JP3487714B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus equipped with a charging device used in copying machines, facsimiles, laser printers and the like.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram of an image forming apparatus.
Reference numeral 1 is a driving roller, 2 is a driven roller, 3 is a tension roller, 4 is a photosensitive member which is stretched over the driving roller 1, the driven roller 2 and the tension roller 3 and cyclically moves in the direction of the arrow, 5 is a discharge lamp, and 6 is a charging device. , 7 is an optical writing unit,
8 is a developing device, 9 is a transfer device, 10 is a fixing device, and 11 is a cleaning device.

In the image formation by this image forming apparatus, first, the surface of the photoconductor 4 is destaticized by the destaticizing lamp 5, and then the surface of the photoconductor 4 is uniformly charged by corona discharge in the charging device 6. The surface of the photoconductor is irradiated with laser light from the optical writing unit 7 to form an electrostatic latent image.
This electrostatic latent image is visualized by the toner contained in the developing device 8, and the visualized toner image is transferred to the photoreceptor 4.
It is transferred by the transfer device 9 onto the upper surface of the recording paper P that has been conveyed to the lower side, and is further fixed by the fixing device 10. The recording paper P on which the toner image is fixed is discharged to the outside of the apparatus. On the other hand, after the toner image is transferred, the cleaning unit 11 removes the residual toner from the photoconductor 4 and prepares for the next recording process.

FIG. 9 is a perspective view showing the appearance of the charging device. In the figure, 12 is a case, 13 is a grit, and 14 is a high voltage cable. 10 is a perspective view showing the structure of the charging device, and FIG. 11 is a sectional view showing the structure of the charging device. In FIGS. 10 and 11 , 15 is a charging wire, 16 is a spring installed at one longitudinal end of the case 12, and 17 is a spring.
Is a partition plate, 18a and 18b are V-shaped grooves provided in the partition plate 17,
9 is a hook provided at the other end in the longitudinal direction. To show these specific configurations, partition plates 17 are fixed to both ends in the longitudinal direction inside the case 12, a spring 16 is engaged with one end of the charging wire 15, and a hook 19 is engaged with the other end. There is. The charging wire 15 is stretched between the V-shaped grooves 18a and 18b by the bias of the spring 16. The charging wire 15 is connected to the high voltage cable 14 and supplied with a voltage. The grit 13 is placed in parallel with the charging wire 15 in the case 12 having the internal structure as described above.

FIG. 12 shows an electric circuit of the charging device 6. Power pack 20 to apply a high voltage of several KV to the charging wire 15 in FIG, 21 shows the tool E <br/> zener diode connected to the grid 13. In such a configuration, a high voltage is applied from the power pack 20 to the charging wire 15 to cause corona discharge, and the generated ions are uniformly attached to the surface of the photoconductor 4 by the grit 13 to charge the wire.

[0006]

In such a charging operation, dirt or the like is likely to adhere to the charging wire 15 partially or wholly, and if the dirt adheres to the charging wire 15, the charging ability in that part is lowered and the photoreceptor 4 of the photosensitive member 4 is deteriorated. The surface could not be uniformly charged, resulting in charging defects such as uneven charging. For this reason, there has been a problem that an image defect occurs in the electrostatic latent image formed on the surface of the photoconductor 4. As a countermeasure against this, there is an idea to constantly increase the current density of the charging wire to reduce the charging failure, but in this case, there have been problems such as an increase in the ozone generation amount and an early deterioration of the photoconductor as the current density increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which prevents uneven charging of a photosensitive member and suppresses deterioration of the photosensitive member and the amount of ozone generated even when dirt is attached to the charging wire.

[0008]

In order to achieve the above object, in the invention according to claim 1 , the charging wire of the charging device for uniformly charging the photosensitive member is provided at the tip of the first sheet during image formation. The feature is that the current density is made higher than usual.

According to the second aspect of the present invention, the charging wire of the charging device for uniformly charging the photosensitive member is set to be more than usual in the first sheet at the time of image formation depending on the time elapsed from the completion of the previous image recording. It is characterized in that the length of time for increasing the current density is changed.

According to the third aspect of the invention, the charging wire of the charging device for uniformly charging the photoconductor has a higher current density than usual in the first sheet during image formation, depending on the number of previously recorded images. The feature is that the length of time to do is changed.

[0011]

According to the structure described in claim 1 , by increasing the current density applied to the charging wire at the front end portion of the first sheet during image formation and discharging, the insulation of the charging wire whose insulation is increased by the adhered matter The sex can be reduced for a short time. As a result, the charging failure can be prevented at the normal current density after the trailing edge of the first sheet. Therefore, image formation can be obtained with high accuracy, and the amount of ozone generated can be suppressed for a longer period of time. Further, according to the configuration of claim 2 , at the time of image formation, the time elapsed after the completion of the previous image recording is completed. Accordingly, since the length of time of the high current density applied to the charging wire is changed, the energization time of the high current density applied to the charging wire can be efficiently obtained, and excessive energization can be eliminated. Therefore, charging failure on the photoconductor can be prevented without waste, and the amount of ozone generated can be suppressed.

According to the third aspect of the invention, the length of time of high current density applied to the charging wire is changed according to the number of previously recorded images at the time of image formation. It is possible to obtain an energization time with a high current density given to, and it is possible to eliminate excessive energization. Therefore, charging failure on the photoconductor can be prevented without waste, and the amount of ozone generated can be suppressed.

[0013]

It described embodiment of EXAMPLES present invention. FIG. 1 shows a control block diagram according to an embodiment of the present invention. In the figure, a timer 30 measures an interval from the completion of image recording to the start of the next image recording, and the counter 31 is
The number of sheets at the time of image recording is counted. The memory 32 has a control program for the charging device 6, the optical writing unit 7, the developing device 8, the transfer device 9, the fixing device 10, and the like.
And the interval time from the completion of image recording measured by the timer 30 to the start of the next image recording, or the charging wire set corresponding to each value of the number of sheets at the time of image recording counted by the counter 31. A table of energization conditions is stored. The operation panel 33 sends a key signal operated by an operator to the control section, and the control section 34 is composed of a microcomputer and controls the operation of each of the above-mentioned devices.

With the above-mentioned configuration, FIG. 2 shows a flowchart according to the first embodiment of the present invention . First, the image recording apparatus starts recording based on a start key of the operation panel 33 or an input signal from the outside (not shown) (Process 20).
1). When this recording is started, it is determined whether the image formation is the first sheet of the first sheet (process 202). If the image is the first sheet of the first sheet (process 202Y), the current of the charging wire 15 provided in the charging device 6 is determined. The density is increased to a predetermined value (step 203). Next, it is judged whether or not the image formation on the leading edge of the first sheet of paper is completed (process 204), and if it is completed (process 204Y), the current density passed through the charging wire 15 is set to a normal value at that timing. (Process 205) If not completed (Process 204N), a routine for monitoring completion of image formation on the leading edge of the first sheet of paper is entered. If it is not the first sheet (process 202N), process 205
Step before. Thereafter, it is monitored whether or not it is the final page of image formation (process 206), and if it is the final page (process 206Y), recording is completed when the sheet of the final page is ejected outside the apparatus (process 207). If it is not the final page (process 206N), the routine for monitoring the final page is entered. As described above, at the time of image recording, control is performed so that the current density flowing through the charging wire 15 only at the leading edge of the first sheet of paper is increased to a predetermined value, so that charging failure can be prevented and the amount of ozone generated can also be increased. It can be suppressed.

FIG. 3 shows the relationship between the energization time of the charging wire and the insulating property of the charging wire according to the first embodiment of the present invention. The line A shows the insulation value of the charging wire, and has a characteristic that the insulation property decreases as the energizing time applied to the charging wire becomes longer. Therefore, after the image forming apparatus is started, it can be seen that the insulating property of the charging wire is high and the charging failure is likely to occur at the time of forming the first image.
In this case, charging failure can be prevented by increasing the current density applied to the charging wire accordingly. Line B is the insulation value of the charging wire that causes the charging failure of the photoconductor.
Above this level, large and small charging defects occur on the photoconductor.

FIG. 4 shows a flowchart according to the second embodiment of the present invention. First, the image forming apparatus starts recording based on a start key of the operation panel 33 or an input signal from the outside (not shown) (process 301). When this recording is started, it is judged whether the image formation is the first sheet of the first sheet (process 302), and if it is the first sheet of the first sheet (process 30).
2Y), timer 3 indicates the elapsed time from the completion of the previous image recording.
0 is calculated based on the measurement of 0 (process 303), and the energization time of high current density of a predetermined value supplied to the charging wire 15 corresponding to the elapsed time is read from the memory 32 and set (process). 304), the charging wire 15 provided in the charging device 6 is energized with a high current density (step 305). Next, it is determined whether the first sheet of the first sheet has completed the image formation for one page (process 30).
6) If it is completed (process 306Y), the current density passed to the charging wire 15 at that timing is set to a normal value (process 307), and if not completed (process 306N), completion of the first sheet is monitored. Enter the routine. If it is not the first sheet (process 302N), the process proceeds to the step before the process 307. After that, it is monitored whether it is the final page of image formation (process 308), and if it is the final page (process 308)
Y), when the sheet of the last page is ejected out of the apparatus, recording is completed (process 309). If it is not the final page (process 308N), the routine for monitoring the final page is entered. As described above, the charging wire 15 is applied to the first sheet of the first sheet in correspondence with the elapsed time from the completion of the previous image recording.
Is set and the current density is controlled so as to be increased to a predetermined value. Therefore, charging failure can be prevented, and the photoconductor can be rapidly deteriorated and the amount of ozone generated can be suppressed.

FIG. 5 shows the relationship between the elapsed time from the completion of the previous image recording and the energization time of the high current density applied to the charging wire according to the second embodiment of the present invention. Line C
Shows the energization time value of high current density given to the charging wire under the condition that no charging failure occurs, and the energization time value becomes longer as the elapsed time from the completion of the previous image recording becomes longer. . This is because the electrical insulation of the charging wire is interrupted and the insulating property that has been temporarily lowered gradually increases. Therefore, if the time of the high current density given to the charging wire is lengthened accordingly, the charging failure can be prevented.

FIG. 6 shows a flowchart according to the third embodiment of the present invention. First, the image forming apparatus starts recording based on a start key on the operation panel 33 or an input signal from the outside (not shown) (process 401). When this recording is started, it is determined whether the image formation is the first sheet of the first sheet (process 402), and if it is the first sheet of the first sheet (process 40).
2Y), the number of recordings at the time of the previous image recording is calculated based on the data measured by the counter 31 (process 403), and a high current density of a predetermined value is supplied to the charging wire 15 corresponding to the number of recordings. The energization time is read from the memory 32 and set (process 404), and the current density of the charging wire 15 provided in the charging device 6 is set to a high current density and the energization is performed (process 405). Next, it is determined whether the first sheet of the first sheet has completed the image formation for one page (process 406),
If completed (process 406Y), the current density flowing through the charging wire 15 is returned to the normal value at that timing (process 4).
07) If not completed (process 406N), a routine for monitoring completion of image formation of the first sheet is entered. If it is not the first sheet (process 402N), the process is performed before the process 407. Thereafter, it is monitored whether or not it is the final page of image formation (process 408), and if it is the final page (process 408Y), recording is completed when the paper of the final page is ejected outside the device (process 409). If it is not the final page (process 408N), the routine for monitoring the final page is entered. As described above, the charging wire 15 is applied to the first sheet of the first sheet in correspondence with the number of sheets recorded in the previous image recording.
Is set and the current density is controlled so as to be increased to a predetermined value. Therefore, charging failure can be prevented, and the photoconductor can be rapidly deteriorated and the amount of ozone generated can be suppressed.

FIG. 7 shows the relationship between the number of previously recorded images and the energization time of the high current density applied to the charging wire according to the third embodiment of the present invention. Line E shows the energization time value of the high current density given to the charging wire under the condition that no charging failure occurs, and the energization time value is shorter if the number of previous image recording sheets is larger. This is because the insulating property of the charging wire changes depending on the frequency of energization to the charging wire. Therefore, by determining the energization time of the high current density applied to the charging wire in accordance with this characteristic, defective charging can be efficiently prevented.

[0020]

As described in the foregoing, according to the invention according to claim 1, by increasing the current density to be applied to the charging wire at the first sheet top portion during images formed, the photosensitive due to contamination of the charging wire The charging failure of the body can be prevented, and high quality image recording can be obtained. Further, it is possible to suppress the early deterioration of the photoconductor and the amount of ozone generated.

According to the second aspect of the invention, during image formation, the length of time of high current density applied to the charging wire is changed according to the elapsed time from the completion of the previous image recording. As a result, the application time can be determined without waste, the charging failure can be efficiently prevented, and the early deterioration of the photoconductor and the generation amount of ozone can be suppressed. Higher quality image recording can be obtained.

According to the third aspect of the invention, the length of time of high current density applied to the charging wire is changed according to the number of previously recorded images during image formation, so that the application is performed without waste. It is possible to efficiently prevent the charging failure due to the fixed time, and it is also possible to efficiently suppress the early deterioration of the photoconductor and the generation amount of ozone. Therefore, high quality image recording can be obtained.

[Brief description of drawings]

FIG. 1 is a control block diagram according to an embodiment of the present invention.

FIG. 2 shows a flowchart according to a first embodiment of the present invention.

FIG. 3 shows the relationship between the electrification time of the charging wire and the insulating property of the charging wire according to the first embodiment of the present invention.

FIG. 4 shows a flowchart according to a second embodiment of the present invention.

FIG. 5 shows the relationship between the elapsed time from the completion of image recording and the energization time of high current density applied to the charging wire according to the second embodiment of the present invention.

FIG. 6 shows a flowchart according to a third embodiment of the present invention.

FIG. 7 shows the relationship between the number of recorded images and the energization time of the high current density applied to the charging wire according to the fourth embodiment of the present invention.

FIG. 8 shows a block diagram of a conventional image forming apparatus.

FIG. 9 shows an external view of a conventional charging device.

FIG. 10 shows a perspective view of a conventional charging device.

FIG. 11 shows a cross-sectional view of a conventional charging device.

FIG. 12 shows an electric circuit diagram of a conventional charging device.

[Explanation of symbols]

1 ... Drive roller 2. Driven roller 3 ... Tension roller 4 ... Photoreceptor 5 ... Static elimination lamp 6 ... Charged device 7 ... Optical writing unit 8 ... Developing device 9 ... Transfer device 10: Fixing device 11 ... Cleaning unit 12 ... Case 13 ... Grit 14 ... High voltage cable 15 ... Charging wire 16… Slinging 17 ... Partition board 18 ... V-shaped groove 19 ... Hook 20 ... Power pack 21 ... Zener diode 30 ... timer 31 ... Counter 32 ... Memory 33 ... Operation panel 34 ... Control unit

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Claims (3)

(57) [Claims] 1. An image forming apparatus for forming an electrostatic latent image on a photoconductor, visualizing the electrostatic latent image with toner, and recording the image on a recording sheet. A charging device for uniformly charging the photoconductor. The image forming apparatus is characterized in that the charging wire has a current density higher than usual at the front end portion of the first sheet during image formation. 2. An image forming apparatus for forming an electrostatic latent image on a photoconductor, visualizing the electrostatic latent image with toner, and recording the image on a recording sheet. A charging device for uniformly charging the photoconductor. The image forming method characterized in that the charging wire for the first sheet is changed in length for a higher current density than usual in accordance with the time elapsed from the completion of the previous image recording on the first sheet during image formation. apparatus. 3. An image forming apparatus for forming an electrostatic latent image on a photoconductor, visualizing the electrostatic latent image with toner, and recording the image on a recording sheet. A charging device for uniformly charging the photoconductor. The image forming apparatus is characterized in that the charging wire of (1) is changed in length of time for increasing the current density higher than usual in accordance with the number of previously recorded images in the first sheet during image formation.