JPS5828581B2 - corona tie den sochi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona charging device, and more particularly to a corona charging device that prevents particulate material contained therein from adhering.

Corona charging devices are widely used in conventional devices as ion generators for electrostatic charging.

After a period of use in these conventional corona charging devices, particulate material builds up on the insulating surfaces of the corona device as well as on the non-corona electrodes, such as screens or conductive backing electrodes.

Deposition of particulate material on the screen or backing electrode increases the likelihood of arcing and reduces the charging efficiency of the corona device.

At high humidity, wet particulate material also increases the likelihood of electrical shorts and corona element corrosion.

Particulate material can also contaminate adjacent elements, such as photoconductors in electrophotographic imaging devices.

The problem of particulate material build-up within the corona charging device has been solved in prior art devices by periodic cleaning of the corona charging device and by periodic relining of the corona wire.

The mechanism by which particulate material is deposited within a corona charging device is not completely understood, and this deposition varies depending on whether a positive or negative corona discharge is generated.

Corona charging devices generate ozone, oxides of nitrogen, and ammonia from normal gases in the air, and these were believed to combine to form the particulate material, so all components of the particulate material has been thought to occur during normal operation of the corona charging device.

When corona devices are used in equipment that requires no maintenance over long periods of time, conventional solutions are no longer suitable.

While investigating alternatives to traditional methods, it was discovered that internally generated particulate material is only a small fraction of the total particulate material.

Oxides of nitrogen are generated in relatively large quantities in both positive and negative corona discharges, and these oxides react readily with ammonia, producing ammonium nitride particles, which appear to be the particulate material formed with the greatest concentration. It was found that it was formed.

However, considering the amount of ammonium nitride formed, it is unlikely that all of this occurred due to ammonia generation inside the corona device.

This is because the internal ammonia concentration is much too low to account for the generation of large amounts of ammonium nitride particulate material.

It has been found that the formation of particulate material is significantly influenced by the level of ammonia in the ambient air, which can be introduced externally into the corona charging device.

The main object of the present invention is to provide a corona charging device which does not allow the deposition of particulate material and thus achieves long term maintenance free operation.

Briefly summarized, the present invention provides a corona charging device via a filter device containing a chemically active material that reacts with constituents within the air stream to prevent the formation of particulate material in the corona device and related devices. to provide airflow.

The invention generally applies to corona charging devices used as ion generators for electrostatic charging.

However, embodiments of the present invention relate to electrophotographic reproduction machines where the problem of particulate material adhesion is particularly severe.

In the electrophotographic reproduction apparatus shown in FIG. 1, a rotating drum 1 supports an electrophotographic photoconductor member around its periphery, and upon this member it is desired that a continuous form paper 6 be formed. The image that appears is directed.

The surface of the photoconductor member is uniformly charged with a predetermined polarity by a corona charging device 2.

The charged surface is formed by a form flash device 3 or an exposure device 4.
is exposed to a light image to form an electrostatic latent image.

The electrostatic latent image is developed by a suitable development device 5 which cascades a mixture of toner and carrier onto the electrostatic latent image on the surface of the photoconductor member, as is known in the art.

The toner has a charge that is attracted to the surface of the drum to make the image visible.

The resulting toner image is transferred to continuous form paper 6 by transfer corona device 7.

The transfer corona device transfers ions of opposite polarity to the toner onto the paper 6.
This transfers the toner image from the drum 1 to the paper 6.

After transfer by the transfer corona device, the paper 6 is separated from the drum and sent to a fusing device 8 for fusing the toner and permanently fixing it to the paper.

Typically, not all of the l.toner image is transferred to the paper, so residual toner remains on the surface of the drum after the transfer operation.

In the cleaning device, the photoconductor member passes successively through an erasure lamp 9, a precleaning corona device 10 and a rotating cleaning brush 11.

Eraser lamp 9 discharges the photoconductor member, and precorona device 10 generates a charge to electrostatically attract residual image toner to cleaning brush 11, which attracts the toner to the photoconductor member. Sweep away from the surface.

Once this operation is complete, the drum imaging cycle is complete.

A control device 14 is provided which generates electrical control signals for controlling the operation of the various devices of the reproduction machine.

In this way, the position of the image on the drum can be determined such that the appropriate devices around the drum are activated at a given time.

Furthermore, the control device 14 serves as a temporary storage device for image data supplied to the exposure device 4, if desired.

According to the invention, the charged corona device 2 cooperates with an associated filter device 15 and an air flow generator 16.

This device is designed to prevent three types of contamination within the corona device: corrosion;
An air flow is generated through the filter device 15 and the corona charging device to reduce or eliminate particulate material deposition and dust.

In the illustrated embodiment, the filter device 15 comprises a particle filter that receives air from an air flow generator 16.

In this embodiment, the airflow generator 16 comprises a suitable blower.

Particle filter 20 is a device suitable for removing particles greater than about 1 micron in size from the air stream, and filter 20 serves to significantly reduce contamination of the corona charging device by dust.

Before entering the corona charging device, the air from the particle filter 20 is passed through an ammonia filter device 22 where the ammonia present in the air is removed by a chemical reaction and thus introduced into the charging corona charging device. Air that is substantially free of ammonia and dust is obtained.

This air is sent to the corona charging device 2 so as to keep the corona wire clean.

In addition, an air flow path within the corona charging device is provided such that any residual toner particles on the surface of the photoconductor member are kept away from the corona wire and these are carried out along with the ozone normally generated within the corona charging device. is set.

This air is passed to a suitable ozone filter 24 to remove ozone and the air from the ozone filter is either exhausted from the airflow system or returned to the system for recirculation.

A specific embodiment for the ammonia filter 22 is shown in the third example.
As shown in the figure.

Air from particulate filter 20 enters through air inlet 26, passes through a quantity of chemically active material 32 contained within housing 34, and exits through outlet 36.

Housing 34 is formed of or coated with a material that is chemically inert to chemically active materials and is designed to facilitate air flow through the filter.

The chemically active material is held in place by being sandwiched on either side by retaining member 28 and spacer member 30.

Retaining member 28 physically restrains the chemically active material and prevents air from passing freely through any suitable member.

Screens with an open area of more than 50% are suitable as holding members.

Spacer member 3o is a suitable chemically inert material, such as porous foam.

In certain embodiments, polyurethane foams having 15 to 30 pores per crfL have been found to be suitable for this purpose.

Retaining member 28 and spacer member 30 serve the dual function of holding the chemically active material in place and distributing air evenly throughout the filter.

The chemically active material consists of a suitable carrier material and an active ingredient, such as an acid, which reacts with the constituents of the air.

The carrier material can be porous or have a large surface area and can be adapted as a lifetime indicator (if used).

The active ingredient must react readily with the components to be removed in the air, have a low vapor pressure, and be chemically inert to the carrier material.

One suitable chemically active material is a carrier material such as activated carbon treated with a solution of sulfuric acid.

Activated carbon is soaked in sulfuric acid.

After this, the activated carbon is vacuum dried and, since the vapor pressure of sulfuric acid is very low, a significant amount of sulfuric acid is absorbed into the pores of the filter material.

A typical filter treated in this way is approximately 5% by weight.
Contains sulfuric acid.

Another chemically active material is a carrier material consisting of silica gel treated with a solution of phosphoric acid.

Silica gel is soaked in phosphoric acid.

After soaking, the silica gel was vacuum dried and a significant amount of phosphoric acid was absorbed into the open pores of the carrier material.

A typical filter treated in this manner may contain about 15% by weight phosphoric acid.

This configuration of the ammonia filter provides a large surface area for reaction with ammonia present in the air to be supplied to the corona charging device.

A specific embodiment of a corona charging device is shown in FIG.

The corona charging device consists of a plurality of corona wires 40 spaced apart from one another by a predetermined distance and a plurality of screen wires 42 spaced considerably narrower than the spacing between the corona wires. .

A suitable power supply 44 is provided to apply a corona generating potential of, for example, several kilovolts to the corona wire 40 and a lower potential to the screen wire 42.

This voltage is normally referenced to the photoconductor backing electrode, which is at ground potential.

An inner housing 48 is provided having an end member extending close to the surface of the photoconductor member to provide a controlled air flow through the corona charging device.

Remotely from the photoconductor, the housing 48 is provided with a perforated plate member 50;
The back section of the 0 acts as a manifold for the air directed into the corona charging device.

Air is directed from the outlet 36 of the ammonia filter in FIG. 3 by suitable conduit to the inlet 52 and through the apertures in plate 50 to the corona wire and screen.
Forced across the wire and toward the surface of the photoconductor member.

An outer housing 56 is provided in the corona charging device and an air outlet 54 is provided to create a pressure difference between the inlet air and the outlet air to produce a controlled air flow generally in accordance with the arrows shown. It is formed.

As a result of producing the illustrated air flow, all dust is removed from the corona wire and screen wire and is discharged through the outlet 54.

Furthermore, the ozone generated within the corona charging device is also discharged via this outlet.

The air flow along with debris and ozone contaminants is removed from the housing 56.
Air is drawn through the gap between the outer housing 56 and the photoconductor member to insure that these are removed through the corona charging device without being distributed to other parts of the reproduction apparatus. It is attracted to the charging device.

With the above device, the ammonia level in the air introduced into the corona charging device is less than 1 billion parts, which allows the corona charging device to operate without maintenance for long periods of time. This has the effect of eliminating the problem of adhesion of particulate materials.

Ammonia levels in the air vary significantly.

The average in uncontaminated air is about 6 parts per billion.

However, air near chemical processes that produce or use ammonia has much higher levels, perhaps reaching 500 parts per billion.

The amount of chemically active material in the filter determines the ammonia handling capacity of the filter.

Since the ammonia level in the air is variable, the life of the filter will also vary.

In devices that do not require maintenance for a long period of time, it is desirable to install an indicator that indicates the life of the filter.

This lifespan indicator is provided in the embodiment shown in FIG.

The indicator operates based on the change in pH of the system as the chemically active material changes, for example from phosphoric acid to ammonium phosphate.

This chemically active material is formed from a carrier material to which is added a suitable color indicator to indicate when the pH of the system has reached a critical value.

In the illustrated embodiment, a window 58 transparent to the spectrum of light from the light source 60 is provided in a recess in the housing 34'.

The light source 60 is imaged onto the window 58 by a suitable lens 62, and the reflected light from the window 58 is collected by the lens 64 and passed through a suitable color filter 66 to a photocell 68.

In a particular embodiment, the carrier material is silica gel treated as described above with phosphoric acid.

A suitable color indicator, such as crystal violet, is also introduced into the chemically active material 32'.

This material is normally pale yellow in color; however, at a specified critical pH to indicate the end of the filter's life, the color indicator material changes to a dark purple color and the amount of light reaching photocell 68 changes, and A suitable electrical signal can be generated by monitoring the output signal of the photocell.

Since filters are normally used up rather slowly, an indication of this is set to a value that occurs before 100% of the chemically active material is used up, so that the filter can be replaced at a convenient time for machine operation. The remaining period after the generation of the electrical signal allows the filter to operate normally.

The color change starts on the air inlet side of the filter and progresses towards the output side.

The vertical position of window 58 along the filter may be selected to be any particular position such that the display corresponds to the desired level of use.

An elongated transparent window may be mounted vertically in the housing 34' to provide a visual indication of the filter usage level.

It will be clear that the optical transmission device can be used for a filter end-of-life indicator that is sensitive to color changes or density changes.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electrophotographic apparatus embodying the present invention. 1... Rotating drum, 2... Corona charging device, 3... Form flash device, 4...
...K Optical device, 5...Development device, 6.
... Continuous form paper, 7 ... Transfer corona device, 8 ... Melting device, 9 ... Erasing lamp, 10 ... Preliminary cleaning Corona device, 11.
... Rotating cleaning brush, 14 ... Control device, 15 ... Filter device, 16 ... Air flow generation device. FIG. 2 is a schematic diagram of an air filter device embodying the present invention. 2... Corona charging device, 16... Air flow generator, 20... Particle filter, 22...
...Ammonia filter, 24...Ozone filter. FIG. 3 is a partial cross-sectional view of an ammonia filter. 34... Housing, 26... Air inlet, 36... Outlet, 32... Chemically active material, 30... Spacer Part, 28...
...Holding member. FIG. 4 is a cross-sectional view of the corona charging device to show the air passage through the corona charging device. 40... Corona wire, 42... Screen wire, 44... Power supply, 48...
...Inside...Using, 50...Perforated plate, 5
6...External...Using, 52...Inlet, 54...Outlet. Figure 5 shows an ammonia sample with a usage level sensing device added.
FIG. 3 is a partial cross-sectional view of the filter. 34'...Housing, 58...Window,
60...Light L62...Lens, 64.
... Lens, 66 ... Color filter, 68
. . . Photocell, 32′ . . . Chemically active material into which color indicator material is introduced.

Claims (1)

[Claims] 1. A corona charging device having the following (a) to ←→. (a) A charge generating means that generates a charge on the surface. (b) means for generating an air flow that flows along a predetermined path through the charge generating means; ←→ Filter means positioned within the passageway between the air flow generating means and the charge generating means such that the air flow enters. The filter means includes a carrier material which is a chemically active material treated with an acid to effect a chemical reaction with the undesirable gaseous ammonia component contained in the air stream.