JPH03293683A - Electrifying device - Google Patents

Abstract

PURPOSE:To carry out stable electrification on a surface of a body to be electrified by making the electrifying member from a conductive wire member and providing a pressing member to maintain an electrifying wire member in a pressed state against the body to be electrified. CONSTITUTION:The electrifying wire 10 is pressed down against and brought into contact with a photosensitive drum 1 surface in an approximate parallel with a drum generatrix by the wide pressing member 11 matching a whole length of the wire whose whole length consists of an elastic body such as 'Moltoprene(R)'. A wide rigid holder plate 12 such as 'Derlin(R)' is provided in the back side of the opposite side of the wire pressurizing surface side in the pressing member 11, and the holder plate 12 is pressured against the photosensitive drum 1 against the elastic resistance of the pressing member 11 and the pressing member 11 is pressurized between it and the photosensitive drum 1 surface making a pressurized state with a pressurizing member, pressing down the whole length of the electrifying wire 10 to the photosensitive drum 1 surface immobile and stable with eveness on each part, and they are brought into a close contact. Thus, the stable electrification can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is a method of charging the surface of a charged object to a predetermined potential by bringing a charging member to which a voltage is applied into contact with a charged object (including static electricity removal processing). The same applies to contact charging devices.

(Prior art) For example, in image forming devices such as electrophotographic devices (copying machines, laser beam printers, etc.) and electrostatic recording devices, the surface of an image carrier as a charged object such as a photoreceptor or dielectric is charged. Corona discharge equipment has been widely used as a treatment device.

A corona discharge device is effective as a means for uniformly charging the surface of an object to be charged, such as an image carrier, to a predetermined potential. but,
It requires a high-voltage power supply and has problems such as relatively large amounts of undesirable ozone being generated due to corona discharge.

In contrast to such a corona discharge device, a contact charging device, which charges the surface of the charged object by bringing a charging member to which a voltage is applied as described above into contact with the charged object, can reduce the voltage of the power source, and
Since it has the advantage of generating only a very small amount of ozone, it is used, for example, in image forming apparatuses to charge the surface of image carriers such as photoreceptors and dielectrics, and other objects to be charged.
It has attracted attention as an alternative device to corona discharge devices, and research on its practical use is progressing (Japanese Patent Application Laid-Open No. 17826-1983).
7・56-104351・58-40566・58-1
39156/58-150975, etc.).

The present applicant also applied a DC voltage to a charging member and an oscillating voltage having a peak-to-peak voltage that is more than twice the charging start voltage of the charged object (voltage value changes periodically over time) for the purpose of uniform charging processing, etc. A number of proposals have been made, including contact charging methods and devices based on the application of a voltage that changes over time (Japanese Patent Laid-Open No. 63-149668/14961i9).
Publications, etc.).

The charging member generally has a roller type or a plate type structure.

FIG. 9 shows a schematic configuration of an example of an image forming apparatus using a roller type contact charging member as a charging processing means for an image carrier. The image forming apparatus in this example is a transfer type electrophotographic apparatus (copying machine, laser beam printer, etc.).

1 is a rotating drum-type electrophotographic photoreceptor (
(hereinafter referred to as a photosensitive drum), which is rotated clockwise as indicated by an arrow at a predetermined circumferential speed (process speed).

2 is a charging roller made of iron/stainless steel (SU
It consists of a conductive core metal 2a such as S), and a conductive rubber layer 2b such as carbon-containing EPDM, whose outer periphery is coated in the form of a roller. The entire length of the roller is brought into contact with the surface of the photosensitive drum 1 with a predetermined pressing force by applying pressure using a pressure means such as a spring shown in the figure, and in this example, the roller rotates as the photosensitive drum 1 rotates.

9 is an external power source that applies voltage to the charging roller 2;
Preset for the charging roller 2 by the power source 9,
A superimposed voltage of a DC voltage and an oscillating voltage with a peak-to-peak voltage that is more than twice the charging start voltage of the photoreceptor is applied to the contact spring 8 and the core metal 28.
By applying the electric potential to a predetermined potential, the outer circumferential surface of the photosensitive drum 1, which is being rotationally driven, is charged to a predetermined potential.

Next, the charged surface of the photosensitive drum 1 is subjected to image exposure 3, such as image-forming exposure of the original image or scanning exposure with a laser beam modulated in accordance with printed information, by an exposure means (not shown) to form a target image. Electrostatic latent images corresponding to information are sequentially formed on the surface of the photosensitive drum.

Next, toner is supplied to the surface of the photosensitive drum from the developing sleeve 4 of the developing device, and the latent image formed on the surface of the photosensitive drum is sequentially developed as a toner image.

A transfer roller 5 is brought into pressure contact with the photosensitive drum 1 on the downstream side of the developing sleeve 4 in the rotational direction of the photosensitive drum, and a transfer material 7 is transferred from a paper feed section (not shown) to the pressure contact portion (transfer) between the photosensitive drum 1 and the transfer roller 5. With respect to part), when the leading edge of the toner image on the surface of the photosensitive drum 1 reaches the pressure contact part, the leading edge of the transfer material 7 also arrives at the pressure contact part, and is supplied in a cycle synchronized with the rotation of the photosensitive drum. .

A transfer bias is applied to the transfer roller 5 from a power source, and as the transfer material 7 passes through the pressure contact section, the toner image on the surface of the photosensitive drum is sequentially transferred to the transfer material 7 side (transfer).
do.

After the toner image has been transferred, one surface of the photosensitive drum is cleaned by a cleaning device 6.
Residues such as untransferred toner are removed and cleaned.
The edges are turned over and used for image formation.

(Problems to be Solved by the Invention) However, the above conventional example has the following problems.

1) Due to durability, rubber plasticizer oozes out from the conductive rubber layer 2b of the charging roller as a charging member and adheres to or fuses to the surface of the photosensitive drum 1, which is the object to be charged, resulting in image deletion. It was causing this.

2) In the charging roller 2 for A3 size, the length in the axial direction increases accordingly, and when the charging roller 2 is pressed against the photosensitive drum 1 by pressing both ends of the charging roller 2 with a pressure means such as a spring, the central part of the roller floats off the surface of the photosensitive drum 1, and a charging failure occurs in that area.

3) For models with high process speeds, the frequency of the primary power supply applied to the charging roller 2 must be increased to match the process speed to prevent charging failures.
If it exceeds 0 Hz, the photosensitive drum 1 and the charging roller 2 vibrate and the charging noise generated becomes louder.

The present invention makes it possible to satisfactorily charge the surface of an object to be charged, such as a photosensitive drum, by a contact charging method without the above-mentioned problems.

(Means for Solving the Problems) The present invention provides a charging device in which a charging member to which a voltage is applied is brought into contact with a charged object to charge the surface of the charged object, wherein the charging member is a conductive wire. The gist of the present invention is a charging device characterized by having a pressing member that keeps the charging wire material pressed against an object to be charged.

(Function) (1) A conductive charged wire is used as the charging member, this charged wire is pressed against the surface of the charged object by the pressing member, and a voltage is applied to the charged wire to cause the charging roller to Contact charging of the surface of the object to be charged is performed in the same way as in the case of a charging plate or a charging plate.

(2) Unlike charging rollers and charging blades, charging using this charging wire does not have a charging layer made of rubber, etc., so the plasticizer that oozes from the rubber charging layer does not reach the surface of the charged object. It has become possible to suppress the occurrence of problems such as adhesion/fusion and resulting image blurring in the image forming apparatus.

(3) In addition, the problem of floating in the center of the roller, which has been a problem with charging rollers, can be solved by charging using this charging wire, since the charging wire as a charging member is pressed against the surface of the object to be charged, so that the entire length of the charging wire is actively pressed against the surface of the object to be charged. By keeping the charging wire in a pressed state, the charging wire does not float off the surface of the charged object, and charging defects due to floating do not occur.

(4) Since the entire length of the charged wire is kept actively pressed against the surface of the charged object by the pressing member, even if a large oscillating voltage with a peak-to-peak voltage superimposed with direct current is applied to the charging member, it will not be charged. The wire does not vibrate. Furthermore, even when only direct current was applied, the charged wire no longer danced and moved at the moment of application.

As a result, the charging wire does not separate from the surface of the object to be charged, and in combination with the effect of item (3) above, stable charging can be performed.

(5) Regarding charging noise, it no longer occurred at all even when the primary power frequency applied to the charging wire exceeded 300 Hz. The reason for this is that when an external bias is applied to the charging roller, the roller begins to vibrate, and the flow of air caught between the roller and the object to be charged causes charging noise. It is thought that since there is almost no air caught between the wire and the object to be charged, no charging noise is generated.

(6) Also, in charging using a charging wire, unlike the case of a charging plate that is pressed against the object to be charged with a constant pressure, silica, toner, etc. that have passed through the cleaning device 6 in the image forming apparatus are mixed with the charging wire. It also has the advantage that it easily passes between the photosensitive drum as the object to be charged and, as a result, is less likely to adhere to the charging wire.

(Example) Example 1 (Figures 1 to 3) Figure 1 is a side view of an example of the charging device of the present invention, Figure 2 is a partially cutaway plan view, and Figure 3 is a partially cutaway perspective view. It is a diagram.

Reference numeral 1 denotes a photosensitive drum as a charged member in the image forming apparatus shown in FIG. In this example, it consists of an organic photoreceptor (OPC), has an outer diameter of 30φ in this example, and is driven to rotate at a predetermined speed in the clockwise direction of the arrow.

10 is a charging wire material made of conductive material such as iron, copper, aluminum, SUS, etc. as a contact charging member (hereinafter referred to as charging wire)
In this embodiment, the charging wire 10 is a gold-plated tungsten wire with a diameter of 60 μm.

The charging wire 10 is placed approximately parallel to the drum busbar, and its entire length is pressed against the photosensitive drum 1 by a horizontally elongated pressing member 11 corresponding to the entire length of the wire and made of an elastic material such as maltbrane.
Press it against the surface and make contact. The pressing member 11 has a horizontally long rigid holder plate 12 made of Delrin or the like on the back side opposite to the wire pressing surface side, and the holder plate 12 is pressed against the photosensitive drum 1 by the elastic resistance of the pressing member 11. A pressing member 11 is placed between the surface of the photosensitive drum and the surface of the photosensitive drum.
By applying pressure to the charging wire 10 using a pressure member (not shown), the entire length of the charging wire 10 is uniformly pressed immovably and stably against the surface of the photosensitive drum 1 and brought into close contact.

The charging wire 10 has a contact 8 connected to the power source 9 at one end thereof.
A voltage is applied through the oscillating voltage, which is a superimposition of an AC voltage and a DC voltage.

Here, the oscillating voltage is a voltage whose voltage value changes periodically over time. More specifically, preferably, a voltage that is a superimposition of an AC voltage and a DC voltage having a threshold voltage that is twice or more of the charging start voltage of the photoreceptor is applied to the charging wire, that is, the wire 10. Further, the waveform of the oscillating voltage is not limited to a sine wave, but may be a rectangular wave, a triangular wave, or a pulse wave.

Furthermore, it is possible to similarly charge the object to be charged using only a direct current voltage.

In the above configuration, the photosensitive tram 1 is set at a circumferential speed of 40 mm/sec.
Rotate with e, and apply -700V to the charging wire 10 from the power supply 9.
DC voltage, peak-to-peak voltage 1800Vpp, frequency 2
When an AC voltage of 50 Hz was applied, the surface of the photoreceptor 18 was uniformly charged to about -700 V, and a good image was output.

Since the entire length of the charging wire 10 is pressed against the surface of the photosensitive drum by the pressing member 11, even if a high AC voltage with a peak-to-peak voltage superimposed on the charging wire 10 is applied to the charging wire 10, the charging wire 10 will not move. does not vibrate. Furthermore, even when only direct current is applied, the charging wire 10 no longer dances at the moment of application. As a result, the charging wire 10 does not come off the surface of the photosensitive drum 1, and stable charging can be performed.

Furthermore, unlike the case of a charging roller, this type of contact wire charging does not have a charging layer made of rubber or the like, so problems such as fusion and flow due to plasticizer seeping from the charging layer of the charging roller do not occur. lost.

Furthermore, with this type of contact wire charging, the lifting of the central part of the roller from the surface of the photosensitive drum, which had been a problem with charging rollers, no longer occurs due to the structure.

Furthermore, the charging layer, which had been a problem with charging rollers, no longer occurs at all.

Further, unlike the case of a charging plate, this embodiment has the advantage that silica, toner, etc. that have passed through the cleaning blade 6 are blocked by the molten plane, which is the pressing member 11, and are less likely to adhere to the charging wire 10.

Embodiment 2 (FIG. 4) In this embodiment, two charging wires 10 are provided in contrast to one charging wire 10 in the first embodiment. 2-wood charging wire IOA・
The IOBs are pressed against the surface of the photosensitive drum 1 in parallel with each other by a pressing member 11, and a voltage is applied to both. With this configuration, even if one charging wire is contaminated with foreign matter or is broken, the remaining charging wires can continue to reliably charge the surface of the photosensitive drum. The same effect can be obtained even if the number of charging wires is three or more.

Embodiment 3 (FIGS. 5 and 6) In this embodiment, the charging wire 10 is held approximately parallel to the direction of the drum generatrix, and its left and right ends are pressed by pressing members 11a and 11a made of Delrin or the like, respectively. A 100 μm thick polyethylene terephthalate sheet (Mylar sheet) whose longitudinal side is fixed to the cleaning blade holder 6a is used as a pressing member flb to hold the charged wire portion between the pressing members 11a and lla on both ends of the sheet. The sheet is stably pressed against one surface of the photosensitive drum by M (sheet deflection reaction force).

With such a configuration, not only stable charging is performed, but also the pressing member 11b presses against the photosensitive drum 1.
There is also the advantage that the photosensitive drum is not scraped by the pressing member because it does not come into direct contact with the pressing member. Pressing member f
The material of lb may be SUS, aluminum, PET, copper sheet, etc. in addition to Mylar sheet.

Embodiment 4 (FIG. 7) In this embodiment, the cleaning plate 6 is also used as a member for pressing the charging wire 10.

That is, the blade length (
A positioning #I6b for storing the charging wire 10 is provided along the photosensitive drum generatrix direction), the charging wire 10 is glued and stored in the groove 6b as necessary, and the cleaning blade 6 is attached to the photosensitive drum 1 with its tip edge. The charging wire 10 on the back side of the plate is pressed against the surface of the photosensitive drum 1 at a predetermined pressure and is fixedly supported by a mounting section (not shown).

This configuration has the advantage that there is no need to add a new separate part as a pressing member, and the configuration around the photosensitive drum becomes extremely simple.

Embodiment 5 (FIG. 8) The charging wire 10 (IOA/10B) does not necessarily have to have a circular cross section, but may have a triangular, quadrangular, oval, etc. cross section as shown in FIGS. 8(a) to (C). It's okay. In this case, since the contact area between the photosensitive drum 1 and the charging wire can be increased, more stable charging can be achieved than with a charging wire having a circular cross section.

Further, as shown in FIGS. 8(d) to 8(g), the charging wire 10 is used as a core metal part, and its outer peripheral surface is coated with a dielectric surface layer 101 made of resin or the like (layer thickness, e.g. 10 to 10
00 .mu.m), or as shown in FIGS. 8(h) to (k), a surface layer 101 as described above may be used at least at the portion in contact with the charged object.

Materials constituting the surface layer 101 include N-methoxymethylated nylon (trade name: Torezin: Teikoku Kagaku Sangyo Co., Ltd.), polyvinyl butyral resin, polyurethane resin,
Ethylene/vinyl acetate resin, styrene/butadiene resin, fluorocarbon resin with low resistance powder (carbon, etc.) dispersed (trade name: Emlaron Nippon Addison Co., Ltd.), resins such as regenerated cellulose, and even engineered chlorohydrin and urethane. , CR, NBR rubber, etc. can be used.

Furthermore, it is also possible to use a heat shrink tube.

(Effects of the Invention) As described above, the device of the present invention is a device that can perform contact charging on a charged object such as a photoconductor in the same manner as a conventional charging roller or charging blade, and in the case of a charging roller or charging blade. Unlike , it does not have a charging layer made of rubber or the like, so there are problems such as adhesion and fusion of plasticizer that oozes from the rubber charging layer to the surface of the charged object, resulting in image distortion in the image forming device, and charging rollers. There is no problem of the occurrence of partial charging failure due to floating in the center of the roller, which was a problem, and there is no problem of the formation of a charged layer. It is extremely effective when used as a device.

[Brief explanation of the drawing]

FIG. 1 is a side view of the device of the first embodiment. Figure 2 is a partially cutaway plan view. FIG. 3 is a partially cutaway perspective view. FIG. 4 is a partially cutaway perspective view of the device of the second embodiment. FIG. 5 is a side view of the device of the third embodiment. FIG. 6 is a partially cutaway plan view. FIG. 7 is a side view of the device of the third embodiment. FIG. 8(a) to FIG. 8(k) are various enlarged cross-sectional views of the charging wire. FIG. 9 is a schematic configuration diagram of an example of an image forming apparatus using a charging roller. 1 is a photosensitive drum as a charged object, 1o/10A/IO
B is a charging wire (conductive charging wire material) as a charging member;
9 is an external power source, and 1111a and llb are pressing members.

Claims (1)

[Claims] (1) In a charging device that charges the surface of the charged object by bringing a charging member to which a voltage is applied into contact with the charged object, the charging member is a conductive wire, and the charging wire is brought into contact with the charged object. A charging device characterized by having a pressing member that maintains a pressed state.