JPS6225778A - Picture density control system in electronic photograph device - Google Patents

Abstract

PURPOSE:To make constant a picture density regardless of the history of a developing agent by detecting the number of copies from the time of the exchanging of the developing agent and correcting the picture density in the device to detect the toner concn. and control the supply of the toner. CONSTITUTION:The toner concn. is detected by a sensor 2 of the inductance, and the signal is inputted to an oscillating device 3 and a frequency-voltage converting device 4. Next, a toner supply judging circuit 7 compares the toner concn. detecting signal with the reference voltage, when the density is lower, the signal is inputted to a toner supply member driving circuit 8 and the toner is supplied. When the number of times of agitating is increased for the toner, the signal level is decreased as well as the toner concn. is decreased. Then, a copy counter 10 detects the number of the copies from the time of the exchanging of the toner, counts 9 the developing unit driving time, inputs the correcting signal to a reference voltage adjusting device 6, and corrects the level of the reference voltage for the changing part only due to the number of the times of agitating the toner. Consequently, since the picture density is corrected by the history of the developing agent, the constant density can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application! 7) The present invention relates to a technique for controlling image density in an electrophotographic apparatus using a binary developer.

(Prior Art) The image density of an electrophotographic bag using a two-component developer consisting of toner and carrier is determined based on a signal from a toner density sensor provided in a developing unit. This toner concentration sensor is formed by winding a coil near the discharge port of a funnel-shaped bobbin whose upper part is expanded to provide a toner intake port, and which captures the developer flowing down from the separator in the development unit. , is configured to detect the developer flowing speed, which changes in accordance with the toner concentration, as the inductance of the coil.

Incidentally, the developer is stirred and charged within the developing unit in order to promote adsorption of toner to the latent image formed on the photoreceptor drum, but the band M1. ai: gradually changes depending on the history of the total number of stirrings from the beginning of use. On the other hand, it goes without saying that the flow rate of the developer passing through the bobbin is proportional to the toner concentration, but it also depends on the degree of bonding of the particles with each other depending on the amount of charge of the toner.

Therefore, there is a problem in that the speed of the developer flowing down the toner density sensor is affected not only by the toner concentration but also by the total number of times the developer is stirred, causing the density of the copied image to change from the reference density over time. Ta.

(Purpose) In view of these problems, the present invention provides image density control that allows copies with constant image density to be obtained at all times regardless of the history of the developer by correcting the image density in accordance with the number of copies. The purpose is to provide a method.

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

FIG. 1 shows an embodiment of the present invention, and reference numeral 1 in the figure indicates a toner concentration detection circuit, and a toner concentration sensor 2 detects the toner concentration of the developer as an inductance.
Also constituted are an oscillator 3 for converting signals from the oscillator into a frequency, and a frequency-to-voltage converter 4 for converting signals from the oscillator into a voltage. 6 is base? Is! Base on voltage regulator? T?
! The reference voltage from the voltage generating stone 5 is changed by a signal from an image density correction signal generation circuit 9, which will be described later, to output a corrected reference voltage. 7 is a toner replenishment judgment circuit, and the toner 1st detection signal is the correction base? P! A signal is output to the toner replenishing member drive circuit 8 when the voltage drops below the voltage range. 9 is the image 11 correction signal generation circuit described above;
Copy counter 1 provided in an electrophotographic device
It also includes a developer unit driving time counter 12 which receives a signal from 0 and performs a counting operation and which is reset to zero by a reset switch 11, and a logarithmic converter 13 which converts the output from this to zero.

In this embodiment, the developing units are filled with new developer, and at the same time, the reset switch 11 is operated to reset the developer unit driving time counter 12 to zero. At this time, the developer is running fast, so the toner concentration sensor 2
The speed of the developer that is applied is controlled only by the toner concentration, and since the developing unit driving time counter 12 also has a time value of zero, the image one-time correction signal generating circuit 9
As a result, the reference voltage from the reference voltage generator 5 is directly inputted to the toner replenishment judgment circuit 7 without being corrected by the reference voltage regulator 6, and the toner density is set to the initial setting. The developing unit is replenished with toner until the specified density is reached. If the copying operation is performed at this point, the apparatus operates under its original operating conditions, and copies with excellent image quality can be obtained.

When a large number of copies are made in this way, the number of copies from the time of developer replacement, that is, the total time the developing unit has operated, is determined by the developing unit driving time counter 1.
It will be added up to 2.

In this way, as the number of copies increases and the number of times the developer is stirred increases, the speed of the developer that moves down the toner concentration sensor 2 begins to decrease in proportion to the logarithm of the number of times the developer is stirred, as described above, and the toner concentration increases. The signal level from the toner concentration detection circuit 1 decreases in the same manner as the decrease in the signal level (Figure 3).
On the other hand, at this point, the count content of the developing unit drive time counter 12 is gradually increasing, so the image density correction signal generation circuit 9 generates a correction signal representing the logarithm value of the total usage time of the developer. Output to the reference voltage regulator 6 and set the base voltage to the reference voltage regulator 6. The reference voltage from the F1 voltage generator 5 is reduced in proportion to the logarithm of the total usage time and output to the toner replenishment determining circuit 7. As a result, the comparison level of the toner replenishment determining circuit 7 is lowered by the amount of variation caused by the number of times the developer is stirred, and toner is replenished based on the actual toner concentration within the developing unit.

Hereinafter, the standard level of toner replenishment is corrected in proportion to the logarithm of the total operating time accumulated in the developing unit driving time counter 12 in this way, and the image level is maintained at the standard level (FIG. 3). .

When the developer is replaced due to long-term use, the reset switch 11 returns the counter to zero and the process returns to the above-described process.

FIG. 2 shows a second embodiment of the present invention, in which the reference signal from the reference voltage generator 5 is input directly to the toner replenishment judgment circuit, while the signal from the image density correction signal generation circuit 9 is inputted directly to the toner replenishment judgment circuit. It is designed to be input to the developing sleeve rotation speed control circuit 11.

According to this embodiment, when the toner concentration measurement signal falls below the reference level regardless of the usage time of the developer, toner replenishment is performed and the toner concentration Iff in the developing unit is turned on.
The rotation speed of the developing sleeve gradually decreases in accordance with the driving time of the developing unit, that is, the logarithm of the number of copies, so the relative speed difference with the photoreceptor drum becomes smaller. The amount of toner supplied to the latent image is reduced, and as a result, the copy image density is maintained at the initially set value.

In the above embodiment, the output of the toner immersion level sensor fluctuates depending on the logarithm of the cumulative usage time of the developer. It goes without saying that if the output of the toner concentration sensor varies based on the functional relationship of rA, it is corrected based on this rA quantity relationship.

Furthermore, in the embodiment described above, the total operating time of the developing unit is calculated based on the number of copies, but it is possible to measure the operating time of the developing unit based on the signal from the sequence circuit that controls the main body. Not even.

Furthermore, in the above-described embodiment, the image intensity is adjusted by changing the toner replenishment standard and by changing the rotational speed of the developing sleeve, but other image adjustment means, such as the developing bias voltage It goes without saying that the same effect can be achieved even if the

(Effects) As explained below, according to the present invention, the image density is adjusted in accordance with the total usage time of the developer, so changes in image density due to the usage history of the developer can be avoided. By modifying it, you can always obtain a copy image set to a constant intensity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a device showing one embodiment of the present invention, FIG. 2 is a block diagram of a device showing another embodiment of the present invention, and FIG. 3 is an explanatory diagram showing the operation of the same device. . 1... Toner concentration detection circuit 2... Toner concentration sensor

Claims (1)

[Claims] The developing unit is provided with toner concentration detection means for detecting the concentration of toner contained in a developer consisting of two components, toner and carrier, as a change in inductance, and the toner replenishment is controlled based on a signal from the detection means. An image density control method for an electrophotographic apparatus, characterized in that the number of copies made since a developer is replaced is detected in the photographic apparatus, and an image density adjustment means is controlled based on this number of copies.