JPH02167585A - Toner image transfer device - Google Patents

Abstract

PURPOSE:To enable the excellent transfer of a toner image irrelevantly to humidity by isolating and separating or short-circuiting 1st and 2nd paper guides from or to an earthing part according to the humidity. CONSTITUTION:The 1st and 2nd paper guides 3 and 7 are connected in common and grounded to the earthing part 12 through a changeover switch 11. The contact point of the changeover switch 11 is switched according to the humidity and the changeover switch 11 is placed on the ON side at high humidity or in a high-humidity area to isolate and separate the paper guides 3a and 3b, and 7 from the earthing part. Therefore, corona discharge charges which operate from behind a copying machine 4 are prevented from flowing to the earthing part 12. At normal humidity or in a normal humidity area, the changeover switch 11 is connected to the OFF side and consequently a potential difference which is large enough to cause discharge between copying paper 4 or the paper guides 3a and 3b, and 7, and the earthing part 12. Consequently, the toner image transfer device which can transfer the toner image excellently without being affected by the humidity is obtained.

Description

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

<Prior art> Generally, in a transfer type electrophotographic copying machine, charging, exposure,
After each copying step of development, the toner image formed on the photoreceptor is electrostatically transferred onto copy paper by a corona discharge device. 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 activated, 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 member (metal), and the copy paper is conveyed while being in contact with 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, A situation occurred in which the 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, and the resulting copy is a defective image with partial or total 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 copy paper to a transfer area and a second paper guide that guides copy paper that has been peeled off from a 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 switches both paper guides according to humidity conditions. It is characterized by insulation separation from the grounding part or direct short circuit 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 ground portion of the copying machine main body by a changeover 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 by the electrical charges on the copy paper can be transferred satisfactorily.

<Embodiment> 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 numerals 3 denote upper and lower paper guides 3a that guide the copy paper 4 sent through the paper feed and conveyance device to a transfer area where a toner image is transferred.
, 3b. Reference numeral 5 indicates a transfer corona discharger which is provided in the transfer area and performs a corona discharge of the same polarity to charge the latent image formed on the photoreceptor 1;
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 photoreceptor 1 rotating in the direction of the arrow is transferred to the paper guide 3.
The image is electrostatically transferred by a transfer corona discharger 5 onto a copying paper 4'' which is conveyed at the same speed as the surface of the photoreceptor 1 via between a and 3b. Thereafter, the copy paper 4 electrostatically adhered to the photoreceptor 1 is peeled off by a peeling device 6 and conveyed via a paper guide 7 to a fixing device (not shown).

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, upper and lower paper guides 3a and 3b are held by an insulating support member 10 fixed to a frame 9 (grounding part) of the main body of the copying machine with screws or the like. Therefore, the paper guides 3a and 3b are held electrically floating above the ground portion. Similarly to the paper guide 3, the paper guide 7 after peeling is also insulated and separated from the ground portion. The paper guides 3 and 7 are connected in common, as shown in FIG. 1, and connected to a grounding section 12 (for example, the main body frame 9) via a changeover switch 11.

The changeover switch II has its contact position changed according to the humidity, and the ON side is open and the OFF side is grounded. This changeover switch 11 is used during high humidity (rainy season).
Alternatively, it can be switched to the ON side in humid areas and to the OFF side when the humidity is normal.

With the above configuration, the changeover switch 11 is connected to the ON side during high humidity during the rainy season or in a humid region, for example. As a result, the paper guides 3a, 3b and 7
is isolated from the ground part.

Therefore, it is possible to prevent the corona discharge charge acting from the back surface of the copying machine 4 from flowing to the ground 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 an electric 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 it is manually switched in accordance with each humidity, it may be configured in such a manner that it is automatically switched.

That is, a humidity sensor is provided, the output from the humidity sensor is compared with a reference value at humidity, and each contact of the changeover switch 11 is switched based on the comparison output. For example, if the comparison shows that the humidity is higher than the reference value, each changeover switch (1) is turned to the ON side.

<Effects> According to the toner image transfer device of the present invention, the first paper guide that guides the copy paper to the transfer area by corona discharge and the second paper guide that guides the copy paper after peeling are provided on the ground portion. On the other hand, since the insulation is separated or short-circuited depending on the humidity, the electric charge generated by the corona discharger on the copy paper does not escape through each paper guide, so that good transfer of the toner image can be performed regardless of the humidity. Can be done.

In particular, copy paper is guided to the first paper guide and then to the second paper guide.
However, compared to a case where only the first paper guide is insulated or grounded, the copy paper is always placed in the same state by the corona discharger, which increases good transfer stability.

[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 copy paper guide is attached in the transfer area according to the present invention. 1: Photoreceptor, 2: Toner image, 4: Copy paper, 5: Transfer corona discharger, 3.7: Paper guide, 12: Grounding section, 11: Changeover switch. Agent: Patent attorney Takeshi Sugiyama (1 other person)

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 insulated and separated from the copying machine main body; A corona discharge device that electrostatically transfers a toner image onto the copy paper by emitting corona discharge from the back side of the copy paper, and a corona discharger that electrostatically transfers the toner image onto the copy paper, and a corona discharge device that guides the copy paper that has been peeled off from the photoreceptor after transfer to the fixing section, and is insulated from the copy machine main body. a second electrically conductive paper guide held in a separated state; and the first and second electrically conductive paper guides.
The paper guide is provided between the paper guide and the grounding part of the copying machine main body, and it maintains the insulated state of both paper guides from the grounding part of the copying machine main body in high humidity, and also keeps the paper guides in an insulated state separated from the ground part of the copying machine main body in normal humidity. A toner image transfer device that performs stable transfer regardless of humidity, and is equipped with a selector switch for electrically connecting to the ground.