JPH11143184A - Cleaning control method for corona electrifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corona electrifier cleaning and control method capable of preventing the deterioration of the corona electrifier (re-electrifier) by the excessive cleaning, while raising the cleaning property of the corona electrifier. SOLUTION: In an electrophotographic device provided with two or more developing devices for developing the same photoreceptor drum (photoreceptor), and a wire cleaning pad (cleaning means) 19 for cleaning corona discharge wire 18 and the corona electrifier (re-electrifier) 6 provided with the grid cleaning pad (cleaning means) 23 for cleaning the grid wire 22 between two developing devices, the cleaning frequency or the cleaning interval for the corona discharge wire 18 and the grid wire 22 by the wire cleaning pad 19 and the grid cleaning pad 23 is respectively controlled in accordance with the number of image sheets or the number of picture elements to be sensitized by the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the cleaning of a corona charger provided in an electrophotographic apparatus such as an electrostatic copying machine, an image recording apparatus, a printer and a facsimile.

[0002]

2. Description of the Related Art A conventional two-color image forming method will be described with reference to an electrophotographic apparatus shown in FIG.

The electrophotographic apparatus shown in FIG. 1 employs a so-called two-color multiplex developing method, in which the surface of a photosensitive drum 1 as a latent image forming medium which is driven to rotate is uniformly charged by a first charger 2. After the first charging, the first image exposure 3 is performed to form a first latent image on the photosensitive drum 1, and the first latent image is developed by the first developing device 4 using the first toner 5, After the surface of the photosensitive drum 1 is uniformly and again charged by the second charger (recharger) 6, a second image exposure 7 is performed to form a second latent image on the photosensitive drum 1, and the second latent image is formed. The latent image is developed by the second developing device 8 using the second toner 9 having a different color from the first toner 5 to form a two-color image on the photosensitive drum 1 using the two-color toner.

In an electrophotographic apparatus employing such a two-color multiplex developing method, due to its structure, the space between the first developing device 4 and the second charger (recharger) 6 and the second charger (recharger) are provided. No means such as a cleaner for removing the toner on the photosensitive drum 1 is arranged between the device 6 and the second developing device 8. For this reason, when the first toner 5 adhered to the first latent image on the photosensitive drum 1 by development passes through the charger (recharger) 5 every time an image is formed, the second charger (rechargeable) is scattered by toner or the like. Charger)
6 is contaminated with toner, or the toner scattered in the second developing device 8 reaches the second charger (recharger) 6 and is similarly contaminated with toner. It is known that the deterioration of the stain on the charger 6 proceeds faster than the first charger 2.

The degree of contamination of the second charger (recharger) 6 is somewhat proportional to an increase in the number of image formations in the first developing device 4 and poor toner scattering in the second developing device 8. A developing method in which the moving direction (rotating direction) of the sleeve 8a of the second developing device 8 is opposite to the moving direction (rotating direction) of the photosensitive drum 1 near the nip with the photosensitive drum 1 (hereinafter, referred to as a counter developing method). In the case of (1), since the scattering of the toner is exerted in the upstream direction of the photosensitive drum 1, it greatly affects the contamination of the second charger (recharger) 6. As a matter of course, the same problem also occurs in a multicolor multi-developing electrophotographic apparatus having two or more developing units.

In order to solve such a problem, the conventional method has a second problem.
The number of cleaning times of the charger is made larger than that of the first charger,
This has been addressed by increasing the cleaning performance of the second charger by shortening the cleaning interval.

[0007]

However, when the above method is adopted, the corona discharge wire and the grid wire of the second charger (a scorotron-type corona charger) are strongly polished by the cleaning means. Obviously, the life of the corona discharge wire and the grid wire is shorter than that of the vessel. As a result, the maintenance interval of the second charger is shortened, and the frequency of replacement is increased, thereby causing a problem that the overall maintenance cost is increased. The reason is that the frequency of color image output and the frequency of black image output differ depending on the intended use of the user,
If the cleaning frequency and the number of times of the charging device are uniformly defined, it is conceivable that cleaning of the charging device is insufficient or the cleaning process is performed excessively due to a variation in the use frequency of the black image and the color image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to improve the corona charger (recharger) cleaning performance and to improve the corona charger (recharger) by excessive cleaning. An object of the present invention is to provide a method for controlling the cleaning of the corona charger, which can prevent the deterioration of the corona charger.

[0009]

In order to achieve the above object, the invention according to claim 1 has two or more developing devices for developing the same photoreceptor, and cleans at least a corona discharge wire or a grid wire. In an electrophotographic apparatus in which a corona charger having means is disposed between two developing devices, the number of times of cleaning or the cleaning interval by the cleaning means depends on the number of images or the number of pixels to be visualized by the developing device. Control.

According to a second aspect of the present invention, in the first aspect of the invention, the number of times of cleaning or the cleaning interval of the corona discharge wire by the cleaning means is increased by the developing device disposed upstream of the corona charger. The control is performed in accordance with the number of images or the number of pixels to be converted.

According to a third aspect of the present invention, in the first aspect of the present invention, the number of cleanings or the cleaning interval of the grid wire by the cleaning means is visualized by the developing device arranged upstream of the corona charger. The control is performed in accordance with the number of images or the number of pixels to be performed.

According to a fourth aspect of the present invention, there is provided a corona charger having two or more developing devices for developing the same photoreceptor and having a cleaning means for cleaning a corona discharge wire is provided between the two developing devices. In addition, in an electrophotographic apparatus in which the rotation direction of the sleeve of the developing device located in the photoconductor rotation direction of the corona charger is opposite to the rotation direction of the photoconductor in the vicinity of the nip portion with the photoconductor, The cleaning interval of the corona discharge wire is controlled in accordance with the number of images or the number of pixels to be visualized by a developing device located downstream of the corona charger.

According to a fifth aspect of the present invention, a corona charger having two or more developing devices for developing the same photoreceptor and having a cleaning means for cleaning a grid wire is disposed between the two developing devices. An electrophotographic apparatus in which the rotation direction of the sleeve of the developing device positioned in the photoconductor rotation direction of the corona charger is opposite to the rotation direction of the photoconductor near the nip portion with the photoconductor; The cleaning interval of the wire is controlled in accordance with the number of images or the number of pixels to be visualized by a developing device located downstream of the corona charger.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a schematic structural view of a two-color electrophotographic apparatus to which the present invention is applied. The two-color electrophotographic apparatus is provided around a photosensitive drum 1 which is a latent image forming medium. ,
It comprises a first charger 2, an exposure device for performing first image exposure 3, a first developing device 3, a second charger (recharger) 6, an image exposure device for performing second image exposure 7, and the like. I have.

Thus, in this two-color electrophotographic apparatus, the surface of the photosensitive drum 1 is uniformly and uniformly charged by the first charger 2, and then the first image exposure 3 is performed to place the first image on the photosensitive drum 1. A first latent image is formed, and the first latent image is developed with a first developing device 4 using a first toner 5 to form a first toner image, and then a second charger (recharger) 6 Photosensitive drum 1
After the surface is uniformly charged again, a second image exposure 7 is performed to form a second latent image, and the second latent image is formed by the second developing device 8 into a second latent image having a color different from that of the first toner 5. A second toner image is formed by developing using the second toner 9. Thus, a two-color image is obtained on the photosensitive drum 1 by the two-color multiplex development method.

Thereafter, the two-color image on the photosensitive drum 1 is collectively transferred onto transfer paper by a transfer charger (not shown), and the transfer paper having received the transfer of the two-color image is sent to a fixing device (not shown). After the two-color image is fixed, a two-color image is formed. In this manner, all the steps of the two-color image by the two-color multiple development method are completed, and the two-color print is discharged out of the apparatus.

Next, the scanning system of the two-color electrophotographic apparatus will be described.

In FIG. 1, image data transferred from a reader unit (for a copying machine) or an interface (I / F) block (for a printer) (not shown) to an image processing circuit 10 is shaded by the image processing circuit 10. Correction, pattern processing, LOG conversion (brightness density conversion)
And a gamma correction (density correction) are performed to convert each pixel into a pixel image signal having an output level corresponding to the density of the pixel.

Next, the image data is converted into a video signal in the image processing circuit 10, and the video signal of the image data is sent to the cleaning sequence control circuit 16 and the laser driver board 11. This cleaning sequence control circuit 16
Is a circuit for controlling the cleaning sequence of the second charger 6, and there is another circuit for controlling the cleaning sequence of other chargers (primary charger, transfer charger, separation charger, etc.). .

The laser driver substrate 11
Generates and outputs a laser drive pulse alternately for the first latent image and for the second latent image in accordance with the input video signal, and the laser drive pulse is supplied to the laser light emitting device 12 to generate the laser light. Flash.

Next, the first latent image laser beam and the second latent image laser beam emitted from the laser emitting device 12 (image exposure)
3, 7 are swept by the rotating polygon mirror 13, respectively.
A spot image is formed on the surface of the photosensitive drum 1 by a lens 14 such as an f / θ lens and a fixed mirror 15 for directing the laser light toward the photosensitive drum 1. In this manner, the laser beams 3, 7 scan the photosensitive drum 1 in a direction (main running direction) substantially parallel to the rotation axis on the photosensitive drum 1, and form an electrostatic latent image on the photosensitive drum 1. .

FIG. 2 is a schematic structural view of the second charger 6.
The second charger 6 has a corona discharge wire and a grid automatic cleaning mechanism.

The corona discharge wire 18 is stretched between both ends of a corona charger block (not shown), and a predetermined tension is applied to the corona discharge wire 18 by a spring (not shown) provided at one end thereof. Is given.

Power is supplied to the corona discharge wire 18 from a main body connector (not shown) via power supply terminals (not shown), power supply pins, springs, and the like. A wire cleaning pad 19 is provided so as to sandwich the corona discharge wire 18 from both sides. The wire cleaning pad 19 is supported by a cleaning pad support member 20 and can be replaced alone.

The cleaning pad supporting member 20 is screwed onto a screw 21 and moves along the corona discharge wire 18 by the rotation of the screw 21. The screw 21 can rotate via a gear according to the rotation of a motor (not shown). Since the motor can rotate in an arbitrary rotation direction in response to a control signal from the cleaning sequence control circuit 16 shown in FIG. 1, the cleaning pad supporting member 20 can freely move back and forth along the corona discharge wire 18. .

On the other hand, the grid wire 22 is stretched between both ends of a corona charger block (not shown), and is electrically connected to an electrode terminal and a shield 26 (not shown). The grid cleaning pad 23 is installed so as to sandwich the grid wire 22. The grid cleaning pad 23 is supported by a grid cleaning pad support member 24, and only the grid cleaning pad 23 can be replaced.

The grid cleaning pad support member 24 is screwed onto a screw 25, and is movable along the grid wire 22 by the rotation of the screw 25.
The screw 25 can rotate via a gear according to the rotation of a motor (not shown). Since the motor can rotate in an arbitrary rotation direction in response to a control signal from the cleaning sequence control circuit 16 shown in FIG. 1, the grid cleaning pad support member 24 can freely move back and forth along the grid wire 22. .

That is, the wire cleaning pad 19 and the grid cleaning pad 23 are reciprocated along the corona discharge wire 18 and the grid wire 22 by driving a motor (not shown) in response to a control signal from the cleaning sequence control circuit 16, and The discharge wire 18 and the grid wire 22 can be cleaned.

Here, the processing steps of the cleaning sequence control circuit 16 will be described with reference to the flowchart shown in FIG.

This processing step differs depending on whether the image data handled by the electrophotographic apparatus is binary or multi-valued. Also, the first
The case where the control is performed based on the number of images visualized by the developing device is different from the case where the control is performed based on the number of pixels that are visualized. In the present embodiment, the following (1) to (1) to processing steps in the case where image data handled by the electrophotographic apparatus is a binary signal and control is performed based on the number of images to be visualized in the first development. The process (4) will be described. (1) When a video signal is input from the image processing circuit 10 to the cleaning sequence control circuit 16 at the time of image formation, the value of the cleaning counter C1 is incremented by one every time the first latent image of the video signal is output per image. . The cleaning counter C1 is stored in the memory 17 shown in FIG. 1, and the value of the cleaning counter C1 is 0 in the initial setting of the main body. (2) The cleaning counter C1 is compared with the cleaning determination value Cs. Then, when the cleaning counter C1 is equal to or more than the cleaning determination value Cs (C1 ≧ Cs), the processing after the step (3) is performed. The cleaning counter C1 is smaller than the cleaning determination value Cs (C1 <
If Cs), the process ends. Cleaning counter C
1 is stored in the memory 17 and is 3000 in the initial setting of the main body. (3) The cleaning frequency value Ctd is added to the cleaning determination value Cs. The cleaning frequency value Ctd is stored in the memory 17, and is 2,000 in the initial setting of the main body. (4) The cleaning sequence control circuit 16 sends a cleaning start signal for the second charger 6 to a main body controller (not shown).
Then, as soon as the continuous image forming operation is completed, the main body controller controls the corona discharge wire 18 of the second charger 6.
And the cleaning operation of the grid wire 22 is started.

In the above processing steps, the cleaning counter C1, the cleaning judgment value Cs, and the cleaning frequency value Ctd are each set to an initial value at the time of shipment from the factory. However, the initial value may be set when the main body is installed. May be reset according to the installed temperature and humidity environment or the user's request.

In the processing steps (1) to (4), the cleaning sequence of the second charger 6 is controlled based on the video signal of the first latent image. Or the cleaning sequence control based on the video signals of both the first latent image and the second latent image, taking into account the effect of toner scattering of the second developing device 8. By performing cleaning control,
The cleaning property of the charger 6 can be further improved.

<Embodiment 2> In the present embodiment, a video signal output from the image processing circuit 10 at the time of forming the first latent image in Embodiment 1 is used as a reference, and the number of images of the first latent image is changed. Thus, the cleaning sequence of the corona discharge wire 18 of the second charger 6 is controlled.

<Embodiment 3> In the present embodiment, a video signal output from the image processing circuit 10 at the time of forming the first latent image in Embodiment 1 is used as a reference and the number of images of the first latent image is changed. Thus, the cleaning sequence of the grid wire 22 of the second charger 6 is controlled.

<Embodiment 4> This embodiment is directed to a counter-type developing system in which the rotation direction of the sleeve 8a of the second developing device 8 in the first embodiment is opposite in the vicinity of the nip portion with the photosensitive drum 1. The cleaning sequence control of the corona discharge wire 18 of the second charger 6 is performed according to the number of images of the second latent image.

<Embodiment 5> This embodiment is directed to a counter-type developing system in which the rotation direction of the sleeve 8a of the second developing device 8 in the first embodiment is opposite to that in the vicinity of the nip with the photosensitive drum 1. The grid wire 2 of the second charger 6 is used in accordance with the number of images of the second latent image.
The second cleaning sequence control is performed.

[0038]

As is apparent from the above description, according to the present invention, there are provided two or more developing devices for developing the same photoreceptor and a cleaning means for cleaning at least a corona discharge wire or a grid wire. In an electrophotographic apparatus in which a corona charger is disposed between two developing devices, the number of times of cleaning or the cleaning interval by the cleaning means is controlled according to the number of images or the number of pixels to be visualized by the developing device. Therefore, the effect of preventing deterioration of the corona charger (recharger) due to excessive cleaning can be obtained while improving the cleanability of the corona charger (recharger).

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a two-color electrophotographic apparatus to which the present invention is applied.

FIG. 2 is a configuration diagram of a second charger of the two-color electrophotographic apparatus to which the present invention is applied.

FIG. 3 is a flowchart illustrating processing steps of a cleaning sequence control circuit.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (photoreceptor) 2 first charger (corona charger) 4 first developer (developing device) 6 second charger (corona charger) 8 second developer (developing device) 16 cleaning sequence control circuit 18 Corona discharge wire 19 Wire cleaning pad (cleaning means) 22 Grid wire 23 Grid cleaning pad (cleaning means)

Claims (5)

[Claims] 1. A corona charger having at least two developing devices for developing the same photoreceptor and having at least a cleaning means for cleaning a corona discharge wire or a grid wire is disposed between the two developing devices. In the electrophotographic apparatus, a cleaning control method for a corona charger, wherein a number of times of cleaning or a cleaning interval by the cleaning unit is controlled according to the number of images or the number of pixels to be visualized by the developing device. 2. The method according to claim 1, wherein the number of cleanings or the cleaning interval of the corona discharge wire by the cleaning unit is controlled in accordance with the number of images or the number of pixels to be visualized by the developing device disposed upstream of the corona charger. Claim 1 characterized by the following:
The cleaning control method of the corona charger described in the above. 3. The method according to claim 1, wherein the number of cleanings or the cleaning interval of the grid wire by the cleaning unit is controlled according to the number of images or the number of pixels to be visualized by the developing device arranged upstream of the corona charger. The method for controlling cleaning of a corona charger according to claim 1, wherein: 4. A corona charger having two or more developing devices for developing the same photoconductor and having a cleaning means for cleaning a corona discharge wire is disposed between the two developing devices. In the electrophotographic apparatus, the rotation direction of the sleeve of the developing device positioned in the photoconductor rotation direction is opposite to the rotation direction of the photoconductor in the vicinity of the nip portion with the photoconductor, and a cleaning interval of the corona discharge wire by the cleaning unit. Controlling the cleaning of the corona charger according to the number of images or the number of pixels to be visualized by a developing device located downstream of the corona charger. 5. A corona charger having two or more developing devices for developing the same photosensitive member and having a cleaning means for cleaning a grid wire is disposed between the two developing devices. An electrophotographic apparatus in which the rotation direction of the sleeve of the developing device positioned in the body rotation direction is opposite to the rotation direction of the photoconductor in the vicinity of the nip portion with the photoconductor, wherein a cleaning interval of the grid wire by the cleaning unit is corona. A cleaning control method for a corona charger, wherein the control is performed in accordance with the number of images or the number of pixels to be visualized by a developing device located downstream of the charger.