JPS61173268A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To eliminate the unevenness of density from the beginning to the end of printing and to execute the satisfactory continuous printing by enlarging the output power of the exposure part to the first 1 - several sheets and con trolling the output power smaller after that. CONSTITUTION:For the first sheet, a control signal Sc is set to a low level, and therefore, the third transistor 305 executes the ON action and the fourth transistor 306 executes the OFF action. In such a condition, a reference voltage supplied to the input terminal (-) of the second operational amplifier 302 is determined by a partial pressure with resistances 313 and 314, and therefore, the level of the reference voltage is comparatively set higher. Thus, the first transistor 303 is biased deeply, and in such a condition exposure data DT are inputted and then, based upon the data a laser light emitting element 51 turns on and executes the OFF action, and the light emitting power at the time of ON becomes larger. After the second sheet, the control signal Sc is set to a high level.

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. 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.

[Conventional technology]

In general, in an electrophotographic apparatus, a charging unit consisting of a charging Char-Shear scans a laser beam along the circumference of a photosensitive drum rotating at a constant speed in response to a character code P input from the outside, for example. exposure section, development section, transfer section,
A static eliminator is placed in each. In addition, near the transfer part,
A paper insertion section that feeds paper to the transfer section and a fixing section that fixes the character image transferred by the transfer section are provided.

In such an electrophotographic apparatus, when a character code for printing a photo on paper is input from the outside, character pattern data corresponding to this character code is read out from the character generator, and the laser beam ray photoconductor is By scanning the charged photosensitive surface, a character image corresponding to the input character code is formed on the photosensitive surface. The character image formed by this laser beam is then developed at the next developing section, and further transferred to the paper fed from the paper feeding section at the next transfer section. Then, the paper onto which the character image has been transferred is fixed in a fixing section. In addition,
The character image remaining on the transferred photosensitive surface is neutralized by the static eliminating section.
Waits for the next charge.

[Problem that the invention seeks to solve]

However, the electrophotographic apparatus configured as described above has the following problems.

The sensitivity of the photoreceptor used in such an electrophotographic apparatus, that is, the surface potential due to charging with respect to the charging voltage applied by the charging charger, exhibits a very high value immediately after the power is turned on and operation starts. However, when characters are photographically printed on a large number of sheets by repeating charging, exposure, development, transfer, and static elimination, the sensitivity of the photoreceptor decreases over time and reaches a nearly constant value after a certain period of time. Then, for example, when the operation is stopped for several hours or more, the photoreceptor sensitivity returns to its original high value.

Therefore, if the charging voltage applied by the charging charger is a constant value, immediately after the start of operation, the surface potential due to charging will not be abnormally high, and image formation by laser beam exposure will be relatively insufficient. As a result, the resulting photographic character image becomes too dark. Moreover, after a certain period of time has elapsed, the surface potential due to charging becomes low due to the low sensitivity of the photoreceptor, and the charging is erased by exposure, resulting in a photographic character image that is too bright. Therefore, there is a problem in that uniform photographic images with constant density cannot always be obtained.

The present invention was developed based on the above circumstances, and its purpose is to adjust the exposure power for printing the first one to several sheets as necessary according to the user's judgment. It is an object of the present invention to provide an electrophotographic apparatus that can maintain the brightness of an image formed on a photosensitive surface at a substantially constant value after exposure by increasing the size of the image, and can always obtain a high-quality photographic image with a constant density.

[Failure to solve the problem]

In the present invention, at least a charging section, an exposing section, and a developing section are sequentially disposed along the moving direction of the photoreceptor, and the exposing section forms an image on the photosensitive surface of the photoreceptor charged by the charging section, and then develops the photoreceptor. In an electrophotographic device that performs printing on paper by developing it in a separate section,
a selection means for selecting whether or not to perform exposure intensity correction; and when this selection means selects exposure intensity correction, the output power of the exposure section is increased for the first one to several images;
An exposure power control means is provided for controlling the output/4' power of the exposure section to a small value for a few sheets or more.

[Effect]

In the present invention having such a configuration, when exposure intensity correction is selected by the selection means, for example, when the power is turned on first thing in the morning or when the power is turned on again after being turned off for a long time, the first to For printing a few sheets, increase the power of the exposed section to prevent insufficient exposure due to excessive charging, and when printing more than one or several sheets, reduce the charging by reducing the low power of the exposed section. This prevents over-exposure due to exposure, and adjusts the glow of the exposed area appropriately depending on the degree of charge on the photoreceptor.

[Embodiments of the invention]

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

FIG. 1 is a schematic cross-sectional view showing the general structure of an electrophotographic apparatus according to an embodiment. In the figure, reference numeral 1 denotes a housing, and a photosensitive drum 2 having a photosensitive surface formed along its outer periphery is installed in the center of the housing 1. The photosensitive drum 2 is rotated at a constant speed by a motor (not shown). Along the circumference of the photosensitive drum 20, there is a charging charger 3 that forms a charging section, and a radar beam generator 5 that outputs a scanning laser beam 4 that forms an exposure section. Developing section 6. Transfer section 7 having a transfer charger. A static eliminating run f8 and a wiping row 29 forming a static eliminating section are provided.

An insertion slot 1 for a paper feed cassette 10 is provided at the lower side of the housing 1.
1 is formed between the insertion opening 11 and the transfer section 7, a paper feed roller 13 for guiding the paper 12 stored in the paper feed cassette 10 to the transfer section 7, and a paper feed roller 14 are formed. is provided. Note that a paper insertion section 15 for manually feeding paper is provided on the side surface of the housing 1. A transport conveyor 16 and two fixing rollers 1 are located on the opposite side of the transfer section 7 from the paper feed guide 14.
A fixing section 18 consisting of 7g and 17b is provided.

Furthermore, at the upper part of the paper insertion section 15 on the side surface of the housing 1, there is a correction means for selecting whether or not to perform exposure intensity correction. A tongue 19 is attached.

As shown in FIG. 2, the laser beam generator 5 includes:
Turns on in response to character/turn data information read from the character generator.

A laser beam emitting element 5 which is turned off, a rotating polygon mirror 52 and an fθ lens 53 that horizontally scan the radar beam from the light emitting element 51, a scanning start position detector 54, a scanning end position detector 55, etc. A reflecting mirror 56 that irradiates a laser beam to each position detector 54 and 55.
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, where 21 is a CPU (central processing unit) that constitutes a control section, and 22 is an R in which program data for the CPU 21 to control each section is stored.
OM (Read Only Memory), 23 is a character generator, 24 is RAM (Random Access Memory) in which an area for storing information for printing, etc. is formed, 25 is an interface for importing information from the outside. , 26 are various sensors such as the scan start position detector 54 and the scan end position detector 55, and a correction button 19.
a detection circuit 27 that detects a pressing operation of , a lighting device 28 that controls lighting of various lamps, a static elimination control circuit 29 that controls lighting of the static elimination lamp ``8'', a high voltage generator 30 that supplies high voltage to the charger 3; A high voltage generator 31 that supplies high voltage to the transfer charger 7, 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 I10 date which performs input/output control for the laser light emitting element 51 as well as output control of information to the exposure power control circuit 33 which controls the output i4 of the laser light emitting element 51. The CPU 21, ROM 22, and character generator 2
3, the RAM 24, the interface 25, and the I10 port 26 are connected by a path line 34. The CPU 21 stores information input from the outside via the interface 25 in the RAM 24, and when printing the information thereafter, converts the information into character/turn information by the character generator 23, and then converts the information into character/turn information. -) 2t; Output to the exposure/warming control circuit 33 is controlled. Further, the CPU 21 reads Ilo! based on the program data of '2 in the ROM.
−) ,? t; various sensors and corrections selectively control the detection circuit 27 of the tongue 19, the lighting device 28 of various lamps, the static elimination control circuit 29, the high voltage generator 30, 31, and the motor drive device 32.

As shown in FIG. 4, the exposure power control circuit 33
, the second operational amplifier 301, 302 and the first NPN type,
Second, third and fourth transistors 303.304.30
It is composed of 5.3θ6 and various resistances. Suwachi,
The first operational amplifier 301 has its input terminal ←) connected to one control terminal of the laser emitting element 51, its input terminal (G) connected to a +V power supply, and its output terminal connected through a resistor 307. It is connected to the input terminal (+) of the second operational amplifier 302. Said second operational amplifier 302
The output terminal of the first transistor 903 is connected to the (-) terminal of the first transistor 903 via a resistor 308. It is connected to the terminal and its emitter is grounded.

The collector and emitter of the second transistor 304 are connected to the base and emitter of the first transistor 303. The second transistor 304 is connected to the +V power supply through resistors 310 and 311 in series, and is grounded through the resistors 310 and 312 in series. Exposure data DT consisting of character turn information is supplied to the second transistor 304 via the resistor 310.

The third transistor 305 has its collector connected to a resistor 3.
13.314 is connected in series to the +V power supply, and its emitter is grounded, and the fourth transistor 3
06 has its collector connected to the +V power supply via the resistor 315 and the resistor 314 in series, and its emitter is grounded. The connection point of the resistors 313, 314, 315 is connected to the second operational amplifier 30 via a resistor 316.
2 input terminal ←). The resistance value of the resistor 313 is set to a larger value than the resistance value of the resistor 315. The control signal Sc is supplied to the pace of the third transistor 305 via an inverter 317, and is also supplied to the pace of the fourth transistor 306 via inverters 31B and 319. The exposure data DT and the control signal Sc are output from the I10 port 26.

The CPU 21 performs exposure control shown in FIG. 5 based on program data in the ROM 22. That is, when this electrophotographic apparatus is powered on, the I10 port 26
, it is checked via the detection circuit 27 whether or not the correction button 19 has been depressed when the power is turned on. If there is a push-down operation, it is determined that the power has been turned on first thing in the morning or after a long period of time has elapsed, and when several sheets of paper 12 to be stamped are set, one of the above-mentioned If the correction button 19 is not pressed down when the power is turned on, the printer happens to have finished printing a few photos and the power to the device is cut off for a short time, and when N=l, the control signal Sc is set to a low level. Set. In this state, exposure data DT is output to perform exposure processing, and when this processing is completed, the count value N is incremented by one. Then, when the count value N≧2 is reached, the control signal Se is set to a high level, and the exposure data DT is output in the same manner as described above to perform the exposure process, and when this process is completed, the process of incrementing the count value N by 1 is repeated. .

In the apparatus according to the embodiment of the present invention having such a configuration, when the power-on correction presses down the button 19 and then sets printing of multiple sheets and starts printing, the control signal Ss is low for the first sheet. level, so the third transistor 3θ
5 is turned on, and the fourth transistor 306 is turned off. In this state, the reference voltage supplied to the input terminal ←) of the second operational amplifier 302 is determined by the voltage division between the resistors 313 and 314, so the level of the reference voltage is set relatively high. Therefore, the first transistor 303 is deeply biased, and when the exposure data DT is inputted in this state, the laser light emitting element 51 turns on and off based on the data. hoe
growing. In other words, the exposure for the first
(The power becomes larger. Therefore, even if the photosensitive drum 2 has a high sensitivity and is overly charged during printing of the first sheet, sufficient exposure can be achieved by increasing the exposure power, and image formation by exposure is good. Therefore, there is no risk that the printing density of the first sheet will become dark and the printed surface will become dark.

Also, for the second and subsequent sheets, the control signal Sc is set to ), so the fourth transistor 306
is turned on, and the third transistor 305 is turned off. In this state, the input terminal of the second operational amplifier 302 (
Since the reference voltage supplied to (c) is determined by the voltage division between the resistors 315 and 314, the level of the reference voltage is set relatively low. Therefore, the first transistor 30.9 is shallowly biased, and when the exposure data DT is inputted in this state, the radar light emitting element 51
operates on and off, but the light emission power when it is on is small.

In other words, the power of exposure for the second and subsequent sheets becomes smaller. Therefore, even if the sensitivity of the photosensitive drum 2 decreases and the charging weakens when printing the second and subsequent sheets, the exposure i4 power is weakened, so the exposure in the exposed area will not become over-exposed. In some cases, imaging is performed well. Therefore, there is no risk that the print density of the second and subsequent sheets will become lighter.

In addition, if the power is turned on while the correction button 19 is pressed down, it may be necessary to turn off the power for a short time after printing some photos, and then turn the power back on again. Since the sensitivity of the drum 2 has already decreased, in this case, the count value N=2 and the exposure power is weakened in the same way as the operation for the second and subsequent sheets described above. Therefore, the first 1
Even when the number of sheets is 1, the exposure at the exposure section does not tend to be overexposed, and image formation is performed satisfactorily.

In this way, if necessary, such as when turning on the power first thing in the morning or turning it on again after being turned off for a long time, you can change the exposure power from small to small for the first shot and the second and subsequent shots. Since the printing density is changed, 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 exposure i4 value is changed between the first sheet and the second and subsequent sheets.
The exposure power may be changed after about three sheets and after that number.

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.

〔Effect of the invention〕

As detailed above, according to the present invention, the power of the exposure section is increased at the time of printing the first several sheets of paper, depending on the user's judgment, to prevent insufficient exposure due to excessive charging. Moreover, when printing after a few sheets of one wafer, the power of the exposure section is reduced to prevent over-exposure, and there is no unevenness in density from the beginning to the end of printing, allowing for good continuous printing. A photographic device can be provided.

[Brief explanation of drawings]

The figures show an 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 the circuit configuration, and FIG. 4
This figure is a specific circuit configuration diagram of the exposure i4 word control circuit in FIG. 3, and FIG. 5 is a flowchart showing exposure control processing by the CPU. 2... Photosensitive drum (photosensitive member), 3... Charger (charging section), 5... Laser beam generator (exposure section), 6... Developing section, 19... Correction? Tan, 2 no.
...CPU (Central Processing Unit), 22...ROM (Read Only Memory), 33...Exposure power control circuit, 5...Laser light emitting element, 301.302...
・Operation amplifier, 303.304.305.306...
Transistor, 313.314.315...Resistance.

Claims (1)

[Claims] Along the direction of movement of the photoconductor, at least a charging section, an exposure 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 selection means for selecting whether or not to perform exposure intensity correction; and when this selection means selects exposure intensity correction, the first
An electrophotographic apparatus, characterized in that an electrophotographic apparatus is provided with an exposure power control means that increases the output power of the exposure section for a few sheets, and decreases the output power of the exposure section for one to several subsequent sheets.