JPS61105578A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain always photographic images of high quality with a certain density by controlling the destaticization intensity in a destaticizing part in accordance with the reduction of sensitivity due to the elapse of time after the operation start of a photosensitive body so that this intensity falls within a certain time in accordance with said elapse of time and is a certain value after the certain time. CONSTITUTION:Just after the operation start time when the power source of a device is turned on, the destaticization intensity of a destaticizing lamp 8 is high because the terminal voltage of a capacitor 40 of an integrating circuit 41 is low, and the high photosensitive body sensitivity just after the operation start is reduced temporarily up to a certain value, and the surface potential formed on the photosensitive surface of a photosensitive drum 2 by the electrifying voltage applied from a charging charger 3 to the photosensitive surface is reduced by this reduction. As the result, the density of character images formed with a laser beam 4 from a laser beam generating device is not too high. when the photosensitive body sensitivity falls according as the time elapses the reduction of the photosensitive body sensitivity due to the destaticizing action of the destaticizing lamp 8 is lessened gradually, and the actual photosensitive body sensititivy in the part of the charing charging charger 3 is a certain value approximately, and the surface potential is a certain value approximately.

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 decrease in sensitivity of a photoreceptor over time is compensated for by reducing static elimination strength in response to the passage of time.

[Prior Art] In general, in an electrophotographic apparatus, a charging section consisting of a charging charger emits a laser beam along the circumference of a photosensitive drum rotating at a constant speed in response to a character code input from the outside. An exposure section for scanning, a developing section, a transfer section, and a defrosting section are respectively 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. Then: The character image formed by this laser beam is developed in the next developing section, and further 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 fixed in a fixing section. Note that the character image remaining on the transferred photosensitive surface is neutralized by the static eliminating section and is placed on standby for the next charging.

[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, 11
Light, 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 static elimination strength, charging voltage, exposure intensity, etc. are fixed to 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.

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, and as a result, the photographic character image obtained becomes too bright. Therefore, there was a problem that uniform photographic images with constant density could not always be obtained.

The present invention was made based on these circumstances.
□The purpose of this is to reduce the static electricity removal strength in response to the decrease in sensitivity of the photoreceptor, so that the surface potential of the photosensitive surface due to charging can be maintained at a nearly constant value, and the purpose is to maintain a constant density and high quality. An object of the present invention is to provide an electrophotographic device that can obtain photographic images.

[Means for Solving the Problems] The present invention forms an image on the photosensitive surface of a photoreceptor charged in a charging unit in an exposure unit, develops it in a developing unit to obtain a photographic image, and then roughly removes the charge. In an electrophotographic device that eliminates static electricity in the static elimination unit, the snow removal strength on the photosensitive surface in the static elimination 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 photoconductor. The value is lowered in response to time, and after a certain period of time has elapsed, it is controlled to a substantially constant value.

[Function] With an electrophotographic device configured in this way, the static elimination strength is high immediately after the start of operation and decreases over time, so it equivalently compensates for the decrease in sensitivity of the photoreceptor over time, and reduces the sensitivity due to charging. The surface potential of the surface becomes almost constant.

[Example] 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). A charging charger 3 that forms a charging section along the circumference of the photosensitive drum 2. A laser beam generator ft5 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 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.
1 is formed between the insertion opening 11 and the transfer section 7, and a paper feed row 513 and a paper feed guide 14 for guiding the paper 12 stored in the paper feed force bit 10 to the transfer section 7. 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 provided on the opposite side of the transfer section 7 to the paper feed 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. , a scan start position detector 54, a scan end position detector 55, and each of these position detectors 54. ．． 55 to irradiate the laser beam, and a mirror 58 to direct the laser beam to the photosensitive surface of the photosensitive drum 2.
It is made up of.

FIG. 3 is a block diagram showing a schematic configuration of the electrophotographic apparatus, and 20 in the figure is a CPLI that executes various calculation information processing. The CPLI 20 is connected to a ROM 22.0 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. I10 sends and receives control signals and data to and from each part
Controls the boat 26 etc.

This I10 boat 26 includes various sensors 27, 54, 55, etc. in the laser beam generator M5. A drive circuit 28 that supplies a drive voltage to the static elimination lamp 8. A drive circuit 29 that supplies a drive voltage to the charger 3.
A drive circuit 31° that supplies a drive voltage to the transfer charger 30 of the transfer section 7 and the photosensitive drum 22 rotating polygon mirror 5
2. Fixing rollers 17a, 17b, conveyor belt 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 pages? , a line data buffer is formed for storing one line of scan data read from this page print data buffer and converted by the character generator 23 into the aforementioned multiple scan data.

Further, the drive circuit 28 for the static elimination lamp 3 is constructed as shown in FIG. That is, one end of the static elimination lamp 8 is connected to a drive power supply terminal 34 that outputs a DC drive voltage of +24■ via the emitter-collector of an npn-type switching transistor 33, and the base terminal of the switching transistor 33 is connected to the I10 board. It is connected to the static elimination signal output terminal No. 26. The other end of the static elimination lamp 8 is grounded via a resistor 35 and connected to the emitter terminal of a pnp type amplification transistor 36. The collector terminal of the transistor 36 is grounded, and the base terminal is connected via a resistor 37 to a resistor 39 and a capacitor 40 of an integrating circuit 41 consisting of a resistor 39 and a capacitor 40 connected in series between a +5V control power supply terminal 38 and the ground. connected to the connection point. Note that a diode 41 for preventing backflow is connected between both terminals of the resistor 39.

The terminal voltage of the capacitor 4o of the integrating circuit 41 is determined by the time constant determined by the values of the resistor 39 and the capacitor 40, since a DC voltage of 5 cm is applied from the control power supply terminal 38 when the device is turned on and becomes operational. rise according to

This time constant is set so that the increase characteristic of the terminal voltage of the capacitor 40 corresponds to the characteristic curve A of FIG. 5, in which the photoreceptor sensitivity on the photosensitive surface of the photosensitive drum 2 decreases with respect to the elapsed time after the start of operation. Since the base terminal of the transistor 36 corresponds to the terminal voltage of the capacitor, when the switching transistor 33 is conductive, the collector current decreases as the terminal voltage of the capacitor 40 increases. and,
After a certain period of time, the collector current becomes almost zero. When the collector current decreases, the current flowing through the snow removal lamp 8 also decreases, and therefore the brightness of the static elimination lamp 8, that is, the static elimination intensity decreases.

Therefore, the static elimination strength is at a high value immediately after the start of operation of the device, as shown by the decreasing characteristic curve B in FIG.
The resistance decreases as time passes, and after a certain period of time the resistance reaches 35.
It becomes an almost constant value determined by the value of .

In an electrophotographic apparatus configured in this manner, the T! When the power is turned on, + from the power supply circuit (not shown)
5■ DC voltage is applied to the integrating circuit 4 via the control power supply terminal 38.
1. As a result, the terminal voltage of the capacitor 40, that is, the base terminal voltage of the transistor 36 is
9 and capacitor 40 according to the aforementioned time constant. At the same time, the photosensitive drum 2 starts rotating at a constant speed, and the static elimination signal output terminal of the I10 port 26 is
A static elimination signal of the same level is sent, and the switching transistor 33 becomes conductive. When the switching transistor 33 becomes conductive, current is supplied from the drive power supply terminal 34 to the static elimination lamp 8 . Immediately after the start of operation, the static elimination intensity of the static elimination lamp 8 is at a high value as shown in FIG. 6, as described above.

In this state, when the character code for one page is input from the external host computer via the interface 25,
Is the character code for this one page temporarily stored in the page print data buffer in RAM24? The data is read out line by line, converted into one line of scan data by the character generator 23, and stored in the line data buffer in the RAM 24.

When a print command is input, a charging signal is inputted to the drive circuit 29 of the charging charger 3 via the charging signal output terminal of the I10 boat 26. Then, the charging
The i-jerger 3 charges the photosensitive drum 2 at a predetermined charging voltage.
Charge the photosensitive surface of ゛.

Next, one row of scanning data stored in the row data buffer of the RAM 24 is sequentially read out and the laser beam generator 5
Send to. 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 the customer character image for one line is formed, RAM2
The character code for the next line is read from the page print data buffer of page 4, and the character code is sent to the character generator 23 in the same manner as described above.
The scan data is converted into one line of scan data and stored in the line data buffer. 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.

Further, the photosensitive surface of the photosensitive drum 2 on which the transferred character image is formed in the transfer section 7 is irradiated with a static eliminating lamp 8 to eliminate the static electricity, and the transferred character image remaining on the photosensitive surface is removed by a wiping roller 9. It is wiped off and prepared for the next charging and exposure.

In an electrophotographic apparatus configured in this manner, the terminal voltage of the capacitor 40 of the integrating circuit 41 shown in FIG. Static neutralization strength is high. Generally, when the static elimination strength is high, the sensitivity of the photoreceptor on the photosensitive surface of the photosensitive drum 2 tends to decrease temporarily. The amount of this decrease roughly corresponds to the static elimination strength. Therefore, the high photoconductor sensitivity immediately after the start of operation is temporarily reduced to a certain constant value, so that the surface formed on the photoconductor surface in response to the charging voltage applied to the photoconductor surface of the photoconductor drum 2 of the charging charge t-3. The potential becomes lower by that amount. As a result, the density of the character image formed by the laser beam 4 from the laser beam generating device 5 does not become too dark as in the conventional device.

After this charging and exposure are completed, the sensitivity of the photoreceptor on the photosensitive surface returns to a value corresponding to the reduction characteristic curve A in FIG. 5, which is lower than the original sensitivity to photosensitive surface by the number of times of charging and exposure. Since the static elimination strength decreases according to the decreasing characteristic curve B in FIG. 6, as the sensitivity of the photoconductor decreases over time, the amount of decrease in the sensitivity of the photoconductor due to the static elimination action of the static elimination lamp 8 also gradually decreases. Therefore, the actual sensitivity of the photoreceptor in the charging charger 3 section is always a substantially constant value, and the surface potential formed by charging on the photosensitive surface is also a substantially 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 electric charge charged in the capacitor 40 of the integrating circuit 41 is also discharged, 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, when the power is turned on, the integration circuit 41
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 static removal strength in the snow removing section is adjusted to a predetermined level from the operation start time by adjusting the static removal intensity in the snow removal section in response to the decrease in photoconductor sensitivity that occurs over time after the photoconductor starts operating. Within a certain period of time, it will be lowered in response 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 drawings]

This figure shows 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 a schematic configuration of a laser beam generator, and FIG. 3 is a block diagram. 4 is a drive circuit diagram of the static elimination lamp, FIG. 5 is a photoreceptor sensitivity characteristic diagram, and FIG. 6 is a static elimination strength characteristic diagram of the static elimination section. 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
...CPLJ, 23...Character generator,
24...RAM, 25...Interface, 26
・I/O boat, 28, 29. 31... Drive circuit, 33... Switching transistor, 36...
Transistor, 39...Resistor, 40...Capacitor, 41...Integrator circuit.

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,
Furthermore, 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 and is placed on standby for the next charging, the static eliminating strength for the photosensitive surface in the static eliminating section is determined by In response to a decrease in sensitivity due to the passage of time after the body starts working, the sensitivity is reduced in response to the elapsed time within a predetermined certain time from the start time of work, and after the certain time has passed, the sensitivity is reduced to a substantially constant value. An electrophotographic apparatus characterized in that it is equipped with a static elimination strength control means. (2) The electrophotographic apparatus according to claim (1), wherein the static elimination intensity control means includes an integrating circuit including a resistor and a capacitor.