JPH0535101A - Method for replenishing toner - Google Patents

Abstract

PURPOSE:To obtain stable images by changing over a replenishing table according to the number of copies and replenishing a toner thereby attaining an adequate toner concn. at the time of initial setting. CONSTITUTION:Screw feeders 7 can be respectively separately driven by motors 8a to 8c selected by the signal from a counter for the number of copies. Namely, the detection output of the toner concn. from a photodetector 9e is inputted to an operation amplifier 11 where the reference output of the toner concn. from a reference value generator 12, i.e., reference voltage source and the detection output from the photodetector 9e are compared. Any of the motors 8a to 8c is driven for the prescribed period of time by this comparison signal. The mismatch quantity of the replenishing table by a change in the flow property of the toner at the time of initial setting is decreased by controlling the rotating speed of the screw feeder 7 for replenishing water, by which the fluctuation quantity of the developer concn. is decreased. The replenishing amt. is increased on lowering of the toner concn., by which the stable output images are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner replenishing method for a developing device used for developing and visualizing an electrostatic latent image on an image carrier in an electrophotographic image forming apparatus such as a copying machine. It is a thing.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, an electrostatic latent image formed on an image bearing member is developed using a developing device and visualized as a toner image.

Among such developing devices, in a developing device using a two-component developer consisting of magnetic powder (carrier) such as iron powder or ferrite and toner of colored powder, the two-component developer is attracted to a magnet. To form a brush-shaped magnetic brush, and the magnetic brush of the developer is rubbed against the electrostatic latent image on the image carrier to develop the electrostatic latent image.

FIG. 9 shows the structure of a conventional developing device using a two-component developer.

In FIG. 9, 4 is a developing container containing a two-component developer D made of a mixture of toner and magnetic particles,
The developing device has a developing sleeve 3 as a developer carrying member in a developing container 4. The developing sleeve 3 is arranged in parallel to face the peripheral surface of the photosensitive drum 1 of the image carrier of the image forming apparatus, and is synchronized with the photosensitive drum 1 rotating in the direction of arrow A in synchronization with the arrow B by a driving unit (not shown). Is rotated in the direction.

Inside the developing sleeve 3, a plurality of magnetic poles of N pole and S pole are arranged in a predetermined order around the magnet roller 2.
Of the developer D, which is fixedly placed in the developer container 4 and is accommodated in the developer container 4.
Is attracted by the magnet roller 2 to the developing sleeve 3
A magnetic brush D ₁ of the developer D is formed in front of the developing portion which is carried on the developing sleeve 3 and the photosensitive drum 1 face each other. The magnetic brush D ₁ of the developer D develops by rubbing the electrostatic latent image on the photosensitive drum 1 to visualize it as a toner image.

Two screw type agitators 5a, 5b are provided in the lower part of the developing container 4 in parallel with the developing sleeve 3 and are separated by partition walls 5c having unillustrated communication ports at both ends. 5b is rotated by a driving unit (not shown) to stir the developer D in the developing container 4.

Into the developing container 4, the agitator 5b is placed.
Toner is replenished from the toner replenishing tank 6 with the replenishing port 6a positioned above.

A screw feeder 7 reaching the toner replenishing port 6a is provided in the lower part of the toner replenishing tank 6, and the screw feeder 7 is driven by a motor 8 connected outside the replenishing tank 6 to replenish the replenishing tank. The toner T contained in the developer container 6 is conveyed and supplied into the developing container 4 through the supply port 6a. The replenishment operation of the toner T is performed based on the detection result of the toner concentration of the developer D by the toner concentration sensor 9 provided on the developing sleeve 3.

The toner density sensor 9 is the developing sleeve 3
On the lower part of the sensor body 9a located directly above the sleeve 3
A transparent glass window 9b is provided in the horizontal direction, which is the tangential direction to the peripheral surface, and a light emitting element 9 such as an infrared LED is provided above it.
c, infrared transmitting filter 9d and infrared receiving element 9
e is provided.

The light emitting element 9c emits infrared rays in response to a light emission command output from the light emitting element control circuit 10, and the infrared rays irradiate the developer D on the photosensitive drum 3 through the transparent window 9b, and the toner of the developer D is emitted. It reflects with the reflectance according to the density,
An amount of infrared rays corresponding to the toner concentration is received by the light receiving element 9e through the transparent window 9b, and the toner concentration is detected.

The toner density detection output from the light receiving element 9e is input to the operational amplifier 11, and the operational amplifier 11 outputs the toner density reference output from the reference value generator 12 as a reference voltage source and the detection output from the light receiving element 9e. Comparison was made, and the replenishment amount was determined by the difference, and the replenishment time was determined.

Regarding the toner replenishing operation, the toner concentration reference output from the reference value generator 12 is compared with the detection output from the light receiving element 9e, and it is determined that toner replenishment is necessary. Output toner supply signal,
The motor 8 receives this, and the replenishment time is determined by the preset toner replenishment table, that is, the toner replenishment table shown in FIG. 11, and the toner replenishment operation is performed.

[0014]

However, in the above-mentioned conventional example, since the replenishment amount from the toner replenishment tank 6 is high at the time of initial installation of the machine and the replacement of the toner replenishment tank 6, the replenishment time is long. There is a problem that the table of the replenishment amount is deviated, and the developer density becomes higher than the set value and becomes unstable, and the image density becomes unstable.

Further, in the above-mentioned conventional example, when the solid image having the maximum density continues over the entire image area, the toner density of the developer sharply decreases, and it takes a lot of time to return to the proper toner density. Therefore, there is a problem that the density of the output image becomes unstable.

The present invention is intended to solve the above problems. That is, it is an object of the present invention to provide a toner replenishment method capable of replenishing toner with an appropriate density and obtaining a stable image.

[0017]

In order to achieve the above object, the first method of the present invention is such that, at the time of initial setting, the supply table is switched depending on the number of copies, and the second method of the present invention. In this case, the replenishment table is made non-linear depending on the amount of change in toner concentration.

[0018]

According to the first method of the present invention, at the time of initial installation of the machine and replacement of the toner replenishing tank, the replenishment table is made variable until a certain fixed number of copies are completed or for a certain fixed time. It is possible to stabilize the agent concentration and stabilize the image.

In the second method of the present invention, the toner replenishment table is made non-linear and the replenishment amount is increased each time the toner concentration decreases, so that it is possible to prevent the toner concentration from decreasing due to the output of a solid image and to stabilize it. The output image can be obtained.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a developing device shown for explaining a first embodiment of the present invention.

In FIG. 1, members designated by the same reference numerals as those in FIG. 9 described above are the same members, and therefore detailed description thereof will be omitted.

And, 8a, 8b, 8c are motors,
Each of the screw feeders 7 can be driven separately. As shown in FIG. 2, the motor 8a rotates at α rpm, the motor 8b rotates at β rpm, and the motor 8c rotates at γ rpm.

That is, the toner concentration detection output from the light receiving element 9e is input to the operational amplifier 11, and the operational amplifier 11
Compares the reference output of the toner concentration from the reference value generator 12, which is a reference voltage source, with the detection output from the light receiving element 9e, and the comparison signal causes the motors 8a, 8b,
Any one of 8c is driven.

That is, the motors 8a, 8b and 8c are selected by a signal from a copy number counter (not shown).

The number of rotations may be controlled by using one motor and controlling the gear ratio with a clutch.

As described above, the mismatch of the replenishment table due to the change in the fluidity of the toner at the time of initial setting is controlled by controlling the rotation speed of the screw feeder 7 for replenishment, so that the amount of the mismatch can be reduced and the developer concentration can be reduced. The amount of fluctuation can be reduced.

FIG. 4 is an explanatory view showing the replenishment time in the comparison signal of the toner density detection output.

In FIG. 4, a is a replenishment table for copy numbers from o to f, b is a replenishment table for f to g, and c is a conventional replenishment table, that is, a replenishment table for g and subsequent sheets.

FIG. 3 is a graph showing the toner replenishment amount with respect to the number of times of toner replenishment (the number of copies) when the toner replenishment time for replenishing the toner consumption in the average image is once. As can be seen in FIG. 3, the replenishment amount e immediately after installation
Is usually larger due to the supply amount d.

If this is replenished by the ordinary replenishment table c in FIG. 4, the replenishment amount is overwhelmingly large with respect to the consumption amount, and the developer concentration increases significantly, and the developer is developed. It may overflow from the container or the image may be fogged.

A signal from a copy number counter (not shown) is used to supply the replenishment table from the beginning to the f-th sheet using the replenishment table of FIG. 4a, and from the f-th sheet to the g-th sheet of the replenishment table of FIG. 4b. Then, by using the replenishment table in FIG. 4C for the g-th sheet and thereafter, the replenishment amount in the comparison signal can be suppressed within a certain range, and the fluctuation of the developer concentration can be reduced.

Note that a is 20 to 40% of the slope of c, and b is
Is preferably within a range of 15 to 20% of a.

The characteristic of the replenishment amount as shown in FIG. 3 is an average value, but the numerical value may change due to machine difference or the like. Furthermore, it is difficult to realize stepless mechanical and soft means for proper replenishment due to cost, etc., so by combining mechanical and soft means, the replenishment amount can be made more accurate. By bringing them close to each other, the developer concentration can be stabilized. For example, if the mechanical means has two stages and the soft means has three stages, a total of six stages of control can be performed, and more stable replenishment can be performed.

FIG. 5 shows a replenishment table according to the second embodiment of the present invention.

When replenishment is performed using the conventional replenishment table as shown in FIG. 11, when a so-called solid image continues, the toner density decreases as shown in FIG. The toner density sensor 9 detects the amount of change in the toner density, replenishes the toner, and balances the amount of change in the toner density when the toner consumption amount and the replenishment amount are balanced.

Although it is possible to increase the replenishment amount by simply increasing the inclination of the replenishment table of FIG. 11, the replenishment amount becomes too large and the ripple of the change in toner density becomes too large when a small amount of replenishment is performed. I will end up.

By selecting a discontinuous point such as a _{1 in} FIG. 5 as the maximum point of the toner density change amount that can fluctuate in a normal image, the normal replenishment table (A in FIG. 5) can be set up from 0 to a ₁ . The table is used after a _{1 and} the supply amount is increased (B in FIG. 5).

Since the toner density does not greatly change by the amount of an average density image copy which is usually used, there is no particular problem when replenishing using the conventional replenishing table. It is set. However, in a solid image, the consumption amount increases rapidly, so that the replenishment table determined by the linear equation cannot follow the replenishment, which tends to cause a delay. In order to correct this, the coefficient of supply is corrected by changing the coefficient from the point a ₁ on the supply table as shown in FIG. 5 to change the slope and increase the amount of supply, and as shown in FIG. It is possible to stabilize the output image.

In the embodiment of FIG. 5, the discontinuity point is provided to stabilize the toner density by replenishment.
However, it is necessary to provide a plurality of toners in order to further stabilize the toner density and reduce the fluctuation range.

FIG. 7 shows a supply table according to the third embodiment of the present invention.

A normal supply table is used up to point c _{1 in} FIG. When exceeding the c ₁ point, to weaken the rate of decrease in the toner concentration or to return by using the replenishment table up the number of 10% supply amount to _a point a. If you still cannot recover, or if you exceed a point ₁
% Increase the supply amount.

Further, even in the process of returning the toner density, it is possible to obtain the effect of saving the replenishment amount so as not to overreplenish.

When replenishment is carried out at the replenishment table of FIG. 7E, the toner concentration returns toward an appropriate value, and when the variation amount a ₁ is cut off, if the replenishment table of E is performed, the replenishment amount is consumed. This greatly exceeds the amount, and the toner concentration fluctuates in the positive direction. However, as the fluctuation amount becomes smaller, the replenishment amount is reduced by changing the replenishment table as well, so that the replenishment amount does not significantly fluctuate in the positive direction and changes to an appropriate value.

Therefore, the fluctuation of the toner density can be further reduced and the output image can be stabilized.

When the fluidity of the toner is not uniform and is unstable, such as when the machine is initially installed, a plurality of replenishment tables represented by a linear equation are provided, and further, a discontinuity point a ₁ is provided to replenish the replenishment amount. Fluctuate.

For example, taking the initial installation as an example, when the toner is installed in the initial toner replenishing tank 6, the amount of replenishment is several times as large as that in the normal toner replenishment. Therefore, the toner replenishment table has two stages like G ₁ and H ₁ in FIG. 8 until the toner fluidity becomes low and the toner replenishment can be stably performed. Uses a supply table of G ₁ and α and subsequent ones of H ₁ . However, since the fluidity of the toner is not uniform and the correction cannot be completed, the replenishment table is further changed to G ₂ and H _{2 in} FIG. 8 according to the value of the variation amount of the toner concentration. The above α
Is preferably 50-300.

Thus, the shortage of the replenishment amount due to the shortening of the replenishment time by the replenishment table in order to make the initial replenishment amount constant can be alleviated. In other words, it can be used as a correction unit at the time of replenishment when the fluidity of the toner is unstable, and the toner density can be stabilized.

Further, in this embodiment, the supply table has two stages,
Although the discontinuity point is described as one point, it is also possible to control with a plurality of supply tables and a plurality of discontinuity points for more stable control.

[0049]

As described above, according to the first method of the present invention, at the time of initial installation of the machine, the supply table is made variable until a certain number of copies have been completed.
It is possible to stabilize the developer concentration and stabilize the image. According to the second method of the present invention, since the toner replenishment table is made non-linear and the replenishment amount is increased each time the toner concentration decreases, it is possible to prevent the toner concentration from decreasing due to the output of a solid image, and to provide a stable output. Images can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a developing device suitable for implementing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of rotation speed control for the number of copies.

FIG. 3 is an explanatory diagram of replenishment characteristics from the time of initial installation.

FIG. 4 is an explanatory diagram of a replenishment time in a comparison signal of toner density detection output.

FIG. 5 is an explanatory diagram of a toner replenishment table according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a toner density variation at the time of image output depending on the number of copies.

FIG. 7 is an explanatory diagram of a toner supply table according to a third embodiment of the present invention.

FIG. 8 is an explanatory diagram of a toner supply table according to a fourth embodiment of the present invention.

FIG. 9 is a sectional view showing an example of a conventional developing device.

FIG. 10 is an explanatory diagram of a toner density variation when a conventional solid image is output.

FIG. 11 is an explanatory diagram of a conventional toner supply table.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 3 ... Developing sleeve 4 ... Developing device 6 ... Toner supply tank 7 ... Screw feeder 8a, 8b, 8c
... motor 9 ... toner concentration sensor 10 ... light emitting element control circuit 11 ... operational amplifier 12 ... reference value generator

Claims (6)

[Claims] 1. A toner replenishing method for replenishing toner by a signal from a toner concentration detecting means for detecting the toner concentration of a two-component developer comprising toner and carrier. In the initial setting, the toner replenishing table is switched depending on the number of copies. A toner replenishment method characterized by the above. 2. The toner replenishment method according to claim 1, wherein the switching of the toner replenishment table comprises mechanical control. 3. The toner replenishing method according to claim 1, wherein the toner replenishing table is switched by software. 4. A toner replenishment method for replenishing toner by a signal from a toner concentration detecting means for detecting the toner concentration of a two-component developer comprising toner and carrier, wherein the toner replenishment table is made non-linear by the amount of change in the toner concentration. A method of replenishing toner, which is characterized by carrying out. 5. The toner replenishing method according to claim 4, wherein the toner replenishing table has a plurality of discontinuities. 6. The toner replenishing method according to claim 4, wherein a plurality of toner replenishing tables are provided and a plurality of discontinuity points are provided.