JPS58149065A - Printer - Google Patents

Abstract

PURPOSE:To maintain the charging potential on a photosensitive drum always constant and to maintain the density of printing images constant accordingly, by changing the voltage to be generated in the photosensitive drum according to the times of use of the photosensitive drum. CONSTITUTION:The voltage of a high-voltage power source 1 is first set at, for example, 6V, and the electrostatic charging potential of a photosensitive drum 3 is set at 1,000V. When the photosensitive drum 3 is going to be used repeatedly, a counter 9 counts the number of revolutions of the drum, and a D/A converter 10 generates the analog voltage corresponding to the count value, in accordance with which voltage the power source 1 is controlled. The electrostatic charging voltage of the drum 3 is thus maintained always at 1,000V. As a result, the output of the printing image in the same density is obtained irrespectively of the number of revolutions of the photosensitive drum.

Description

Detailed Description of the Invention α) Technical Field of the Invention The present invention relates to a printing device, and particularly in an electrophotographic printing device, it is possible to reduce the charged potential of a photoconductor caused by repeated use of the photoconductor. The present invention relates to a printing apparatus that is controlled so as to compensate for the reduction in accordance with the number of times a photoreceptor is used.

(2) Prior art and its problems For example, a data processing device uses an electrophotographic printing device as its output device, and prints a printout or an image output as a result of data processing on paper. In this printing apparatus, as shown in FIG. 1, a high voltage is applied from a high voltage power source 1 to an electrode 2, whereby a photosensitive drum 3 is charged, and an exposure section 4 forms a pattern. The toner supplied from the developing device 5 is attached to this latent image to make it visible, and this visible image is transferred onto the paper α by the transfer charger 6 and fixed by the fixing device F. Then, the photosensitive drum 3 is entirely exposed to light by a charge eliminating lamp 7 to neutralize the charged state, and then the residual toner on the photosensitive drum 3 is collected by a charge removing toner collecting device 8. In the apparatus shown in FIG. 1, if the charging potential of the photosensitive drum 3 changes, the amount of toner adhering to the latent gIK will vary, and as a result, for example, the density of the printed image will not be constant. become. However, since the surface of the photosensitive drum 30 is formed with a photosensitive material made of, for example, selenium and tellurium, as the number of times the photosensitive drum 3 is used increases, charging fatigue, exposure fatigue, etc. are compounded, and its surface characteristics change. If this happens, even if a constant voltage is applied to the photosensitive drum 3, the resulting charged potential will decrease, so the charged potential on the surface of the photosensitive drum will decrease as the number of times the photosensitive drum is used. Become. For example, as shown in FIG. 2, when a constant voltage of 6 KV is applied to the photosensitive drum 3 and the photosensitive drum is used 1000 times, the charged potential of the photosensitive drum, which was initially 1000 V, decreases by 600 VK.

As a result, the adhesion of the toner decreases as the number of times it is used increases, resulting in a problem in that the output density of the printing device becomes lighter.

(3) Purpose of the Invention The purpose of the present invention is to reduce the charging potential of the photosensitive drum in order to improve the problem that the density of the printed image becomes lighter as the number of times the photosensitive drum is used increases. It is an object of the present invention to provide a printing device that compensates according to the number of times the photosensitive drum is used.

(4) Structure of the Invention In order to achieve this object, in the printing apparatus of the present invention, a photoreceptor charged by a charging means is exposed to light to form a latent image, toner is attached to this latent image, and this is applied to a sheet of paper. An electrophotographic printing apparatus for transferring images onto a photoreceptor is equipped with a counting means for counting the number of rotations of a photoreceptor, and a control voltage generating means for generating a control voltage based on the counted value, thereby increasing the output voltage of the charging means. It is characterized by being controlled.

(5) Embodiment of the Invention Before explaining in detail one embodiment of the present invention, the principle of the present invention will be briefly explained based on FIG. 3.

FIG. 3 is a diagram showing the principle of compensating for the decrease in charging potential shown in FIG. 1. As shown in FIG. B3, the charged potential of the photosensitive drum can be maintained at a constant value by increasing the voltage applied to the photosensitive drum as the number of times the photosensitive drum is used increases. From this, if the number of times the photosensitive drum is used is counted and the voltage shown in Figure 3 is applied to the photosensitive drum according to the number of uses, the decrease in the charged potential of the photosensitive drum can be compensated for, and the potential of the photosensitive drum can be reduced. held constant.

Next, one embodiment of the present invention will be described based on FIGS. 3 and 4.

In the figure, the same reference numerals as those in FIG. 1 indicate the same components, and 9 is a counter and IO is a D/A converter.

The counter 9 calculates the number of rotations of the photosensitive drum 3.

The L)/A converter 10 generates a control voltage depending on the count value of the counter 9, and
Based on this control voltage, the generated voltage shown in FIG. 3 is applied from the high voltage power supply 1 to the electrode 2.

Next, the operation of this embodiment shown in FIG. 4 will be explained with reference to FIG. 3.

Initially, the voltage of the high-voltage electricity 6r11 is set to 6KVK, for example, and the charging potential of the photosensitive drum 3 is set to 1000V. In this state, the photosensitive drum 3 is rotated to form a latent image in the exposure section 4, toner is attached from the developing device 5 to the latent image, this toner is transferred to the paper 1, and the residual toner is further removed from the charge and collected by the recovery device 8. Collect the toner. When these series of operations are continued, the counter 9 counts the number of rotations of the photosensitive drum 3 and outputs this counted value to the counter 9 in digital form. The D/A converter lO generates an analog voltage corresponding to this count value trap, and the trap high voltage power supply l is controlled based on this value K so that the voltage shown in FIG. 3 is generated.

As a result, the charged potential of the photosensitive drum 3 is always maintained at K1000v.

As a result, a printed image output with the same density is obtained regardless of the number of rotations of the photosensitive drum.

Next, a second embodiment of the present invention will be explained with reference to FIGS. 5 and 6.

In this embodiment, as shown in FIG. 5, the number of rotations of the photosensitive drum is divided into several levels 11, and if the generated voltage is kept constant within the same level 1, K is set so that the charged potential is kept constant. It is.

In FIG. 6, 11 is a classifier, and 12 is a control voltage generator.

The classifier 11 classifies the count value of the counter 9 into layers based on the count value, and is composed of a microprocessor unit.

The control voltage generating section 12 generates a pressure control voltage so that the generated voltage shown in FIG. 5 is generated from a high voltage power supply, and includes a level setter 12α and a converter 1z.

The level setting device 12g is connected to a power source E, so that the control voltage can be set according to the floor 11 in which the rotation speed of the photosensitive drum is classified.
, E, and a resistor, which allows the voltage value of each level to be selected.

The converter 12 stores the floors llI classified by the classifier 11.
Accordingly, a predetermined control voltage value that generates the voltage shown in FIG. 5, for example, is selected from the level setter 12α.

Next, the operation of this second embodiment will be explained.

First, the charging potential of the photosensitive drum 3 is set to 1oocl', and then the photosensitive drum is rotated. The number of rotations is counted by a counter 9 and the counted value is output to the classifier 11. At this time, the classifier 11 outputs a classification signal for each fixed number of rotations, and in response to this, the converter 12h outputs a large control voltage in the classification category with a low number of rotations, and a small control voltage in the category with a high number of rotations. K to output. Based on this control voltage value, the voltage shown in FIG. 5 is applied to the electrode 2 from the high-voltage power supply l. As a result, a constant charging potential is obtained. The circuit configuration is simplified by classifying the number of rotations of the photosensitive drum into layers and generating voltages according to the classification.

As shown in Figure 2, before using the photosensitive drum,
Since the charging potential rapidly decreases, if the rotational speed is small, the variation in the charging potential can be reduced by dividing the rotation speed into small areas.

For example, θ~1O110~20.20~50.50~10
0,100~200.200~500゜500~100
Classified as 0.1000~.

Furthermore, as shown in FIG. 7, when the rotation of the photosensitive drum 30 is stopped in the configuration shown in FIG. 6, that is, when the count value of the counter 9 does not increase, the classifier 11 detects this and resets the counter 9. You can do it like this. In this way, the charging potential characteristics of the surface of the photosensitive drum 30 are restored when the photosensitive drum 30 is not used, so that the charging potential can be prevented from becoming higher than the set potential when the photosensitive drum is used continuously.

(6) As described in detail, according to the present invention, the voltage generated on the photosensitive drum is changed in accordance with the number of times the photosensitive drum is used, so that the charged potential on the photosensitive drum can always be kept constant. Therefore, the printing lijigII density can be kept constant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electrophotographic printing apparatus, FIG. 2 is a graph showing the relationship between the number of times a photosensitive drum is used and the charging potential, FIG. 3 is a diagram showing the principle of an embodiment of the present invention, and FIG. A block diagram of this embodiment, FIG. 5 is a diagram showing the principle of the second embodiment of the present invention, FIG. 6 is a block diagram of the embodiment, and FIG. 7 is a modification of the device shown in FIG. 6. . In the figure, l is a high-voltage power supply, 2 is an electrode, 3 is a photosensitive drum, 4 is an exposure section, 5 is a developer, 6 is a transfer charger, 7 is a static elimination lamp, 8 is a collection device, 9 is a counter, 10tiD/A 11 is a classifier, 12 is a control voltage generator, 12g is a level setter, and 127 is a converter. Patent applicant Fujitsu Ltd. (1 other person) Representative patent attorney Akira Yamatani , 5I!l I6. Optical drum 18 rotations

Claims (2)

[Claims] (1) A counter that counts the number of rotations of the photoreceptor in an electrophotographic printing device that exposes a photoreceptor charged by a charging means to form a latent image, attaches toner to this latent image, and transfers it to paper. and a control voltage generating means for generating a control voltage based on the counted value, and the output voltage of the charging means is controlled by the control voltage generating means. (2) Claim α) characterized in that the control voltage generating means uses a classification means for classifying the rotation speed into a plurality of categories and a level setting means for outputting a level according to the classification. printing device.