JPS63133165A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce the unevenness of surface potential in a developing position by selecting the position, where the surface potential of a photosensitive body is measured, as the developing position. CONSTITUTION:The length of a developing device 5 in a housing 7 is shorter than that of a photosensitive drum 1, and the deep end side of the photosensitive drum 1 does not face the developing device 5. Consequently, the part which faces the developing device 5 in the lengthwise direction from the front side of the photosensitive drum 1 is used as the image forming area, and the part which does not face the developing device 5 in the deep side of the photosensitive drum 1 is used as a non-image area A. A potential measure 6 facing the photosensitive drum 1 is arranged in the deep end side of the housing 7. For example, a potentiometer probe is used as the potential measurer 6 and is arranged on the extension of a developing sleeve 51 in the developing device. Thus, the surface potential is accurately and stably controlled in the developing position.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus having an electrophotographic process such as an electrophotographic copying machine, a laser beam printer, etc., and particularly an image forming apparatus having a surface potential control function of a photoreceptor. related to things.

(Prior Art) Conventionally, in this type of image forming apparatus, for example, a charging means, an exposing means, and a developing means are sequentially arranged around a photoreceptor along the rotational direction of the photoreceptor, and the surface of the photoreceptor is After being uniformly charged by a charging means, an exposure means performs image exposure to form an electrostatic latent image on the photoreceptor, and a developing means makes the electrostatic latent image visible.

In order to prevent density variations in the developed image due to variations in the surface potential of the photoreceptor, the surface potential of the photoreceptor is measured and the amount of charge or exposure is controlled so that the surface potential becomes a predetermined value. Ta. The surface potential of this photoreceptor was measured in the area between the exposure position and the developing device.

(Problem to be Solved by the Invention) However, in the case of such a conventional example, since the surface potential of the photoreceptor was measured between the image exposure position and the developing unit, the surface potential of the photoreceptor varied from the measurement position. There is a problem in that the actual surface potential at the developing position is different from the measured value because the surface potential attenuates in a short period of time before reaching the developing position, making control of the surface potential unstable. In particular, when the photoreceptor is made of amorphous silicon, selenium, or the like, the surface potential attenuates quickly, resulting in a large difference between the surface potential at the measurement position and the surface potential at the development position.

The present invention has been made to solve the problems of the prior art described above, and its purpose is to provide an image forming apparatus that can reduce variations in surface potential at the development position of a photoreceptor, thereby improving image quality. The aim is to increase

(Means for Solving the Problems) In order to achieve the above object, the present invention sequentially performs a charging process, an exposure process, and a developing process to form an electrostatic latent image and a visible image on a photoreceptor. In addition, in an image forming apparatus that measures the surface potential on the photoreceptor and controls the surface potential of the photoreceptor based on the result, the position where the surface potential of the photoreceptor is measured is set as the development position.

(Function) The surface potential of the photoreceptor is measured and controlled at the development position. Therefore, the density of the image visualized in the developing step is maintained at a predetermined density.

(Example) The present invention will be explained below based on the illustrated example. 1st
The figure is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. In the figure, reference numeral 1 denotes a photoreceptor drum, which is rotatable in the direction of the arrow. After this photosensitive drum 1 is uniformly charged by a charger 2 (
charging process), the original placed on the original platen 4 (not shown)
The image light obtained by illuminating with the exposure lamp 3 is exposed (exposure step) to form an electrostatic latent image.

Furthermore, the electrostatic latent image on the photoreceptor drum l is developed as a toner image by the developing device 5 (developing process), and the developed image is transferred onto a transfer material (not shown), fixed, and discharged outside the machine. Ru.

Here, a potential measuring device 6 for measuring the surface potential of the photoreceptor drum 1 is disposed on an extension line of the developing sleeve 51 of the developing device 5, and is arranged to measure the surface potential at the developing position of the electrostatic latent image. It has become.

FIG. 2 shows a kit in which the photosensitive drum 1 and the developing device 5 are integrated into a housing 7. As shown in FIG. The upper part of the photoreceptor drum 1 is covered by a housing 7 to prevent light from entering from other than an image light entrance groove 7a formed in the housing 7, and the lower part not covered by the housing 7 is covered with an image light entrance groove 7a formed in the housing 7. It is designed so that it does not receive light when installed in a forming unit. A developing sleeve 51 is provided inside the developing device 5 in parallel with the photosensitive drum l. The length of the developing device 5 within the housing 7 is shorter than the length of the photosensitive drum 1, and the rear end side of the photosensitive drum 1 does not face the developing device 5. Therefore, the portion facing the developing device 5 along the longitudinal direction from the front side of the photosensitive drum 1 becomes an image forming area, and the portion not facing the developing device 5 on the back side of the photosensitive drum 1 becomes a non-image area A. The above-described potential measuring device 6 is disposed at the rear end of the housing 7, facing the photosensitive drum 1.

For example, an electrometer probe is used as the potential measuring device 6, and is arranged on an extension of the developing sleeve 51 within the developing device 5.

The surface potential of the photosensitive drum 1 is controlled by the measured value measured by the potential measuring device 6.

The surface potential is controlled by controlling the amount of charge or the amount of exposure. In other words, the potential measuring device 6
is connected to a control circuit 8, which controls the amount of discharge in the charger 2 via a high-voltage power supply 9 and the amount of discharge in the exposure lamp 3 via a lighting circuit 10 in accordance with the measured value of the surface potential of the photoreceptor drum l. The surface potential of the photoreceptor drum 1 is controlled by controlling the exposure amount.

As a method of controlling this surface potential, either the method of controlling the potential of the non-exposed area (dark potential) or the method of controlling the potential of the exposed area (bright potential) may be used, or both methods may be used in combination. good. In the case of dark potential control, for example, the photoreceptor drum l is charged with the charger 2 and is not exposed to light, the dark potential of the photoreceptor drum 1 is detected with the potential measuring device 6, and the detected potential is determined in advance. If the potential is not equal to the predetermined value, the control circuit 8 controls the discharge amount of the charger 2 via the high-voltage power supply 9.

In addition, in the case of the bright potential control method, the photoreceptor drum is charged and, for example, a white plate 1 with a predetermined reflectance is placed on the tip of the document table 4.
1 is provided, the exposure lamp 3 irradiates light of a predetermined intensity to expose the photoreceptor drum 1''2, the bright area potential is measured by the electrometer probe 6, and if it is not equal to the predetermined value, the control circuit 8 By adjusting the amount of light from the exposure lamp 3 via the lighting circuit 10, the bright potential is converged to a predetermined potential.

However, the amount of discharge in the dark potential control described above may be controlled by adjusting the grid voltage, and in the bright potential control, for example, in a copying machine using a laser beam, light is emitted to a light source that irradiates a document and a photoreceptor. If the irradiating light source is different, the amount of light of the exposure light source that directly irradiates the photoreceptor may be adjusted.

In the image forming apparatus having configuration 1, the surface potential of the photoreceptor drum 1 at the development position is measured as described above,
If it is not equal to the predetermined value, the control circuit 8 adjusts the discharge amount of the charger 2 via the high-voltage power supply 9 or the exposure amount of the exposure lamp 3 via the lighting circuit 10, so that the surface potential at the development position becomes the predetermined potential. It is converged on. Therefore, the density of the image developed by the developing device 5 is maintained at a predetermined density, and a high-quality image can be stably obtained.

Furthermore, in this embodiment, since the potential measuring device 6 is disposed facing the non-image compensation area A of the photoreceptor drum 1, the surface potential of the photoreceptor drum 1 can be measured and the surface potential can be controlled at all times even during image formation. The image density can be further stabilized.

(Effects of the Invention) The present invention has the above-described structure and operation, and since the surface potential of the photoreceptor is measured and controlled at the development position, the surface potential control at the development position can be performed accurately and This can be done stably, and the effect is that high-quality images can be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a partially broken part of a kit of a developing device and a photosensitive drum showing how the potential measuring device of FIG. 1 is installed. It is a schematic perspective view. Explanation of symbols

Claims (1)

[Claims] A charging process, an exposure process, and a development process are sequentially performed to form an electrostatic latent image and a visible image on the photoconductor, and at the same time, the surface potential on the photoconductor is measured, and the surface potential of the photoconductor is determined based on the results. An image forming apparatus to be controlled, characterized in that a position where the surface potential of the photoreceptor is measured is a developing position.