JPS6183559A - Electrostatic discharging device - Google Patents

Abstract

PURPOSE:To vary and set an electrostatic discharging area by composing a dielectric electrode of plural electrode elements which are arranged in plural stagger arrays. CONSTITUTION:The electrostatic discharging device has an electrostatic discharging member 21 which is arranged for a member to be charged electrostatically, and this discharging member 21 includes a dielectric 24, dielectric electrode 22, and discharging electrode 23. The dielectric electrode 22 consists of plural electrode elements 22a which are arranged in two arrays independently of one another. Then, an alternating voltage from an alternating voltage applying means is applied between the respective electrode elements 22a of the dielectric electrode 22 and the discharging electrode 23 through voltage application control means 30 and 32.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge device used in electrostatic recording devices, electrophotographic devices, etc.

Background of the Invention For example, in an electrophotographic apparatus, a photoreceptor is charged and exposed to image light to form an electrostatic latent image. FIG. 1 shows an example of such an electrophotographic apparatus, which uses a so-called NP image forming process.

In FIG. 1, the TL photographic photoreceptor 1 has a photoconductor layer (1tE cadmium, etc.) 3 formed on the circumferential surface of a drum-shaped conductor (aluminum, etc.) 2 that is electrically grounded, and a transparent This is a well-known type having an insulating layer 4 (polyethylene terephthalate, etc.). The photoreceptor 1 rotates in the direction of the arrow, and is uniformly charged by the corona discharge device 5 as it rotates.

The discharge device 5 consists of a well-known type of corona discharge device, and its discharge polarity is positive when the photoconductor layer 3 is of N type;
In the case of P type, it is negative. The photoreceptor 1 is then subjected to secondary charging (removal of the charge imparted to the surface of the photoreceptor by the secondary charging) using a corona discharge device 6 using a glue having a polarity opposite to that of the discharge device 5. At the same time, image light (in this case, an optical image of the original to be copied) is exposed through a slint-like opening 07 provided in the discharge device 6. Next, in a step of 0 or more in which substantially uniform light (non-image light) containing no image information is exposed by the non-image light irradiating means 8, the photoreceptor l is exposed to a high-contrast electrostatic charge corresponding to the original to be copied. A latent image is formed, but the explanation of the physical phenomenon of static TLH1 image formation through such a process is given in the Japanese Patent Publication No. 42
Since it is well known from Publication No.-23910, etc., detailed explanation will be omitted to avoid complexity.

The latent image is developed (visualized) using toner in a developing device 9, and the obtained toner image is transferred by a transfer corona discharge device 10 onto a transfer paper 11 conveyed in the direction of the arrow. , is fixed on the transfer paper 11 by the fixing device 12. On the other hand, the photoreceptor 1 after the transfer is cleaned by a cleaner 13,
Reused.

A document O to be copied is placed on a document table 14 . The document table 14 moves forward in the direction of the arrow, and at this time, the document 0 is scanned and image light is projected onto the photoreceptor 1 . That is, when the document table 14 moves forward, the original fIO is illuminated by the lamp 15, and the light reflected from the document 0 is transmitted to the mirror 16, lens 17, . Mirror 18. Further, the light enters the photoreceptor 1 through the slit opening lower part. This results in
An optical image of the original O is slit exposed onto the photoreceptor 1.

When scanning of the original is completed, the original table 14 moves back in the direction opposite to the arrow and returns to the forward movement starting position. The lamp 15 is turned off when the manuscript table 14 moves backward.

L/7 S17 ft 1st T9 The example is a zoom lens, and the lens position on the optical path is, for example, the dotted line position 1.
7' to change the ratio of the optical path length between the document and the lens to the optical path length between the lens and the photoconductor, and by changing the focal length of the lens 17 in accordance with this ratio, the photoconductor 1 You can change the imaging magnification of the original image. Note that the mechanism for changing the position of the lens 17, the focal length changing mechanism, and the changing mechanism for changing the ratio of the photoreceptor circumferential speed to the original scanning speed are well known, and their explanations will be omitted here to avoid complexity.

Now, in the electrophotographic apparatus as described above, the discharge device 5,
6 operates while the photoreceptor 1 is rotating, while the photoreceptor l
starts rotating before the start of document scanning, that is, before the start of image exposure, and continues to rotate even after the document scanning is completed. This is to adjust the sensitivity of the photoreceptor before image exposure, and to perform processes such as transfer and cleaning after image exposure. However, when the photoreceptor is rotating in such a state that the image light is not exposed to the photoreceptor, the potential of the surface area of the photoreceptor becomes the dark area potential, and thus toner adheres to this area. In order to prevent this undesirable toner adhesion, in the conventional apparatus, auxiliary light is illuminated on the photoreceptor through the slit opening lower of the corona discharge device 6 when the image light is not exposed, and the surface potential of the photoreceptor is set as the bright area potential. Also, even during image exposure, the selected width dimension (dimension in the direction perpendicular to the transfer paper conveyance direction)
In order to prevent toner from adhering to the surface area of the photoreceptor that is not in contact with the transfer paper, auxiliary light is similarly illuminated on this area through the slit opening lower part of the corona discharge device 6, and the surface potential of this area is adjusted to the bright area. It was set as electric potential.

Furthermore, as is well known, Joyong TffQ in Figure 1
Double MUm Teshige [1 no! FF-1”EZMQ2wI+
If the document is double-printed (fy*M-), the width of the image will change even if it is the same document.

In other words, the width of the image exposure area of the photoreceptor l (dimension in the direction perpendicular to the direction of photoreceptor movement) for the same document changes depending on the selected magnification. In this case as well, auxiliary light was applied to an external area of the photoreceptor other than the image exposure area through the slit opening lower, and this area was set at a bright area potential.

However, in this conventional technique, an additional auxiliary light source is required for irradiating an auxiliary light to bring the external area other than the image exposure area (image area) of the photoconductor to a bright area potential where toner does not adhere. , power consumption also increases accordingly.

The main purpose of the present invention is to solve the above-mentioned disadvantages of the conventional technology. A first object of the present invention is to provide a discharge device capable of preventing undesirable toner adhesion.

In order to achieve this object, the present invention provides a dielectric, an induction electrode and a discharge electrode extending between the dielectric in the longitudinal direction of the dielectric, and a discharge electrode between the induction electrode and the discharge electrode. and an alternating voltage application means for generating ions in the vicinity of the discharge electrode by applying an alternating voltage to the discharge electrode. A voltage application control means is provided for selectively controlling the application of alternating voltages to each of the plurality of electrode elements by the alternating voltage application means, so that the discharge area can be variably set.

Mitate 1 Before explaining the configuration of the discharge device of the present invention, the principle of discharge employed in the discharge device of the present invention will be explained with reference to FIG.

The outline of this discharge principle is that an alternating current voltage is applied between electrodes that sandwich a dielectric material, positive and negative ions are generated at the junction between the end face of one electrode and the dielectric material, and a desired polarity is created by an external electric field. It extracts ions. More specifically, as shown in FIG. 2, the discharge device includes a charged member 25.
has a discharge member 21 disposed against the discharge member 2;
1 includes a dielectric 24, an induction electrode 22, and a discharge electrode 23. Alternate voltages are applied between the induction electrode 22 and the discharge electrode 23 by the alternate voltage application means 27, while the discharge member 2
The member to be charged 25, which moves in the direction of arrow A relative to 1, has a layer 25b made of an insulator or a photoconductor provided on a conductor base 25a, and a layer 25b made of an insulator or a photoconductor is provided on a conductor base 25a. A bias voltage is applied between them by a DC or AC bias voltage applying means 28. Induction electrode 2
By applying an alternating voltage between the discharge electrode 23 and the discharge electrode 23, a discharge is caused from around the discharge electrode 23, and sufficient positive and negative ions are generated.
The member to be charged 25 is charged by selectively extracting the positive or negative ions using an electric field caused by a bias voltage applied between the electrodes 5a.

In such a device, the thickness of the dielectric 24 is reduced (for example, the thickness is 500 gm or less, preferably 20 gm or less).
(approximately 200 gm), stable discharge can be obtained with a lower applied voltage than in conventional corona discharge devices.

Furthermore, the discharge device can be made smaller than conventional corona discharge devices.

This is because by reducing the thickness of the dielectric 24, the electric field strength between the two electrodes can be increased even if the alternating voltage applied between the two electrodes sandwiching the dielectric 24 is low. For this reason, if the electric field strength at the edge of one electrode (discharge electrode) is high enough to cause a discharge, discharge is possible, and a creeping discharge occurs along the surface of the dielectric 24 in contact with this electrode.

Figure 3 shows the relationship between the bias applied voltage to the discharge electrode 23 and the density of the ion current flowing to the grounded conductor base 25a under the conditions of an AC voltage frequency of 10 kHz and a peak-to-peak value VPP of 4.3 kV. As can be seen from Fig. 3, the ion current density increases exponentially as the applied voltage increases.Therefore, by controlling the applied voltage to the discharge electrode, the ion current density can be increased by controlling the applied voltage to the charged member. The amount of discharge can be controlled.

FIG. 4 is a perspective view showing an embodiment of the discharge device according to the present invention, in which members corresponding to those shown in the second figure are designated by the same reference numerals. The discharge member 21 has a discharge member 21 arranged with respect to the charging member, and the discharge member includes a dielectric body 24 made of ceramic glass or the like, and an induction electrode 22 and a discharge electrode 23 extending across the dielectric body in the longitudinal direction of the dielectric body. including.

As shown in FIG. 4, the induction electrode 22 is not a single body, but consists of a plurality of electrode elements 22a arranged in two rows and independent from each other, and the electrode elements in each row are different from the electrode elements in other rows. Mutual discrepancy relationship (staggered arrangement relationship in Figure 4)
are arranged in On the other hand, the discharge electrode 23 is composed of a single body extending in the longitudinal direction of the dielectric 24.

The discharge device further includes an alternating voltage applying means 27 such as an AC power source that applies an alternating voltage between each electrode element 22a of the induction electrode 22 and the discharge electrode 23, and a voltage that controls the application of the alternating voltage to each electrode element. and an application control means. In the illustrated embodiment, the voltage application control means includes a multiplexer 30 for connecting the alternating voltage application means 27 to each of the electrode elements 22a of the inductive electrode 22 independently of each other; The multiplexer 3 to apply
0.

On the other hand, a bias voltage is applied between the discharge electrode 23 and a charged member (not shown) by a bias voltage applying means 28 such as a DC power supply. In addition, the multiplexer 30 and the discharge member 2
The connection between 1 and 1 is made to maintain complete insulation to prevent unnecessary discharge.

To explain the operation, for example, when the discharge device of the present invention is
When used as a discharge device for primary charging in an electrophotographic apparatus as shown in the figure, the control circuit 32 controls the width of the transfer paper (dimension in the direction perpendicular to the transfer paper conveyance direction), the width of the original to be copied (dimension in the direction perpendicular to the original scanning direction). or, in the case of a variable magnification type device, an r width signal corresponding to the width of the image area according to the magnification (dimension in the direction perpendicular to the moving direction of the charged member, that is, the photosensitive drum), etc., to the multiplexer 30. to be applied. The multiplexer 30 responds to the signal by alternating voltage applying means 2.
7 is selectively applied to several electrode elements corresponding to the above-mentioned "width" among the electrode elements 22a of the induction electrode 22.

In the discharge principle explained with reference to FIG.
Ion generation in the vicinity of 3 is caused by the induction electrode 22 and the discharge electrode 2.
This is caused by applying voltage alternately between the two. Therefore, by controlling the application of this alternating voltage between ON and OFF, it is possible to control the generation of ions in the vicinity of the discharge electrode, and therefore, it is possible to control the discharge, that is, the attachment of ions to the charged member.

In the present invention, the induction electrode is made into a divided type consisting of a plurality of electrode elements as described above, and the ion generation area in the discharge electrode can be variably set by selectively controlling the application of alternating voltage to each electrode element. be. That is, returning to FIG. 4, with respect to the electrode elements 22a of the induction electrode 22 to which alternating voltages are applied by the multiplexer 30, positive and negative ions are generated around the nearby discharge electrode portion, but when the alternating voltage is applied No ion generation is observed for electrode elements that are not used. Therefore, when a bias voltage is applied while moving a charged member (not shown) in a direction perpendicular to the arrangement direction of the induction electrodes 22, the portion of the discharge electrode 23 near the several electrode elements 22a corresponding to the above-mentioned "width" Of the positive and negative ions generated in the surrounding area, predetermined ions are extracted and adhere to the charged member, but ions do not adhere to the corresponding regions of the charged member for electrode elements to which no alternating voltage is applied. As a result, only the area of the charged member corresponding to the image area is charged, and the area corresponding to the image area is not charged, so that it is possible to prevent toner from adhering to the non-image area.

For example, if the transfer paper is A4 size, the paper width is approximately 210mm.
Therefore, a "width" signal is output from the control circuit 32 so that only the region of the charged member corresponding to this paper width is charged, and in response, the multiplexer 30 selects the corresponding one of the electrode elements 22a. Apply alternating voltages to something. Therefore, only the region of the charged member corresponding to this paper width is primarily charged.

As described above, according to the present invention, by selectively controlling the application of alternating voltages to each of the plurality of electrode elements of the induction electrode, it is possible to reliably set the discharge region variably.
Undesirable adhesion of toner to the imaged area can be prevented. Further, for example, when the induction electrode is composed of a plurality of electrode elements arranged in a single row, the presence of gaps between these electrode elements causes discharge unevenness in the longitudinal direction of the discharge electrode. On the other hand, according to the present invention,
Since the electrode elements of the induction electrode are arranged in a staggered relationship in multiple rows, potential unevenness in one row is equalized by discharge from the discharge electrode portions corresponding to the electrode elements in other rows, so that the discharge device Overall, a uniform potential is achieved in the longitudinal direction of the discharge electrode.

FIG. 5 is a diagram showing another embodiment of the discharge device of the present invention. The embodiment shown in FIG. 5 has the same structure as the embodiment shown in FIG. be.

In FIG. 5, the induction electrode 22 has three electrode elements 22a.
These electrode elements are arranged in three rows in a staggered relationship with each other in the row direction (in FIG. 5, they are offset from each other in the row direction). Therefore, the control circuit 3
It will be understood that by selectively controlling the application of alternating voltages to each electrode element 22a by the voltage application control means constituted by 2 and the multiplexer 30, discharge regions with three different widths can be set.

Although the above description has been made regarding the case where the present invention is applied to a discharge device in a so-called NP type electrophotographic apparatus,
The present invention is not limited to this, and the electrophotographic apparatus may also be of a type other than the NP type, such as FJ? It is clear that a method such as a Carlson process method may also be used.

As stated above, according to the present invention, the discharge area can be reliably controlled with a simple configuration, so the device of the present invention can be used as a discharge device for primary charging in an electrophotographic device. In this case, the area of the charged member corresponding to the non-image area can be maintained at the bright potential without irradiating the charged member with conventional auxiliary light, and undesirable toner adhesion to this area can be prevented. It becomes possible. Therefore, not only is the auxiliary light source unnecessary, but also it is possible to reduce power consumption.

In addition, by selectively controlling the application of alternating voltages to multiple induction electrode elements, the discharge area can be variably set as desired, so it is possible to adjust the width of the transfer paper or the width of the image exposure area based on the imaging magnification. can be easily adapted.

Furthermore, according to the present invention, the discharge potential in the column direction does not become non-uniform, which is the case when a plurality of induction electrodes are composed of i number of electrode elements arranged in a single column.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of an electrophotographic apparatus to which the discharge device of the present invention can be applied, and FIG. 2 is a diagram showing the discharge principle employed in the discharge device of the present invention. FIG. 3 is a diagram showing the relationship between bias voltage application and ion current density, FIG. 4 is a perspective view showing one embodiment of the discharge device of the present invention, and FIG. 5 is another embodiment of the discharge device of the present invention. FIG. Explanation of the symbols 21 is a discharge member, 22 is an induction electrode, 22a is an electrode element of the induction electrode, and 23 is a discharge electrode. 24 is a dielectric, 27 is an alternating voltage application means, 28 is a bias voltage application means, and 30 and 32 are voltage application control means. Figure 1 Figure 2 Figure 3 Seal Voc(v') Figure 5 Cause

Claims (1)

[Claims] A dielectric, an induction electrode and a discharge electrode extending across the dielectric in the longitudinal direction of the dielectric, and applying alternating voltages between the induction electrode and the discharge electrode to generate ions near the discharge electrode. In the discharge device, the induction electrode includes a plurality of electrode elements arranged in a staggered relationship with each other in a plurality of rows, and further, each of the plurality of electrode elements is controlled by the alternating voltage application means. 1. A discharge device comprising voltage application control means for selectively controlling the application of alternate voltages to control a discharge region.