JPS6262376A - Image density controlling device for copying machine - Google Patents

Abstract

PURPOSE:To maintain a picture image density constant by controlling the copy parameter of a developing machine basing on detected the value of concentration of a developer containing magnetic carrier and toner. CONSTITUTION:A controlling section 16 compares the concentration of a developer detected by a developer concentration detecting section 11 with a preset reference value. The output signal makes at least one of toner supply quantity control by on and off of the dispense motor 13 of a developing machine, a picture image density control by the control of bias voltage applied to the roll 18 of the developing machine or a latent image potential contrast control of a sensitive body 20 by the control of voltage applied to an electrostatic charger 19. By the control of copy parameter basing on the concentration of the developer, the required fixed picture image density can be ensured even when the original of large area coverage is copied continuously.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention maintains a constant image density by controlling copy parameters that affect toner density and image density based on a detected value of toner density of a developer. The present invention relates to an image density control device for a copying machine that maintains the image density of a copying machine.

[Conventional technology]

As a conventional image density control device for a copying machine, for example, there is one that controls the image density by controlling the toner density of a developer.

For controlling the toner concentration of this developer, for example, Japanese Patent Application No. 58-223596, Japanese Patent Application No. 59-184
998 and Japanese Patent Application No. 59-184999 for a "developer concentration detection device for copying machines" (November 28, 1981, September 4, 1980, September 4, 1980), ``Developer control device for copying machine'' filed as patent application No. 163076/1982 (September 1982)
5th day of the month), the summary of which is shown in Part 5. That is, a paddle roll 15 transports the developer 1 consisting of two components, a fibrous carrier and toner, a magnet roll 9 that supplies the developer to the concentration detection section, and a fixed amount of the developer on the surface of the roll is transferred to the lower end. The trimmer plate 10 supplies the developer 1 to the developer transport plate 2, and the developer 1 is supplied from the developer transport plate 2 to the developer transport plate 2.
an aluminum roll 3 attached to a mirror-finished sleeve 5 attached to the outer peripheral surface and rotating counterclockwise; a rubber magnet 4 attached to the inner surface of the sleeve 5 to attract and hold the developer 1 on the sleeve surface; There is a spike regulating plate 6a that shapes the developer 1 adhering to the surface of the sleeve 5 into a smooth magnetic brush, and a spike regulating plate 6a is attached to the spike regulating plate 6a to adsorb the developer removed by the spike regulation and prevent it from falling. Preventing magnet 6b
, a transparent conductive glass 7C that electrostatically attracts the developer 1 that is regulated to stand up during concentration measurement, a light emitting element 7a that irradiates light onto the surface of the sleeve 5 through the conductive glass 7c, and The light receiving element 7b receives the light emitted from the light emitting element 7a and reflected on the surface of the sleeve 5 via the conductive glass 7c, and the bias bracket 7d applies a predetermined voltage to the conductive glass 7c. conductive glass 7C
It consists of a scraper 8a that peels off the developer drawn back into the sleeve 5 from the surface of the sleeve 5. In addition to the above configuration, a developer concentration detection section 11 that is connected to the light emitting element 7a and the light reception element 7b and detects the developer source once, a detection section drive power source 12 that drives the development concentration detection section 11, and a development concentration detection section There is a control section 16 that calculates the detected value of the section 11 and controls the drive of the dispense motor 13. Further, a voltage V Ill! is applied to the conductive glass 7G via the conductive glass bias bracket 7d. A power source 14 is provided which includes a NESA bias power source 14a that applies SA and a roll bias power source 14b that applies voltage from the aluminum roll 3 to the sleeve 5.

In the above configuration, as shown in FIG. 6(a), the conductive glass 7c receives a negative voltage (a) applied to the sleeve 5. Voltage vsisa CLEA for removing developer attached to the conductive glass 7C surface based on LL
NING or voltage Vntsa 5ENs for adsorbing the developer on the sleeve 5 surface to the conductive glass 70 surface
*Nt, (either D is V HE!+A bias power supply 1
4a.

Voltage V□SA CL! When AM+□ is applied, the electric field generated between the conductive glass 7C and the sleeve 5 is formed in the direction from the conductive glass 7C toward the sleeve 5, and the toner in the developer is attracted to the sleeve surface, and the conductive glass 70
The surface is cleaned. The detected value of the amount of light received by the light receiving element 7b at this time is vcL! □.

When the developer has not yet been sampled from the developer transport plate 2, no developer is attached to the surface of the sleeve 5, and therefore the light from the light emitting element 7a is transmitted to the conductive glass 7.
The reflected light passes through the conductive glass 7C and is received by the light receiving element 7b.

Next, VNf3A 31! is applied to the conductive glass 7C by the NASA bias power supply 14a. N! When ING is applied and sampled developer is supplied from the developer conveying plate 2, the developer on the surface of the sleeve 5 is exposed to the conductive glass 7c.
When the electric field reaches between the sleeve 5 and the sleeve 5, an electric field is formed in the direction from the sleeve 5 to the conductive glass 7C.

Therefore, the toner contained in the developer 1 adheres to the conductive glass 7C and develops it. By this development, the light emitting element 7a
The light directed toward the sleeve 5 and the reflected light from the sleeve 5 are attenuated or blocked depending on the degree of development, and the development characteristics, that is, the concentration of the developer can be determined from the amount of light received by the light receiving element 7b. The detected value of the amount of light received by the light receiving element 7b at this time is set as VIMAGE.

Figure 6 (a) shows the above Vstsa CLtA□6 and Vn
The relationship between tsASEMSING and developing roll bias V
The detected V eLIAN % V IMAGE is shaped into the waveforms shown in FIGS. 6(b) to 6(c) by the developer density detecting section 11. The control unit 16 outputs a detection pulse as shown in FIG. 6(d), and the V at the pulse timing is
CLEAN SV IMAGE is detected. The ratio of VIMAGt and VCLEAN (7) at that time is taken as the D value. This D value is calculated by the control unit 16, and thereby the degree of development on the conductive glass 7C can be detected. In the developer concentration control, when the D value exceeds a preset reference value of 0.5, it indicates that the amount of development on the conductive glass 7C is small, and the controller 16 turns on the disben smoke 13.
A signal is issued and toner is supplied. When the D value is 0.5 or less, it indicates that the amount of development is large, and the OFF signal continues to be output from the control section 16 to the disbensmoke 13.

FIG. 7 is an explanatory diagram showing specific toner supply control, and as shown in FIG. 7(a), the duty cycle is 1.5.
The D value is detected in seconds, and it is detected three times and the average value is taken.
For example, when the D value is greater than or equal to a certain reference value of 0.5, the dispense motor 13 is turned on for <2.0 seconds to supply toner (0N10 once every 4.5 seconds) as shown in FIG.
FF signal is output).

By detecting the amount of developed toner and controlling the amount of toner supply as described above, an image with a stable density can be obtained.

[Problem that the invention seeks to solve]

However, in the conventional image density control device for copying machines,
Since it only controls the supply of toner, when an original with large area coverage is continuously copied, the amount of toner consumed may exceed the amount of toner supplied, so the density of the copied image will gradually become lighter. There is a problem that it comes.

[Means and effects for solving the problem] The present invention has been made in view of the above problems, and in order to obtain a predetermined image density even when an original with a large area coverage is continuously copied, a developer is used. The present invention relates to an image density control device for a copying machine that controls copy parameters that affect toner density and image density based on a detected toner density value.

〔Example〕

Hereinafter, the image density control device for a copying machine according to the present invention will be explained in detail. FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. It also controls the voltage.

Here, 17 is a power source whose bias voltage applied to the developing machine roll 18 is controlled by the control section 16.

In the above configuration, the control unit 16 compares the detected concentration value of the developer with a preset reference value and controls the toner supply amount by controlling the dispense motor 13 with 0N10FF and by changing the developing bias voltage. Develop bias voltage control and both at the same time.

Alternatively, a predetermined image density can be maintained by performing only one of them.

Toner supply amount control stops toner supply when the detected threshold value is less than a preset reference value Ds=0.5,
When the value exceeds 0.5, toner is supplied.

The toner supply time at this time is, for example, 2 seconds as shown in FIG. 7(b).

On the other hand, the ON time of the dispense motor 13 is, for example,
If the setting is set to 4.5 seconds, there is a time delay from toner supply to density detection for originals with small area coverage (for example, 10% or less), so the toner supply corresponding to this time will be oversupplied, and the second As shown by the dotted line in the figure, the concentration increases beyond the control point. The optimal ON time of the dispense motor is 2 seconds to minimize this overshoot. However, when the ON time is set to 2 seconds, when a document with a large area coverage is continuously copied, the toner supply amount control by the dispense smoke 13 alone cannot prevent the image density from decreasing.

On the other hand, in density control using a developing bias voltage, the image density increases when the developing bias voltage is lowered, so a reduction in the image density is prevented by lowering the bias voltage step by step in accordance with the detected threshold value. I can do it. Figure 3 shows the correlation between the image density and the detected value, and based on the actual results shown by the solid line, the image density is assumed to be 1.1 in the normal case, for example.
If set to keep it above, the detected value will be approximately 0.65.
However, in cases where it is not possible to maintain the image density above a certain value, for example, 1.1 or above, by controlling the toner supply amount using disbensmoke, (1) area coverage When continuously copying large documents (20% or more), (2) If the toner supply due to dispense smoke decreases (when the amount of toner in the toner box is small), in such cases, dispen smoke 13 is turned ON.
A signal is issued to replenish toner, but the detected value exceeds 0.65.

Now, if Ds+=0.65 as the preset reference value, the detection value of the developer density detection section 11 will be 0.5 times in a row.
When the bias voltage exceeds 65 V, the developing bias power supply 17 changes the bias voltage to 300 V, for example, according to a command from the control unit 16.
By changing from 250v to 250v, the image density is 1.1
or more. The condition for returning the developing bias voltage from 250v to 300v is set when the detected value shows 0.65 or less five times in a row.

A specific example of the above control shown in FIG. 4 will be explained as follows.
If the amount of toner supplied by the dispense motor 13 is not in time, the density will decrease as shown in the figure, so when the detected value exceeds the preset reference value Ds+-0,65 five times in a row ( (I)), the developing bias voltage was changed from 300 V to 250 V to prevent the density from decreasing (I (I)). Even after switching the voltage, the toner is still being supplied, so the density increases as shown by the line (■) in the diagram.If the average value of the five detection values becomes 0.65 or less, the voltage is returned to 300V (as shown in the diagram). C)) Or, as shown in the line ■ in the figure, the area coverage of the original is large and the toner consumption is large, so the density decreases, and the D value is the preset reference value Ds□=
If it exceeds 0.8 and is detected five times in a row (as shown (=)),
Furthermore, lower the developing bias voltage one more step. The developing bias voltage can be reduced to the extent that the toner does not adhere to the background portion of the paper and darken the paper.

As described above, by controlling the toner supply amount in combination with the developing bias voltage control, it was possible to maintain the image density at a constant value or higher over almost the entire range of practical detection values.

Note that instead of the developing bias voltage control in the above embodiment, the charger 19 is controlled by the control section 16 according to the detected value.
The latent image potential contrast of the photoreceptor 20 may be controlled by increasing or decreasing the potential of the power source 17a.

Further, in the above embodiment, the optically detected value of the toner density is used as the basis for image density control, but the toner density detected value by other methods may be used without being limited to this optically detected value.

〔Effect of the invention〕

As explained above, according to the image density control device for a copying machine of the present invention, means is provided for controlling copy parameters that affect the toner density and the image density based on the detected toner density value of the developer. Since the density is controlled, a predetermined image density can be maintained even when a document with a large area coverage is continuously copied.

[Brief explanation of drawings]

FIG. 1 is an image forming control device for a copying machine according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the control relationship between toner concentration and toner supply time, and FIG. 3 is a relationship between detected toner concentration value and image density. An explanatory diagram showing. FIG. 4 is a time chart showing the operating principle of an example of control of the image density control device for a copying machine according to the present invention. FIG. 7 is a time chart showing toner supply control. Explanation of symbols i ---------・Developer 2 ---------
−・Developer transport plate 3−・−・Aluminum roll 4・−−
-1--Rubber magnet 5--Sleeve 6a--Earling regulating plate 6b--
------・Magnet 7a for spike control plate----1.--Light emitting element 7b-----1 Light receiving element 70
--- Conductive glass 7d --- Conductive glass bias bracket 8 a --- = --- Scraper 8 b --- - Scraping magnet 9 --
--------- Magnet roll lO・--m----・
Trimmer plate 11-----・Development density detection section 12--・Detection section drive power supply 13--------・Disben smoke. 14-- Power supply 14a ・-= NESA bias power supply 14b-
- Roll bias power supply 15 ------- - Paddle roll 16 - - Control unit 17 - Development noise power supply 17a ------- - Charger power supply 1
8--・--・-・Developer roll 19----------Charger 20-------Photoconductor patent patent issued
Applicant Fuji Zero Nox Co., Ltd. Agent Patent Attorney
Shin Matsubara 2 Same as Kiyoshi Muraki Replaced
Same as above Atsushi Shima - Same as Hiroshi Sakai Figure 2 Figure 3 Figure 3 Hatake I Ranietomo Figure 5

Claims (3)

[Claims] (1) An image density control device that controls image density based on a detected value of toner density of a developer containing magnetic carrier and toner, comprising: a first control means that controls toner density according to the detected value; 1. An image density control device for a copying machine, comprising: second control means for controlling a copy parameter that affects image density according to a value. (2) The image density control device for a copying machine according to claim 1, wherein the second control means controls a developing bias voltage of a developing machine as the copy parameter. (3) The image density control device for a copying machine according to claim 1, wherein the second control means controls a charging potential of a charger as the copy parameter.