JPS59124361A - Controlling method of toner density for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To prevent a toner density signal from being affected by a copying image density by forming a standard pattern image at the length proportional inversely with a set value of a copied image density, and using the value obtd. by integrating the optical density detection signal of the standard pattern image as the toner density signal. CONSTITUTION:A detecting circuit 1 for the set value of an image density detects the signal for adjusting the image density set by a copying density setter A and outputs the voltage signal of the level proportional inversely to the set density. A voltage-time transducing circuit 2 forms the pulse signal having the width proportional to the signal level from the circuit 1, outputs the same at the point of the time when a scanner starts moving, and disables an erasing lamp driver B during the time corresponding to the pulse width from the circuit 2 in a circuit 3 for putting out the erasing lamp. A detecting circuit 4 for a pattern density exposes a member C for a standard density pattern, samples the signal emitted from a photosensor E detecting the pattern image formed on a photosensitive drum D for a prescribed time, integrates the value and outputs the same to a controller F.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a toner density control method for an electrophotographic apparatus, which controls toner density by detecting a standard pattern image using a photosensor.

(Prior art) - In general, as a method for adjusting the image density of an electrophotographic device, developing bias voltage, exposure light amount, light amount,
Although the amount of charged electric charge is changed, there is a problem in that the density of the standard pattern image for toner density detection also changes. In order to solve this problem, an image density adjustment method has been proposed in which the bias voltage is kept constant when creating a standard pattern image even if the bias voltage is changed during image density adjustment, but the structure is complicated. The drawback was that it was expensive.

(131) The present invention was made in consideration of such circumstances,
The purpose of this invention is to propose an improved toner density control method that is not affected by the toner density value or the copy image density by making the length of the standard pattern image correspond to the change in the copy image density setting (10). do.

(Structure) Therefore, the details of the present invention will be explained below based on examples.

FIG. 1 is a block diagram showing an example of an apparatus used in the present invention, and the symbol in the figure is an image density setting value detection circuit that detects an image density adjustment signal set by a copy density setting device A. The device is configured to output a voltage signal having a level inversely proportional to the set concentration. Reference numeral 2 denotes a voltage-to-hour conversion circuit, which is configured to generate a pulse signal having a width proportional to the signal level from the detection circuit 1 and output it at the time when the scanner starts moving. Reference numeral 3 denotes an erase lamp extinguishing circuit, which is configured to deactivate the erase lamp driver B for a time corresponding to the pulse width from the conversion circuit 2. 4 is a pattern density detection circuit which periodically outputs a signal detected by a photosensor E of a pattern image formed on a photoreceptor drum D by exposing a standard density pattern member C disposed at the home position of the scanner. It is configured to perform sampling over a predetermined time T (FIG. 4), integrate the sampled signal, and output it to the controller F. Note that in the drawing, reference numeral G indicates a toner replenishment member drive circuit that drives a toner replenishment member J provided in the developing unit H based on a signal from the controller F, and K indicates an eraser lamp.

Next, the operation of the apparatus configured as described above will be explained.

Setting the copy density in this apparatus will be explained by taking as an example a method (FIG. 2) in which the developing potential is adjusted by changing the developing bias potential, that is, the potential difference between the surface potential of the photosensitive drum and the developing bias potential.

Now, before copying, when the copy density setting device A is operated to set the standard density, the development potential is adjusted to a corresponding value (Fig. 2). This potential is detected by an image density setting value detection circuit 1, and is converted by a voltage-to-time conversion circuit 2 into a time corresponding to this image density.

In this state, when the copy start button is pressed, the scanner starts scanning the pattern member C, and at the same time, the erase lamp extinguishing circuit 3 is activated to turn off the erase lamp K.
The light is turned off and a pattern image begins to be formed on the surface of the photoreceptor drum. After the time converted by the voltage one-hour conversion circuit 2 has elapsed, the erase lamp K is turned on again and the formation of the pattern image is stopped for 6Jl (FIG. 3A).

The pattern image formed in this way is
As a result, the W4 image is converted into an output voltage at a level proportional to the density by the photosensor E, and is input to the pattern density detection circuit 4. This output voltage is sub-ringed at regular intervals in the concentration detection circuit 4 as shown in FIG. The controller F compares this i1r1 with the set jxl value)
to control the toner concentration in the developing unit H to a constant value.

Next, in order to obtain a low-density copy, the copy density setting device A is adjusted and the development potential is set to a low value.
A long time that is inversely proportional to this is set in the voltage-to-hour conversion circuit 2. When copying is started in such a situation, the erase lamp K is turned off, and the erase operation is inactive for a long time compared to the standard density described above, forming a pattern latent image that is long in the circumferential direction. (Figure 3B). This latent image is visualized by attracting toner with a richness corresponding to the development potential, and is detected by the sensor H.

This signal is sampled at regular intervals in the concentration measuring circuit 4, and the individual sampling values IDn are integrated (FIG. 4B). Needless to say, since this pattern image is formed long in the circumferential direction of the photoreceptor drum,
The number of samplings increases in accordance with the length of this image, and becomes equal to the aforementioned integrated value ΣIDm of standard image density. Therefore, the toner density signal is not affected by the copy density, and erroneous toner replenishment due to changes in the density of the pattern image will not occur.

In this embodiment, the copy density is adjusted by the development potential, but it goes without saying that the exposure light can also be applied by changing the amount of charged electric charge. In addition, in this embodiment, erasing from the start of scanning of the pattern member is disabled and the circumferential length of the pattern image is adjusted, but from the time when the remaining length of the pattern member reaches a predetermined value The erase operation may be disabled, and furthermore, in this embodiment, the discrete signals obtained by sampling the signals from the photosensor that detects the pattern image at a constant cycle are integrated. , the same effect can be obtained even if the integration is performed continuously over the entire length of the pattern image.

(Effects) As explained below, according to the present invention, the circumferential length of the density detection pattern image on the photoreceptor drum is changed according to the copy image density setting value, and the pattern image density is integrated. Since the toner density signal is configured to do this, the toner density signal is not affected by changes in the copy density, and the l·toner density can be precisely controlled.

[Brief explanation of the drawing]

1 is a configuration diagram of the apparatus used in the present invention, and FIG. 2 is an explanatory diagram showing the relationship between phenomenon potential and image density.
FIGS. 3 and 4 are explanatory diagrams showing the operation of the same two apparatuses, and show the relationship between the set copy density and the length of the standard pattern image, and the relationship between the density of the standard pattern image and its circumferential length, respectively. It represents a relationship. A...Copy density setting device 4...Pattern density detection circuit Applicant Rico Co., Ltd. - Agent Patent attorney Kei Nishikawa Katsuhiko Kimura 1 Figure h Figure 2 Figure 3 Figure 4 figure

Claims (1)

[Claims] In a method of controlling the toner concentration in the developer by detecting the optical density of a standard pattern image formed at a position outside the original image forming area of the photosensitive drum, forming the standard pattern image;
1. A toner density control method for an electrophotographic copying machine, which comprises integrating an optical density detection signal of the standard pattern image and using the resulting value as a toner density signal.