JPH0117585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transfer/separation device for an electrophotographic copying machine.

A transfer-type electrophotographic copying machine applies a transfer electric field to attract the toner adsorbed to the electrostatic latent image formed on the photoreceptor to the copy paper side, and performs the transfer. Copy paper sticks to the photoconductor. A separating device separates the copy paper from the photoreceptor, and in order to electrostatically apply the force for this separation, an electric charge is injected into the copy paper during transfer, and the copy paper is made into a conductor after transfer. It has been proposed to utilize the electrostatic attractive force between the charges and the induced charges generated in the conductor by bringing the charges close to each other.

FIG. 1 shows the principle of the transfer/separation device, which is the object of the present invention. Reference numeral 1 denotes a photoreceptor, which rotates in the direction of arrow A. The photoreceptor 1 carries an electrostatic latent image 2 of negative polarity, to which toner 3 of positive polarity is adsorbed. Copy paper 4, which is fed toward the circumferential surface of photoreceptor 1 as shown by arrow B, is injected with a negative charge by corona discharger 5 to which DC voltage is applied. As a result, the toner 3 is attracted to the copy paper 4 and transferred. The copy paper 4 that has been transferred is attracted to the circumferential surface of the photoreceptor 1 and advances to a position where the conductive belt 6 is installed. The conductive belt 6 is running as shown by arrow C. Copy paper 4 is placed on the conductive belt 6.
Electrostatic induction occurs due to the negative charge inside the copy paper 4.
A positive charge is induced in the part facing the . And, due to the electrostatic attraction force that acts between these two charges,
The copy paper 4 is attracted to the conductive belt 6 and separated.

By the way, if the conductive belt 6 is grounded,
Since the negative charges paired with the positive charges generated by the electrostatic induction escape to the ground, only the positive charges that attract the negatively charged copy paper 4 remain on the conductive belt 6, and a strong attraction force is generated. . As a result, the separation performance is sufficient, but on the other hand, the positively charged toner 3 is repelled by the positive charges of the conductive belt 6,
In addition, as a result of being attracted to the negatively charged electrostatic latent image 2 on the photoreceptor 1, the developed image once transferred to the copy paper 4 is retransferred to the photoreceptor 1 side upon separation.

The present invention is aimed at solving the above-mentioned problem, and at the time of starting separation, the conductive conveying member is positioned at a first position close to or close to the photoreceptor, but after the separation is started, By switching to a second position further away from the photoreceptor than the first position, re-transfer of toner to the photoreceptor is prevented and transfer performance is improved.

Next, the present invention will be explained with reference to embodiments shown in FIG. 2 and subsequent figures.

Photoreceptor 1 rotates in the direction of arrow A, and copy paper 4 fed in as shown by arrow B is charged by a corona discharger 5, thereby performing transfer. The grounded conductive belt 6 is passed around pulleys 7a and 7b and runs in the direction of arrow C, but the pulley 7a is elastically pressed toward the photoreceptor 1.

Spacers 8a and 8b are attached to both ends of the circumferential surface of the photoreceptor 1, as shown in FIG. a roller 10a attached to the shaft 9 of the pulley 7a;
10b rolls on spacers 8a and 8b.
A gap G is formed between the conductive belt 6 and the circumferential surface of the photoreceptor 1 due to the contact of the rollers 10a and 10b with the spacers 8a and 8b. This gap G corresponds to the copy paper 4 adsorbed on the photoreceptor 1.
A gap of about 0.3 mm is left between the conductive belt 6 and the conductive belt 6. The spacers 8a and 8b are connected to the photoreceptor 1.
Rather than being provided around the entire circumference of the
As shown in the figure, the spacers 8a and 8b are provided corresponding to the image areas D ₁ and D ₂ , and the spacers 8 a and 8 b have cuts corresponding to the cuts E ₁ and E ₂ . Cuts between spacers 8a and 8b and image area
The positions of D ₁ and D ₂ are slightly shifted from the cuts E ₁ and E ₂ , and the cuts E ₁ and E ₂ are in front. The leading portions b ₁ and b ₂ are suitably 15 mm or less.

The copy paper 4 is fed into the image areas D ₁ and D ₂ synchronously, and after being transferred, the copy paper 4 is attracted to the circumferential surface of the photoreceptor 1 and moves toward the pulley 7a. When the leading edge of the copy paper 4 reaches the position of the pulley 7a, the rollers 10a and 10b have fallen into the gaps between the spacers 8a and 8b, and the conductive belt 6 moves the copy paper on the circumferential surface of the photoreceptor 1. Close to 4. As a result, the leading edge of the copy paper 4 is strongly attracted to the conductive belt 6, separated from the photoreceptor 1, and adsorbed to the conductive belt 6, thereby being conveyed in the direction of arrow C.

Due to the rotation of the photoreceptor 1, the rollers 10a, 10
When b passes through the area l ₁ and rides on the spacers 8a ₁ and 8b ₁ , the pulley 7a moves onto the spacers 8a 1 and 8b ₁ .
Depending on the thickness of 8b ₁ , it is separated from the circumferential surface of the photoreceptor 1,
A gap G is created between the conductive belt 6 and the circumferential surface of the photoreceptor 1. When this gap G occurs, the leading edge of the copy paper 4 is strongly attracted to the conductive belt 6 and has already been separated from the photoreceptor 1, so that the copy paper 4 continues to be conveyed. When the copy paper 4 reaches the position of the pulley 7a, there is a gap of about 0.3 mm between the copy paper 4 and the conductive belt 6. There is less reception at the tip than at the tip. As a result, although toner is retransferred to the photoreceptor 1 side at the leading end, retransfer does not occur at the subsequent portions. Further, in the area after the leading edge, a gap occurs between the conductive belt 6 and the copy paper 4 on the circumferential surface of the photoreceptor 1, resulting in a decrease in separation force. Since the particles are attracted to the conductive belt 6 and transported, separation can be continued sufficiently even with a reduced separation force. Cuts E ₁ and E ₂ between image areas D ₁ and D ₂
In the preceding portions l ₁ and l ₂ of the spacers 8a and 8b, that is, the leading edge of the copy paper 4,
The occurrence of retransfer causes white spots, but these can be used for binding margins and do not cause any practical problems.

In the above embodiment, spacers 8a, which have cuts on both edges of the circumferential surface of the photoreceptor 1, are used as means for bringing the conductive conveying member into contact with and separating from the photoreceptor.
8b was installed, but as a means of contact and separation, this is
It will not be tied down. For example, the position of the conductive conveyance member may be moved by a plunger or the like in synchronization with the copy cycle. This method must be used in the case of a type in which the image area on the photoreceptor is not fixed.

In addition to the belt, as a conductive conveyance section,
A roller can also be used, and in addition to directly grounding it and keeping it at zero potential, it is also effective when keeping it at a certain level of potential.

As described above, the present invention allows toner to be attracted to an electrostatic latent image formed on a photoreceptor, and the resulting toner image is transferred to copy paper at a transfer section under the application of a transfer electric field. Then, by applying an electrostatic attraction force between the copy paper and the conductive conveying member,
In a transfer/separation device of an electrophotographic copying machine that separates the copy paper from the photoreceptor, the conveyance member is positioned at a first position close to or close to the photoreceptor at the time of starting separation; Later, the conveying member was switched to a second position that was further separated from the photoreceptor than the first position.
Sufficient transfer performance can be obtained, and both transfer and separation performance can be achieved.

[Brief explanation of drawings]

FIG. 1 is a front view showing the principle of a transfer/separation device, FIG. 2 is a front view of an embodiment of the present invention, and FIG. 3 is a side view of the same. 1... Photoreceptor, 4... Copy paper, 5... Corona discharger, 6... Conductive belt, 7a... Pulley, 8a, 8b... Spacer, 10a, 10b
……roller.

Claims (1)

[Claims] 1. Toner is attracted to the electrostatic latent image formed on the photoconductor, and the resulting toner image is transferred to copy paper in a transfer section under the application of a transfer electric field, and then the copy paper and conductive In a transfer/separation device of an electrophotographic copying machine that separates the copy paper from the photoreceptor by applying an electrostatic attraction force between the transport members, the transport member approaches the photoreceptor when starting separation. Alternatively, a transfer/separation device for an electrophotographic copying machine is located at a first position close to the photoreceptor, and after the separation is started, the conveying member is switched to a second position further separated from the photoreceptor than the first position. .