JPS61212872A - Copying machine - Google Patents

Abstract

PURPOSE:To prevent effectively a transfer slippage due to transportation defect when the electrostatic attraction of a photosensitive body to a recording paper is small by setting the line speed of a transporting roller slightly higher than that of the photosensitive body. CONSTITUTION:The line speed of the transporting roller 13 is slightly higher than that of the sensitizing material 5. The adhesion to the photosensitive body 5 of the popular recording paper P2 of a low firmness becomes better by impressing a transfer voltage 11, and the tip of the recording paper is separated approximately in a part 6 by impressing a separation electrode 12. At such a time, the electrostatic attraction is large because the substantial transfer effective area is long, and a projecting loop absorbs a difference between line speeds, whereby the recording paper can be transported without the transfer slippage. The paper P1 having excellent firmness is separated in a part (a), and transported by being engaged by a slightly high speed roller 13. As a result, the transfer slippage can be prevented irrespective of the rigidity of the recording paper, and clear copying can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transfer-type copying device that ensures the conveyance of recording paper and prevents misalignment of transfer.

[Conventional technology]

Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a light beam image corresponding to a document is irradiated onto the surface of an image carrier uniformly charged by a charging electrode to form an electrostatic latent image, and the latent image is developed. The toner is brought into contact with the toner to be visualized as a toner image, and a recording paper sent from a paper feed section in synchronization with the toner image on the image carrier is guided to the peripheral surface of the image carrier, and the visualized toner image is is transferred onto the recording paper by the action of a transfer electrode applied with high voltage, and then the recording paper is separated from the circumferential surface of the image carrier by the action of a separation electrode etc. applied by a high voltage alternating electrode, and the separated recording paper is The toner image is guided by a conveying member to a heat roller fixer, and the toner image on the recording paper is fixed as a permanent image. After the transfer and separation, the surface of the image carrier is wiped by a cleaning device to complete the next copying step 1.

Nowadays, there is a trend to reduce the diameter of the image carrier in order to make copying machines more compact, but even in the copying machine with the above structure, the area where transfer is effectively performed by the transfer electrode on the image carrier, i.e. The width of the contact between the drum surface and the transfer paper is short.

For example, in a copying machine in which the diameter of the drum of the image bearing member is 100 mm, the contact width between the drum surface and the transfer paper is about 16,111 mm for commonly used recording paper. When the contact width between the drum surface and the transfer paper becomes shorter in this way, the electrostatic adhesion force between the image carrier and the recording paper in the contact area between the drum surface and the transfer paper becomes smaller, and the contact between the recording paper and the transfer paper becomes smaller. It becomes easy to slip on the circumferential surface, and the conveyance force of the recording paper decreases, making feeding errors more likely to occur. Therefore, in order to prevent such feeding defects, some conveyance devices utilize a conveyance suction belt system that uses a conveyance belt and suction together. Although this method can achieve the effect of stably conveying the recording paper to the fixed area of the heat roller after separating the recording paper from the image carrier,
Especially in the case of small-sized recording paper with high rigidity (strong stiffness),
When the trailing edge of the recording paper is conveyed before and after it is separated from the image carrier, only the leading edge of the recording paper touches the suction belt, so the suction force to the recording paper is weak and unstable, resulting in transfer misalignment. There is a problem with this.

[Problem that the invention seeks to solve]

The present invention transfers an image from an image carrier having a curvature to a transfer means (
A transfer type copying device for effectively preventing transfer misalignment due to poor conveyance when the electrostatic attraction force between the image carrier and the recording paper is small when the image is transferred onto a recording paper and the recording paper is further separated by a separating means. The purpose is to provide

[Means for solving problems]

The present invention aims to achieve the second object, in which an image is transferred from an image carrier having a curvature to a recording paper by a transfer means, the recording paper is further separated by a separating means, and a heated roller fixed fixer is used to transfer an image to a recording paper. The present invention provides a copying apparatus which performs fixing, and is characterized in that the line speed of the conveyance roller is set slightly faster than the line speed of the image carrier.

〔Example〕

FIG. 1 shows an embodiment of a transfer type copying apparatus to which the present invention is applied, and is a side sectional view of a copying apparatus of a moving document table type using a one-sided reference copying method and using a converging light transmission element as an optical system.
FIG. 2 is an explanatory view of the main parts showing the mode of transfer and separation between a weak regular recording paper and a small-sized recording paper that is highly rigid and stiff. In the figure, 1 is a document table on which a document is placed, 2 is an exposure lamp for illuminating the surface of the document, 3 is a reflector for efficiently condensing and irradiating the light of the lamp onto the surface of the document, and 4 is a document This is a focusing light transmission element (Selfoc lens) for transferring the image to the image carrier (photosensitive drum) 5. Reference numeral 6 denotes a charging electrode for uniformly charging the surface of the photosensitive drum 5 rotating in the direction of the arrow. An electrostatic latent image corresponding to one document is formed on the circumferential surface of the photosensitive drum 5. The latent image is visualized as a toner image by the developing device 7. On the other hand, the recording paper P is fed by a paper feed roller 8, a registration roller 9, and a feed roller 10 for feeding small-sized recording paper in synchronization with the toner image on the photosensitive drum 5, and is superimposed on the photosensitive drum 5. Transfer electrode 1
After the toner image on the photoreceptor is transferred onto the recording paper P by step 1, it is separated from the photoreceptor drum 5 by the separation electrode 12, and is transported to the left side in the first drawing by the transport roller 13 for transporting the small-sized recording paper. The sheet is further guided to a heat roller fixing device 16 by a generally concave conveying member 14 and an auxiliary conveying roller 15, where it is fixed, and then discharged onto a paper discharge tray 19. After the recording paper has been separated, the photosensitive drum 5 is cleaned of residual toner remaining in the core portion by a cleaning device 17, and then erased by an erasing lamp 18 to erase any residual charge remaining in the core portion in preparation for the next copying cycle. As a result of various experiments in the above configuration, the inventor of the present invention found that the line speed of the conveying roller 13 was slightly increased compared to the line speed of the photosensitive drum 5. It was found that stable copied images could be obtained without paper misalignment at the transfer position. According to this experiment 1, when the line speed of the photosensitive drum 5 is 120 mW/see, the conveyance roller 13
If the line speed of the photosensitive drum 5 is increased by about 0.3% to 120.4 speeds/sec, there will be no transfer deviation at the core even when transferring the small-sized recording paper. Good results were obtained. This is because when copying is performed using ordinary recording paper P2, which has a weak stiffness, by applying the transfer electrode 11 as shown by the broken line in the second figure, the adhesiveness with the photosensitive drum 5 improves due to the weak stiffness, and the effective transfer area is effectively The leading edge of the recording paper is separated from the photosensitive drum 5 at the omitted part as shown in the second figure at the position where the leading edge of the recording paper is separated due to the increased width and the application of the separation electrode 12. After separation, the paper is conveyed through a convex loop as shown by the broken line in the figure. It is held between rollers 13 and conveyed. In this case, since the actual effective transfer area is long, the electrostatic attraction force between the recording paper and the photosensitive drum 5 is large, and the line speed of the conveyance roller 13 and the line speed of the photosensitive drum 5 are increased due to the convex loop after the recording paper is separated. Since the difference in speed can be absorbed by the loop, the loop is absorbed little by little, and the desired copy image can be obtained by being conveyed without causing any transfer deviation. Next 1
When copying is performed using small-sized recording paper with high rigidity and stiffness, the stiffness of the recording paper inevitably makes the effective transfer area small, and the upstream side of the above-mentioned portion as shown by the dashed line in the second figure inevitably becomes smaller. The leading edge of the recording paper is separated at section a, and the recording paper is separated in a substantially straight state as shown by the dashed line P1 in the second figure without forming a convex loop after separation, and the recording paper is separated by the conveyance roller 13.
Proceed to the section. The length between the small-sized recording paper separation position and the conveying roller 13 is configured to be approximately the same as the length of the recording paper in the feeding direction, and the line speed of the conveying roller 13 is set to be equal to the length of the recording paper in the feeding direction. Since the line speed is slightly faster than the line speed of the roller 13, when the recording paper is bitten by the roller 13 section, the recording paper is not pushed and is smoothly bitten, and when it is bitten by the roller 13 section, it is almost At the same time, the transfer is completed and conveyed. In addition, in this example,
Although a transfer type copying apparatus with a movable document table has been exemplified, the present invention is of course applicable to a transfer type copying device with a fixed document table and a movable optical system.

〔Effect of the invention〕

As explained above, the present invention provides a copying machine that transfers an image from an image carrier having a curvature to a recording paper using a transfer means, further separates the recording paper using a separating means, and fixes it using a fixed heat roller fixer. By slightly increasing the line speed of the conveyance roller after transfer and separation compared to the line speed of the image carrier, transfer misalignment is prevented during transfer and separation of not only weak recording paper but also strong small size recording paper. The present invention is very useful because normal and clear copies can always be obtained.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a transfer type copying apparatus to which the present invention is applied, and is a side sectional view of a copying apparatus of a movable document table type using a one-sided reference copying method and using a converging light transmission element as an optical system.
The figure is an explanatory diagram showing the manner of transfer and separation conveyance of a weak regular recording paper and a small-sized recording paper having high rigidity and stiffness. 5... Photosensitive drum 10... Feeding roller 11.
Transfer electrode 12... Separation electrode 13... Conveyance roller 14... Conveyance member 16... Heat roller fixed applicator P... Recording paper

Claims (1)

[Claims] Transferring an image from an image carrier having a curvature to a recording paper by a transfer means, and further separating the recording paper by a separating means,
1. A copying apparatus that performs fixing with a heat roller fixing device, characterized in that the line speed of the conveyance roller is set slightly faster than the line speed of the image carrier.