JP2930834B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer comprising a toner and a carrier for visualizing an electrostatic latent image on the surface of a photoreceptor in an electrophotographic apparatus such as a copying machine. The present invention relates to a developing device for supplying a surface.

[0002]

2. Description of the Related Art For example, in a dry copying machine, a developing device for visualizing (developing) an electrostatic latent image on a photoreceptor surface with a two-component developer comprising a carrier and a toner is often used. In such a developing device, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing device. Therefore, as the stirring frequency of the carrier stirred with the toner in the developing device increases,
A situation such as peeling of the resin coat layer on the surface or sticking of the toner to the surface occurs to cause deterioration, and as a result, the charging performance of the developer gradually decreases.

Therefore, apart from replenishment of toner consumed by the developing operation, a device in which the carrier is replenished little by little into the developing device so as to suppress the deterioration of the charging performance is disclosed, for example, in Japanese Patent Publication No. 2-15991. Official Gazette and Shoko 6
No. 0-2596. In the apparatus, the developer in the developer tank that has become excessive due to the replenishment of the carrier overflows from a developer overflow port provided on the wall surface of the developer tank, is discharged, and is collected in a developer collection container. By repeating such replenishment / discharge sequentially, the deteriorated developer in the developing tank is replaced with newly supplied toner and carrier, whereby
The charging performance is maintained, and a decrease in copy image quality is suppressed.

[0004]

However, in the above-mentioned apparatus, since the depleted developer in the developing tank is discharged by overflow from a developer overflow on the wall of the developing tank, it is newly supplied. There is a problem that the replacement ratio with fresh developer is not maintained as intended, so that the charging performance fluctuates and the copy image quality deteriorates.
For example, when copying of a document having a high document density is repeated, the amount of toner consumption increases, and at this time, the total amount of the developer in the developing tank decreases. Even if the carrier is supplied in this state, the amount of the developer does not reach the overflow of the developer, so that the discharge due to the overflow does not occur. As described above, in the spontaneous discharge structure due to the overflow, the discharge as intended is unlikely to occur, so that the deterioration of the copy image quality due to the deterioration of the charging performance cannot be sufficiently compensated.

On the other hand, when the carrier is replenished in a state in which the amount of the developer in the developing device is large, the carrier is likely to be immediately discharged due to overflow. There is also a problem that the replacement efficiency is lowered because the replacement is not performed as intended, and an excessive supply of the carrier is required to compensate for this, and the consumption of the entire developer increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to replenish a carrier developer containing a carrier and to discharge the developer in a developing tank corresponding to the replenishment. And more reliably can be performed,
As a result, it is possible to provide a developing device capable of suppressing deterioration in charging performance and maintaining good image quality, and improving replacement efficiency by repeating replenishment and discharge, thereby reducing developer consumption. is there.

[0007]

[0008]

[0009]

Means for Solving the Problems To solve the above problems,
In order, a developing device of the invention according to claim 1, in the developing tank for containing a developer comprising a toner and a carrier, freely developing roller are each rotated supplies stirrer and developer stirring the developer to the photoreceptor A developing device in which a carrier developer containing a carrier is sequentially supplied to the developing tank from a developer replenishing section, and the developer in the developing tank is discharged from a discharging section formed in the developing tank. A discharge opening is formed in the discharge portion, and an opening / closing lid driven by driving means to open and close the discharge opening is provided.
A replenishing unit that controls the developer replenishing unit and the driving unit such that the total amount of the developer replaced by the replenishment from the developer replenishing unit and the discharge of the developer through the discharge opening is sequentially increased every predetermined number of times. -It is characterized by having emission control means.

[0010]

Further, the developing device of the invention according to claim 2 is
A carrier containing a carrier is provided in a developing tank containing a developer comprising a toner and a carrier, and a rotary driving member for a stirrer for stirring the developer and a developing roller for supplying the developer to the photoreceptor are rotatably provided. In the developing device in which the developer is sequentially replenished from the developer replenishing section to the developing tank, while the developer in the developing tank is discharged from a discharging section formed in the developing tank, a discharging opening is formed in the discharging section. And an opening / closing lid which is driven by a driving means to open / close the discharge opening, while supplying the developer in the developer tank by replenishment from the developer supply unit and discharge of the developer through the discharge opening. A cumulative driving time reference control unit for controlling the developer supply unit and the driving unit such that a repetitive operation for gradually replacing the developer is performed based on the cumulative driving time of the rotary driving unit. It is characterized in that.

[0012]

[0013]

Further, the developing device according to the third aspect of the present invention,
An agitator for agitating the developer and a developing roller for supplying the developer to the photoreceptor are rotatably provided in a developing tank for storing the developer including the toner and the carrier, and the carrier developer containing the carrier contains the developer. In the developing device in which the developer in the developing tank is discharged from the discharging section formed in the developing tank while the developer is sequentially supplied from the replenishing section to the developing tank, a discharging opening is formed in the discharging section. An opening / closing lid driven by a driving unit is provided to open and close the discharge opening. On the other hand, during each supply operation of the carrier developer to the developing tank and each discharging operation of the developer from the developing tank, the number of image forming operations is limited. The preset use limit of the developer shown in the figure is defined as the developer service life, and the interval between the next replenishment and discharge processing of the developer indicated by the number of image forming operations is defined as the developer replacement interval. Sometimes, the developer replenishing unit and the driving unit are configured such that the amount of developer in the developer tank / (developer life / developer replacement interval) or more is supplied to the developer tank and discharged from the developer tank. A supply / discharge control means for controlling the means.

Further, the developing device of the invention according to claim 4 is
An agitator for agitating the developer and a developing roller for supplying the developer to the photoreceptor are rotatably provided in a developing tank for storing the developer including the toner and the carrier, and the carrier developer containing the carrier contains the developer. In the developing device in which the developer in the developing tank is discharged from the discharging section formed in the developing tank while the developer is sequentially supplied from the replenishing section to the developing tank, a discharging opening is formed in the discharging section. While an opening / closing lid driven by a driving means is provided to open and close the discharge opening, the developer replenishing unit replenishes a carrier developer having an average life shorter than the developer stored in the developing tank. Yes, so that the supply operation of the carrier developer to the developer tank and the discharge operation of the developer from the developer tank are performed based on the average life of the carrier developer supplied from the developer supply unit. It is characterized in that it comprises a supply and discharge control means for controlling the developer supply unit and driving means of the serial.

[0016] The developing apparatus of the invention of claim 5, wherein the
An agitator for agitating the developer and a developing roller for supplying the developer to the photoreceptor are rotatably provided in a developing tank for storing the developer including the toner and the carrier, and the carrier developer containing the carrier contains the developer. In the developing device in which the developer in the developing tank is discharged from the discharging section formed in the developing tank while the developer is sequentially supplied from the replenishing section to the developing tank, a discharging opening is formed in the discharging section. While an opening / closing lid driven by a driving unit is provided to open and close the discharge opening, at least a mode selection unit for selecting an image quality improvement mode and a developer saving mode, and a supply amount of the carrier developer to the developing tank and The discharge amount of the developer from the developing tank becomes relatively large when the image quality improvement mode is selected, and becomes relatively small when the developer saving mode is selected. It is characterized in that it comprises a supply and discharge control means for controlling the developer supply unit and a driving unit so.

[0017] The developing apparatus of the invention of claim 6 wherein the
The developing device according to any one of claims 1 to 5, wherein the discharge opening is formed in a wall of the developing tank at a portion where the developer stays in the developing tank.

[0018]

[0019]

[0020]

[Action] In the configuration according to the first aspect, during the early deterioration of the developer that has been contained in the developing tank is not progressed so much in the beginning, the amount of replenishment and discharge are each less, thereby sufficient developer While the developer which can be used for the above is prevented from being wastefully discharged, the amount of replenishment / discharge is gradually increased as the deterioration progresses, and the deterioration of the charging performance in the developing tank is suppressed. Therefore, good image quality can be maintained more reliably. Further, as described above, the replacement efficiency is improved by changing the replacement amount in accordance with the degree of progress of the deterioration, whereby the consumption amount of the entire developer can be reduced.

[0021]

According to the second aspect of the present invention , based on the accumulated driving time of a rotary driving member such as a stirrer in a developing tank which is more directly related to the deterioration of the stored developer, Since supply and discharge are performed, for example, power supply O
Even in the case where the preliminary rotation of the rotary driving member during the warm-up at the time of N has a greater effect on the deterioration of the developer, the replacement process suitable for the progress of the deterioration of the developer can be performed. For this reason, it is possible to more reliably maintain the charging performance and reliably maintain good image quality.

[0023]

[0024]

According to the third aspect of the present invention, the replenishment amount and the discharge amount of the developer, that is, the replacement amount of the developer in the developing tank when the replenishment amount and the discharge amount are equal are set to what amount. As a result of examining whether a reduction in the charging performance can be suppressed, a preset use limit of the developer, which is indicated by the number of image forming operations, is defined as a developer service life, and is indicated by the number of image forming operations. When the interval between the next processing of the replenishment and discharge processing of the developer is defined as the developer replacement interval, the developer amount in the developer tank / (developer life / developer replacement interval) or more is used as the developer tank. It was found that it was only necessary to replenish the toner and discharge it from the developing tank. Therefore, in each replenishing and discharging operation of the developer, by controlling the developer replenishing unit and the driving means so that the above amount of replenishing and discharging is performed, a decrease in the charging performance of the developer is suppressed,
Good image quality can be reliably maintained.

According to the fourth aspect of the present invention, a carrier developer having an average life shorter than the developer stored in the developer tank is supplied from the developer supply section to the developer tank, and the carrier is supplied to the developer tank. Since the replenishing operation of the developer and the discharging operation of the developer from the developing tank are performed based on the average life of the carrier developer supplied from the developer replenishing section, the developer in the developing tank approaches the average life. It is possible to avoid a situation in which the developer is continuously used in a state where the developer is used, that is, in a state where the function as the developer is considerably lower than the initial use. As a result, deterioration of the initial image quality can be prevented, and good image quality can be reliably maintained.

According to a fifth aspect of the present invention, when the image quality improving mode is selected by the mode selecting means,
The amount of carrier developer supplied to the developing tank and the amount of developer discharged from the developing tank become relatively large, and this reduces the degree of deterioration of the developer in the developing tank. Obtainable. On the other hand, when the developer saving mode is selected by the mode selection means, the replenishing amount of the carrier developer to the developing tank and the discharging amount of the developer from the developing tank become relatively small, whereby the image quality improving mode is selected. Although the degree of deterioration of the developer in the developing tank increases and the image relatively decreases, the consumption of the carrier developer can be suppressed. As described above, in the present developing apparatus, an operation in which image quality is prioritized over economy and an operation in which economy is prioritized over image quality can be selected according to a user's request.

According to the configuration of claim 6 , in addition to the operation of the configuration of any one of claims 1 to 5 ,
When the discharge opening is opened by the opening operation of the open / close lid,
The deteriorated developer remaining without contributing to the developing operation in the developing tank can be reliably discharged, and the new developer and the deteriorated developer can be efficiently replaced. Therefore, the charging performance of the developer in the developing tank is maintained in a good state, whereby a good image quality can be maintained.

[0029]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG.
In a copying machine configured by applying the present invention, a document table 1 is provided on the upper surface, and an exposure optical system 2 is provided below the document table 1. The exposure optical system 2 includes a light source lamp 3 that scans a document (not shown) placed on the document table 1 while irradiating the document with light, and a photoconductor 4 that reflects light reflected from the document.
, And a lens unit 6 arranged in the optical path of the reflected light.

On the outer periphery of the photoconductor 4, a charging charger 7 for charging the surface to a predetermined potential, an inter-image eraser (not shown), and a developing device for developing an electrostatic latent image formed on the surface of the photoconductor 4 8, a transfer charger 9 for transferring a toner image on the surface of the photoreceptor 4 to a sheet, a cleaning device 10 for collecting residual toner on the surface of the photoreceptor 4, a static eliminator (not shown), and the like are provided. A timing roller 11, a feeding roller 12, a paper feed cassette 13, and a paper feed roller 14 for supplying paper at a predetermined timing are provided on the paper input side with respect to the photoreceptor 4, and on the paper output side with respect to the photoreceptor 4. Is provided with a fixing device 15 for fixing the toner image transferred onto the sheet to the sheet.

As shown in FIG. 3, the developing device 8 has a container-like developing tank 16, in which a developing roller 17 composed of a magnet roller and a stirrer 18 are provided.
Are rotatably arranged. The developer contained in the developing tank 16 is composed of a carrier and a toner, and the carrier composed of a magnetic material has a resin coat layer on its surface for suppressing adhesion of the toner. When the carrier and the toner are agitated by the agitator 18, the toner is frictionally charged. The developing roller 17 attracts the carrier by magnetic force, forms a magnetic brush, and conveys the toner. The toner adhered to the carrier by Coulomb force is supplied to the photoconductor 4 and is attracted to the electrostatic latent image on the photoconductor 4. Then, development is performed. The height of the ears of the magnetic brush is regulated by the doctor 19.

An opening for supplying a developer is formed in the upper wall portion 16a of the developing tank 16, and a developer supply unit (developer supplying portion) 20 is fitted into the opening for supplying the developer from above. The inside of the developer supply unit 20 is partitioned into two chambers, a toner storage chamber 20a and a carrier developer storage chamber 20b. In one toner storage chamber 20a, toner is stored, and in the other carrier developer storage chamber 20b, a developer consisting of only a carrier or a developer in which toner is mixed with a carrier at a predetermined ratio (hereinafter, referred to as carrier) is used. Developer).

A toner supply roller 21 and a carrier developer supply roller 22 are provided at the bottom of each of the storage chambers 20a and 20b, respectively. When the carrier developer supply roller 22 is driven to rotate, the carrier developer in the carrier developer storage chamber 20b flows down by an amount corresponding to the driving time of each roller 21/22. And supplied into the developing tank 16.

On the other hand, on the bottom wall portion 16b of the developing tank 16, a container-like collection container 23 having an open upper surface is detachably attached from below. Then, on the bottom wall portion 16b,
A discharge opening 24 for vertically communicating the inside of the developing tank 16 with the inside of the collection container 23 is formed, and an opening / closing mechanism 25 for opening and closing the discharge opening 24 is provided along the lower surface of the bottom wall 16b.

As shown in FIGS. 1 (a) and 1 (b), the opening / closing mechanism 25 includes a flat opening / closing lid 26 slidably disposed along the lower surface of the bottom wall 16b, and the opening / closing lid 26. Guide plates 27 provided on both sides of the opening / closing lid 26 so as to guide the sliding operation of the opening / closing lid 26, and a discharge solenoid (driving means) 28 having a tip of a plunger 28a connected to the opening / closing lid 26. Made up of When the discharge solenoid 28 is not energized (OFF), the plunger 2
8a is held in the advanced position, whereby the opening / closing lid 2
6 is held in a closed state that covers the discharge opening 24 from below. On the other hand, when the discharge solenoid 28 is energized (ON), the plunger 28a is retracted, whereby the opening / closing lid 26 is opened.
Is retracted from the position covering the discharge opening 24 and the discharge opening 24
Switches to the open state. In this open state, the developer in the developing tank 16 flows down through the discharge opening 24 into the collection container 23 by its own weight, and is discharged from the developing tank 16.

Next, a copying operation in the copying machine having the above configuration will be described. Power switch (not shown) is ON
Then, a warm-up process is performed first. After this is completed, a copy start switch 31 described later
Is turned on, the original placed on the original placing table 1 is scanned by the light source lamp 3 of the exposure optical system 2. The light reflected from the original at this time is irradiated on the photoconductor 4 via the reflecting mirrors 5 and the lens unit 6, and an electrostatic latent image is formed on the surface of the photoconductor 4 charged to a predetermined potential by the charging charger 7. It is formed. Next, this electrostatic latent image is developed with toner supplied from the developing device 8. The toner image on the surface of the photoconductor 4 is transferred by the transfer charger 9 to the sheet cassette 13.
Is transferred to a sheet supplied from the printer, and is thermally fixed on the sheet by the fixing device 15. As a result, a copy image corresponding to the document image is formed on the sheet.

In order to control such a series of copying operations, as shown in FIG. 4, a control device 32 including a microcomputer is provided in the copying machine. An ON operation signal 31 is input. Further, a copy counter 33 for counting the cumulative number of copying operations is further provided, and this count value (hereinafter, referred to as a copy count value) n is also input to the control device 32.

When the copying operation as described above is repeated, the toner in the developer contained in the developing tank 16 of the developing device 8 is gradually consumed, and the ratio of the toner to the carrier, that is, the toner concentration decreases. To go. The toner concentration sensor 34 for detecting the change in the toner concentration is
The drive control of the toner replenishing roller 21 based on the toner density sensor 34 is performed by the control device 3.
2 further. That is, when it is detected that the detection signal from the toner density sensor 34 has fallen to the lower limit of the appropriate range required for development, the toner replenishing roller 2
1 is started. Thereby, the toner storage chamber 20a
Is supplied to the developing tank 16, and the toner concentration in the developing tank 16 increases. When it is detected that the toner concentration has reached the upper limit of the above-described appropriate range, the driving of the toner supply roller 21 is stopped. By such control, the toner concentration in the developing tank 16 is maintained within the above-mentioned appropriate range.

The toner replenished as described above is agitated with the developer in the developing tank 16 and is supplied to the photoreceptor 4 while being controlled to a fixed charge amount, and used for development. on the other hand,
Since the carrier in the developer does not decrease and is used repeatedly, stirring by the developing roller 17 and the stirrer 18
And gradually deteriorates due to contact with the photoconductor 4. When the carrier deteriorates in this manner, a predetermined charge amount cannot be given to the toner, and the image quality deteriorates.
Therefore, by newly replenishing the carrier in the developing tank 16 and replacing it with the deteriorated carrier in the developing tank 16,
A decrease in the charging performance as described above can be suppressed. For this purpose, the supply and discharge control for replenishing the carrier developer from the carrier developer storage chamber 20b and discharging the developer in the developing tank 16 is also performed by the control device 32. Therefore, the control device 32 also has a function as a supply / discharge control unit. Hereinafter, a control procedure when functioning as the supply / discharge control means will be described with reference to a flowchart of FIG.

First, every time copying is performed, the copy count value n of the copy counter 33 is compared with the set value switching count value n (i) (S1). This n (i) is obtained by setting in advance the cumulative number of copies for which the set values of a discharge cycle X _C , a discharge time t _XC , a replenishment cycle Y _C , a replenishment time t _YC, etc. to be described later are to be changed. A plurality of values of n (1) .n (2)... Are stored in a storage unit in the control device 32, and are sequentially read out in the process of S1 according to the parameter i. Further, the set value switching count value n (i) (i = 1,
2,...), The discharge cycle value X _C (i), the discharge time t _XC (i), the supply cycle value Y _C (i), and the supply time t _YC
(i) is stored as a data table.

In S1, when it is determined that the copy count value n has reached the set value switching count value n (i), each of X _C (i) and t _XC corresponding to n (i) at this time is determined. (i),
Y _C (i) and t _YC (i) are _defined as discharge cycle X _C and discharge time t.
A process of newly setting _XC , replenishment cycle Y _C , and replenishment time t _{YC instead} of the previous values is performed (S2), and 1 is added to the parameter i (S3).

Processing S1 for setting value switching as described above
After to S3, the above copy count value n, compared with the emission timing value M _X (S4), when n is determined that has reached M _X, ON the discharge solenoid 28
(S5). Thereby, the opening / closing lid 26 is moved from the closed position covering the discharge opening 24 to the open position, and the developing tank 1 is opened.
The discharge of the developer in 6 starts. At the same time, the counting of the discharge time monitoring timer is started, and the counting time t of this timer is measured.
_The developer is discharged until _X reaches the discharge time t _XC (S6). t _X to OFF the discharge solenoid 28 to reach t _XC (S7). As a result, the opening / closing lid 26 returns to the closed position covering the discharge opening 24, and the discharge of the developer is stopped. Then, the above discharge timing value M
The _X, performs the processing of adding the discharge cycle X _C (S
8), whereby the discharge timing value M _X are then updated to the cumulative number of copies value to perform the discharge of the developer.

[0043] After the discharge treatment as described above has been completed, or the copy count value n in step S4 when it does not reach the discharge timing value M _X is then compared n refill timing value M _Y (S9). While performing the processing returns to step S1 when the n has not reached M _Y, when n has reached the M _Y subsequently, the carrier developer supply roller 22 O
N (S10). Thus, the supply of the carrier developer in the carrier developer storage chamber 20b to the developing tank 16 is started. At the same time, the time of the replenishment time monitoring timer is started, and the time t _Y measured by the timer is determined by the replenishment time t.
Replenishment of carrier developer is continued until _YC is reached (S
11). When t _Y reaches t _YC , the supply of the carrier developer is stopped by turning off the carrier developer supply roller 22 (S12). Then, the above replenishing timing value M _Y, adding the replenishment cycle Y _C (S
13) Perform processing to return to S1. As a result, the supply timing value _MY is updated to the cumulative copy number value at which supply is to be performed next.

By repeating such control, every time copying is performed X _C times, the discharge solenoid 2
8 is driven for a time t _XC, and the amount of the developer corresponding to the drive time is discharged from the developing tank 16 to the collection container 23. Further, every time copying is performed Y _C times, the carrier developer supply roller 22 is driven for a time t _YC, and the amount of the carrier developer corresponding to the drive time is supplied to the developing tank 16. As described above, the replenishment of the carrier developer and the discharge of the developer in the developing tank 16 are repeated, so that the deteriorated developer in the developing tank 16 is sequentially replaced with fresh developer.

As described above, in the above embodiment, by opening the discharge opening 24 formed on the bottom wall surface of the developing tank 16, the developer existing on this bottom side portion is changed in shape and opening. The discharge is performed through the discharge opening 24 in an amount corresponding to time. Therefore, even when the total amount of the developer in the developing tank 16 fluctuates and the surface height changes, an amount of the developer corresponding to the driving of the opening / closing lid 26 by the discharging solenoid 28 is reliably discharged from the bottom side. be able to. For this reason, the replacement ratio when sequentially replacing the deteriorated developer in the developing tank 16 with fresh developer to be newly supplied is controlled as intended. As a result, the charging performance can be maintained substantially constant, and good copy image quality can be maintained.

Further, in the above description, the discharge cycle X _C , the discharge time t _XC , the supply cycle Y _C , and the supply time t _YC are changed whenever the copy count value n reaches the set value n (i). . When these set values are uniformly set, for example, as shown in FIG. 6B, the discharge cycle and the replenishment cycle are uniformly set to about 400 times, and each time the copy is repeated 400 times, In such control that discharge of the 50 g of the developer and replenishment of the same amount of the carrier developer are performed while the deterioration of the developer in the developing tank is not so advanced (period A in the figure). A large amount of developer that can sufficiently contribute to the development process is also discharged. When the cumulative number of copies increases and the degree of deterioration of the developer increases (period B in the figure), the replacement ratio between the deteriorated developer and the fresh developer becomes insufficient, and Therefore, there arises a problem that the charging performance is reduced and the copy image quality is gradually deteriorated.

Therefore, as described above, the discharge cycle X _C
Discharge time t _XC , supply cycle Y _C , supply time t
_By changing _YC sequentially according to an increase in the number of cumulative copies, the above-described problem is solved. For example, in FIG. 6A, for example, each of the initial values X _C (0) and Y _C (0) of the discharge cycle and the replenishment cycle is set to, for example, about 700 times. As the values t _XC (0) and t _YC (0), the discharge amount and the replenishment amount are each 10 g.
Then, the initial set value switching count value n (1) is set to, for example, 8000 times, and the discharge cycle and the supply cycle X _C (1) corresponding to the set value switching count value n (1) are set. ), Y _C (1) is about 400 times each, and the discharge time and the replenishment time t _XC (1) and t _YC (1) are the timing charts when the amount of discharge and replenishment amounts to 20 g each. Is shown.

In this case, 10 g of the carrier developer is supplied and discharged every 700 times until the cumulative number of times of copying reaches 8000 times. Each time the copying is performed 400 times, 20 g of the carrier developer is supplied and discharged. If the number of times exceeds 20,000, for example, 3
Switching is performed so that 30 g of replenishment / discharge is performed every 00 times.

As described above, as the cumulative number of copies increases, the frequency of replenishment and discharge or the amount of replenishment and discharge is increased as needed to reduce the mixing ratio between the deteriorated developer and the fresh developer. It is possible to keep it almost constant. As a result, a decrease in the charging performance of the developer in the developing tank 16 can be suppressed, and good image quality can be maintained for a long time. Further, the overall consumption of the developer for this can be minimized.

Embodiment 2 Another embodiment of the present invention is shown in FIG.
A description will be given with reference to FIG. For convenience of explanation,
Members having the same functions as those described in the above embodiment (hereinafter, referred to as the first embodiment) are denoted by the same reference numerals, and description thereof will be omitted.

In the first embodiment, the opening and closing mechanism 25 is provided on the bottom wall 16c of the developing tank 16,
For example, as shown in FIG.
Can also be provided on the side wall portion 16c. Stirrer 18
Is provided with a spiral stirring blade 18a around a central axis as shown in FIG. When the agitator 18 is rotated to agitate the toner and the carrier, the agitated developer is moved in the axial direction of the agitator 18 (arrow in FIG. (The direction indicated by C), and is sent to the developing roller 17 side. As a result, as shown in FIG.
As a result of the conveyance in the axial direction by 8, the bulge is formed along the side wall surface 16 c located at the tip end. That is, even when the total amount of the developer in the developing tank 16 is slightly reduced, the bottom side along the side wall surface 16c is a portion where the developer is always present. Therefore, even if the discharge opening 24 is formed in this portion as shown in FIG.
It is possible to reliably discharge the developer according to the opening operation of the opening / closing lid 26, and in particular, it is possible to discharge the developer more reliably by interlocking with the driving of the agitator 18.

[Embodiment 3] Still another embodiment of the present invention will be described with reference to FIGS. 1, 7 and 9 to 11. For convenience of explanation, members having the same functions as the members described in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the first embodiment, the process of replenishing the carrier developer and the process of discharging the developer in the developing tank 16 are performed when the copy count value n reaches a predetermined count value. It is configured to be. On the other hand, for example, while the developer discharge process is performed based on the copy count value n in the same manner as described above, the carrier developer replenishment process is synchronized with the toner replenishment based on the detection signal from the toner density sensor 34. It is also possible to adopt a control configuration or the like that performs this. For this reason, if the discharge process and the replenishment process are controlled independently of each other, the timing of simultaneously performing the replenishment and the discharge will inevitably occur. There is a possibility that fresh developer is immediately discharged.

Therefore, in this embodiment, it is assumed that the replenishing process of the carrier developer and the discharging process of the developer in the developing tank 16 are controlled independently of each other. The control configuration is such that it is not performed at the same time. That is, as shown in FIG.
2, a discharge processing control unit 41 for controlling the driving of the discharge solenoid 28 shown in FIG. 1 or 7 based on the count value n of the copy counter 33, FIG. 3 based on the detection signal
A supply processing control unit 42 for controlling the driving of the carrier developer supply roller 22 is provided independently of each other, and a monitoring control unit (simultaneous processing inhibition control means) 43 for exchanging signals with both control units 41 and 42. Is provided.

As shown in FIG. 10A, for example, as described above, the discharge processing control section 41 determines that it is time to perform the discharge processing when the copy count value n has reached the set value. (S21), and then sends a discharge processing start request signal to the monitoring control unit 43 (S21).
22). Thereafter, the process waits until a discharge processing permission signal is transmitted from the monitoring control unit 43 (S23). After receiving this signal, the discharge processing is executed in the same procedure as S5 to S8 in FIG. 5 (S24). ).

On the other hand, the replenishment processing control section 42
As shown in (b), for example, when the value detected by the toner density sensor 34 decreases to the lower limit of the appropriate range and the above-described toner replenishment is performed, this point in time is determined as the carrier developer replenishment timing. (S31). At this time, a replenishment processing start request signal is transmitted to the monitoring control unit 43 (S32), and the monitoring control unit 4
The process waits until a replenishment processing permission signal is transmitted from No. 3 (S33). After receiving this signal, S1 in FIG.
The supply process is executed in the same procedure as in steps S0 to S12 (S
34).

As shown in FIG. 11, the monitoring controller 43 first determines whether or not a supply signal start request signal has been generated by the supply processing controller 42 (S41). Is set to 1 in the replenishment processing timing flag F (S42).
Is set (S43). Next, it is determined whether or not a discharge start request signal is generated by the discharge processing control unit 41 (S4).
4). If this signal has been generated, a discharge processing permission signal is transmitted to the discharge processing control unit 41 (S45). As a result, the discharge process is executed by the discharge process control unit 41, and the process waits until the process is completed (S4).
6).

When the discharging process is completed, it is then determined whether the above F is 1 or 0 (S47).
On the other hand, when the value is 1, the replenishment processing permission signal is transmitted to the replenishment processing control unit 42 (S48). As a result, the replenishment process is executed by the replenishment process control unit 42, and after this process is completed (S4).
9) The process returns to S41. If it is determined in S44 that there is no discharge processing start request signal, the process proceeds to S47, and if there is a supply processing start request signal (when F = 1), replenishment is performed. Only processing is performed.

As described above, in the above-described control, when either the replenishment or the discharge is being executed, the request signal from the other is not received by the monitoring control unit 43, and the process being executed is completed. Waiting to do so generates a permission signal to the other. Therefore, the discharging process and the replenishing process are not performed at the same time, whereby the replenished fresh developer is not discharged immediately, so that a more efficient replacement state is maintained. Thereby, good copy image quality can be maintained.

In this embodiment, even when the replenishment process comes, it is not immediately executed, but it is determined whether or not the discharge process has come. When the timings substantially coincide with each other, control is performed so that the discharging process is performed with priority. In other words, when the timing at which the replenishment process is to be performed and the timing at which the discharge process is to be performed are substantially the same, when the replenishment process is performed first and the discharge process is subsequently performed, the newly replenished developer is almost completely discharged. It will be discharged in an unused state. Such a defect is eliminated by the above control.

[Embodiment 4] Still another embodiment of the present invention will be described with reference to FIGS. 1, 4, 7, 12, and 13. FIG. For convenience of explanation, members having the same functions as the members described in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the first embodiment, the cumulative number of copies n counted by the copy counter 33 is monitored, and this is set to a preset discharge / supply timing value M _X · M _Y.
The discharge / supply process is performed when the number of times has reached.

In a personal copying machine or the like in which the frequency of copying is relatively low and the power is turned on / off each time a small amount of copying is performed, a high-speed copying machine having a large number of copies after the power is once turned on is used. In comparison, the degree of deterioration of the developer becomes faster. This is because the pre-rotation of the developing roller 17 and the stirrer 18 is performed at the time of warm-up performed every time the power is turned on, and the deterioration of the developer due to the stirring of the toner and the carrier in the developing tank 16 during this time Is to be large. Therefore, in such a copying machine, when the cumulative number of copies is simply monitored and a predetermined count value is reached, when replenishing and discharging the carrier developer, an appropriate replacement state according to the degree of deterioration is set. I ca n’t hold it,
The copied image deteriorates.

In this embodiment, the supply and discharge timing of the carrier developer is determined based on the accumulated driving time of the developing roller 17 or the stirrer 18 which is the rotary drive of the developing device 8. I have. FIG. 12 shows a specific example of the control by taking a developer discharging process as an example.
Is shown in this case, if the drive of the developing roller 17 at the time and the copying operation execution power ON is carried out, the accumulated drive time T _rot is read, whether the T _rot has reached the discharge cycle set time X _T It is determined whether or not it is (S51). When it is determined that X _T has been reached, the discharge solenoid 28 is set to O
N (S52), whereby the discharge of the developer in the developing tank 16 is started, and at the same time, the timer of the discharge time monitoring timer is started. The time t _X measured by this timer reaches the set time t _XC. The developer is discharged (S53). When t _X reaches the set time t _XC, by the OFF of the discharge solenoid 28 shown in FIG. 1 or FIG. 7 (S5
4), the discharge of the developer is stopped, and the above-described cumulative drive time T _rot is reset to 0 (S55), and the process returns to S51.

The above processing is configured to be performed by the control device 32 shown in FIG.
The control device 32 in this case is configured to also function as a cumulative drive time reference control unit. This control, as shown in FIG. 13, for example, every accumulated drive time of the developing roller 17 reaches X _T, the discharge opening 24 is actuated discharge solenoid 28 is opened for a time t _XC, this An amount of the developer corresponding to the opening time is discharged from the developing tank 16 to the collection container 23.

As described above, by monitoring the accumulated driving time of the developing roller 17 and replenishing the carrier developer and discharging the developer, especially in a personal copying machine or the like where the copying frequency is relatively low, the developing process is performed. Depending on the degree of degradation of the agent, a more suitable replacement is made, which makes it possible to maintain good copy image quality over a long period of time.

Embodiment 5 Still another embodiment of the present invention will be described below with reference to FIGS. 1, 3, 4, 5, 7, and 14. FIG. For convenience of explanation, members having the same functions as the members described in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the developing device of this embodiment, the developer is discharged from the developing tank 16 based on the copy count value n as in the developing device of the first embodiment. The developer is supplied from the tank 16. For this purpose, the control device 32 shown in FIG. 4 performs the control shown in FIG.

That is, as shown in FIG. 14, for example, when the copy count value n reaches the set value in the same manner as described above, when it is determined that the timing for performing the discharging process has been reached (S61), the processing shown in FIG. In the same procedure as S5 to S8, a discharge process is performed by operating the discharge solenoid 28 shown in FIG. 1 or FIG. 7 (S62). Next, when this discharge processing is completed (S63), S10 in FIG.
The replenishment process by the operation of the carrier developer replenishment roller 22 shown in FIG.
4). Thereafter, when this replenishment processing is completed (S65),
It returns to S61.

In the above control, the replenished fresh developer is not discharged immediately, so that a more efficient replacement state is maintained and the consumption of the developer is reduced. At the same time, good copy image quality can be maintained.

In the case where the discharge of the developer and the supply control of the carrier developer are not performed as described above, in order to prevent the replenished fresh developer from being discharged immediately, for example, The replenishment position of the carrier developer and the formation of the discharge opening 24, such as setting the supply position of the carrier developer from the developer supply unit 20 at one end of the developing tank 16 and forming the discharge opening 24 at the other end. It is necessary to limit the position. On the other hand, when the discharge of the developer and the supply control of the carrier developer are performed as described above, the discharge position of the carrier developer and the formation position of the discharge opening 24 are not limited. Can be prevented. Therefore, the position of the developer supply unit 20 and the collection container 23 and the like can be set relatively freely, and the size and simplification of the developing device can be achieved.

[Embodiment 6] Still another embodiment of the present invention will be described below with reference to FIGS. 1 to 4, FIG. 7, FIG. 15, and FIG. For convenience of explanation, means having the same functions as the means shown in the drawings of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the developing device of this embodiment, the developing tank 1
In the same manner as in the developing device of the first embodiment, the supply of the carrier developer No. 6 is performed based on the copy count value n, and the discharge of the developer from the developing tank 16 reaches the predetermined copy count value n. This is performed at the time of front rotation or rear rotation.

In the above-described pre-rotation and post-rotation, the surface potential is made uniform in each part by performing the operations of charging and discharging the photosensitive member 4 shown in FIG. This is a process for preventing non-uniformity. The pre-rotation is performed before the image forming operation by the photoconductor 4 is started when the copy start switch 31 is operated, and the post-rotation is performed after the image forming operation by the photoconductor 4 is completed. Note that the post-rotation here does not cover the rotation of the photoconductor 4 for post-processing after each copy operation when a plurality of continuous copies are set, but after the set continuous copy. Only the post-rotation of the photoconductor 4 for processing is targeted. During the pre-rotation and post-rotation, the rotation of the developing roller 17 and the agitator 18 in the developing tank 16 is accompanied.

In order to perform the above operation, the control device 32 shown in FIG. 4 performs the control shown in FIG. That is, as shown in FIG. 15, for example, as described above, when the copy count value n reaches the set value, it is determined that it is time to perform the discharging process (S7).
4) Stand by until the pre-rotation or post-rotation is performed, and at the time of pre-rotation or post-rotation (S75), a discharge process is performed by operating the discharge solenoid 28 shown in FIG. 1 or 7 (S76 to S79). . Thereafter, when the copy count value n reaches the set value and it is determined that it is time to perform the replenishing process (S80), the discharging process is performed by the operation of the carrier developer replenishing roller 22 shown in FIG. (S81-S84), and returns to S71. FIG.
The operations of S71 to S74 and S76 to S84 in FIG. 5 are the same as the operations of S1 to S4 and S5 to S13 in FIG.

[0076] In the control described above, since the copy count value n to discharge treatment as close as possible to the timing set value M _X, before the rotation time and the time of the post-rotation may be appropriately conducted . In this case, for example, FIG.
As shown in, by copying the count value n has reached the set value M _X, when it is timing for the discharge processing is judged (S74), waits until the pre-rotation is performed, prior to the time of rotation (S91), a discharge process is executed.
On the other hand, in S74, the copy count value n is changed to the set value M _X
Even when not reached, when the copy count value n _P after the copy end next copy set number is a plurality exceeds the set value M _X (S92), the set value M _X
The difference between the copy count value n, when the less the difference between the set value M _X and the next copy count value n _P after copying is completed, i.e., when the _{M X -n ≦ n P -M X} (S93) At the time of the previous rotation with the current copy count value n (S94), the discharging process is executed. Further, in S93, when the difference between the set value M _X and the copy count value n, which is larger than the difference between the set value M _X and the next copy count value n _P after copying is completed, i.e., M _X -n> when n _P -M _X, (S95) during rotation after the copy is finished, it executes the discharge processing.
Therefore, in this control, for example, a 1000 set value M _X is a 999 current copy count n,
When the next copy set number is like a 100 sheets, during the post-rotation after the copying operation is completed, performs the discharge process at a significantly timing exceeds the set value M _X a copy count value n becomes 1099 sheets while that would, at the time the pre-rotation before said copying operation, it is possible to perform discharge process at the timing of approximately setpoint M _X.

According to the control for performing the developer discharging process during the pre-rotation or post-rotation as described above, the developer is stirred by the stirrer 18 when the developer in the developing tank 16 is discharged. The bias of the deteriorated developer in the inside 16 is prevented, and the required amount of the developer is efficiently discharged. Therefore, the replacement of the replenished carrier developer with the deteriorated developer is efficiently performed, and the consumption amount of the entire developer can be reduced. Further, at least the discharge of the developer from the developing tank 16 is performed at the time of pre-rotation or post-rotation not during the copying operation, so that the developing tank 16 during the copying operation is discharged.
, The change in the amount of developer is suppressed, and the change in image quality such as uneven density due to the change in the amount of developer is suppressed. Thereby, a decrease in image quality can be suppressed.

[Embodiment 7] Still another embodiment of the present invention is shown in FIGS. 1, 3 to 5, 7 and 17 to 22.
This will be described below based on For convenience of explanation, means having the same functions as the means shown in the drawings of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the developing device of this embodiment, each operation of replenishing the carrier developer from the developer supply unit 20 to the developing tank 16 and discharging each of the deteriorated developer from the developing tank 16 shown in FIG. At this time, in order to replace the developer in the developing tank 16 sequentially without using it in a state of being deteriorated beyond its life, a preset usage limit of the developer indicated by the copy count value is set to a predetermined value. The amount of developer in the developer tank / (developer use life / developer replacement interval) is defined as the life, and the interval between the next processing of the developer replenishment and discharge processing indicated by the copy count value is defined as the developer replacement interval. The above-mentioned amount of developer is supplied to the developing tank 16 and
The carrier developer replenishing roller 22 is discharged from the
The operation of the opening and closing mechanism 25 is controlled by the control device 32 shown in FIG.
Is controlled by the The replacement amount as described above is determined as follows.

When the carrier developer is supplied from the developer supply unit 20 to replace the deteriorated developer in the developing tank 16, the fresh developer is uniformly distributed in the developing tank 16 in a very short time. Assuming that, the life of the developer in the developing tank 16 is expressed by the following equation.

A = P {(1−α) − (1−α) ^{n / P + 1} } / α (1) where each symbol in the above formula is defined as follows. Each symbol uses a unit defined as a copy count value 1000 of 1 k.

A: Average life of the developer in the developing tank 16 (hereinafter referred to as developer life) α: Development in the developing tank 16 in such an amount that the deteriorated developer in the developing tank 16 is replaced with fresh developer. P: Copy count value at which the deteriorated developer in the developing tank 16 is replaced with fresh developer (hereinafter, referred to as a replacement interval) n: Copy count value Here, a method of deriving the above equation (1) will be described.
Note that the toner concentration of the developer in the developing tank 16 is constant.

First, assuming that the life of an arbitrary developer in the developing tank 16 is Li and the ratio of the developer having the life Li is βi, the developer life A is as follows.

[0084]

(Equation 1)

When the entire amount of the developer in the developing tank 16 is replaced with the developer of Mg at a rate of 100α% for each Pk, the change in the life of the developer in the developing tank 16 is expressed as shown in FIG. .
For example, the developer amount Mg is 500 g, and the developer replacement ratio α is 1
%, That is, 5 g, the change in the developer life is as shown in Table 1 below. Note that 0P (k) in FIG.
Indicates an initial state in which the developer in the developing tank 16 has not deteriorated at all, and 1P (k), 2P (k),.
The state in which the replacement of the third time,... Has been performed is shown. Also,
1, 2,... Of the leftmost column and the topmost row in Table 1.
.. Correspond to the above 1P (k), 2P (k),..., And the rows indicate the proportion of each developer present in the developing tank 16 at each replacement count.

Then, based on FIG. 17 and Table 1 above,
Calculating the developer life is as follows.

0P (k): A = (1 / M) (0P × M) 1P (k): A = (1 / M) ｛0P × Mα + 1P × M (1-α)｝ 2P (k): A = (1 / M) ｛0P × Mα + 1P × Mα (1-α) + 2P × M (1-α) ² ｝ ……………………………………………………… ... NP (k): A = (1 / M) ｛0P × Mα + 1P × Mα (1-α) + 2P × Mα (1-α) ² +... + (N−1) P × Mα (1-α) ^{N / P-1} + mP × M (1-α) ^{n /} PP (mP = n) (3) Accordingly, the expression (3) of the developer life A at nP (k) is represented by a general expression. When 0 <α ≦ 1, A = P {(1-α) − (1-α) ^{n / P + 1} } / α (1) When α = 0, A = n, and (1) is obtained.

Further, the process of deriving the equation (1) will be described in detail. From the equation (3), A = 1P.alpha. (1-.alpha.) + 2P.alpha. (1-.alpha.) ² + ... + (m- 1) P · α (1−α) ^{n / P−1} + mP (1−α) ^{n / P} Also, (1−α) A = 1P · α (1−α) ² + ... + (m− 2) P · α (1−α) ^{n / P−1} + (m−1) P · α (1−α) ^{n / P} + mP (1−α) ^{n / p + 1.} Pα (1-α) + Pα (1-α) ² + ... + Pα
(1−α) ^{n / P−1} + Pα (1−α) ^{n / P} (a) When α ≠ 0, A = P (1−α) + P (1−α) ² +... + P (1−α) ) ^{N / P-1} + P (1-α) ^{n / P} (1-α) A = P (1-α) ² +... + P (1-α) ^{n / p-1} + P (1-α) ^{n / P} + P (1−α) ^{n / P + 1} ... −αA = P ｛(1−α) − (1−α) ^{n / P + 1} ｝ A = P ｛(1−α) − (1−α) ^{n / P + 1} ｝ / α (1) (b) When α = 0 From Equation (3), A = n Note that from Equation (1), when α → 0, A = N.

The equation (1) obtained as described above shows the relationship between the developer replacement ratio and the replacement interval (copy count value n) and the life of the developer.

On the other hand, under the condition that the supply amount and the discharge amount of the developer in the developing tank 16 are equal, for example, the use life of the developer is 40 k, the replacement interval is 1 k, and the amount of the developer in the developing tank 16 is When the relationship between the copy count value n and the degree of deterioration of the developer in the developing tank 16 when the developer replacement amount was 12.5 g and the developer replacement amount was 100, the result shown in FIG. 18 was obtained. The results show that each developer replacement amount (50, 10
(0, 200), when the copy count value n becomes very large, the degree of deterioration of the developer in the developing tank 16 converges to a predetermined constant value. Thus, by determining the degree of deterioration of the developer in the developing tank 16, that is, the replacement amount of the developer so that the developer life A does not exceed the developer life, the life of the copier is equal to or longer than that. Can be given to the developer, and in this case, the following conditions are required.

A _L ≧ A (4) A _L : Service life of developer The following formula (5) can be derived from the above formulas (1) and (4).

[0092] than _{Mα ≧ M / (A L /} P) ......... (5) This equation (5), the developer-tank-contained developer amount / (developer service life / developer substituted interval) or more developer amount By supplying and discharging, the developer can have a life equal to or longer than the service life of the electrophotographic apparatus. With such a configuration, in the developing device of the present embodiment, a decrease in the charging performance of the developer is prevented, and good image quality can be maintained.

The structure of the developing device that performs the above operation is, for example, the developing device shown in the first embodiment.
The control device 32 shown in FIG. 4 performs the above-described replacement of the amount of the developer in each replacement operation with respect to the discharge solenoid 28 shown in FIG. 1 or 7 and the carrier developer supply roller 22 shown in FIG. Control to be performed.

Further, when the replacement interval of the developer in the developing tank 16 and the replacement amount were examined, the following results were obtained.

When a predetermined amount of the carrier developer is supplied to the developing tank 16 and the developer is discharged from the developing tank 16, if the developer replacement interval is lengthened, a large amount of the developer is replaced. Before and after the replacement of the developer, the developing characteristics of the developer in the developing tank 16 are significantly changed, and the image quality of the copied image is significantly changed. Further, the probability that the replenished developer is discharged at the time of discharge is increased, and the developing tank 16
The degree of deterioration of the internal developer tends to increase. In order to prevent such inconvenience, the developer replacement interval may be shortened, and the amount of the developer may be divided and supplied and discharged. Hereinafter, the reason will be described.

The average life of the developer in the developing tank 16 after the replacement of the developer is represented by the following equation as in the above equation (1).

A = P {(1−α) − (1−α) ^{n / P + 1} } / α (1) On the other hand, the average life B of the developer in the developer tank 16 before the developer replacement
Is represented by the following equation (6) from the equation (1).

B = P {(1−α) − (1−α) ^{n / P + 1} } / α + P (6) From these formulas (1) and (6), before and after the replacement of the developer, The change amount D of the average life of the developer in the developing tank 16 is
It is represented by the following equation (7).

D = BA−P = P × {1− (1−α) ^{n / P} } (7) In the above equation (7), the developer replacement ratio α, the replacement interval P, and the copy count value n And the variation D of the average life of the developer in the developing tank 16. From this equation (7), it can be seen that as the copy count value n increases, the variation amount D of the average developer life increases and saturates at the replacement interval P. That is, the maximum value of the change amount D of the average developer life is the replacement interval.

On the other hand, the general relationship between the copy count value n and the charge amount of the developer is as shown in FIG. 19, and it is clear that this change in the charge amount is one of the causes of the density change in the copied image. Is known. Also, the copy count value is set to 1
Experiments have shown that a difference of k, that is, 1000, causes a difference in the charge amount of the developer. Therefore, if P ≦ 1k, there is no difference in density between copied images before and after the replacement of the developer, and the user of the copying machine does not feel uncomfortable.

For example, when the developer replacement amount with respect to the copy count value was made equal and the deterioration degree of the developer in the developing tank 16 before and after the developer replacement until the copy count value was 240 k was examined, FIG. 20 shows a case where 2.5% of the developer is replaced every 1 k, and FIG. 21 shows a case where 0.025% of the developer is replaced every 0.01 k.
In the case shown in FIG. 20, there was a difference in the degree of deterioration of the developer between before and after the replacement of the developer, but there was no difference in the case shown in FIG.

As described above, during the life of the copying machine itself, if the number of times of replacement of the developer is increased even if the total amount of replacement of the developer in the developing tank 16 is the same, the basic configuration shown in FIG. With respect to the deterioration curve s, the change in the deterioration degree change curve t indicating the change in the deterioration degree of the developer before and after the replacement of the developer in the developing tank 16 can be suppressed. As a result, it is possible to suppress a change in the developing characteristics of the developer before and after the replacement of the developer, and to suppress a change in the image quality of the copied image.

[Embodiment 8] A further embodiment of the present invention will be described below with reference to FIGS. 1, 3 to 5, 9 to 13, 23 and 24. For convenience of explanation, means having the same functions as the means shown in the drawings of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the developing device of the present embodiment, the carrier developer storage chamber 20b of the developer supply unit 20 shown in FIG.
A carrier developer having an average life shorter than the developer stored in the developing tank 16 from the beginning is stored. Therefore,
The carrier developer having an average life shorter than the developer in the developer tank 16 is supplied from the carrier developer storage chamber 20b to the developer tank 16. The supply of the carrier developer from the carrier developer storage chamber 20b to the developer tank 16 and the discharge of the developer from the developer tank 16 are controlled by the control device 32 shown in FIG. 4 based on the life of the carrier developer. Is done. That is, control is performed such that the entire amount of the developer in the developing tank 16 is replaced while the life of the carrier developer lasts. Alternatively, the life of the developer stored in the developing tank 16 from the beginning is regarded as the same as the life of the carrier developer, and the degree of deterioration of the developer in the developing tank 16 calculated based on this is determined as the carrier developer. Of the developer is controlled so as not to exceed the average life of the developer.

In this case, the operation of replenishing the carrier developer from the carrier developer storage chamber 20b and the operation of discharging the developer from the developing tank 16 are controlled by the control shown in FIGS. 5 and 6 in the first embodiment. Alternatively, it can be performed by the control of FIGS. 9 to 11 shown in the third embodiment, or by the control of FIGS. 12 and 13 shown in the fourth embodiment.

In the present developing apparatus, the developer in the developing tank 16 is used in a state in which the average life is approaching, that is, in a state in which the function as the developer is considerably lower than the initial use, by the above-described operation. The situation that can be continued can be avoided. Therefore, deterioration of the initial image quality can be prevented, and good image quality can be maintained.

Next, the reason why the above-described function is generated will be described. The relationship between the degree of deterioration of the developer in the developer tank 16 and the copy count value, which is calculated based on the average life of the developer in the developer tank 16, depends on the average life of the carrier developer for replenishment. Replenishing agent and developing tank 16
When the discharge of the developer from is controlled, it differs for each average life of the replenishing carrier developer, and is as shown in FIG. In the figure, curve a _1, when the relative average life 40k of within the developing tank 16 developer, the average life of the carrier developer for replenishment have the same 40k, curve b ₁ is in the developing tank 16 When the average life of the carrier developer for replenishment is 80 k, which is longer than the average life of 40 k of the developer, the curve c ₁ indicates that the average life of the developer in the developing tank 16 is 40 k. When the average life of the carrier developer is 20 k, which is shorter than that, the curve d ₁ indicates that the developer having an average life of 40 k is stored in the developing tank 16, and the developer is not gradually replenished and discharged. The case where the entire amount of the developer in the developing tank 16 is replaced at a time for each predetermined copy count value n is shown. Then, the following becomes clear from FIG.

When the carrier developer having the same average life as the developer in the developing tank 16 is replenished (curve a ₁ ), the deterioration degree of the developing agent in the developing tank 16 becomes 40 k with the increase of the copy count value. The developing tank 16 will be used for a long time in the state where the level of the developer tank has been reached. When the carrier developer whose average life is longer than that of the developer in the developing tank 16 is replenished (curve b ₁ ), the deterioration degree of the developing agent in the developing tank 16 increases as the copy count value increases. The average life of the developer stored from the beginning exceeds the level of 40k, and the developer continues to be used with the life of the developer having an average life of 40k. When the carrier developer whose average life is shorter than the developer in the developing tank 16 is supplied (curve c ₁ )
Although the degree of deterioration of the developer in the developing tank 16 increases with an increase in the copy count value, the degree of deterioration depends on the average life of the developer stored in the developing tank 16 from the beginning.
It stabilizes at a level well below the level of k. When the entire amount of the developer in the developing tank 16 is replaced at one time for each predetermined copy count value n (curve d ₁ ), the degree of deterioration is substantially linear from the state of 0 at the time of replacement of the developer to the level of 40 k. , And returns to the 0 level after the replacement of the developer. Therefore, the relationship between the copy image quality and the copy count value in each of the above cases is as shown in FIG. In the figure, a curve a ₂ , a curve b ₂ , and a curve c ₂
Respectively correspond to the above-mentioned curves a ₁ , b ₁ , and c _1. Curve d ₂ represents the change in copy image quality when the developer in the developing tank 16 having the average life of 40 k is not replaced. Is shown. From the figure, it can be seen that good image quality can be maintained when a carrier developer having a shorter average life than the developer in the developing tank 16 is selected as a replenishing carrier developer.

It should be noted that a developer having a short life is lower in cost than a developer having a long life. Therefore, even if a short-lived developer is used as a replenishing carrier developer and the frequency of replacement of the developer is increased, the cost does not simply increase.

[Embodiment 9] A further embodiment of the present invention will be described below with reference to FIGS. 1, 3 to 5, 7, 25 and 26. For convenience of explanation, means having the same functions as the means shown in the drawings of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the developing device of this embodiment, the supply amount of the carrier developer from the carrier developer storage chamber 20b of the developer supply unit 20 shown in FIG.
6, the amount of developer discharged from the developing tank 16,
The replacement amount in each replacement operation can be selected. That is, in the developing device of the present embodiment, the image quality improvement mode in which the replacement amount by one supply operation and the discharge operation of the developer is relatively large and the image quality is prioritized over the economic efficiency, and the one replacement amount Between the image quality improvement mode and the developer saving mode, in which the amount of replacement at one time is almost intermediate between the image quality improvement mode and the developer saving mode. ing.

In order to perform the above operation, a mode selection switch 5 as mode selection means shown in FIG. 25 for selecting each of the above modes is provided on an operation panel (not shown) of the copying machine.
1 is provided. The control device 32 shown in FIG. 4 controls the carrier developer supply roller 22 and FIG. 1 so that the developer in the developing tank 16 is replaced in the mode selected by the operation of the mode selection switch 51. Alternatively, the operation of the discharge solenoid 28 shown in FIG. 7 is controlled.

In the above configuration, the supply of the carrier developer to the developing tank 16 in the developing device and the developing tank 16
The discharge of the developer from is performed, for example, by the operation of FIG. 5 shown in the first embodiment. At this time, when the image quality improvement mode is selected, the discharge time t _XC and the replenishment time t _YC are set longer than those in the other modes, and the supply of the carrier developer to the developing tank 16 is performed. In addition, the discharge of the developer from the developing tank 16, that is, the replacement of the developer in the developing tank 16 is performed in a relatively large amount. When the developer saving mode is selected, the discharge time t _XC and the replenishment time t _YC are set to be shorter than those in the other modes, and the replacement of the developer in the developer tank 16 is relatively shorter. It is done in small quantities. When the standard mode is selected, the discharge time t _XC and the replenishment time t _YC are set to an intermediate time between the image quality improvement mode and the developer saving mode.
The replacement of the internal developer is performed in an intermediate amount.

By the operation described above, the relationship between the degree of deterioration of the developer in the developing tank 16 and the copy count value is as shown in FIG. 26 in the case of the image quality improvement mode and the case of the developer saving mode. The curve f becomes the curve g in the case of the standard mode. When the above modes are appropriately switched, the above relationship becomes, for example, a curve h. Note that the transition to each mode after the mode switching operation can be performed by approximately several hundred copies in number of copies, depending on the developer replacement cycle or the replacement ratio. And from FIG. 26,
The image quality obtained by copying is the best because the degree of deterioration of the developer in the developing tank 16 is lowest and stable in the image quality improvement mode, and it can be seen that the standard mode and the developer saving mode are in the following order. On the other hand, the consumption amount of the developer is the smallest in the developer saving mode and the largest in the image quality improvement mode. Therefore, the economy is the best in the developer saving mode, and the order of the standard mode and the image quality improvement mode is as follows.

As described above, in the configuration of this embodiment, by selecting the image quality improvement mode, the developer saving mode or the standard mode, the operation of giving priority to image quality over economy, operation of giving priority to economy over image quality, Alternatively, an operation in between them can be selected as desired by the user.

In this embodiment, the discharge time t _XC and the supply time t _YC are changed according to the selected mode. However, the discharge cycle X _C and the supply cycle Y _C , or the discharge time t _{C Both the XC} and the replenishment time t _YC and the discharge cycle X _C and the replenishment cycle Y _C may be changed. That is, any method can be used as long as the replacement amount of the developer in the developing tank 16 per copy count value is changed.

In the above embodiment, the discharge opening 2
The position 4 is best formed on the bottom wall of the developing tank 16 in that the developer is forcibly discharged from the developing tank 16, but is not particularly limited thereto. Any position may be used as long as the developer in the developing tank 16 can be discharged.

[Embodiment 10] A further embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, means having the same functions as the means shown in the drawings of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the developing device of this embodiment, a portion where the deteriorated developer is likely to stay in the developing tank 16, that is, the developing tank 1
A discharge opening 24 is formed in a portion where a continuous flow of the developer does not occur in 6. At the position of the discharge opening 24 that meets the above conditions, the magnetic force of the developing roller 17 is difficult to reach,
This is a position where the developer does not flow even when the stirrer 18 rotates. The above position in the developing tank 16 shown in FIG. 27 corresponds to the lower wall portion 16 located below the stirrer 18 in the developing tank 16.
b or the side wall portion 16 located in the radial direction of the stirrer 18
d, or both side walls located in the axial direction of the stirrer 18.

In this embodiment, the discharge opening 24
Is a side wall portion 16d located in the radial direction of the agitator 18, and is formed at a portion where the upper layer portion of the developer contacts. Therefore, the opening / closing mechanism 25 is provided on the side wall 16d so as to correspond to the discharge opening 24. Further, a collection container 23 having an open side surface is detachably attached to the side wall portion 16d from the side so as to cover the discharge opening 24. The configuration shown in each of the above embodiments can be applied to the control of the opening / closing lid 26 in the opening / closing mechanism 25.

In the developing device of this embodiment, with the above-described configuration, when the discharge opening 24 is opened by the opening operation of the opening / closing lid 26, the deteriorated developer remaining without contributing to the developing operation can be surely removed. And the deteriorated developer can be efficiently replaced with new developer replenished from the developer supply unit 20. Therefore, the developer in the developing tank 16 can be effectively used, and the charging performance of the developer in the developing tank 16 can be maintained in a good state, whereby a good image quality can be maintained.

In each of the above embodiments, the developer supply unit 20 is provided with the toner storage chamber 20a and the carrier developer storage chamber 20b, and the supply of the carrier developer is controlled separately from the supply of the toner. As described above, only the carrier developer storage chamber for storing the carrier developer in which the toner is mixed at a predetermined high concentration is provided in the developer supply unit 20, and the density detection signal from the toner density detection sensor 34 is provided. Accordingly, it is also possible to adopt a configuration in which the carrier is supplied together with the toner. In this case, when the cumulative amount of the carrier developer sequentially replenished in accordance with the density detection signal reaches a predetermined amount, the opening and closing is performed such that an amount corresponding to the carrier amount in the cumulative amount is sequentially discharged. The opening / closing operation of the lid 26 is controlled.

[0123]

[Table 1]

[0124]

[0125]

[0126]

[0127]

[0128]

As it is evident from the foregoing description, the developing device of the first aspect of the present invention, with the discharge opening for the developer discharge is formed in the discharge portion of the developing tank by the driving means to open and close the discharge opening While the driven opening / closing lid is provided, the developer replenishing unit is configured such that the total replacement amount of the developer at each predetermined repetition by the replenishment from the developer replenishing unit and the discharge of the developer through the discharge opening is sequentially increased. And a supply / discharge control means for controlling the driving means.

In this way, during the initial period when the deterioration of the developer is not so advanced, wasteful discharge of the developer which can be sufficiently used for the development is suppressed, while the deterioration in the developing tank is prevented. Of the charging performance is suppressed. Therefore, good image quality can be maintained more reliably.
In addition, as described above, the replacement efficiency is improved by changing the replacement amount in accordance with the degree of progress of the deterioration, thereby providing an effect that the consumption amount of the entire developer can be reduced.

[0130]

[0131]

The developing device according to the second aspect of the present invention
A discharge opening for discharging the developer is formed at a discharge portion of the developing tank, and an opening / closing lid driven by a driving means to open and close the discharge opening is provided. The repeated operation for gradually replacing the developer in the developing tank by discharging the developer of
The configuration includes a cumulative driving time reference control unit that controls the developer replenishing unit and the driving unit so as to be performed based on the cumulative driving time of the rotary driving body of the stirrer and the developing roller.

As described above, the supply and discharge of the carrier developer are performed based on the accumulated driving time of the rotary driving member such as the stirrer in the developing tank, which is more directly related to the deterioration of the stored developer. Accordingly, for example, even when the preliminary rotation of the rotary driver during warm-up when the power is turned on affects the deterioration of the developer, it is possible to perform the replacement process more suitable for the progress of the deterioration of the developer. . As a result,
This has the effect that the charging performance can be more reliably maintained and good image quality can be reliably maintained.

[0134]

[0135]

[0136]

[0137]

Further, the developing device according to the third aspect of the present invention
A discharge opening for discharging the developer is formed in a discharge portion of the developing tank, and an opening / closing lid driven by driving means to open and close the discharge opening is provided, while each supply operation of the carrier developer to the developing tank is performed. At the time of each discharge operation of the developer from the developing tank, a preset use limit of the developer indicated by the number of image forming operations is defined as a developer service life, and replenishment of the developer indicated by the number of image forming operations is performed. And when the interval until the next process of the discharge process is the developer replacement interval, the amount of developer in the developer tank / (developer usage life / developer replacement interval) or more is supplied to the developer tank, In addition, the apparatus is provided with a replenishing / discharging control means for controlling the developer replenishing section and the driving means so as to be discharged from the developing tank.

As a result, the effect that the deterioration of the charging performance of the developer can be surely suppressed and good image quality can be maintained more reliably can be achieved.

The developing device according to the fourth aspect of the present invention provides
A discharge opening for discharging the developer is formed in a discharge portion of the developing tank, and an opening / closing lid driven by driving means to open and close the discharge opening is provided, while the developer supply portion is housed in the developing tank. This is to replenish the carrier developer having an average life shorter than that of the developing agent. The operation of replenishing the carrier developer to the developing tank and the operation of discharging the developer from the developing tank are replenished from the developer replenishing unit. In this configuration, a supply / discharge control unit that controls the developer supply unit and the driving unit is provided based on the average life of the carrier developer.

Accordingly, it is possible to avoid a situation in which the developer in the developing tank is approaching the average life, that is, a situation in which the developer is continued to be used in a state where the function as the developer is considerably lower than the initial use. As a result, it is possible to prevent the initial image quality from deteriorating, and it is possible to more reliably maintain good image quality.

The developing device according to the fifth aspect of the present invention provides
A discharge opening for discharging the developer is formed in a discharge portion of the developing tank, and an opening / closing lid driven by driving means to open and close the discharge opening is provided. At least an image quality improvement mode and a developer saving mode are set. A mode selecting means for selecting, a replenishing amount of the carrier developer to the developing tank and a discharging amount of the developer from the developing tank become relatively large when the image quality improving mode is selected, while the developer saving mode And a replenishment / discharge control means for controlling the developer replenishing unit and the driving means so that the number is relatively reduced when is selected.

As a result, it is possible to select an operation that prioritizes image quality over economy and an operation that prioritizes economy over image quality as desired by the user.

[0144] The developing apparatus of the invention of claim 6 wherein the
The developing device according to any one of claims 1 to 5, wherein the discharge opening is formed in a wall of the developing tank at a portion where the developer stays in the developing tank.

Accordingly, in addition to the effects of the invention described in any one of the first to fifth aspects , when the discharge opening is opened by the opening operation of the opening / closing lid, the liquid remains in the developing tank without contributing to the developing operation. The deteriorated developer can be reliably discharged, and the new developer and the deteriorated developer can be efficiently replaced. Therefore, it is possible to maintain the charging performance of the developer in the developing tank in a more favorable state, thereby achieving an effect that a good image quality can be more reliably maintained.

[Brief description of the drawings]

FIGS. 1A and 1B show a main part of a developing device according to an embodiment of the present invention, in which FIG. 1A is a longitudinal sectional view, and FIG. 1B is a line II in FIG. FIG.

FIG. 2 is a schematic diagram showing an overall configuration of a copying machine in which the developing device is built.

FIG. 3 is an enlarged sectional view showing a developing device in the copying machine.

FIG. 4 is a control block diagram of the copying machine.

FIG. 5 shows replenishment performed by a control device in the copying machine.
9 is a flowchart illustrating a processing procedure of discharge control.

6A and 6B show an example of a replenishment / discharge control cycle. FIG. 6A is a timing chart in the above-described copying machine, and FIG. 6B is a timing chart in a conventional copying machine.

FIG. 7 is a longitudinal sectional view showing a main part of a developing device in another embodiment of the present invention.

8A and 8B are diagrams for explaining a flow state of a developer in a developing tank accompanying rotation of a stirrer in the developing device, wherein FIG. 8A is a schematic plan view viewed from above, and FIG. b)
Is a schematic longitudinal section.

FIG. 9 is a control block diagram of a developing device according to still another embodiment of the present invention.

10A and 10B show a control procedure in the control device in the embodiment of FIG. 9, wherein FIG. 10A is a flowchart showing a discharge processing procedure, and FIG. 10B is a flowchart showing a replenishment processing procedure. It is.

FIG. 11 is a flowchart showing a processing procedure of monitoring control in the control device in the embodiment of FIG. 9;

FIG. 12 is a flowchart showing a discharge processing procedure in a developing device according to still another embodiment of the present invention.

FIG. 13 is a timing chart showing an example of an emission control cycle in the embodiment of FIG.

FIG. 14 is a flowchart illustrating a procedure of a discharging process and a replenishing process in a developing device according to still another embodiment of the present invention.

FIG. 15 is a flowchart showing a discharge processing procedure and a replenishment processing procedure in a developing device according to still another embodiment of the present invention.

16 is a flowchart illustrating another example of the discharge processing procedure illustrated in FIG.

FIG. 17 is a view showing still another embodiment of the present invention, in which the developer in which the total amount in the developing tank is Mg is Pk (k = 100).
FIG. 9 is an explanatory diagram of a change in the life of a developer in a developing tank when replacement is performed at a rate of 100α% for every (0 sheets).

FIG. 18 shows that the amount of developer used in the developing tank is equal to the amount of discharge and the amount of discharged developer is equal to 40 k, the replacement interval is 1 k, the amount of developer in the developing tank is 500 g, 6 is a graph showing a relationship between a copy count value and a degree of deterioration of a developer in a developing tank when an amount of 12.5 g is set to 100.

FIG. 19 is a graph showing a general relationship between a copy count value and a charge amount of a developer.

FIG. 20 shows that the developer in the developing tank is copied at a copy count value of 1 k.
9 is a graph showing the relationship between the copy count value and the degree of deterioration of the developer in the developing tank when 2.5% is replaced every time.

FIG. 21 shows that the developer in the developing tank is set to a copy count value of 0.0
9 is a graph showing the relationship between the copy count value and the degree of deterioration of the developer in the developing tank when 0.025% is replaced every 1 k.

FIG. 22 is a graph showing a deterioration degree change curve t and a basic deterioration curve s before and after replacement of a developer in a developing tank.

FIG. 23 shows yet another embodiment of the present invention, and is a graph showing the relationship between the copy count value and the degree of deterioration of the developer in the developing tank when each developer having a different life is supplied. .

24 is a graph showing a relationship between a copy count value and copy image quality when the replenishing developer shown in FIG. 23 is used.

FIG. 25 is a control block diagram of a copying machine showing still another embodiment of the present invention.

FIG. 26 shows the relationship between the degree of deterioration of the developer in the developing tank and the copy count value in the image quality improvement mode (curve e), the developer saving mode (curve f), and the standard mode (curve g) in the copying machine. It is a graph.

FIG. 27 is a sectional view of a developing device showing still another embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 4 photoconductor 8 developing device 16 developing tank 16b bottom wall portion 17 developing roller 18 stirrer 20 developer supply unit (developer supply unit) 24 discharge opening 26 opening / closing lid 28 discharge solenoid (drive means) 32 control device (supply / supply) Discharge control means, cumulative operation time reference control means) 43 monitoring control section (simultaneous processing prohibition control means) 51 mode selection switch (mode selection means)

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Ueda 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Hideo Yamasa 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp shares JP-A-4-118675 (JP, A) JP-A-4-37781 (JP, A) JP-A-4-29271 (JP, A) JP-A-4-66984 (JP, A) JP-A-4-115236 (JP, A) JP-A 1-177763 (JP, U) JP-A 63-180866 (JP, U) JP-A 63-180864 (JP, U) Field (Int.Cl. ⁶ , DB name) G03G 15/08

Claims (6)

(57) [Claims] An agitator for agitating a developer and a developing roller for supplying the developer to a photoreceptor are rotatably provided in a developing tank containing a developer comprising a toner and a carrier. In the developing device in which the developer is sequentially replenished from the developer replenishing section to the developing tank, while the developer in the developing tank is discharged from a discharging section formed in the developing tank, a discharging opening is formed in the discharging section. And an opening / closing lid driven by a driving means to open and close the discharge opening, and a total of a total number of times of a predetermined number of repetitions by replenishment from the developer replenishing portion and discharge of the developer through the discharge opening is provided. A developing device comprising: a supply / discharge control unit that controls the developer supply unit and the driving unit such that the replacement amount of the developer is sequentially increased. 2. A developer tank containing a developer comprising a toner and a carrier is provided with a rotatable driving member for rotating a stirrer for stirring the developer and a developing roller for supplying the developer to a photoreceptor. In a developing device in which a carrier developer containing a carrier is sequentially supplied to a developing tank from a developer replenishing section, the developer in the developing tank is discharged from a discharging section formed in the developing tank. Is provided with an opening / closing lid which is driven by a driving means to open and close the discharge opening, and a developer tank is provided by replenishment from the developer supply section and discharge of the developer through the discharge opening. A cumulative driving time reference for controlling the developer replenishing unit and the driving means such that a repetitive operation for gradually replacing the developer in the developer is performed based on the cumulative driving time of the rotary driving body. A developing device comprising control means. 3. A carrier containing a carrier, wherein a stirrer for stirring the developer and a developing roller for supplying the developer to the photoreceptor are rotatably provided in a developing tank containing a developer comprising a toner and a carrier. In the developing device in which the developer is sequentially replenished from the developer replenishing section to the developing tank, while the developer in the developing tank is discharged from a discharging section formed in the developing tank, a discharging opening is formed in the discharging section. An opening / closing lid is provided which is driven by a driving means to open and close the discharge opening. On the other hand, during each replenishing operation of the carrier developer into the developing tank and each discharging operation of the developer from the developing tank, an image is formed. The preset use limit of the developer indicated by the number of forming operations is defined as the developer service life, and the interval between the replenishment and discharge processing of the developer indicated by the number of image forming operations until the next processing is defined as the developer. When the replacement interval is set, the amount of developer in the developing tank /
A replenishment / discharge control unit for controlling the developer replenishing unit and the driving unit such that the amount of developer greater than (developer usage life / developer replacement interval) or more is supplied to the developing tank and discharged from the developing tank. A developing device, comprising: 4. A carrier containing a carrier, wherein a stirrer for stirring the developer and a developing roller for supplying the developer to a photoreceptor are rotatably provided in a developing tank containing a developer comprising a toner and a carrier. In the developing device in which the developer is sequentially replenished from the developer replenishing section to the developing tank, while the developer in the developing tank is discharged from a discharging section formed in the developing tank, a discharging opening is formed in the discharging section. In addition, an opening / closing lid driven by a driving unit is provided to open and close the discharge opening. On the other hand, the developer replenishing section includes a carrier developer having an average life shorter than the developer stored in the developing tank. The operation of supplying the carrier developer to the developing tank and the operation of discharging the developer from the developing tank are performed based on the average life of the carrier developer supplied from the developer supply unit. And a supply / discharge control means for controlling the developer supply section and the driving means. 5. A carrier containing a carrier, wherein a stirrer for stirring the developer and a developing roller for supplying the developer to the photoreceptor are rotatably provided in a developing tank containing a developer comprising a toner and a carrier. In the developing device in which the developer is sequentially replenished from the developer replenishing section to the developing tank, while the developer in the developing tank is discharged from a discharging section formed in the developing tank, a discharging opening is formed in the discharging section. And an opening / closing lid which is driven by a driving means to open / close the discharge opening, and at least a mode selecting means for selecting an image quality improving mode and a developer saving mode; The replenishment amount of the developer and the discharge amount of the developer from the developing tank are relatively large when the image quality improvement mode is selected, while the relative amounts are relatively large when the developer saving mode is selected. And a supply / discharge control unit for controlling the developer supply unit and the driving unit so as to reduce the number of units. Wherein said discharge opening, a developing device according to any one of claims 1 to 5, characterized in that the developer in the developing tank is formed in a wall of the developing tank at the site of residence .