JP2003167442A - Method for controlling toner recycling of electrophotographic device using liquid developer with high viscosity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling toner recycling to stably supply a liquid developer having proper liquid developer concentration to a liquid developing device using a liquid developer of high viscosity and to control the residual developer recovered after the development so as to resume a proper concentration and to supply again. <P>SOLUTION: The device is equipped with a concentration controlling tank where the residual developer after the development from a developer supporting body and the residual developer after the transfer from an image carrying body are recovered, the recovered developer is reserved to control the concentration of the developer and then to supply as a developer to the developer supporting body, and a concentrated developer and a carrier liquid are supplied to control the concentration of the developer liquid, and with a buffer tank where the liquid developer with controlled concentration in the concentration controlling tank is carried and reserved. The liquid developer controlled to proper concentration is supplied from the buffer tank to the developer supporting body. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner recycling control system for an electrophotographic apparatus, which collects a residual developer after development and after transfer, adjusts the concentration, and supplies the developer as a developer again.

[0002]

2. Description of the Related Art In a liquid developing electrophotographic apparatus, a toner liquid in which toner particles are dispersed in a carrier liquid is used as a developing liquid. The developing solution is adjusted to a concentration suitable for development in advance and supplied to the developing section, but after development, part of the toner particles and carrier solution moves to the image carrier (photosensitive drum), and the rest from the developing section. Be recovered. The concentration of the developer collected from the developing unit changes due to the loss of the moving toner particles (and part of the carrier) determined by the ratio of the image area / non-image area of the screen. That is, the developer collected at this point is not in a state suitable for development and cannot be reused as it is.

Although it is possible to discard all of the collected developing solution, in order to collect and reuse the developing solution from the viewpoint of cost and environment, the concentration of the toner collected in the apparatus is adjusted and the toner is collected again. It is desirable to supply to the developing section.

In the conventional electrophotographic apparatus using the low-viscosity liquid developer, the low-concentration low-viscosity liquid developer is excessively supplied to the latent image portion of the image carrier to form an image. Excess liquid developer at that time is collected and supplied again to the developer support (developing roller). As the circulation of the supply and recovery of the liquid developer is repeated, the solid components in the liquid developer are consumed and the required image density cannot be obtained. Therefore, the concentrated liquid developing solution is replenished and adjusted so that the liquid developing solution has a predetermined concentration, and the liquid developing solution is sent to the developing solution support.

As described above, the conventional low-viscosity liquid developer is
Since it is excessively supplied to the latent image portion, the concentration of the liquid developer supplied can have a certain allowable range.
However, since such a liquid developing solution is a volatile liquid, the volatilized liquid has to be collected in the apparatus, and there is a problem that the scale of the apparatus becomes large.

On the other hand, a liquid developing apparatus using a non-volatile high concentration, high viscosity liquid developer forms a thin layer of the liquid developer on a developer support in an amount suitable for obtaining a required image density. However, since the liquid developer is supplied to the latent image portion of the image carrier, in this case, the liquid developer is circulated in the developing device and there is no liquid to volatilize, so that a large-scale liquid recovery device is not required.
In the case of such a liquid developing apparatus, it is necessary to form a thin layer of a proper amount and a proper amount of the liquid developing solution on the developing solution support, and therefore, a liquid having a stable concentration is formed on the developing solution support. Developer needs to be supplied.

Further, in the case of the conventional low-viscosity liquid developer, since the solid content ratio required for toner is relatively small, it can be easily transported by a pump, and a flow meter or the like is arranged in the transport path to control the flow rate. Further, regarding the concentration control, it is possible to adopt an easy and efficient method, for example, by allowing the liquid to pass through the slit portion and controlling the concentration by the light transmission concentration or the like. On the other hand, with a high-viscosity liquid developer, it is difficult to install a flow meter because toner sticking may occur in the water that has been left in the pipe for a long time when the power is not turned on. There is also a need for another type of device for concentration control.

[0008]

SUMMARY OF THE INVENTION The present invention is a liquid developing apparatus which uses a highly viscous liquid developing solution to form a thin developing solution layer on a developing solution support and then develops the liquid developing apparatus. It is an object of the present invention to provide a toner recycling control system in which a liquid developer having a different developer concentration is stably supplied and the residual developer collected after development and after transfer is readjusted to an appropriate concentration and supplied.

[0009]

SUMMARY OF THE INVENTION A toner recycle control system for an electrophotographic apparatus according to the present invention is a development residual developer from a developer support of a developing device for forming and developing a thin layer of a highly viscous liquid developer. , And the residual transfer developer from the image carrier is recovered, the concentration of the developer is adjusted, and then the developer is supplied to the developer support again as a developer. Therefore, in addition to the concentration adjusting tank that stores the collected developing solution and supplies the concentrated developing solution and the carrier solution to adjust the concentration of the developing solution, the liquid developing solution whose concentration is adjusted in this concentration adjusting tank is transported and stored. It is equipped with a buffer tank. The liquid developer adjusted to an appropriate concentration is supplied from the buffer tank to the developer support.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail according to embodiments. FIG. 1 shows a schematic configuration diagram of a toner recycling apparatus to which the present invention can be applied.
An electrophotographic apparatus using a high-viscosity liquid developer usually includes, as main components, an image carrier (photoconductor), a developer for each color including a developer support, and an intermediate transfer member.
The image carrier is further provided with a charger (not shown) for charging the image carrier to a predetermined potential, and an exposure device (not shown) for exposing the image carrier after charging to form an electrostatic latent image thereon.

The developer support (developing roller) is usually provided in association with yellow / magenta / cyan / black and has a toner viscosity of 400 to 4000 mPa · S.
Then, a liquid developer having a carrier viscosity of 2.5 cSt to 1000 cSt, preferably 20 to 200 cSt is used to form a toner layer having a thickness of 5 to 20 μm on the developer support. The developer support is charged to a predetermined potential by supplying positively (or negatively) charged toner particles to the image carrier according to an electric field between the developer carrier and the image carrier, thereby exposing the image carrier. Toner particles are attached to the portion (or unexposed portion).

The intermediate transfer member transfers the toner attached to the image carrier according to an electric field between the intermediate transfer member and the image carrier, and then transfers and fixes the toner on the print medium. Alternatively, as in the case of monochrome printing in particular, the image can be directly transferred and fixed to the print medium without passing through the intermediate transfer member.

In the liquid developing apparatus using such a highly viscous and highly concentrated liquid developing solution, the image density developed on the image bearing member is the solid content contained in the liquid developing solution on the developing solution support. Depends on. Therefore, in such a developing device, it is necessary to keep the solid content concentration of the liquid developer constant. A suitable concentration for printing developer is 12.5%
It is not possible to stably obtain the required good printing quality unless the concentration is controlled within ± 0.5%, which is the solid content ratio.

When the developing solution adjusted to the optimum density is supplied to the developing section, the solid content of the developing solution is developed in accordance with the ratio of the developing section and the non-developing section of the electrostatic latent image which is determined depending on the printing content. It Further, the carrier liquid is also removed at a certain ratio when the developing section comes into contact with the image bearing member. In this way, the developer that has passed through the developing unit and still remains in the developing unit has its density changed from the state adjusted to the density suitable for the initial printing by the above operation. In order to use the developing solution whose density has changed in this way for printing again, a process of recovering the density to a predetermined state is required.

In the illustrated toner recycling device, the residual developing solution after use is collected in the concentration adjusting tank. The residual developer after development from the developer support is collected in the concentration adjusting tank through the pump 3, and the residual developer from the image carrier is collected in the concentration adjusting tank through the pump 4. The recovered liquid developer is added to the concentration adjusting tank by dropping high-concentration developer or carrier liquid according to the output of the concentration sensor and stirring, for example, 5%.
Adjusted to a predetermined developer concentration of ~ 30%.

At this time, in order to adjust the concentration to a predetermined concentration, a concentrated developer having a concentration higher than the predetermined concentration of the developer, for example, a concentrated developer having a concentration of 40%, is discharged from the high-concentration developer tank storing the concentrated developer. Supplied through a drip pump, or
A carrier liquid for diluting a developer having a high concentration to a predetermined concentration is supplied from a carrier liquid tank in which it is stored to a concentration adjusting tank through a carrier liquid drop pump. In order to mix it so that the concentration of the developer is
An agitator coupled to the agitator motor is provided.

The multicolor printing apparatus is equipped with a concentrated developer container for each color and one common carrier liquid container, and supplies the carrier liquid from the common carrier liquid container to the concentration adjustment tank for each color. With the configuration, the mounting area can be reduced and the configuration can be made compact.

When the concentration of the developing solution in the concentration adjusting tank is determined to be full, the liquid concentration adjusting operation is not performed and the waste tank is pumped until the concentration can be adjusted. Run 5 to discard the developer. At this time, during printing or the like, the collected developer is dropped from the developer support or the image carrier at any time, so it is necessary to discard the developer in excess of the dropped amount. The volume sensor controls the operating amount of the waste pump to ensure that the liquid level drops.

The means for forming the layer for detecting the concentration is to draw up the developing solution from the concentration adjusting tank using a plurality of roller pairs,
The developing solution is conveyed by rollers and spread thinly to form a thin layer of the developing solution uniformly formed on the final stage roller. Further, at this time, a pattern roller can be used as a means for regulating the developer coating amount in order to stabilize the layer thickness. The pattern roller is a well-known roller which forms vertical and horizontal fine grooves (patterns) on the roller surface and conveys a certain amount of developing solution using the grooves.

The density is detected by measuring the light reflected through the thin layer of the final stage roller with a reflection densitometer. Liquid developer concentration 5 to 30%, preferably 10% to 2
0% developer is used. Therefore, when the developer concentration is detected by the reflected light of the optical sensor, if the developer is too thick, the output is saturated and cannot be detected. Since it can be detected by an optical sensor, it is possible to adjust the developer concentration by forming a thin developer layer having a thickness of 5 to 30 μm, preferably 10 to 20 μm, and then detecting the reflection density thereof.

Nothing is done when the output of the reflection densitometer is within a certain allowable range from the output at the optimum density, but when the density is higher than the upper limit (for example, 13%) of the allowable range of the density. Is the carrier stock solution, and if it is lower than the lower limit of the permissible range (for example, 12%), the developer concentration higher than the optimum printing concentration (for example, 25%) is dropped into the concentration adjusting tank. Is controlled to be constant.

The developer whose concentration has been adjusted in the concentration adjusting tank is once sent to the buffer tank by the pump 2. By making the buffer tank sufficiently large, it is possible to stably supply a developing solution having a printable concentration even in continuous printing. The developer is supplied from this buffer tank to the developer support by another pump 1. The pump 2 is not driven while the concentration of the concentration adjusting tank is being adjusted, that is, while the high-concentration developer or carrier liquid dropping pump is being driven. As a result, the concentration of the developer in the buffer tank is always kept constant, so that the developer is always supplied from the buffer tank to the developer support regardless of the adjustment of the developer in the adjusting tank. be able to.

The developing solution sent to the developing device having the developing solution support collects in the developing solution pool in the developing device and is pumped up from there by a roller (not shown) to have a predetermined thickness on the developing solution support. It is applied with. Excess developer in thin layer formation passes through the developer pool as it is and is returned to the buffer tank. Since the concentration of this developer is the same as that at the time of supply, it is not necessary to adjust the concentration. For this reason, the excessively supplied developer is returned directly to the buffer tank instead of the adjusting tank to prevent wasteful work.

Further, the toner is circulated between the developer support and the buffer tank to prevent the toner from sticking. The flow path diameter of the path for returning from the developer support to the buffer tank is changed from the buffer tank to the developer support. By making it larger than the flow path diameter of
The developer can be smoothly circulated by only the pump 1 from the buffer tank.

The thin developer layer formed on the developer support is 5
With a thickness of about 20 μm, all solids contained in this thin developer layer move to the image area on the image carrier to contribute to image formation. In the non-image area, the developer on the developer support is recovered by the recovery section and returned to the toner recycling device. Then, the developing solution returned to the toner recycling device is adjusted to a predetermined concentration in the concentration adjusting tank, sent to the buffer tank, and then supplied again to the developing solution support. The transfer residual developer recovered from the image bearing member is mostly a carrier liquid and has a small solid content, and since foreign matter such as paper dust may be mixed in, the solid content contained in the developer is large. Can be separated and only the carrier liquid can be returned to the developer concentration adjusting tank.

A liquid amount sensor B and a full sensor D are installed in the buffer tank. At the time of initializing the apparatus, a step of generating a developing solution having a concentration suitable for printing is performed until the buffer tank becomes full, and the value of the liquid amount sensor B when full is stored in the process. The liquid level sensor B can detect the rise and fall of the liquid level. By combining this with the full sensor D, it is possible to determine the empty state by the change amount from the time when the buffer tank is full, and the sensor of the empty only There is no need to prepare.

A liquid amount sensor A and an empty sensor C are installed in the concentration adjusting tank. Since the adjusting tank of the apparatus in the shipping state is empty, the value of the liquid amount sensor A before the start of introducing the high-concentration developing solution or the carrier solution into the adjusting tank is stored as the empty value. Since it is possible to determine whether the tank is full or not based on the amount of change from the value of the liquid amount sensor A when empty, the full sensor is omitted.

When it is determined that the concentration adjusting tank is full and the concentration of the developing solution in the concentration adjusting tank is not suitable for printing at that time, in order to perform further concentration adjustment, the inside of the concentration adjusting tank is adjusted. Discard a predetermined amount of developer. At this time, since the toner that exceeds the liquid level rise due to the developer collected from the developing device and the image carrier must be discarded, the output of the waste pump 5 is changed so that the liquid level sensor indicates the drop of the liquid level. To do.

Further, it is provided with means for judging the driving state of each pump, and it is possible to detect whether or not the pump is in the true driving state while the control side is driving. For example, there is a method of attaching an encoder plate coaxially with the rotation axis of the pump and detecting with a sensor to see if the clock can be detected.

Then, it is possible to make a matrix of the change of the liquid amount and the operating state of the pump from the drive state judgment and the change state of the liquid amount, and monitor whether or not there is a contradiction. This matrix is as illustrated in FIG. As shown in the upper column of the matrix in FIG. 2, when the pump 2 is driven, the value of the buffer tank liquid amount sensor is decreasing, or when it is unchanged, if the pump 1 is stopped,
It is abnormal. Further, when the pump 2 is driven, if the liquid volume sensor in the adjusting tank is rising or is unchanged, both are abnormal. Further, as shown in the lower column of the matrix of FIG. 2, when the pump 2 is not driven, the buffer tank liquid amount sensor is rising or falling, and when the pump 1 is stopped, the pump 1 is stopped. It is abnormal.

As illustrated here, when a contradiction occurs, the mechanical engine can immediately stop the adjustment and issue an alarm. Further, since the flow rate of the path connecting between each tank and the developer support can be determined based on the variation state of the liquid quantity, feedback control can be applied to the pump drive in such a manner as to keep it constant.

The liquid quantity sensor to be used here is one that reads the change in resistance of the variable resistors connected with the up and down movement of the float, or as shown in FIG. A slit-shaped triangular slit whose width changes linearly with the reading of output changes with a horseshoe-shaped transmissive optical sensor, or, as shown in FIG. It is possible to use a reflection plate in which a slender triangular pattern in which the reflection density changes linearly is formed and whose output is read by a reflection type optical sensor.

Since the developer is sent from the buffer tank to the developing device during printing by the control of the toner recycling device, the buffer tank and the concentration adjusting tank are agitated and the concentration of the developing solution is adjusted even during printing standby. This density adjustment is performed only during printing and when the standby level is shallow. When the standby level is shallow, it means the state level that is relatively easy to return to the operating state among the standby levels. That is, after a lapse of a certain time after printing is completed, the standby state is entered (shallow standby level), but at this time, the manufacturing work of the developing solution having a concentration suitable for printing by the concentration adjustment is continued, and after a further lapse of a certain period of time, a deep standby level ( When it goes to the sleep state), the density adjustment is finished.

The duration of the standby state accompanied by the adjustment of the concentration of the developing solution is based on the number of printed sheets immediately before being grasped by the mechanical engine, and the grasped value of the capacity until the tank is full by the liquid amount sensor of the buffer tank. You can decide. That is, the adjusting operation of the concentration adjusting tank continues until a certain time after printing is completed,
The device can be stopped in the sleep state or the power saving state, and the time until the sleep state or the power saving state can be changed by the volume until the full tank state determined by the liquid amount sensor of the adjusting tank. Further, the time until the sleep or the transition to the power saving state can be set according to the amount of the consumed developer which changes depending on the number of printed sheets immediately before.

[0035]

According to the present invention, the buffer tank is provided in addition to the density adjusting tank so that only the toner adjusted to the optimum print density can be put in the buffer tank, so that the optimum density is always maintained even in the continuous printing. Only the toner can be continuously supplied.

Further, in the present invention, it is necessary to dispose a flow rate sensor or the like between the tanks or between the developer support and the tank by devising a method for detecting the liquid quantity and the change in the liquid quantity in each tank. It is possible to provide a toner recycling control system having a simple structure.

Further, according to the present invention, since the highly viscous liquid developer is recycled in the apparatus, it is possible to constantly supply the toner having a relatively simple structure and a concentration suitable for printing.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a toner recycling apparatus to which the present invention can be applied.

FIG. 2 is a diagram exemplifying a matrix of a change in liquid amount and a pump operating state.

FIG. 3 is a diagram showing an example of a liquid amount sensor configuration.

FIG. 4 is a diagram showing another example of a liquid amount sensor configuration.

Continued front page    (72) Inventor Shigenori Uesugi             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Yoshiro Kawamoto             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor, Yasuichi Takeda             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Koichi Yoshida             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Yoshiaki Fujimoto             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Moriki             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Masanobu Motoe             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. (72) Inventor Yasuhiko Kishimoto             At 98 Unoke-nu, Unoki-cho, Kawakita-gun, Ishikawa Prefecture             2 PFU Co., Ltd. F term (reference) 2H027 DA38 DD01 DD02 DE02 DE03                       DE04 DE07 DE10 EA06 EC06                       ED08 ED10 EE01 EE03 EE07                       EF01 EF13 EF16                 2H030 AD03 BB27 BB36 BB38 BB42                 2H074 AA03 BB02 BB04 BB14 BB32                       BB50 BB54 BB72 CC03 CC04                       CC12 CC13 CC15 CC23 CC24                       CC26 CC33 CC62 EE07                 2H134 GA01 GB03 JC01 JC02 JC04                       JC07 KA22 KA25 KG03 KH17                       KJ02

Claims (23)

[Claims] 1. A developer residual concentration developer from a developer support for forming and developing a thin layer of a highly viscous liquid developer and a transfer residual developer from an image bearing member are collected to adjust the concentration of the developer. After carrying out, in the toner recycling control system of the electrophotographic apparatus which supplies the developing solution again to the developing solution support, the collected developing solution is stored and the concentrated developing solution and the carrier solution are supplied to adjust the concentration of the developing solution. An adjusting tank and a liquid developer whose concentration is adjusted in the concentration adjusting tank are conveyed,
A toner recycle control system for an electrophotographic apparatus, comprising a buffer tank for storing the liquid developer, and supplying a liquid developer having an appropriate concentration to the developer support from the buffer tank. 2. When a layer is formed on the developing solution support with the supplied liquid developing solution, excess liquid developing solution is returned to the buffer tank as it is and recovered from the developing solution support after development. 2. The toner recycle control system for an electrophotographic apparatus according to claim 1, wherein the residual developing solution and the residual developing solution recovered after being transferred from the image bearing member are provided in respective circulation paths to be returned to the concentration adjusting tank. . 3. A thin layer forming body for forming a thin layer on the surface of the liquid developing solution in the concentration adjusting tank, and detecting the reflection density of the thin layer of the developing solution formed on the thin layer forming body. 3. The toner recycling control system for an electrophotographic apparatus according to claim 1, wherein the concentration of the liquid developer is detected by the method. 4. The toner recycling control system for an electrophotographic apparatus according to claim 3, wherein the thin layer forming body is composed of a pair of rollers, and the density of the final stage roller is detected by a reflection sensor. 5. The toner recycling control system for an electrophotographic apparatus according to claim 4, wherein a pattern roller is used as a roller at a front stage for supplying the developing solution to the final stage roller to regulate a coating amount of the developing solution. 6. The toner recycling control method for an electrophotographic apparatus according to claim 3, wherein the thickness of the thin developer layer for detecting the reflection density of the developer is in the range of 5 to 30 μm. 7. The residual transfer developer recovered from the image carrier separates solids contained in the developer and returns only the carrier liquid to the concentration adjusting tank.
Alternatively, the toner recycling control method of the electrophotographic apparatus according to the item 2. 8. A multi-color printing apparatus is provided with a developing device including the developing solution support for each of a plurality of colors, a concentrated developing container is provided for each color, and a common carrier liquid container is provided. 3. The toner recycling control system for an electrophotographic apparatus according to claim 1, wherein the carrier liquid is supplied from the carrier liquid container to the concentration adjusting tank for each color. 9. The concentration of the concentration-adjusted liquid developer is 5%.
4. The toner recycling control method for an electrophotographic apparatus according to claim 3, wherein the predetermined density is in the range of .about.30%. 10. A liquid amount sensor is attached to each of the buffer tank and the concentration adjusting tank, and a mechanism for determining a driving state of a pump is provided to monitor a matrix of a liquid amount change and a pump driving state. 2. The toner recycling control system for an electrophotographic apparatus according to claim 1, wherein an abnormality relating to pump driving is detected without installing a flow rate sensor. 11. The electrophotographic apparatus according to claim 10, wherein the pump drive is maintained at a constant flow rate by feeding back the pump drive based on the amount of change in the liquid amount detected by the liquid amount sensor. Toner recycling control method. 12. The toner of an electrophotographic apparatus according to claim 10, wherein the liquid amount sensor is configured to read the output of a variable resistor connected with the vertical movement of a float installed on the liquid surface. Recycle control method. 13. The liquid amount sensor is configured so that a transmission type optical sensor reads a triangular slit having a slit width that linearly changes with a vertical movement of a float installed on the liquid surface. Alternatively, the toner recycling control method for the electrophotographic apparatus according to Item 11. 14. The liquid amount sensor has a structure in which a reflection plate formed with a triangular pattern in which a reflection density moving linearly with a vertical movement of a float installed on the liquid surface changes linearly is read by a reflection type optical sensor. 12. The toner recycling control system for an electrophotographic apparatus according to claim 10 or 11. 15. The buffer tank is provided with a full sensor for detecting a full tank in addition to the liquid amount sensor, and the empty state of the buffer tank is determined by using a change amount from when the buffer tank is full. The toner recycle control method for an electrophotographic apparatus according to claim 10 or 11, configured to perform the above. 16. When the apparatus is turned on, an operation of adjusting and supplying a developing solution having a concentration suitable for printing is performed until the buffer tank is full, and the liquid amount sensor of the full tank The toner recycling control method for an electrophotographic apparatus according to claim 15, wherein the value is acquired and held. 17. A configuration in which an empty sensor is provided in addition to the liquid amount sensor in the concentration adjusting tank, and the full state of the concentration adjusting tank is determined using the amount of change from the empty state of the concentration adjusting tank. 12. The toner recycling control system for an electrophotographic apparatus according to claim 10 or 11. 18. A structure for acquiring and holding a value of a liquid amount sensor in a state before starting to drip a high-concentration developing solution or a carrier solution into the concentration adjusting tank before the initial operation of the apparatus. The toner recycling control method for the electrophotographic apparatus according to 1. 19. When it is determined that the concentration adjusting tank is full and that the concentration of the developer in the concentration adjusting tank is not suitable for printing at that time, the developer in the concentration adjusting tank is 18. The toner recycling control method for an electrophotographic apparatus according to claim 17, wherein the method is configured to be discarded. 20. To discard the toner that exceeds the liquid level rise due to the developer collected from the developer support and the image carrier, the liquid discharge sensor of the waste pump is arranged so that the liquid level sensor indicates the drop of the liquid level. A structure in which the output is variable.
9. A toner recycling control method for an electrophotographic apparatus according to item 9. 21. The adjusting operation of the concentration adjusting tank is continued until a certain time after printing is finished, and is stopped in a sleep mode or a power saving state of the apparatus, and the time until the sleep state or the power saving state is changed is set in the concentration adjusting tank. The toner recycling control method for an electrophotographic apparatus according to claim 10, wherein the toner recycling control method is changed according to the volume up to a full state determined by the liquid amount sensor. 22. The adjusting operation of the density adjusting tank is continued until a certain time after the printing is finished, is stopped in the apparatus sleep state or the power saving state, and the time until the sleep state or the power saving state is changed varies depending on the immediately preceding number of printed sheets. 12. The toner recycling control system for an electrophotographic apparatus according to claim 10, wherein the setting is made according to the amount of the developing solution. 23. Toner is provided without a pump on the return path by making the flow path diameter of the return path from the developer support to the buffer tank larger than the flow path diameter from the buffer tank to the developer support. 3. The toner recycling control system for an electrophotographic apparatus according to claim 2, wherein the good circulation of the toner is possible.