JPS5833551B2 - Denshisha Shin Fukushi Yakiniokeru Auto Bias Genzohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an auto bias developing method in an electrophotographic copying machine, in particular, detecting the surface potential of a photoreceptor that enters a developing section after being charged and exposed via a developer, and , an operational amplifier adds and calculates a potential of several tens of volts that does not cause background stains on the copy, and the output is applied to the developing electrode to remove the non-image area (
The present invention relates to an auto-bias developing method in an electrophotographic copying machine that prevents toner particles in a developer from adhering to the background (background area).

By using such an auto-bias development method, a copy image without background stains can be obtained, and there is no need to perform fine adjustment of the exposure amount, and the exposure knob can be changed in stages in 2 to 3 steps using a simple mechanism. It has the advantage of being able to

However, in such an auto-bias development method in which the surface potential of the photoreceptor is detected by a detection electrode through a high-resistance developer, a voltage added by several tens of volts is applied to the development electrode by an auto-bias calculation circuit. Therefore, if the detection electrode is provided near the development electrode, the bias voltage applied to the development electrode will leak to the detection electrode, increasing the detection potential.

In addition, in order to reduce the influence of leakage current on the detection electrode,
The detection electrode is placed on the photoconductor entrance side, away from the development electrode,
If an insulator is used between them, the detection potential can be made to match the photoreceptor surface potential, but since no bias voltage is applied to this insulator in the developing section, the electrostatic latent image may not reach the non-image area. It is not possible to prevent adsorption of toner particles, resulting in a copy image with a smeared background.

Therefore, recently, the detection electrode is moved a certain distance away from the development electrode, and a guard electrode is provided in the insulator part so as to surround the detection electrode, and the current leaking from the development electrode is passed through the guard electrode and then Techniques have been proposed to prevent water from flowing in.

Conventionally, the method of applying voltage to the guard electrode was to connect it to the ground or apply a constant voltage within the detection potential operating range, but the detection potential V.

As shown in Figure 1, when grounded, the symbol A
As shown in , when the photoreceptor surface potential Vs is lower than that and a constant voltage vk (100 volts) is applied, the symbol B
As shown in , the photoreceptor surface potential Vs is detected to be high (in a range lower than the constant voltage Vk) and low in a higher range.

Therefore, in the conventional method, the photoreceptor surface potential is not accurately detected, and as a result, the difference between the photoreceptor surface potential and the development potential, that is, the effective bias voltage acting on the toner particles is not always constant, and the auto bias I was unable to perform my functions to the fullest.

Therefore, an object of the present invention is to provide an auto-bias developing method as described above, in which the detection electrode faithfully detects the surface potential of the photoreceptor, so that the auto-bias function can be fully exerted. There is a particular thing.

The present invention will be described below with reference to the drawings.

FIG. 2 is a schematic end view of a developing device to which the present invention is applied, in which a photoreceptor 1 has a photoconductive insulating layer 1a on its surface,
An electrostatic latent image is formed there through a charging and exposure process.

The developing plate is composed of a detection electrode section 2 and a development electrode section 3, each of which has an upper surface along the circumferential surface of the photoreceptor 10, and the detection electrode section 2 is disposed on the entrance side of the photoreceptor 1. A developer supply port 4 is formed between the two with a fixed interval.

As shown in FIG. 3, the detection electrode section 2 includes an insulating substrate 5.
Guard electrodes 7, 8 and 9 are arranged at intervals on the upper surface of the sensor, surrounding the detection electrode 6.

The developing electrode section 3 is formed by forming a conductive film on the entire upper surface of a single conductive plate 10 or an insulating substrate.

The detection electrode 6 is connected to the input side of an impedance conversion circuit 110 such as a field effect transistor, and the guard electrodes 1, 8 and 9 are connected to the output side of the impedance conversion circuit 11 as well as the voltage summing operational amplifier 120.
Connected to the input side.

Further, the output side of the operational amplifier 12 is connected to the developing electrode 10.

Note that numerals 13 and 14 indicate power supply units of the impedance conversion circuit 11 and the operational amplifier 12, respectively.

In FIG. 2, when the photoreceptor 1 with an electrostatic latent image formed on its surface enters the developing tray, the developer 16 stored in the developer tank 15 is drawn up from the developer supply port 4. Thus, the space between the surface of the photoreceptor 1 and the upper surface of the developing plate is filled.

Here, the photoreceptor surface potential is detected by the detection electrode 6 via the developer, but as mentioned above, if this detection potential is added several tens of volts using an operational amplifier and output to the development electrode, the developing Current leaks from the electrode to the detection electrode, increasing the detection potential.

In this embodiment, the high impedance detection potential detected by the detection electrode 6 is transferred to the impedance conversion circuit 1.
1, the impedance is converted to low impedance and a potential of the same value as the detection potential is applied to the guard electrodes 7, 8, 9, etc. Therefore, the current leaking from the developing electrode 10 does not flow to the detection electrode 6 and is applied to the guard electrodes 7, 8, 9, etc. electrode? , 8, 9, etc.

Therefore, the detection electrode 6 can faithfully detect the surface potential of the photoreceptor without being affected by noise from the development electrode 10, and the operational amplifier 12 adds a predetermined potential to the surface potential of the photoreceptor. If the output voltage is output to , the developing electrode 10 can always exhibit a stable auto-bias function.

FIG. 4 shows the photoreceptor surface potential VS and detection potential V in the above example.

In the diagram showing which relationship, when the photoreceptor surface potential Vs is 100V, the detection potential V detected by the detection electrode.

1 oov was also detected, indicating that the detection electrode was faithfully detecting the photoreceptor surface potential.

Therefore, even if a guard electrode is used in the same way, compared to the case where the guard electrode is connected to the ground as shown by symbol A in Figure 1, or the case where a constant voltage is applied to the guard electrode as shown by symbol B, this This shows that the case where the impedance-converted detection potential according to the invention is applied to the guard electrode is far superior in faithfully detecting the photoreceptor surface potential.

As described above, according to the present invention, the surface potential of the photoconductor that enters the developing section after being charged and exposed is detected by the detection electrode via the developer, and this detection potential is determined by the operational amplifier to an extent that does not cause background stains on the copy. An electrophotographic copying machine that prevents toner particles in a developer from adhering to non-image areas of an electrostatic latent image formed on the surface of a photoreceptor by adding the potentials of and applying the output to a developing electrode. In the auto bias development method, a guard electrode is provided around the detection electrode that detects the surface potential of the photoreceptor, and a potential of the same value is applied to this guard electrode by converting the detection potential detected by the detection electrode into a low impedance. As a result, the photoreceptor surface potential can be detected faithfully, and the auto bias function can be fully utilized, eliminating the need for fine-tuning the exposure amount and allowing the exposure knob to be adjusted in 2 to 3 steps. This improves operability for the user and always provides clear copies with no background smudges.

[Brief Description of the Drawings] Fig. 1 is a diagram showing the relationship between the photoreceptor surface potential and the detected potential in a conventional device using a guard electrode, and Fig. 2 is an example of a developing device to which the present invention is applied. a schematic end view showing
FIG. 3 is a perspective view showing the developing tray in the above embodiment, and FIG. 4 is a diagram showing the relationship between the photoreceptor surface potential and the detected potential in the above embodiment. 1... Photoreceptor, 2... Detection electrode section, 3
...Development electrode part, 5...Insulating substrate,
6...Detection electrode, 7゜8.9...Guard electrode, 10...Development electrode, 11...
Impedance conversion circuit, 12... Addition operational amplifier, 13, 14... Power supply section.

Claims (1)

[Claims] 1. The surface potential of the photoreceptor that enters the developing section after being charged and exposed is detected by a detection electrode via a developer, and an operational amplifier adds a potential to this detection potential to an extent that does not cause background stains on copies. Applying that output to the developing electrode,
A detection electrode that detects the surface potential of a photoreceptor in an auto-bias developing method in an electrophotographic copying machine that prevents toner particles in a developer from adhering to non-image areas of an electrostatic latent image formed on the surface of a photoreceptor. A guard electrode is provided around the photoreceptor, and a potential of the same value obtained by converting the detection potential detected by the detection electrode to a low impedance is applied to the guard electrode, thereby faithfully detecting the surface potential of the photoreceptor. Auto bias development method for electrophotographic copying machines.