JP2007249163A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can sufficiently use a fresh developer by preventing the newly supplied developer from being discharged without being used. <P>SOLUTION: The image forming apparatus has a developer transport roller 9 transporting a developer to a developing roller by a trickle development system of an electrophotographic system, and a developer transporting means comprising agitating and transporting screws 10A and 10B. Then the developer transporting means discharges a developer after the supplied developer reaches a reference amount in the agitating and transporting screws 10A and 10B. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a technique for supplying and discharging a developer.

  In an electrophotographic image forming apparatus, a latent image is formed on a uniformly charged image forming body by exposure, the latent image is developed into a toner image, and then the toner image is transferred to a transfer material such as recording paper. To do. Then, when the transfer material carrying the toner image passes through the fixing device, the toner is fixed on the transfer material.

  When developing a latent image, a two-component developer composed of a toner and a carrier having excellent developability is often used. The toner and the carrier are agitated in the developing device, the toner is electrostatically attached to the outer surface of the carrier, and the toner to which the toner is conveyed to the developing area and applied with the developing bias is separated from the carrier and becomes a latent image portion of the image forming body. Adhere electrostatically. Since toner is consumed by development in the developing device, toner concentration detecting means for detecting the amount of toner in the developer using inductance or the like is provided in the developing device. When the toner falls below a predetermined ratio, the toner is replenished into the developing device from a toner supply unit such as a toner hopper.

  Conventionally, the toner in each developing device is replenished at least by the amount of consumed toner with new toner, but the carrier is used continuously. When this carrier is used for a long period of time, a minute toner of less than 1 μm adheres to the outer periphery of each carrier, and this causes the development performance to gradually deteriorate so that a good toner image cannot be obtained. become. For this reason, when a predetermined number of images have been formed, each developing device arranged close to the periphery of the image forming body is removed, the internal developer is replaced, and a new carrier is replaced. Had to be done.

  In this way, the toner to be replenished and a new carrier are added and replenished after a certain period of time, and the replacement of the developer due to service work is gradually omitted by gradually replacing the carrier with deteriorated development performance with a new carrier, That is, a method called trickle development has been proposed (see, for example, Patent Document 1).

  Similarly, by adding carrier particles into the housing chamber at a rate that is a function of the aging rate of the carrier particles and the required charging capacity of the toner particles in the housing chamber, the service life of the developer in the housing chamber can be reduced. An apparatus that guarantees at least equal to the service life has been proposed (see, for example, Patent Document 2).

  In order to stabilize the image density, an apparatus having a function of increasing the amount of developer in the container has been proposed for the purpose of making the amount of toner on the developing roller constant (for example, patents). Reference 3). In the invention disclosed in the document, the developer does not overflow before the developer is full, but when the developer is full, the developer overflows and a newly supplied developer is supplied. Are also discharged.

Also, an apparatus having a developer supply mode and a discharge mode has been proposed for the problem of discharging dust only before and after the operation of the machine (see, for example, Patent Document 4). However, the supply mode and the discharge mode only have a function of discharging the developer at a stroke in order to discharge the dust, and the problem of discharging a new agent is not addressed.
JP-A-2-21591 JP-A-7-111598 JP 11-167269 A JP 2001-209243 A

  However, in the conventional technologies described so far, a new carrier is added at a fixed ratio together with the toner to be replenished, and a carrier whose service performance has deteriorated is gradually replaced with a new carrier. However, the newly replenished developer instead of the deteriorated developer overflows from the discharge port and is discharged and wastes new agent. The problem that it ends up was left.

  The present invention has been made in consideration of the above-described circumstances, and prevents the newly replenished developer from being discharged without being used, thereby making it possible to fully utilize the new developer. The purpose is to provide.

  In order to solve the above problem, only the developer or carrier is replenished without discharging the developer up to a certain amount, the agent is circulated in the developing machine, and the agent is only recognized when the amount exceeds a certain amount. This prevents the new agent from leaving the outlet without being used.

  That is, the invention according to claim 1 is an image forming apparatus having a developer conveying means comprising a developer conveying roller and an agitating / conveying screw for conveying the developer to the developing roller by an electrophotographic trickle developing method. The developer is discharged after the replenishment developer reaches a reference amount in the conveying screw.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, only the developer is replenished, and the volume of the developing device is increased without discharging until a specific timing. This is characterized in that the cycle interval of the discharge timing of the developer is increased to increase the circulation time of the newly supplied developer in the developing device.

  According to a third aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, further comprising means for detecting that the amount of the developer in the developing unit has exceeded an upper limit.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, when the developer is discharged, it is detected that the amount of the developer in the developing device is smaller than the reference amount. It has the means.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the developer conveying means is less than at least the means for detecting that the upper limit has been exceeded or the reference agent amount. The rotation is started and stopped according to the developer amount detecting means having any one of means for detecting this.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the charging roller, the photosensitive member, and the developing device are integrated, and the image forming apparatus is attached to and detached from the image forming apparatus. It has the process cartridge comprised so that it was possible.

  According to the present invention, it is possible to realize an image forming apparatus that can prevent a newly supplied developer from being discharged without being used and can fully utilize the new developer.

  Hereinafter, an image forming apparatus and a process cartridge usable in the image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus 1 having a plurality of two-component developing devices. FIG. 2 is an enlarged cross-sectional view centering on a photoreceptor and a developing device of the image forming apparatus shown in FIG. is there.

  The image forming apparatus 1 includes photosensitive drums 2A to 2D that are image carriers that carry an image at the time of image formation, a charging device 20 that charges the photosensitive drums 2A to 2D with a charging roller 7 that is a charging member, The electrostatic latent image formed by exposing the surface of the photosensitive drums 2 </ b> A to 2 </ b> D charged by the charging device 20 by the writing unit 5, which is an exposure unit, is developed by the developer 25 to be a visible image (toner image). Toner that remains on the surface of the photosensitive drums 2A to 2D after the visible image is transferred to the transfer material (transfer paper) P by the transfer device including the transfer belt 3 and the developing devices 4A to 4D. Is removed from the photosensitive drums 2A to 2D.

The charging roller 7 is provided with a conductive elastic member such as epichlorohydrin rubber having a volume resistance of 1 × 10 ³ to 1 × 10 ⁸ Ω · cm on the outer periphery of a cored bar formed by, for example, SUM-Ni plating. Yes.

  Then, a single-sided adhesive sheet film having a thickness of 50 to 60 μm made of polyester such as polyethylene terephthalate or polybutylene terephthalate is wound around both ends of the charging roller 7, and the photosensitive drums 2 </ b> A to 2 </ b> D are wound through the film material. The pressure is applied with a predetermined pressure. Thereby, the charging effective area portion of the charging roller 7 is maintained in a non-contact relationship with the surface of the photosensitive drums 2A to 2D. For this reason, wear of the photoconductor drums 2A to 2D can be avoided, which is useful for extending the life of the photoconductor.

  The charging roller 7 has the same linear velocity as the photosensitive drums 2A to 2D. As for the voltage application to the charging roller 7, for example, DC = −700 V is applied to the cored bar portion with a constant voltage, and an AC voltage is applied with constant current control.

  The developing devices 4A to 4D are two-component developing devices that perform development by holding toner with a developer and applying a bias. A double-sided printing unit 6 is shown below only a part of the photosensitive drums 2A to 2D. In the figure, reference numeral 8 denotes a fixing device for fixing the image on the transfer paper onto which the image has been transferred.

  The image forming apparatus of the present embodiment is preferably configured as a process cartridge in which the above-described charging roller, photoconductor, and developing device are integrated and detachable from the image forming apparatus.

  The carrier particles and toner constituting the developer used in this embodiment will be described.

  Carrier particles include copper zinc ferrite, ferrite containing manganese as a main component, and the like as the core material. Specifically, magnetic materials such as manganese ferrite and manganese magnesium ferrite are used. By adding a resistance adjusting agent typified by bismuth (Bi) or zircon (Zr), or adjusting conditions such as temperature, time, atmosphere, etc. in the firing step and the subsequent steps as appropriate, it has a high magnetic susceptibility and high resistance. A core material is obtained. Further, the ferromagnetic particles may be coated with an acrylic resin, a polyester resin, a silicone resin, a fluorine resin, or the like. These resins can be appropriately selected in consideration of the electric resistance of the carrier particles and the chargeability with the toner. Further, in order to adjust the characteristics of such carrier particles, a conductive substance such as carbon black, aluminum oxide, titanium oxide, a charge control agent, or the like may be added to the above-described resin. In addition to this, magnetic particles may be dispersed in the above resin.

  The weight average particle diameter of the carrier particles is preferably a small particle diameter of 25 to 45 μm. When the weight average particle diameter is 45 μm or less, the magnetic brush can be made dense, and the gradation and solid uniformity can be improved. On the other hand, if it is less than 25 μm, it is not preferable because carrier adhesion tends to occur.

  Moreover, it is preferable that the intensity | strength of the magnetization in 1 kOe of a carrier particle is 60-80 emu / g. In particular, when the carrier particles are reduced in size as described above, the magnetization becomes smaller and causes carrier adhesion and the like, and therefore, it is set to 60 emu / g or more. On the other hand, if the magnetization intensity exceeds 80 emu / g, the image quality of the formed image is deteriorated even if the carrier particles are surface-coated with a resin. The strength of magnetization can be adjusted by the type and amount of additives added to the core material.

  The toner includes at least a thermoplastic resin and a pigment such as carbon black, copper phthalocyanine, quinacridone, or bisazo. The thermoplastic resin is preferably a styrene-acrylic resin or a polyester resin. In addition, a wax such as polypropylene as a fixing aid and an alloy-containing dye for controlling the toner charge amount can be internally added. Furthermore, surface-treated silica, alumina, oxides such as titanium oxide, nitrides, carbides and the like may be externally added. Further, a fatty acid metal salt, resin fine particles and the like may be externally added together.

  The volume average particle diameter of the toner is preferably a small particle diameter in order to obtain a high-quality and high-definition image, specifically 3 to 8 μm. When the volume average particle size is smaller than the above range, the two-component developer is not preferable because the toner is fused to the surface of the carrier particles during long-term stirring in the developing device and the charging ability of the carrier particles is lowered. Moreover, when the volume average particle diameter is larger than the above range, it is difficult to obtain a high-quality and high-definition image, which is not preferable.

  The concentration of the toner in the developer is preferably 3 to 15 wt%. If the toner density is too low, an abnormal image called “bokeh” is generated in the halftone image due to conduction from the developing sleeve to the surface of the photoreceptor by the magnetic brush. Therefore, the toner concentration needs to be 3 wt% or more. In addition, by setting the toner concentration to 3 wt% or more, a sufficient image density can be obtained. On the other hand, if the toner concentration exceeds 15 wt%, background fogging or the like occurs in the image, and high image quality cannot be obtained, which is not preferable.

  The cleaning device 30 includes a cleaning blade 31. Further, the tip of the blade 31 is brought into contact with the surface of the photosensitive drums 2A to 2D with an optimum angle and contact pressure in order to remove the toner remaining on the photosensitive drums 2A to 2D. Further, a brush roller 32 is provided upstream of the cleaning blade 31, and rotates in the direction of arrow B at about 1.1 times the linear velocity of the photosensitive member. The cleaning blade 31 is easily scraped off from 2D.

The photosensitive drums 2A to 2D are formed by forming an undercoat layer (UL) on a conductive substrate made of aluminum and then applying a charge generation layer (CGL), a charge transport layer (CTL), and a surface protective layer in this order. It is formed. In this surface protective layer, fine powder of high-hardness particles, such as alumina fine powder of metal oxide, is dispersed, and in addition, silicon carbide, chromium oxide, silicon nitride, titanium oxide, α-iron oxide, silicon oxide, carbonized Calcium, zinc oxide, α-Fe ₂ O ₃ , talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide, calcium carbonate, Si (OH) ₂ · nH ₂ O, clay, boron carbide, cerium oxide, etc. Can be used. In addition, organic powders such as benzoguanamine resins and melamine resins, and fine powders such as various alloys can also be used. The fine powder particles have a Mohs hardness of 5 or more and an average particle size of 1 μm or less.

  Each of the photosensitive drums 2A to 2D has the same configuration, the photosensitive drum 2A forms an image corresponding to magenta, the photosensitive drum 2B forms an image corresponding to cyan, and the photosensitive drum 2C An image corresponding to the yellow color is formed, and the photosensitive drum 2D forms an image corresponding to the black color, and these are arranged at intervals in the transfer paper conveyance direction. Further, the developing devices 4A to 4D have the same configuration, and include a developing roller 9 that is close to or slidably contacted with the photosensitive drums 2A to 2D and two parallel stirring and conveying screws 10A and 10B, and only the color of the toner to be used is provided. Is different. The developing device 4A uses magenta, the developing device 4B uses cyan, the developing device 4C uses yellow, and the developing device 4D uses different colors of toner such as black.

  In this image forming apparatus, when the image forming operation is started, each of the photosensitive drums 2A to 2D rotates independently in the clockwise direction in FIG. 1, and a voltage is applied to the charging roller 7. As a result, the surface is uniformly charged. Then, a latent image of each color is formed on each charging surface of each of the photosensitive drums 2A to 2D after the writing unit 5 irradiates laser light corresponding to the image of each color. The latent images reach the positions of the developing devices 4A to 4D as the photosensitive drums 2A to 2D rotate, and are developed with the toners of magenta, cyan, yellow, and black to become toner images of the respective colors.

  When the transfer paper P is attracted to the transfer belt 3 and conveyed, the toner images of yellow, magenta, cyan, and black are sequentially transferred to the upper surface of the transfer paper and passed through the photosensitive drum 2D. A full-color toner image in which the four colors are superimposed is formed. Heat and pressure are applied to the transfer paper P on which the image is formed by the fixing device 8 to melt and fix the toner image, and then the paper is discharged.

  Next, the developer supply / discharge mechanism and the developer amount detection means will be described.

  FIG. 3 is a cross-sectional view showing an embodiment of replenishment and conveyance of developer containing toner of the two-component developing devices 4A to 4D used in the image forming apparatus of the present embodiment, and is a YY cross section in FIG. The toner tank 17 in FIG. 3 is located on the front side in FIG. 2, and the MONO pump 18 and the developer holding device 42 in FIG. Located and not shown. 4 is a partial cross-sectional view taken along the line ZZ in FIG. 2 showing the developing roller and the agitating and conveying screw of the developing device in FIG. The illustrated developing devices 4A to 4D include a developing roller 9 that is a magnet roller, and two agitating and conveying screws 10A and 10B arranged in parallel.

  The developer used in the developing devices 4A to 4D is conveyed while being stirred in the axial direction by the agitating and conveying screws 10A and 10B in a state where the toner concentration is 5 to 7 wt%, and is held by the developing roller 9 (FIG. 2). In the same manner as in the conventional example, it is subjected to development by a photosensitive drum. Although not shown in detail, a toner replenishing port 14 (FIGS. 3 and 4) is provided on the second-axis stirring and conveying screw 10B (FIG. 2) that is not on the developing roller 9 side among the stirring and conveying screws 10A and 10B. A shortage of toner is supplied from the toner supply port 14. In the figure, 15 is a partition plate, and 16 is a toner density sensor.

  In FIG. 3, reference numeral 17 denotes a toner cartridge, and the toner stored in the toner cartridge is supplied into the developing devices 4 </ b> A to 4 </ b> D by a Mono pump 18 attached to the toner supply port 14. Tubes 40A and 40B are connected to the tip of the MONO pump 18 via solenoid valves 19A and 19B, the opposite side of one tube 40A is connected to the nozzle 41, and the opposite side of the other tube 40B is the developer holding device. 42. The nozzle 41 is disposed in the toner cartridge 17 and sucks the toner therein. Further, the developer holding device 42 is connected to the developing devices 4 </ b> A to 4 </ b> D by a tube 43. In the figure, 44 is an air pump for the nozzle 41.

  The Mono pump 18 can be connected to a developing motor (not shown) by a clutch, and the clutch connection time can be turned on for a time calculated from the signal of the toner density sensor 16 for detecting the toner density and the pixel data. It is possible. Further, the electromagnetic valve 19A is simultaneously opened only when the clutch is turned on.

  In the developer holding device 42, only developer or carrier particles are stocked in advance. The developer or carrier is once supplied to the sub hopper 45 and replenished from the sub hopper 45 to the developing devices 4A to 4D by the rotation of the screw in the sub hopper. The developer holding device 42 is installed adjacent to the toner cartridge 17, and 0.2 g of carrier is supplied every 60 sheets. This operation is executed while no image is being formed.

  In the present embodiment, the developer upper and lower limit detection is performed using a developer upper and lower limit height sensor, and developer discharge control is performed. FIG. 5 is a cross-sectional view taken along the line XX of FIG. 4 and shows an enlarged view of the discharge port portion of FIG. The waste transport screw 55 can be controlled to start and stop rotating by driving a roller rotation control motor (not shown).

  In FIG. 5, a collection container 52 is installed below the developing containers 4 </ b> A to 4 </ b> D so as to cover the developer discharge port 50. Although this discharge port is not shown in the figure, several outlets are installed in the depth direction of the figure. Further, by providing the discharge port on the stirring and conveying screw 10A side, the replenisher is not directly discharged. The agent discharged to the collection container 52 is conveyed in the back direction of the drawing by the waste agent conveying screw, and is collected in a waste agent tank (not shown) by a tube (not shown).

  The roller rotation control motor is operated by a roller rotation control drive circuit controlled by a controller. Accordingly, when the roller rotation control motor is operated, the discharge agent conveying screw 55 starts or stops rotating, and a predetermined amount of developer is discharged from the developer discharge port 50, or the discharge of the developer is stopped. The upper and lower limits of the amount of developer in the developing containers 4A to 4D are detected by the developer upper limit height sensor S1 and the developer lower limit height sensor S2 provided in the developing containers 4A to 4D. This is realized by detecting the upper limit height and the lower limit height. The developer upper limit height sensor S1 and the developer lower limit height sensor S2 constitute developer amount detection means. Here, the discharge port is configured to be positioned below the lower limit height sensor S2.

  In FIG. 6, the controller includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory (eg, NVRAM: Non-Volatile RAM)), and an I / O (In / Out Interface). ) And the like. The controller receives a copy start signal, a set number of copies, a developer upper limit height detection signal S1 ′, a developer lower limit height detection signal S2 ′, and other input signals from a UI (User Interface). In response to these input signals, the controller outputs control signals for the replenishment clutch operating circuit and other operating circuits.

  The ROM in the controller stores a program that operates according to each input signal and necessary data. The controller operated by this program has a developer replenishment amount determining means for calculating a developer amount to be replenished, and a roller rotation control means.

  The roller rotation control means 3 always detects the upper surface height of the developer by the developer upper limit height sensor S1, and drives the motor when the developer is detected to be high (exceeds a predetermined value). A control signal is sent to rotate the roller to discharge the developer.

  On the other hand, when the controller detects that the upper surface height of the developer is low (lowers a predetermined value) by the developer lower limit height sensor S2, the roller rotation control means in the controller rotates the roller. The stop signal is output to stop the roller, and the discharge of the (developer) agent is stopped.

  In addition, only developer or carrier particles are stocked in advance in the developer holding device 42. When the old developing device is removed and a new developing device is installed, the number of rotations of the developing motor (not shown) of the developing devices 4A to 4D is stored in a memory such as NVRAM (Non-Volatile RAM). When the predetermined number of times is reached, the supply of developer or the supply of carrier particles is started. When the developer supply mode is started, the toner supply side electromagnetic valve 19A is closed and the developer supply side electromagnetic valve 19B is opened. With the motors of the developing devices 4A to 4D turned on and the clutch of the Mono pump 18 turned on, the tubes 43, the developer holding device 42, the tube 40B, the electromagnetic valve 19B, the Moron pump 18 and the developing device 4A are started from the developing devices 4A to 4D. The path of ˜4D is opened, and the developer can be supplied by the MONO pump 18. When the developer is conveyed for a certain time, the electromagnetic valve 19B and the clutch are turned off. This operation is executed while no image is being formed.

  The upper and lower limits of the amount of developer in the developing containers 4A to 4D are detected by the developer upper limit height sensor S1 and the developer lower limit height sensor S2 provided in the developing containers 4A to 4D. This is realized by detecting the upper limit height and the lower limit height. The developer upper limit height sensor S1 and the developer lower limit height sensor S2 constitute developer amount detection means. Here, the discharge port is configured to be positioned below the lower limit height sensor S2.

  In the present embodiment, for example, the developer can be increased from 200 g to 300 g in the developing device. By making the relationship between the stirring roller diameter and the developer amount appropriate, it is possible to sufficiently stir the developer and supply the agent to the developing roller regardless of the developer amount (200 to 300 g) in the developing device.

  In FIG. 2, when the developer amount is, for example, 200 g, which is the lower limit of the amount of developer, the developer lower limit height sensor S2 is set at, for example, half the height of the stirring roller 10B. The volume in the developing device is adjusted so that the height is, for example, ½ of the diameter. When the developer amount is, for example, 300 g, which is the upper limit of the developer amount, the developer upper limit height sensor S1 is installed at a height that is 7/8 of the stirring roller 10B, and the height of the developer is equal to the stirring roller diameter. The volume in the developing device is adjusted so that the height becomes 7/8.

  As a result, even when the developer amount is the upper limit amount, for example, 300 g, the predetermined height of the developing roller 10B, for example, 7/8, is not exceeded, so that the stirring rollers 10A, 10B are buried in the developer. Can be avoided, and sufficient stirring can be secured. Further, even when the developer amount is 200 g, which is the lower limit amount, the developer roller 10B does not fall below a predetermined height (for example, ½ height), so that a sufficient amount of developer is pumped up to the developing roller 9. Is possible. The heights of the height detection sensors S1 and S2 may be changed according to the volume and configuration of the developer used.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

  According to the above embodiment, the volume of the developer is increased, the circulation time of the newly supplied developer in the developer is lengthened, and the upper and lower limits of the amount of developer in the developer can be detected, In addition, since a system that enables the developer to be discharged at a target timing is provided, maintenance, ease of service, and image stability are realized.

  Further, according to the above embodiment, in trickle development, the agent is replenished without discharging until the agent reaches a certain amount, and the agent is discharged when a certain reference amount is reached. Circulates for a certain amount of time, and the newly replenished agent is prevented from being discharged without being used, and the agent that has not deteriorated is prevented from becoming a waste agent. An apparatus capable of realizing up is provided. By this method, it becomes possible to discharge the degraded agent more efficiently than before, and it is possible to realize the output of a high quality image.

  In addition, according to the above-described embodiment, the amount of developer that can be accommodated increases, the amount of developer in the developing device becomes full, the cycle of timing for discharging the developer can be lengthened, and a new supply is provided. Since the developer is circulated for a long time in the developing device, the usage efficiency of the developer is further improved.

  Further, according to the above-described embodiment, the volume of the developing device can be increased, the circulation time of the newly supplied developer in the developing device can be lengthened, and the amount of the agent in the developing device can be increased. By making it possible to detect the lower limit, and to make it possible to detect the upper and lower limits of the amount of the agent in the developing device, it is possible to realize that the start and end of the discharge of the agent are performed at the target timing.

  Further, according to the above-described embodiment, when the upper and lower limits of the developer amount are detected, the discharge agent screw starts or stops rotating, and when the agent becomes full, the discharge agent screw starts rotating. Then, when the minimum amount of the agent that can be developed is reached, the rotation of the discharge agent conveying screw can be stopped to prevent the new agent from being discharged.

  Further, according to the above embodiment, when an abnormality occurs, maintenance can be performed immediately by exchanging the cartridge. In addition, since most of the image problems are included in the cartridge, a stable image can be obtained by replacement.

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the vicinity of a photoconductor and a developing device of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a component developer supply / conveyance device of the image forming apparatus according to the exemplary embodiment of the present invention. 1 is a partial cross-sectional view of a developing device of an image forming apparatus according to an embodiment of the present invention. 1 is a partial cross-sectional view of a developing device of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram of a control device of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

2A, 2B, 2C, 2D Photosensitive drum 3 Transfer belt 4A, 4B, 4C, 4D Developing device 5 Writing unit 6 Duplex unit 7 Charging roller 8 Fixing device 9 Developing roller 10A Agitating and conveying screw 10B Agitating and conveying screw for second axis 14 Toner supply port 15 Partition plate 16 Toner density sensor 17 Toner cartridge 18 Mono pump 19A Toner supply side electromagnetic valve 19B Developer supply side electromagnetic valve 20 Charging device 30 Cleaning device 31 Cleaning blade 32 Brush roller 40A, 40B Tube 41 Nozzle 42 Development Agent holding device 44 Air pump for nozzle 41 Developer discharge port 52 Recovery container 55 Discharge agent conveying screw S1 Developer upper limit height sensor S2 Developer lower limit height sensor

Claims (6)

In an image forming apparatus having a developer conveying means comprising a developer conveying roller and an agitating and conveying screw for conveying a developer to a developing roller by an electrophotographic trickle developing method,
An image forming apparatus, wherein the developer is discharged after the replenishment developer reaches a reference amount in the stirring and conveying screw.   Only the developer is replenished, the volume of the developer is increased without discharging until a specific timing, the cycle interval of the timing for discharging the developer is increased, and the development of the newly supplied developer is performed. The image forming apparatus according to claim 1, wherein a circulation time in the container is increased.   3. The image forming apparatus according to claim 1, further comprising means for detecting that the amount of the developer in the developing unit exceeds an upper limit.   4. The image forming apparatus according to claim 3, further comprising means for detecting that the amount of the developer in the developing device is less than a reference agent amount when discharging the developer.   The developer conveying means starts and stops rotating according to a developer amount detecting means having at least either means for detecting that the upper limit has been exceeded or means for detecting that the amount is less than the reference agent amount. The image forming apparatus according to claim 4, wherein:   6. The image according to claim 1, further comprising a process cartridge in which the charging roller, the photosensitive member, and the developing device are integrated with each other and are detachable from the image forming device. Forming equipment.

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