JPS60130773A - Image density controller of copying machine or the like - Google Patents

Abstract

PURPOSE:To prevent variation in image quality by detecting a detection frequency based upon inductance having close relation with the property Q/M of a developer, and feeding the detection result back for a development bias and the rotating speed of a developing sleeve. CONSTITUTION:This is a detector which detects the toner density (TC) of a two-component developer as the inductance of a coil 3. The detection frequency fD is different even when the TC is constant. A tone weight-toner charge (Q/M) curve has relation with a TC-fD curve. The fD is detected by a circuit 20 by detecting the inductance of the developer by the coil 3, its detection signal is compared by a comparing circuit 22 with the reference value fD of a generating circuit 21, and a control circuit 23 controls the development bias, developing sleeve rotating speed, etc., on the basis of the comparison result. Consequently, change in image quality with Q/M is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image density control device in a developing device that uses a two-component developer consisting of )/ner particles and magnetic+1 carrier particles.

Outside a copying machine that uses a two-component developer, measure the exact amount M of toner adhered within a specified area and the charge Q of the toner, and compare Q/M and M with A1ζ], The technical concept of controlling toner concentration and developer entrainment energy so that they are the same as the reference value is well known (Utility Model Application Publication No. 58-1).
3544) , -I:: In the prior art, the measuring device for toner weight fi) M and toner mass Q is very much a circular hole, and it is also possible to control toner concentration and stirring energy. However, the value of Q/M does not change suddenly,
High-speed copying machines had drawbacks such as an increased number of defective copies during that time.

Purpose The present invention has been made in order to solve the above-mentioned drawbacks of the conventional 4F method.In particular, the present invention adjusts the developing conditions by detecting the characteristic values of the developer, thereby maintaining constant image quality. It was done for the purpose of

The structure of the present invention will be described below based on examples.

Figure 1 is a block diagram of the main parts of a developing device that uses a method to detect the toner concentration (hereinafter referred to as T and C) of the developer as the inductance of a coil. , 3 is a detection coil, 4 is a stirring member, 5 is a magnet, 6 is a developing sleeve, 7 is a photosensitive drum, and 8 is a toner tank.

FIG. 2 is an electrical circuit diagram showing an example of a T and C detection and toner replenishment control circuit, and 3 in the figure is a coil corresponding to the detection coil 3 shown in FIG.

FIG. 3 shows toner concentration and detection frequency (hereinafter referred to as TC-f o curve), toner concentration and toner charge amount ( This is a diagram showing actual measurement data when the T C-Q/M curve (hereinafter referred to as the T C-Q/M curve) was actually measured. This figure shows that even if T and C are constant, the detection frequency (hereinafter referred to as fo) is different. It means. Also, the TC-Q/M curve is TC-fo
It can be thought that it means that it is related to a curve. In other words, even for -T and C, if the toner charge amount (hereinafter referred to as Q/M) is small, a large amount of developer flows into the detection bobbin, so the inductance becomes large.
fo becomes smaller. On the other hand, when 97M is large, the repulsion due to the charge of the developer particles is large, less developer flows into the detection bobbin, and the inductance becomes smaller.
fo becomes larger.

Generally, the image density and background density in the quality of copies obtained by electrophotography are strongly dependent on 97M, and when 97M is large, the image density is low and the background density is also low. When 97M is small, the image density is high and the background density is also high. Therefore,
To get a good quality copy, you have to keep 97M at a reasonable value. However, it is not only difficult to measure 97M in an actual developing device, but it also changes depending on the environmental conditions (humidity, temperature) in which the developer is placed and the stirring state of the developer, making it difficult to maintain it at an appropriate value. Have difficulty.

FIG. 3 shows that under certain conditions of T and C, the value of 97M can be detected as the value of fo. In the present invention, by detecting the value of fo, the developing power applied to the developing sleeve is adjusted in order to bring the above-mentioned copy quality into an appropriate state.

That is, if fo larger than a predetermined fo is detected, it is determined that the developing bias is greater than 97M, and the developing bias is lowered, and in the opposite case, it is lowered.

Note that instead of adjusting the developing bias, the value of fo is detected and f is larger than a predetermined fo.

If this is detected, the rotation speed of the developing sleeve may be controlled to be increased, and in the opposite case, the rotation speed may be controlled to be decreased, or the developing bias and the sleeve rotation speed may be controlled simultaneously.

FIG. 4 is a diagram showing an example of an electric circuit for implementing the present invention, in which 20 is an FO detection circuit, 21 is a reference FO value generation circuit, 22 is a comparison circuit, and 23 is a developing bias or developing circuit. In the sleeve rotation speed control circuit, fo is detected by detecting the inductance of the developer using a coil, and the detection signal is used as the reference f.

(ilj), and based on the comparison results, the developing bias, developing sleeve rotation speed, etc. are controlled as described above.

As is clear from the above explanation, according to the present invention, it is possible to prevent changes in image quality due to changes in developer characteristics (Q/, M), and in particular, it is possible to prevent changes in image quality due to changes in developer characteristics (Q/, M). By detecting the detection frequency based on inductance, the detection and comparison results are fed back to the developing bias and/or developing sleeve rotation speed, which affect image quality like Q/M, to prevent changes in image quality due to 97M change. I can do it.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a main part configuration of a developing device to which the present invention is applied, FIG. 2 is a diagram showing an example of a T and C detection and toner replenishment control circuit, and FIG. 3 is a diagram showing an example of a toner replenishment control circuit. FIG. 4, which is a diagram of actual measurement data showing the relationship between density, detection frequency, toner density, and toner charge amount, is a block diagram showing an example of an electric circuit used to implement the present invention. l...Developing device, 2...Detection bobbin, 3...Detection coil, 4...Stirring member, 5...Magnet, 6...
・・Developing sleeve, 2O・foo knowledge circuit, 21・・
・Reference fo value light generation circuit 22... Comparison circuit, 23...
・Control circuit. Patent applicant Ricoh Co., Ltd.

Claims (4)

[Claims] (1), ) In a copying machine or the like that uses a two-component developer consisting of toner particles and magnetic carrier particles, the detection section that detects the inductance of the developer is broken, and the output detected by the detection section is compared with a predetermined standard. 4. The development conditions were adjusted by comparing the values. Image density control device with ¥ symbol. (2) The image density control wholesale foil making according to claim 1, wherein the developing condition is a developing bias. (3) The image density 111/2v imaging according to claim (1), wherein the developing condition is the number of revolutions of the image sleeve. (4) The image density control device as set forth in claim (1), wherein the developing condition (+iii) is a developing bias and a rotation number of the developing sleeve 11.