JPH04171469A - Developing device in image forming device - Google Patents

Abstract

PURPOSE:To enable stable make-up so as to uniform image density by selecting bias to be applied to a make-up means on the basis of the difference of standard make-up bias applied to a toner make-up means as the center value so as to output this bias to a bias setting circuit, and correcting the center value of the difference according to the frequency of make-up. CONSTITUTION:When a copying start switch 17 is turned on, a toner make-up control part 16 starts control processing. The toner make-up control part 16 changes make-up data on the past seven pieces, for instance, takes in detection output from photo-sensors 52, 53 confronting a toner make-up roller 8, and discriminates whether the detection output difference has the fixed value. In the case of being out of the fixed value, the toner make-up control part 16 selects the bias potential to a supply roller 7 on the basis of a specified table so that the output difference between the photo-sensors 52, 53 becomes the fixed value, and outputs this bias potential to a bias circuit 15. Excess make-up or defective make-up caused by environmental change can be thereby coped with to enable make-up control for stabilizing image density.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device in an image forming apparatus such as a copying machine, and more particularly to a toner replenishment control device.

(Prior Art) As is well known, in image forming apparatuses such as copying machines and printers, an electrostatic latent image formed on a photoconductor is processed using a two-component developer containing a mixture of toner and carrier, for example. A copy is obtained by processing a visible image using a photocopy process, transferring the visible image onto copy paper, and then fixing it.

One of the above-mentioned image forming apparatuses is a color copying machine that obtains a color image by superimposing images of different colors on the same copy paper, and the schematic configuration thereof will now be explained with reference to FIG. 5 as follows. 6 That is, this color copying machine includes a scanner part 21 for reading a document, an image processing part 22 that electrically processes an image signal output as a digital signal from this scanner part 21, and an image processing part 2.
The printer section 23 forms an image on copy paper based on the image recording information of each color from 2.

The scanner part 21 described above includes a lamp 2 that illuminates the original placed on the original placing table 24 while moving in the scanning direction.
5, a mirror 26, 27° 28 for setting the optical path of the reflected light from the document illuminated by the lamp 25, and an imaging lens 29 disposed in this optical path for forming an image on the dichroic prism 30. It includes a light receiver 31 that separates the reflected light from the document into colors and receives the light for each wavelength. In the above-mentioned scanner part 21, the dichroic prism 30 separates the reflected light from the document into three colors, for example, red R, green G, and blue B, that is, the image light, and separates the colors of each wavelength. The light enters the light receivers, that is, the red CCD 31R, the green CCD 31G, and the blue CCD 31B, and is converted into a digital signal within the light receiver.

The digital signal described above is output to the image processing section 22,
The processing unit 22 performs the processing necessary for image forming exposure, which will be described later, to record information of each color, for example, black (hereinafter abbreviated as Bk), yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), The signals are converted into signals for recording each color of cyan (C).

Although FIG. 5 shows the case where the above-mentioned four colors Bk, Y, M, and C are formed, the number of colors is of course not limited to this.

On the other hand, signals from the five image processing sections 22 are input to the printer section 23 and are used to control the operation of the image exposure laser light emitting devices 1328k, 32C132M, and 32Y according to the respective colors.

The printer section 23 described above is a section that exposes image light from a document onto a photoreceptor, processes the electrostatic latent image formed by this exposure into a visible image using a developer, and then transfers it onto copy paper. It is.

That is, in the case shown in the figure, the printer unit 23 has four sets (7 sets).
) Recording device 1338k, 33C133M, 33Y
(That's it.

Since each of the above-mentioned printing apparatuses has the same configuration, in order to simplify the explanation, the printing apparatus for C (cyan) will now be explained, and explanations for other colors will be omitted. Note that components having the same function in each color layer are given the same reference numerals, and in order to distinguish the configuration of each color, a subscript indicating each color is attached to the reference numeral.

In other words, a recording device for C (cyan)! 33C is a photoconductor 3 on a drum in the optical path from the laser beam emitting device 32G.
4C, and around the photoconductor 34C, a charging device 3 for performing image forming processing along the rotational direction.
5C, developing device l36C1 transfer device! 37C etc. are provided in the same manner as in known copying machines.

Then, the photoreceptor 3 is uniformly charged by the charging device 35C.
4C, a cyan latent image is formed by exposure by a laser beam emitting device 32C, and the latent image is processed into a visible image by a developing device 36C.

On the other hand, the printer section 23 is provided with a paper feed section for copy paper.
Copy paper having one of the various sizes selected is fed, and the leading edge of the copy paper is aligned with the leading edge of the image by the registration rollers 40, and then placed on the photoreceptor 3.
The image is conveyed toward the conveyor belt 41 passing through the transfer position C.

Then, the copy paper carried on the conveyor belt 41 and conveyed to the transfer position of the photoreceptor 34C is sequentially conveyed to the photoreceptor 348, which has been subjected to visible image processing, toward 34C134M and 34Y. After the visible image of each color is electrostatically transferred by the action of the transfer device i37 provided oppositely, the visible image is conveyed from the conveyor belt 41 toward the fixing roller 42, where it is fixed, and then discharged outside the machine by the discharge roller 43. be done. The above-described transfer belt 41 electrostatically attracts the copy paper it carries, so that the copy paper is transported at the speed of the belt without positional deviation.

By the way, in the above-mentioned developing device, for example, when a two-component developer is used, which is a mixture of resin toner and magnetic carrier such as iron powder, an amount of toner corresponding to the amount of toner consumed is replenished. It is necessary to maintain a constant concentration.

For this reason, in the past, a reference density pattern was developed on the photoreceptor, the ratio of the density of this pattern to the density of the photoreceptor's background was calculated, and the toner was added to the developing device so that this ratio remained constant. Structures for quantitative replenishment (for example, JP-A-63-210873, JP-A-63-27868)
Measure the image density on the photoreceptor at the current stage,
If the density is not at a predetermined density, the operating state of the replenishing member in the toner replenishing section, such as the number of rotations and rotational speed of the replenishing roller, is controlled so as to correct the density. Publication No. 56542, JP-A-60-165
465, Japanese Unexamined Patent Publication No. 63-101970), or the bias applied to the replenishing member is controlled based on the difference between the image density of the photoreceptor and the reference density.
In addition to this, a structure that controls the operating state of the above-mentioned supply member (for example, Japanese Patent Laid-Open No. 57-221798
(Japanese Unexamined Patent Publication No. 146081/1981).

(Problem to be Solved by the Invention) However, in the above-mentioned toner supply control,
In some cases, toner is replenished while the photoreceptor is being developed.
In such a case, the image density increases from the time the toner is replenished, and density unevenness occurs in the developed image, resulting in extremely poor image characteristics as a copy.

In addition, due to changes in the developer environment (charge-up), toner replenishment may be insufficient or oversupplied.For this reason, for example, when copying is performed a predetermined number of times, such as every 8 sheets, the toner is refilled several times. The predetermined standard replenishment potential, that is, the bias applied to the developing sleeve (VB) and the standard replenishment bias (Vi) are counted.

), a method has been proposed in which the image density is stabilized by changing the replenishment potential according to the number of replenishments as shown in the table below (No. 44).

However, when replenishing the developer using the replenishment control described above, as the developer is used, the amount of replenishment decreases even if the replenishment potential is the same, as shown in Figure 6, and the replenishment potential oscillates. This may cause image density to become unstable. In addition, in FIG. 6, FIG. 6(A) shows the case where a new developer is used.
FIG. 6(B) shows the case where developer is used, which is collected several times and replenished again.

The main reasons for this are thought to be that carrier acceptance decreases as the developer deteriorates, and toner adheres to the developing sleeve, making the sleeve more susceptible to staining and making it impossible to obtain sufficient replenishment potential. .

Another cause of the decrease in the amount of toner replenishment mentioned above is that when toner adheres to the developing sleeve, the bias effect is reduced and the electric field between the developing sleeve and the replenishment roller is weakened, causing the replenishment roller to Since it becomes difficult for the toner to move to the developing sleeve, the amount of toner consumed by the replenishment roller may decrease.

Therefore, in order to prevent toner from being replenished from the replenishment roller to the developing sleeve, in other words, to prevent the amount of toner consumed on the replenishment roller from decreasing, the toner is stored separately from the image on the photoreceptor. By detecting the density of the formed developed pattern for toner density detection, the density is maintained at a constant level.
The dynamic range of the developing bias toward the developing sleeve side is changed, but if the amount of toner supplied from the above-mentioned replenishment roller to the developing sleeve decreases, changing the dynamic range will reduce the replenishment potential. When the developing potential is no longer available, increasing the developing potential is carried out, but even if such a method is used, if the amount of toner supply decreases, there are cases where increasing the developing potential will not have an actual effect. There is.

SUMMARY OF THE INVENTION In view of the above problems in toner replenishment control, an object of the present invention is to suppress a decrease in the amount of toner replenishment by facilitating the movement of toner from the replenishment roller to the developing sleeve, and to prevent replenishment during development. To provide a developing device capable of replenishing and uniformizing and stabilizing image density even when the developing device is started.

(Means for Solving the Problem) In order to achieve this object, the present invention is directed to a replenishing means for supplying toner to a magnetic brush developing sleeve through a replenishing tank supply means, the toner replenishing means, and the replenishing means. In a developing device including means for applying a bias to a supplying means for supplying toner, the developing device is disposed upstream and downstream in a moving direction of the toner replenishing means, and detects the state of supply of toner to the developing sleeve. an optical sensing element that
The replenishment toner bias setting circuit is connected to the output side, and the input side includes an optical detection element that detects the reflected density from the density reference pattern formed on the photoconductor and the toner supply state of the toner replenishment means. The toner replenishing device includes a control unit connected to a detection optical element, and the control unit detects the toner supply state from the optical element on the toner replenishing means side, thereby reducing toner consumption. When it is determined that this is the case, the bias towards the supply means side is adjusted, and when a predetermined number of copies have been made, the number of toner replenishments within that number of copies is counted, and the target number of replenishments is determined according to the number of copies. The difference between the bias (VB) applied to the developing sleeve and the standard replenishment bias (v8°) applied to the toner replenishment means (V s V ll
-) as the center value to be applied to the replenishment means and outputs it to the bias setting circuit, and furthermore, the difference (Vll V)I is determined according to the number of replenishments. ) is characterized by correcting the center value of

(Function) According to the present invention, when it is determined that the amount of toner consumed on the replenishment means has decreased, the bias to the supply means is changed to promote the movement of toner to the replenishment roller. Based on the number of toner replenishments within the preset number of copies, if the number of toner replenishments tends to be large, the bias potential is adjusted in a direction that increases the difference between the bias applied to the toner replenishing means and the developing bias. and also,
On the contrary, if the number of toner replenishments tends to be low, the bias potential should be set in a direction that reduces the difference between the bias applied to the toner replenishing means and the developing bias to stabilize the amount of toner replenishment. I can do it.

(Embodiment) Hereinafter, details of an embodiment of the present invention will be explained with reference to FIGS. 1 to 4.

FIG. 1 is a schematic cross-sectional view showing the overall structure of a developing device according to an embodiment of the present invention.

That is, in FIG. 1, a developing device 1 includes a developing tank 3 having a developing sleeve 2 therein, and a replenishing tank 4 containing replenishing toner.

The developer tank 3 described above has an opening at a position facing the photoreceptor 5, and a portion of the circumferential surface of the developing sleeve 2 is exposed from this opening. The rotation direction of the developing sleeve 2 is set so that it can move tangentially in the same direction as the photoreceptor 5, and a developing main pole, which is provided internally at a position facing the photoreceptor 5, is fixed. A magnetic brush is formed on the surface of the magnet group 6, and the magnetic brush is made to correspond to the photoreceptor 5.

On the other hand, a supply roller 7 is located at the outlet of the supply toner in the supply tank 4, and this supply roller 7 is connected to the developing sleeve 2.
The replenishment roller 8 is in contact with the replenishment roller 8, which is close to the replenishment roller 8. and,
A blade 9 is brought into contact with the replenishment roller 8 together with the supply port spatula 7, and the replenishment toner rubbed and supplied by the supply roller rough is made into a thin layer by the blade 9 and carried on the surface, and directed toward the developing sleeve 2. It is designed to be transported.

Further, this replenishment roller 8 includes a clutch 10 that is activated via a control section to be described later, and by turning on the clutch 10 when replenishing toner, it is possible to replenish toner toward the developing sleeve 2. It can be rotated in any direction. In FIG. 1, reference numeral 11 indicates a developer recovery screw, reference numeral 12 indicates a supply screw that directs the recovered developer toward the developing sleeve 2 again, and reference numeral 13 indicates a seal plate. There is.

The above-mentioned developing sleeve 2, supply roller 7, supply roller 8
and blade 9 each have a bias circuit 14.1.
5 are connected, and each bias circuit 14.15 is
Among them, the bias circuit 15 for the supply roller 7, replenishment roller 8, and blade 9 in the replenishment tank 4 is operated and controlled by a toner replenishment control section 16, which will be described later.

That is, as shown in FIG. 2, the toner supply control section 16 includes, for example, a microcomputer 16A as a main part, and this microcomputer 16A stores basic programs and basic data necessary for arithmetic control processing. The ROM 16B is equipped with a ROM 16B, and the RA for importing data is equipped with a RA. (I10 interface) Signals are exchanged via 16D.

The input port of the input/output device 16D described above includes a copy start switch 17 and a numeric keypad 18 for setting the number of copies.
, and a reference density pattern 5 formed on the photoreceptor 5.
A (see FIG. 1) photosensor 19 that detects the density of toner replenishment roller 8, and photosensors 52 that are arranged close to each other on the upstream side and the downstream side across the position facing the developing sleeve 2 in the rotational direction of the toner supply roller 8. .53 are connected to each other.

Further, the output port of the input/output device 116D is connected to the drive circuit 10A of the clutch 10 and the bias circuit 15 described above.
is connected.

The toner replenishment control unit 16 operates a toner replenishment roller 8 for correcting the amount of toner replenishment according to the number of toner replenishments for a predetermined number of copies (in the case of the present embodiment, the past eight copies).
and to set the bias potential to the supply roller 7. Specifically, as shown in FIG. 3, the polarity and potential are set in a direction that eliminates the difference between the charge amount and the target image density. It is supposed to be done.

In other words, if the difference between the outputs from the photosensors 52 and 53 facing the toner replenishment roller 8 is a constant value, toner transfer from the toner replenishment roller 8 to the developing sleeve 2 occurs, resulting in so-called toner replenishment. is performed, and as a result, it can be determined that the toner on the toner replenishment roller 8 has been consumed. Therefore, the output (VB
The bias applied to the supply roller 7 is variably controlled so that the difference between □ and Vsa) becomes a constant value, thereby promoting the transfer of toner to the toner supply roller 8.

On the other hand, the above-mentioned counting of the number of times of replenishment is, for example, reflected light output from the reference density pattern 5A formed on the photoreceptor 5 (
vsp) and the reflected light output from the background surface of the photoreceptor 5 (VsJ
When the ratio (Vsp/VsJ) is larger than a reference value corresponding to the target image density, that is, when the amount of reflected light is large, it is counted as the time for replenishment.

In other words, in the case of this embodiment, when the toner charge polarity is (-), "As shown in Table 1j, the number of replenishments for the past eight sheets is counted, and the number of replenishments reaches 4 (78 sheets). Select the amount of change in the replenishment potential Δ■□,■ and the amount of change in the center value of the replenishment potential ΔV)In■ so that the replenishment roller 8
It is designed to set the bias applied to the Here, if the center value of the replenishment potential is VB V) lo (where vB: developing bias, -VH0: standard replenishment bias), and the number of replenishments is, for example, 1 out of 8 sheets,
The bias potential (vl) applied to the replenishment roller 8 is expressed as VH=VHo+ΔVIE■+Δ, V, , CI. Therefore, if the number of replenishments is small (centered on the number of replenishments (4 times/8 pieces)), the amount of replenishment per time is large, so the replenishment potential is reduced accordingly. Since the amount is small, we are trying to increase the replenishment potential.

Table 1 However, as the initial value of the center value (vi VHo), B
X, M: 50■ Y, C: 100V. (However, vB
: developing bias, VFIO: standard replenishment bias) Since this embodiment has the above-described structure, the operation of the toner replenishment control section 16 will be explained below based on a flowchart for explaining the operation of the toner replenishment control section 16 shown in FIG. explain.

That is, when the copy start switch 17 is turned on, control processing in the toner replenishment control section 16 is started, and the toner replenishment control section 16 changes the replenishment data regarding the past seven sheets, and then transfers the replenishment data to the toner replenishment roller 8. The detection outputs from the photosensors 52 and 53 are taken in, and it is determined whether the difference between the detection outputs is at a constant value. If the difference is not at a constant value, the bias potential to the supply roller 7 is changed to
2.53 outputs (VB□, ■, 3) are selected based on, for example, Table 1 and output to the bias circuit 15 so that the difference between the outputs (VB□, ■, 3) becomes a constant value. Note that this bias correction is not limited to the selection based on Table 1 above, and it goes without saying that a unique shift amount may be set.

On the other hand, when the above-mentioned replenishment data regarding the past seven sheets is copied, the presence or absence of replenishment is determined based on the signal from the photosensor 19, the total number of replenishment times is determined, and the replenishment bias potential is calculated from this sum based on Table 1 above. selected and output to the bias circuit 15.

Therefore, when the toner on the toner supply roller 8 is not consumed, in other words, when the toner is not transferred to the developing sleeve 2, the shift of the bias potential at the supply roller 7 prevents the toner transfer. The toner that is promoted and replenished from the supply roller 7 to the toner supply roller 8 is
The developing sleeve 2 is supplied according to the bias setting from the bias circuit 15.

(Effects of the Invention) As described above, according to the present invention, by detecting a decrease in the amount of toner consumed on the toner replenishing roller and variably controlling the bias potential for the toner replenishing roller, toner can be replenished to the toner replenishing roller. In addition, the number of times that toner is replenished during a predetermined number of copies is counted, and the compensation potential and the center value of the supply potential are changed. Can be stabilized.

Further, according to the present invention, by making the above-mentioned changes, it is possible to deal with poor replenishment due to developer deterioration and poor replenishment due to sleeve stains, and also to prevent excessive replenishment and poor replenishment due to environmental changes. By being able to deal with this, it is possible to realize replenishment control for stabilizing image density.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the overall configuration of a developing device according to an embodiment of the present invention, FIG. 2 is a block diagram for explaining the main parts of the developing device shown in FIG. 1, and FIG. FIG. 2 is a diagram for explaining the characteristics of the main parts shown in FIG. 2, FIG. 4 is a flowchart for explaining the action of the main parts shown in FIG. 2, and FIG. 5 is a layout showing an example of the image forming apparatus. 6 are diagrams for explaining defects in the conventional structure. DESCRIPTION OF SYMBOLS 1... Developing device, 2... Developing sleeve, 3... Developer tank, 4... Supply tank, 5... Photoreceptor, 7... Supply roller, 8... Supply roller, 9 ...Blade, 15
... Bias circuit, 16 ... Control section, 17 ... Copy start switch, 18 ... Numeric keypad, 19 ... Photo sensor.・Two'-

Claims (1)

[Scope of Claims] Replenishment means for supplying toner from the replenishment tank to the magnetic brush developing sleeve via the supply means, and means for applying a bias to the toner replenishment means and the supply means for supplying toner to the replenishment means. A developing device comprising: an optical detection element disposed on an upstream side and a downstream side in a moving direction of the toner replenishing means to detect a state of supply of toner to the developing sleeve; and a bias setting circuit for the replenishing toner. It is connected to the output side, and the input side is connected to an optical detection element that detects the reflected density from the density reference pattern formed on the photoreceptor and an optical element that detects the toner supply state of the toner replenishing means. a toner replenishing device having a control section configured to control the supplying means when it is determined that the amount of toner consumption has decreased based on detection of the toner supply state from the optical element on the side of the toner replenishing means; In addition to adjusting the bias toward the side, when a predetermined number of copies are made, the number of toner replenishments within that number of copies is counted, and according to the number of copies, the toner is applied to the developing sleeve to reach the target number of replenishments. The difference (V_B - V_
The bias applied to the replenishment means is selected with H_0) as the center value and outputted to the bias setting circuit, and the center value of the difference (V_B-V_H_0) is further corrected according to the number of replenishments. A developing device in an image forming apparatus.