JPH0455511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic copying machine that maintains good transfer performance regardless of high humidity or low humidity.

<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 area on the photoreceptor to the copy paper by the corona discharge device, which has the same polarity as the charge on the photoreceptor and the charge on the toner particles. Electric charges are charged charges of different polarity that are attracted and transferred onto the 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.

Further, 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 has been 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 the electric charge flowed through the paper guide to the frame (grounding 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, and to efficiently remove charges remaining on a photoreceptor after transfer.

<Means for Solving the Problems> In the electrophotographic copying machine of the present invention, the shield member of the transfer corona discharger is grounded via a resistor when the humidity is high, and when the humidity is not high, the shield member is directly short-circuited to the grounding part. ,
Similar to this corona discharger for transfer, the corona discharger for static elimination is also characterized by a configuration in which the shield member is grounded via a resistor when the humidity is high, and the grounding portion is directly short-circuited when the humidity is not high.

<Function> According to the electrophotographic copying machine of the present invention, when the humidity is high, the shield member of the corona discharger for transfer and static elimination is grounded through insulation or resistance, so that the discharge current flowing to the photoreceptor side increases. Therefore, as the charge applied to the copy paper increases, the charge for neutralizing the photoreceptor also increases.

Therefore, by compensating for the large amount of charge that escapes to the ground through the copy paper and increasing the discharged charges toward the copy paper, the toner image transfer action can be made equivalent to that at normal humidity when the humidity is low. Further, although the charge charged on the photoreceptor at this time also increases, the amount of corona discharge for static elimination also increases in the static elimination corona discharger, and the static elimination after transfer of the photoreceptor can also be effectively performed.

<Example> FIG. 1 is a cross section showing a transfer section in an electrophotographic copying machine according to the present invention. In the figure, 1 is 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 denotes upper and lower paper guides 3a for guiding the copy paper 4 sent through the paper feeding and conveying device to the transfer area where the toner image is transferred.
It is 3b. 5 is a photoreceptor 1 provided in the transfer area.
6 is a transfer corona discharger that performs a corona discharge of the same polarity to charge the latent image formed on the transfer area; 6 is a peeling device that is disposed behind the transfer area and peels the copy paper that is in close contact with the photoreceptor 1 from the photoreceptor; 7 is a peeling device that This is a guide plate that guides the peeled copy paper 4 to the fixing section. Further, reference numeral 8 denotes a corona discharger for neutralizing charges, which is disposed behind the transfer area and facing the photoconductor 1, and eliminates electric charges from the photoconductor.

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 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 area 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, it is also insulated and separated from the ground portion. 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 addition, at times of normal humidity other than those mentioned above, or in regions other than those mentioned above, by connecting the changeover switch 11 to the OFF side, it is possible to generate a discharge between the copy paper 4 or paper guides 3a, 3b, and 7 and the grounding section 12. Since no potential difference occurs, malfunctions due to noise in each control device in the copying machine are prevented.

In the present invention, in particular, the stainless steel shield material 5a of the transfer corona discharger 5 is electrically connected to the grounding part 10 via the changeover switch 13. This switch 13 has an ON side connected to the grounding part 12 through a resistor R (about 1MΩ), and an OFF side connected to the grounding part 12 as it is.
It is connected to 2.

With this configuration, the changeover switch 13 can be turned on in high humidity or in humid areas.
When switched to the side, the shielding material 5a and the grounding part 1
A high resistance R is inserted between 2 and 2. Therefore, the discharge current becomes difficult to flow toward the shield material 5a, while the copy paper 4 passing through the transfer area
In response, it becomes easier to flow to the side. and,
This increase in the discharge current toward the copy paper 4 directly results in an increase in the charge on the copy paper 4, which can compensate for transfer loss due to a decrease in electrical resistance of the copy paper 4 due to high humidity.

In addition, in FIG. 3, the changeover switch 13 is
A resistor R is inserted on the ON side, but this ON
The side may be completely insulated from the ground portion 12. However, since a portion of the photoreceptor 1 that does not overlap with the copy paper 4 is exposed to a large discharge action, the above-described configuration may be used as long as there is no problem of fatigue of the photoreceptor 1 due to long-term use.

Furthermore, in non-humid conditions or in non-humid regions, the electrical resistance of the copy paper 4 is sufficiently high, and if the switch 13 is turned to the ON side in such a state, the electrostatic charge on the copy paper 4 will be reduced during transfer. By increasing, the degree of close contact with the photoreceptor 1 is strengthened,
At the time of peeling, the copy paper 4 is not peeled off smoothly. In addition, since the problem of deterioration of the photoreceptor 1 described above also occurs, the changeover switch 13 is connected to the OFF side.
The shield material 5a and the ground portion 12 are short-circuited. In this way, the copy paper 4 can be easily peeled off at the time of peeling.
The problem of deterioration of the photoreceptor 1 does not occur.

When the shielding material 5a of the transfer corona discharger 5 is insulated from the grounding part 12, the discharge from the corona discharger 5 is applied not only to the copy paper 4 but also to the copy paper on the photoreceptor 1, as described above. It is also strengthened for areas that do not overlap with 4. Therefore, even if normal charge removal is performed, the photoreceptor 1 cannot be sufficiently removed, and the next image formation is adversely affected.

Therefore, as shown in FIG. 1, it is preferable to strengthen the discharge action on the photoreceptor 1 by the static eliminating corona discharger 8 to effectively eliminate static electricity. In the figure, the shielding material 8a of the static elimination corona discharger 8 is connected to the changeover switch 1.
4, and when this switch 14 is turned to the ON side, it is connected to the grounding part 12 via the resistor r,
When it is turned to the OFF side, it is short-circuited to the grounding part 12. As a result, when the switch 14 is turned to the ON side, the static elimination current applied to the photoreceptor 1 increases during static neutralization. Therefore, if the changeover switch 14 is changed in accordance with the changeover of each contact of the changeover switch 11 connected to the shield material 5a of the transfer corona discharger 8,
Good static elimination can be performed.

In FIG. 1, each changeover switch 11, 13,
In order to facilitate the operation of the switches 14, it is convenient if the switches are configured to work together.

Moreover, the changeover switches 11, 13, 14 of the present invention
Although the above example shows a configuration in which the humidity is changed manually according to each humidity, a configuration in which the humidity is changed automatically may also be used.

That is, a humidity sensor is provided, and the output from this humidity sensor is compared with a reference time at a reference humidity, and based on the comparison output, the changeover switch 1 is switched.
It is sufficient to switch each contact point 1, 13, and 14. For example, if the comparative output is higher than the reference humidity, each switch 11, 13, 14 is turned to the ON side.

<Effects> According to the electrophotographic copying machine according to the present invention, the discharge effect of the transfer corona discharger on the copy paper increases in high humidity, and the electric charge discharged through the copy paper can be compensated for, thereby improving the transfer efficiency. Good transfer can be performed without any deterioration, and at the same time, the static eliminating effect can be enhanced and good static neutralization can be performed in eliminating static electricity from the photoreceptor.

In addition, even under normal humidity conditions, the amount of charge discharged through the copy paper is extremely small, so corona discharge to the copy paper is suppressed, resulting in good transfer and charge removal from the photoreceptor. I can do it.

Therefore, in the next image formation, a normal image can always be formed without any adverse effects.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a transfer area of an electrophotographic copying machine according to the present invention, and FIG. 2 is a sectional view showing an example of how a copy paper guide is attached in the transfer area. 1; Photoreceptor, 2; Toner image, 4; Copy paper, 5;
Corona discharger for transfer, 5a; Shield material, 8; Corona discharger for static elimination. 8a; Shielding material; 12; Grounding portion; 13, 14; Selector switch.

Claims (1)

[Scope of Claims] 1. A transfer corona discharger for electrostatically transferring a toner image formed on a photoreceptor onto copy paper, and a corona discharger for removing electric charge remaining on the photoreceptor after the transfer. In an electrophotographic copying machine equipped with a static elimination corona discharger, the shield member constituting the transfer corona discharger is connected to the grounding part of the copying machine body via a resistor, or directly electrically connected to the grounding part. a first switch for electrically connecting the shield member constituting the static elimination corona discharger to the grounding section of the copier main body via a resistor or directly to the grounding section; The above-mentioned first and second switches switch both shield members to the side where they are connected to the grounding part through a resistor when the humidity is high, and continuously switch them to the side where they are directly connected to the grounding part when the humidity is normal. An electrophotographic copying machine.