JPH028873A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To stably control a mixing rate by measuring the amount that toner is used for a picture signal in synchronization with the timing when the picture signal forms an electrostatic latent image and instructing toner replenishment based on the measured value. CONSTITUTION:A toner consumption measuring means and a CPU 33 as a toner replenishment instructing means generate timed sequence, measure exhausted toner and control toner replenishment. The toner is actually used when a picture electrical signal, converted into optical energy, is projected on an electrified photosensitive body; therefore the measurement of exhausted toner is synchronous with the timing of electrification. As a result, a sensor is not needed to detect toner concentration, whereby cost is reduced. In addition, toner is measured every time it is used, thereby carrying out stable control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electrophotographic apparatus, and particularly to a toner replenishment control device in a developing device using a two-component developer.

[Prior art]

FIG. 4 shows the configuration of a general digital copying device as an electrophotographic device.

In the figure, l is a photosensitive drum, around which a charging charger 11, an optical system 12, a developing device 10, a transfer charger 13, a separation charger 14, and a cleaning unit 15 are arranged in the order of image forming process. 16 is a manual feed table, 17 is a paper feed cassette, 18 is a paper feed roller, 19
2 is a transport fan, 20 is a main motor, 21 is a fixing unit, 22 is a scanner power supply fan, 23 is a polygon mirror 24 is an image reading plate (COD), 25 is a lens, 2
6 is a fluorescent light. In addition, the image reading plate 24° lens 2
5. The fluorescent lamp 26 constitutes an original scanning and electric image signal conversion means, and the polygon mirror 23 constitutes an electrostatic latent image forming means. The operation of this copying apparatus is well known and will therefore be omitted.

FIG. 5 is an enlarged view of the developing device 10. The outline of the developing device 10 will be explained based on this figure. In the two-component development method,
The toner and carrier in the stirring roller 6 must always be mixed at a constant ratio.

The optimum weight ratio of toner to -i is about 2 to 3%. The toner and carrier mixed within the stirring roller 6 are called a developer, and this developer is conveyed to the photoreceptor 1 by the developing roller 3. At this time, the black electrostatic latent image on the angry light body 1 (
For color toner, the toner is attached to the area (of that color). Meanwhile, the carrier returns to the stirring roller 6 again. Therefore, the weight ratio of the toner decreases by the amount of toner developed onto the photoreceptor 1. If this operation is repeated, the toner weight ratio falls below the optimum range, so the toner replenishing roller 8 is rotated to replenish a -1 constant amount of toner.

2 is a doctor for making the thickness of the developer layer on the developing roller 3 constant; 4 is a conveying screw; 5 is a stirring separator; 7
9 is an agitator, and 9 is a toner cartridge.

By the way, conventionally, a photosensor has been used to detect the toner concentration in the developer.

However, this method has the drawback that the sensor is easily soiled, and if it becomes soiled, the mixing ratio of toner and carrier cannot be controlled. Another known method is the F sensor method, in which a developer containing toner and carrier is passed through a coil and the mixture ratio is detected by changes in coil inductance, but this method requires a complicated configuration of the sensor section and sensor control section. The disadvantage is that it becomes expensive.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide an electrophotographic apparatus that is capable of stable mixing ratio control with a simple configuration.

〔composition〕

For this purpose, the present invention provides means for scanning a document and converting the content into an electrical image signal, means for forming the converted electrical image signal as an electrostatic latent image on a photoreceptor, and stirring toner and carrier. In an electrophotographic apparatus having a developing means for depositing toner on the latent image, a measuring means for measuring a toner consumption portion of the image signal in synchronization with the electrostatic latent image forming timing of the image signal, and a measured value. The present invention is characterized in that it has a command means for issuing a toner replenishment command based on.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a control block diagram, FIG. 2 is a timing chart, and FIG. 3 is a flow chart.

Unlike the conventional example in which the concentration of developer is detected by a sensor, the present invention is characterized in that the amount of toner consumption is detected and toner replenishment is controlled.

Now, set the initial value of toner to T (initial) and toner supply roller 1.
The amount of rotational replenishment is T (one rotation), the amount of toner consumed per one electrical image signal is T (one dot), and the lower limit of the appropriate toner density is T (lower limit).

Toner is actually consumed when the electrical image signal is converted into light energy and irradiated onto the charged photoreceptor l. Therefore, it is necessary to synchronize toner consumption measurement with the charging timing.

In the timing chart of FIG. 2, the period when the charger 11 is ON is the latent image formation period as shown in (1), but as shown in FIG. Since the system 12) is shifted, a coefficient force untage signal (2) is generated that is shifted by a certain time.

In FIG. 1, timing generation, toner consumption measurement, and toner replenishment control are performed by the CPU 33, which serves as toner consumption measurement means and toner replenishment command means. 3I is a reference clock and an image electric signal.

A gate 32 is a counter to which a counter gate signal is input.

By the way, the toner density of a two-component developer is determined by the weight of the toner.
From wt and the weight Wc of the carrier, it is determined as W t + W c .

Normally, the concentration is controlled to be maintained at a value close to the optimal concentration (hereinafter referred to as a set value). However, toner replenishment at the time of image formation is unfavorable for image formation, so toner replenishment is performed at an unfavorable time for image formation. Since it is not possible to always maintain the set value in this way, the concentration is controlled within a certain range. At this time, the lower limit value is the value at which it would be problematic if the concentration were to become lower than this.

The process will be explained below according to the flowchart shown in FIG. First of all, the initial toner density (initial! IJI 9M degrees) is set (Sl; same as step 1 and below). The initial concentration is (1
Although determined by WL and Wc in the equation ), initially a developer called an initial agent mixed to a predetermined concentration (at the time of shipment from the factory) is used. Therefore, the initial settings may be performed when adding the initializing agent (when installing the machine and when replacing the agent). At other times, the weight lWc of the carrier does not change, so the density of the toner is determined by the weight W of the toner.

Next, the amount of toner consumed on one sheet of transfer paper is measured as the aforementioned T (consumption) (S2). Therefore, the toner weight after developing one sheet of transfer paper is Wt = Wt - T (consumption), and the density at this time is calculated from equation (1) (S
3). This calculated value is compared with the lower limit value mentioned above, and if it is larger than this (darker), nothing is done and preparation is made for the next image formation, and if it is smaller than the lower limit (lighter), it moves to the next step (S4). .

The next step is toner replenishment. Toner replenishment is performed by rotating the toner replenishment roller 8 (F'), but at this time, the toner replenished with one rotation of the roller is
(one rotation), which is an approximately constant amount. Therefore roller 1
The amount of toner after rotation is Wt=wt+T (1 rotation), and the density after replenishment is calculated from equation 11 (S5
).

This step is repeated until this calculated value becomes thicker than the set value (?ffi<), at which point toner replenishment is finished and preparations are made for the next image formation (S6).

The above control is performed when the development of one sheet of transfer paper is completed, and for example, the CPU 33 is performing other work during the period other than this.

Further, in S2, 34, 35, and 36, predetermined variables and constants, such as Wt of the initial agent.

Wc, toner supply IT (1 rotation), etc. are stored in the ROM.

Further, instead of calculating the toner amount and density by calculation inside the CPU 33, storing the relationship between the toner amount and density in the ROM can be used to improve calculation speed.

The above is an example using the CPU33, but the CPU
In addition to the processing using the 33 software, a hardware device is also possible, and the work contents are the same as those shown in the flowchart. Also, the same effect can be obtained by making small changes to the flowchart.

〔effect〕

As described above, according to the present invention, a sensor is not required to detect the toner concentration, so the cost can be reduced, and since measurement is performed every time toner is consumed, stable control can be performed.

[Brief explanation of the drawing]

1 is a toner replenishment control block diagram of an electrophotographic apparatus according to the present invention, FIG. 2 is a timing chart thereof, FIG. 3 is a flowchart thereof, and FIG. 4 is a side view showing a schematic configuration of a digital copying apparatus. FIG. 5 is a side view of the main part of the developing section. 10... Developing device, 24... Image reading plate, 23
...Polygon mirror, 25...Lens, 26...
Fluorescent light, 33...cpu. t2 no N FF Fig. 2 Fig. 3

Claims (1)

[Claims] means for scanning a document and converting the content into an electric image signal; means for forming the converted electric image signal as an electrostatic latent image on a photoreceptor; In an electrophotographic apparatus having a developing means for depositing a toner, the electrophotographic apparatus includes a measuring means for measuring a toner consumption portion of the image signal in synchronization with the electrostatic latent image forming timing of the image signal, and a toner replenishment command based on the measured value. An electrophotographic apparatus characterized in that it has a command means to perform a command.