JPS61250662A - Image forming device - Google Patents

Abstract

PURPOSE:To form a stable image by changing the irradiation position of electrostatic discharging light which is obtained from an exposure lamp on a photosensitive drum according to the quantity of exposure light and holding the surface potential of the photosensitive drum constant. CONSTITUTION:When a density specifying key is operated, a control part 32 varies a voltage supplied to the exposure lamp 12 to vary the quantity of exposure of the exposure lamp 12. Simultaneously, a motor 35 which drives a mirror 25 is operated under the command of a control part 32 to vary the angle of rotation of a mirror 25. Namely, when the voltage of the exposure lamp is high, the distance between an electrostatic charger 15 for charging and the incidence position of discharging light on the photosensitive drum 14 increases and when the voltage of the exposure lamp 12 is low, the charger 15 and incidence position come closer to each other. Consequently, the surface potential of the photosensitive drum 14 is held constant even when the quantity of exposure varies and the picture quality of a copy image is held stable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus applied to, for example, an electronic copying machine, and particularly relates to an improvement of an exposure apparatus thereof.

[Technical Background of the Invention and Problems Therewith] As is well known, copying machines in which an exposure lamp also serves as a static elimination lamp have conventionally had the following drawbacks. That is, if an attempt is made to obtain an appropriate copy image by changing the exposure amount depending on the type of document, the amount of static eliminating light will also change depending on the exposure amount.

In this way, when the amount of static electricity removal light changes, due to the pre-exposure effect,
Because the surface potential of the photoreceptor drum changes, if you try to copy a dark original, such as a newspaper, with a clear image by increasing the exposure, the image will have poor contrast. Ta.

[Object of the Invention] The present invention has been made based on the above-mentioned circumstances, and its object is to provide an apparatus that serves both as an exposure means and a static elimination means, and that uses a relatively simple structure to eliminate images caused by changes in the amount of exposure light. It is an object of the present invention to provide an image forming apparatus that can suppress changes in the surface potential of a carrier and can form stable images.

[Summary of the Invention] This invention maintains the surface potential of the photoreceptor drum constant by changing the irradiation position of the photoreceptor drum with static elimination light taken out from an exposure lamp depending on the amount of exposure light, for example. It is something.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, an original platen 11 made of transparent glass, for example.
is provided with a document cover (not shown). A document is set on the document table 11, and is moved in the directions of arrows a and b when a copy key on an operation panel (not shown) is operated. An exposure lamp 12 that irradiates light onto the document table 11 is provided on the lower surface of the document table 11 . The document table 11 by this exposure lamp 12
The reflected light is guided to a photosensitive drum 14 as an image carrier via a rod lens array 13.

This photosensitive drum 14 is rotated in the direction of arrow C in the figure, and first, the surface is charged with an electric charge by a charging device 15 serving as a charging means, and then the rod lens array 1
The light guided by 3 is exposed. As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum 14, and this electrostatic latent image is transferred to the developing roller 1 in the developing device 16 as a developing means.
7, the toner is applied to form a visible image. On the other hand, paper P as the transfer material
is taken out from a paper feed cassette (not shown) and fed to the transfer section. The paper P fed to the transfer section T is brought into close contact with the surface of the photoreceptor drum 14 at the transfer charger 18, and
The toner image on the photoreceptor drum 14 is transferred by the action of the charger 18 .

The paper P to which this toner image has been transferred is charged by a peeling charger 19
The image is peeled off from the photoreceptor drum 14 and conveyed on the conveyor belt 20, fixed by a pair of fixing rollers (not shown), and then discharged. In addition, the photosensitive drum 14 after the transfer
After the residual toner on the surface is removed by the cleaning blade 22, the afterimage is erased by the discharge light emitted from the exposure lamp 12, and the initial state is restored. Further, the exposure lamp 12 is provided with a reflective member 23, and the reflective member 23 is provided with a through hole 24 through which the static eliminating light is taken out. The extracted static eliminating light is irradiated onto the surface of the photoreceptor drum 14 via a rotatable mirror 25 serving as an adjusting means capable of adjusting the angle of incidence and angle of reflection.

FIG. 2 shows the overall control circuit.

The operation panel 31 is provided with a copy key for specifying a copying operation, a numeric keypad for specifying the number of copies, a density specifying key for specifying an exposure amount, and the like.

The output signal from the operation panel 31 is supplied to the control section 32, and in response to the commands from the control section 32, the motors 33 and 34 that drive the photoreceptor drum 14 and the developing unit 16 are operated, and the exposure lamp 12 and the charging motor 33 and 34 are operated. The charger 15, the transfer charger 18, the peeling charger 19, etc. are operated. Further, when the density designation key is operated, the voltage supplied to the exposure lamp 12 is varied by the control section 32, and the amount of exposure of the exposure lamp 12 is changed.

At the same time, the mirror 2
The motor 35 that drives the mirror 25 is operated, and the power of the motor 35 is transmitted to the mirror 25 via a drive unit 36 made of gears and the like shown in FIG. 1, and the rotation angle of the mirror 25 is changed. That is, when the voltage of the exposure lamp is high, the charging charger 15 and the photoreceptor drum 14- are made to have separate positions of incidence of the neutralizing light, and when the voltage of the exposure lamp 12 is low, the charging charger 15 and the photoreceptor drum 14 are separated from each other. The position of incidence of the static elimination light on the photoreceptor drum 14 is made closer to the photoreceptor drum 14. As shown in FIG. 3, the resistance value of the photosensitive drum changes depending on the intensity of the pre-exposure to the neutralizing light and the distance (recovery time) from the incident position of the neutralizing light to the charging device. That is, in the case of a bright original, the voltage of the exposure lamp is high and the amount of static elimination light is also large. Therefore, as indicated by H in the figure, it takes time for the resistance value to recover to the constant value Th. Therefore, in this case, the distance between the static eliminating position and the charging device is increased so that the recovery time of the apparent resistance value becomes a certain constant value. Furthermore, in the case of a dark original, the voltage of the exposure lamp becomes low.

For this reason, the amount of static eliminating light is reduced, and the recovery time of the resistance value is shortened as shown by D in the figure. Therefore, in this case, the distance between the incident position of the static eliminating light and the charging device is narrowed, and the apparent resistance value is set to a certain constant value over the recovery time.

FIG. 4 shows the relationship between the static elimination illuminance and the surface potential of the photosensitive drum, where A is the conventional one and B is the one according to this embodiment. As is clear from this figure, in this example, the surface potential of the photoreceptor drum does not change much with respect to the change in the static elimination illuminance.

According to the embodiment described above, the rotation angle of the mirror 25 is changed in accordance with the voltage of the exposure lamp 12, and the incident position of the neutralizing light on the photoreceptor drum 14 is changed. Therefore, even if the exposure amount changes, the surface potential of the photoreceptor drum 14 can be kept constant, so it is possible to stably maintain the image quality of the copied image.

In the above embodiment, the voltage of the exposure lamp 12 is changed by operating the density specifying key, but the invention is not limited to this, and the density of the document is automatically detected, and the exposure amount and the mirror 25 are adjusted accordingly. The rotation angle may be changed.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As described in detail above, according to the present invention, in an apparatus that serves both as an exposure means and a static elimination means, a change in the surface potential of an image carrier due to a change in the amount of exposure light can be achieved with a relatively simple configuration. Therefore, it is possible to provide an image forming apparatus that can suppress the image quality and form a stable image.

[Brief explanation of drawings]

The drawings show an embodiment of an image forming apparatus according to the present invention, and FIG. 1 is a schematic configuration diagram showing only the main parts, and FIG.
The figure is a schematic configuration diagram showing the control circuit, and FIGS. 3 and 4 are diagrams shown to explain the operation, respectively. 12... Exposure lamp, 14... Photosensitive drum, 15
... Charging charger, 16... Developing device, 18... Transfer charger, 19... Peeling charger, 25... Mirror, 32... Control unit, 35... Motor,... Static elimination light. Applicant's agent Patent attorney Takehiko Suzue Figure 1■ Figure 3

Claims (3)

[Claims] (1) an image carrier, a charging means for forming an electric charge on the surface of the image carrier, exposing and scanning a document image to form an optical image corresponding to the document image on the charged surface of the image carrier; an exposure means that also serves as a static eliminating means for removing residual charges on the image bearing member; a developing means for developing the image formed on the image bearing member; and a transfer means for transferring the developed image onto a transfer material. An image forming apparatus comprising: an adjusting means for guiding the neutralizing light of the static eliminating means to the image carrier; and an irradiation position of the static eliminating light on the image carrier by driving the adjusting means according to the exposure amount of the exposing means. An image forming apparatus comprising: a control means for changing the image forming apparatus. (2) The image forming apparatus according to claim 1, wherein the exposure means is fixed and the original image is moved. (3) The image forming apparatus according to claim 1, wherein the adjusting means comprises a rotatable mirror.