JPS63231379A - Method for controlling toner concentration of electrophotographic device - Google Patents

Abstract

PURPOSE:To avert excessive replenishment of toners by a difference in the color and capacity of the toners and to prevent staining of a copy and splashing of the toners by controlling the concns. of the toners in respective plural developing devices disposed around a photosensitive body by different means for controlling toner concns. according to the colors and capacity of the toners housed in said developing devices. CONSTITUTION:The concn. of the toner in the developing device A of the smaller use frequency and capacity of the 1st developing device A and 2nd developing device B disposed around the photosensitive body of a toner concn. control device is detected by an inductance detecting means 3. The concn. of the toner in the developing device B having the large use frequency and capacity is detected by an optical detecting means 2. The color and capacity of the toner housed in the developing device A detected by the means 3 is inputted as a toner replenishment signal to the means 4 for controlling the toner concn. The output obtd. from the concn. difference of the pattern detected by the means 2 and the color assignment signal from a color assignment input means 5 are inputted to the means 4 and 1st and 2nd means 7, 9 for driving toner replenishment are controlled by the output of the means 4, by which the toner is replenished.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a toner density control method for an electrophotographic apparatus.

(Conventional technology) In recent years, multiple developing devices have been placed around the photoreceptor.

An electrophotographic apparatus has been proposed in which a latent image on a photoreceptor is developed (visualized) with toner of an arbitrary color by selecting one of the above-mentioned developing devices according to a user's designation.

That is, for example, in the electrophotographic apparatus shown in FIG. 4, a first developing device A containing red toner around the photoreceptor 1;
Two developing units B each containing black toner are arranged, and when the user operates a mode selection switch (not shown) on the operation panel, each developing unit B can be selected according to the specified mode. A selected developing device A or B is configured to move close to the photoreceptor 1 and obtain a copy of a specified color according to well-known copying processes such as charging, exposure, development, and transfer.

By the way, in the case where the first developing device A and the second developing device B use a two-component developer consisting of toner and carrier, in order to make the density of the copied image uniform, it is necessary to mix the toner and carrier. Toner density control is required to keep the ratio, that is, the toner density, constant.

The toner density control method in the conventional electrophotographic apparatus described above, for example, as shown in FIG. A well-known optical detection means 2 detects the difference in density as a difference in amount of reflected light, and
By photoelectrically converting this amount of reflected light with the P sensor, for example, the front and back of the density pattern can be erased, and the photoreceptor 1
The toner density is detected and controlled by comparing the P sensor output Vs4 (approximately constant) obtained by looking at the surface of the toner and the P positive sensor output Vsp (toner density 1; changes accordingly) obtained by looking at the density pattern. ing. Furthermore, in conventional toner concentration control, the toner concentration is detected at predetermined intervals (for example, every 10 sheets after the first sheet after the main switch is turned on).
If it is detected that the toner concentration is low, the toner replenishment solenoid is turned on and off for each sheet until the first toner concentration detection time, for example, up to the 10th sheet, and replenishes toner to the designated developing device. controlled to continue.

It is known that this toner density control method can be controlled regardless of the color of the toner, although the detection level changes if the detection light of the P sensor is selected as infrared light, as shown in Figure 5. There is.

Therefore, in conventional electrophotographic apparatuses, a method has been adopted in which toner density control is performed using the same optical detection means (including the use of one detection means in common).

However, as shown in FIG. 4, for example, the conventional electrophotographic apparatus has a second developing device B containing frequently used black toner, and a first developing device A containing rarely used red toner. There is a difference in developer capacity, and
Red toner, which has a small capacity, deteriorates more easily over time than black toner, which has a large capacity. Therefore, when these toners are controlled by toner concentration control using the same optical detection means, the red toner deteriorates more quickly over time than the black toner, which has a large capacity. Due to deterioration, even though the toner concentration is appropriate, the P sensor detects that the toner concentration is low, and as shown in Figure 6, red I-toner is oversupplied, resulting in background smudges on copies and damage to the machine due to toner scattering. There was a problem that caused problems.

(Objective) An object of the present invention is to provide a toner concentration control method for an electrophotographic apparatus that can avoid excessive supply of toner caused by differences in toner color or capacity.

(Structure) According to the present invention, the toner density of each of the developing devices is controlled by different toner density control means depending on the color and capacity of the toner contained in the plurality of developing devices around the photoreceptor. Features.

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 shows an example of a toner density control device controlled based on a toner one-time control method according to the present invention.

This toner density control device uses an inductance detection means 3 to measure the toner density of the first developing device A, which is used less frequently and has a lower capacity, among the developing devices A and B arranged around the photoreceptor 1. The toner density of the second developing device B, which is frequently used and has a large capacity, is detected using an optical detecting means 2 similar to the conventional one.

The inductance detection means 3 includes, for example, a detection coil 3a, a reference coil 3b, a detection oscillator 3, as shown in FIG.
c, reference oscillator 3d, gate 3e, integrating amplifier 3f, multivibrator 3g, detector 3h, DC amplifier 31
and a comparator 3j. In this inductance detection means 3, when the developer is passed through the detection coil 3a, the magnetic permeability changes due to a change in toner concentration, that is, a change in the ratio of carrier to toner, and the inductance of the detection coil 3a changes. The toner concentration is detected by utilizing the change in the toner density.

That is, in FIG. 2, the oscillation frequency of the detection oscillator 3c changes due to a change in the inductance of the detection coil 3a. On the other hand, the reference coil 3b is set in advance so that its inductance matches the value at a proper toner concentration. A reference oscillator 3d based on this reference coil 3b
and the oscillation frequency of the detection oscillator 3c, and add this to the integrating amplifier 3f, the detection carrier 3h, and the DC amplifier 3.
1 performs integral amplification, detection, and DC amplification. Here, when the toner concentration of the first developing device A is high, the inductance L of the detection coil 3a becomes small, and the oscillation frequency of the detection oscillator 3c becomes high. As a result, the output of the comparator 3J becomes Lr L
11 level, the toner replenishment signal 1 is output from the comparator 3j.
1 L H is output. On the other hand, when the toner concentration is low, the inductance L of the detection coil 3a becomes large,
The oscillation frequency of the detection oscillator 3C is small. This results in
The output of the comparator 3j becomes ``H'' level, and the toner replenishment signal rr Hrr is output from the comparator 3j.

This toner replenishment signal, ie, the output of the inductance detection means 3, is given to the toner concentration control means 4. Furthermore, this toner density control means 4 has a.

By operating a mode selection switch to designate (specify by the user) the color of the toner to be used, the output of the color designation input means 5 which outputs a mode selection signal and the output of the optical detection means 2 are respectively given.

On the other hand, at the output terminal of the toner density control means 4.

a first toner replenishment drive means 7 for driving the first toner replenishment roller 6 of the first developer A, and a second developer fgt device B;
A second toner replenishment drive means 9 for driving the second toner replenishment roller 8 is connected to each of the two toner replenishment rollers 8 . Here, each toner replenishment drive means 7, 9 is constituted by a mechanism that rotates each toner replenishment roller 6.8 for a predetermined period of time by turning on and off a well-known toner replenishment solenoid.

The toner concentration control means 4 controls the first and second replenishment drive means 7 and 9 in accordance with the outputs of the optical detection means 2, the inductance detection means 3, and the color specification input means 5.

That is, as shown in FIG. 3, for example, when the copy switch of the electrophotographic apparatus is turned on, the toner density control means 4 first controls whether the first developing device A or the second developing device B is used. It is determined whether image creation is to be performed.

This judgment is determined by input from the color designation input means 5. Here, if the user specifies red toner, the first developer A is moved to the vicinity of the photoreceptor 1, and if the user specifies black toner, the second developer B is moved to a developing state. Next, if the first developing device A is selected in the above judgment, the inductance detection mode is turned on, and it is determined whether the output of the inductance detection means 3, that is, the toner replenishment signal, is rr L II according to a predetermined program.
/l It is determined whether Hpg. This results in
When the toner replenishment signal is H'', the first toner replenishment driving means 7 is turned on.

Red toner is replenished into the first developing device A, then a predetermined number of toner replenishments (toner replenishment a preprogrammed number of times)
When this is completed, the first toner replenishment driving means 7 is turned off, and after it is determined whether copying is complete, the operation is stopped.

On the other hand, if the second developing device B is selected in the above judgment,
When the optical detection mode is turned on, the output of the optical detection means 2 is determined according to a predetermined program.
Based on L11, the second toner replenishment driving means 9 is turned on, and black toner is replenished into the second developing device B. Hereinafter, as in the case of red toner, when the predetermined toner replenishment is completed according to the unique program, the second toner replenishment driving means 9 is turned off, and the operation is stopped upon completion of copying.

In this way, the toner density control device implementing the present invention has the following features:
The toner concentration control of the first developing device A and the toner concentration control of the second developing device B can be performed by different toner concentration control means, respectively, so that toner replenishment can be controlled according to unique programs.

Therefore, according to the toner density control method of the present invention,
Excess supply of toner caused by differences in toner color or capacity is avoided.

(Effects) According to the present invention, by avoiding excessive supply of toner, it is possible to prevent background smudges on copies and mechanical troubles due to toner scattering.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the inductance detection means in the above embodiment, and FIG.
4 is a schematic diagram of a conventional electrophotographic apparatus, FIG. 5 is a diagram showing the relationship between the amount of toner adhering to the photoreceptor and the amount of reflected light, and FIG. 6 is a flowchart showing an example of the operation of the above embodiment. is a diagram showing the relationship between the number of copies and toner density. A...First developing device, B...Second developing device, 1...
...Photoreceptor, 2...Optical detection means, 3...Inductance detection means, 4...Toner concentration control means,
5...Color specification input means, 6...First toner supply roller. 7...First toner replenishment drive means, 8...Second toner replenishment roller, 9...Second toner replenishment drive means. % 3 and % 4 figure tiger i house 4 deceased To 1-i Sai At → 艙 2 Yuhu - L + - $f";;j

Claims (1)

[Claims] A plurality of developing devices are provided around the same photoconductor, and the latent image on the photoconductor is visualized by selecting and moving each of the developing devices close to the photoconductor according to a specified mode. The electrophotographic apparatus is characterized in that the toner concentration of each of the developing units is controlled by different toner density control means according to the color and capacity of the toner contained in each of the developing units. Toner concentration control method.