JPS61105568A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain photographic images of high quality with a certain density by controlling an electrifying voltage to a photosensitive surface in an electrifying part in accordance with the reduction of sensitivity due to the elapse of time after the operation start of a photosensitive body. CONSTITUTION:Just after the operation start, the output voltage of a high voltage generating circuit 33 is low because the terminal voltage of a capacitor 38 of an integrating circuit 39 is low. As the result, the value of the electrifying voltage applied to the photosensitive surface of a photosensitive drum 1 from a charging charger 3 is low. This electrifying voltage rises along a rise characteristic curve determined by the time constant of the integrating circuit 39 in accordance with the elapse of time after the operation start time. This rise characteristic curve is set so as to correspond to a reduction characteristic curve of the sensitivity of the photosensitive surface of the photosensitive drum 2. As the result, the density of character images formed by a laser beam generating device 5 is always held in a certain level, and photographic images of high quality in the certain density level are always obtained just after the operation start as well as a certain time after the operation start.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic apparatus that forms an image on the photosensitive surface of a charged photoreceptor in an exposure section and develops it in a development section to obtain a photographic image. In particular, the present invention relates to an electrophotographic apparatus in which a reduction in sensitivity of a photoreceptor over time is compensated for by increasing a charging voltage in response to the passage of time.

[Prior Art] Generally, in an electrophotographic apparatus, for example, along the circumference of a photosensitive drum rotating at a constant speed, ? ! A charging section consisting of an electric charger, an exposure section that scans a laser beam in response to a character code input from the outside, a developing section, a transfer section, and a snow removal section are arranged. Further, a paper insertion section for feeding paper to the transfer section and a fixing section for fixing the character image transferred by the transfer section are provided near the transfer section.

In such an electrophotographic apparatus, when a character code for printing a photograph on paper is input from the outside, character pattern data corresponding to this character code is read out from the character generator, and a laser beam is directed onto the photoreceptor based on this character pattern data. By scanning the charged photosensitive surface, a character image corresponding to the input character code is created on the photosensitive surface. The character image formed by this laser beam is then developed in the next developing section, and roughly transferred to the paper fed from the paper feeding section in the next transfer section. and,
The paper onto which the character image has been transferred is inspected in a fixing section. Note that the character image remaining on the transferred photosensitive surface is neutralized by a static eliminating section and is used for the next charging process.

[Problems to be Solved by the Invention] However, the electrophotographic apparatus configured as described above has the following problems. The sensitivity of the photoreceptor used in such an electrophotographic device, that is, the surface potential due to charging with respect to the charging voltage applied by the charging charger, is as shown in Figure 5, immediately after the power is turned on and the operation starts. shows a very high value. However, charging, B light, and development.

When characters are photographically printed on a large number of sheets of paper by repeating transfer and static elimination, the sensitivity of the photoreceptor decreases over time and reaches a substantially 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 fixed at a constant value, the surface potential due to charging will become abnormally high immediately after the start of operation, and image formation by laser beam exposure will be relatively insufficient. Become. As a result, the resulting photographic character image becomes too dark. In addition, after a certain period of time, 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
The resulting photographic character image is too bright. therefore,
There was a problem in that uniform photographic images with constant density could not always be obtained.

The present invention has been made based on the above circumstances, and its purpose is to increase the charging voltage in response to the decrease in sensitivity of the photosensitive member, thereby keeping the surface potential of the photosensitive surface due to charging almost constant. It is an object of the present invention to provide an electrophotographic apparatus that can maintain a constant density and always obtain high-quality photographic images at a constant density.

[Means for solving the IBi problem] The present invention creates an image on the photosensitive surface of a photoreceptor charged by a charging unit, and develops it in a developing unit to obtain a photographic image. In an electrophotographic device that eliminates static electricity in a static eliminator, the charging voltage on the photosensitive surface in the charging unit is adjusted within a predetermined period of time from the start of operation in response to a decrease in sensitivity over time after the start of operation of the photoreceptor. The value is increased in response to the elapsed time, and is controlled to a substantially constant value after a certain amount of time has elapsed.

[Function] In an electrophotographic apparatus configured as described above, the charging voltage is low immediately after the start of operation and increases as time passes, so that the decrease in sensitivity of the photoreceptor over time is equivalently compensated for, and the photosensitive voltage due to charging is reduced. The surface potential of the surface becomes almost constant.

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

FIG. II1 is a schematic cross-sectional view showing a schematic configuration 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). A charging charger 3 that forms a charging section along the circumference of the photosensitive drum 2. A laser beam generator 5 that outputs a scanning laser beam 4 that forms an exposure area. Developing section 6. Transfer section 7 having a transfer charger. A static eliminating lamp 8 and a wiping roller 9 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.
A paper feed roller 13 and a paper feed guide 14 are formed between the insertion opening 11 and the transfer section 7 for guiding the paper 12 stored in the paper feed cassette 10 to the transfer section 7. It is provided. Note that a paper insertion section 15 for manually feeding paper is provided on the side surface of the housing 1. A conveyor 16 and two fixing rollers 17 are located on the opposite side of the transfer section 7 to the spinning paper guide 14.
A fixing section 18 consisting of a and 17b is provided.

As shown in FIG. 2, the laser beam generator 5 includes:
A laser beam light emitting element 51 that turns on and off in response to character pattern data information read out from a character generator, a rotating polygon mirror 52 and an fθ lens 53 that horizontally scan the laser beam from this light emitting element 51. , the scanning start position detector 54, the scanning end position detector 55, and the reflection that causes the multi-position detectors 54 and 55 to be irradiated with a laser beam! 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 a schematic configuration of the electrophotographic apparatus, and 20 in the figure is a CPU that executes various calculation information processing. The CPU 20 is connected to a ROM 22.22, which stores fixed data such as control programs, via a path line 21 consisting of a data bus, an address bus, etc. A character generator 23 that stores character pattern data corresponding to character codes input from the outside. A RAM 24 that temporarily stores variable data such as character codes input from the outside. For example, an interface 25 for receiving character codes sent from an external host computer via a transmission path. It also controls the I10 port 26, etc., which transmits and receives control signals and data to and from each part.

This I10 boat 26 includes various sensors 27, 54, 55, etc. inside the laser beam generator 5. Various lamps such as the static elimination lamp 8 28. A drive circuit 29 that supplies a driving voltage to the charging charger 3. A drive circuit 31 that supplies drive voltage to the transfer charger 30 of the transfer section 7.
and the photosensitive drum 21 rotating polygon 152. Fixing roller 17a.

17b, conveyor 16. Various motors 32 and the like that rotationally drive the paper feed roller 13 and the like are connected. The I10 boat 26 also sends each character pattern data read from the character generator 23 to the laser beam generator 5.

In the character generator 23, each character pattern is divided into a large number of parts in the vertical direction, and each divided pattern is displayed and stored as scan data.

In the RAM 24, there is a 1 to be printed input from an external host computer via an interface 25.
A page print data buffer that stores character codes for a page, and a line data buffer that stores one line of scan data read from the page print data buffer and converted into the aforementioned multiple scan data by the character generator 23. is formed.

Further, the drive circuit 29 of the charger 3 is constructed as shown in FIG. 4. That is, a high voltage generation circuit 33 that generates a high voltage to be sent to the charging charger 3.
The gate input terminal G of is connected to the +5V control power supply terminal 3 via the emitter-collector of the switching transistor 34.
5. This switching transistor 3
The base terminal of No. 4 is connected to the charging signal output terminal of the I10 boat 26. Further, the output voltage adjustment terminal IN of the high voltage generation circuit 33 is a connection point between a resistor 37 and a capacitor 38 of an integrating circuit 39 consisting of a resistor 37 and a capacitor 38 connected in series between a +5V m control power supply terminal 36 and the ground. It is connected to the. Note that a diode 40 for preventing backflow is connected between both terminals of the resistor 37.

The terminal voltage of the capacitor 38 of this integrating circuit 39 is determined by the time constant determined by the values of the resistor 37 and the capacitor 38, since a DC voltage of 5 cm is applied from the control power supply terminal 36 when the device is turned on and becomes operational. rise according to

This time constant is set so that the increasing characteristic of the terminal voltage of the capacitor 38 corresponds to the decreasing characteristic curve of the photoreceptor sensitivity on the photosensitive surface of the photosensitive drum 2 with respect to the elapsed time after the start of operation shown in FIG. Therefore, the input voltage of the output voltage adjustment terminal IN of the high voltage generation circuit 33 is a low value immediately after the start of operation of the device, increases as time passes, and becomes a substantially constant value after a certain period of time.

In an electrophotographic apparatus configured as described above, when the apparatus is turned on in order to print photographic character images on a certain number of sheets or more continuously, +5
The DC voltage of
is applied to As a result, the terminal voltage of the capacitor 38,
That is, the input voltage at the output voltage adjustment terminal IN of the high voltage generation circuit 33 starts to rise according to the above-described time constant determined by the resistor 37 and the capacitor 38.

In this state, when the character code for one page is input from the external host computer via the interface 25,
This character code for one page is once stored in the page print data buffer in the RAM 24, and then read out line by line, converted into scan data for one line by the character generator 23, and stored in the line data buffer in the RAM 24. Stored.

Then, when a printing command is input, the photosensitive drum 2 starts rotating at a constant speed. At the same time, the drive circuit 29 of the charging charger 3 is connected to the charging signal output terminal of the I10 port 26.
An H-level charging signal is input to the terminal.

In the drive circuit 29, the input H-level charging signal is input to the base terminal of the switching transistor 34, so the switching transistor 34 becomes conductive. When the switching transistor 34 becomes conductive, the gate input terminal G of the high voltage generation circuit 33 is connected from the control power supply terminal 35 to +
A gate signal of 5v is applied. In response to the input of this gate signal, a high voltage is sent to the charging charger 3 from the output terminal 0tJT. The charger 3 charges the photosensitive surface of the photosensitive drum 2 with a charging voltage corresponding to the input voltage. Note that the high voltage value sent to the charging charger 3 is determined in accordance with the voltage value applied to the output voltage adjustment terminal IN, that is, the terminal voltage of the capacitor 38 of the integrating circuit 39. Therefore, immediately after turning on the power,
The voltage applied to the charger 3 has a small value.

Next, one row of scanning data stored in the row data buffer of the RAM 24 is sequentially read out and laser beamed! −
The signal is sent to the program generator 5. The laser beam generator 5 sequentially scans the charged photosensitive surface of the photosensitive drum 2 with a laser beam based on each scanning data sequentially received. As a result, one line of character image corresponding to one line of character code is formed on the photosensitive surface. When a character image for one line is formed, the next one from the page print data buffer in the RAM 24 is formed.
The character code for a line is read out, converted into scan data for one line by the character generator 23, and stored in the line data buffer in the same manner as described above. Then, the laser beam generator 5 forms the next line of character images on the photosensitive surface.

In this way, character images are sequentially formed on the photosensitive surface of the photosensitive drum 2, which is rotated at a constant speed.

The character image for one page formed on the photosensitive surface of the photosensitive drum 2 is
As described above, the image is developed in the developing section 6 and transferred onto the paper 12 fed from the paper feed cassette 10 in the transfer section 7 .

The photographic character image transferred onto the paper 12 is fixed by fixing rollers 17a and 17b of the fixing section 18. Then, the paper 12 on which one page of photographic character images has been formed is discharged from the fixing section 18 to the outside of the housing 1.

In an electrophotographic apparatus configured in this way, the terminal voltage of the capacitor 38 of the integrating circuit 39 in FIG. is also low. As a result, the charging voltage value applied to the photosensitive surface of the photosensitive drum 2 of the charging charger 3 is a low value as shown in FIG. As time elapses from the operation start time, this charging voltage increases according to a rising characteristic curve determined by the time constant of the integrating circuit 39 as shown in the figure. This increasing characteristic curve is set to correspond to the decreasing characteristic curve of the photoreceptor sensitivity of the photosensitive surface of the photosensitive drum 2 shown in FIG. Therefore, when the photoconductor sensitivity is high immediately after the start of operation, the charging voltage at the charging charger 3 is low, and the charging voltage increases in response to a decrease in the photoconductor sensitivity, so that the surface potential formed by charging on the photoconductor surface is low. becomes an almost constant value.

As a result, the density of the character image formed by the laser beam generator 5 is always maintained at a constant level.

Therefore, a high quality photographic image with a constant density level can always be obtained even immediately after the start of operation or after a certain period of time has elapsed.

Note that when the printing of photographic characters on a certain number of sheets of paper is finished, the power to the device is turned off, the operation is stopped, and a downtime of several hours has elapsed, the photoconductor sensitivity of the photoconductor drum 2 returns to its original value as described above. At the same time, the charge stored in the capacitor 38' of the integrating circuit 39 is also discharged via the high voltage generating circuit 33, so that the terminal voltage returns to the original low voltage.

Note that the present invention is not limited to the embodiments described above. In the embodiment, at the same time as the power is turned on, the integrating circuit 39
Although the voltage supply is started for the first page (first sheet), the voltage supply may be started in synchronization with the print command for the first page (first sheet).

[Effects of the Invention] As explained above, according to the present invention, the charging voltage in the charging section is adjusted to a predetermined value from the start time of operation by adjusting the charging voltage in the charging section in response to the decrease in photoreceptor sensitivity due to the passage of time after the start of operation of the photoreceptor. Within a certain period of time, it will increase according to the elapsed time,
After a certain period of time has elapsed, it is controlled to a substantially constant value. Therefore, the decrease in photoreceptor sensitivity of the photoreceptor can be compensated for, the surface potential of the photoreceptor surface due to charging can be maintained at a substantially constant value, and high-quality photographic images with constant density can always be obtained.

[Brief explanation of the drawing]

The drawings show an electrophotographic apparatus according to an embodiment of the present invention, in which Fig. 1 is a schematic cross-sectional view showing the whole, Fig. 2 is a perspective view showing the schematic configuration of the laser beam generator, and Fig. 3 is a block diagram. FIG. 4 is a drive circuit diagram of the charger, FIG. 5 is a photoreceptor sensitivity characteristic diagram, and FIG. 6 is a charging voltage characteristic diagram of the charger. DESCRIPTION OF SYMBOLS 1... Housing, 2... Photosensitive drum, 3... Charger, 4... Laser beam, 5... Laser beam generator, 6... Developing section, 7... Transfer section , 8...
- Static elimination lamp, 9... Wiping roller, 10... Paper feed cassette, 12... Paper, 18... Fixing unit, 20
...CPU123...Character generator, 2
4...RAM, 25...Interface, 26.
... I10 port, 29... Drive circuit, 33... High voltage generation circuit, 34... Switching transistor,
37...Resistor, 38...Capacitor, 39...Integrator circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) At least a charging section, an exposing section, a developing section, and a static eliminating section are sequentially disposed along the moving direction of the photoconductor, and the exposure section is used to form an image on the photosensitive surface of the photoconductor charged by the charging section. image,
Further, in an electrophotographic apparatus in which a photographic image is obtained through development in the developing section, and the photoreceptor is neutralized in the static eliminating section to wait for the next charging, the charging voltage applied to the photosensitive surface in the charging section is set to In response to the decrease in sensitivity due to the passage of time after the body starts working, the sensitivity is increased in response to the elapsed time within a predetermined certain time from the start time of work, and after the certain time has elapsed, it becomes an approximately constant value. An electrophotographic apparatus comprising a charging voltage control means. (2) The electrophotographic apparatus according to claim (1), wherein the charging voltage control means is constituted by an integrating circuit including a resistor and a capacitor.