the photosensitive drum 2. . The fine toner and the external additive t removed from the photosensitive drum 2 also move in the positive rotation direction A of the photosensitive drum 2 and easily enter the gap between the distorted blade edge portion 51e and the photosensitive drum 2. .

  FIG. 5B shows a state where printing is finished and the photosensitive drum 2 is stopped. During the stop, the fine toner and the external additive t accumulated between the cleaning blade 51 and the photosensitive drum 2 are pressurized and gradually aggregated while being left by the distorted cleaning blade 51. However, from the result of FIG. 4, if the stop is 1 minute or less, the agglomeration is not deteriorated and cleaning can be performed. It can also be seen that if it is allowed to stand for 2 to 3 minutes, the fixation with the photosensitive drum 2 proceeds and it is difficult to clean.

  FIG. 5C shows a state immediately after starting the next printing after stopping for 5 minutes. As a result of the fine powder toner and the external additive t being completely agglomerated and fixed to the photosensitive drum 2 during the stoppage, the toner passes through the cleaning blade 51.

  FIG. 5D shows a state where the fine powder toner and the external additive t have passed through the blade 51. The fine powder toner or the external additive t fixed to the photosensitive drum 2 makes one round of the photosensitive drum 2 and returns to the cleaning blade 51 again. At this time, the fine powder and the external additive t pass through the cleaning blade 51, so that the exposure is blurred due to the rotational load fluctuation of the photosensitive drum 2, and a streak-like image defect occurs.

  That is, if the fine toner and the external additive t fixed to the photosensitive drum 2 after the stop can be removed before making one round of the photosensitive drum 2 and returning to the cleaning blade 51 again, the photosensitive drum Even after 2 is stopped for a long time, streaks do not occur at the next printing.

  Based on the above background, embodiments of the present invention will be described in detail below.

  FIG. 6 shows a configuration in which fine toner and external additive t fixed to the photosensitive drum 2 make a round around the photosensitive drum 2 and are removed before returning to the cleaning blade 51 again. This is shown in relation to the image forming apparatus.

  In this embodiment, the control means 21 is connected to the exposure device 1, the developing device 4, the transfer charger 6 and the like, and an image is recorded on the recording material 7 based on image information input from a host computer (not shown). Control to perform the formation.

  The control means 21 is connected to a time measuring means, that is, a timer 12. The timer 12 measures the time during which the photosensitive drum 2 has been stopped, and the value of the timer 12 is reset after the end of the image forming process.

  The control means 21 reads the time measured by the timer 12, and when the time measured by the timer 12 when the image forming process start signal is input is equal to or longer than a predetermined time, the photosensitive drum 2 and the developing roller 42 are separated from each other. The body drum is rotated by an angle θ (θ = 120 ° in the present embodiment) formed by the cleaning blade contact position and the developing roller contact position and then stopped again. Then, after the photosensitive drum 2 and the developing roller 42 are in contact with each other, the developing roller 42 is rotated at a predetermined speed (141 mm / sec in this embodiment) for a predetermined time, and then the photosensitive drum 2 is rotated again to form an image forming process. Execute the sequence to move to. Hereinafter, this sequence is referred to as an image carrier cleaning sequence, that is, a “DC (Drum Cleaning) sequence” SQ1. When the time measured by the timer 12 is smaller than the predetermined time, the image forming process starts immediately after the image forming process start instruction.

  From the results shown in FIG. 4, streaks of rank Δ or less occur when the stop time of the photosensitive drum 2 is 3 minutes or more. Therefore, in this embodiment, the stop time of the photosensitive drum 2 measured by the timer 12 is used. The DC sequence SQ1 is executed in the case of 3 minutes or more.

  Table 1 shows the results of evaluating the rotation time and the streak image when the developing roller 42 was rotated at 141 mm / sec when the DC sequence SQ1 was executed after the photosensitive drum 2 stopped for 5 minutes.

  From this result, it was found that a good image without streaks can be obtained by rotating the developing roller for 1.0 second or more. In this embodiment, based on this result, the rotation time of the developing roller 42 is 1.0 second.

  FIG. 7 shows a flowchart of this embodiment.

  According to this embodiment, when an image forming process start signal is input (S0), the control unit 21 reads the measurement time T of the timer 12 (S1) and determines whether the value is equal to or longer than the predetermined time Tfix (S2). In this example, Tfix was set to 3 minutes.

  If the measurement time T exceeds Tfix, the DC sequence SQ1 is executed (S3). Specifically, the photosensitive drum 2 and the developing roller 42 are separated from each other, and the photosensitive drum 2 is rotated forward by 120 ° which is an angle θ formed by the contact portion of the cleaning blade 51 and the contact portion of the developing roller 42. After that, the developing roller 42 is brought into contact again and rotated at 141 mm / sec for 1.0 second, and then the photosensitive drum 2 is rotated at 94 mm / sec to shift to an image forming process (S4). After the image forming process is completed, the value of the timer 12 is reset (S5) to prepare for the next image formation.

  When the measurement time T is Tfix or less (3 minutes or less in this embodiment), the image forming process is immediately executed without executing the DC sequence SQ1 after the image forming process start signal is input (S4). After completion, the value of the timer 12 is reset (S5) to prepare for the next image formation.

  In the present embodiment, based on the evaluation results shown in FIG. 7, the rotation speed of the developing roller 42 during execution of the DC sequence SQ1 is 141 mm / sec and the rotation time is 1.0 second. However, the present invention is not limited to this, and may be appropriately changed according to the configuration of the developing device, the type of toner to be used, and the like.

  Further, in this embodiment, in order to minimize the wear of the developing roller 42 due to rubbing with the photosensitive drum 2 when the DC sequence SQ1 is executed, the DC sequence SQ1 is only performed when the photosensitive drum 2 is stopped for a predetermined time or longer. However, the DC sequence SQ1 may always be executed after inputting the image forming process start signal regardless of the stop time of the photosensitive drum 2.

  As described above, according to this embodiment, according to the stop time of the photosensitive drum 2, the developing roller is rubbed against the cleaning blade contact position on the photosensitive drum in a stopped state before the image formation. 2 is executed to remove the agglomerated toner and the external additive t fixed on the surface 2. As a result, it is possible to reduce the load fluctuation due to the partial reduction of the surface friction coefficient μ of the photosensitive drum 2 at a low cost, and to always output a good image without causing streak-like image defects due to blurring during exposure. it can.

  In addition, according to the present embodiment, a practically good image can be obtained without a cleaning member contact / separation control device, so that the cost can be greatly reduced and the reliability can be improved. Further, since only control immediately before image formation is required, power consumption during standby time can be minimized, and noise due to fine movement during standby can be avoided.

  Further, in the case where the image forming interval is long, the product durability life is extended as compared with the method in which the fine movement is always performed at a constant period.

Example 2
Next, a second embodiment of the image forming apparatus according to the present invention will be described.

  Also in this embodiment, the image forming apparatus of Embodiment 1 described with reference to FIGS. 1 to 3 is used. This embodiment is characterized in that the image forming apparatus performs a so-called pre-rotation operation in which the photosensitive drum 2 is rotated for a predetermined time after the image forming process signal is input and before the image forming process is started.

  Also in the present embodiment, the same configuration as that of the first embodiment described with reference to FIG. 6 is performed, and the fine powder toner or the external additive t fixed to the photosensitive drum 2 makes one round of the photosensitive drum 2 and is cleaned again. The configuration is such that they are removed before returning to the blade 51.

  That is, the control means 21 is connected to the exposure device 1, the developing device 4, the transfer charger 6, and the like, and is used to form an image on the recording material 7 based on image information input from a host computer (not shown). Control is performed.

  In addition, the timer 12 is connected to the control means 21. The timer 12 measures the time during which the photosensitive drum is stopped, and the value of the timer 12 is reset after the image forming process is completed.

  The control unit 21 reads the time measured by the timer 12, and when the time measured by the timer 12 when the image forming process start signal is input is equal to or shorter than a predetermined time, the photosensitive drum is prepared as preparation before moving to the image forming process. A so-called pre-rotation operation is performed in which 2 is rotated for a predetermined time in a state of being separated from the developing roller 42, and then the photosensitive drum 2 and the developing roller 42 are brought into contact again to shift to the image forming process.

  In the image forming apparatus of this embodiment, the pre-rotation time is 2.5 seconds, and the rotation speed of the photosensitive drum 2 at this time is 94.2 mm / sec.

  If the time measured by the timer 12 when the image forming process start signal is input is equal to or longer than a predetermined time, the photosensitive drum 2 is cleaned with the photosensitive drum 2 and the developing roller 42 separated from each other before shifting to the pre-rotation operation. After rotating by an angle θ (120 ° in this embodiment) formed by the blade contact position and the development roller contact position, the rotation is stopped again, and the photosensitive drum 2 and the development roller 42 are brought into contact with each other. Is rotated at a predetermined speed (141 mm / sec in this embodiment) for a predetermined time, and then a sequence for again separating the photosensitive drum 2 and the developing roller 42 is executed. Hereinafter, this sequence is referred to as an image carrier cleaning sequence, that is, a “DC (Drum Cleaning) sequence” SQ2. After execution of the DC sequence SQ2, the process proceeds to the above-described pre-rotation operation, and then proceeds to the image forming process.

  From the results shown in FIG. 4, streaks of rank Δ or less occur when the stop time of the photosensitive drum 2 is 3 minutes or more. Therefore, in this embodiment, the stop time of the photosensitive drum 2 measured by the timer 12 is used. The DC sequence SQ2 is executed when the time is 3 minutes or longer.

  Table 2 shows the result of evaluating the streak rank when image formation is performed after the photosensitive drum 2 is pre-rotated after the DC sequence SQ2 is executed after the photosensitive drum has stopped for 5 minutes. The rotation speed of the developing roller 42 when the DC sequence SQ2 was executed was 141 mm / sec.

  From this result, it was found that a good image without streaks can be obtained by rotating the developing roller for 0.8 seconds or more. In this embodiment, based on this result, the rotation time of the developing roller 42 is set to 0.8 seconds.

  When the pre-rotation operation of the photosensitive drum 2 is executed before the start of the image forming process as in the image forming apparatus according to the present embodiment, the fixed fine powder toner remaining on the photosensitive drum that cannot be completely removed in the DC sequence SQ2 The external additive t is removed little by little while passing through the cleaning blade 51 during the subsequent pre-rotation operation (twice in this embodiment), so that the pre-rotation operation is performed before the start of the image forming process. Compared with the image forming apparatus of Example 1 that does not perform the above, the streaks are slightly smaller.

  FIG. 8 shows a flowchart of this embodiment.

  When the image forming process start signal is input (S0), the control unit 21 reads the measurement time T of the timer 12 (S1), and determines whether the value is equal to or longer than the predetermined time Tfix (S2).

  In this example, Tfix was set to 3 minutes. When the measurement time T is equal to or shorter than Tfix, a so-called pre-rotation operation is performed in which the photosensitive drum 2 is rotated for a predetermined time in a state of being separated from the developing roller 42 as a preparatory step immediately before shifting to the image forming process (S4). Thereafter, the photosensitive drum 2 and the developing roller 42 are again brought into contact with each other, and the process proceeds to the image forming process (S5). After the image forming process is completed, the value of the timer 12 is reset (S6) to prepare for the next image formation.

  When the measurement time T exceeds Tfix, after the image forming process start instruction, the DC sequence SQ2 is executed before the pre-rotation (S3). Specifically, the photosensitive drum 2 and the developing roller 42 are separated from each other, and the photosensitive drum 2 is rotated forward by 120 ° which is an angle formed by the contact portion of the cleaning blade 51 and the contact portion of the developing roller 42. After that, the developing roller 42 is brought into contact again, rotated at 141 mm / sec for 0.8 seconds, then stopped, and then separated again. Thereafter, the pre-rotation operation described above is performed (S4), and the photosensitive drum 2 and the developing roller 42 are again brought into contact with each other and the process proceeds to the image forming process (S5). After the image forming process is completed, the value of the timer 12 is reset (S6) to prepare for the next image formation.

  In the present embodiment, based on the evaluation results shown in Table 2, the rotation speed of the developing roller when the DC sequence SQ2 is executed is 141 mm / sec and the rotation time is 0.8 seconds. However, these values are limited to these values. Instead, it may be appropriately varied depending on the configuration of the developing device, the type of toner used, and the like. Further, the time for the pre-rotation operation is 2.5 seconds and the rotation speed of the photosensitive drum during the pre-rotation is 94.2 mm / sec, but these values may be appropriately changed depending on the specifications of the image forming apparatus. Good.

  Further, in this embodiment, in order to minimize the wear of the developing roller 42 due to rubbing against the photosensitive drum 2 when the DC sequence SQ2 is executed, the DC sequence SQ2 is only performed when the photosensitive drum 2 is stopped for a predetermined time or longer. Was supposed to be executed. However, the DC sequence SQ2 may always be executed after inputting the image forming process start signal regardless of the photosensitive drum stop time.

  Also in this embodiment, the same effects as those of the first embodiment can be obtained.

Example 3
Next, a description will be given of a third embodiment of the image forming apparatus according to the present invention.

  Also in this embodiment, the same image forming apparatus as in Embodiments 1 and 2 described with reference to FIGS. 1 to 3 is used. The present embodiment is characterized in that the image forming apparatus according to the second embodiment is an image forming apparatus in which the rotation speed of the photosensitive drum 2 during the pre-rotation operation described above is variable depending on the stop time.

  In this embodiment, the same configuration as that of Embodiments 1 and 2 described with reference to FIG. 6 is used, and the fine powder toner and the external additive t fixed to the photosensitive drum 2 make one round of the photosensitive drum 2, They are configured to be removed before returning to the cleaning blade 51 again.

  That is, the control means 21 is connected to the exposure device 1, the developing device 4, the transfer charger 6, and the like, and is used to form an image on the recording material 7 based on image information input from a host computer (not shown). Control is performed.

  In addition, the timer 12 is connected to the control means 21. The timer 12 measures the time during which the photosensitive drum is stopped, and the value of the timer 12 is reset after the image forming process is completed.

  The control unit 21 reads the time measured by the timer 12, and immediately performs the above-described pre-rotation operation when the time measured by the timer 12 when the image forming process start signal is input is equal to or shorter than the first predetermined time. Thereafter, the photosensitive drum 2 and the developing roller 42 are brought into contact again, and the process proceeds to the image forming process. At this time, the rotation time of the photosensitive drum 2 during the pre-rotation operation is set to 2.5 seconds, and the rotation speed is set to a first predetermined speed (94.2 mm / sec in this embodiment). In this embodiment, in this embodiment, the photosensitive drum 2 rotates at least two rounds during the pre-rotation.

  If the time measured by the timer 12 when the image forming process start signal is input is equal to or longer than the second predetermined time, the DC sequence SQ2 described above is executed after the image forming process start signal is input and before the pre-rotation operation is performed. Transition to the image forming process. At this time, the rotation time of the photosensitive drum 2 during the pre-rotation operation is set to 2.5 seconds, and the rotation speed is set to a second predetermined speed (188.4 mm / sec in this embodiment) that is faster than the first predetermined speed. .

  Note that the rotation speed of the photosensitive drum 2 is returned to the first predetermined speed after the DC sequence SQ2 is executed and before the process proceeds to the image forming process. In this case, the photosensitive drum 2 rotates at least four or more times during the pre-rotation, and the fine powder toner and the external additive t in the fixed state remaining on the photosensitive drum 2 without being completely removed by the DC sequence SQ2 are at least four times. Passes the cleaning blade 51.

  From the results shown in FIG. 4, streaks of △ rank or less occur when the photosensitive drum stop time is 3 minutes or more, and streaks of × rank or less occur when the photosensitive drum stop time is 4 minutes or more. is there. In this embodiment, when the stop time of the photosensitive drum 2 measured by the timer 12 is not less than 3 minutes and not more than 4 minutes, the DC sequence SQ2 is executed and then the first predetermined speed (94.2 mm / sec) is reached. Rotate. When the stop time is 4 minutes or longer, the rotation speed of the photosensitive drum 2 during the previous rotation is set to the second predetermined speed (188.4 mm / sec) and the second rotation is performed for 2.5 seconds.

  Table 3 shows the image after the photosensitive drum 2 is stopped for 3 minutes and then the DC sequence SQ2 is executed, and then the photosensitive drum 2 is pre-rotated at a first predetermined speed (94.2 mm / sec). It is the result of evaluating the stripe when forming.

  Table 4 shows that after the photoconductor drum 2 is stopped for 5 minutes and the DC sequence SQ2 is executed, the photoconductor drum 2 is pre-rotated at a second predetermined speed (188.4 mm / sec). It is the result of evaluating the streaks when performing image formation.

  In both cases, the rotation speed of the developing roller 42 during execution of the DC sequence SQ2 was set to 141 mm / sec.

  From these results, it was found that a good image without streaks can be obtained by rotating the developing roller 42 for 0.6 seconds or more.

  In this embodiment, the rotation time of the developing roller 42 is set to 0.6 seconds based on this result. When the pre-rotation operation is performed for the same time, the faster the rotational speed of the photosensitive drum 2, the more frequently the fine powder toner and the external additive t remaining on the photosensitive drum 2 pass through the cleaning blade 51. Therefore, the streak becomes slightly slight.

  FIG. 9 shows a flowchart of this embodiment.

  When the image forming process start signal is input (S0), the control unit 21 reads the measurement time T of the timer 12 (S1), and determines whether the value is equal to or longer than the first predetermined time Tfix1 (S2). In this example, Tfix1 was set to 3 minutes. When the measurement time T is equal to or shorter than Tfix1, a pre-rotation operation for 2.5 seconds is immediately performed at the first predetermined speed v1 (94.2 mm / sec in the present embodiment) (S10), and then the photosensitive drum 2 and development are performed again. The process advances to the image forming process by contacting the roller 42 (S7). After completing the image forming process, the value of the timer 12 is reset (S8) to prepare for the next image formation.

  It is determined whether or not the measurement time T exceeds Tfix1 and is equal to or shorter than a second predetermined time Tfix2 that is longer than Tfix1 (S4).

  When the measurement time T exceeds Tfix1 and is equal to or shorter than a second predetermined time Tfix2 longer than Tfix1, the DC sequence SQ2 is executed after the image forming process start signal is input and before the pre-rotation is performed (S4-a). Specifically, the photosensitive drum 2 and the developing roller 42 are separated from each other, and the photosensitive drum 2 is rotated forward by 120 ° which is an angle formed by the contact portion of the cleaning blade 51 and the contact portion of the developing roller 42. After that, the developing roller 42 is brought into contact again, rotated at 141 mm / sec for 0.8 seconds, then stopped, and then separated again. Thereafter, a pre-rotation operation for 2.5 seconds is performed at the first predetermined speed v1 (94.2 mm / sec) described above (S10), and then the photosensitive drum 2 and the developing roller 42 are brought into contact again to form an image forming process. (S7). After completing the image forming process, the value of the timer 12 is reset (S8) to prepare for the next image formation.

  If the measurement time T is equal to or longer than Tfix2 in step S3, the DC sequence SQ2 is executed after the image forming process start signal is input and before the pre-rotation is performed (S4-b). Thereafter, a pre-rotation operation is performed for 2.5 seconds at the second predetermined speed v2 (188.4 mm / sec) described above (S5), and the rotational speed of the photosensitive drum 2 is returned to the first predetermined speed v1. (S6) The photosensitive drum 2 and the developing roller 42 are again brought into contact with each other and the process proceeds to the image forming process (S7). After completing the image forming process, the value of the timer 12 is reset (S8) to prepare for the next image formation.

  In the present embodiment, the first predetermined stop time is 3 minutes and the second predetermined stop time is 4 minutes based on the evaluation result of FIG. 4, and based on the evaluation results shown in Tables 3 and 4, The rotation speed of the developing roller 42 during execution of the DC sequence SQ2 was 141 mm / sec, and the rotation time was 0.6 seconds. However, these values are not limited to these values, and may be appropriately changed according to the configuration of the developing device, the type of toner to be used, and the like. Further, the time for the pre-rotation operation is 2.5 seconds, and the rotation speed of the photosensitive drum 2 during the pre-rotation is 94.2 mm / sec and 188.2 mm / sec. These values are also the specifications of the image forming apparatus. It may be appropriately changed depending on the above.

  Also in this embodiment, the same operational effects as those of Embodiments 1 and 2 can be obtained.

Example 4
Next, a description will be given of a fourth embodiment of the image forming apparatus according to the present invention.

  A fourth embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. FIG. 12 shows the structure of the periphery of the photosensitive drum of the image forming apparatus that can be adapted to carry out the present invention.

  In the image forming process, the photosensitive drum 2 as an image carrier is rotationally driven by a driving unit at a predetermined peripheral speed in the rotation direction of an arrow in the figure. A primary charging device 3 serving as a charging roller for charging the surface of the photosensitive drum to a predetermined potential in order along the rotation direction of the photosensitive drum 2, a laser beam is irradiated on the photosensitive drum 2 based on image information. A scanner unit 1 that forms an electrostatic latent image, a developing device 4 that attaches toner to the electrostatic latent image and develops it as a toner image, a transfer roller for transferring the toner image on the photosensitive drum 21 to the recording material 7, A transfer device 6 to be transferred, a cleaning device 5 to remove transfer residual toner remaining on the surface of the photosensitive drum 2 after transfer, and the like are disposed.

  In this embodiment, the photosensitive drum 2, the charging device 3, the developing device 4, and the cleaning device 5 include an image forming cleaning device 9 including the photosensitive drum 2, the charging device 3, and the cleaning device 5, and the developing device 4. I know.

  In this embodiment, the image forming cleaning device 9 and the developing device 4 are connected by a spring (not shown) to form a process cartridge 10 that is an integral cartridge, and can be attached to and detached from the image forming apparatus main body. It has become.

  Since the image forming cleaning device 9 and the developing device 4 are pressed and contacted by a spring, the two devices can be separated by moving the contacting / separating means 20 up and down. In other words, the photosensitive drum 2 and the developing device 4 can be contacted and separated.

  In this embodiment, a transfer roller 6 constituting a transfer device is disposed so as to face and contact the photosensitive drum 2 in the process cartridge 9. The transfer roller 6 has its driving means controlled by a transfer drive controller 22. The fixing device 8 fixes the toner image transferred to the recording material 7. The recording material 7 onto which the toner image on the photosensitive drum 2 has been transferred is applied with heat and pressure when passing through the fixing device 8. As a result, the toner image is permanently fixed on the surface of the recording material 5.

  The process cartridge 10 will be described.

  The photosensitive drum 2 is configured by applying a photosensitive layer to the outer peripheral surface of an aluminum cylinder, and is driven to rotate in the direction of arrow A in the figure. Photosensitive drum driving means including an electric motor (not shown) is connected to the central axis of the photosensitive drum 2, and the photosensitive drum driving means rotationally drives the photosensitive drum 2. The photosensitive member driving means is controlled by the photosensitive member drive control unit 24 (FIG. 3).

  As the charging device 3, a contact charging type can be used. The charging member is a conductive roller formed in a roller shape, and the surface of the photosensitive drum 2 can be uniformly charged by bringing the roller into contact with the photosensitive drum 2 and applying a charging bias.

  The developing device 4 includes a developing roller 42 as a developer carrying member that rotates in the direction of an arrow, and a developing container 40 that stores toner. A part of the developing container 40 facing the photosensitive drum 2 is opened over substantially the entire longitudinal direction of the photosensitive drum 2, and a roller-shaped developer carrier (developing means) is formed in the opening. A developing roller 42 is disposed. During image formation, the developing roller 42 is rotationally driven in the direction of arrow B in the figure.

  Further, the developing device 4 includes a developing blade 44 as a developer layer thickness regulating member that regulates the amount of toner carried on the developing roller 42. The developing blade 44 is provided such that the vicinity of the free end side is in contact with the outer peripheral surface of the developing roller 42 by surface contact. When the toner carried on the developing roller 42 passes through the contact portion with the developing blade 44, the toner is charged by frictional charging and is restricted to a thin layer.

  In the developing device 4 having such a configuration, a DC voltage fixed to a predetermined value as a developing bias is applied to the developing roller 42. Thus, in this embodiment, the exposed portion of the surface of the photosensitive drum 2 that is uniformly charged is developed.

  The photosensitive drum 2 on which the toner image is formed continues to rotate, and is transferred to the recording material 7 that has been attracted to and conveyed by the transfer roller 6 at the transfer portion. The toner remaining on the photosensitive drum 2 without being transferred is removed from the photosensitive drum 2 by the cleaning device 5.

  The cleaning device 5 includes a cleaning blade 51 and a waste toner box 52. The cleaning blade 51 is always in pressure contact with the photosensitive drum 2 with a predetermined pressing force, and the toner remaining on the photosensitive drum 1 is physically removed. The toner is scraped off and stored in the waste toner box 52.

  The operation from the end of the image forming process to the start of the next image forming process by the image forming apparatus of the present embodiment having the above configuration will be described.

  After the toner image carried on the photosensitive drum 2 is transferred to the recording material 7, the photosensitive drum 2 and the developing roller 42 are separated by the contact / separation means 20, and the driving of the photosensitive drum 2 is stopped. The image forming process as described above is completed.

  When an instruction to start the image forming process is detected, the photosensitive drum 2 is rotated in the order of rotation in the image formation from the position where the cleaning blade 51 is in contact with the photosensitive drum 2 to the position where it is in contact with the transfer roller 6. In the direction, that is, in the direction of arrow A in the figure. Thereafter, a predetermined drive start signal is output to the transfer drive control unit 22 to control the drive means, whereby the transfer roller 6 is driven at a predetermined speed.

  This is a pre-rotation operation performed prior to the image forming process. At this time, the image forming operation is not performed, and the photosensitive drum 2 is stopped. By this pre-rotation operation, the adhering matter at the contact portion with the cleaning blade 51 on the photosensitive drum 2 can be scraped off by driving the transfer roller 6.

  Further, since the photosensitive drum 2 and the developing roller 42 are separated during the pre-rotation operation, wear of the photosensitive drum 2 and the developing roller 42 can be suppressed. When the pre-rotation operation is completed, the process proceeds to the next image forming process.

  According to this embodiment, when the cleaning member 51 and the photosensitive drum 2 are left in contact with each other, the edge of the cleaning member 51 is caused by the friction between the photosensitive drum 2 and the transfer roller by performing the pre-rotation operation. The deposit t on the photosensitive drum 2 staying in the part 51e is scraped off, and streaky image defects can be suppressed.

Example 5
Next, a description will be given of a fifth embodiment of the image forming apparatus according to the present invention.

  The basic configuration of the image forming apparatus according to the present embodiment is the same as that of the image forming apparatus according to the fourth embodiment described with reference to FIG. 12, and in this embodiment, only the pre-rotation operation is changed. .

  The pre-rotation operation will be described with reference to FIG.

  When the image forming process is completed and an instruction to start the image forming process is detected, as in the fourth embodiment, the photosensitive member is exposed from the position where the cleaning blade 51 is in contact with the photosensitive drum 2 to the position where it is in contact with the transfer roller 6. The body drum 2 is rotated in the forward direction, that is, in the direction of arrow A in the figure.

  Thereafter, a predetermined drive start signal is output to the transfer drive control unit 22 and the photoconductor drive control unit 24. During the pre-rotation operation, the transfer roller 6 is driven at a predetermined speed, and the photosensitive drum 2 is driven at a speed slower than the predetermined speed. By doing so, the transfer roller 6 rotates quickly with respect to the photosensitive drum 2, and the deposits on the contact portion with the cleaning blade 15 on the photosensitive drum 2 can be scraped off. Note that the photosensitive drum 2 may be rotated at a predetermined speed and the transfer roller 6 may perform a pre-rotation operation with a peripheral speed difference such as driving at a speed higher than the predetermined speed.

  According to the present embodiment, when the cleaning member 51 and the photosensitive drum 2 are left in contact with each other, a pre-rotation operation is performed with a difference in peripheral speed between the photosensitive drum 2 and the transfer roller 42. By the friction between the photosensitive drum 2 and the transfer roller, the deposits on the photosensitive drum 2 staying at the edge of the cleaning member 51 are scraped off, and streaky image defects can be suppressed.

Example 6
Next, a description will be given of a sixth embodiment of the image forming apparatus according to the present invention.

  FIG. 14 shows a four-color full-color image forming apparatus which is an embodiment of the multi-color image forming apparatus of this embodiment to which the present invention can be applied.

  The image forming apparatus shown in FIG. 14 is an inline-type full-color printer, and has four photosensitive drums 2 (2a, 2b, 2c, and 2d) arranged in parallel in the vertical direction. All these photosensitive drums 2 (2a, 2b, 2c, 2d) are arranged along the moving direction of the electrostatic conveyance belt 30 as a recording material conveyance belt, and the photosensitive drums 2 (2a, 2b, 2c, 2d) are arranged. The full color image can be obtained by sequentially transferring the color toner image carried on the recording material 7 to the recording material 7. Further, the process cartridge 10 (10a, 10b, 10c, 10d) of the present embodiment is as described in the fourth embodiment.

  The operation from the end of the image forming process of this embodiment to the start of the next image forming process will be described.

  In this embodiment, the point that the electrostatic conveyance belt 30 is used as a transfer member instead of the transfer roller 6 is different from the fourth and fifth embodiments.

  In this embodiment, when the image forming process is completed and an instruction to start the image forming process is detected, the cleaning blade 51 (51a, 51b, 51c, 51d) is used as the photosensitive drum as in the fourth and fifth embodiments. 2 (2a, 2b, 2c, 2d), all the photosensitive drums 2 (2a, 2b, 2c, 2d) from the position in contact with the electrostatic conveyance belt 30 in the forward direction, that is, Rotate in the middle arrow A direction.

  Thereafter, a predetermined drive start signal is output to a transfer drive control unit and a photoreceptor drive control unit (not shown). During the pre-rotation operation, all the photosensitive drums 2 (2a, 2b, 2c, 2d) are simultaneously driven at a predetermined speed by controlling the driving means, and the electrostatic conveyance belt 30 is controlled at the predetermined speed by controlling the driving means. Drive at a faster speed.

  By doing so, the electrostatic conveyance belt 30 rotates quickly with respect to the photosensitive drum 2 (2a, 2b, 2c, 2d), and cleaning on the photosensitive drum 2 (2a, 2b, 2c, 2d) is performed. It is possible to scrape off the adhering matter at the contact portion with the blade 51 (51a, 51b, 51c, 51d).

  The pre-rotation operation may be the operation used in the fourth and fifth embodiments. In the sixth embodiment, and the fourth and fifth embodiments, a transfer member that transports the recording material 7 such as the transfer roller 6 and the electrostatic transport belt 30 is used. However, the pre-rotation operation may use an intermediate transfer drum, an intermediate transfer belt, or the like that transfers and laminates the toner image on the photosensitive drum 2 to the intermediate transfer member and then retransfers it to the recording material.

  Also in this embodiment, the same operational effects as those of Embodiments 4 and 5 can be obtained.

Example 7
Next, a description will be given of a seventh embodiment of the image forming apparatus according to the present invention.

  The basic configuration of the image forming apparatus of this embodiment is the same as that of the image forming apparatuses of Embodiments 4 and 5 described with reference to FIGS. 12 and 13. In this embodiment, the photosensitive drum 2 is used. There is a time measuring means for reading the stop time T, that is, the timer 12, and only the pre-rotation operation is changed.

  The pre-rotation operation will be described with reference to FIG. First, the time measuring means of the present embodiment will be described.

  The photosensitive drum 2 and the transfer roller 6 are driven and controlled by the photosensitive member drive control unit 22 and the transfer drive control unit 24. The central processing unit 21 includes a microcomputer and performs various controls including an image forming process.

  The central processing unit 21 is connected to the voltage application power source 23, the development bias application power source 46, the photoconductor drive control unit 24, and the transfer drive control unit 22. A programmable timer 12 is connected to the central processing unit 21.

  The programmable timer 12 controls the central processing unit 21 to set various operation modes, preset the count contents, read the count contents, update the count contents, and output a signal when the set time has elapsed. Can do. The programmable timer 12 can measure the time T during which the cleaning member 51 is in contact with the surface of the photosensitive drum 2 in a stopped state.

  With reference to FIG. 15, the operation from the end of the image forming process to the start of the next image forming process in the image forming apparatus of the present embodiment will be described.

  The power is turned on (S0), initialization processing is performed (S1), and standby processing is performed (S2).

  On the other hand, when the driving of the photosensitive drum 2 is stopped and the image forming process is completed (S9), the programmable timer 12 is set to the timing mode, the count value is cleared, and the timing operation of the programmable timer 12 is started (S10). . Therefore, the programmable timer 12 measures time while executing the standby process.

  When an image forming process start signal is input (S0) and the central processing unit 21 detects an instruction to start the image forming process (S3), the value output by the programmable timer 12, that is, the photosensitive drum 2 is stopped. The time T that has been used is read (S4).

  A position where the cleaning blade 51 comes into contact with the transfer roller 6 from the position where the cleaning blade 51 comes into contact with the photosensitive drum 2 when stopped for a certain time (T ≧ Tfix) based on the read contact stop time T (S ≧ Tfix). The photosensitive drum 2 is rotated in the forward direction, that is, in the direction of arrow A in FIG.

  When the pre-rotation operation is completed (S7), the process proceeds to the next image forming process (S8). The contents of the image forming process are as described in the fourth embodiment.

  When the image forming process is completed (S9), the operation mode of the programmable timer 12 is reset, the count value is cleared, and the time counting operation is started (S10).

  Thereafter, the process returns to the standby process (S2) again to repeat the operation.

  Therefore, the contact stop time measured by the programmable timer 12 after this corresponds to the standby time from the end of the image forming process to the start of the next image forming process, that is, the time when the photosensitive drum is not rotating. To do.

  The contact stop time for performing the pre-rotation operation has been described above with reference to FIG.

  That is, as shown in FIG. 4, when the contact stop time is 3 minutes or more, the streak rank is from Δ to ×. Therefore, in this embodiment, the pre-rotation operation is performed only when the contact stop time T is 3 minutes or longer. By doing so, it is possible to minimize the time for the pre-rotation operation, reduce the wear of the photosensitive drum 2 and the transfer roller 6 as much as possible, and suppress the occurrence of white stripes. Note that the stop time at which an image defect occurs differs depending on the toner used and the image forming apparatus, so the contact stop time for executing the pre-rotation operation differs depending on the model.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present invention. It is sectional drawing of one Example of a cleaning blade. It is sectional drawing of one Example of a developing device. 6 is a graph showing a relationship between a stop time of a photosensitive drum and a streak image. FIG. 4 is a schematic view of a blade tip when a photosensitive drum is rotated forward and left to stand and then rotated again. 1 is a schematic configuration relationship diagram of an embodiment of an image forming apparatus according to the present invention. 3 is a flowchart of an embodiment of control of the image forming apparatus according to the present invention. 6 is a flowchart of another embodiment of control of the image forming apparatus according to the present invention. 6 is a flowchart of another embodiment of control of the image forming apparatus according to the present invention. It is the schematic of the blade front-end | tip part at the time of reversely rotating, after stopping a photoreceptor drum. FIG. 3 is a schematic view of a blade tip when the photosensitive drum is stopped and then rotated backward and left. FIG. 6 is a schematic cross-sectional view illustrating a configuration of a peripheral portion of a photosensitive drum and a pre-rotation operation of another embodiment of the image forming apparatus according to the present invention. FIG. 6 is a schematic cross-sectional view illustrating a configuration of a peripheral portion of a photosensitive drum and a pre-rotation operation of another embodiment of the image forming apparatus according to the present invention. 1 is a diagram illustrating a schematic configuration of an embodiment of a multicolor image forming apparatus according to the present invention. 6 is a flowchart of an embodiment of a pre-rotation operation of the image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 2 Photosensitive drum (image carrier)
3 Charging device 4 Developing device 5 Cleaning device 6 Transfer roller (transfer device)
7 Recording material 10 Process cartridge 12 Timer 20 Contact / separation means 21 Control means (central processing unit)
22 Transfer Drive Control Unit 24 Photoconductor Drive Control Unit 30 Electrostatic Conveyance Belt 42 Developing Roller (Developer Carrier)
43 Toner supply roller 51 Cleaning blade

Claims (13)

An image carrier, drive means for rotationally driving the image carrier, a developer carrier that can be brought into contact with and separated from the image carrier, and a cleaning blade that contacts the image carrier and removes the developer. In an image forming apparatus having
When an instruction to start an image forming process is input after the image carrier is stopped, the image carrier is rotated again by a predetermined angle and then stopped again, and
The developer carrier is brought into contact with the image carrier, the developer carrier is rotated for a predetermined time, and then
The image carrier is rotated to shift to an image forming process.
An image forming apparatus having an image carrier cleaning sequence. Having time measuring means for measuring the time during which the image carrier is stopped;
2. The image carrier cleaning sequence is executed according to a time when the image carrier measured by the time measuring unit when an instruction to start an image forming process is input is stopped. The image forming apparatus described in 1.   When an instruction to start the image forming process is input, the angle at which the image carrier is rotated until it is stopped again is an angle formed by the contact position of the cleaning blade and the contact position of the developer carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An image carrier, drive means for rotationally driving the image carrier, a developer carrier that can be brought into contact with and separated from the image carrier, and a cleaning blade that contacts the image carrier and removes the developer. And before the image carrier is rotated for a predetermined time while being separated from the developer carrier during the image formation process start preparation period after the image formation process start signal is input. In an image forming apparatus for performing an image forming process by bringing the developer carrier into contact with the image carrier after performing a rotation operation,
When an instruction to start an image forming process is input after the image carrier is stopped, the image carrier is rotated again by a predetermined angle and then stopped again, and
The developer carrier is brought into contact with the image carrier, the developer carrier is rotated for a predetermined time, and then
The rotation of the developer carrier is stopped, and after the separation from the image carrier, the pre-rotation operation is performed.
An image forming apparatus having an image carrier cleaning sequence. Having time measuring means for measuring the time during which the image carrier is stopped;
5. The image carrier cleaning sequence is executed according to a time when the image carrier measured by the time measuring unit when an instruction to start an image forming process is input is stopped. The image forming apparatus described in 1.   Varying the rotation speed of the image carrier during the pre-rotation operation according to the time that the image carrier was stopped measured by the time measuring means when an instruction to start an image forming process was input The image forming apparatus according to claim 5.   When an instruction to start the image forming process is input, the angle at which the image carrier is rotated until it is stopped again is an angle formed by the contact position of the cleaning blade and the contact position of the developer carrier. The image forming apparatus according to claim 4, wherein the image forming apparatus is an image forming apparatus. An image carrier, drive means for rotationally driving the image carrier, a developer carrier capable of coming into contact with and separating from the image carrier, a cleaning blade for contacting the image carrier and removing the developer, Image forming comprising: a transfer member that is in contact with the image carrier in order to transfer an image on the image carrier directly or onto a carried recording material; and a drive unit that rotationally drives the image carrier. In the device
When an instruction to start an image forming process is input after the image carrier is stopped, the image carrier is placed at a position where the cleaning blade abuts the image carrier. The image carrier is rotated in the rotational direction at the time of image formation, and a pre-rotation operation is performed in which a peripheral speed difference is provided between the image carrier and the transfer member before starting the image forming process. An image forming apparatus. The developer carrier is disposed at a position downstream of the cleaning member and upstream of the transfer member along the rotational direction of the image carrier.
While the image carrier is stopped, the position where the cleaning blade is in contact with the image carrier is rotated to the position where it is in contact with the transfer member, and during the pre-rotation operation, the image carrier and the developer carrier. The image forming apparatus according to claim 8, wherein the body is separated from the body.   The image forming apparatus according to claim 8, wherein the pre-rotation operation stops driving the image carrier and drives the transfer member.   10. The image forming apparatus according to claim 8, wherein the pre-rotation operation drives the image carrier at a normal speed and drives the transfer member at a speed higher than normal.   The image forming apparatus according to claim 8, wherein the pre-rotation operation drives the image carrier at a speed slower than normal and drives the transfer member at a normal speed. Stopping the driving of the image carrier and measuring time for measuring the time that the cleaning member is in contact with the image carrier;
The image forming apparatus according to claim 8, wherein the pre-rotation operation is executed according to a stop time of the image carrier.

Images