JPS627543B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to copying machines, particularly electrophotographic copying machines.

As one of the exposure devices of electrophotographic copying machines,
Optical images obtained by one image exposure are guided along first and second optical paths to first and second imaging positions located at different positions in the direction of movement of the photoreceptor, and An arrangement has already been proposed in which the optical images are each formed at a second imaging position. A copying machine equipped with this type of exposure device can obtain two electrostatic latent images of the same image on the photoreceptor with one exposure, and in the case of repeat copying, one electrostatic latent image can be obtained with one exposure. This method has the advantage that the copying time can be shortened compared to a method that obtains an electric latent image. In this case, in a copying machine configured to perform charge removal at the same time as image exposure or a copying machine equipped with first and second chargers corresponding to the first and second image forming positions, the first The electrostatic latent image obtained by irradiating the optical image at the imaging position passes through the second charger immediately after the charging process ends, so the potential of the charger is attenuated especially after the charging process ends. Characteristics matter. However, in general, the shield case of a charger has a substantial width in the direction of movement of the photoreceptor, and the current is passed through a large capacitor in order to perform a wide discharge and to stabilize the power supply voltage. Since the voltage is supplied to the terminal, the attenuation characteristics of the potential, that is, the potential fall is poor. In response to this, a conventional idea has been to increase the distance between the two electrostatic latent images obtained on the photoconductor so that the electrostatic latent image is not affected by potential fluctuations when the charger is turned on and off. It is being However, increasing the distance between the two electrostatic latent images increases the distance between the first imaging position and the second wire connection position, which increases the overall size of the machine. Become. Further, as described above, if the distance between the two electrostatic latent images is large, it is disadvantageous in terms of shortening the copying time.

The present invention has been proposed in view of the above-mentioned points, and it is possible to prevent an electrostatic latent image from being affected by potential fluctuations when a charger is turned on or off without increasing the distance between two electrostatic latent images. The aim is to provide an improved copying machine that does not have

According to the present invention, such an object is achieved by using a photoconductor and a plurality of image forming positions located at different positions in the moving direction of the photoconductor along a plurality of optical paths so that an optical image obtained by one image exposure is formed. and a plurality of chargers arranged adjacent to each of the plurality of image formation positions. This is achieved by a copying machine having a shutter device that is selectively located between the charger and the photoreceptor and electrostatically blocks the charger and the photoreceptor. .

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The attached FIG. 1 is a schematic configuration diagram showing one embodiment of a copying machine according to the present invention.
FIG. 2 is an enlarged vertical cross-sectional view of the main part. The exposure device of the copying machine functions to transmit an image of a document placed on a document table 1 to the outer peripheral surface of a photoreceptor drum 2 as an optical image. The exposure device includes a first plane mirror 3 that moves along the lower part of the original platen 1 at the same speed as a slit light source (not shown in the figure), and a diagonal of the moving speed of the first plane mirror 3. a second plane mirror 4 that moves in the same direction at a speed of 1, a lens 5, a half mirror 6,
Third to fifth plane mirrors 7 fixedly arranged respectively
9.

The first and second plane mirrors 3 and 4 are the first
When moving to the right as seen in the figure, the reflected light of the light irradiated toward the original on the original platen 1 passes through the first plane mirror 3, the second plane mirror 4, and the lens 5, and then passes through the half mirror. 6, the light transmitted through the half mirror 6 passes through the third plane mirror 7 and the fourth plane mirror 8, and then reaches the photosensitive drum 2.
The outer surface of the photoreceptor drum 2, that is, the photoreceptor surface, is guided to the first image forming position of the photoreceptor drum 2 through the first slits 11 of the light shielding plate 10 spaced apart along the outer circumference of the photoreceptor drum 2. It's starting to irradiate. Further, the light reflected by the half mirror 6 passes through the fifth plane mirror 9 and reaches a second imaging position located on the forward side in the rotational direction of the photoreceptor drum 2 from the first imaging position. The photosensitive surface of the photosensitive drum 2 is irradiated through a second slit 12 provided in the light shielding plate 10. In this case, an optical path from the first plane mirror 3 to the first imaging position via the second plane mirror 4, lens 5, half mirror 6, third plane mirror 7, and fourth plane mirror 8 is formed. On the other hand, there is an optical path from the first plane mirror 3 to the second imaging position via the second plane mirror 4, the lens 5, the half mirror 6, and the fifth plane mirror 9. is a second optical path, and the optical path from the first plane mirror 3 to the half mirror 6 is a common optical path.

A first charger 13 is provided around the photoreceptor drum 2 at a position on the lag side in the rotational direction of the photoreceptor drum 2 than the first image formation position, and a first charger 13 is provided at a position on the lag side in the rotational direction of the photoreceptor drum 2 from the first image formation position. A second charger 14 is provided at a position on the lag side of the photoreceptor 2 in the rotational direction. Both of the first and second chargers 13 and 14 include a shield case 15 that opens toward the circumferential surface of the photoreceptor drum 2 and has a substantially U-shaped cross section, and a thin metal wire 16 that is stretched inside the shield case 15.
Contains. The second charger 14, which is the latter one of the two chargers, has a second charger.
As clearly shown in FIG. 2, an electrically insulating shutter element 17 is provided selectively between the photosensitive drum 2 and the shield case 15 to close the opening of the shield case 15. In this embodiment, the shutter element 17 is constituted by a cylindrical body surrounding the shield case 15, and has two openings 18 on its periphery spaced apart from each other by substantially 180°. The shield case 15 is configured to rotate around the substantial center thereof as a rotation center.
In this case, during the charging process, the shutter element 17 has its opening 18 aligned with the opening of the shield case 15, so that the shutter element 17 can connect the thin metal wire 16 and the photoreceptor drum 2.
On the other hand, once the charging process is completed, the opening of the shield case 15 is closed by turning substantially 90 degrees, and the thin metal wire 16 is connected to the photosensitive wire 16. This is designed to prevent charging from occurring between the body drum 2 and the body drum 2.

Further, a developing device 19 is provided at a position on the forward side of the rotational direction of the photosensitive drum 2 from the second image forming position.
A transfer device 20 and a cleaning device 21 are arranged around the photoreceptor drum 2 at intervals.

Further, in the case of this embodiment, a light-shielding shutter plate 22 is provided in the middle of the second optical path to selectively block the optical path. This shutter plate 22 is provided to prevent stray light or afterglow from the light source from being irradiated from the second imaging position to the photosensitive drum 2 after the exposure is completed, and after the exposure is completed, the shutter plate 22 is provided at the first imaging position. and the second imaging position until the photosensitive drum 2 rotates by an angle corresponding to the circumferential length of the drum.

Next, the operation of the apparatus constructed as described above will be explained. First and second plane mirrors 3, 4
An optical image obtained by one scan, that is, one exposure is simultaneously guided to the first and second imaging positions along the first and second optical paths,
The first and second chargers 1 rotate in synchronization with it.
Images are formed at two different positions in the rotational direction of the photosensitive drum 2, which is charged by the photosensitive drums 3 and 14, respectively. When the above-described charging-exposure process is completed, the electrostatic latent image obtained at the first imaging position among the electrostatic latent images on the photoreceptor drum 2 that is still rotating is transferred to the second charger 14. At this time, the opening of the shield case 15 of the charger 14 is closed by the shutter element 17, and the charger and the photoreceptor drum are electrostatically isolated. Therefore, there is no possibility that the electrostatic latent image will be disturbed when passing through the second charger 14.

Further, after passing through the second charger 14, this electrostatic latent image passes through a second imaging position, but at this time, the second optical path is blocked by the shutter plate 22. There is no afterglow or stray light from the light source, and the charged potential at that portion does not attenuate on the way to the developing device 19.

The two electrostatic latent images formed on the photoreceptor drum 2 are made visible by the developing device 19 as the photoreceptor drum 2 rotates, and the visible images are transferred between the photoreceptor drum 2 and the transfer device. The image is transferred to the copy paper supplied between the photo frame 20 and the photo frame 20, resulting in a so-called copy image.

From the above explanation, according to the copying machine of the present invention, since the charger is selectively shielded from the photoreceptor drum by the shutter element, the electrostatic latent image on the photoreceptor drum is removed immediately after the charging process is completed. It will be appreciated that upon passing through the charger, the electrostatic latent image is not affected by residual charge in the charger.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of a copying machine according to the present invention, and FIG. 2 is a schematic vertical sectional view showing an enlarged main part of the copying machine. DESCRIPTION OF SYMBOLS 1... Document table, 2... Photosensitive drum, 3... First plane mirror, 4... Second plane mirror, 5...
... Lens, 6 ... Half mirror, 7 ... Third plane mirror, 8 ... Fourth plane mirror, 9 ... Fifth plane mirror, 10 ... Light shielding plate, 11 ... First slit, 12... Second slit, 13... First charger, 14... Second charger, 15... Shield case, 16... Metal thin wire, 17... Shutter element, 18... Opening, 19 ...developing device,
20...Transfer device, 21...Cleaning device,
22...Shutter board.

Claims (1)

[Claims] 1. Guide a photoconductor and an optical image obtained by one image exposure along a plurality of optical paths to a plurality of imaging positions located at mutually different positions in the direction of movement of the photoconductor; A copying machine including an exposure device configured to form the optical image at each of the plurality of image forming positions, and a plurality of chargers disposed adjacent to each of the plurality of image forming positions. A copying machine characterized in that at least a later charger has a shutter device that electrostatically isolates the charger from the photoreceptor.