JPH0455510B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a transfer device that is used in an electrophotographic copying machine and maintains good transfer performance regardless of whether the humidity is high or low.

<Prior Art> Normally, in a transfer type electrophotographic copying machine, a toner image formed on a photoreceptor is electrostatically transferred onto copy paper by a corona discharge device after each copying process of charging, exposure, and development. Ru. This transfer transfers the toner particles electrostatically adhered to the charged areas on the photoreceptor to the same polarity as the charge on the photoreceptor and to the toner particles imparted onto the copy paper by the corona discharge device. Charged charges are charged charges of different polarity that are attracted and transferred onto copy paper. therefore,
Whether or not the electrical charge applied to the copy paper is sufficient for transfer is an extremely important condition for the success or failure of transfer.

The copy paper is initially stored in a cassette or the like, and after the copy cycle is energized, it is transported to a transfer area along a paper guide via a paper feed and transport device at a predetermined time. After the transfer is performed in this transfer area, the copy paper is transferred along another paper guide to a fixing section for fusing and fixing the toner image. Here, the paper guide is usually made of a conductive material (metal),
The copy paper is conveyed while contacting this paper guide.

<Problems to be Solved by the Invention> Therefore, in general, under high humidity conditions, copy paper contains a large amount of moisture in the air, so its electrical resistance decreases, and during the above-mentioned transfer, the electrical resistance of the copy paper is reduced. A situation occurred in which electric charges flowed through the paper guide to the frame (grounded part) of the copy paper body. Therefore, there is no charge on the copy paper to sufficiently attract the toner image on the photoreceptor,
As a result, the resulting copy becomes a defective image with partially or entirely white spots.

An object of the present invention is to enable good toner image transfer without being affected by humidity.

<Means for Solving the Problems> The toner image transfer device of the present invention includes a first paper guide that guides the copy paper to the transfer area, and a second paper guide that guides the copy paper that has been peeled off from the photoreceptor. A changeover switch made of a conductive material, electrically insulated from the copying machine body, and connected between the two paper guides and the grounding part of the copying machine body controls both paper guides according to humidity conditions. It is characterized by insulation separation from the grounding part or direct short-circuiting to the grounding part.

<Function> According to the toner image transfer device of the present invention, both paper guides are electrically insulated and separated from the grounding portion of the copying machine body by the switch when the humidity is high. Therefore, the charge charged on the copy paper by the transfer corona discharger can be prevented from escaping to the ground portion via both paper guides.

Therefore, the toner image formed on the photoreceptor can be transferred satisfactorily by the electric charges on the copy paper.

<Example> FIG. 1 is a cross-sectional view showing a toner image transfer portion in an electrophotographic copying machine according to the present invention. In the figure, reference numeral 1 denotes a drum-shaped photoreceptor that is rotated in the direction of the arrow. The photoreceptor undergoes each copying process (not shown) of charging, exposure, and development arranged so as to face its circumferential surface, and a toner image 2 corresponding to the image of the document is formed on its surface. Reference numeral 3 designates upper and lower paper guides 3a and 3b that guide the copy paper 4 sent through the paper feed and conveyance device to a transfer area where a toner image is transferred. A transfer corona discharger is provided in the transfer area and performs corona discharge of the same polarity to charge the latent image formed on the photoreceptor 1; A peeling device 7 is a guide plate that guides the peeled copy paper 4 to a fixing section. Further, the reference numeral 8 denotes a corona discharger for eliminating electric charge, which is disposed behind the transfer area and facing the photoreceptor 1, and removes the electric charge from the photoreceptor.

In the apparatus configured as described above, the toner image 2 formed on the photoconductor 1 rotating in the direction of the arrow is transferred to the copy paper that is conveyed at the same speed as the surface of the photoconductor 1 via paper guides 3a and 3b. 4 is electrostatically transferred by a transfer corona discharger 5. After that, the copy paper 4 is electrostatically adhered to the photoreceptor 1.
is peeled off by the peeling device 6 and the paper guide 7
The image is conveyed to a fixing device (not shown) via the top. On the other hand, after the transfer process, the photoreceptor 1 is moved to the region of the corona discharger 8 for static electricity removal, and the photoreceptor 1 is neutralized and prepared for the next image formation.

The paper guides 3 and 7 are not attached directly to the frame (grounding part) 9 of the main body of the copying machine, but are attached via an insulating resin. The state is shown in FIG. In the figure, the upper and lower paper guides 3a and 3b are the frame 9 of the copying machine main body.
It is held by an insulating support member 10 fixed to the (grounding part) with screws or the like. Therefore, the paper guides 3a and 3b are held electrically floating above the ground portion. Paper guide 7 after peeling
Similarly to the paper guide 3, the edge is separated from the grounding part. The paper guides 3 and 7 are connected in common, as shown in FIG.

The changeover switch 11 changes its contact position according to the humidity, and the ON side is open and the OFF side is open.
side is grounded. This changeover switch 11 is
It can be switched to the ON side in times of high humidity (rainy season) or in humid areas, and to the OFF side in normal humidity.

With the above configuration, the changeover switch 11 can be operated at times of high humidity during the rainy season or in humid areas.
Connect to ON side. As a result, the paper guides 3a, 3b, and 7 are insulated and separated from the ground portion. Therefore, it is possible to prevent a phenomenon in which corona discharge charges acting from the back side of the copying machine 4 flow to the grounding portion 12 via the paper guides 3a, 3b, and 7, and to perform good transfer.

In particular, since both paper guides 3 and 7 are insulated or grounded, it is possible to reliably prevent charged charges from escaping during the action of corona discharge, resulting in greater stability compared to, for example, paper guide 3 alone. .

At times of normal humidity or in regions other than those mentioned above, by connecting the changeover switch 11 to the OFF side, the potential difference between the copy paper 4 or paper guides 3a, 3b, and 7 and the grounding part 12 is sufficient to generate a discharge. Therefore, malfunctions due to noise in each control device in the copying machine are prevented.

Moreover, although the changeover switch 11 of the present invention is illustrated as having a configuration in which the switch is manually switched according to each humidity, it may be configured to switch automatically.

That is, a humidity sensor is provided, the output from this humidity sensor is compared with a reference value at humidity, and the changeover switch 11 is set based on the comparison output.
If you switch each contact point. For example, if the comparison indicates that the humidity is higher than the reference value, each changeover switch 11 is turned to the ON side.

<Effects> According to the toner image transfer device of the present invention, the first paper guide before transfer and the second paper guide after transfer are insulated or short-circuited with respect to the grounding part under the same conditions. Even if the leading edge of the copy paper is guided from the first paper guide to the second paper guide after transfer, the same state can be maintained on both paper guide sides, so in high humidity, corona discharge charge can be transferred through the leading edge of the copy paper after transfer. This prevents the paper from flowing to the ground portion via both paper guides, allowing for good transfer.

In addition, even in normal humidity conditions, good transfer can be performed as described above, and there is no potential difference that would cause a discharge between the copy paper or both paper guides and the grounded part, so noise from each control device in the copy machine Malfunctions due to this are prevented.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a transfer area of an electrophotographic copying machine according to the present invention, and FIG. 2 is a cross-sectional view showing an example of how a paper guide for copy paper is attached in the transfer area according to the present invention. 1; Photoreceptor, 2; Toner image, 4; Copy paper, 5;
Corona discharger for transfer, 3, 7; paper guide,
12; Grounding part, 11; Selector switch.

Claims (1)

[Scope of Claims] 1. A first electrically conductive paper guide that guides a copying paper to a transfer area where a toner image formed on a photoreceptor is transferred and is held in an insulated and separated state from the copying machine main body; A corona discharge device performs corona discharge from the back side of the paper to electrostatically transfer the toner image onto the copy paper, and the copy paper, which has been peeled off from the photoreceptor after transfer, is guided to the fixing section and is insulated and separated from the copy machine body. The second conductive paper guide held in the state is electrically connected to the first and second conductive paper guides, and both paper guides are connected to the main body of the copying machine when the humidity is high. A toner image transfer device that performs stable transfer regardless of humidity, comprising: a changeover switch that maintains an insulated separation state from a grounding section of the copying machine body and electrically connected to a grounding section of the copying machine body at normal humidity;