JP6794139B2 - Image forming device - Google Patents

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 "photoreceptor") as an image carrier is uniformly charged, and the charged photosensitive member is charged. By selectively exposing the body, an electrostatic image is formed on the photoconductor. The electrostatic image formed on the photoconductor is visualized as a toner image by the toner of the developing agent. Then, the toner image formed on the photoconductor is transferred to a recording material such as recording paper or a plastic sheet, and heat or pressure is applied to the toner image transferred on the recording material to convert the toner image into a recording material. Image recording is performed by fixing.

Such an image forming apparatus generally requires replenishment of a developer and maintenance of various process means. In order to facilitate the replenishment work of the developer and the maintenance of various process means, a process in which the photoconductor, charging means, developing means, cleaning means, etc. are collectively made into a cartridge in the frame and attached to and detached from the image forming apparatus main body. It has been put into practical use as a cartridge. According to the process cartridge method, it is possible to provide an image forming apparatus having excellent usability.

Conventionally, in a developing apparatus used for an image forming apparatus, a coating agent (lubricating agent) is applied to a developing roller (developing agent carrier) for the purpose of suppressing the blinding of a regulating blade (developing agent regulating member) and reducing the driving torque. The method of doing is widely used. Patent Document 1 uses a powder having the same polarity as toner as a coating agent for a developing roller. In Patent Document 2, as a coating agent, at least the surface of a toner supply roller (developer supply member) is charged with a powder having a charging capacity of 0, or the developer is charged with the same polarity as the developing agent and the absolute value of the charging capacity is the developer. It has been proposed to apply a powder having a charge capacity equal to or less than that of the above. On the other hand, in a conventional image forming apparatus, a technique of periodically discharging a developer for the purpose of suppressing deterioration of the developer is widely known. Patent Document 3 discloses that, for the purpose of suppressing toner deterioration of the developer, the developer is periodically ejected so that the toner consumption for each page is constant.

Japanese Unexamined Patent Publication No. 2-298971 Japanese Unexamined Patent Publication No. 8-227212 Japanese Unexamined Patent Publication No. 2006-23327

When a 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 when the charging characteristics of the toner are lowered due to the deterioration of the durability of the developing agent and the durability of the developing roller and the developing blade. At the time of image formation, it may move to the recording material together with the toner image. The coating agent adhering to the recording material in this way may appear as a streak image on the image or as a streak-like fog image on a white background on the paper. Therefore, it is desirable that the coating agent initially applied to the developing roller is promptly discharged to the outside of the developing room.

However, with the conventional discharge method and discharge frequency as in Patent Document 3, the coating agent could not be completely discharged and may stay in the developing room. When image formation is performed with the coating agent remaining in the developing chamber in this way, the coating agent is used as a recording material together with the toner image in a situation where the charging characteristics of the toner deteriorate due to deterioration of the durability of the developing agent and deterioration of the developing roller. It sometimes moved. In this case as well, there is a concern that abnormal images such as streaks and fog 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, the image forming apparatus of the present invention
In an image forming apparatus capable of performing an image forming operation of forming an image on a recording material,
An image carrier for supporting the developer image and
A developing unit having a developer carrying member for carrying a developer,
A detection unit that detects the amount of developer contained in the developing device, and
A said image forming operation, the a discharging operation for discharging the developer from the developing device, and a control unit that performs, for,
The developer carrier carries a coating agent when not in use,
When the detection unit detects that the capacity of the developer when not in use is the first capacity in the discharge operation, the control unit stores the developer in the unused state. There and controlling the first greater than the storage capacity second than the amount discharged when it is detected that a yield capacity multi Kunar so.
Further, in order to achieve the above object, the image forming apparatus of the present invention is used.
In an image forming apparatus capable of performing an image forming operation of forming an image on a recording material,
An image carrier for supporting the developer image and
A developing device comprising a developer carrying member for carrying a developer,
A detection unit for detecting the amount of the developer contained in the developing apparatus is provided.
The image forming operation and a different operation, an image forming apparatus for performing a discharging operation is moved to said image bearing member a developer from said developer carrying member,
When not in use, the developer carrier is coated with a coating agent made of a powder different from the developer.
A control unit for changing the execution frequency is provided so that the smaller the amount of the developing agent contained in the unused state detected by the detection unit, the higher the execution frequency of the discharge operation with respect to the image forming operation. It is characterized by.

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

Schematic cross-sectional view of the image forming apparatus according to the embodiment Schematic cross-sectional view of the process cartridge in the examples Schematic cross-sectional view of the developing apparatus in the examples Flow diagram of the discharge operation in the first embodiment Flow chart of discharge operation in Example 2 Flow chart of discharge operation in Example 3 Flow chart of discharge operation in Example 4 A table showing the results of comparative verification in the examples Graph showing comparative verification results in Examples Diagram for explaining the effect of the embodiment

Hereinafter, embodiments for carrying out the present invention will be described in detail exemplarily based on examples with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed depending on 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)
The electrophotographic image forming apparatus according to the embodiment of the present invention will be described. Here, the electrophotographic image forming apparatus (hereinafter, also simply referred to as “image forming apparatus”) uses an electrophotographic image forming method and uses a developing agent (hereinafter, also referred to as “toner”) as a recording material to form an image. It is what forms. Examples of the image forming apparatus include a copier, a printer (laser beam printer, LED printer, etc.), a facsimile apparatus, a word processor, and a multifunction printer (multifunction printer) thereof.

Further, in the present specification, terms indicating directions such as up, down, vertical, and horizontal with respect to the configuration and operation of a developing unit (or developing apparatus) or a process cartridge are usually used unless otherwise specified. Represents the direction when viewed in the state. That is, the normal usage state of the developing unit (or developing device) or the process cartridge is a state in which the developing unit (or the developing device) or the process cartridge is properly mounted on the properly arranged image forming apparatus main body and can be used for the image forming operation.

[Image forming device]
FIG. 1 is a schematic cross-sectional view showing the overall configuration of the 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 in-line 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 device connected to the image forming apparatus main body 100A or a host device such as a pannal computer communicably connected to the image forming apparatus main body 100A.

The image forming apparatus 100 uses the first, second, and third image forming units for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K), respectively. , Has a fourth image forming unit SY, SM, SC, SK. In this embodiment, the first to fourth image forming portions SY, SM, SC, and SK are arranged in a row in a direction intersecting the vertical direction. In this 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 the formed images are different. Therefore, in the following, if no particular distinction is required, the subscripts Y, M, C, and K given to the symbols to indicate that the elements are provided for any of the colors are omitted and collectively. explain. Of course, depending on the configuration, an image forming apparatus provided with image forming portions having different sizes and shapes may be used.

The image forming apparatus 100 has four drum-type electrophotographic photosensitive members, that is, a photosensitive drum 1 arranged side by side in a direction intersecting the vertical direction as a plurality of image carriers. The photosensitive drum 1 is rotationally driven in the direction of arrow A (clockwise) by a drive means (drive source) (not shown). Around the photosensitive drum 1, a charging roller 2 as a charging means for uniformly charging the surface of the photosensitive drum 1, and an electrostatic image (electrostatic latent image) on the photosensitive drum 1 by irradiating a laser based on image information. A scanner unit (exposure device) 3 is arranged as an exposure means for forming the above. Further, around the photosensitive drum 1, a developing unit (developing device) 4 as a developing means for developing an 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 as a cleaning means is arranged. Further, an intermediate transfer belt 5 as an intermediate transfer body for transferring the toner image (developer image) on the photosensitive drum 1 to the recording material 12 is arranged so as to face the four photosensitive drums 1.

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

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, integrally made into a cartridge, and the process cartridge is formed. 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 on the image forming apparatus main body 100A. In this embodiment, the process cartridges 7 for each color all have the same shape, and the process cartridges 7 for each color contain yellow (Y), magenta (M), cyan (C), and blanks, respectively. The toner of each color of K) is stored.

The intermediate transfer belt 5 formed of the endless belt as the intermediate transfer body abuts on all the photosensitive drums 1 and circulates (rotates) in the direction of arrow B (counterclockwise) in the drawing. The intermediate transfer belt 5 is hung on the drive roller 51, the secondary transfer opposed roller 52, and the 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 as primary transfer means are arranged side by side so as to face each photosensitive drum 1. The primary transfer roller 8 presses the intermediate transfer belt 5 toward the photosensitive drum 1 to form a primary transfer portion N1 in which the intermediate transfer belt 5 and the photosensitive drum 1 come into contact with each other. Then, 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 supply (high voltage power supply) as a primary transfer bias applying means (not shown). As a result, the toner image on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 5.

Further, a secondary transfer roller 9 as a secondary transfer means is arranged at a position facing the secondary transfer facing 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 opposed roller 52 via the intermediate transfer belt 5 to form a secondary transfer portion N2 in which the intermediate transfer belt 5 and the secondary transfer roller 9 come into contact with each other. Then, 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 supply (high pressure power supply) as a secondary transfer bias applying means (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 the laser beam 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 forming a full-color image, the above-mentioned processes are sequentially performed in the first to fourth image forming units SY, SM, SC, and SK, and the toner images of each color are superimposed on the intermediate transfer belt 5 to be primary. Transferred.

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

Further, the primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer step is removed and recovered by the cleaning member 6. Further, the secondary transfer residual toner remaining on the intermediate transfer belt 5 after the secondary transfer step is cleaned by the intermediate transfer belt cleaning device 11. It should be noted that the image forming apparatus 100 can also form a monochromatic or multicolored image using only one desired image forming portion or only some (but not all) image forming portions. It has become like.

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

The photoconductor unit 13 has a cleaning frame body 14 as a frame body that supports various elements in the photoconductor unit 13. A 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 arrow A (clockwise) according to the image forming operation by transmitting the driving force of a drive motor as a drive means (drive source) (not shown) to the photoconductor unit 13. To. In this embodiment, the photosensitive drum 1 which is the center of the image forming process is an organic photosensitive drum 1 in which an undercoat layer, a carrier generation layer, and a carrier transfer layer, which are functional films, are sequentially coated on the outer peripheral surface of an aluminum cylinder. I am using it.

A cleaning member 6 and a charging roller 2 are arranged on the photoconductor unit 13 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 is dropped and housed in the cleaning frame 14 (cleaning unit).

The charging roller 2, which is a charging means, rotates drivenly by bringing the roller portion of the conductive rubber into pressure contact with the photosensitive drum 1. As a charging process, a predetermined DC voltage is applied to the core metal of the charging roller 2 to the photosensitive drum 1, whereby a uniform dark potential (Vd) is formed on the surface of the photosensitive drum 1. To. The spot pattern of the laser beam emitted in response 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 by the carriers from the carrier generation layer. It disappears and the potential drops. As a result, an electrostatic latent image having a predetermined bright area potential (Vl) in the exposed area and a predetermined dark area potential (Vd) in the unexposed area is formed on the photosensitive drum 1. In this example, Vd = -520V and Vl = -100V.

In the developing unit 4, a developing roller 17 as a developing agent carrier for supporting the developing agent (toner) 80 and a toner supply roller 20 as a developing agent supplying member for supplying toner to the developing roller 17 are arranged. Has a room. Further, the developing unit 4 is arranged below the toner supply roller 20 in the direction of gravity, and is communicated with the developing chamber by the developing opening 33, which is a developing agent storage chamber for storing the toner 80, that is, a toner storing chamber 18 (developing agent). It has a containment unit). Further, the toner supply roller 20 is rotating in contact with the developing roller 17 with the nip portion N.

In the toner storage chamber 18, the toner stored in the toner storage chamber 18 is agitated, and the toner is conveyed to the upper part of the toner supply roller 20 toward the region indicated by V in the direction of arrow G in the drawing. The stirring and transporting member 22 of the above is provided.

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

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

The toner supply roller 20 is arranged so as to form a predetermined contact portion (nip portion) N on the peripheral surface of the developing roller 17 at the facing portion, and rotates in the direction of arrow E (clockwise) in the drawing. The toner supply roller 20 is an elastic sponge roller having a foam layer formed on the outer periphery of the conductive core metal. 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. 2, the toner supply roller 20 has a recessed amount ΔE that is made concave by the developing roller 17. The contact portion N rotates in the same direction with a peripheral speed difference, and by this operation, the toner supply roller 20 supplies toner to the developing roller 17. At that time, the amount of toner supplied to the developing roller 17 can be adjusted by adjusting the potential difference between the toner supply 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 driven at 100 rpm, and a DC bias is applied so that the potential of the developing roller 17 becomes V = + 50V with respect to the potential of the toner supply roller 20. There is.

Both the developing roller 17 and the toner supply roller 20 in this embodiment have an outer diameter of 15 mm, and the amount of penetration of the toner supply roller 20 into the developing roller 17, that is, the toner supply roller 20 is made concave by the developing 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 heights are 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 urethane foam layer as a foam layer composed of a core metal electrode 20a having an outer diameter of φ5 (mm), which is a conductive support, and an open cell (continuous bubble) in which bubbles are connected to each other around the core electrode 20a. 20b is provided and rotates in the direction of E in the figure. By using urethane on the surface layer as an open cell, a large amount of toner can enter the inside of the toner supply roller 20. 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 the amount of penetration described later is 1.5 mm. By rotating the aluminum sleeve, the toner supply roller 2 is driven to rotate with respect to the aluminum sleeve at 30 rpm. Next, a DC voltage of −50 V is applied to the aluminum sleeve. At that time, a resistor of 10 kΩ is provided on the ground side, the current is calculated by measuring the voltage across the resistor, 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 refers to the average diameter of foam cells having an arbitrary cross section. First, the area of the foam cell that is the maximum is measured from the enlarged image of the arbitrary cross section, and the diameter equivalent to a perfect circle is converted from this area to obtain the maximum cell diameter. To get. Then, after removing the foamed cells that are 1/2 or less of the maximum cell diameter as noise, it refers to the average value of the individual cell diameters similarly converted from the remaining individual cell areas.

Subsequently, the toner circulation in the developing chamber when the toner supply roller 20 is rotating in the direction of the arrow E in the drawing will be described. First, the toner contained in the toner accommodating portion 18 is flipped up by the toner conveying member 22, and most of the toner is conveyed to the upper part of the supply roller 20. The toner conveyed to the supply roller 20 stays on the surface and inside of the supply roller 20. Then, the supply roller 20 is conveyed to just before the nip with the developing roller 17 by rotating in the direction of arrow E in the drawing. Then, the portion of the supply roller 20 to which the toner is conveyed is deformed immediately before the nip with the developing roller 17, and the deformation causes the toner remaining on the surface and inside to be discharged. The discharged toner is stored in the space above the developing roller 17 and the supply roller 20 (hereinafter, referred to as “temporary toner storage unit V”).

A part of the toner stored in the temporary toner storage portion V rushes into 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 charged by rubbing between the developing roller 17 and the supply roller 20. After passing through the nip portion N, the charged toner is electrostatically adsorbed on the developing roller 17 according to its own charge amount. Due to the effect, 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, so that a toner coat having a desired layer thickness is formed on the developing roller 17. Further, the regulated toner falls due to gravity and returns to the toner accommodating portion 18.

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

[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 is intended to protect the developing roller 17 from the time of manufacture to the start of use and to function 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. Approximately 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 in the coating agent 22. Its average particle size is 2 μm. The coating agent used in this embodiment has a characteristic of having a higher charge than the toner used for development. Specifically, in a greenhouse environment of 23 ° C. and 40%, the average charge per unit mass of toner was about 50 μC / g, while the average charge per unit mass of tospar 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 having a charging characteristic lower than that of the coating agent as described above. Further, the average particle size of the developer is preferably larger than that of the coating agent.

In this embodiment, tospearl having a particle size of 2 μm is used, but the present invention is not limited to this, and any one that functions as a lubricant without turning over the developing blade 21 can be used as appropriate. Specifically, examples of the material and particle size used for the coating agent include the following in consideration of the electrical characteristics of 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, etc. into these resins, they are pulverized by a known pulverization method to form mother particles. Further, an external additive may be added. Further, regarding the particle size, a combination of 0.8 μm to 10 μm can be appropriately used.

[Developer filling amount]
The amount of the developing agent filled in the developing apparatus 4 in this embodiment will be described in detail with reference to FIGS. 3A to 3C. In the developing apparatus 4 of this embodiment, there are three levels in which the toner filling amount is different. That is, in the image forming apparatus according to the present embodiment, three types of developing apparatus 4 having different toner filling amounts in the toner chamber in the unused state (initial) are configured to be detachably attached to the apparatus main body 100A. 3 (a) to 3 (c) are schematic cross-sectional views of the developing apparatus 4 in this embodiment, FIG. 3 (a) shows a type in which the initial filling amount of the developing agent is 240 g, and FIG. 3 (b) shows. The 150 g type and FIG. 3 (c) show the 100 g type developing apparatus 4, respectively. The user can appropriately select which type of developing apparatus 4 is to be attached to the apparatus main body 100A according to the frequency of use and cost, and provides a degree of freedom.

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

In this embodiment, the information regarding the filling amount of the toner is based on the filling amount held in the non-volatile ROM, but the information for determining the filling amount is not limited to this. For example, any information that can determine the difference in toner filling amount, 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, and the life rotation speed of the photosensitive drum, can be appropriately substituted. is there. In this embodiment, the information regarding the filling amount of the developing agent is used, but the information regarding the amount of the developing agent contained in the unused developing apparatus (new developing apparatus) may be held in the non-volatile memory 200.

[Filling amount detecting means]
A CPU 100B (FIG. 2) is arranged in the image forming apparatus as a central processing apparatus. The CPU is a control unit that reads various adjustment values from the non-volatile memory attached to the developing device and controls the image forming device. Information on the initial filling amount of the developing device is also detected by the CPU from the non-volatile memory, and a predetermined discharge control program is selected and controlled for each filling amount. Further, in this embodiment, the toner filling amount of the developing device is determined based on the information of the non-volatile memory, but 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, ribs, etc.) of the developing device for each toner filling amount and detecting the difference in the container shape with the image forming apparatus.

[Discharge control]
Next, the control of discharging the coating agent in this embodiment will be described in detail. Most of the coating agent applied to the developing roller 17 at the beginning of use of the developing apparatus is collected on the surface of the toner supply roller 20 and inside the toner supply roller 20 by rotary rubbing between the developing roller 17 and the toner supply roller 20. Toner.

Further, since the coating agent of this embodiment has a feature of having a higher charge than the toner, it is necessary to control the discharge with a potential setting different from that at the time of normal image formation. That is, the potential difference is opposite to the charging polarity of the coating agent charged by the developing blade 21, and the magnitude of the absolute value forms a potential difference larger than the potential difference in the image forming operation. Specifically, the toner supply roller 20 is DC from the bias power supply 20c, and the developing roller 17 is DC from the bias power supply 17c so that the potential of the developing roller 17 is V = + 300V with respect to the potential of the toner supply roller 20. Bias is applied. The CPU 100B that controls the bias application of the bias power supplies 20c and 17c and the toner supply rollers 20 and the development roller 17 corresponds 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 on the positive side. By setting the potential based on the electrical characteristics of the coating agent in this way, 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 in the developing roller 17 moves to the photosensitive drum 1 together with the toner by performing a solid black image forming operation for one round of the developing roller 17 together with the toner, and is collected in the cleaner container. Toner. By this work, the amount of the coating agent remaining in the developing chamber can be surely reduced. In addition, this discharge control also serves as a lubricant for the cleaning member 6. At this time, since the intermediate transfer belt 5 is separated from the photosensitive drum 1, all the toner transferred from the developing device 4 to the photosensitive drum 1 is collected by the cleaning member 6.

In this embodiment, since a coating agent having a higher charging characteristic than the toner was used, the potential was set as described above, but the potential is not limited to this, and the coating agent can be efficiently discharged according to the electrical characteristics of the coating agent. It is also possible to set the potential to be performed.

[Toner discharge control flow]
The toner discharge control in the first embodiment will be described with reference to FIG. FIG. 4 is a diagram showing a flowchart of the discharge operation in the first embodiment. In this embodiment, as described below, the CPU of the image forming apparatus sets the operating conditions of the ejection operation to (4) t4, (12) t11, and (15) t13 according to the initial filling amount information in the non-volatile memory. Switch to three. In particular, the discharge operation control program is characterized in that the smaller the initial filling amount, the more aggressively the coating agent is discharged. In this embodiment, the frequency of ejection is set to a predetermined count of the number of printed sheets, and the developing apparatus having a small filling amount can control the ejection with a smaller number of printing counts than the developing apparatus having a large filling amount. There is.
In this embodiment, the CPU 100B corresponds to the accommodation amount detection unit for detecting the initial toner filling amount (accommodation amount) of the developer in the present invention. Further, in the present embodiment, the CPU 100B also serves as a discharge control unit for changing the execution frequency (operating condition) of the discharge operation, a count unit for counting the number of times the image formation operation is executed, a life detection unit, a remaining amount detection unit, and the like in the present invention. ..

(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) The detection result of 100 g is sent to the toner discharge control means (t3).
(4) The detection means selects every 100 sheets of discharge frequency at 100 g (t4).
(5) Normal image formation is performed (t5).
(6) A counter is added each time an image is formed (t6).
(7) After a certain number of sheets have elapsed, the counter count reaches a predetermined count number (t7).
(8) The discharge control means detects the arrival at the counter and performs a discharge operation (t8).
(9) After the discharge operation is completed, the counter is returned to 0 (t9).
After (10), it returns to (t5) and loops from (t5) to (t9).
(11) In (t2), the detection result of 150 g is sent to the toner discharge control means (t10).
(12) The detection means selects a discharge frequency of every 300 sheets at 150 g (t11).
After (13), the loop is performed from (t5) to (t9) as in the case of 100 g.
(14) In (t2), the detection result of 240 g is sent to the toner discharge control means (t12).
(15) The detection means selects every 600 sheets to be discharged at 240 g (t13).
After (16), the loop is performed from (t5) to (t9) as in the case of 100 g.

<Comparison verification>
In order to verify the effect of the discharge performance of the coating agent, the configuration of the example of the present invention was verified using this example and the following comparative example. The toner filling amount of the developing device was 150 g.

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

<Comparative Example 1 Conventional Technology>
In Comparative Example 1, the toner is sequentially discharged so as to have a predetermined printing rate at the time of low printing intermittent durability as in the background technique described above. In this Comparative Example, the toner is discharged 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 at the time of executing the discharge control is the same potential setting as that for normal image formation. The frequency and the amount of exhalation are the same as in Example 1. The filling amount of toner is 150 g.

<Example 2>
The discharge control flow of Example 2 of the present 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 non-volatile memory decreases by a predetermined percentage, and the frequency (operation). The condition) is changed for each filling amount. That is, in the case of 240 g having the largest filling amount, the development life is reduced every 3% (t16), in the case of 100 g having the smallest filling amount, every 1% (t14), and in the case of 150 g in between. Change to spit out every 2% (t15). Here, the development life is a ratio of the remaining life based on the rotation speed of the developing roller. Other configurations are the same as in the first embodiment.

<Example 3>
The discharge control flow of Example 3 of the present invention is shown in FIG. In the third embodiment, the discharge control program of the CPU of the image forming apparatus discharges the frequency (operating condition) of the discharge every time the remaining amount of toner held in the non-volatile memory decreases by a predetermined percentage. (Operating conditions) are changed for each filling amount. That is, in the case of 240 g having the largest filling amount, the toner remaining amount decreases every 3% (t19), and in the case of 100 g having the smallest filling amount, the toner remaining amount decreases every 1% (t17). In the case of 150 g, change so that the toner is discharged every 2% of the remaining amount of toner (t18). Other configurations are the same as in the first embodiment.

<Example 4>
The discharge control flow of Example 4 of the present invention is shown in FIG. 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 as the discharge control for each filling amount. That is, in the case of 240 g having the largest filling amount, the discharge amount (operating condition) at the time of discharging is two laps of the developing roller (D roller) (t22), and in the case of 100 g having the smallest filling amount, 10 laps of the developing roller. It is controlled to exhale in minutes (t20). Further, in the case of 150 g in the middle of them, it is controlled to be discharged by 5 laps (t21) of the developing roller. The frequency of ejection is not related to the initial filling amount, and the ejection is executed when it is counted that 500 sheets have been printed. Other configurations are the same as 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, the low printing intermittent durability of the developing device was carried out by using the discharge method of the above-mentioned comparative example, and the presence or absence of abnormal images was confirmed.
[Method]
In an environment of a temperature of 15 ° C. and a humidity of 10%, an image forming apparatus of this example was used to form an image having a low printing rate intermittently on two sheets. The images were checked regularly to confirm the occurrence of abnormal images. The durability of the used toner is evaluated using cyan toner in a new unused state, and the initial filling amount is 150 g. Further, the amount of the coating agent applied to the developing roller is adjusted to 50 mg.
[result]
The verification results are shown in Table 1-1 of FIG. A in the table is a state in which no streaks are generated on the image. B in the table is an occurrence in which the streak length on the image is less than 2 cm. C in the table has a streak length of 2 cm or more. In any of Examples 1 to 4, the result was that the occurrence of abnormal images could be suppressed. Details will be described later.

<Verification 2 Verification of exhalation property>
The development roller was rotationally driven using the endurance developing apparatus used in Verification 1. It was visually confirmed whether or not the coating agent (Tospearl) was developed on the developing roller (whether or not the once peeled coating agent was adhered to the developing roller again).
[Method]
Using the developing device used in Verification 1 in an environment with a temperature of 15 ° C and a humidity of 10%, a developing device with a uniform remaining amount of toner after durability of 30 g was prepared, and development without toner consumption was performed. Rotate and visually check the coating condition on the developing roller at that time. It was confirmed whether tospearl was developed. The potential setting during the development drive was set to the potential during the discharge operation, and the toner coating state on the developing roller when the drive was applied for 1 minute was confirmed.
[result]
The results of this verification are shown in Table 1-2 of FIG. ◯ in the table indicates that there is no coating agent on the developing roller. X in the table is the 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 exhalation property>
The same examination as in Verification 2 was carried out using a new toner and a development rotation drive without toner consumption. It was visually confirmed whether or not the coating agent was coated on the developing roller.
[Method]
In an environment of temperature 15 ° C. and humidity 10%, prepare a developing device filled with 30 g of new toner, perform development rotation without toner consumption, and visually check the coating state on the developing roller at that time. It was confirmed whether the toner was developed. The potential setting during the development drive was set to the potential during the discharge operation, and the toner coating state on the developing roller when the drive was applied for 1 minute was confirmed. The amount of the coating agent is 50 mg.
[result]
The results of this verification are shown in Table 1-3 of FIG. ◯ in the table indicates that there is no coating agent on the developing roller. X in the table is the case where the coating agent is confirmed on the developing roller. Even in the toner in a new state, 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 result>
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 developing chamber in the latter half of the durability, and the coating agent was easily developed. There are two possible factors. First, there is a problem with how to spit out the coating agent, and it is highly possible that the coating agent was not actually discharged. Secondly, the amount of the coating agent discharged at one time is limited at the discharge frequency such that the printing rate is constant. Therefore, it is considered that the spitting efficiency is lowered and a streak image is generated.

The superiority of the present invention over Comparative Example 2 will be described. In Comparative Example 2, since the potential control for efficiently discharging the coating agent is not performed, the discharging efficiency of the coating agent is low. Therefore, it is considered that the residual concentration of the coating agent becomes high and a streak image is generated in the latter half of the life of the developing apparatus.

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

The results of verifications 2 and 3 will be further verified with reference to FIGS. 9 and 10. FIG. 9 is a graph of the results of verifications 2 and 3 from the viewpoint of the residual concentration of the coating agent and the coating of the developer, and FIG. 10 is an explanatory diagram thereof. The rank on the vertical axis of the graph of FIG. 9 ranks the amount of the 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. Further, it can be seen that even if the residual concentration is the same, the ease of developing the coating agent changes depending on the difference in the deterioration state of the toner. In particular, the coating agent tends to be developed more easily in the toner after the durability is deteriorated. This is because, as shown in FIG. 10, the chargeability of the toner is lowered, so that the coating agent having a high chargeability is more likely to be coated on the developing roller.

Based on the above examination, in Examples 1 to 4, the coating agent is intermittently discharged to the outside of the developing room so that the residual coating concentration of the coating agent, which does not generate an abnormal image even with the durable 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 the optimum method according to the initial weight. Further, in Examples 1 to 4, even if the ejection control of the developing apparatus having a large toner filling amount is performed by the ejection control in the developing apparatus having a small toner filling amount, the abnormal image of the coating agent factor can be suppressed. However, since the coating agent is discharged together with the toner, increasing the discharge frequency of the developing apparatus having a large amount of toner filling reduces the amount of toner that the user can use for image formation, which is not desirable. Therefore, 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 residual coating agent by changing the operating conditions of the discharge operation for each toner filling amount of the developing device. It is controlled appropriately so that

From the above, in the developing apparatus of Examples 1 to 4, the result that the residual concentration of the coating agent after durability was the lowest was obtained. According to the study by the inventors, the discharge efficiency can be improved by setting the optimum potential for discharge according to the electrical characteristics of the coating agent. Further, it is possible to reduce the residual concentration of the coating agent by increasing the discharge frequency and the discharge amount (changing the operating conditions) as the developing device has a smaller filling amount.

As described above, according to the present embodiment, in the new state of the developing apparatus, in the developing apparatus in which a powder different from the developing agent used for image formation is applied to the developing agent carrier, the coating agent is surely moved out of the developing room. It is possible to effectively carry out control of spitting out. For this reason, even in a situation where the charging characteristics of the toner are deteriorated due to a decrease in the durability of the developer or deterioration of the developer carrier, the amount of the residual coating agent is surely reduced, so that the coating agent is applied at the initial stage. It is possible to reduce the occurrence of image defects caused by the coating agent. Therefore, stable image formation can be performed 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 an image forming apparatus capable of forming a monochrome image is used. Even if there is, the same effect can be obtained. Similarly, in this embodiment, a contact development method using a non-magnetic one-component toner is adopted, but the present invention is not limited to this, and for example, the same effect can be obtained by adopting a jumping development method.

In the above embodiment, the control is to discharge a powder different from the developer depending on the toner filling amount of the developing device, but the smaller the toner filling amount of the developing device is, the more the developing agent is discharged per unit number of prints. Stated.
In other words, in the discharge operation of discharging powder different from the developer, the amount of the second developer when the amount of the first developer is detected is larger than the amount of the first developer. It is controlled so that it is larger than the second discharge amount at the time. This is not particularly limited in terms of means such as increasing the amount of discharge at one time and increasing the number of times of discharging the same amount.
As a result, the smaller the initial content of the developer, the more the amount of the developer discharged per unit number of printed sheets may be increased.
Moreover, it is not limited to this. For various purposes such as suppressing deterioration of toner, stabilizing the cleanability of the photosensitive drum, or stabilizing the cleaning of the intermediate transfer body, depending on the filling amount of the developing device, the smaller the filling amount, the more the developer discharge amount per unit number of prints. It is possible as long as it increases.

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

Claims (12)

In an image forming apparatus capable of performing an image forming operation of forming an image on a recording material,
An image carrier for supporting the developer image and
A developing unit having a developer carrying member for carrying a developer,
A detection unit that detects the amount of developer contained in the developing device, and
A said image forming operation, the a discharging operation for discharging the developer from the developing device, and a control unit that performs, for,
The developer carrier carries a coating agent when not in use,
When the detection unit detects that the capacity of the developer when not in use is the first capacity in the discharge operation, the control unit stores the developer when it is not in use. There the image forming apparatus characterized by controlling the first greater than the storage capacity second than the amount discharged when it is detected that a yield capacity multi Kunar so. A supply member that comes into contact with the developer carrier and supplies the developer to the developer carrier.
Anda voltage applying unit for applying a voltage to a potential difference to said developer carrying member between the supply member and the developer carrying member,
The voltage applying unit, wherein in the discharging operation, a voltage for forming a first potential difference different sizes from the image forming operation, to claim 1, characterized in that applied to the developer carrying member Image forming device. The coating agent is, an image forming apparatus according to claim 1 or 2, characterized in that it consists of high powder electrification characteristics than the developer. It has a regulating member that regulates the amount of the developer on the developer carrier.
In the discharge operation, the voltage applying portion has 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 is the image forming. voltage forming the first potential difference greater than the second potential difference definitive in operation, the image forming apparatus according to claim 2, characterized in that applied to the developer carrying member. A counting unit for counting the number of executions of the image forming operation is provided.
The discharge operation is executed when the count number of the counting unit reaches a predetermined number of times.
The control unit according to claim 1 to 4, wherein the smaller the amount of the developer when not in use , the smaller the predetermined number of times, so that the execution frequency of the discharge operation is increased. The image forming apparatus according to any one item. A life detection unit for detecting the ratio of the remaining life of the developer carrier or the image carrier is provided.
The discharge operation is executed every time the ratio of the remaining life detected by the life detection unit decreases by a predetermined percentage.
The control unit according to claim 1 to 4, wherein the smaller the amount of the developing agent contained when not in use , the smaller the predetermined%, thereby increasing the execution frequency of the ejection operation. The image forming apparatus according to any one item. The image forming apparatus according to claim 6, wherein the remaining life is based on the rotation speed of the developer carrier or the rotation speed of the image carrier. It includes a remaining amount detecting unit for detecting a ratio of the remaining amount of the developing agent to the storage amount of the developer at the time of the unused
The discharge operation is executed every time the ratio of the remaining amount detected by the remaining amount detecting unit decreases by a predetermined percentage.
The control unit according to claim 1 to 4, wherein the smaller the amount of the developing agent contained when not in use , the smaller the predetermined%, thereby increasing the execution frequency of the ejection operation. The image forming apparatus according to any one item. A counting unit for counting the number of rotations of the developer carrier is provided.
The discharge operation is executed when the count number of the counting unit reaches a predetermined number of times.
According to claim 2 or 4, the control unit increases the frequency of execution of the discharge operation by reducing the predetermined number of times as the amount of the developing agent contained when not in use is smaller. The image forming apparatus described. The cartridge having a pre-Symbol developer carrying member, the image forming apparatus according to any one of claims 1 to 9, characterized in that it is detachably mountable to the apparatus main body of the image forming apparatus. The average particle size of the coating agent, the image forming apparatus according to any one of claims 1 to 1 0, characterized in that the smaller than the average particle size of the developer. In an image forming apparatus capable of performing an image forming operation of forming an image on a recording material,
An image carrier for supporting the developer image and
A developing device comprising a developer carrying member for carrying a developer,
A detection unit for detecting the amount of the developer contained in the developing apparatus is provided.
The image forming operation and a different operation, an image forming apparatus for performing a discharging operation is moved to said image bearing member a developer from said developer carrying member,
When not in use, the developer carrier is coated with a coating agent made of a powder different from the developer.
A control unit for changing the execution frequency is provided so that the smaller the amount of the developer detected by the detection unit when it is not used, the higher the execution frequency of the discharge operation with respect to the image forming operation. An image forming apparatus characterized by.