JP2012173515A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of, when including a film of which a free end is in contact with at any position in a section from a latent image forming position by a latent image forming device to a developing position by a developing device on a surface of a rotating latent image holding body, reducing image failures such as a stripe generated on an image caused by remaining foreign matters such as dust happening to be attached to the free end portion of the film without adding new components.SOLUTION: The image forming apparatus includes: the latent image holding body; the latent image forming device; the developing device; a transfer device; a cleaning device; and control means. The control means executes a control operation for rotating the latent image holding body in a predetermined direction at a predetermined time from when the film and the latent image holding body are rotated in a direction opposite to a predetermined direction, until when a surface portion in contact with the free end of the film during rotation in the opposite direction, of the surface of the latent image holding body, passes through at least the cleaning device.

Description

  The present invention relates to an image forming apparatus.

  In general, an image forming apparatus such as a copying machine or a printer that forms an image composed of a developer is electrostatically charged on the surface of a latent image holding body such as a photosensitive member based on image information by a latent image forming apparatus such as an exposure device. After forming the latent image, the electrostatic latent image is developed with a developer supplied from a developing device to form a developer image.

  Among such image forming apparatuses, from the viewpoint of preventing the developer from leaking and floating on the side where the latent image forming apparatus is installed from the developing apparatus, the surface of the rotating latent image holding body is arranged. The film as a seal member (leakage prevention material) can be freely installed in any position in the section from the latent image forming position where an electrostatic latent image is formed by the latent image forming apparatus to the developing position where development is performed by the developing apparatus. Some are installed with the edges touching.

  Conventionally, there has been proposed an image forming apparatus or the like to which such improvements regarding the seal member are added.

  For example, there is known an image forming apparatus in which a film having a specified thickness or the like is applied as a sheet-like seal member installed in contact with a photoconductor upstream of a developer reservoir (developing device) in the rotation direction of the photoconductor. (Patent Document 1). According to this image forming apparatus, black streak-like image noise in the sub-scanning direction that has occurred in the non-image area can be prevented by applying a seal member made of a polyethylene terutarate film having a thickness of 100 μm.

  In addition, the seal member provided on the inner wall of the toner dust prevention member having the arc-shaped inner wall covering the upper outer peripheral surface of the developing roller is in a state where its free end is suspended in a region corresponding to between the specific magnetic poles of the developing roller. A developing device provided is known (Patent Document 2). According to this developing device, in the conventional developing device, the toner dust that adheres and accumulates on the inner wall of the toner dust prevention member or the inner side of the seal member peels off and falls and falls into the developing region, and the It is said that the problem of appearing as image noise on black spots can be solved.

Japanese Patent Application Laid-Open No. 07-287445 JP-A-10-207229

  The present invention is installed with the free end in contact with any position in the section from the latent image forming position by the latent image forming device to the developing position by the developing device on the surface of the rotating latent image holding member. If a foreign film such as dust adheres to the free end of the film, image defects such as streaks that occur on the image due to the presence of the foreign material It is an object of the present invention to provide an image forming apparatus that can be reduced without adding new components.

The image forming apparatus of the present invention (A1)
A latent image holding body having a surface for holding an electrostatic latent image and rotating in a predetermined direction;
A latent image forming apparatus for forming an electrostatic latent image on the surface of the latent image holding member;
A developing device that develops the electrostatic latent image with a developer to form a developer image;
A transfer device for transferring the developer image formed on the surface of the latent image holding member to a recording member or an intermediate transfer member;
A cleaning device that removes and cleans unnecessary objects attached to the surface of the latent image holder;
A film installed with a free end in contact with any position in a section from the latent image forming position by the latent image forming device to the developing position by the developing device on the surface of the latent image holding member; ,
The surface on which the free end of the film is in contact when rotating in the opposite direction of the surface of the latent image holding member after rotating the latent image holding member in the opposite direction to the predetermined direction. And a control means for executing a control operation for rotating the portion in the predetermined direction at least until the portion passes through the cleaning device at a required time.

The image forming apparatus of the invention (A2) is the image forming apparatus of the invention A1,
In the control operation, the control means rotates the latent image holding member in the opposite direction by at least a circumferential length corresponding to a length in which the free end of the film is in contact.

The image forming apparatus of the invention (A3) is the image forming apparatus of the invention A1 or A2,
The control means adds an operation of attaching a developer from the developing device to the surface of the latent image holding body before or when the latent image holding body is rotated in the opposite direction in the control operation. To do.

The image forming apparatus according to the invention (A4) is the image forming apparatus according to any one of the inventions A1 to A3.
Humidity measuring means for measuring the humidity inside the image forming apparatus is provided, and the control means before the image forming operation is started when the humidity measured by the humidity measuring means reaches a preset value or After the completion, the control operation is executed.

The image forming apparatus according to the invention (A5) is the image forming apparatus according to any one of the inventions A1 to A4.
A time measuring unit that measures an elapsed time from the end of the last image forming operation to a request for the next image forming operation; and the control unit presets an elapsed time measured by the time measuring unit. The control operation is executed before the next image forming operation when the measured value is exceeded.

The image forming apparatus of the invention (A6) is the image forming apparatus of any one of the inventions A1 to A5.
One or both of the latent image holding member and the developing device including the replacement unit, an exchange unit configured to be attached and detached, detection means for detecting that the replacement unit has been changed, and the latent image holding member A rotation amount measuring means for accumulating and measuring the rotation amount;
The control means enables the control operation to be executed when the detection means detects the replacement of the replacement unit, and the latent image measured by the rotation amount measurement means after the replacement unit is detected to be replaced. The control operation is not required to be executed when the rotation amount of the holding body reaches a preset value.

  According to the image forming apparatus of the invention A1, the free end is placed at any position in the section from the latent image forming position by the latent image forming apparatus to the developing position by the developing apparatus on the surface of the rotating latent image holding member. The film is placed in contact with the film, and even if foreign matter such as dust adheres to the free end of the film, the foreign matter continues to exist on the image. Image defects can be reduced without adding new components.

  In the image forming apparatus according to the invention A2, compared with the case where the configuration of the invention is not provided, when the latent image holding member is rotated in the reverse direction in the control operation, the reverse rotation is not unnecessarily performed. The operation can be executed efficiently.

  In the image forming apparatus of the invention A3, the latent image holding member is attached to the surface of the latent image holding member when the latent image holding member is rotated in the reverse direction in the control operation as compared with the case where the configuration of the invention is not provided. The developer comes into contact with the film, and the removal of foreign matters adhering to the film is promoted.

  In the image forming apparatus according to the invention A4, the control operation can be appropriately executed only when there is a high possibility that foreign matter is present on the film as compared with the case where the configuration of the invention is not provided. .

  In the image forming apparatus according to the invention A5, the control operation can be appropriately executed only when there is a high possibility that foreign matter is present on the film, as compared with the case where the configuration of the invention is not provided. .

  In the image forming apparatus according to the invention A6, the control operation can be appropriately executed only when there is a high possibility that a foreign object will newly adhere to the film, as compared with the case where the configuration of the invention is not provided. .

1 is an explanatory diagram showing an overview of an image forming apparatus according to an embodiment. FIG. 2 is a schematic view of a part (mainly an image forming device) in the image forming apparatus of FIG. It is the schematic which shows the structure of the principal part (installation of a film etc.) in the image forming apparatus of FIG. It shows the attachment state of a film, (a) is a partial cross-sectional explanatory drawing showing the state seen from the front side, (b) is a conceptual diagram showing the state seen from the side surface side. 2 is a block diagram illustrating a configuration of a main control system of the image forming apparatus. FIG. It is a flowchart which shows the example of 1 structure of the control procedure in the case of performing control operation | movement of film cleaning before starting a printing. It is a flowchart which shows the procedure of control operation | movement of film cleaning. (A) is an enlarged explanatory view showing a state of foreign matter adhering to the film, and (b) is an enlarged explanatory view showing an amount of reverse rotation of the photosensitive drum, a state of removing the foreign matter, and the like. It is a flowchart which shows the other structural example of the control procedure in the case of performing control operation | movement of film cleaning before starting a printing. It is a schematic explanatory drawing which shows the other attachment state (other structural example of an image forming apparatus) of a film. FIG. 2 is a diagram for explaining an example of a streak-like image defect that occurs due to the continued presence of foreign matter on a film, wherein (a) is a conceptual diagram showing an example of white stripes, and (b) is an example of color stripes. FIG.

  Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as “embodiments”) will be described with reference to the accompanying drawings.

[Embodiment 1]
FIG. 1 shows an outline of an image forming apparatus 1 according to the first embodiment, and FIG. 2 shows a part (image forming apparatus) in the image forming apparatus 1.

  The image forming apparatus 1 is configured as a color printer, for example. In the image forming apparatus 1, a toner (coloring or the like) that forms a developer in an internal space of the housing 10 based on information of an input image using an image recording method such as a known electrophotographic method or electrostatic recording method. A plurality of image forming devices 20 that form toner images to be developed with fine powder), and a recording sheet 9 as an example of a recording member that holds the toner images formed by the image forming device 20 and finally The intermediate transfer device 30 for transferring, the paper feeding device 40 for accommodating and transporting the required recording paper 9 to be supplied to the secondary transfer position of the intermediate transfer device 30, and the recording with the toner image transferred by the intermediate transfer device 30 A fixing device 45 for fixing the toner image through the paper 9 and a control device 5 are installed. The housing 10 has a support structure portion and an exterior portion formed of a support member, an exterior cover, and the like. An alternate long and short dash line in the figure indicates a conveyance path through which the recording paper 9 is mainly conveyed in the housing 10.

  The image forming apparatus 20 includes four image forming apparatuses 20Y, 20M, 20C, which respectively form four color toner images exclusively for yellow (Y), magenta (M), cyan (C), and black (black: K). It is composed of 20K. These four image forming devices 20 (Y, M, C, K) are arranged in a state of being arranged in series in the internal space of the housing 10. Each image forming device 20 (Y, M, C, K) has a substantially common configuration as shown below.

  Each image forming device 20 (Y, M, C, K) includes a rotating photosensitive drum 21 as shown in FIGS. 1 and 2, and the following devices are arranged around the photosensitive drum 21. Is mainly arranged. The main devices are a charging device 22 for charging the surface of the photosensitive drum 21 (image holding surface capable of holding an electrostatic latent image) to a required potential, and an input image on the charged surface of the photosensitive drum 21. An exposure device 23 that irradiates light based on information (signal) to form an electrostatic latent image (for each color) having a potential difference, and the electrostatic latent image of the corresponding color (Y, M, C, K). A developing device 24 (Y, M, C, K) that develops with a developer toner to form a visible toner image, and primary transfer that transfers the toner image to the intermediate transfer device 30 (intermediate transfer belt). A device 25; a drum cleaning device 26 that removes deposits such as toner remaining on the image holding surface of the photosensitive drum 21 after transfer; and a static eliminator 27 that neutralizes the surface of the photosensitive drum 21.

  The photosensitive drum 21 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or columnar substrate to be grounded, and includes a motor, a rotation transmission mechanism, and the like. Rotation drive device 13 (drum rotation drive unit 51: FIG. 5) configured as shown in FIG. The charging device 22 is a non-contact type charging device that performs charging by corona discharge, for example. When the developing device 24 performs reversal development, the charging device 22 has a voltage or current as a charging bias for charging to the same polarity as the charging polarity of the toner supplied from the developing device. 52 (FIG. 5).

  The exposure device 23 irradiates light (dotted line with arrows) LB configured in accordance with image information input to the image forming apparatus 1 onto the image holding surface of the photosensitive drum 21 after being charged. It forms an electrostatic latent image. As the exposure device 23, a scanning type configured using optical components such as a semiconductor laser and a polygon mirror is used, but in addition, for example, configured using a light emitting diode and an optical component. A non-scanning exposure apparatus may be used. In this exposure device 23, the image processing apparatus 11 (image processing unit: FIG. 5) performs necessary image processing on the information of the image to be printed input to the image forming apparatus 1, and each color obtained after the processing is performed. The component image signal is transmitted to the exposure driving unit 53 (FIG. 5). The image forming apparatus 1 can be connected to an image reading device, an information terminal such as a personal computer, and an image information device such as a storage medium read / write device via a connection communication unit 12 (connection communication unit: FIG. 5). The image information is input from the image information device.

  As shown in FIG. 2 and the like, the developing device 24 (Y, M, C, K) includes a developer container 241 that stores a two-component developer G including a non-magnetic toner (Gt) and a magnetic carrier (Gc). A developer roll 242 that holds the developer G contained in the developer container 241 while rotating and conveys the developer G to a developing region that is in close proximity to and faces the photosensitive drum 21, and the developer contained therein. An agitating / conveying member 243 such as a screw auger that conveys the developing roll 242 while stirring by rotating G, and a layer thickness regulating member 244 that regulates the amount (layer thickness) of the developer held on the developing roll 242 ing. The developing roll 242 includes a rotating cylindrical developer holder (sleeve) and a magnet roll that is installed inside the cylinder of the developer holder and has a plurality of magnetic poles arranged at intervals on the circumferential surface. Has been.

  In each of the developing devices 24, a developing bias is supplied to the developing roll 242 from the developing power supply 54 (FIG. 5), and the developing roll 242 and the agitation transport member 243 are connected to the developing rotation driving device 55 (FIG. 5). ) Is rotated in the direction indicated by the arrow. The toner of the developer G in each developing device 24 is rubbed with the carrier by being conveyed while being agitated by the agitating / conveying member 243 in the developer container 241, and thus has a required polarity (in the first embodiment, negative polarity). ) Is triboelectrically charged.

  Further, as shown in FIGS. 3 and 4 and the like, the developing device 24 has a film 6 as a seal member on the upper edge 241a of the developing opening in the developer container 241, and the free end 6a thereof is photosensitive. It is installed in contact with the surface of the drum 21.

  The film 6 is a section from the position (latent image forming apparatus) P1 where the exposure device 23 forms an electrostatic latent image on the image holding surface of the photosensitive drum 21 to the position (development position) P2 where the developing device 24 performs development. However, in the first embodiment, it is disposed so as to contact at a position on the front side of the development position P2 (upstream side in the rotation direction A1 of the photosensitive drum 21). In addition, the outer surface of the free end 6 a of the film 6 is in contact with the image holding surface of the photosensitive drum 21 along the rotational axis direction C, and the leading end of the free end 6 a is in contact with the image holding surface of the photosensitive drum 21. It is in a curved state in contact with the rotation direction A1 at an acute angle θ. On the other hand, the film 6 has an end (fixed end) 6b opposite to the free end 6a fixed to the upper edge 241a. The outer surface of the free end 6a of the film 6 is in contact with the image holding surface of the photosensitive drum 21 with a predetermined length E in the rotation direction A1 of the photosensitive drum 21 (FIG. 4). The film 6 may be any film as long as it can stably come into contact without damaging the surface of the photosensitive drum 21. For example, a film having a thickness of 50 to 300 μm made of a resin such as polyurethane or PET (polyethylene terephthalate) is more preferable. Although a film made of thermoplastic polyurethane having a thickness of about 100 μm is used, it is not limited to this.

  The primary transfer device 25 is a contact-type transfer device including a primary transfer roll that rotates in contact with the surface of the photosensitive drum 21 (via an intermediate transfer belt 31 described later) and is supplied with a primary transfer bias. As the primary transfer bias, a DC voltage or the like having a polarity opposite to the charging polarity of the toner is applied from the transfer power supply unit 56 (FIG. 5). The primary transfer device 25 may be handled as constituting the intermediate transfer device 30. The drum cleaning device 26 contacts the surface of the photosensitive drum 21 after passing through the primary transfer position, and adheres to the surface of the drum 26a in a housing 26a where the portion facing the photosensitive drum 21 is open. In addition to the elastic blade 26b and the rotating brush 26c for removing the toner, there are provided a sending member 26d and the like for driving the adhering material such as toner removed by the elastic blade 26b and the rotating brush 26c to collect and send them to a collecting unit (not shown). It is configured.

  As shown in FIG. 1 and the like, the intermediate transfer device 30 is arranged so as to exist at a position below each image forming device 20 (Y, M, C, K). The intermediate transfer device 30 includes an intermediate transfer belt 31 that rotates and rotates in a direction indicated by an arrow B while passing through a primary transfer position between the photosensitive drum 21 and the primary transfer device 25 (primary transfer roll). A plurality of support rolls 32a to 32f that hold the intermediate transfer belt 31 in a desired state from the inner surface thereof and rotatably support the intermediate transfer belt 31 and the intermediate transfer belt 31 supported by the support roll 32e at a predetermined pressure. It is mainly composed of a rotating secondary transfer roll 35 and a belt cleaning device 36 that removes adhering matter such as toner and paper dust remaining on the intermediate transfer belt 31 after passing through the secondary transfer roll 35. Yes.

  As the intermediate transfer belt 31, for example, a belt formed of an endless belt having a predetermined thickness using a material in which a resistance adjusting agent such as carbon is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used. . The support roll 32a is configured as a drive roll, and the support roll 32c is configured as a tension applying roll. The support roll 32a as a drive roll receives power from the intermediate transfer rotation drive device 57 (FIG. 4) and rotates in the direction indicated by the arrow B. A secondary transfer bias is supplied from the transfer power supply unit 56 (FIG. 4) to the support roll 32e (or the secondary transfer roll 35). As the secondary transfer bias, a DC voltage or the like indicating the same polarity (or opposite polarity) as the charging polarity of the toner is supplied.

  The paper feeding device 40 is disposed so as to exist at a position below the intermediate transfer device 30. The sheet feeding device 40 is attached so that it can be pulled out to the front side (side surface that the operator faces when using it) of the housing 10, and is a single unit that accommodates recording paper 9 of a desired size, type, etc. Or a plurality of) paper containers 41 and a feeding device 42 that feeds the recording paper 9 from the paper container 41 one by one. The recording paper 9 sent from the paper feeding device 40 is connected to the intermediate transfer belt 31 in the intermediate transfer device 30 via a plurality of paper conveyance roll pairs 43a, 43b, 43c,. The sheet is conveyed to a secondary transfer position between the secondary transfer rolls 35.

  The fixing device 45 rotates inside the housing 46 in the direction indicated by the arrow and is heated by heating means so that the surface temperature is maintained at a predetermined temperature. A pressurizing rotator 48 which is rotated in contact with a predetermined pressure in a state substantially along the axial direction is installed. The recording sheet 9 on which an image is formed after the fixing of the toner image by the fixing device 45 is discharged to a housing 10 or the like through a discharge conveyance path constituted by a plurality of conveyance roll pairs and conveyance guide materials. It is transported and accommodated.

  The control device 5 includes an arithmetic processing device, a storage element, a control circuit, an external storage device, an input / output device, and the like, and the image forming apparatus 1 according to a control program and data stored in the storage element or the external storage device. The operation of each component is controlled. The control device 5 includes an image forming control unit 50 that controls operations of the image forming device 20, the intermediate transfer device 30, the paper feeding device 40, and the fixing device 45, and a connection communication unit (input unit) to which image information is input. 11 is connected to various detection means, an image processing unit 12 that performs required image processing on image information, an operation input unit 13 that sets and displays operations and conditions of the image forming apparatus, and the like. A control signal necessary for operation is transmitted. Other configurations of the control device 5 will be described later.

  In the first embodiment, for example, the photosensitive drum 21, the charging device 22, the cleaning device 26, and the static eliminator 27 in the image forming device 20 are configured as an exchange unit that is attached to and detached from the housing 10 and replaced. . The replacement unit is replaced with a new one after being removed from the housing 10 when the photosensitive drum 21 or the like reaches the end of its life or when it is damaged. For example, the replacement unit can be configured as a unit in which the photosensitive drum 21 and the cleaning device 26 are integrated.

  A basic image forming operation (printing) by the image forming apparatus 1 is performed as described below. Here, a full-color image formed by combining toner images of four colors (Y, M, C, K) formed using all of the four image forming devices 20 (Y, M, C, K). A pattern (full color mode) of the image forming operation to be formed will be described.

  When the control device 7 receives an instruction for requesting an image forming operation via the connection communication unit 11 or the operation input unit 13 described above, each of the image forming devices 20 (Y, M, C, K) starts with each photosensitive drum. 21 rotates in the direction indicated by arrow A, and each charging device 22 charges the surface of each photosensitive drum 21 to a required polarity (negative polarity in the first embodiment) and a potential, respectively. Subsequently, the exposure device 23 emits light on the surface of the charged photosensitive drum 21 based on the image data separated into the respective color components (Y, M, C, K) transmitted from the image processing device. Exposure is performed by irradiating LB, and electrostatic latent images of respective color components each having a required potential difference are formed. Next, each developing device 24 (Y, M, C, K) corresponds to an electrostatic latent image of each color component formed on the photosensitive drum 21 with a corresponding color (Y) charged to a required polarity (minus polarity). , M, C, K) toner is supplied and electrostatically adhered.

  The developing process at this time will be described in detail. In each developing device 24, the developing roll 242 and the agitating / conveying member 243 are rotationally driven, and the developer G accommodated in the developer accommodating portion 241 is conveyed by the agitating / conveying member 243. It is conveyed to the developing roll 24b while being stirred. The developer G that has been stirred and conveyed adheres to the developing roll 24b that rotates in the direction indicated by the arrow, and is regulated to a required thickness by the layer thickness regulating member 244, and then the developing roll 24b is separated from the photosensitive drum 21. It is conveyed to the opposite development area. The developer G (toner Gt in the first embodiment) conveyed to the development area is supplied to the photosensitive drum 21 by the developing electric field formed by the developing bias supplied between the developing roll 242 and the photosensitive drum 21 and is latent. Adhere to the image area. On the other hand, most of the developer G that has not been subjected to the development is returned to the developer container 241 by the rotating developing roll 242.

  The electrostatic latent images of the respective color components formed on the respective photosensitive drums 21 in this way are respectively developed with the corresponding color toners by passing through the respective developing devices 24, and are thus four colors (Y, M, C). , K) is visualized as a toner image. In each developing device 24, the gap between the upper edge 241a of the developing area opening in the developer container 241 and the surface of the photosensitive drum 21 is closed by the film 6 as the sealing member. Therefore, in the developing process, the developer G (toner Gt in the first embodiment) in the developer container 241 is prevented from leaking and floating from the gap portion to the side where the exposure device 23 is installed. The

  Next, the toner images of the respective colors formed on the photosensitive drums 21 of the respective image forming devices 20 (Y, M, C, K) are sequentially applied to the intermediate transfer belt 31 of the intermediate transfer device 30 by the primary transfer device 25. The primary transfer is performed so as to be superimposed on each other. Each photosensitive drum 21 after the completion of the primary transfer is cleaned by removing unnecessary materials such as toner remaining on the image holding surface by the drum cleaning device 26, and then the image holding surface is neutralized by the static eliminator 27. Is done.

  The intermediate transfer device 30 holds the toner image primarily transferred to the intermediate transfer belt 31 and conveys it to the secondary transfer position, and then the secondary transfer roll 35 is collectively fed to the paper 9 fed from the paper feeding device 40. And make secondary transfer. After the secondary transfer is completed, the intermediate transfer belt 31 is cleaned by removing unnecessary materials such as toner and paper powder remaining on the surface thereof by the belt cleaning device 36.

  The sheet 9 on which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 31 and then introduced into the fixing device 45, where it undergoes necessary fixing processing (heating and pressing), and the toner image is fixed. The sheet 9 after fixing is discharged and stored in a discharge storage section (not shown) formed in the housing 10, for example, in an image forming operation that only forms an image on one side.

  Through the above operation, the sheet 9 on which a full color image formed by combining four color toner images is output.

  Further, in the image forming apparatus 1, dust such as an external additive externally added to the toner Gt of the developer G is collected inside the housing 10 as the replacement unit is replaced. As shown in FIG. 8a, the foreign substance 101 floats and adheres to the film 6 described above after the replacement work. If the foreign matter 101 continues to adhere to and remain on the portion of the free end 6a of the film 6 that contacts the photosensitive drum 21, a streak-like image defect extending along the rotation direction A1 of the photosensitive drum 21 on the image. May occur. Incidentally, when the foreign matter 101 is placed in a high humidity environment where the humidity is relatively high, it tends to adhere to the film 6 and remain.

  Examples of the streak-like image defects include those exemplified below.

  First, as illustrated in FIG. 11a, when an image having a low image area ratio (Cin) (for example, 20% or less) is formed, the electrostatic latent image of the image exists at the free end 6a of the film 6. The potential (Vi) of the latent image portion that passes through the foreign object 101 becomes a smaller value (potential model indicated by a two-dot chain line) than the normal potential (pulse wave-like potential model indicated by the solid line), and the latent image portion is developed. As a result of the relatively small amount of developer (toner) adhering to the latent image portion of the normal latent image potential in the process, the latent image portion is white (or relatively light in density) in the entire image. ) Image defect that appears as a streak line (white streak). In FIG. 10, symbol Vh indicates a charging potential, and Vd indicates a developing potential.

  The other is that when an image having a high image area ratio (Cin) (for example, 50% or more) is formed as shown in FIG. 11b, the electrostatic latent image of the image is formed on the free end 6a of the film 6. The pixel width of the latent image portion that passes through the existing foreign matter 101 becomes a state (potential model indicated by a two-dot chain line) that is larger than the normal pixel width (pulse wave-like potential model indicated by a solid line), In the image portion, the developer (toner) adheres with a relatively wide width as compared with the latent image portion having a normal latent image potential in the development process. As a result, the density of the latent image portion in the entire image is relatively low. This is an image defect that appears as a dark streak line (color streak).

  Therefore, the image forming apparatus 1 is configured such that the control operation of the film cleaning described below is executed by the control device 5 at a required time.

  Further, in the image forming apparatus 1, as shown in FIGS. 1 and 5, a humidity measuring device 15 that measures the humidity inside the housing 10 as means for detecting information related to the timing for executing the film cleaning control operation. Is installed. As the humidity measuring device 15, for example, a measuring machine that measures relative humidity is used.

  In addition to this, as the information detecting means, a pause time measuring means 16 for measuring an elapsed time (pause time) from the end of the last image forming operation (printing) to the request of the next image forming operation. Further, the unit replacement detection means 17 for detecting the replacement of the replacement unit including the photosensitive drum 21 described above, or the number of executions of the image forming operation after replacement of the replacement unit (when forming an image on one side of the recording paper 9). The number-of-prints measurement means 18 for measuring the number of operations) is provided. For example, the pause time measuring means 16 starts measuring time after one image forming operation is completed, continuously performs the measurement until the next image forming operation is required, and the main power switch is turned off. Even a timer that works is used. As the unit replacement detection means 17, for example, a switch or a sensor that detects that an attaching / detaching operation is performed between the replacement unit and the housing 10 is used. The print count measuring means 18 uses a counter that accumulates and measures the number of executions of the image forming operation after the replacement unit obtains the replaced detection signal. More specifically, for example, the number of rotations of the photosensitive drum 21 is detected by a rotation number measuring device such as an encoder, and the obtained number of rotations is converted from the circumference of the photosensitive drum 21 to the number of recording sheets 9 of a required size. The converted value is used as the number of prints.

  The controller 5 is connected to the humidity measuring device 15 described above, and is connected to a pause time measuring means 16, a unit replacement detecting means 17, a print collection measuring means 18 and the like as necessary. Information necessary for the film cleaning control operation is input to the control device 5 from the humidity measuring device 15, the rest time measuring means 16, the unit replacement detecting means 17, the print collection measuring means 18, and the like. The drum rotation driving device 51 that transmits rotational power to the photosensitive drum 21 has a function of switching the rotation direction between the forward direction and the opposite direction, and a function of controlling the rotation amount to a predetermined amount. Yes.

  Hereinafter, the film cleaning control operation will be described.

  In the first embodiment, when the image forming operation is started, the film cleaning control operation is executed when the relative humidity S measured by the humidity measuring unit 15 is equal to or higher than a preset relative humidity threshold value X. Is set to

  That is, as shown in FIG. 6, when there is a print request instruction (step S10), the control device 5 reads the relative humidity S measured by the humidity measuring means 15 (S11), and the relative humidity at that time It is determined whether S is greater than or equal to a threshold value X (S12). As the threshold value X, for example, 75% RH which is one standard of high humidity is set.

  When it is determined that the relative humidity S is equal to or higher than the threshold value X, a film cleaning control operation is executed (S13). On the other hand, when it is determined in step S12 that the relative humidity S is less than the threshold value X or when the film cleaning control operation is completed, the requested printing operation is executed as described above (S14), and the request is made. The last printing is repeated until the end (S15).

  As shown in FIG. 7, in the film cleaning control operation, the photosensitive drum 21 in each image forming device 20 is first stopped (S20) and then the direction opposite to the rotation direction A1 in the image forming operation. A2 is reversely rotated by a required amount (S21).

  The amount of reverse rotation at this time is required to reversely rotate at least the circumference corresponding to the length E with which the outer surface of the free end 6a of the film 6 is in contact. The free end 6a is set so as to reversely rotate by a circumference corresponding to the separation distance between the image holding surface portion 21a of the photosensitive drum 21 and the developing position P2 that was in contact with the stop (S21) before the reverse rotation. (FIG. 3). Operations such as reverse rotation of the photosensitive drum 21 are performed by operating the drum rotation driving device 51 based on a control signal sent from the control device 5 to the image forming control unit 50.

  Subsequently, the control device 5 rotates the photosensitive drum 21 reversely by a necessary amount and then stops (S22), and then rotates the photosensitive drum 21 in the positive direction A1 during the image forming operation (S22). The surface portion W in the range where the free end 6a of the film 6 is in contact with the image holding surface of the photosensitive drum 21 when rotating in the reverse direction A2 is a cleaning position P3 (elastic blade in the first embodiment). It is rotated forward until it passes through the position where the contact 26b comes into contact (S23).

  The amount of forward rotation at this time is sufficient as long as the surface portion W of the image holding surface of the photosensitive drum 21 passes through at least the drum cleaning device 26 (the cleaning position P3) (FIG. 8b). In form 1, since it is a stage where a print request has been made, the process continues as it is and rotates forward (S25).

  When the film cleaning control operation is executed, unlike the image forming operation, operations related to charging by the charging device 22, formation of a latent image by the exposure device 23, development by the developing device 24, and transfer by the primary transfer device 25 are performed. I will not.

  Specifically, when the photosensitive drum 21 rotates in the reverse and forward directions in this control operation, the surface potential of the photosensitive drum 21 is not charged by the charging device 22 but is kept in a state of being neutralized by the static eliminator 27. In the developing device 24, the developing roll 242 and the like stop rotating, and the supply of the developing bias is also stopped. In the primary transfer device 25, the primary transfer bias is not applied, or the primary transfer roll is separated from the image holding surface of the photosensitive drum 21 (via the intermediate transfer belt 31). In this control operation, the intermediate transfer device 30 rotates the intermediate transfer belt 31, but stops the rotation of the intermediate transfer belt 31 when separating the primary transfer roll.

  When such a film cleaning control operation is executed, first, in the process of rotating the photosensitive drum 21 in the reverse direction, it adheres (adheres) to the outer surface of the free end 6a of the film 6 as illustrated in FIG. 8b. The foreign matter 101 is rubbed by the image holding surface of the reversely rotating photosensitive drum 21 and pulled away from the outer surface of the film, and moves to the image holding surface of the photosensitive drum 21. Next, in the step of rotating the photosensitive drum 21 in the forward direction, the foreign matter 101 transferred to the image holding surface of the photosensitive drum 21 is conveyed so as to pass through the development position P1 and the primary transfer position, and finally the drum cleaning device 26. Is removed from the image holding surface of the photosensitive drum 21.

  As described above, even if the foreign matter 101 adheres to the outer surface of the free end 6a of the film 6, the foreign matter 101 is removed from the free end 6a of the film 6 by executing the film cleaning control operation. As a result, the foreign matter 101 continues to be present at the free end 6 a of the film 6, so that a streak-like image defect due to the presence of the foreign matter 101 is less likely to occur. In the first embodiment, since the film cleaning control operation is performed particularly in a high humidity environment, it is possible to prevent the foreign matter 101 adhering to the free end 6a of the film from absorbing moisture and being easily fixed. It can be effective.

[Other embodiments]
In the first embodiment, as indicated by a two-dot chain line in FIG. 6, when the image forming operation is started, the pause time T measured by the pause time measuring means 16 is first set to a preset pause time. It is also possible to determine whether or not the threshold value Y is equal to or greater than the threshold value Y, and to perform a film cleaning control operation when the pause time Y is equal to or greater than the threshold value Y.

  That is, in this case, as shown in FIG. 6, when the control device 5 receives a print request instruction (S <b> 10), the measurement is performed by the pause time measurement means (timer) 16 that starts measurement after the last print is completed. After stopping (S34) (S31), the pause time T continuously measured by the pause time measuring means 16 is read until the next print request is made (S32). It is determined whether or not this is the case (S33). As the threshold value Y, for example, 5 hours, which is one standard for a relatively long standing time, is set.

  When it is determined that the pause time T is equal to or greater than the threshold Y, the control device 5 reads the humidity S as described above, and when the humidity S is equal to or greater than the threshold X (S11 to S12). The film cleaning control operation is executed in the same manner (S13). On the other hand, if it is determined in step S33 that the pause time T is less than the threshold value Y, or if the pause time T is greater than or equal to the threshold value Y, it is determined in step S12 that the relative humidity S is less than the threshold value X. If the film cleaning control operation is completed, the requested printing operation is executed (S14), and the requested last printing is repeated until the completion (S15).

  In this way, the judgment material (conditions) for performing the film cleaning control operation that the pause time T, which is the elapsed time from the end of the last print to the next print request, has become relatively long. ), The foreign matter 101 adhering to the free end 6a of the film is prevented from being easily fixed by being left for a long time (and being absorbed in a high humidity environment). Can be more effective. If necessary, in the first embodiment, it is possible to adopt a configuration in which the humidity S is not used as a determination material, and only the downtime T is used as a determination material.

  In the first embodiment and the other embodiments described above, when the film cleaning control operation is executed, the photosensitive drum 21 is reversely rotated in the reverse direction A2 as indicated by a two-dot chain line in FIG. Prior to this, it is possible to add an operation of causing the developing device 24 to attach the toner Gt of the developer G by a required amount to the image holding surface of the photosensitive drum 21.

  That is, as shown in FIG. 7, this configuration and the control device 5 set the photosensitive drum 21 in each image forming device 20 to the rotation stop state in the film cleaning control operation (S20), and then the image of the photosensitive drum 21. A toner image Gtb is deposited on the holding surface by the developing device 24 by a required amount to form a toner image Gtb (S40). Thereafter, the photosensitive drum 21 on which the toner image Gtb is formed is moved in the reverse direction A2 by a required amount. Only reverse rotation is performed (S21).

  The toner Gt can be attached by the developing device 24 by applying a developing bias such as a direct current to the developing roller 242 that is stopped. As a result, the toner Gt in the developer layer held on the developing roll 242 adheres to the image holding surface of the photosensitive drum 21 facing as a developing region in a state along the rotation axis direction C by electrostatic action, and forms a belt-like shape. The resulting toner image Gtb is formed (FIG. 8b). The amount of toner Gt to be attached and the size of the toner image Gtb satisfy the condition that the toner image Gtb can pass at least in contact with the free end 6a of the film when the photosensitive drum 21 is rotated in the reverse direction. I just need it.

  As described above, when the operation of attaching the toner Gt to the image holding surface of the photosensitive drum 21 is added before the photosensitive drum 21 is reversely rotated in the film cleaning control operation, when the photosensitive drum 21 is reversely rotated. Then, it is added that the toner image Gtb made of the toner Gt comes into contact with the free end 6a of the film and rubs the foreign matter 101 adhering to the free end 6a of the film. Is reliably removed. In the first embodiment, it is also possible to adopt a configuration in which the toner Gt is adhered by the developing device 24 in the process of reversely rotating the photosensitive drum 21 (S21).

  Furthermore, in the first embodiment and each of the other embodiments described above, as illustrated in FIG. 9, the replacement unit including the photosensitive drum 21 and the replacement thereof are used as judgment materials when executing the image forming operation. It is also possible to use the information of the cumulative number of prints (number of sheets) PV and the timing for executing the film cleaning control operation.

  That is, as shown in FIG. 9, when this configuration and control device 5 receives a print request instruction (S 50), it is determined whether or not replacement of the replacement unit including the photosensitive drum 21 is detected by the unit replacement detection unit 17. Confirm (S51). If it is confirmed that the replacement unit has been replaced at this time, after the last printing is finished, the number of prints PV when the number of times of printing is counted by the number-of-prints measuring means 18 (S59) is read (S52) and then the number of prints at that time It is determined whether PV is a threshold value Z or more (S53). As the threshold value Z, for example, 2000 sheets (pages) are set.

  When it is determined that the number of printed sheets PV is equal to or greater than the threshold value Z, the humidity S (further pause time T) is read as described above (S54), and the humidity S is equal to or greater than the threshold value X (and the pause time T is equal to or less than the threshold value Z). When it is equal to or greater than the threshold value Y (S55), the film cleaning control operation is similarly executed (S56). On the other hand, if it is confirmed in step S51 that the replacement unit has not been replaced, or if it is determined in step S53 that the number of printed sheets PV is less than the threshold Z even if the replacement unit has been replaced, or the number of printed sheets Even if PV is greater than or equal to the threshold value Z, if it is determined in step S55 that the humidity S is less than the threshold value X (or the pause time T is less than the threshold value Y), or if the film cleaning control operation is completed, a request is made. The requested printing operation is executed (S57), and the requested last printing is repeated until the end (S58).

  As described above, when the replacement unit including the photosensitive drum 21 is replaced, the film cleaning control operation can be performed, and when the number of printed sheets PV after the replacement reaches the threshold value Z, the control operation is not required to be performed. When the control operation judgment material is added, dust, toner external additives, etc. float when the replacement unit is replaced, and it becomes easier to newly adhere to the free end 6a of the film as foreign matter 101. It is possible to prevent the foreign matter 101 from being newly attached, which is more effective. Further, when the number of printed sheets PV after replacement of the replacement unit is equal to or greater than the threshold value Z, it is considered that there is no foreign matter 101 adhering (adhering) to the free end 6a of the film, and thereafter the film cleaning control operation is not executed. Unnecessary increase in waiting time before starting printing can be avoided.

  In addition, in the first embodiment and each of the other embodiments, the film control operation is executed at the time when the image forming operation is finished instead of or in addition to the time before the image forming operation is started. It is also effective to configure this. The replacement unit may be configured as a replacement unit having contents including one or both of the photosensitive drum 21 and the developing device 24. Further, instead of measuring the number of printing operations PV after replacement of the replacement unit, it is also possible to adopt the accumulated number of rotations of the photosensitive drum 21 after the replacement.

  Further, the attachment state of the film 6 as the seal member is not particularly limited as long as there is a possibility that the foreign matter 101 such as dust adheres and continues to exist. As another example, for example, as illustrated in FIG. 10, the film 6 is placed on the lower edge 241 b of the developing opening in the developer container 241 of the developing device 24, and the free end 6 a is the photosensitive drum 21. The thing which installed and attached in the state which contacts the surface of is mentioned. An image forming apparatus 20 illustrated in FIG. 10 is disposed downstream of the intermediate transfer apparatus 30 (intermediate transfer belt 31) in the direction of gravity. Further, the object to which the film 6 is fixed is not limited to a part of the developing device 24 (the developing container 241), and the section where the free end 6a contacts is from the latent image forming position P1 to the developing position P2. It will not be specifically limited if it becomes either of the area of.

  Further, the image forming apparatus 1 may be a color image forming apparatus of another formation or a single color image forming apparatus that forms a single color (mainly black and white) image. In addition, a latent image holding member such as a belt-shaped photosensitive member can be used in place of the photosensitive drum 21.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 5 ... Control apparatus (control means)
6 ... Film 6a ... Free end 9 ... Recording paper (recording medium member)
15 ... Humidity measuring part (humidity measuring means)
16 ... Rest time measuring unit (time measuring means)
17 ... Unit replacement detection part (detection means)
18: Print count measuring unit (rotation amount measuring means)
21 ... Photosensitive drum (latent image carrier)
21a... Surface portion 23 in contact with free end of film 23. Exposure device (latent image forming device)
24 ... Developer 25 ... Primary transfer device (transfer device)
26 ... Drum cleaning device (cleaning device)
29 ... Toner density detection sensor (density detection means)
31. Intermediate transfer belt (intermediate transfer member)
G: Developer A1: Direction of rotation during image formation (predetermined direction)
A2 ... Reverse rotation direction (reverse direction)
P1 ... Latent image forming position P2 ... Developing position E ... Length with which the free end of the film is in contact

Claims (6)

A latent image holding body having a surface for holding an electrostatic latent image and rotating in a predetermined direction;
A latent image forming apparatus for forming an electrostatic latent image on the surface of the latent image holding member;
A developing device that develops the electrostatic latent image with a developer to form a developer image;
A transfer device for transferring the developer image formed on the surface of the latent image holding member to a recording member or an intermediate transfer member;
A cleaning device that removes and cleans unnecessary objects attached to the surface of the latent image holder;
A film installed with a free end in contact with any position in a section from the latent image forming position by the latent image forming device to the developing position by the developing device on the surface of the latent image holding member; ,
The surface on which the free end of the film is in contact when rotating in the opposite direction of the surface of the latent image holding member after rotating the latent image holding member in the opposite direction to the predetermined direction. An image forming apparatus, comprising: a control unit that executes a control operation of rotating in a predetermined direction at least until a portion passes through the cleaning device at a required time.   2. The image forming apparatus according to claim 1, wherein in the control operation, the control unit rotates the latent image holding member in the opposite direction by at least a circumferential length corresponding to a length that a free end of the film is in contact with. .   The control means adds an operation of attaching a developer from the developing device to the surface of the latent image holding body before or when the latent image holding body is rotated in the opposite direction in the control operation. The image forming apparatus according to claim 1, wherein the image forming apparatus is performed. Humidity measuring means for measuring the humidity inside the image forming apparatus is provided,
4. The control unit according to claim 1, wherein the control unit executes the control operation before or after the image forming operation when the humidity measured by the humidity measuring unit has reached a preset value. The image forming apparatus according to claim 1. A time measuring means for measuring an elapsed time from the end of the last image forming operation to the request for the next image forming operation;
5. The control unit according to claim 1, wherein the control unit executes the control operation before a next image forming operation is started when an elapsed time measured by the time measurement unit exceeds a preset value. The image forming apparatus according to claim 1. One or both of the latent image holding member and the developing device including the replacement unit, an exchange unit configured to be attached and detached, detection means for detecting that the replacement unit has been changed, and the latent image holding member A rotation amount measuring means for accumulating and measuring the rotation amount;
The control unit enables the control operation to be executed when the detection unit detects the replacement of the replacement unit, and the latent image measured by the rotation amount measurement unit after the replacement unit is detected. The image forming apparatus according to claim 1, wherein the control operation is not required to be executed when the rotation amount of the holding body reaches a preset value.

Images