JP2017010010A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology that can reduce a situation where a coating agent coated on a developer carrier moves to a recording material together with a developer image.SOLUTION: An image forming apparatus comprises: a photoreceptor drum 1 for carrying a developer image; a developing device 4 including a developing roller 17 that carries a developer and a developing blade 21 that regulates the amount of a developer on the developing roller 17; and a detection part 100B that detects information on the amount of a developer stored in the developing device 4. The image forming apparatus performs a discharge operation for discharging a coating agent coated on the developing roller 17 before being used from the developing device 4 to the photoreceptor drum 1 while changing an operation condition for the discharge operation on the basis of the information.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus using an electrophotographic process.

  In an image forming apparatus such as a printer using an electrophotographic image forming method (electrophotographic process), an electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) as an image bearing member is uniformly charged, and the charged photosensitive member. An electrostatic image is formed on the photoreceptor by selectively exposing the body. The electrostatic image formed on the photoconductor is visualized as a toner image with the toner of the developer. The toner image formed on the photoconductor is transferred to a recording material such as recording paper or a plastic sheet, and the toner image is applied to the recording material by applying heat or pressure to the toner image transferred onto the recording material. Image recording is performed by fixing.

  Such an image forming apparatus generally requires replenishment of developer and maintenance of various process means. In order to facilitate the replenishment of the developer and maintenance of various process means, the photosensitive member, the charging means, the developing means, the cleaning means, etc. are collectively assembled into a cartridge, and a process that can be attached to and detached from the image forming apparatus main body. A cartridge has been put into practical use. According to the process cartridge system, an image forming apparatus having excellent usability can be provided.

  2. Description of the Related Art Conventionally, in a developing device used in an image forming apparatus, a coating agent (lubricant) is applied to a developing roller (developer carrying member) for the purpose of suppressing the peeling of a regulating blade (developer regulating member) and reducing driving torque. This method is widely used. In Patent Document 1, a powder having the same polarity as the toner is used as a coating agent for the developing roller. In Patent Document 2, as a coating agent, at least the surface of a toner supply roller (developer supply member) is a powder having a charging ability of 0, or charged to the same polarity as the developer, and the absolute value of the charging ability is the developer. It has been proposed to apply a powder that is equal to or less than the charging ability of the above. On the other hand, in the conventional image forming apparatus, a technique for regularly discharging the developer is widely known for the purpose of suppressing the deterioration of the developer. Japanese Patent Application Laid-Open No. 2004-260260 discloses a device that periodically discharges the developer so that the toner consumption for each page is constant for the purpose of suppressing toner deterioration of the developer.

JP-A-2-298971 JP-A-8-227212 JP 2006-23327 A

  When the coating agent is used as in Patent Documents 1 and 2, the initial coating agent remaining in the developing chamber in the latter half of the life in which the charging characteristics of the toner deteriorate due to the durability deterioration of the developer and the durability deterioration of the developing roller and the developing blade. When the image is formed, the toner image may move to the recording material. Thus, the coating agent adhering to the recording material may appear as a streak image on the image or appear as a streaky fog image on a white background on paper. For this reason, it is desirable that the coating agent initially applied to the developing roller is promptly discharged out of the developing chamber.

However, with the conventional discharge method and discharge frequency as disclosed in Patent Document 3, the coating agent may not be discharged completely, and may remain in the developing chamber. In this way, when image formation is performed with the coating agent remaining in the developing chamber, the coating agent is used together with the toner image on the recording material in a situation where the charging characteristics of the toner deteriorate due to deterioration of the durability of the developer or deterioration of the developing roller. There was a case to move. Also in this case, there is a concern that abnormal images such as streaks and fogging may occur.

  An object of the present invention is to provide a technique capable of reducing the movement of a coating agent applied to a developer carrier to a recording material together with a developer image.

In order to achieve the above object, an image forming apparatus of the present invention includes:
An image carrier for carrying a developer image;
A developing device having a developer carrying member carrying the developer, and a regulating member regulating the amount of developer on the developer carrying member;
A detecting unit for detecting the amount of developer contained in the developing device;
A control unit that performs a discharge operation for discharging the developer from the developing device separately from the image forming operation;
The developer carrier carries a coating agent when not in use,
In the discharge operation, the discharge amount when the first developer storage amount is detected is the second discharge amount when the second developer storage amount larger than the first developer storage amount is detected. It is characterized by being larger than the amount of discharge.
In order to achieve the above object, the image forming apparatus of the present invention includes:
A developing device that includes a developer carrying member that carries the developer, and a regulating member that regulates the amount of the developer and applies a charge to the developer carried on the developer carrying member;
A detector that detects the amount of developer contained in the developing device,
An image forming apparatus that performs an ejection operation for moving a developer from the developer carrier to the image carrier, which is different from an image forming operation for forming a developer image on a recording material,
The developer carrier is coated with a coating agent made of powder different from the developer when not in use,
A control unit is provided that changes the execution frequency so that the smaller the developer storage amount detected by the detection unit, the higher the execution frequency of the discharge operation for the image forming operation.

  According to the present invention, it is possible to reduce the movement of the coating agent applied to the developer carrier to the recording material together with the developer image.

Schematic sectional view of an image forming apparatus according to an embodiment Schematic sectional view of the process cartridge in the embodiment Schematic sectional view of the developing device in the embodiment Flow chart of discharge operation in embodiment 1 Flow chart of discharge operation in embodiment 2 Flow chart of discharge operation in embodiment 3 Flow chart of discharge operation in embodiment 4 Table showing comparative verification results in Examples The graph which shows the comparison verification result in the example The figure for demonstrating the effect of an Example

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

(Example)
An electrophotographic image forming apparatus according to an embodiment of the present invention will be described. Here, an electrophotographic image forming apparatus (hereinafter also simply referred to as “image forming apparatus”) uses an electrophotographic image forming method to form an image using a developer (hereinafter also referred to as “toner”) on a recording material. To form. Examples of the image forming apparatus include a copying machine, a printer (laser beam printer, LED printer, etc.), a facsimile machine, a word processor, and a multifunction machine (multifunction printer) thereof.

  Further, in this specification, the terms representing the directions such as up, down, vertical, and horizontal for the configuration and operation of the developing unit (or developing device) or the process cartridge are used in a normal manner unless otherwise specified. Indicates the direction when viewed in the state. In other words, the normal use state of the developing unit (or developing device) or process cartridge is a state in which the developing unit (or developing device) or the process cartridge is properly attached to the properly arranged image forming apparatus main body and can be used for an image forming operation.

[Image forming apparatus]
FIG. 1 is a schematic cross-sectional view illustrating the overall configuration of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 of this embodiment is a full-color laser printer that employs an inline method and an intermediate transfer method. The image forming apparatus 100 can form a full color image on a recording material (for example, recording paper, plastic sheet, cloth) according to the image information. The image information is input to the image forming apparatus main body 100A from an image reading apparatus connected to the image forming apparatus main body 100A or a host device such as a personal computer connected to the image forming apparatus main body 100A so as to be communicable.

  The image forming apparatus 100 includes, as a plurality of image forming units, first, second, and third images for forming yellow (Y), magenta (M), cyan (C), and black (K) images, respectively. And fourth image forming units SY, SM, SC, and SK. In the present embodiment, the first to fourth image forming units SY, SM, SC, and SK are arranged in a line in a direction that intersects the vertical direction. In the present embodiment, the configurations and operations of the first to fourth image forming units SY, SM, SC, and SK are substantially the same except that the colors of images to be formed are different. Therefore, in the following, unless there is a particular distinction, the subscripts Y, M, C, and K given to the reference numerals to indicate that they are elements provided for any color are omitted, and generally explain. Of course, depending on the configuration, an image forming apparatus provided with image forming units having different sizes and shapes may be used.

  The image forming apparatus 100 includes, as a plurality of image carriers, four drum-type electrophotographic photosensitive members, that is, photosensitive drums 1 arranged in parallel in a direction intersecting the vertical direction. The photosensitive drum 1 is rotationally driven by an unillustrated driving means (driving source) in the illustrated arrow A direction (clockwise direction). Around the photosensitive drum 1, a charging roller 2 as a charging means for uniformly charging the surface of the photosensitive drum 1, a laser is irradiated based on image information, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 1. A scanner unit (exposure device) 3 is disposed as an exposure means for forming the. Further, around the photosensitive drum 1, a developing unit (developing device) 4 as developing means for developing the electrostatic image as a toner image, and toner (transfer residual toner) remaining on the surface of the photosensitive drum 1 after transfer are removed. A cleaning member 6 is disposed as a cleaning means. Further, an intermediate transfer belt 5 as an intermediate transfer body for transferring a toner image (developer image) on the photosensitive drum 1 to the recording material 12 is disposed opposite to the four photosensitive drums 1.

In this embodiment, the developing unit 4 uses a non-magnetic one-component developer toner as the developer. In this embodiment, the developing unit 4 performs reverse development by bringing a developing roller (described later) as a developer carrying member into contact with the photosensitive drum 1. That is, in this embodiment, the developing unit 4 is a portion (image portion) in which the charge is attenuated by exposure on the photosensitive drum 1 with the toner charged to the same polarity (negative polarity in this embodiment) as the charging polarity of the photosensitive drum 1. , The electrostatic image is developed by adhering to the exposed portion.

  In this embodiment, the photosensitive drum 1 and the charging roller 2, the developing unit 4 and the cleaning member 6 as process means acting on the photosensitive drum 1 are integrated, that is, integrated into a cartridge, and processed into a process cartridge. 7 is formed. The process cartridge 7 can be attached to and detached from the image forming apparatus 100 via mounting means such as a mounting guide and a positioning member provided in the image forming apparatus main body 100A. In this embodiment, the process cartridges 7 for the respective colors all have the same shape, and each of the process cartridges 7 for each color has yellow (Y), magenta (M), cyan (C), and blank ( K) toner of each color is accommodated.

  The intermediate transfer belt 5 formed of an endless belt as an intermediate transfer member is in contact with all the photosensitive drums 1 and circulates (rotates) in the direction of the arrow B (counterclockwise) in the figure. The intermediate transfer belt 5 is wound around a driving roller 51, a secondary transfer counter roller 52, and a driven roller 53 as a plurality of support members.

  On the inner peripheral surface side of the intermediate transfer belt 5, four primary transfer rollers 8 serving as primary transfer units are arranged in parallel so as to face the respective photosensitive drums 1. The primary transfer roller 8 presses the intermediate transfer belt 5 toward the photosensitive drum 1 to form a primary transfer portion N1 where the intermediate transfer belt 5 and the photosensitive drum 1 abut. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer roller 8 from a primary transfer bias power source (high voltage power source) as a primary transfer bias applying unit (not shown). As a result, the toner image on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 5.

  A secondary transfer roller 9 as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 52 on the outer peripheral surface side of the intermediate transfer belt 5. The secondary transfer roller 9 is pressed against the secondary transfer counter roller 52 via the intermediate transfer belt 5 to form a secondary transfer portion N2 where the intermediate transfer belt 5 and the secondary transfer roller 9 come into contact. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 9 from a secondary transfer bias power source (high voltage power source) as a secondary transfer bias applying unit (not shown). As a result, the toner image on the intermediate transfer belt 5 is transferred (secondary transfer) to the recording material 12.

  At the time of image formation, first, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. Next, the surface of the charged photosensitive drum 1 is scanned and exposed by laser light corresponding to the image information emitted from the scanner unit 3, and an electrostatic image according to the image information is formed on the photosensitive drum 1. Next, the electrostatic image formed on the photosensitive drum 1 is developed as a toner image by the developing unit 4. The toner image formed on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 5 by the action of the primary transfer roller 8. For example, when a full-color image is formed, the above-described process is sequentially performed in the first to fourth image forming units SY, SM, SC, and SK, and the toner images of the respective colors are superimposed on the intermediate transfer belt 5 to be primary. Transcribed.

Thereafter, the recording material 12 is conveyed to the secondary transfer portion N2 in synchronization with the movement of the intermediate transfer belt 5. The four color toner images on the intermediate transfer belt 5 are secondarily transferred onto the recording material 12 collectively by the action of the secondary transfer roller 9 that is in contact with the intermediate transfer belt 5 via the recording material 12. The recording material 12 onto which the toner image has been transferred is conveyed to a fixing device 10 as a fixing unit. The toner image is fixed on the recording material 12 by applying heat and pressure to the recording material 12 in the fixing device 10.

  Further, the primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer process is removed and collected by the cleaning member 6. The secondary transfer residual toner remaining on the intermediate transfer belt 5 after the secondary transfer process is cleaned by the intermediate transfer belt cleaning device 11. Note that the image forming apparatus 100 can form a single-color or multi-color image using only one desired image forming unit or using only some (not all) image forming units. It is like that.

[Process cartridge]
With reference to FIG. 2, the overall configuration of the process cartridge 7 mounted on the image forming apparatus 100 will be described. FIG. 2 is a schematic cross-sectional view (main cross-sectional view) of the process cartridge 7 of this embodiment viewed along the longitudinal direction (rotational axis direction) of the photosensitive drum 1. In the present embodiment, the configuration and operation of the process cartridge 7 for each color are substantially the same except for the type (color) of the developer stored therein. The process cartridge 7 is configured by integrating a photosensitive unit 13 including the photosensitive drum 1 and the like, and a developing unit 4 including the developing roller 17 and the like.

  The photoconductor unit 13 has a cleaning frame 14 as a frame that supports various elements in the photoconductor unit 13. The photosensitive drum 1 is rotatably attached to the cleaning frame 14 via a bearing (not shown). The photosensitive drum 1 is rotationally driven in the direction of the arrow A (clockwise) in accordance with the image forming operation by transmitting the driving force of a driving motor (not shown) as a driving means (driving source) to the photosensitive unit 13. The In this embodiment, the photosensitive drum 1 that is the center of the image forming process is an organic photosensitive drum 1 in which an outer surface of an aluminum cylinder is coated with a functional undercoat layer, a carrier generation layer, and a carrier transfer layer in this order. Used.

  In the photosensitive unit 13, a cleaning member 6 and a charging roller 2 are disposed so as to come into contact with the peripheral surface of the photosensitive drum 1. The transfer residual toner removed from the surface of the photosensitive drum 1 by the cleaning member 6 falls and is stored in the cleaning frame 14 (cleaning unit).

  The charging roller 2 as charging means is driven to rotate by bringing the roller portion of conductive rubber into pressure contact with the photosensitive drum 1. As a charging process, a predetermined DC voltage is applied to the core of the charging roller 2 with respect to the photosensitive drum 1, whereby a uniform dark portion potential (Vd) is formed on the surface of the photosensitive drum 1. The The spot pattern of the laser beam emitted corresponding to the image data by the laser beam from the scanner unit 3 described above exposes the photosensitive drum 1, and the exposed portion is charged on the surface by the carrier from the carrier generation layer. Disappears and the potential drops. As a result, an electrostatic latent image is formed on the photosensitive drum 1 with a predetermined light portion potential (Vl) at an exposed portion and a predetermined dark portion potential (Vd) at an unexposed portion. In this embodiment, Vd = −520V and Vl = −100V.

  The development unit 4 is a development in which a development roller 17 as a developer carrier for carrying a developer (toner) 80 and a toner supply roller 20 as a developer supply member for supplying toner to the development roller 17 are arranged. Room. Further, the developing unit 4 is disposed below the toner supply roller 20 in the gravitational direction, and is connected to the developing chamber and the developing opening 33 to store the toner 80, that is, the toner storing chamber 18 (developer). Containment section). The toner supply roller 20 is in contact with the developing roller 17 with the nip portion N and rotating.

In the toner storage chamber 18, the toner stored in the toner storage chamber 18 is agitated, and the toner is transported in the direction of arrow G in the figure toward the upper portion of the toner supply roller 20 and the region indicated by V. The agitating and conveying member 22 is provided.

In this embodiment, a developing blade is used as a regulating member that regulates the amount of developer on the developer carrying member.
The developing blade 21 is disposed below the developing roller 17 and is in contact with the developing roller 17 in the counter direction, and regulates the coating amount of toner supplied by the toner supply roller 20 and applies electric charge. In this embodiment, a SUS thin plate having a thickness of 0.1 mm is used as the developing blade 21, a contact pressure is formed by utilizing the spring elasticity of the thin plate, and the surface thereof is toner and the developing roller 17. Is brought into contact with the surface. The developing blade is not limited to this and may be a thin metal plate such as phosphor bronze or aluminum. Alternatively, the surface of the developing blade 21 may be coated with a thin film such as polyamide elastomer, urethane rubber, or urethane resin. The toner is triboelectrically charged by rubbing between the developing blade 21 and the developing roller 17 to be charged, and at the same time the layer thickness is regulated. In this embodiment, a predetermined voltage is applied to the developing blade 21 from a blade bias power source (not shown) to stabilize the toner coat. In this example, V = −400 V was applied as the blade bias.

  The developing roller 17 and the photosensitive drum 1 rotate so that the surfaces of the developing roller 17 and the photosensitive drum 1 move in the same direction (in this embodiment, the direction from the bottom to the top) in the opposing portion (contact portion). In this embodiment, the developing roller 17 is disposed in contact with the photosensitive drum 1. However, the developing roller 17 may be disposed close to the photosensitive drum 1 at a predetermined interval. Good. In the present embodiment, the toner charged negatively by frictional charging with respect to a predetermined DC bias applied to the developing roller 17 from the bias power source 17c in the developing unit that comes into contact with the photosensitive drum 1 from the potential difference, the bright portion. The electrostatic latent image is visualized by transferring only to the potential portion. In this embodiment, by applying V = −300 V to the developing roller, a potential difference from the bright portion potential portion is formed to be ΔV = 200 V, and a toner image is formed.

  The toner supply roller 20 is disposed with a predetermined contact portion (nip portion) N formed on the peripheral surface of the developing roller 17 at the opposing portion, and rotates in the direction of the arrow E (clockwise) in the figure. The toner supply roller 20 is an elastic sponge roller in which a foam layer is formed on the outer periphery of a conductive metal core. The toner supply roller 20 and the developing roller 17 are in contact with each other with a predetermined amount of penetration, that is, in FIG. The contact portions N rotate with the circumferential speed difference in the same direction, and the toner is supplied to the developing roller 17 by the toner supply roller 20 by this operation. At this time, the toner supply amount to the developing roller 17 can be adjusted by adjusting the potential difference between the toner supplying roller 20 and the developing roller 17. In this embodiment, the toner supply roller 20 is driven and rotated at 200 rpm and the developing roller 17 is rotated at 100 rpm, and a DC bias is applied so that the potential of the developing roller 17 becomes V = + 50 V with respect to the potential of the toner supply roller 20. Yes.

The developing roller 17 and the toner supply roller 20 in this embodiment both have an outer diameter of 15 mm, and the amount of penetration of the toner supply roller 20 into the development roller 17, that is, the toner supply roller 20 is recessed by the development roller 17. The dent amount ΔE was set to 1.0 mm. Further, the toner supply roller 20 and the developing roller 17 are arranged so that the center height is the same. The toner supply roller 20 used in this embodiment includes a conductive support and a foam layer supported by the conductive support. Specifically, a foamed urethane layer as a foamed layer composed of a cored bar electrode 20a having an outer diameter of φ5 (mm), which is a conductive support, and an open cell body (open cells) in which bubbles are connected to the periphery thereof. 20b is provided and rotates in the direction E in the figure. A large amount of toner can enter the inside of the toner supply roller 20 by using urethane on the surface layer as an open cell body. Further, the resistance of the toner supply roller 20 in this embodiment is 1 × 10 ⁹ (Ω). As will be described later, a coating agent having a lubricating action is applied to the surface of the developing roller when not in use.

  Here, a method of measuring the resistance of the toner supply roller 20 will be described. The toner supply roller 20 is brought into contact with an aluminum sleeve having a diameter of 30 mm so that an intrusion amount described later becomes 1.5 mm. By rotating the aluminum sleeve, the toner supply roller 2 is driven to rotate relative to the aluminum sleeve at 30 rpm. Next, a DC voltage of −50 V is applied to the aluminum sleeve. At that time, a resistance of 10 kΩ is provided on the ground side, the current is calculated by measuring the voltage at both ends, and the resistance of the toner supply roller 20 is calculated. In this embodiment, the surface cell diameter of the toner supply roller 20 is set to 50 μm to 1000 μm.

  Here, the cell diameter means the average diameter of the foamed cells having an arbitrary cross section. First, the area of the foamed cell that is the maximum is measured from the enlarged image of the arbitrary cross section, and the maximum cell diameter is converted from this area by converting the equivalent circle diameter. Get. And after deleting the foam cell which is 1/2 or less of this maximum cell diameter as noise, it points out the average value of each cell diameter converted similarly from the remaining individual cell area.

  Next, toner circulation in the developing chamber when the toner supply roller 20 rotates in the direction of the arrow E in the figure will be described. First, the toner accommodated in the toner accommodating portion 18 is splashed up by the toner conveying member 22, and most of the toner is conveyed to the upper portion of the supply roller 20. The toner conveyed to the supply roller 20 remains on the surface and inside of the supply roller 20. Then, the feed roller 20 is conveyed until just before the nip with the developing roller 17 by the rotation in the direction of arrow E in the drawing. The portion of the supply roller 20 where the toner is conveyed is deformed immediately before the nip with the developing roller 17, and the toner remaining on the surface and inside is discharged by the deformation. The discharged toner is stored in a space above the developing roller 17 and the supply roller 20 (hereinafter referred to as “temporary toner storage portion V”).

  A part of the toner stored in the temporary toner storage portion V enters the nip portion N by the rotation of the developing roller 17 and the supply roller 20. The toner that has entered the nip portion N is given an electric charge by rubbing between the developing roller 17 and the supply roller 20. After having passed through the nip portion N, the charged toner is electrostatically attracted to the developing roller 17 by its own charge amount. As a result, the toner is supplied from the supply roller 20 to the developing roller 17. Then, a part of the toner supplied to the developing roller 17 is regulated by the developing blade 21 which is a developer regulating member, thereby forming a toner coat having a desired layer thickness on the developing roller 17. Further, the regulated toner falls due to gravity and returns to the toner storage unit 18.

  As described above, the toner coat is formed by supplying the toner stored in the temporary toner storage portion V to the developing roller 17. That is, in order to stably form a toner coat, it is necessary to have a configuration in which a desired amount of toner is continuously supplied to the temporary toner storage portion V stably.

[Coating agent]
Next, the coating agent applied to the developing roller 17 in this embodiment will be described in detail. The developing roller 17 of the present embodiment has a purpose of protecting the developing roller 17 from the manufacture to the start of use by the user and functioning as a lubricant for the developing blade 21 at the start of use. A powder different from the toner is used as the coating agent. About 10 to 150 mg of this coating agent is applied to the developing roller 17. In this example, Toshiba Silicone Tospearl (trade name) was used as the powder used for the coating agent 22. The average particle size is 2 μm. The coating agent employed in this example has a feature that the charge is higher than that of the toner used for development. Specifically, in a greenhouse temperature environment of 23 ° C. and 40%, the average charge per unit mass of toner was about 50 μC / g, and the average charge per unit mass of Tospearl was 90 μC / g. As the developer, a conventionally known developer can be appropriately used as long as it is a non-magnetic one-component developer and has a charging property lower than that of the coating agent as described above. The average particle diameter of the developer is preferably larger than that of the coating agent.

  In the present embodiment, Tospearl having a particle diameter of 2 μm is used. However, the present invention is not limited to this, and any suitable one can be used as long as the developing blade 21 functions as a lubricant without turning up. Specifically, examples of the material and particle size used for the coating agent include the following in consideration of electrical characteristics with the developing roller 17 and the developing blade 21. Examples of the material include urethane resin, silicone resin, polyester resin, styrene resin, acrylic resin, styrene-acrylic resin, or a blend resin thereof. After kneading a charge control agent, wax, or the like in these resins, mother particles are formed by pulverization by a known pulverization method. Further, an external additive may be added. Further, regarding the particle size, a combination of 0.8 μm to 10 μm is possible as appropriate.

[Developer filling amount]
With reference to FIGS. 3A to 3C, the amount of the developer filled in the developing device 4 in this embodiment will be described in detail. The developing device 4 of this embodiment has three levels with different toner filling amounts. In other words, the image forming apparatus according to the present embodiment is configured such that three types of developing devices 4 having different toner filling amounts in the toner chamber in an unused state (initial) are detachable from the apparatus main body 100A. 3A to 3C are schematic cross-sectional views of the developing device 4 in this embodiment. FIG. 3A is a type in which the initial filling amount of the developer is 240 g, and FIG. FIG. 3C shows a developing device 4 of a type of 150 g and FIG. The user can appropriately select which type of developing device 4 is attached to the apparatus main body 100A according to the use frequency and cost, and provides a degree of freedom.

  Information regarding the filling amount of the developing device 4 is held in the nonvolatile memory 200 as information unique to the developing device. The non-volatile memory 200 is, for example, a rewritable flash ROM, a system program for controlling the image forming apparatus, the number of recording sheets on which an image is recorded, information on the life of the developing device, information on the remaining amount of toner, Various adjustment values and the like are stored. The nonvolatile memory 200 also stores system data indicating the serial number of the device, production date, and the like. In addition to these pieces of information, the nonvolatile memory 200 stores information relating to the filling amount of the developing device as information unique to the developing device.

  In this embodiment, the information regarding the toner filling amount is based on the filling amount held in the nonvolatile ROM, but the information for determining the filling amount is not limited to this. For example, any information that can determine the difference in the amount of toner filling, such as the nominal life of the developing device, the number of printable sheets, the life rotation speed of the developing roller, the usable toner amount, the life rotation speed of the photosensitive drum, can be appropriately replaced. is there. In the present embodiment, the information on the developer filling amount is used, but information on the developer amount stored in an unused developing device (new developing device) may be held in the nonvolatile memory 200.

[Filling amount detection means]
In the image forming apparatus, a CPU 100B (FIG. 2) is arranged as a central processing unit. The CPU is a control unit that reads various adjustment values from a non-volatile memory attached to the developing device and controls the image forming apparatus. Information on the initial filling amount of the developing device is also detected by the CPU from the nonvolatile memory, and a discharge control program determined in advance for each filling amount is selected and controlled. In this embodiment, the toner filling amount of the developing device is determined based on the information in the nonvolatile memory. However, the present invention is not limited to this. For example, it is also possible to appropriately detect the toner filling amount by changing the container shape (for example, rib) of the developing device for each toner filling amount and detecting the difference in the container shape by the image forming apparatus.

[Discharge control]
Next, the control for discharging the coating agent in the present embodiment will be described in detail. Most of the coating material applied to the developing roller 17 at the beginning of use of the developing device is collected on the surface of the toner supply roller 20 and inside thereof due to rotational friction between the developing roller 17 and the toner supply roller 20. The

  Further, since the coating agent of this embodiment has a feature that the electric charge is higher than that of the toner, it is necessary to perform discharge control with a potential setting different from that during normal image formation. That is, a potential difference having a polarity opposite to the charging polarity of the coating agent charged with the developing blade 21 and having an absolute value larger than the potential difference during the image forming operation is formed. Specifically, the toner supply roller 20 is supplied with a bias power supply 20c and the development roller 17 is supplied with a bias power supply 17c so that the potential of the developing roller 17 becomes V = + 300V with respect to the potential of the toner supply roller 20, respectively. A bias is applied. The bias power supplies 20c and 17c and the CPU 100B that controls the bias application to the toner supply roller 20 and the developing roller 17 correspond to the voltage application unit of the present invention. Since Tospearl as the coating agent used in this embodiment has higher charging characteristics than the toner in the toner storage chamber 18, the coating agent is electrostatically supplied to the developing roller 17 having an apparent potential. Thus, by setting the potential based on the electrical characteristics of the coating agent, the coating agent remaining in the toner supply roller 20 can be positively supplied to the developing roller 17.

  In this way, the coating agent collected on the developing roller 17 moves together with the toner to the photosensitive drum 1 by performing a solid black image forming operation for one rotation of the developing roller 17 and is collected in the cleaner container. The By this operation, the amount of the coating agent remaining in the developing chamber can be surely reduced. Further, this discharge control also serves to supply the cleaning member 6 as a lubricant. At this time, since the intermediate transfer belt 5 is separated from the photosensitive drum 1, all the toner moved from the developing device 4 to the photosensitive drum 1 is collected by the cleaning member 6.

  In this example, since the coating agent having a higher charging characteristic than the toner was used, the above-described potential was used. However, the present invention is not limited to this, and discharge is efficiently performed according to the electrical characteristics of the coating agent. It is also possible to set the potential to be performed.

[Toner discharge control flow]
With reference to FIG. 4, the toner discharge control in the first embodiment will be described. FIG. 4 is a flowchart illustrating the discharge operation according to the first embodiment. In this embodiment, as described below, the CPU of the image forming apparatus sets the operating conditions of the discharge operation to (4) t4, (12) t11, (15) t13 according to the initial filling amount information in the nonvolatile memory. Switch to the three. In particular, the control program for the discharge operation is characterized in that the coating agent is discharged more positively as the initial filling amount is smaller. In this embodiment, the discharge frequency is set to a predetermined count of the number of printed sheets, and a developing device with a small filling amount is controlled to discharge with a smaller printing count than a developing device with a large filling amount. Yes.
In this embodiment, the CPU 100B corresponds to a storage amount detection unit that detects an initial toner filling amount (storage amount) of the developer in the present invention. Furthermore, in this embodiment, the CPU 100B also serves as a discharge control unit that changes the execution frequency (operation condition) of the discharge operation, a count unit that counts the number of times of image forming operation execution, a life detection unit, a remaining amount detection unit, and the like. .

(1) The toner filling amount of the developing device is detected by the image forming apparatus by the filling amount detecting means (t1).
(2) As a result of detection, the filling amount is 100 g (t2).
(3) It is sent to the toner discharge control means that the detection result is 100 g (t3).
(4) The discharge frequency of every 100 sheets at 100 g is selected by the detection means (t4).
(5) Normal image formation is performed (t5).
(6) A counter is added for each image formation (t6).
(7) After a certain number of sheets have elapsed, the count of the counter reaches a predetermined count number (t7).
(8) The discharge control means detects the arrival of the counter and performs the discharge operation (t8).
(9) After the discharge operation is completed, the counter is reset to 0 (t9).
(10) Thereafter, the process returns to (t5) and loops from (t5) to (t9).
(11) In (t2), a detection result of 150 g is sent to the toner discharge control means (t10).
(12) The discharge frequency of every 300 sheets at 150 g is selected by the detection means (t11).
(13) After that, the loop is repeated from (t5) to (t9) as in the case of 100 g.
(14) It is sent to the toner discharge control means that the detection result is 240 g at (t2) (t12).
(15) The discharge frequency of every 600 sheets at 240 g is selected by the detection means (t13).
(16) Thereafter, the loop is repeated from (t5) to (t9) as in the case of 100 g.

<Comparison verification>
About the structure of the Example of this invention, in order to verify the effect of the discharge performance of a coating agent, it verified using this Example and the following comparative examples. Note that the toner filling amount of the developing device was 150 g.

<Example 1>
The first embodiment of the present invention is configured to perform the discharge operation and the discharge control flow (FIG. 4) of the above-described embodiment. In the first embodiment, the discharge control program of the CPU of the image forming apparatus sets the discharge frequency to a predetermined count of the number of printed sheets, and the developing device with a small filling amount has a smaller printing interval than the developing device with a large filling amount. The spout control is turned on.

<Comparative Example 1 Conventional Technology>
In Comparative Example 1, as in the background art described above, toner discharge is sequentially performed so as to achieve a predetermined printing rate at the time of low printing intermittent durability. In this comparative example, the toner is set so as to have a printing rate of 5%. It is controlled to perform the discharge operation at any time.

<Comparative Example 2 Conventional Technology>
In Comparative Example 2, the potential setting during the discharge control is set to the same potential setting as that for normal image formation. The frequency and the amount to be discharged are the same as in the first embodiment. The toner filling amount is 150 g.

<Example 2>
The discharge control flow of Example 2 of this invention is shown in FIG. In the second embodiment, the discharge control program of the CPU of the image forming apparatus discharges the discharge frequency (operating condition) every time the development life held in the nonvolatile memory decreases by a predetermined percentage. (Condition) is changed for each filling amount. That is, when the filling amount is 240 g, the development life decreases every 3% (t16), when the filling amount is the smallest 100 g, every 1% (t14), and in the middle of 150g, Change to discharge every 2% (t15). Here, the developing life is a ratio of the remaining life based on the number of rotations of the developing roller. Other configurations are the same as those in the first embodiment.

<Example 3>
FIG. 6 shows a discharge control flow according to the third embodiment of the present invention. In the third embodiment, the discharge control program of the CPU of the image forming apparatus discharges the discharge frequency (operating condition) every time the remaining amount% of toner held in the nonvolatile memory decreases by a predetermined percentage. (Operating conditions) is changed for each filling amount. That is, when the charging amount is 240 g, the toner remaining amount is reduced by 3% (t19), and when the charging amount is 100 g, the toner remaining amount is 1% (t17). In the case of 150 g, the toner is changed to be discharged every 2% (t18). Other configurations are the same as those in the first embodiment.

<Example 4>
FIG. 7 shows a discharge control flow according to the fourth embodiment of the present invention. In the fourth embodiment, the discharge control program of the CPU of the image forming apparatus changes the discharge amount (operating condition) at the time of discharge for each filling amount as discharge control. That is, in the case of 240 g with the largest filling amount, the ejection amount (operating condition) at the time of ejection is two rotations of the developing roller (D roller) (t22), and in the case of 100 g with the smallest filling amount, 10 rotations of the developing roller. It is controlled to discharge in minutes (t20). Moreover, in the case of 150g in the middle, it controls so that it discharges by the developing roller 5 rounds (t21). Note that the discharge frequency does not depend on the initial filling amount, and discharge is executed when it is counted that 500 sheets have been printed. Other configurations are the same as those in the first embodiment.

<Verification 1 Relationship between residual concentration of coating agent and streaks>
In order to confirm the effect of the discharge property of the coating agent, using the discharge method of the comparative example described above, the low-printing intermittent durability of the developing device was carried out to check whether or not an abnormal image was generated.
[Method]
In an environment of a temperature of 15 ° C. and a humidity of 10%, the image forming apparatus of this example was used to form an image with a low printing rate intermittently on two sheets. The images were checked regularly to confirm the occurrence of abnormal images. The used toner is evaluated for durability using an unused new cyan toner, and the initial filling amount is 150 g. The amount of the coating agent applied to the developing roller is set to 50 mg.
[result]
Table 1-1 in FIG. 8 shows the results of this verification. A in the table indicates a state in which no streak is generated on the image. B in the table is the occurrence of a streak length of less than 2 cm on the image. C in the table has a streak length of 2 cm or more. In any of Examples 1 to 4, it was possible to suppress the occurrence of abnormal images. Details will be described later.

<Verification 2: Verification of discharge performance>
The developing roller was driven to rotate by using the post-endurance developing device used in Verification 1. Whether or not the coating agent (Tospearl) was developed on the developing roller (whether or not the coating agent that had been peeled off once again adhered to the developing roller) was visually confirmed.
[Method]
In an environment where the temperature is 15 ° C. and the humidity is 10%, using the developing device used in the verification 1, a developing device in which the remaining amount of toner after the endurance is 30 g is prepared, and development without toner consumption is performed. Rotate and visually check the coating on the developing roller. It was confirmed whether Tospearl was developed. The potential setting during development driving was set to the potential during discharge operation, and the toner coat state on the developing roller when driving for 1 minute was confirmed.
[result]
Table 1-2 of FIG. 8 shows the results of this verification. A circle in the table indicates that no coating agent is present on the developing roller. In the table, x indicates a case where the coating agent is confirmed on the developing roller. In Examples 1 to 4, the coating agent was not coated on the developing roller, and good results were obtained. Details will be described later.

<Verification 3 Verification of discharge performance>
The same examination as in the verification 2 was performed, and development rotation driving without toner consumption was performed using a new toner. Whether or not the coating agent was coated on the developing roller was visually confirmed.
[Method]
In an environment with a temperature of 15 ° C. and a humidity of 10%, a developing device filled with 30 g of new state toner is prepared, the developing rotation without toner consumption is performed, and the coating state on the developing roller at that time is visually confirmed. It was confirmed whether Tospearl was developed. The potential setting during development driving was set to the potential during discharge operation, and the toner coat state on the developing roller when driving for 1 minute was confirmed. The amount of the coating agent is 50 mg.
[result]
Table 1-3 in FIG. 8 shows the results of this verification. A circle in the table indicates that no coating agent is present on the developing roller. In the table, x indicates a case where the coating agent is confirmed on the developing roller. Even in the new toner, in Examples 1 to 4, the coating agent was not coated on the developing roller, and the result was good. Details will be described later.

<Verification results>
The superiority of Examples 1 to 4 of the present invention over Comparative Example 1 will be described. In the configuration of Comparative Example 1, the result of verification 2 can be considered as the reason why the abnormal image has occurred. That is, the amount of the coating agent was large in the development chamber in the latter half of the durability, and the coating agent was easily developed. There are two possible causes. First, there is a problem in how to discharge the coating agent, and it is highly likely that the coating agent was not actually discharged. Secondly, with the discharge frequency at which the printing rate is constant, the amount of coating agent discharged at a time is limited. For this reason, it is considered that the discharge efficiency is lowered and a streak image is generated.

  The superiority of the present invention over Comparative Example 2 will be described. Since the comparative example 2 does not perform the potential control for efficiently discharging the coating agent, the discharging efficiency of the coating agent is low. For this reason, it is considered that the residual density of the coating agent increased in the latter half of the life of the developing device, and a streak image was generated.

  According to the study by the present inventors, it was found that when the residual concentration of the coating agent is high, the coating agent is developed on the developing roller. In particular, the tendency was remarkable when the toner deteriorated.

  With reference to FIGS. 9 and 10, the results of verifications 2 and 3 are further verified. FIG. 9 is a graph showing the results of verifications 2 and 3 in terms of the residual concentration of the coating agent and the coating point of the developer, and FIG. 10 is an explanatory diagram thereof. The rank on the vertical axis of the graph of FIG. 9 is a ranking of the amount of coating agent developed on the developing roller in five stages. It can be seen that the amount of the coating agent developed on the developing roller decreases as the residual concentration of the coating agent decreases. It can also be seen that even when the residual density is the same, the ease of development of the coating agent changes depending on the difference in the deterioration state of the toner. In particular, the toner after durability deterioration tends to be developed more easily. As shown in FIG. 10, because the chargeability of the toner is lowered, a coating agent having a higher chargeability is more easily coated on the developing roller.

Based on the above study, in Examples 1 to 4, the coating agent is intermittently discharged out of the developing chamber so that the residual concentration of the coating agent that does not generate an abnormal image even with the durability deteriorated toner is less than 0.005%. Therefore, a different discharge control program is prepared for each initial weight, and the discharge control of the coating agent is performed by an optimum method according to the initial weight. In the first to fourth embodiments, even if the discharge control of the developing device with a large toner filling amount is performed by the discharge control in the developing device with a small toner filling amount, the abnormal image due to the coating agent can be suppressed. However, since the coating agent is discharged together with the toner, increasing the discharge frequency of the developing device having a large amount of toner filling is not desirable because the amount of toner that the user can use for image formation is reduced. For this reason, in Examples 1 to 4, the amount of toner that can be used by the user while reducing the occurrence of abnormal images due to the remaining coating agent by changing the operating conditions of the discharge operation for each toner filling amount of the developing device. Is appropriately controlled to maximize the value.

  From the above, in the developing devices of Examples 1 to 4, the result of the lowest coating agent residual concentration after durability was obtained. According to the study by the inventors, the discharge efficiency can be increased by setting the potential to be optimal for discharge according to the electrical characteristics of the coating agent. Further, the developing device with a smaller filling amount can reduce the residual concentration of the coating agent by increasing the discharge frequency and the discharge amount (changing the operating conditions).

  As described above, according to the present embodiment, in a developing device in which a powder different from the developer used for image formation is applied to the developer carrying member in a new state of the developing device, the coating agent is surely moved out of the developing chamber. It is possible to effectively carry out the discharge control. For this reason, even in a situation where the charging characteristics of the toner are lowered due to a decrease in the durability of the developer or deterioration of the developer carrier, the amount of the remaining coating agent is reliably reduced, so that the initial coating is performed. The occurrence of image defects due to the coating agent can be reduced. Accordingly, it is possible to stably form an image throughout the life of the developing device.

  In the above embodiment, an image forming apparatus capable of forming a color image is illustrated, but the image forming apparatus to which the present invention can be applied is not limited to this, and is an image forming apparatus capable of forming a monochrome image. Even if it exists, the same effect can be acquired. Similarly, in this embodiment, the contact development method using a non-magnetic one-component toner is adopted. However, the present invention is not limited to this. For example, the same effect can be obtained even if a jumping development method is adopted.

In the above embodiment, the control is performed to discharge the powder different from the developer depending on the toner filling amount of the developing device. The smaller the toner filling amount of the developing device is, the more the developer discharging amount per unit print number is increased. Stated.
In other words, in the discharge operation for discharging powder different from the developer, the second developer amount, which is larger than the first developer amount, is detected as the discharge amount when the first developer amount is detected. Control is performed so as to be larger than the second discharge amount. This is not particularly limited by means such as increasing the amount to be discharged at one time and the same amount of discharging but increasing the number of times.
As a result, the smaller the initial developer content, the greater the amount of developer discharged per unit printed sheet.
Furthermore, it is not limited to this. For various purposes such as suppressing toner deterioration, stabilizing the photosensitive drum cleaning, or stabilizing the intermediate transfer member, depending on the loading amount of the developing device, the smaller the filling amount, the greater the amount of developer discharged per unit printed sheet. As long as it increases the value, it is possible as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum (image carrier), 4 ... Developing device, 6 ... Cleaning member (cleaning part), 17 ... Developing roller (developer carrier), 17c ... Bias power supply (voltage application part), 18 ... Toner storage chamber (Developer container), 20... Toner supply roller (developer supply member), 20 c... Bias power supply (voltage application unit), 21... Development blade (developer regulating member), 80. Image forming apparatus, 100B ... CPU (voltage application unit, discharge control unit, detection unit)

Claims (13)

An image carrier for carrying a developer image;
A developing device having a developer carrying member carrying the developer, and a regulating member regulating the amount of developer on the developer carrying member;
A detecting unit for detecting the amount of developer contained in the developing device;
A control unit that performs a discharge operation for discharging the developer from the developing device separately from the image forming operation;
The developer carrier carries a coating agent when not in use,
In the discharge operation, the discharge amount when the first developer storage amount is detected is the second discharge amount when the second developer storage amount larger than the first developer storage amount is detected. An image forming apparatus characterized in that the amount is larger than the amount of discharge. A voltage application unit that applies a voltage forming a potential difference between the developer carrier and the supply member to the developer carrier;
The voltage application unit applies a voltage that forms a first potential difference having a magnitude different from that in the image forming operation in the discharge operation to the developer carrying member. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the coating agent is made of a powder having a charging property higher than that of the developer.   In the discharging operation, the voltage application unit is the potential difference having a polarity opposite to the charging polarity of the coating agent charged by the regulating member, and the magnitude of the absolute value of the potential difference of the image forming operation The image forming apparatus according to claim 2, wherein a voltage that forms the first potential difference larger than the second potential difference at the time is applied to the developer carrying member. A counting unit for counting the number of executions of the image forming operation;
The discharging operation is executed when the count number of the counting unit reaches a predetermined number of times, and the control unit reduces the predetermined number of times as the initial developer storage amount decreases, thereby discharging the discharging operation. The image forming apparatus according to claim 1, wherein an execution frequency of the image forming apparatus is increased. A life detecting unit for detecting a ratio of the remaining life of the developer carrier or the image carrier;
The discharge operation is executed every time the remaining life ratio detected by the life detection unit decreases by a predetermined percentage,
The said control part makes the execution frequency of the said discharge operation high by making the said predetermined% small, so that the accommodation amount of an initial developer is small, The any one of Claims 1-4 characterized by the above-mentioned. The image forming apparatus described in 1.   The image forming apparatus according to claim 6, wherein the remaining life is based on a rotation speed of the developer carrier or the image carrier. A remaining amount detecting unit for detecting a ratio of the remaining amount of the developer with respect to the initial amount of the developer;
The discharge operation is executed every time the remaining amount ratio detected by the remaining amount detecting unit decreases by a predetermined percentage,
The said control part makes the execution frequency of the said discharge operation high by making the said predetermined% small, so that the accommodation amount of an initial developer is small, The any one of Claims 1-4 characterized by the above-mentioned. The image forming apparatus described in 1. A counting unit for counting the number of rotations of the developer carrier,
The discharging operation is executed when the count number of the counting unit reaches a predetermined number of times, and the control unit reduces the predetermined number of times as the initial developer storage amount decreases, thereby discharging the discharging operation. The image forming apparatus according to claim 2, wherein the execution frequency of the image forming apparatus is increased.   The image forming apparatus according to claim 1, further comprising a supply member that contacts the developer carrying member and supplies the developer to the developer carrying member.   11. The apparatus according to claim 1, wherein at least the developer carrying member and the regulating member are integrated as a cartridge and configured to be detachable from the apparatus main body of the image forming apparatus. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein an average particle diameter of the coating agent is smaller than an average particle diameter of the developer. A developing device that includes a developer carrying member that carries the developer, and a regulating member that regulates the amount of the developer and applies a charge to the developer carried on the developer carrying member;
A detector that detects the amount of developer contained in the developing device,
An image forming apparatus that performs an ejection operation for moving a developer from the developer carrier to the image carrier, which is different from an image forming operation for forming a developer image on a recording material,
The developer carrier is coated with a coating agent made of powder different from the developer when not in use,
An image, comprising: a control unit that changes the execution frequency so that the smaller the amount of the developer that is detected by the detection unit is, the higher the execution frequency of the discharge operation with respect to the image forming operation is. Forming equipment.