JPH04159589A - Destaticization method and electrostatic charging state measuring method for electrostatic charged body - Google Patents

Abstract

PURPOSE:To expand a destaticization setting area, to unnecessiate the decomposing/absorbing device of ozone, and to miniaturize by applying the damping alternating voltage of a specific frequency to a non-electrostatic charge body and destaticizing. CONSTITUTION:When a conductive electrode 3 is brought into contact with the surface of an electrostatic charged body 2, a voltage is applied between the electrostatic charged body 2 and the conductive electrode 3, the both are moved at a relative velocity (v)mm/sec relatively, and the surface of the electrostatic charged body 2 is destaticized, the applied voltage is the damping alternating voltage that its peak value is more than the electrostatic charge starting voltage toward the electrostatic charged body 2 as well as which is applied by a frequency f(Hz), v/f<=0.1(mm). Thus, the high voltage is not necessary such as a corona discharger, and it is possible to destaticize the electrostatic charged body 2 without generating the ozone at the comparatively low voltage, and to measure a potential by electrification having a slight irregularity of the electrostatic charged body 2 by a simple configuration.

Description

[Detailed Description of the Invention] The present invention relates to a paper conveying belt used in an image forming apparatus,
The present invention relates to a method for removing static electricity from a charged object such as a transfer belt, a transfer drum, and a photoreceptor, and a method for measuring the charged state of the charged object after static electricity removal.

[East 11] In image forming devices such as electrophotographic copying machines, dielectric films such as transfer belts and transfer drums are used to attract and convey transfer paper, but these dielectrics become electrically charged during the transfer process. A static eliminator is always required. Conventionally, as a static eliminator for this purpose, a thin wire type corona discharger consisting of a wire electrode stretched within a shield electrode has been used.

However, static eliminators using corona dischargers have the following problems.

a) It is necessary to superimpose a DC voltage of the opposite sign to the potential on the surface of the charged member on the alternating high voltage of 3 to 6 KV to the necessary wire electrode in the palace, to prevent leakage to the electrode and main body. Therefore, in order to maintain a large distance from the wire to the shield electrode, the discharger itself becomes large, and it becomes essential to use a highly insulated cable.

b) Most of the discharge current from the wire flows to the shield electrode.

C) Corona ~ Raw corona discharge generates ozone, etc., which tends to cause oxidation of equipment components.Also, considering the effect of ozone on the human body, we recommend using ozone absorption, decomposition filters, and fans as airflow generation means. Requires.

d) Kufu brain! The high electric field formed on the surface of the wire collects dust inside the device, stains the surface of the wire, causes uneven discharge, and causes uneven charge removal on the charged object.

In addition, it is necessary to measure the charged state of the charged object in order to know whether the charged object has been completely neutralized by the static eliminator, but conventional measurement methods measure the average potential. Although a sensor was used, it was not possible to measure the electrified 4th position, which had minute unevenness.

In view of the above-mentioned problems of the conventional method for removing static electricity from a charged object of an image forming apparatus and the method for measuring the charging state of the charged object after static electricity removal, the present invention has been proposed to provide a method for removing static electricity from a charged object in an image forming apparatus, and a method for measuring the charged state of the charged object after static electricity removal. A method for efficiently removing static electricity from a charged object at a relatively low voltage without requiring high voltage or generating ozone, etc., and measuring the charging potential of a charged object with minute irregularities using a simple configuration. The objective is to provide a method to do so.

In order to solve the above-mentioned problems, the method for removing static electricity from a charged object according to the present invention includes: bringing a conductive electrode into contact with the surface of the charged object, and applying a voltage between the charged object and the conductive electrode. the relative velocity v
In a static elimination method in which static electricity is removed from the surface of a charged object by relatively moving it at am/sec, the peak value of the applied voltage is equal to or higher than the charging start voltage for the charged object, and the frequency f () Iz) is v It is characterized by an alternating voltage given by /f<0.1 (dragon).

The method of measuring the charged state of the surface of a charged object according to the present invention is characterized by bringing a dielectric into contact with the surface of the charged object and measuring the attractive force acting on the dielectric.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the effects of the present invention will be explained in detail based on embodiments with reference to the drawings.

FIG. 1 is a diagram schematically showing a transfer belt using a dielectric endless belt as an example of a charged object to which the static elimination method of the present invention is applied.

The transfer belt 2 is stretched around two rotating rollers 4 and 6, rotates at a linear speed V in the direction shown by the arrow, and attracts the transfer paper 1 fed from the roller 4 side to the upper running section. Transfer belt 2
The toner image formed on the photoreceptor 7 is electrostatically transferred onto the transfer paper 1 under the action of the transfer charger 8 . After the toner image is transferred, the transfer paper 1 is separated from the transfer belt 2 by curvature separation at the point where it is wound around the roller 6, and is conveyed to a fixing section (not shown) where it is fixed and image formation is completed. The surface potential of the transfer belt 2 after the completion of the above transfer process is determined by using a PET (polyethylene terephthalate (trade name: Mylar) film (thickness: 75 μm) with a volume resistance IQ of 16 to 1Q of 17Ω·1 as the transfer belt, and at a belt linear velocity of In the case of 120 dragons/dai, it will be charged to about -1200V. This charge 4
In order to eliminate static electricity from the transfer belt 4, the roller 4 is grounded, and the static elimination roller 3 is provided as a counter electrode in contact with the outer peripheral surface of the belt, and an alternating voltage is applied from an alternating voltage source 5. The charge is removed, and the next transfer step is started again.

In order to determine the voltage value and frequency of the alternating voltage applied to neutralize the transfer belt, the following experiment was conducted.

First, as shown in FIG. 2, a conductive roller (metal roller) 3' is provided in place of the static elimination roller 3 in contact with the outer peripheral surface of the belt 2 wound around the roller 4, and a DC power source 9 is connected to the conductive roller 3'.
A DC voltage is applied by P, the surface potential of the transfer belt 2 is measured by an electrometer 10, and recorded by a linear coder 11.
The charging characteristics of the ET film were investigated. The relationship between the applied voltage and the electrification level measured by changing the thickness of the PET film to 25 μm, 50 μm, and 75 μm was as shown in the graph of FIG. 3. From this graph, it was found that there is a charging start voltage (voltage below which no charging occurs), and that this charging starting voltage varies depending on the thickness of the film.

Next, the above-mentioned charging start voltage V. Figure 4(a), (
When an alternating voltage (frequency: 120 Hz>) as shown in b) was applied to the neutralizing roller, it was confirmed that the surface potential of the transfer belt 2, which had been charged to -1200 V, was neutralized to zero V.

This is the charging start voltage V. This means that although this applied voltage does not have the ability to charge a dielectric object to be charged, a force acts to move the space charge on the object to be charged, and the charge can be removed. In addition, since alternating applied voltages are used, the dielectric material is (÷), (-
) has a static neutralizing effect no matter which side is charged.

However, if the applied voltage is lower than the charging start voltage, insufficient charge removal will occur, and if the applied voltage is higher than the charging start voltage, the applied frequency (120H
z, v/f = 1 mm period), and the charge could not be removed to zero V.

In addition, when measuring the charging state with a surface electrometer as shown in Figure 2, the surface potential is measured as the average of a specific area, so as shown in Figure 5 (a), fine pitch When the battery is charged alternately (±) and (-), the electrometer outputs as if it were not charged, as shown in FIG. 5(b).

Therefore, the following method is proposed as a method for investigating the state of charging when a high frequency is used with an applied voltage equal to or higher than the charging start voltage. As shown in Figure 6, (shi), (-
) When a dielectric sheet 1' made of paper or plastic is placed on the alternately charged object 2, the dielectric sheet 1' has M
The stress of axwe 11 acts, and the dielectric sheet 1' is attracted in the direction of the charged object 2 by the force Fx, and the dielectric sheet 1'
If an attempt is made to move ' in a direction that deviates from the object to be charged 2, a frictional force is generated. Therefore, as shown in FIG. 7, a dielectric sheet 1' is brought into contact with the charged object 2 whose charging state is to be measured so as to overlap it by a certain length, and the dielectric sheet 1' is brought into contact with the charged object 2 whose charging state is to be measured in a direction opposite to the moving direction of the charged object 2. If the dielectric sheet 1' is pulled through the spring meter M, the frictional force F can be measured with the spring meter.

Figure 8 shows the tension when the pitch of the charge pattern formed on the transfer belt as a charged object is changed by changing the applied frequency under a constant voltage higher than the charging start voltage and a constant linear velocity. The curve of change in force is
A case is shown in which a PET film of 75 μm is used as a transfer belt.

From this figure, the pitch of the charge pattern, i.e., v/
f is v / f20, 1 [Dragon] (V is relative linear velocity 120
I! Im/s), the attraction force became zero, and it was found that the dielectric belt was not charged.

Therefore, the transfer belt was uniformly charged to -1200V,
After neutralizing the belt using an applied voltage of 4 KV p-p at a frequency f = 1200 Hz, the paper was placed on the belt and measured in the same manner, and the adsorption force was zero, and the electrometer measurement The result was also zero volts, confirming that the static electricity was uniformly removed to zero volts.

Process-1 ~ As described above, according to the static elimination method of claim 1, an alternating voltage of a frequency given by v/f 20.1 is applied to the charged object at a voltage lower than the charging start voltage which alternates the peak value of the applied voltage. Since static electricity is removed by applying voltage, the setting range for static electricity removal can be widened, and compared to static electricity removal using a corona discharger, the voltage is relatively low and no ozone is generated, making it an ozone decomposition and absorption device. This eliminates the need for this, which is effective in reducing size and cost.

Moreover, in the method for measuring the charging state according to claim 2.3, the unevenness and average value of the charging level can be measured with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a transfer belt and its surroundings as an example of a charged object to which the static elimination method of the present invention is applied;
3 and 3 are explanatory diagrams for explaining the charging start voltage of the dielectric film, FIGS. a),
(b) is a curve diagram showing a comparison between the actual potential of an alternating charging potential with a minute pitch and the output of an electrometer; FIGS. 6 and 7 are explanatory diagrams explaining the charging state measuring method of the present invention; FIG. 8 is a curve diagram showing the relationship between charge slam pitch and tensile force. DESCRIPTION OF SYMBOLS 1... Paper, 1'... Dielectric sheet, 2... Dielectric belt (charged object), 3... Static elimination roller (conductive electrode), 4... Roller (counter electrode), 5... Alternate power supply, 7... Photoreceptor, 8... Transfer charger, 10... Surface electrometer Patent attorney Ni Ito 4! 1 Figure 2+

Claims (3)

[Claims] (1) A conductive electrode is brought into contact with the surface of the object to be charged, a voltage is applied between the object to be charged and the conductive electrode, and the two are moved relatively at a relative speed of vmm/sec. In the static neutralization method for static neutralizing the body surface, the applied voltage is an alternating voltage whose peak value is equal to or higher than the charging start voltage for the charged object and whose frequency f (Hz) is given by v/f≦0.1 (mm). A static electricity removal method characterized by using a voltage that (2) A method for measuring the charged state of the surface of a charged object, the method comprising: bringing a dielectric into contact with the surface of the charged object and measuring the attractive force acting on the dielectric. (3) A method for measuring a charged state, which further comprises measuring an average surface potential in addition to measuring the charged state on the surface of a charged object according to claim 2.