JPS61100772A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To make possible satisfactoryn continuous printing without uneven density in the case of printing continuously plural sheets by weakening the electrostatic charge to a photosensitive body in the stage of printing the 1st 1- several sheets and thereafter intensifying the electrostatic charge to the photosensitive body. CONSTITUTION:A CPU21 executes electrostatic charge control in accordance with the program data of a ROM22. The count value N of a counter provided in a RAM24 is set at '1' when the number of sheets to be printed is set at a plural number of sheets. A control signal Sc is set at a low level in the stage of count value N=1. An electrostatic charge signal Sv is outputted in this state to execute the electrostatic charge control process. The count value N is added by 1 when the process is completed. The signal Sc is set at a high level when the count value N>=2. The signal Sv is similarly outputted and the electrostatic charge control process is executed. The count value N is added by 1 when the process ends. Such process is repeated. The adequate electrostatic charge is thus executed even if the sensitivity of the drum 2 increases in printing of the 1st sheet and even if the sensitivity of the drum 2 decreases gradually in the printing of the 2nd and subsequent printing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention includes at least a charging section, an exposing section, and a developing section that are sequentially arranged along the moving direction of the photoconductor, and the photoconductor charged in the charging section is The present invention relates to an improvement in an electrophotographic apparatus that forms an image on a photosensitive surface in an exposure section and further develops it in a development section to print on paper.

[Prior Art] Generally, in this type of electrophotographic apparatus, when printing multiple sheets in succession, the sensitivity of the photosensitive surface of the photoreceptor is high for the first one to several sheets, and then the sensitivity gradually decreases. begins to decline. On the other hand, in conventional electrophotographic apparatuses, when printing a plurality of sheets in succession, the charging voltage of the charging unit is the same from beginning to end.

[Problems to be Solved by the Invention] However, if the charging voltage is the same from beginning to end, the first one or several sheets will be charged more than necessary, resulting in insufficient exposure. te stamp total 11
becomes too dark, and when printing after one or several sheets, the charge is too weak and the exposure becomes overexposed, resulting in the print being too light.
There was a problem in that the printing degree was highly uneven between the beginning and the end of printing, making it impossible to perform good continuous printing.

This invention was made to solve this problem, and when printing multiple sheets in succession, the charge on the photoreceptor is weakened during the first one to several sheets of printing, and after that, the charge on the photoreceptor is reduced. It is an object of the present invention to provide an electrophotographic device that can perform continuous printing without uneven density by increasing the charging of the body and thereby performing charging in accordance with changes in the sensitivity of the photosensitive surface of a photosensitive member. do.

[Means for Solving the Problems] The present invention includes at least a charging section, an exposing section, and a developing section that are sequentially arranged along the moving direction of the photoconductor, and the photosensitive surface of the photoconductor charged by the charging section is In an electrophotographic device that creates an image in an exposure section and then develops it in a development section to print on paper, a high-voltage generator that supplies high voltage to the charging section and a high-voltage generator that supplies a high voltage to the charging section and when printing multiple sheets continuously, Level controller 7 controls the level of the high voltage supplied from the high voltage generator to the charging section low for the first one to several sheets, and then controls the level high.
It has steps.

[Function] In the present invention having such a configuration, when printing a plurality of sheets continuously, the high voltage level supplied from the high voltage generator to the charging section is controlled to be low for the first one to several sheets. When printing more than one or several sheets, the high voltage level supplied to the charging section is increased to strengthen the charge on the photoreceptor, thereby preventing the charge from becoming unnecessarily loose. This prevents the exposed portion from becoming overexposed.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the present invention will be described as applied to an electrophotographic printer using a laser.

FIG. 1 shows the overall configuration, and 1 is a casing. A photosensitive drum 2 as a photosensitive member having a photosensitive surface formed along the outer periphery is installed in the center of the housing 1, and the photosensitive drum 2 is rotated at a constant speed by a motor (not shown). Along the circumference of the photosensitive drum 2,
A charger 3 forming a charging section, a generator 5 for scanning laser light m4 forming an exposure section, a developing section 6, a transfer charger 7 forming a transfer section, and a static elimination lamp 8 forming a static elimination section. A wiping roller 9 is provided.

An insertion slot 1 for a paper feed cassette 10 is provided at the lower side of the housing 1.
1 is formed, and a paper feed roller 13 and a paper feed guide 14 for guiding the paper 12 stored in the paper feed cassette 10 to the transfer charger 7 are formed between the insertion opening 11 and the transfer section 7. It is provided. Note that a paper insertion section 15 for manually feeding paper is also provided on the side surface of the housing 1. On the opposite side of the transfer charger 7 to the paper feed guide 14, there is a pressure-type fixing unit 1 consisting of a conveyor 16 and two fixing rollers 17a and 17b.
8 are arranged.

As shown in FIG. 2, the laser beam generating device 5 includes a laser light emitting element 51 that is turned on and off according to information;
A rotating polygon mirror 52 and an fθ lens 53 that horizontally scan the laser light from the light emitting element 51, a scan start position sensor 54, a scan end position sensor 55, and each sensor 54, 55 are irradiated with laser light, respectively. It is composed of anti-q1 mirrors 56 and 57 and a mirror 58 for directing the laser beam to the photosensitive surface of the photosensitive drum 2.

FIG. 3 is a block diagram showing the circuit configuration, in which 21 is a CPU (central processing unit) constituting the control section, 22 is a CPU 2
1 is a ROM (read only memory) in which program data for controlling each part is stored, 23 is a character generator, and 24 is a RAM (random access memory) in which an area for storing information for printing is formed. 25 is an interface for taking in information from the outside; 26 is a drive device 27 that drives various sensors such as the scan start sensor 54 and scan end sensor 55; a lighting device 28 that controls lighting of various lamps; A separate static elimination circuit 29 that controls lighting of the lamp 8, and a high voltage output control circuit 30 that supplies high voltage to the charger 3.
, a high-voltage generator 31 that supplies high voltage to the transfer charger 7, and input/output to a motor drive device 32 that drives and controls various motors such as a motor that rotationally drives the photosensitive drum 2 and a motor that rotationally drives the rotating polygon mirror 52. This is the 1,,"O port that performs control and controls the output of information to the exposure control circuit 33 that controls the laser emitting element 51. The CPtJ 21, ROM 22, character generator 23, RAM 24, interface 2
5. It is connected to the I10 boat 26 by a hash line 34. The CPU 21 is connected to the interface 2.
5 is stored in the RAM 24, and when that information is subsequently to be printed, the information is converted into character pattern information by the character generator 23 and then sent to the exposure control circuit via the I10 port 26. 33. In addition, the CPU2
1 is a drive device 2 for various sensors via an I10 boat 26 based on program data in a ROM 22.
7. Selectively control various lamp lighting devices 28, two static elimination control circuits, high voltage output control circuit 30, high voltage generator 31, and motor drive device 32.

The high voltage output control circuit 30 is an NPN circuit as shown in FIG.
first, second and third transistors 301.302.
303 and a level control means formed by a variable resistor 304, and a high voltage generator 305. Said first
The transistor 301 has its collector connected to the +V terminal, and its emitter connected to one end of the variable resistor 304. The other end of the variable resistor 304 is connected to the collector of the second transistor 302 via a resistor 306 and to the collector of the third transistor 303 via a resistor 307.

The emitters of the second and third transistors 302 and 303 are grounded. A movable terminal of the variable resistor 304 is connected to an input terminal of the high voltage generator 305. Then, a charging signal SV for starting charging is supplied to the base of the first transistor 301, and a control signal Sc is supplied to the base of the second transistor 302 to the inverter 3.
08.309 in series and the third
The control signal Sc is supplied to the base of the transistor 303 via an inverter 310. The charging signal S
v and the control signal Sc are supplied from the 1/'O port 26. The resistance value of the resistor 306 is set larger than the resistance value of the resistor 307. The high voltage generator 305 sets the high voltage level supplied to the charger 3 high when the input voltage is high, and sets the high voltage level supplied to the charger 3 low when the input voltage is low.

The CPU 21 performs charging control shown in FIG. 5 based on program data in the ROM 22.

That is, when the number of sheets to be printed is set, the count value N of the counter provided in the RAM 24 is set to "1". When the count value N=1, the control signal Sc is set to low level. In this state, a charging signal Sv is output to perform charging control ft processing, and when this processing is completed, the count value N is incremented by 1. Then, when the count value N≧2 is reached, the control signal Sc is set to a high level, and the charging signal Sv is output in the same manner as described above to perform the charging control Il process, and when this process is completed, the count value N is increased by +1.
Repeat the process.

In the apparatus according to the embodiment of the present invention having such a configuration.

When printing multiple sheets is set and printing is started, the control signal Sc is set to low level for the first sheet, so the control signal Sc is set to low level for the first sheet.
The second transistor 303 is turned on, and the second transistor 302 is turned off. When the charging signal Sv is inputted in this state, the first transistor 301 is turned on, and a +
V lightning voltage will be applied. However, variable resistor 3
The level of the voltage signal output from the movable terminal 04 is lower than when the resistor 306 is connected. As a result, the high voltage generator 305 supplies a relatively low level high voltage to the electrostatic charger 3, and the charging of the photosensitive drum 2 by the electrostatic charge v3 is weakened. Therefore, even if the sensitivity of the photosensitive drum 2 is high when printing the first sheet, the charging is weakened and the photosensitive drum 2 is appropriately charged, resulting in insufficient exposure by the laser beam in the exposed area. It is done well without any problems. Therefore, there is no risk that the printing density of the first sheet will be high.

Furthermore, since the control signal Sc is set to a high level for the second and subsequent sheets, the second transistor 302 is turned on and the third transistor 303 is turned off. When the charging signal Sv is input in this state, the first transistor 301 turns on, and the variable resistor 304 and the resistor 3
A +V voltage will be applied across the series circuit with 06.

Therefore, the level of the voltage signal output from the movable terminal of variable resistor 304 becomes higher than when resistor 307 is connected. As a result, the high voltage generator 305 supplies a relatively high level of high voltage to the charging charger 3, and the charging of the photosensitive drum 2 by the charging charger 3 is strengthened. Therefore, even if the sensitivity of the photosensitive drum 2 gradually decreases in printing from the second sheet onward, the charging is strengthened, so that the photosensitive drum 2 is appropriately charged.
Exposure by the laser beam in the exposed area can be performed satisfactorily without becoming excessively exposed. Therefore, there is no risk that the print density of the second and subsequent sheets will become lighter.

In this way, when printing multiple sheets in succession, the first
Since the charging voltage of the charger 3 is changed from a low level to a high level between the second and subsequent sheets,
It is possible to eliminate unevenness in printing density due to changes in the sensitivity of the photosensitive surface of the photosensitive drum 2, and it is possible to perform good continuous printing with substantially uniform density.

In the above embodiment, the charging voltage is changed between the first sheet and the second and subsequent sheets, but the charging voltage is not necessarily limited to this. The charging voltage may be changed after that number of sheets.

Further, although the above embodiments have been described in which the present invention is applied to an electrophotographic printer using a laser, the present invention is not necessarily limited to this, and can also be applied to a normal copying machine.

[Effects of the Invention] As detailed above, according to the present invention, when printing a plurality of sheets in succession, the charge on the photoreceptor is weakened during the first printing of one to several sheets, and thereafter, the charge on the photoreceptor is increased. It is possible to provide an electrophotographic apparatus that can perform good continuous printing without uneven density by increasing the charging of the photosensitive surface of the photosensitive member and thereby performing charging in accordance with changes in the sensitivity of the photosensitive surface of the photosensitive member.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a diagram showing the overall configuration, Fig. 2 is a perspective view showing the configuration of the laser beam generator, Fig. 3 is a block diagram showing circuit development, and Fig. 4
This figure is a specific circuit configuration diagram of the high-voltage output control circuit in FIG. 3, and FIG. 5 is a flowchart showing the main processing of CPIJ. 2... Photosensitive drum (photosensitive member), 3... Charger (charging section), 5... Laser beam generator @ (exposure section), 6... Developing section, 21... CPtJ (central processing device), 22... ROM (read only memory), 30... high voltage output control circuit, 301.302.3
03...Transistor, 304...Variable resistor, 3
05...High pressure generator, 306.307...Resistor. 1 L;l Figure 4 Figure 5

Claims (1)

[Claims] Along the moving direction of the photoconductor, at least a charging section, an exposing section,
An electrophotographic apparatus in which developing sections are sequentially arranged, the exposing section forms an image on the photosensitive surface of the photoconductor charged by the charging section, and the developing section performs development to print on paper, A high voltage generator supplies a high voltage to the charging section, and when printing multiple sheets in succession, the level of the high voltage supplied from the high voltage generator to the charging section is adjusted for the first one to several sheets. An electrophotographic apparatus comprising a level control means for controlling the level to a low level and then controlling the level to a high level.