JPS61182061A - Potential control method of electrophotographic device - Google Patents

Abstract

PURPOSE:To converge the dark part potential of a bright part potential of a photoreceptor to a set potential by measuring the potential of the photoreceptor for plural reference current values, calculating the changing ratio between the current and potential of a corona charger and controlling the corona charger by a control factor corresponding to the changing ratio. CONSTITUTION:The dark part potential is formed by the 1st reference primary corona current to measure the surface potential and the dark part potential is formed by the 2nd reference primary corona current to measure the surface potential. Both the potential values are inputted to a control factor operating circuit 13 to find out the control factor. Then, the difference between the dark part potential of the 1st reference primary coron current and the set dark part potential is calculated by a potential control circuit 14 and a value obtained by multiplying the difference by the control factor is applied to the reference primary corona current to determine the primary corona current and the dark part potential is compensated to the set potential by controlling a high-voltage transformer 15. Even if the corona discharge chracteristics or the charging characteristics of the photoreceptor are varied due to environmnetal change or the deterioration of durability, the dark part potential of the bright part potential of the photoreceptor can be always set to the set potential, so that an always proper picture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a potential control method for an electrophotographic apparatus.

[Prior art]

2. Description of the Related Art Conventionally, electrophotographic apparatuses, particularly copying machines, have used potential control devices that control the dark area potential of a photoreceptor to a preset potential in order to stabilize images. Before image formation, a black magnetostatic latent image is formed using the reference current of the corona charger, and the amount of current of the corona charger is controlled so that the dark area potential becomes a predetermined dark area setting potential. It is something.

Conventionally, this type of control generally measures the first dark area potential with respect to a reference current, determines the difference from the set dark area potential, and adjusts the current it' of the corona charger using a predetermined control coefficient.
The dark potential is adjusted to a set value IC to converge the dark potential. This control coefficient is uniformly determined in advance based on the rate of change between the current amount of the corona band dt device and the dark potential of the photoreceptor.

However, the corona discharge characteristics and the charging characteristics of the photoreceptor are
Since it fluctuates due to the external environment such as temperature and humidity, deterioration due to durability, etc., the current amount of corona charging and the rate of change of the dark area potential also fluctuate.

The target potential control is such that it converges to the set dark potential only when this rate of change matches a predetermined control coefficient.For the reasons mentioned above, changes in the amount of current for corona charging and the dark potential When the rate V(-) fluctuation occurs, the control coefficient and the rate of change no longer match, and there was a point where it became impossible to converge the set potential V.

The above phenomenon applies not only to the dark potential but also to the bright potential.

〔the purpose〕

The present invention has been made in view of the above-mentioned points, and is intended to eliminate the drawbacks of the above-mentioned conventional examples. The present invention aims to provide a potential control method that can converge the potential or bright area potential to a set potential.

〔Example〕

The present invention will be explained below based on one aspect. FIG. 1 is a schematic diagram of an embodiment of an electrophotographic copying machine to which the present invention is applied. 1 is a photosensitive drum, which is a photosensitive member, and is composed of three layers from the surface: an insulating layer, a light guide IJIM, and a conductive layer.
It is rotatably supported in the direction of the arrow shown in the figure. Around the photosensitive drum 1, there are a primary charger 2, a secondary charger 3, a full exposure lamp 4, a position sensor 7, a developing roller 5 of a developing device, a transfer charger 6, and a rotation direction 1111'j r. , and V
A lamp and a charger 8 for static elimination before c are provided.

Next, to explain the operation, the photosensitive drum 1, which has been pre-discharged by the lamp and the charger 8 before each process, is
After the entire surface is uniformly charged by the next charger 2, the reflected light from the original 10 illuminated by the halogen lamp 9 for exposing the original 10 is focused on the photosensitive drum 1 via the mirrors 9a to 9d and the lens 9e. Image. At the same time, the secondary charger 3V removes the charge in accordance with the image of the document, forming a latent image. Subsequently, after the entire surface is exposed by the entire surface exposure lamp 4, the toner is developed by the developing roller 5. An alternating current bias voltage is applied to this developing roller 5v, and the gradation of the image is improved by jumping development. Subsequently, the transfer charger 6 is activated to perform transfer onto recording paper (not shown). After the transfer, toner remaining on the photosensitive drum 1 is removed by a cleaner 11.

Further, a surface potential sensor 7 for measuring the surface potential of the photosensitive drum 1 is provided between the entire surface exposure lamp 4 and the developing roller 5.
The output signal from the surface potential sensor 7 is converted into a signal V (of a predetermined level) by the potential measuring circuit 12.

Before the normal copying process, potential control is first performed.

This is to adjust the corona currents of the primary charger 2 and the secondary charger 3 so that the dark potential and bright potential of the photoreceptor are always at the set potential. Conventionally, as a general method, one belt? Is it the dark side of the standard primary corona of It device 2?
Form the n-position, measure its surface potential, calculate the difference from the set potential, and multiply it by a predetermined control coefficient (rate of change of primary corona current and dark potential) by yc. base r
In addition to the s primary corona current, the dark MI 5%i level was corrected via the potential control circuit 14 and the high voltage transformer 15.

FIG. 2 is a diagram showing the characteristics of dark area potential v vs. corona current 1. The above method will be explained with reference to the direct N a rc in the same figure.
The dark potential V is measured at the reference primary corona current 11, and the difference Vo V from the set dark potential VD is calculated. Then, the current 1 = α (Vo - V, ) + t, which is obtained by multiplying this by the control coefficient α (corresponding to the horizontal axis V (corresponding to the slope) of the straight line a) and the reference primary corona current 1, is 1. The next corona current is determined, and the high voltage transformer 15 is controlled to correct the first dark area to the set voltage VD.

Conventionally, this control coefficient α is uniformly determined in advance, but
For the reasons mentioned above, variations occur in the l--characteristics shown in FIG. 2. This fluctuation is caused by a parallel shift of the straight line a, with the slope α
There is no problem if it remains unchanged, but in most cases the slope also changes. Therefore, for example, if the straight line a fluctuates like a straight line, the dark potential cannot be controlled as it is.

In the present invention, in order to solve this problem, a plurality of first reference primary corona current values 11 and a plurality of second reference primary corona current values 1
．． This is an attempt to make corrections by setting .

Next, the operation will be explained using the basic flow line [Δ in FIG. First, a dark potential is formed using a first reference primary corona current 1, and its surface potential ■ is measured (Step 1
). Next, a dark potential is formed with the second reference primary corona current I, and its surface potential V is measured (step 2).
. Then, the potentials v1 and V are input to the control coefficient value calculating circuit 13 to obtain the control coefficient α (step 3).

(1=(+,-It)/(Vt-Vl) Potential control is performed using the control coefficient αVc obtained here.As described above, the potential control circuit is 1=(It11)/(V,-V,
)-(Vo-V, )+l, VCC The primary corona current is determined and the dark potential is corrected to the set potential Dv (step 4).

By doing the above, from VC, even if the t-V characteristic fluctuates from aha to a straight line in Fig. 2, the new control coefficient β can be calculated as
't) Calculate from the above formula and perform potential control using this control coefficient β. l'=(+t-1t)/(V't-V
't)-(VD-V', )+1. The dark potential is set by determining the primary corona current 'di FE, V n
This is to be corrected.

Therefore, even if the corona discharge characteristics and the charging characteristics of the photoreceptor change due to environmental changes or deterioration due to durability, and the l-V characteristics shown in Fig. 2 change, the dark area potential is always set. It can be corrected to

[Other Examples]

In the embodiment described above, control of the dark area potential of the photoreceptor is explained, but the control of the secondary corona current of the secondary charger 3 can be similarly performed for the bright area potential.

In addition, although the control coefficient was obtained from two reference currents, reliability could be further improved by setting three or more reference currents and then obtaining the control coefficient from the slope of the averaged l-V characteristic straight line. Stable control can be performed.

〔effect〕

As explained above, according to the method It of the present invention, a plurality of reference corona current values are set and control is performed by determining the control coefficient by itself, so that environmental fluctuations and durability deterioration can be avoided.
As a result, even if variations occur in the corona discharge characteristics and the charging characteristics of the photoreceptor, the dark area potential or bright area potential of the photoreceptor can always be corrected to the set potential, so that an appropriate image can always be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic copying machine according to an embodiment of the present invention, FIG. 2 is a corona charging current vs. dark area potential characteristic diagram, and FIG. 3 is a basic flowchart of potential control of the present invention. It is a line diagram. 1...Photosensitive drum (photosensitive member) 2...
...Primary charger 3...Secondary charger 12...Potential measurement circuit 13...Control coefficient calculation Circuit 14...
......Potential control circuit 15...... Flat pressure transformer 〒6-2-1 Step 9F・4

Claims (1)

[Claims] Set a plurality of reference current values, measure the potential of the photoreceptor with respect to each reference current value, calculate the rate of change between the corona charging current and the potential, and adjust the potential to a preset potential. A potential control method for an electrophotographic apparatus, characterized in that the corona charging is controlled by a control coefficient according to a rate of change obtained by the calculation.