JPH041787A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the splashing of a developer to the surrounding even if a transfer material moves in a narrow transporting path by disposing panel electrodes which generate the potential of the same polarity as the electrostatic charge potential of the developer forming a developed image on the developed image side of the transfer material in the transporting path. CONSTITUTION:The sheet-like electrodes 30, 30 are stuck to the rear surface int he lower part 13c of a cleaning device 13 facing the toner image side on transfer paper P in proximity thereto or the rear surface of a drum shutter 24 and the negative voltage is impressed thereto by a power source 31. The potential of the same polarity as the electrostatic charge potential of the toner T is generated on the rear surface in the lower part 13c of the cleaning device 13 in proximity to the transfer paper P or the rear surface of the drum shutter 24 by the sheet-like electrodes 30, 30. The trouble that the developer on the transfer material moves and splashes to the developed image side of the transporting path and contaminates the transporting path is eliminated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus employing electrophotography, such as a copying machine or a laser beam printer.

(Prior Art) FIG. 4 shows a cross section of the process cartridge 14 and its peripheral equipment when the process cartridge 14 is installed in the main body of an image forming apparatus. The process cartridge 14 integrally houses a photosensitive tram 1O1 which is an image carrier, a developing device 12, a cleaning device 13, etc. in a cartridge container 14a, and is attached to and detached from the main body of the apparatus as a whole, so that the internal equipment can be adjusted. When the process cartridge 14 reaches the end of its life, maintenance is facilitated by replacing the entire process cartridge 14.

Now, regarding the case where an image is formed using negatively charged developer (toner) T, an outline of the image forming operation will be explained with reference to FIG. 4. When the electrostatic latent image is formed, toner T is supplied to the electrostatic latent image by the developing device 12, and the electrostatic latent image is visualized as a toner image (developed image). The toner image is transferred onto a transfer paper (transfer material) P by a transfer roller 15, and this transfer paper P carrying the toner image is sent to a fixing device (not shown) over a support guide 20. The fixing device fixes the toner image onto the transfer paper P as a permanent image. Further, residual toner on the photosensitive drum 10 after the transfer is scraped off by the cleaning plate 13a of the cleaning device 13, and collected into the cleaning device 13 via the scooping sheet 13b.

Here, 24 is a tram shutter for protecting the photosensitive tram 10, and when the process cartridge 14 is installed in the main body of the apparatus, this tram shutter 24 is retracted onto the support guide 20 below the cleaning device 13. ing.

Furthermore, the lower portions of the tram shutter 24 and the cleaning device 13 are disposed close to the support guide 20, and therefore, the conveyance path of the transfer paper P in this part has a narrow vertical interval so as to sandwich the transfer paper P. There is.

(Problem to be Solved by the Invention) However, the cleaning device 13 and drum shutter 24 of the process cartridge 14 are made of resin, etc., and charges are likely to be generated and accumulated in a low humidity environment. When a positive charge is accumulated on the toner T, the negatively charged toner T on the transfer paper P conveyed on the support guide 28 moves toward the cleaning device 13 and the tram shutter 24, and these are transferred to the toner T. There was a problem with it getting dirty.

Here, the charge is accumulated in the cleaning device 13 by the rubbing of the cleaning plate 13a and the thin sheet 13b against the photosensitive tram 10, and the charge is accumulated in the drum shutter 24 by the movement of the charge from the cleaning device 13, etc. Live.

The present invention has been made to solve the above problem, and its purpose is to prevent the developer from scattering around the transfer material carrying the unfixed developed image even when the transfer material is moved through a narrow conveyance path. The present invention provides an image forming apparatus.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an image forming apparatus in which a transfer material carrying an unfixed developed image or a narrow transport path sandwiching the transfer material is transported. The method is characterized in that a planar electrode is disposed on the developed image side of the transfer material in the path to generate a potential having the same polarity as the charged polarity of the developer forming the developed image.

(Function) When a transfer material carrying an unfixed developed image is transported through a narrow transport path, a portion of the transport path facing the developed image is charged with a charge of a polarity different from that of the developer forming the developed image. When accumulated, the developer on the transfer material moves toward the conveyance path, which is disadvantageous in that the developer contaminates the conveyance path.

Therefore, an on-surface electrode that generates an electric potential of the same polarity as the developer on the transfer paper or an alternating current potential of changing polarity is arranged on the part of the conveyance path facing the developed image side, and an electrical repulsion force is used to generate an alternating current potential of the same polarity as the developer on the transfer paper. This prevents the developer from moving toward the conveyance path.

(Example) Embodiments of the present invention will be described below based on the accompanying drawings.

First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

First, an overview of the image forming apparatus will be explained with reference to FIG.
In the figure, reference numeral 10 denotes a photosensitive drum which is an image bearing member, and surrounding the photosensitive drum 10 are a primary charger 11, a developing device 12, a cleaning device 13, and so on. A transfer roller 15 is also provided. The devices other than the transfer roller 15 are arranged in a cartridge container 14a, and are configured to be integrally attached to and detached from the apparatus main body l as a process cartridge 14. Maintenance is facilitated by replacing the entire process cartridge 14 when the toner T in the developing device 12 is used up.

Also, on the upstream side of the photosensitive drum IO, there is a paper feed cassette) 16,
Paper feed roller 17, registration roller 18° conveyance guide 19
A support guide 2 is provided on the downstream side of the photosensitive tram 10.
0, a fixing device 21, and a paper discharge tray 22 are provided. Further, a photosensitive tram l is provided above the process cartridge 14.
A scanner unit 23 for exposing image light is disposed at O.

Note that 24 is a drum shutter, which protects the photosensitive tram 10 by covering the surface of the photosensitive tram 10 exposed to the outside from the cartridge container 14a when the process cartridge 14 is outside the apparatus main body l. When the process cartridge 14 is installed in the main body of the apparatus, the tram cover 24 is retracted below the cleaning device 13.

That is, when only image light is exposed from the scanner unit 23 onto the photosensitive drum 10, which has been uniformly charged by the -order charger 11, an electrostatic latent image force f is formed on the photosensitive drum IO.

The electrostatic latent image is transferred to the developing device 12 as the photosensitive drum 10 rotates.
Toner (developer) T is supplied through the developing sleeve 12a of the developing device 12 and converted into a toner image (developed image). The toner image is directed toward the transfer roller 15, and is transferred onto the transfer paper (transfer material) P by the transfer roller 15. After the transfer, the remaining toner is easily removed from the cleaning blade 13a of the cleaning device 13 on the photosensitive drum IO. The transfer paper P, which is cleaned by the clean sheet 13b and prepared for the next image formation, is taken out one by one from the paper feed cassette 16 via the paper feed roller 17 and is sent toward the registration roller 18. After that, the registration roller 18 adjusts the timing and sends the toner image toward the photosensitive drum 10, and the toner image on the photosensitive drum 10 is transferred by the transfer roller 15.

Then, the transferred transfer paper P moves on the support guide 20 while carrying the toner image on its upper surface, and is sent to the fixing device 21, where the toner image is heated,
After being fixed on the transfer paper P by applying pressure, etc., the paper is transferred to the output tray 2.
It is loaded on 2.

Here, the photosensitive drum 10 used is one that is negatively charged by the primary charger 11, such as an OPC photosensitive member, and the toner T in the developing device 12 is also negatively charged.
The development method is a reversal development method. Therefore, the first
As shown in the figure, negatively charged toner T is placed on the transfer paper P after the transfer.

Now, as shown in detail in FIG. 1, a cleaning device 13 and a drum shutter 24 are disposed on the support guide 20 for the transfer paper P, and only a small gap is formed for the conveyance of the transfer paper P. In addition, the cleaning device 13 and the drum shutter 24 are made of resin or the like, and in a low humidity environment, charges are likely to accumulate, and due to the effects of friction between the cleaning blade 13a of the cleaning device 13 and the deep sheet 13b with the photosensitive drum 10, etc. Positive charges may be accumulated on the lower part 13c of the cleaning device 13 and the drum shutter 24. In such a case, a part of the toner T on the transfer paper P moves to the lower part 13c of the cleaning device 13 and the tram shutter 24 side due to the electric attraction force, and these devices are contaminated with toner.

Therefore, in the present invention, a sheet-like electrode 30.30 is attached to the lower surface of the lower part 13c of the cleaning device 13 facing close to the toner image side on the transfer paper P and the lower surface of the drum shutter 24. A negative voltage was applied to 30 by a power source 31.

Since a potential of the same polarity as the toner T is generated on the lower surface of the lower part 13c of the cleaning device 13 close to the transfer paper P and the lower surface of the drum shutter 24 by the sheet-like electrodes 30, 30, it is possible to Also, the toner T on the transfer paper P is removed by the cleaning device 13 or the drum shutter 24.
Therefore, the inconvenience that the cleaning device 13 and the drum shutter 24 are contaminated by the toner T does not occur.

That is, since the process cartridge IO will not be contaminated with toner T during the operation of the device, the process cartridge
When replacing O, the operator does not get his/her hands or clothes dirty, or when the process cartridge 1O is temporarily placed, the toner T adhering to the process cartridge 1O does not stain the surrounding area. The same thing can be said when attaching and detaching the process cartridge 10 to and from the apparatus main body 1 for maintenance purposes.

Furthermore, even when using positively charged toner T, by applying a positive voltage to the sheet electrode 30, 30,
The invention is equally applicable. Furthermore, even if a positively charged photoreceptor such as selenium (Se) or amorphous silicon type is used as the photoreceptor drum 1O, the sheet-like electrode 3 is adjusted according to the charge of the toner T used.
A positive or negative voltage may be applied to 0°30.

Next, a second embodiment of the present invention will be described with reference to FIG. Components having the same functions as those in the first embodiment are designated by the same reference numerals, and their explanations will be omitted.

In this embodiment, a case will be described in which the present invention is applied to an image forming apparatus equipped with a static elimination needle 40 in order to improve the separability of the transfer paper P from the photosensitive tram 10.

The static eliminating needle 40 is held by a holder 41 disposed below the transfer paper P immediately downstream of the photosensitive drum IO, and the holder 41 is supported by the support guide 20. In this embodiment as well, it is assumed that the development method is a reversal development method in which the photosensitive drum 10 is negatively charged and the toner T in the developing device 12 is also negatively charged.

The static elimination needle 40 serves as a separation assisting means for improving the separation of the transfer paper P from the photosensitive drum 10 when the transfer is performed by the transfer roller 15 or by a positive bias voltage in the above-mentioned reversal development method. The separability of the charged transfer paper P is improved by negatively charging or removing the charge.

Generally, a bias voltage of -1 to -3 KV is applied to the static elimination needle 40. This applied voltage is determined by considering the quality of the transfer paper P and the latitude with respect to the environment, so depending on the conditions, excessive charge or transfer may occur. The electric potential is applied onto the paper P, and in some cases, the potential of the transfer paper P may even be the same as the potential of the static eliminating needle 40. In this case, the negatively charged toner T on the transfer paper P becomes more likely to adhere to the lower surface of the lower part 24c of the leaning device 24 and the lower surface of the tram shutter 24.

Therefore, a sheet-shaped electrode 30.30 is attached to the lower surface of the lower part 24c of the cleaning device 13 disposed close to the toner image on the transfer paper P and the lower surface of the tram shutter 24, and the sheet-on electrode 30. By applying a negative potential to 30, the transfer paper P
The toner T carried on the top is prevented from moving toward the cleaning device 13 or the tram shutter 23.

As shown in the figure, a negative voltage is applied to the sheet electrode 30.30 and the static elimination needle 40 by a power source 31 via resistors R1 and R2.
KV, and when applying a voltage of -2 KV to the static eliminating needle 40, the resistor R1 may be 100 MΩ and the resistor R2 may be 200 MΩ.

Next, a third embodiment of the present invention will be described with reference to FIG. Components having the same functions as those in the first and second embodiments are designated by the same reference numerals and their explanations will be omitted.

Said 1st. In the second embodiment, the sheet electrode 30.3
By applying a DC bias voltage to the cleaning device 1
In this embodiment, a case will be described in which an alternating current bias voltage is applied to the sheet electrodes 30 and 30 to prevent the toner T from adhering to the electrodes 30 and drum shutter 24. That is, the first
This is a case where the three power supplies in the figure are replaced with AC power supplies.

In this case, when the photosensitive drum IO is negatively charged and the toner T used is negatively charged, the sheet-like electrode 30.30 has a peak-to-peak voltage (VPP) of 2.
When a bias voltage of KV is applied, the sheet-like electrode 30.
When the voltage applied to 30 is positive, the sheet electrode 3
Toner T is attracted to 0.30, and is repelled when it is negative.

Here, if the frequency (Vr) of the alternating current is small, the toner T will reciprocate between the sheet electrode 30, 30 and the transfer paper P, or if the frequency (Vr) is sufficiently large (for example, CI
1KH2 or more), the toner T is pushed back toward the transfer paper P before reaching the sheet-like electrodes 30, 30, and does not adhere to the cleaning device 13 or the tram shutter 24.

As described above, this embodiment can also achieve the same effects as the first embodiment.

Furthermore, since the method of applying an AC bias voltage to the sheet-like electrodes 30° and 30 can be applied regardless of the charging electrode (negative or positive) of the toner T, it is possible to This is particularly effective in the case of contact transfer (for example, belt transfer, roller transfer) in which a large amount of toner) is easily transferred.

Above are the first and second points. Regarding the third embodiment, an image forming apparatus using the process cartridge 14 has been described.
The present invention is not limited to the presence or absence of the process cartridge 14, and can also be applied to an image forming apparatus in which the photosensitive tram 10 and the cleaning device 13 can be independently attached to and detached from the apparatus main body 1. That is, the present invention can prevent the photosensitive drum 10 and the cleaning device 13 from becoming dirty, and can provide the worker with a clean working environment.

(Effects of the Invention) As is clear from the above description, according to the present invention, the developer that forms the developed image is placed on the developed image side of the transfer material that carries the unfixed developed image in the narrow conveyance path of the transfer material. Because the transfer material is equipped with a planar electrode that generates electrical repulsion, the developer on the transfer material moves toward the developed image side of the conveyance path and scatters, contaminating the conveyance path with the developer. There is no inconvenience.

[Brief explanation of the drawing]

FIG. 1 is a sectional view around the process cartridge of an image forming apparatus according to the first embodiment, FIG. 2 is a side sectional view of the same image forming apparatus, and FIG. 3 is a process cartridge of the image forming apparatus according to the second embodiment. A sectional view of the surrounding area, FIG. 4, is a diagram for explaining the prior art. 30...Sheet electrode (planar electrode), P...Transfer paper (transfer material), T-)ner (developer). Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] In an image forming apparatus in which a transfer material carrying an unfixed developed image is transported through a narrow transport path sandwiching the transfer material, a developer that forms the developed image is placed on the developed image side of the transfer material in the transport path. An image forming apparatus characterized by disposing a planar electrode that generates a potential having the same polarity as a charging polarity.