JPS61147272A - Toner supply controller - Google Patents

Abstract

PURPOSE:To prevent toner from failing to be charged electrostatically by comparing the signal from a toner concentration detecting means with at least two high and low comparison levels and varying stepwise the amount of toner supplied each time. CONSTITUTION:The concentration of the toner in a developing tank is detected by a toner concentration detector 10 and compared with reference values and when the toner concentration decreases below the low-level-side reference value, toner is supplied to the developing tank 3 by a supplementary roller 9. The supplied toner is agitated and mixed with carriers smoothly by an agitator screw and the supply of the toner raises the toner concentration in the developing tank 3 speedily, so that image density begins to recover. When the toner concentration in the developing tank 3 rises above the low-level-side reference value, the supply pitch of the toner is decreased. Consequently, the newly supplied toner becomes easy to mix with carriers and are charged electrostatically and sufficiently to reduce a scatter of toner as much as possible, thereby improving picture quality and preventing staining.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a toner pollution control device for a two-component developer in an electrophotographic apparatus.

(Prior art) Toner concentration control for two-component developer and developer consisting of toner and carrier is such that toner is replenished when the toner concentration in the developer tank falls below a set level and the toner concentration is raised to the set level. It is carried out as follows.

During this replenishment process, an incorrect amount of toner is replenished at once, so a large amount of uncharged toner that is not mixed with the carrier, that is, floating toner, is generated in the developer tank, and this toner scatters outside the developer tank and is copied. There were problems such as deterioration of quality and contamination of equipment components.

(Objective) In view of these problems, it is an object of the present invention to propose a toner concentration control method that can prevent the generation of uncharged toner.

That is, the feature of the present invention is that, as shown in FIG. 1, the signal from the toner concentration detection means is compared by a comparison means having at least two comparison levels, high and low, to determine the toner concentration level. The present invention is characterized in that the amount of toner supplied at one time is changed in stages by means of adjusting the amount of toner replenishment depending on the amount of toner supplied.

(Structure) Therefore, details of the present invention will be described below based on illustrated embodiments.

FIG. 1 shows a first embodiment of the present invention,
In the drawing, reference numeral 1 denotes a developing unit disposed in contact with the photosensitive drum 2, which consists of a developing tank 3 and a toner replenishment tank 4. A toner concentration detector 9 for detecting the toner concentration based on a change in inductance is disposed below a separator 8 that accommodates the developing sleeve 6 and guides the developer scraped off by the doctor blade 7. A toner replenishment roller 9 is provided at the toner tank connection port 3a of a part of the developer tank 31, and the toner replenishment roller 9 is rotationally driven by a control device, which will be described later, to replenish the unused amount of toner to the developer tank 3. There is. is the above-mentioned control device, which includes an A-D converter 11 that converts the toner concentration signal from the toner concentration detector IO into a digital signal, and compares the output from the converter 11 with two preset reference levels. The toner replenishment roller drive circuit 13 includes a CPU 12 that outputs a signal when the toner replenishment roller 9 falls below a reference level, and a toner replenishment roller drive circuit 13 that drives the toner replenishment roller 9 based on a signal from the CPU 13.

Next, the operation of the apparatus configured as described above will be explained based on the flowchart shown in FIG.

In this case, it is assumed that copying is started in a state where a large amount of toner has been consumed by the if+ copy operations and the toner density in the image tank 3 has decreased significantly.

When the copy button on the main body of the electrophotographic apparatus is pressed, the toner concentration in the developing tank is detected by the toner concentration detector IO and compared with a reference value.

Since the toner concentration is below the low-level reference value, for example 3wt%, a relatively large amount of toner replenishment, for example 10wt% in terms of A31 paper, is encountered, and the replenishment roller 9
The developer tank 3 is replenished with toner. Needless to say, since the amount of toner in the developer is small, the replenished toner is quickly stirred and mixed with the carrier by the stirring screw, and no scattering occurs. As a result of this toner replenishment, the toner concentration in the developing tank 3 rapidly begins to recover to the overprint image density.

When the toner concentration in the developing tank 3 exceeds the low-level reference value due to toner replenishment, the boy's toner replenishment amount of 2wt% in terms of A3 size is selected, and the toner replenishment pitch is reduced to supply more toner. continue. A small amount of newly supplied toner is successively mixed with the carrier and becomes sufficiently charged.

In this way, when the toner concentration reaches the high-level reference value, the toner replenishing roller 9 is stopped and the toner supply is stopped.

When toner consumption progresses due to an increase in the number of copies, and the toner density falls below the high-level standard value, the amount of replenishment at one time is reduced to A.
Toner is replenished little by little at a pitch of 2 wt% in terms of 3rd edition. The small amount of toner supplied is immediately mixed with the carrier and is provided for development in a sufficiently charged state.

FIG. 4 shows a second embodiment of the present invention,
An image density detector 14 consisting of a light emitting element and a light receiving element is disposed downstream of the developing tank 3, and the toner density is detected from the image density of the standard pattern image.

Next, configure 1. The operation of the apparatus will be explained based on flowchart 1 shown in FIG.

When the copy button is pressed, the counter counts the number of copies. When the counted value of the counter reaches a preset value 1, for example 10n+1 (n is a positive integer), a standard pattern (not shown) is exposed to create a standard pattern image on the photosensitive drum 2. The image density of this standard pattern image is detected by the image density detector 14. Needless to say, the image density of this standard pattern image corresponds to the toner density in the developing tank 3. The detected image density signal is compared with two preset levels of reference values. When the toner concentration is below the low-level reference value, a relatively large amount of toner, such as 10 wt% for an A3 size plate, is supplied in one replenishment to quickly restore the toner concentration in the developing tank 3. , continue copying. In this way, when the count value of the counter reaches lOn+1, a standard pattern image is formed again and the toner density is detected. When the toner concentration recovers to exceed the low-level reference value, the amount of toner replenishment at one time is reduced to 2 wt % in terms of A3 size, and toner is gradually replenished into the developing tank 3. As a result, the newly replenished toner is successively stirred with the carrier, sufficiently charged, and used for development. When the count value of the counter reaches 10n+l, the toner concentration is detected, and toner supply is stopped when it reaches the high level reference value. Thereafter, such a process is repeated to replenish toner.

In this embodiment, two toner density levels are set, but it goes without saying that toner replenishment with even finer grains can be achieved by setting three or more levels.

(Effectiveness) As explained in 1-1, according to the present invention, the toner replenishment start level is divided into multiple stages, and as the toner concentration increases, the amount of toner replenishment at one time is reduced. The toner replenished to the toner is easily mixed with the carrier and sufficiently charged, and scattering of the toner is minimized to improve image quality and prevent staining.

Figure 1

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram clearly showing the configuration of the present invention, and FIG.
FIG. 3 is a block diagram of an apparatus showing an embodiment of the present invention.
FIG. 4 is a block diagram showing another embodiment of the present invention, and FIG. 5 is a flow chart showing the operation of the same device.

Claims (1)

[Claims] Toner replenishment control consisting of a means for detecting toner concentration, a comparison means having at least two comparison levels set, and a toner replenishment amount adjusting means capable of adjusting the amount of toner supplied at one time based on a signal from the comparison means. Device.