JP5072205B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and a process cartridge used therefor.

In an electrophotographic image forming apparatus, a uniformly charged image forming body is subjected to image exposure to form a latent image, the latent image is developed into a toner image, and then the toner image is used as a transfer material such as recording paper. Transcription is performed. Then, when the transfer material carrying the toner image passes through the fixing device, the toner is fixed on the transfer material.

In developing a latent image, a two- component developer composed of a toner and a carrier is often used because of its excellent developability. The toner and the carrier are agitated in the developing device so that the toner is electrostatically attached to the outer surface of the carrier, and the toner is separated from the carrier under the condition that the toner is conveyed to the developing area and a developing bias is applied. It adheres electrostatically to the latent image portion. Since in the developing device the toner is consumed by development, the in the developing apparatus be provided a toner density detecting means for detecting the amount of toner in the developer using the inductance or the like, when the toner is lower than a predetermined ratio Toner is replenished into the developing device from a toner supply unit such as a toner hopper.

The toner in each developing device is replenished by the new toner consumed, but the carrier is used continuously. Therefore, when the 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 and a good toner image is obtained. It will not be. 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. The service business was made.

Therefore, conventionally, a new carrier is added at a fixed ratio together with the toner to be replenished, and a carrier whose development performance has deteriorated is gradually replaced with a new carrier, thereby making it unnecessary to replace the developer as a service operation. That is, a method called trickle development has been performed (see 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 by electrophotographic printing. An apparatus is disclosed that is guaranteed to be at least equal to the service life of the machine (see Patent Document 2).

For the problem of stabilizing the image density, an apparatus having a function of increasing the amount of developer in the container has been disclosed for the purpose of making the amount of toner on the developing roller constant (Patent Document). 3). In this method, the developer does not overflow until the developer is full. However, when the developer is full, the developer overflows and the newly supplied developer is discharged.

In addition, it is disclosed that a developer supply mode and a discharge mode are provided for the problem of discharging dust only before and after the operation of the machine (see 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 no countermeasure is taken against the problem of discharging a new developer.

As described above, in the prior art, a new carrier is added at a fixed ratio together with the toner to be replenished, and the developer whose service performance has deteriorated is gradually replaced with a new carrier, thereby replacing the developer as a service operation. Although it is realized that it is not necessary, the newly replenished developer instead of the deteriorated developer overflows from the outlet and is discharged without being used, and the new developer is wasted. There were still challenges.

Japanese Patent Publication No. 2-21591 Japanese Patent Publication No.7-111598 JP 11-167269 A JP 2001-209243 A

  Therefore, the present invention has been made in view of the above problems, and its problem is to prevent the newly replenished developer from being discharged without being used, while fully utilizing the new developer, It is to provide a stable density image output.

The features of the present invention, which is a means for solving the above problems, are listed below.
An image forming apparatus according to the present invention includes: an image carrier; and a developing device that supplies a two-component developer containing toner and a carrier to the image carrier to process an electrostatic latent image into a visible image. In the developing device, an upper space for storing the developer, a lower space for supplying toner and supplying the developer from the upper space , and maintaining the total amount of these in a steady amount. It has a, in the prior SL upper space is provided with a developer amount upper limit detection means for detecting that the amount of sump developer exceeds the upper limit, the pooled developer used for the visible image processing Without being discharged until the amount of developer accumulated in the upper space exceeds the upper limit, and replenishing toner in the lower space, and The developer is circulated and the upper When the developer amount retained in the space exceeds the upper limit, characterized by supplying a developer of the upper space at the same time to discharge the developer of the lower space in the space of the lower stage.

Specifically, according to the present invention, in trickle development having a one-cycle development stirring configuration, the developer is circulated in the developing device without discharging until the developer reaches a reference amount, and the supplied developer reaches a certain reference amount. In this system, the developer is discharged and the newly replenished developer is prevented from being discharged directly by closing the discharge port completely and circulating and stirring the developer. It can be used for. By this method, it becomes possible to discharge the deteriorated developer more efficiently than before, and it is possible to realize the output of a high quality image.

In the present invention, only the developer is replenished until the developer reaches the reference amount, and in a system in which the developer is not discharged, the inside of the developing device is divided into several spaces, and in one space, the developer becomes a steady amount. So that the developer can be stored in the other space, and if the conventional developing device is used, the developing device is expected to fill up in a short time. By increasing the volume of the space to be stored and increasing the amount of developer that can be accommodated in the developing device , the developer discharge timing cycle is lengthened, and a new supply agent is circulated and stirred for a long period before being discharged. System that enables stable image output and high-efficiency developer use by making the amount of developer constant in the space near the developing sleeve. It made.
In addition, the present invention has a function of detecting that the developer amount in the space for storing the developer exceeds the upper limit, thereby enabling the developer discharge to be started at a target timing. System.

In the image forming apparatus of the present invention, the developing device further includes a developing roller, and when supplying the developer from the upper space to the lower space, the developer replenishment amount in the lower space close to the developing roller A developer amount detecting means for controlling the above is provided.
In the present invention, when the developer is replenished from the space for storing the developer to the other space, the developer is replenished so that the amount of the developer becomes steady in the space near the developing roller. By providing developer amount detection means to control the replenishment amount and stabilizing the amount of developer near the developing roller , the amount of developer held on the developing sleeve can be stabilized and more stable image output is possible. System.

The image forming apparatus of the present invention further includes a drop port with a lid that can be opened and closed to replenish the developer from the upper space to the lower space, and based on the developer amount detecting means from the upper to the lower. The dropping port is opened and closed in response to the signal output to the terminal.
In order to supply the developer from the space where the developer is stored to the other space, the developer is provided with a drop opening that can be opened and closed, and the developer is moved from the space where the developer is stored to a space where the developer amount is maintained at a steady amount. The developer amount is kept constant in the space near the developing roller by receiving the signal output based on the amount detection means, opening and closing the drop opening, and allowing the developer to be supplied at the desired timing. Therefore, the system can output more stable images.

The image forming apparatus of the present invention is further provided with a developer amount lower limit detecting means for detecting that the developer amount in the upper space is below a lower limit during discharging of the developer in the upper space. And
The present invention, when the discharge of the current image agent is being performed, by having a function of amount of developer space to be pooled developer detects that the lower limit, the discharge of the developer at the time of interest It becomes a system that makes it possible to realize the termination of the process.

The image forming apparatus of the present invention is further characterized in that a shutter that can be opened and closed according to the developer amount detecting means is provided at the drop opening with the lid that can be opened and closed.
The present invention, by having the shutter fall opening of the openable lid for supplying the space to be pooled upper developer in the lower part of the space, performs control using the pre Kigen image amount detecting means System. That is, the shutter is opened and closed at the timing when the upper and lower limits of the developer amount in the space for storing the developer are detected, and when the developer is full, the shutter is opened, and the minimum developer amount that can be developed is reached. In this case, the shutter is closed.

The image forming apparatus of the present invention is further characterized in that the developer amount detecting means adjusts the opening and closing of the shutter to keep the developer amount in the lower space constant.
According to the present invention, since the lower developer amount provided in the lower space has a function of adjusting the opening and closing of the shutter by the developer amount detecting means provided to keep the lower developer amount constant, the lower developer is excessively increased. Thus, the developer can be discharged while keeping the lower developer amount constant.

The image forming apparatus of the present invention further includes a toner replenishing port in the lower space and a developer dropping port downstream of the toner replenishing port in the developer transport direction.
The present invention, by having a drop opening of the developer downstream of the bets toner supply opening in the developer carrying direction, after the toner is supplied, it is possible to drop the developer circulated from the developer fall opening, toner The toner dropped from the replenishing port is easily transported near the upper surface inside the developing device , but the toner that is easily transported near the upper surface is developed by dropping the circulating developer from the upper stage through the dropping port immediately after toner replenishment. It becomes a system that realizes sufficient mixing with the agent.

The image forming apparatus of the present invention further includes a toner supply port in the lower space, and a developer discharge port upstream of the toner supply port in the developer transport direction.
By upstream of bets toner replenishing port has an outlet of the developer, the system to prevent the developer newly replenished is discharged directly.

The image forming apparatus of the present invention is further characterized in that the image carrier and the developing device are integrated to form a process cartridge that can be attached to and detached from the image forming apparatus main body.

The present invention prevents the newly supplied developer from being discharged without being used by the means for solving the above problems, and provides a stable density image output while fully utilizing the new developer. be able to.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

FIG. 1 is a schematic cross-sectional view showing an image forming apparatus 1 having a plurality of two-component developing devices, and FIG. 2 is an enlarged cross-sectional view showing the vicinity of the photosensitive member and the developing device of the image forming apparatus shown in FIG.
This image forming apparatus includes photosensitive drums 2A to 2D that are image carriers that carry an image during 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 apparatus 20 by the writing unit 5 serving as an exposure unit is developed by the developer 25 to form a visible image (toner image). Toner (transfer residual toner) remaining on the surfaces of the photosensitive drums 2A to 2D after the developing devices 4A to 4D and the transfer device including the transfer belt 3 transfer the visible image onto the transfer material (transfer paper) P. And a cleaning device 30 for removing the photosensitive drums 2A to 2D.

The charging roller 7, for example, of a core formed by SUM-Ni plating, that have an elastic member having a conductive epichlorohydrin rubber or the like with a volume resistivity ^{1 × 1 0 3 ~ 1 ×} 10 8 Ω · cm .
Their to the both end portions of the charging roller 7 wound on one side adhesive sheet film having a thickness of 50~60μm of polyester or polyethylene terephthalate for example, the photosensitive drum 2A~2D through the film material, the predetermined pressure Pressurized by 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 that of 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 at a constant voltage, and an AC voltage is applied by 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 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.

Next, carrier particles and toner as a developer used in the present invention will be described.
Examples of the core material of the carrier particles, copper zinc ferrites, ferrites etc. elevation Gerare composed mainly of manganese, specifically, manganese ferrite, and the like manganese magnesium ferrite. By adding a resistance adjusting agent typified by bismuth (Bi) or zircon (Zr), or adjusting the conditions such as temperature, time, atmosphere, etc. in the firing process and subsequent processes as appropriate, a highly magnetized and highly resistant core material can be obtained. can get. 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 the carrier particles, carbon black, oxide Al Miniumu, conductive material such as titanium oxide, a charge control agent may be added to the 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, a thickness of less than 25 μm is not preferable because carrier adhesion occurs.
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 kind and amount of additives added to the core material.

  As the toner, a toner including at least a thermoplastic resin and a pigment such as carbon black, copper phthalocyanine, quinacridone, or bisazo is used. As the resin, styrene-acrylic and polyester resins are preferable. 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 toner concentration 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, and the tip of the blade 31 is at an optimum angle with respect to the surface of the photosensitive drums 2 </ b> A to 2 </ b> D in order to remove toner remaining on the photosensitive drums 2 </ b> A to 2 </ b> D. And contact with contact pressure. Further, a brush roller 32 is provided upstream of the cleaning blade 31 and rotates in the direction of arrow B at x1.1 times the linear velocity of the photosensitive member, and residual toner is transferred to the photosensitive drums 2A to 2D. The cleaning blade 31 is easily scraped off.

In each of the photosensitive drums 2A to 2D, an undercoat layer (UL) is formed on a conductive substrate made of aluminum, and a charge generation layer (CGL), a charge transport layer (CTL), and a surface protective layer are further coated thereon. It has been crafted. The surface protective layer has fine particles of high hardness particles, for example, alumina dispersed as a fine powder of metal oxide. In addition, silicon carbide, chromium oxide, silicon nitride, titanium oxide, α-iron oxide, silicon oxide , calcium carbide, zinc oxide, alpha-Fe ₂ O _3, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide, calcium _{carbonate, Si (O H 2) ·} n H 2 O, clays, boron carbide Further, cerium oxide or the like can be used. In addition, organic powders such as benzoguanamine resins and melamine resins, various alloys, and the like can also be used. The hardness of the fine powder particles is Mohs hardness of 5 or more, and the average particle size is 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. The developing devices 4A to 4D also have the same configuration, and include a developing roller 9 that is in close proximity or sliding contact with the photosensitive drums 2A to 2D and two parallel agitating and conveying screws 10A and 10B, and only the color of the toner to be used is provided. 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 is rotated clockwise in FIG. Uniformly charged. The charging surfaces of the photosensitive drums 2A to 2D are respectively irradiated with laser beams corresponding to the images of the respective colors by the writing unit 5, and latent images corresponding to the respective colors are formed thereon. 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.
Then, while adhering the transfer paper P to the transfer belt 3 and transporting it, the toner images of yellow, magenta, cyan and black are sequentially transferred to the upper surface in FIG. 1 and passed through the photosensitive drum 2D. Sometimes a full-color toner image is formed by superimposing four colors. On the transfer paper P on which the image is formed, the fixing device 8 applies heat and pressure to melt and fix the toner image, and then discharges the toner image.

Next, the developer supply / discharge mechanism and the developer amount detection means, which are the features of the present invention, will be described.
4A and 4B are schematic views of the developing devices 4A to 4D arranged on the lateral side of the photosensitive drum, FIG. 4A is a YY sectional view of FIG. 2, and FIG. 4B is a ZZ sectional view of FIG. In FIG. 4a, 15 is a partition plate, and 16 is a toner density sensor. Further, in FIG. 2, a screw (or roller) that is a developer conveying means with a black circle (●) in the center represents that the developer is conveyed from the back side to the near side in the figure. Those marked with x indicate that the developer is transported from the near side to the far side in the figure.

The developing devices 4A to 4D according to the present invention have the following configuration. That is, a developing roller 9 as a developer carrying member, a collecting roller 10D as a developer collecting and conveying means, a first stirring and conveying screw 10C as a first developer agitating and conveying means, and a second developer agitating and conveying means. It has a second agitating and conveying screw 10B and a supply and conveying screw 10A that is a developer supply and conveying means.

In the developing device main bodies 4A to 4D, a recovery roller 10D adjacent to the developing roller and a developer collecting chamber containing a first stirring and conveying screw 10C serving as a first developer agitating and conveying means, and a first developer agitating and conveying. A chamber (hereinafter also referred to as a recovery / first stirring / conveying chamber) 10C ′ is provided. Further, a second developer stirring and conveying chamber (hereinafter also referred to as a second stirring and conveying chamber) 10B ′ which is a second developer stirring and conveying chamber containing the second stirring and conveying screw 10B is provided in the first agitating and conveying chamber 10C ′. A developer supply / conveying chamber (hereinafter also referred to as a supply / conveying chamber) 10A ′ provided below and containing the supply / conveying screw 10A is provided adjacent to the second stirring / conveying chamber 10B ′ and the developing roller 9.

The developing device main bodies 4A to 4D are provided between the supply conveyance chamber 10A ′ and the second developer agitation conveyance chamber 10B ′, and are supplied and conveyed without being supplied to the developing roller 9 from the supply conveyance chamber 10A ′. The first communicating portion 10AB, the supply conveying chamber 10A ', and the second developer agitating and conveying chamber, which are first communicating portions for transferring the developer conveyed to the most downstream in the chamber 10A' to the second agitating and conveying chamber 10B '. 10B ′, and a second communicating portion 10BA that is a second communicating portion that transfers the developer conveyed by the second agitating and conveying screw 10B to the supply conveying chamber 10A ′.

The second developer agitating / conveying chamber 10B ′ is provided with a toner replenishing portion 14 for replenishing toner, and the developer conveyed by the first agitating / conveying screw 10C is provided downstream of the toner replenishing portion 14 for the first time. (2) A dropping port 57 for transferring to the developer stirring and conveying chamber 10B ′ is provided. The recovery / first agitating / conveying chamber 10C 'is provided with the aforementioned drop port 57 for transferring the developer to the second developer agitating / conveying chamber 10B' and the carrier replenishing port 43 for supplying the carrier.

In the developing devices 4A to 4D according to the present invention, as shown by the arrows in FIGS. 4a and 4b, the following developer circulation is performed.
First, the developing roller 9 is a cylindrical conductor and includes a rotatable developing sleeve and a plurality of magnetic poles (not shown) built in the developing sleeve, and is supplied from a developer supply / conveying screw 10A adjacent to the developing roller 9. The electrostatic latent images on the photosensitive drums 2A to 2D are developed using a two-component developer composed of toner and carrier.

The developer used for development is removed from the developing roller 9 by the action of a repulsive magnetic field from a magnetic pole called a release magnetic pole among a plurality of magnetic poles arranged in the developing roller 9. In the developing device according to the present invention, the developer used for image formation is once completely removed from the surface of the developing roller 9 by the collecting roller, and then a new developer is supplied to the surface of the developing roller 9 from the supply screw 10A. It is said. The developer removed from the surface of the developing roller 9 by the collecting roller is collected by a collecting roller 10D that is a developer collecting means, and the developer collected by the collecting roller is collected by the inclination of the collecting / first stirring and conveying chamber 10C ′. It flows down to the 1st stirring conveyance screw 10C sequentially. In FIG. 2, as an example of the developer transport method, the developer in the collection and first agitation transport chamber 10 </ b> C ′ is transported from the near side to the far side as shown in FIG. 4B.

Next, a carrier replenishing port is provided in the collection / first agitating / conveying chamber 10C 'to allow replenishment of the carrier. The developer replenished with the carrier upstream in the collection / first stirring / conveying chamber 10C ′ falls from the dropping port provided in the downstream area of the collecting / first stirring / conveying chamber 10C ′ as shown in FIG. 2 Transferred to the agitating and conveying chamber 10B ′. FIG. 2 is a cross-sectional view taken along the line XX in FIG. In the developing device according to the present invention, the toner replenishing port 14 is provided upstream of the dropping port in the second agitating / conveying chamber 10B ′, and toner is replenished to the developer whose toner content (toner concentration) is reduced. It is possible.

In the second agitating and conveying chamber 10B ', the developer added with the replenishing toner is agitated and conveyed by the second agitating and conveying screw 10B. As shown in FIG. 4a, in the second agitation transport chamber 10B ', the developer is transported in a direction opposite to the developer transport direction in the recovery transport chamber 42 at the previous stage. As an example of the transport direction, FIG. 2 shows that the developer transport direction in the second agitation transport chamber is transported from the back side to the near side in the drawing.

As shown in FIG. 4A, the developer stirred and conveyed by the second agitating / conveying screw 10B ′ is supplied to the supply conveying chamber 10A ′ via the second communicating portion 10BA in the most downstream region of the second agitating / conveying chamber 10B. Be transported. In the supply conveyance chamber 10A ', the developer is supplied onto the developing roller 9 adjacent to the supply conveyance chamber 10A' while being conveyed in the supply conveyance chamber 10A 'by the supply conveyance screw 10A. Note that the developer conveyance direction in the supply conveyance chamber is conveyed from the near side to the far side in FIG.

The first agitating and conveying screw 10C and the second agitating and conveying screw 10B are agitated and conveyed so that the toner and the carrier constituting the developer are uniformly dispersed and the toner is sufficiently charged. .

In this embodiment, the toner replenishing port 14 and the carrier replenishing port 43 are provided independently of each other. However, in the developing device according to the present invention, as in the case where the toner and the carrier are supplied in a mixed state, The developer may be supplied through one supply port.

In the present invention, the developer that has been transported to the vicinity of the end of the supply transport chamber 10A ′ and has not been supplied to the developing roller 9 is once again passed through the first communication portion 10AB as shown in FIG. 4a. 2 Transferred into the agitating and conveying chamber, agitated and conveyed again by the second agitating screw 10B, and transferred to the supply conveying chamber 10A ′.

As described above, in the developing device according to the present invention, the first communication portion for transferring the developer to the second agitating / conveying chamber is provided in the most downstream region of the supplying / conveying chamber 10A ′, and the developing roller 9 is provided in the supplying / conveying chamber 10A ′. The developer that has not been supplied is returned to the second agitating and conveying chamber, and the opportunity for supply to the developing roller 9 is increased again in a short time.

In the developing devices 4A to 4D of the present embodiment, the developer is circulated and conveyed as described above, and the developer used for image formation is once completely removed on the developing roller 9 and then newly developed. Supply is performed to develop the electrostatic latent image formed on the photosensitive drum.

FIG. 3 is a cross-sectional view showing an embodiment of replenishment / conveyance of developer containing toner of the two-component developing devices 4A to 4D according to the present invention.
In the figure, reference numeral 17 denotes a toner cartridge. The toner accommodated in the toner cartridge is supplied into the developing devices 4A to 4D 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. 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. Yes. The electromagnetic valve 19A is opened simultaneously only when the clutch is turned on.

  In the developer holding device 42, only developer or carrier particles are stocked in advance. When the old developing device is removed and a new developing device is installed, the number of rotations of a developing motor (not shown) of the developing devices 4A to 4D is stored in a memory such as NVRAM, and when this number of rotations reaches a predetermined number, the developer Supply or 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 following is a description of the developer discharging method.
In this embodiment, the upper and lower limits of the developer amount are detected using a developer upper and lower limit height sensor, and the developer discharge is controlled. FIG. 5 is a cross-sectional view taken along the line X′X ′ of FIG. 4 a, showing a cross-sectional view of the portion just corresponding to the discharge port, and an enlarged view of the collection container 52 installed in the developing device, the waste transport roller 55, and the shutter 51 provided at the discharge port. FIG. The shutter 51 can be moved up and down by driving a shutter opening / closing 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. By providing the discharge port upstream of the toner supply port and the drop port, the supply toner and the carrier are not directly discharged. The developer discharged to the collection container 52 is transported in the depth direction of the drawing by a waste transport screw and is collected in a waste tank (not shown) by a tube (not shown).

The shutter opening / closing motor is operated by a shutter opening / closing motor drive circuit controlled by a controller. Therefore, when the shutter opening / closing motor operates, the developer discharge shutter 51 moves up and down, 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 on the upper surface of the developer by the developer upper limit height sensor S1 and the developer lower limit height sensor S2 provided in the upper stage of 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 detecting means.

In FIG. 6, the controller is constituted by a microcomputer having a CPU (Central Processing Unit) , ROM (Read Only Memory), RAM (Random Access Memory), I / O (Input / Output Interface) and the like. The controller C receives a copy start signal and a copy set number input from the UI, a developer upper limit height detection signal S1 ′, a developer lower limit height detection signal S2 ′, and other input signals. The controller outputs control signals for a replenishing clutch operating circuit, a shutter opening / closing motor driving circuit 66, a drop port opening / closing motor driving circuit, and other operating circuits in accordance with the input signals.

The ROM of the controller stores a program that operates according to the input signals and necessary data. The controller operated by the program has functions such as a developer replenishment amount determining means for calculating the amount of developer to be replenished, a shutter control means, and a drop mouth cover control means.

In this embodiment, the developer can be increased from 0 g to 200 g in the upper stage in the developing unit. In FIG. 2, the developer lower limit height sensor S2 is installed obliquely above the dropping port, and the developer upper limit height sensor S1 is adjusted to a height when the amount of developer in the upper stage of the developer reaches 200 g. When the shutter control means detects that the upper surface height of the developer is higher than the developer upper limit height sensor S1, the shutter control means drives the shutter opening / closing motor to open the shutter 51. At the same time, when detecting that the developer height is higher than the developer upper limit height sensor S1, the drop opening control means drives the drop opening lid opening / closing motor to open the drop opening 57. When it is detected that the upper surface height of the developer is lower than the developer lower limit height sensor S2, the shutter opening / closing motor is driven to close the shutter 51. At the same time, when detecting that the developer height is lower than the developer lower limit height sensor S2, the dropping port control means drives the dropping port lid opening / closing motor to close the dropping port 57.

Further, the developer level sensor S3 is placed on the supply conveyor screw 10A side, the drop opening control means detects that the developer from the developer level sensor S3 is small, falling palate 56 by driving the motor Is opened for a predetermined time to replenish the developer. The drop port control means drives the motor to close the drop port lid 56 after a predetermined time has elapsed. Opening and closing operation of the aforementioned falling palate is repeated until the developer is filled to a developer level sensor S3 position. Here, when it is detected that the height of the upper surface of the developer is less than the developer height sensor S3 when the shutter and the drop opening are open, the shutter control means drives the motor to close the shutter. The shutter control means opens the shutter by driving the motor after a predetermined time has elapsed. The shutter opening / closing operation described above is repeated until the developer is filled up to the position of the developer height sensor S3.

1 is a schematic sectional view showing an image forming apparatus 1 including a plurality of two-component developing devices. FIG. 2 is an enlarged cross-sectional view showing the vicinity of a photoconductor and a developing device of the image forming apparatus shown in FIG. 1. FIG. 3 is a cross-sectional view illustrating an embodiment of developer replenishment / conveyance in the two-component developing device according to the present invention. It is YY sectional drawing of FIG. It is ZZ sectional drawing of FIG. FIG. 3 is an X′X ′ cross-sectional view of FIG. 2 and an enlarged view of the vicinity of a discharge port. It is a block diagram of the Example of this invention .

Explanation of symbols

2A to 2D Photosensitive drums 4A to 4D Developing device 3 Transfer belt 5 Writing unit 6 Duplex unit 8 Fixing device 7 Charging roller 9 Developing roller 10A Supply conveying screw 10B Second agitating and conveying screw 10C First agitating and conveying screw 10D Recovery roller 10A ′ Supply conveyance chamber 10B ′ Second agitation conveyance chamber 10C ′ Recovery / first agitation conveyance chamber 10AB First communication portion 10BA Second communication portion 14 Toner supply port 17 Toner cartridge 15 Partition plate,
16 Toner concentration sensor 20 Charging device 30 Cleaning device 31 Cleaning blade 32 Brush roller 18 Mono pump 19A Electromagnetic valve 19B on toner supply side Electromagnetic valve 42 on developer supply side Developer holding device 43 Carrier supply port 44 Air pump 40A for nozzle 41 Tube 40B Tube 50 Developer discharge port 51 Developer discharge shutter 52 Recovery container 55 Waste transport screw 56 Drop port lid 57 Drop port
S 1 Developer upper limit height sensor S2 Developer lower limit height sensor S3 Developer height sensor

Claims (9)

An image carrier;
A developing device that supplies a two-component developer containing toner and a carrier to the image carrier to process the electrostatic latent image into a visible image;
The developing device has an upper space for storing developer, and a lower space for supplying toner and supplying developer from the upper space , and holding the total amount of these to a steady amount. And
The prior SL upper space is provided with a developer amount upper limit detection means for detecting that the amount of sump developer exceeds the upper limit, the pooled developer recovered without being used for the visible image processing Developer,
The upper space is replenished and the developer is circulated without discharging the developer in the lower space until the developer amount accumulated in the upper space exceeds the upper limit. An image forming apparatus , wherein when the developer amount accumulated in the upper limit exceeds an upper limit, the developer in the lower space is discharged and simultaneously the developer in the upper space is replenished to the lower space . The developing device includes a developing roller,
The developer amount detecting means for controlling a developer replenishment amount is provided in the lower space close to the developing roller when the developer is replenished from the upper space to the lower space. The image forming apparatus described. In order to replenish the developer from the upper space to the lower space, a drop port with a lid that can be opened and closed is provided, and the signal is output from the upper to the lower row based on the developer amount detection means. The image forming apparatus according to claim 2, wherein the mouth is opened and closed. 4. The developer amount lower limit detecting means for detecting that the developer amount in the upper space falls below a lower limit during developer discharge in the upper space. 5. The image forming apparatus according to one. 5. The image forming apparatus according to claim 3 , wherein a shutter that can be opened and closed according to the developer amount detecting unit is provided at the opening having a lid that can be opened and closed. The image forming apparatus according to claim 5, wherein the developer amount detecting unit adjusts opening and closing of a shutter to keep the developer amount in the lower space constant. The image according to any one of claims 1 to 6, further comprising a toner replenishing port in the lower space, and a developer dropping port downstream of the toner replenishing port in the developer transport direction. Forming equipment. 8. The image according to claim 1, further comprising a toner supply port in the lower space, and a developer discharge port upstream of the toner supply port in the developer transport direction. Forming equipment. 9. The image forming apparatus according to claim 1, wherein the image carrier and the developing device are integrated to form a process cartridge that can be attached to and detached from the image forming apparatus main body. .

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