JPS6317475A - Electrostatic discharging device - Google Patents

Abstract

PURPOSE:To eliminate the influence of a last image pattern by forming dielectric electrodes and discharging electrodes so that they cross each other. CONSTITUTION:The dielectric electrodes 22 and discharging electrodes are plural crossing electrodes and electrostatic discharging is caused by discharging electrodes 23 nearby intersections. An alternating voltage is applied to between the dielectric electrodes 22 and discharging electrodes 23 from an alternating voltage applying means 27, a photosensitive drum 1 which moves relatively to the discharging member 21 as shown by an arrow A is an OPC photosensitive body on a conductive base 26. A bias voltage is applied to between the conductive base 26 and discharging electrodes 23 from a bias voltage applying means 28. Thus, the alternating voltage is applied to between the dielectric electrodes 22 and discharging electrodes 23 as an electrostatic charging means to cause electrostatic discharging from the periphery of the discharging electrodes 23 and generate sufficient positive and negative ions, and the positive or negative ions are extracted selectively by an electric field based on the bias voltage applied between the discharging electrodes 23 and conductive base 26 to charge the photoconductor surface of the photosensitive drum 1 electrostatically to specific polarity and a desired value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a band M and an apparatus for performing electrostatic charging in electrostatic recording, electrophotographic bag counting, etc.

11 and 3 Conventionally, color image copying devices using multicolor electrophotography are
~3 methods have been devised and commercialized, but: 51r
The method shown in f4 is also one of the typical methods.

In this method, each of the first to fourth image forming apparatuses Pa, Pb,
Dedicated photosensitive drums 1a, lb, lc, for each Pc and Pd,
ld, and a dedicated latent image forming section 2 for each.
a, 2b, 2c, 2d, developing section 3a, 3b, 3c, 3d
, transfer section 4a, 4b, 4c, 4d, cleaning section 5a
, 5b, 5c, and 5d are arranged. First, the latent image forming section 2a of the first image forming apparatus Pa forms a latent image of the yellow component color of the original image on the photosensitive drum la by a known method, and then the developing section 3a develops a latent image with yellow toner. A visible image is formed using the agent, and the yellow toner is transferred to the transfer member 6 in the transfer section 4a.

On the other hand, while this yellow image is being transferred, a latent image of a magenta component color is formed in the first image forming apparatus Pa, and then a toner image of magenta toner is obtained in the developing section 3b. When the transfer member 6 whose transfer has been completed at Pa is carried into the transfer member 4b of the second image forming device r11Pb, this magenta toner image is transferred to a predetermined position on the transfer member 6.

After image formation is completed in the same manner for cyan color and blurred two colors, the image is fixed in the fixing section 7.

A multicolor image is obtained on the transfer member 6. After the transfer, each photosensitive drum is cleaned by cleaning sections 5a, 5b, and 5c.
, 5d to remove residual toner.

Prepare for the next latent image formation to be performed subsequently.

By the way, in this type of device, each unit is placed in a separate image forming device for each color, and in order to obtain a stable color image, it is necessary to perform stable and even image formation in each unit. . Otherwise, uneven coloring and changes in hue will occur. Among these units, the charging device uses wire diameter 0. Corona charging devices are widely used that perform corona discharge by applying a high voltage to a tungsten wire of about 100 mL.

However, such a corona charging device has the disadvantage that the wire is thin and easily damaged, and furthermore, the wire becomes dirty and uneven discharge occurs, resulting in non-uniform charging of the charged object.

Furthermore, it is necessary to maintain a certain distance between the wire and the conductive shielding member surrounding the wire, which limits the miniaturization of the corona charging device.

On the other hand, in this type of multicolor copying apparatus, when the charging polarity of the charging process is negative, a problem arises in that a considerable amount of ozone is generated due to the large number of charging devices as described above.

Particularly when using OPC photoreceptors, which have become mainstream in recent years, negative charging is common, and countermeasures must be taken to deal with this problem.

Furthermore, a scorotron charging device, in which a grid electrode is added to a corona charging device, has become common because of the stability of the charging potential. Therefore, it is inevitable that the charging current will be larger than that of the corona charging device, and the amount of ozone generated will also inevitably increase.

From the above, it is desirable to introduce a charging device that can be downsized, can charge uniformly and stably, and generates less ozone. Some devices apply a voltage to generate positive and negative ions at the junction between the end face of one electrode and the dielectric, and extract ions of a desired polarity using an external electric field. (Hereinafter referred to as a plate charging device) FIG. 2 shows the basic configuration of this type of discharge member.
4. Induction electrode 22) It has a discharge electrode 23.

Alternate voltages are applied between the induction electrode 22 and the discharge electrode 23 by an alternate voltage application means 27, while the photoreceptor drum 1, which moves in the direction of arrow A relative to the discharge member 21, is placed on the conductor base 26. A bias voltage is applied between the conductor base 26 and the discharge electrode 23 by a bias voltage applying means 28. By applying an alternating voltage between the induction electrode 22 and the discharge electrode 23,
After causing a discharge from around the discharge electrode 23 and generating sufficient positive and negative ions, the discharge electrode 23 and the conductor base 26
The photosensitive drum 1 is charged by selectively extracting the pressure or negative ions using an electric field caused by a bias voltage applied therebetween.

Furthermore, the thickness of the dielectric 24 is changed (for example, the thickness is
The applied voltage is lower than that of the conventional corona charging device 211 (for example, about 1.5 to 2 in peak-to-peak value,
Stable discharge can be obtained at 5 KV). Furthermore, the charging device can be made smaller than the conventional corona charging device.

In addition, this charging device is suitable for uniform charging because it is difficult to cause contamination of the discharge electrode such as so-called wire contamination due to floating particles in the air coming close to the wire of a conventional corona charging device.

However, when the present inventors installed such a plate charging device in an actual copying machine and formed an image, they found that an image corresponding to the pattern of the previous copy image appeared on the next copy image (development (hereinafter referred to as "development")). It was found that the phenomenon (referred to as a ghost phenomenon) tends to be relatively noticeable.

This ghost phenomenon can be removed by pre-charging exposure. However, as mentioned above, there is a strong demand for miniaturization in multicolor copying apparatuses in which three or four image forming apparatuses are arranged, and consideration must be given to reducing the number of component parts as much as possible.

Therefore, a charging device that does not require pre-charging exposure or the like is desired. Further, optical fatigue of the photoreceptor due to pre-exposure causes the charging voltage to become unstable. That is, optical fatigue changes with the passage of time and the environment of the photoreceptor, thereby affecting charging. Therefore, a charging device that does not require the use of pre-charging exposure or the like or a charging device that can provide a stable charging voltage against optical fatigue is desired.

Another object of the present invention is to provide a discharge device that is simple and easy to use by simply improving existing components without installing a new mechanism such as pre-charging exposure, and furthermore, suppressing an increase in cost. It's about doing.

11 Summer 1'' According to the present invention, there is provided a discharge device for uniformly charging a member to be charged, which includes a dielectric, an induction electrode and a discharge electrode extending between the dielectric, and a discharge electrode between the induction electrode and the discharge electrode. an alternating voltage applying means that applies an alternating voltage to generate ions in the vicinity of the discharge electrode; and an alternating voltage applying means that acts between the discharge electrode and the charged object to extract the ions generated by the discharge and polarize the charged object with a specific polarity. In the discharge device equipped with an external electric field applying means for charging, there is provided a discharge device characterized in that the dielectric electrode and the discharge electrode are a plurality of electrodes that intersect with each other, thereby preventing the generation of ghost images. can.

Practical Examples Hereinafter, concrete examples of the present invention will be described in detail with reference to the accompanying drawings. Although this embodiment has been described using a multicolor copying apparatus, it goes without saying that the present invention is not limited to these multicolor copying apparatuses, and can also be applied to monochrome copying apparatuses.

FIG. 3 is a sectional view showing an embodiment of the present invention. The apparatus of this embodiment has four sets of electrophotographic laser beam printer mechanisms built in as a plurality of image forming apparatuses. The main machine box of the apparatus, Pa, Pb, Pc, and Pd indicate four sets of image forming apparatuses arranged sequentially from right to left inside the main machine box IO.The conveyor belt drive roller 11 is rotationally driven by a drive source (not shown). and the conveyor belt 8 is suspended.

This conveyor belt 8 is made of a mesh of Tetoron fibers, and is moved by a drive roller 11 in the direction of the arrow shown in the figure. 13 is a paper feeding mechanism installed on the right side of the machine frame, 7 is an image fixing device installed on the left end side, and 14 is an outlet for discharging the transfer member to the outside of the machine.

The mechanical configurations of the image forming apparatuses ea, Pb, Pc, and Pd are substantially the same. That is, these image forming apparatuses each have photoreceptor drums la, 8C, and 8C as image carriers that are rotationally driven in the direction of the arrow around shafts 8a, 8b, and 8C18d, respectively.
lb, lc, ld, and chargers 15a, 15b, 15c, 1 sequentially arranged around the drum in the drum rotation direction.
5d, developing devices 3a, 3b, 3c, 3d, transfer discharge device 4
a, 4b, 4c, 4d, cleaning device 5a, 5b, 5
c, 5d, and laser beam scanners 16a, 16b, 16c, 16d arranged above the photoreceptor drum. The laser beam scanner has a semiconductor laser, a polygon mirror, an fθ lens, etc., and upon receiving an electric digital pixel signal, sends a laser beam modulated in accordance with the signal to chargers 15a, 15b, 15c, and 15d. The drum surface is exposed by scanning in the drum generatrix direction between the developing devices 3a, 3b, and 3C13d.

Further, the developing device 3a of the first image forming apparatus Pa is filled with yellow toner, and the second developing device 3a is filled with magenta toner.
The third one stores cyan toner, and the fourth one stores black toner.The laser beam scanner 16a of the first image forming apparatus Pa has pixels corresponding to the yellow component image of the color image. The second image forming device pb has a signal corresponding to a magenta component image, the third device Pc has a signal corresponding to a cyan component image, and the fourth device Pd has a signal corresponding to a black component image. Signals corresponding to are input respectively.

A paper feeding mechanism 1 feeds a cut sheet of transfer paper 6 as a transfer member.
When the sheet is inserted onto the feed guide 51 of No. 3, its leading end is detected by the sensor 52, and this start signal causes each image forming apparatus Pa, Pb to

The photosensitive drums la, lb, lc, and ld of PC and Pd start rotating. The drive roller 11 is also driven at the same time, and the conveyor belt 8 also begins to run in the direction of the arrow. The transfer paper 6 is placed in the paper feed guide 5
7 and is supplied onto the conveyor belt 8. Thereupon, the transfer paper 6 receives a corona discharge from the device charger 59 and is reliably placed on the conveyor belt 8.

Furthermore, the leading edge of the transfer paper 6 is connected to each sensor 60a, 6°b, 60
When c and 80d are cut off, each image forming bag is activated by that signal! Image formation is sequentially started on each of the photosensitive drums la, lb, 1c, and ld, which are rotating in advance, 'tPa, Pb, Pc, and Pd. That is, the photosensitive drum 1a of the first image forming apparatus Pa has a yellow image, the second apparatus Pb has a magenta image, the third apparatus Pc has a cyan image, and the fourth apparatus Pd has a black image. are divided and formed.

The image forming principle in each image forming apparatus is already well known as the Carlson process, so its explanation will be omitted. Then, the transfer paper 6 is moved toward the fixing device 7 by the rotation of the conveyor belt 8 to the image forming bags fiPa, Pb, P
c and Pd and are conveyed, and each color is sequentially superimposed and transferred onto the surface of the transfer paper 6 by the transfer dischargers 4a, 4b, 4c, and 4d of each device to synthesize a color image. Ru. When the transfer paper 6 passes through the fourth image forming device Pd, the charge is removed by a static eliminator 61 to which an AC voltage is applied, and the transfer paper 6 is separated from the conveyor belt 8.Next, the transfer paper 6 enters the fixing device 7 where one image is formed. After fixing, the image is discharged outside the machine from the outlet 14, and one print cycle is completed.

In this embodiment, a charging device having a structure as shown in FIG. 4 is used. The dielectric electrode 22 and the discharge electrode 23 are composed of a plurality of intersecting electrodes as shown in the figure, and discharge occurs at the discharge electrodes near the intersection. The discharge electrode 23 has a width of about 10
The dielectric electrodes 22 are arranged in the axial direction at a distance of about 1 mm from the photosensitive drum 1 at a distance of about 1 mm from the photosensitive drum 1 at the center.
The discharge portions are arranged with a slight inclination with respect to the rotational direction of the photosensitive drum l so that the discharge portions do not overlap with respect to the rotational direction of the photosensitive drum l.

The band 'F! in the direction of rotation of the drum due to this charging device! The width is about 1
5 mm, and is determined so that the charging potential saturates to a constant value while the surface of the photoreceptor passes through the band [111]. In this example, the discharge applies a charge uniformly in two dimensions. This allows sufficient charging time, and by dividing the discharge into points within the plate charging plane, the amount of ozone generated can be minimized.

Alternate voltages are applied between the induction electrode 22 and the discharge electrode 23 by an alternate voltage application means 27.

On the other hand, the photosensitive drum l, which moves in the direction of arrow A relative to the discharge member 21, is an OPC photosensitive member on a conductive base 26. A bias voltage is applied between the conductor base 26 and the discharge electrode 23 by a bias voltage applying means 28. At this time, the application of bias voltage is not limited to the discharge electrode 23,
The induction electrode 22 may also be used.

As a charging method, by applying alternate voltages between the induction electrode 22 and the discharge electrode 23, a discharge is caused from around the discharge electrode 23, and sufficient positive and negative ions are generated.
The positive or negative ions are selectively extracted by an electric field caused by a bias voltage applied between the discharge electrode 23 and the conductive substrate 26, and the photoconductor surface of the photoconductor drum l is made to have a specific polarity.
and charged to a desired value.

In this example, the bias voltage is -560V, and the alternating voltage AC1
, 4KV frequency 24K)lz was applied.

Figure 5 shows the charging characteristics in this case in comparison with the charging characteristics when one plate charging device is used.The curve indicated by 48 is that of this example, and the curve indicated by 42 is when one plate charging device is used. This is the case.

As is clear from this figure, the surface potential of the photoreceptor drum approaches the saturated state widely while passing through the charging width 43.

It has been confirmed that by using such a plate charging device, the occurrence of the ghost phenomenon described in the explanation of the prior art can be prevented.

This is considered to be due to the following reasons.

As is clear from FIG. 5, in the charging device of the present invention, the charging width is 4
3, the photoreceptor surface potential is already saturated to a constant value. On the other hand, the surface potential of the photoreceptor after the cleaning process is different between the exposed area and the non-exposed area as shown in FIG. Since it is used after being saturated to a certain value, even if there is the above-mentioned potential difference, this potential difference is equalized while passing through the charging width, and as shown in FIG. I can't pick up the influence of.

On the other hand, in the case of a single charging device, the surface potential of the photoreceptor is not saturated within the charging width 43, so this potential difference remains as it is. In other words, from the charging characteristics 42 in FIG. 5, in a single plate charging device, the respective potentials are added up, resulting in a charging potential as shown at 47 in FIG. 6, and an image pattern called a ghost occurs after development. According to the present invention, this can be prevented.

This effect is particularly remarkable when an OPC photoreceptor or the like is used. In general, it is desirable that the residual charge due to optical fatigue of the photoreceptor, that is, the residual charge in which part of the carriers generated by exposure remains inside the photoreceptor, is erased by the next charging process and the photoreceptor is uniformly charged.

In particular, in the case of an OPC electrophotographic photoreceptor, the transient time is long, ranging from several tens to hundreds of m5ec, and if the charging time is short, charging ends before the residual carriers are sufficiently moved. The charging width of the above plate charging device is several mm.
The moving speed of the photoreceptor is approximately 100 mm/see.
Then, the distance working during the transient time of 12 is 10
The charging time is approximately 1 mm, which is a short charging time and causes a decrease in the charging potential of the exposed area.

If the charging device according to the present invention is used, the photoreceptor can be charged in a charging time that is sufficiently longer than the transient time of the carrier, so that the ghost phenomenon can be prevented and stable and uniform charging is possible.

FIG. 7 shows another embodiment of the invention.

This embodiment uses the dielectric electrode 22 and discharge electrode 2 of the embodiment shown in FIG.
In other words, a plurality of dielectric electrodes 22 are arranged in the axial direction of the photoreceptor drum 1, and the discharge electrodes 23 are arranged slightly inclined with respect to the rotation direction B of the photoreceptor drum 1. The discharge electrode 23 is made to have a line width of several millimeters, whereas the line width of the dielectric electrode 22 is several tens to hundreds of liters.

This embodiment also provides the same effects as the previous embodiment.

As described above, according to the present invention, an induction electrode and a discharge electrode are provided with a dielectric material sandwiched between them, voltages are applied alternately between them, and a constant voltage is applied between the discharge electrode and the photoreceptor drum. The discharge electrode and dielectric electrode of the plate charging device that charges the photoreceptor drum are composed of a plurality of electrodes that cross each other, and the discharge is two-dimensional and substantially uniform, with a component also in the moving direction of the photoreceptor drum. Since a discharge surface is formed, the charging potential can be saturated to a constant value for use, and sufficient charging time can be taken. There is no need to create and erase them, and the influence of these previous image patterns can be prevented.

The second reason is that the plate charging device has lower applied voltage and lower current than the scorotron charging device, and therefore the amount of ozone generated can be kept low.

This is particularly advantageous for multi-color copying machines that are arranged with 3 to -4 image forming devices as described in the embodiments of the present invention, and the copying machine as a whole can benefit from smaller power supplies, lower ozone generation, etc. You can expect good results.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view illustrating a typical configuration of a multicolor copying apparatus. FIG. 2 is a diagram explaining the basic configuration of a plate charging device. FIG. 3 is a longitudinal sectional view illustrating the detailed configuration of an example of a multicolor copying apparatus in which the present invention is effectively used. FIG. 4 is a diagram illustrating the detailed configuration of the plate charging device according to the present invention. FIG. 5 is a diagram showing the charging characteristics of the plate charging device according to the present invention. FIG. 6 is a diagram showing the surface potential of the photosensitive drum when a charging device is used. FIG. 7 is a diagram illustrating another embodiment of the present invention. l... Photosensitive drum 22... Inductive electrode 23... Discharge electrode 24... Dielectric 27... Alternating voltage power source 28... Bias voltage power source Fig. 1 Fig. 2 Fig. 5 Charging time (xroom isc+ Figure 6

Claims (2)

[Claims] (1) A discharge device that uniformly charges a member to be charged, comprising a dielectric, an induction electrode and a discharge electrode that extend between the dielectric, and an alternating voltage applied between the induction electrode and the discharge electrode. Alternating voltage application means for generating ions in the vicinity of the discharge electrode; and external electric field application that acts between the discharge electrode and the object to be charged, extracts the ions generated by the discharge, and charges the object to be charged to a specific polarity. A discharge device comprising: a discharge device characterized in that the dielectric electrode and the discharge electrode are a plurality of intersecting electrodes. (2) The discharge device according to claim 1, characterized in that the intersections of the plurality of dielectric electrodes and the plurality of discharge electrodes are arranged so as not to be aligned in the moving direction of the charged object. discharge device.