JPS60669B2 - Surface potential adjustment device for photoreceptor in electronic copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface potential adjustment device for a photoreceptor in an electronic copying machine.

A photoreceptor having a layer made of zinc oxide or some organic photoconductor exhibits a light attenuation characteristic in which the surface potential decreases only slightly within a range where the exposure amount is small, as shown in FIG.

When the photoreceptor has a light attenuation characteristic as shown by curve A, the initial light amount la has little effect on potential attenuation. Therefore, if the amount of light la is applied to the photoreceptor before exposing the image, there is an advantage that the exposure time of the image can be shortened and an image with high contrast can be obtained. However, in a transfer type electronic copying machine, since the photoreceptor is used repeatedly, the light attenuation characteristic changes from that shown by curve A to that shown by curve B. Also, due to variations in the manufacturing of the photoreceptor, for example, the light attenuation characteristic changes. Since it is inevitable that a photoreceptor having a curve A and a photoreceptor having a light attenuation characteristic shown by a curve B will be manufactured, each photoreceptor has a light amount la.
, the surface potentials of the photoreceptor before image exposure are different, such as Va and Vb.

Therefore, in order to keep the surface potential of the photoreceptor constant before image exposure, the amount of light is l
It is necessary to change the amount of light to be applied before exposing the image depending on the initial surface potential of the photoreceptor, such as giving lb to a photoreceptor whose light attenuation characteristic is shown by curve B. The purpose of the present invention is to prevent changes in the light attenuation characteristics of a photoreceptor due to repeated use, or when the light attenuation characteristics of a photoreceptor set in a copying machine are different from those of the previous one. An object of the present invention is to provide a surface potential adjustment device for a photoreceptor that keeps the potential substantially constant.

The photoconductor surface potential adjustment device of the present invention detects the surface potential of the photoconductor and adjusts the amount of light according to the detected potential even if the light attenuation characteristics change. Even if the light attenuation characteristics of the photoreceptor change when the photoreceptor is irradiated after being set in a ready-to-read state, the surface potential before and before the start of exposure is kept constant before and after the change, and the deterioration of gradation before and after the change is prevented. It is characterized by deterrence.

Apparatus for carrying out the method of the invention is shown in FIGS. 2-4.

These are explained below. In FIG. 2, numeral 1 is
A drum-shaped photoreceptor 1 is shown having a light attenuation characteristic in which the potential decreases only slightly within a range where the amount of exposure is small, and this photoreceptor 1 is rotated in the direction of arrow a. A charging device 2, a surface potential adjustment device 3, and an exposure device 4 are installed near the photoreceptor 1.
In addition, a developing device, a transfer device, and a cleaning device (not shown) are provided at necessary positions. After the photoreceptor 1 is charged by a charging device 2, a light amount is applied by a surface potential adjustment device 3, and then an image is exposed by an exposure device 4. The surface potential adjusting device 3 includes a lamp 3a serving as a light amount setting member and having a constant amount of light emitted, slit forming plates 3b and 3c disposed between the lamp 3a and the photoreceptor 1, and the slit forming plates 3b and 3c. and a light-shielding plate 3d, 3e disposed between the light-shielding plate 3d, 3e and the photoconductor 1; A barrel transparent electrode 3f and a photoreceptor 1 connected to this transparent electrode 3f.
an amplifier 3g that outputs a current with a strength corresponding to the amount of charge induced on the transparent electrode 3f by the surface charge (that is, according to the absolute value of the surface potential of the photoreceptor 1), and this amplifier 3g.
When the absolute value of the surface potential of the photoreceptor 1 is large, the slit width is increased and the photoreceptor 1 is
means 3h for moving the slit forming plate 3b so that the slit width becomes smaller when the absolute value of the surface potential of is small. Further, the output of the amplifier 3g is applied to the lamp 3a to increase the amount of light emitted from the lamp 3a when the absolute value of the surface potential of the photoreceptor 1 is large, and when the absolute value of the surface potential of the photoreceptor 1 is small, Alternatively, the amount of light emitted from the lamp 3a may be reduced and the slit width may be kept constant. Moreover, a lattice-shaped opaque electrode may be used instead of the transparent electrode 3f. FIG. 3 shows a sheet-like photoreceptor having a light attenuation characteristic in which the potential decreases only slightly within a range where the amount of exposure is small, and this photoreceptor 5 is moved in the direction of arrow b.

A charging device 2, a surface potential adjustment device 6, and an exposure device 4 are provided near the movement path of the photoreceptor 5, as well as a developing device, a fixing device (not shown), and the like. There is. The surface potential adjustment device 6 includes opaque electrodes 6a, 6 disposed near the photoreceptor 5 at a constant interval.
b, a slit width changing plate 6c which is rotatably provided on the opaque electrode 6a and is made of a conductor with a small mass and is made of aluminum foil, for example, and a conductor between the slit width changing plate 6c and the opaque electrode 6b. From the slit to the photoreceptor 5
a lamp 6d that emits light at a constant amount and a light shielding plate 6e disposed between the lamp 6d and the photoreceptor 5;
, 6f. When the photoreceptor 5 is negatively charged as shown, positive charges are generated in the portions of the opaque electrodes 6a and 6b near the photoreceptor 5, so that the slit width changing plate 6c The portion of the opaque electrode 6b that is far from the photoreceptor 5 is negatively charged, and due to the repulsion of the charge, the slit width changing plate 6c is separated from the opaque electrode 6b by a certain distance, and the slit width changing plate 6c and the opaque electrode 6b are separated from each other by a certain distance. The interval is large when the absolute value of the surface potential of the photoreceptor 5 is large, and is small when the absolute value of the surface potential of the photoreceptor 5 is small.

The amount of light given to the photoreceptor 5 is adjusted by moving the slit changing plate 6c up and down. In FIG. 4, reference numeral 5 indicates a sheet-like photoreceptor having a light attenuation characteristic in which the potential decreases only slightly within a range where the exposure amount is small, and this photoreceptor 5 is moved in the direction of arrow c.

A charging device 2, a surface potential adjustment device 7, and an exposure device 4 are provided near the movement path of the photoreceptor 5, as well as a developing device, a fixing device (not shown), and the like. There is. The surface potential adjustment device 7 includes a lamp 7a that emits a constant amount of light, a transparent electrode 7b installed near a portion of the photoreceptor 5 that is irradiated with light from the lamp, and a conductive wire between the transparent electrode 7b and the lamp 7a. A capacitor 7f is composed of an electrode 7d connected by a wire 7c and a grounded electrode 7e, and the amount of charge charged varies depending on the amount of charge induced in the transparent electrode 7d, and the electrodes 7d, 7 of this capacitor 7f.
A part is inserted between the lamp 7a and the transparent electrode 7b, and the other end is heated in the direction of the arrow d by a spring 7g, and a slit 7h is formed in the same part.
It is composed of a slit width changing plate 7i which is a light amount setting member and a fixed slit forming plate 7j disposed between the slit width changing plate 7i and the lamp 7a. The slit width changing plate 7i is made of a resin having a high dielectric constant, and the slit width changing plate 7i is pulled in the direction of the arrow e by the action of the electric charge stored in the capacitor 7f. For example, when the photoreceptor 5 is negatively charged, the transparent electrode 7b is charged with a positive charge, and the electrodes 7d and 7e of the capacitor 7f are charged with a negative charge and a positive charge, respectively. The amount of charge charged in the capacitor 7f is large when the absolute value of the surface potential of the photoreceptor 5 is large, and is small when the absolute value of the surface potential of the photoreceptor 5 is small. The force for pulling the slit width changing plate 7i in the direction of the arrow e is strong when the amount of charge charged in the capacitor 7f is large, and weak when the amount of charge charged in the capacitor 7f is small. Therefore, the photoreceptor 5
When the absolute value of the surface potential of the photoreceptor 5 is large, the slit width is large, and when the absolute value of the surface potential of the photoreceptor 5 is small, the slit width is reduced by 4 mm, thereby adjusting the amount of light given to the photoreceptor 5. . According to the present invention, even if the light attenuation characteristics of the photoreceptors change, when photoreceptors having different light attenuation characteristics are used, the change in potential in the light attenuation characteristics is detected, regardless of the change. In response to this detection, the light intensity can be set to keep the surface potential level constant before the start of exposure.
It is possible to prevent a decrease in contrast that would occur when the light attenuation characteristics change, and to obtain a high-contrast image.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the light attenuation characteristics of a photoreceptor used in the apparatus of the present invention, and FIGS. 2 to 4 are layout diagrams showing embodiments of the present invention. 1, 5... Photoreceptor, 2... Charging device, 3, 6, 7... Surface potential adjustment device, 4... exposure device. Complete 1 drawing remaining, 2 drawings remaining, almost 5 drawings remaining, 4 drawings remaining

Claims (1)

[Claims] 1. After a photoconductor, which has a photoconductive coating formed on a conductive support and whose light attenuation characteristics change due to repeated use, is charged by a charging device, an electrostatic latent image is formed on the photoconductor by an image exposure device. In the electronic copying machine, an electrode member is arranged between the charging device and the image exposure device to detect the surface potential of the photoreceptor, and an output is controlled according to the amount of charge induced in the electrode member. It is equipped with an amplifier that changes the size and a light amount setting member that increases or decreases the amount of light to the photoreceptor based on the output from the amplifier, and the light amount setting member adjusts the amount of light to the photoreceptor according to changes in the potential level of the light attenuation characteristic of the photoreceptor. A photoreceptor potential adjustment device characterized by controlling the amount of light to the body.