JPS6152469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona charging device that charges a surface to be charged by corona discharge.

Conventionally, this type of corona charging device includes a charger in which a corona discharge electrode (corona wire) is provided in a shield case having an opening, and the shield case is arranged so that the opening faces the surface to be charged. A device is known in which a surface to be charged is charged by applying a voltage to a corona discharge electrode to cause corona discharge.

With this structure, if the corona discharge electrode deteriorates or becomes dirty, uneven charging will occur on the surface to be charged.

Therefore, in order to prevent this uneven charging, conventional methods include charging using multiple chargers, narrowing the opening width of the shield case to make the corotron beam uniform, and connecting the charger and the surface to be charged. Methods have been developed to increase the distance.

However, these methods have disadvantages such as requiring a large installation space and requiring a large corotron power supply voltage to be applied to the corona discharge electrode, as well as being insufficiently effective in preventing charging unevenness due to deterioration of the corona discharge electrode and dirt. It has the following defects.

The present invention was made in view of the above circumstances, and its purpose is to provide a corona charging device that reliably prevents charging unevenness caused by corona discharge electrode deterioration, dirt, etc., and can uniformly charge a surface to be charged. The goal is to provide the following.

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

The shield case 1 has an insulating bottom wall 2, a pair of side walls 3, 3, and a pair of end walls 4, 4 to form a long box shape with an opening 1a, and corona discharge occurs across the pair of end walls 4, 4. A corotron wire 5 serving as an electrode is stretched to constitute a charger A.

A plurality of conductive plate electrodes 6 are discontinuously embedded in the insulating bottom wall 2 at intervals in the axial direction (longitudinal direction) of the corotron wire 5, and each conductive plate electrode 6 is a variable impedance element 1 consisting of a resistance element 7 and a passive type constant voltage element 8, whose impedance decreases as the current increases.
They are each grounded via 3. Note that the passive type constant voltage element 8 may be a Zener diode, a varistor, or the like.

The corotron wire 5 is connected to a DC corotron power source 9, and the opening 1a is connected to the conductive layer 1.
0, it is disposed so as to face the charged surface 12c (photosensitive layer surface) of the charged member 12 made of the photosensitive layer 11.

Next, the principle of charging operation will be explained.

First, the equivalent circuit of the process of corona discharge of the corotron wire 5 and charging of the charged surface 12a is as shown in FIG.

That is, the DC current i ₀ flowing through the corotron wire 5 is determined by the impedance 2 of the air insulating layer (the air layer between the corotron wire 5 and the charged surface 12a).
0 and the DC current i ₁ flowing to the ground through the impedance 21 of the charged surface 12a and the conductivity grounded through the impedance 22 of the air insulation layer (the air layer between the corotron wire 5 and the bottom wall 2). It can be considered as the sum of the DC current i ₂ flowing through the shield case 1.

Here, if we consider the case where the DC current i ₀ increases by △i ₀ due to abnormal discharge due to deterioration, dirt, etc. of the corotron wire 5, the DC currents i ₁ and i ₂ will increase by △i ₁ , respectively.
The surface potential of the charged surface 12a increases by △i ₂ and the surface potential of the charged surface 12a increases by △i ₁
It increases by △V.

The above ΔV is the cause of charging unevenness in conventional corona charging devices.

However, since the corona charging device according to the present invention is constructed as shown in FIG. 1, the above-mentioned equivalent circuit becomes as shown in FIG. 3.

In FIG. 3, when the DC current i ₀ increases by more than a certain amount, the voltage applied to the variable impedance element 13 increases due to the increase △i ₂ in the DC current i ₂ , which increases at a certain level. The impedance having the above value decreases to a value close to zero, and furthermore, the DC voltage i ₂ increases by the amount of the decrease in the impedance of the variable impedance element 13.

For this reason, the increase △i ₂ ' in the DC voltage i ₂ due to the impedance drop is a current that contributes to uneven charging due to the increase in the DC voltage i ₀ caused by deterioration, dirt, etc. of the corotron wire 5, that is, the DC current. By setting the variable impedance element 13 so that the increase in i ₁ is equal to Δi ₁ , it is possible to prevent charging unevenness on the charged surface 12 a caused by deterioration of the corotron wire 5, dirt, etc.

In other words, due to deterioration or dirt on the corotron wire 5, the DC voltage i ₀ becomes i ₀ +△i ₀ , and the DC voltage i ₁ becomes i ₁ +△
i ₁ , the DC voltage changes to i ₂ +△i ₂ , but at the same time the impedance of the variable impedance element 13 changes, so that a current of i ₂ +△i ₂ +△i ₂ ' flows through the variable impedance element 13. flows. At this time △i ₂ ′=
If the impedance of the variable impedance element 13 changes so that △i ₁ , even if i ₀ becomes i ₀ + △i ₀ , △i ₀ = △i ₂ + △i ₂ ', △i ₁ = 0 Therefore, the current flowing through the charged surface 12a is not changed.

Therefore, the surface potential of the surface to be charged 12a does not change even if an abnormal discharge occurs, and uneven charging can be reliably prevented and uniform charging can be achieved.

In addition, since the structure is simply that a plurality of conductive plate electrodes 6 are provided on the insulating bottom wall 2 of the shield case 1 and the electrodes 6 are grounded via the variable impedance element 13, the structure is simple, compact, and narrow. It can be installed in a small space, and there is no need to increase the size of the power source 9 for the corotron wire 5.

In the above embodiments, it has been empirically found that the appropriate distance between the plate electrodes 6 is approximately 1 mm, and the axial length of the plate electrodes 6 is 8 to 12 mm.

In addition, if the plate electrodes 6 are arranged in the form of a parallelogram as shown in FIG. The impact of

Further, in each of the above embodiments, the plate electrode 6 is provided on the insulating bottom wall 2 (the back surface of the corotron wire 5).
However, as shown in FIG. 5, a U-shaped cross-section unit shield case 1' made of a conductive material is divided in the 5-axis direction of the corotron wire, and an insulating layer 3 is placed between them.
0 may be provided and the shield case itself may be used as an electrode.

As described above, the present invention reliably prevents charging unevenness due to deterioration, dirt, etc. of the corona discharge electrode, and can uniformly charge the surface to be charged 12a.

Furthermore, the structure is simple, compact, and can be installed in a narrow space, and there is no need to increase the power source of the corona discharge electrode 5.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional explanatory diagram showing an embodiment of the present invention, Figs. 2 and 3 are explanatory diagrams of its operation, Fig. 4 is a plan view showing another embodiment, and Fig. 5 is a further different embodiment. It is a partial perspective view which shows an example. 1 is a shield case, 5 is a corona discharge electrode, 6 is a
12a is a conductive plate electrode, 12a is a charged surface, 13
is a variable impedance element.

Claims (1)

[Claims] 1 An opening 1a is provided at a portion surrounding the corona discharge electrode 5 to which a DC voltage is applied and facing the charged surface 12a.
A plurality of conductive parts electrically divided in the axial direction of the corona discharge electrode 5 are provided in a shield case 1 having a A corona charging device characterized in that a variable impedance element 13 formed by connecting a resistor 7 and a passive constant voltage element 8 in series is connected to each of them so that the impedance decreases as the flowing current increases.