JPS6020118Y2 - Development electrode bias application device in electrophotography - Google Patents

Description

[Detailed description of the invention] This invention is a method of applying a bias to the developing electrode in an electrophotographic copying device, and the bias is switched in the non-exposed area (the area that is charged or the image is not exposed), and the bias is applied via a resistor or capacitor. It is characterized by being grounded.

Generally, as one measure to prevent toner loss in non-exposed areas, a method has been conventionally used in which the bias applied to the developing electrode is switched and a high voltage is applied in order to prevent toner from adhering to the non-exposed areas of the photoreceptor.

In order to obtain the above effect, the high voltage is required to be at least higher than the potential of the surface of the photoreceptor, and is 800 to 90
0v was being applied.

For this reason, as a bias power source, a power source for applying a high potential to the non-exposed area in addition to the bias potential for the image exposure area (image area) is required.

However, it has the drawback of significantly increasing power supply costs.

The present invention aims to improve the drawbacks of the prior art described above, and aims to achieve the effect of sufficiently preventing toner loss in non-exposed areas while using a low-cost power source.

In particular, we focused on the phenomenon in which a potential is generated in the rotating developing electrode simply by driving the magnetic brush developing device containing developer. The developing electrode is grounded via a resistor or capacitor selected so that the sum of the potential induced by the photoreceptor potential is slightly higher than the potential of the non-exposed portion of the photoreceptor.

Conventionally, the potential induced in the developing electrode by the charge on the surface of the photoreceptor was considered to be the self-bias potential of the developing electrode, but the self-bias of the magnetic brush development electrode is induced in the developing electrode according to the potential on the surface of the photoreceptor. It has been found that in addition to the potential generated at the rotating developing electrode by driving the developing machine, the potential generated at the rotating developing electrode is added.

As a result, when a magnetic brush developing roll electrode is simply floated in the non-exposed area, the cause of carrier adhesion to the photoreceptor is that the self-bias applied to the developing roll electrode is greater than necessary than the potential of the unexposed area of the photoreceptor. It became clear that this was due to the above-mentioned two-dimensionality of self-bias.

As mentioned above, the present invention relates to a self-biased developing electrode for non-exposed areas, which effectively utilizes the potential generated by driving the developing machine and effectively controls the potential induced by the potential of the photoreceptor of the developing electrode. be.

In order to clarify the present invention, the present invention will be explained using a mathematical formula: R1 is the resistance of the developer, R2 is the grounding resistance, and V is the potential generated by driving the developing electrode that is grounded through the resistance.

, when the charging potential of the photosensitive drum is VDRUM, the potential vR of the developing electrode roller grounded through a resistor (that is, the self-bias potential in the non-exposed area) is 1-g3-VDRUM10V.

■R-R1+R2 it is conceivable that, If the grounding resistance is selected so that ”=0.9, then V.

The self-bias applied to the developing electrode when R1+R2 is 300V to 400V is as shown in FIG. 2<A1-A! Indicated by characteristics.

In the figure, the horizontal axis represents the photoreceptor surface potential VDRUM, and the vertical axis represents the induced potential (8) of the developing roller electrode via the resistance.

. Similarly, the capacity of the developer is C1, the capacity of the grounded capacitor is C2, the potential generated by driving the developing electrode grounded via the capacitor is Vc, and the increased potential of the photosensitive drum is V.
In the case of DRUM, the potential VR of the developing electrode roller grounded via a capacitor (that is, the self-bias potential in the non-exposed area) is VR''' VDRUM+V.

C1+C2 it is conceivable that.

If you choose a capacitor so that -9-=0.9, C□+
02 VR=0.9V, RUM+V.

The relationship between VDRUM and VR is the same as in the case of resistance grounding.

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG.
, b consists of a relay contact R.

In this configuration, when the image area of the photoreceptor 5 passes through the magnetic brush developing roller, the developing roller 4 is connected to the power supply side 1 through contact a, but when the non-exposed area of the photoreceptor passes through the developing roller, The relay 3 is operated by a signal from the copying machine 6, and the developing roller is grounded through the resistor 2 through the contact point.

The signal from the copying machine that operates the relay includes a program that operates each device of the copying machine, a document size detection signal,
Alternatively, there is a detection signal of the potential on the photoreceptor.

The image developed by this developing roller has no fog, and in the non-exposed area, toner does not adhere to the photoreceptor, preventing toner loss. At the same time, the self-bias potential of the developing electrode is higher than necessary. It is also possible to prevent development in which carrier particles adhere to the surface of the photoreceptor due to excessive development.

It goes without saying that a similar effect can be obtained when a capacitor is used in place of the resistor 2.

As mentioned above, the method of the present invention can achieve the desired purpose by simply adding a resistor or capacitor via a relay connected in parallel to a conventional bias power supply, and it is not necessary to add a conventional high voltage power supply. This method has the effect of being much simpler than other methods.

[Brief explanation of the drawing]

FIG. 1 shows an electrophotographic developing electrode bias application device showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between the surface potential of the photoreceptor and the induced potential of the developing roller electrode via resistance. Symbols in the figure: 1...Bias power supply, 2...
・Resistor, 3... Relay, 4... Magnetic brush developing roller, 5... Photoconductor, R...
・Relay contact.

Claims (1)

[Scope of utility model registration request] A developing electrode, a power source for applying bias to the developing electrode, a resistor or capacitor that is in parallel with the power source and one end of which is grounded, and when the photoreceptor surface of the image exposure area passes through the developing electrode, the power source and the non-exposed area It is characterized by having a switching means for connecting the developing electrode from the power source to the resistor or capacitor so that a higher developing electrode potential (than the potential of the non-exposed part of the photoreceptor) is obtained when the photoreceptor surface passes through the photoreceptor. Development electrode bias application device for electrophotography.