JP2005352112A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which has a simple structure, and a low cost, efficiently diffuses and removes ozone staying in a corona electrifier after copying, and prevents deterioration of an image carrier, thereby obtaining satisfactory images. <P>SOLUTION: In the image forming apparatus in which the corona electrifier is disposed such that a first opening defined in its front faces the image carrier, the corona electrifier having a discharge electrode for applying charges to the image carrier and a shield section formed from side plates and a back plate for shielding the discharge electrode, a second opening for forcing ozone staying in the corona electrifier out of it is disposed in the lowest part of the shield section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus capable of obtaining a good image by preventing deterioration of an image carrier due to ozone generated from a corona charger.

  In an image forming apparatus equipped with a corona charger, a corona charger having a discharge electrode for applying an electric charge to an image carrier and a shield portion for shielding the discharge electrode has an image bearing on the first opening on the front surface. It is placed facing the body.

  The corona charger generates ozone when a high voltage is applied to the discharge electrode to apply a charge to the image carrier. In order to deteriorate the image carrier when ozone is generated, a technique is disclosed in which the ozone in the corona charger is exhausted by blowing or sucking with a fan or the like during copying (discharging) or resting of the image forming apparatus. (See Patent Document 1). However, there is a problem that the structure becomes complicated and the cost increases when it is attempted to blow or suck with a fan or the like, and it is difficult to reduce the size of the image forming apparatus.

Further, a technique is disclosed in which an opening for exhausting ozone is provided in a shield portion without blowing or sucking with a fan or the like to prevent deterioration of the image carrier (see Patent Document 2 and Patent Document 3).
JP-A-6-236096 JP-A-6-67509 JP 47-37432 A

  Usually, the image blur occurs when the image is left for a long time after being continuously copied for a long time in a high humidity environment. Image blurring occurs prominently at the position of the corona charger, and the cause is that high-concentration ozone stays in the corona charger for a long time, resulting in deterioration of the chargeability of the surface of the image carrier at that position. Caused by.

  However, if the air is not blown or sucked by a fan or the like, particularly if the image forming apparatus is left standing for a long time after being continuously copied for a long time in a high humidity environment (the image forming apparatus is suspended), the air stays inside the corona charger. Ozone is less likely to be exhausted than when there is a fan, etc., and the position of the image carrier facing the corona charger is partially degraded, and partially striped image blur is likely to occur due to the degradation. There's a problem.

  An object of the present invention is a simple structure and low cost, and efficiently diffuses and removes the ozone remaining in the corona charger after the end of copying, thereby preventing deterioration of the image carrier and good image quality. It is an object of the present invention to provide an image forming apparatus that obtains the above.

  The object of the present invention is achieved by any of the following means.

  (1) A corona charger for forming a discharge part for applying an electric charge to the image carrier and a shield part composed of a side plate and a back plate for shielding the discharge electrode. In the image forming apparatus arranged opposite to the first, a second opening for exhausting ozone remaining in the corona charger to the outside is provided in a lower part at the lowest position of the shield part. Image forming apparatus.

  (2) The image forming apparatus according to (1), wherein the second opening portion is provided so as to avoid the closest portion of the shield portion from the discharge electrode.

  (3) The image forming apparatus according to (1) or (2), wherein the second opening is provided between the image carrier and an end of the side plate.

  (4) When the height from the surface of the image carrier to the end of the side plate is h1, and the height from the image carrier to the discharge electrode is h2, 0.4 <h1 / h2 <0. The image forming apparatus according to claim 3, wherein the image forming apparatus is 9.

  (5) The image forming apparatus according to any one of (1) to (4), wherein the corona charger is provided with an air inlet for ventilation.

  Since it comprised as mentioned above, there exist the following effects.

  According to the first aspect of the present invention, the ozone remaining in the corona charger can be efficiently exhausted and opposed to the corona charger at a low cost and with a simple configuration while the image forming apparatus is stopped. A good image can be obtained by preventing the deterioration of the portion of the image carrier.

  According to the second aspect of the present invention, in addition to the effect of the first aspect, the discharge efficiency is further improved and discharge unevenness can be prevented.

  According to the third and fourth aspects of the invention, in addition to the effect of the first aspect, in particular, during the rest of the image forming apparatus, the residence of ozone in the portion of the image carrier facing the corona charger is reduced. In addition, the deterioration due to ozone can be reduced.

  According to the fifth aspect of the present invention, it becomes easy to maintain the atmospheric pressure balance inside the corona charger by the smooth intake of air from the intake port provided in the corona charger, and the remaining ozone is efficiently exhausted. It became so.

  First, the overall configuration of the image forming apparatus according to the embodiment will be described. FIG. 1 is a front view showing an overall configuration of an image forming apparatus including a corona charger. As shown in FIG. 1, the image forming apparatus main body A includes an image forming unit 1, an image processing unit 2, an image writing unit 3, a high voltage power supply unit 4, a paper feeding / conveying unit 5, a fixing device 6, a paper discharging unit 7, A re-transport unit (ADU) 8 for duplex copying is provided.

  An image reading device SC and an automatic document feeder DF are mounted on the upper part of the image forming apparatus main body A. A document d placed on the document table of the automatic document feeder DF with the first surface facing upward is conveyed in the direction of the arrow, and an image on one or both sides of the document is read by the optical system of the image reading device SC. It is read into the CCD image sensor C1. The analog signal photoelectrically converted by the CCD image sensor C1 is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the image processing unit 2 and then sent to the image writing unit 3.

  In the image writing unit 3, output light from the semiconductor laser is applied to the image carrier 10 of the image forming unit 1 to form a latent image.

  In the image forming unit 1, processing such as charging, exposure, development, transfer, separation, and cleaning is performed, and the image is transferred to the paper S conveyed from the paper feed conveyance unit 5. The paper S carrying the image is fixed by the fixing device 6 and discharged from the paper discharge unit 7 to the paper discharge tray 7C. Alternatively, the single-sided image processed paper S sent to the re-conveying means 8 by the paper discharge path switching plate 7A is again subjected to double-sided image processing in the image forming unit 1 and then discharged by the paper discharge roller 7B of the paper discharge unit 7. It is discharged to the tray 7C.

  FIG. 2 is a front view showing the configuration of the image forming unit 1 in FIG. As shown in FIG. 2, reference numeral 10 denotes an image carrier, which is an image carrier in which an organic or inorganic photoconductive layer is provided on the surface of a substrate. The image carrier 10 is driven and rotated in the direction of the arrow. A corona charger 40 uniformly charges the surface of the image carrier 10. An image exposure unit 13 irradiates a light image on the image carrier 10 to form an electrostatic latent image. A developing device 14 develops the electrostatic latent image formed on the image carrier 10 to form a toner image. Reference numeral 5B denotes a registration roller that feeds the paper S fed from the paper feed cassette 5A to the transfer position in synchronization with the formation of the electrostatic latent image on the image carrier 10. A transfer corona discharger 15 transfers the toner image on the image carrier 10 onto the paper S. Reference numeral 16 denotes a separation corona discharger, which peels off the transferred paper S from the surface of the image carrier 10. A separation claw 17 is in pressure contact with the surface of the image carrier 10 and peels off the paper S attached on the image carrier 10. Reference numeral 18 denotes a pre-charging static elimination means, and 19 denotes a simultaneous transfer exposure means. 6 is a fixing device, and 20 is a cleaning device.

  Next, the above-described corona charger 40 will be described in detail.

(Embodiment 1)
FIG. 3 is a front view showing the configuration of the corona charger after the end of copying in the image forming apparatus according to the first embodiment. As shown in FIG. 3, the corona charger 40 </ b> A is disposed slightly below the left side surface of the image carrier 10 when the image forming apparatus is viewed from the front. In the corona charger 40A, a first opening 47 is disposed so as to face the image carrier 10. The corona charger 40A includes a discharge electrode 44 and a shield part 41 that shields the discharge electrode 44, and the shield part 41 includes a back plate 41c and side plates 41a and 41b.

  A predetermined high voltage DC voltage is applied to the discharge electrode 44, and the side plate 41a is grounded. The shield part 41 has a second opening 46a in the lower part at the lowest position. The second opening 46a removes ozone staying inside the corona charger 40A while the image forming apparatus is at rest. It is provided in order to efficiently diffuse and remove it by utilizing its own weight. The second opening 46a also serves to exhaust ozone generated during copying (discharge) of the apparatus. Note that image blur occurs most easily when a certain amount of copies are continuously copied (for example, 1000 sheets or more) and then left for a long time (for example, at night), so even if the ozone diffusion rate is slow. What is necessary is just to spread reliably.

  Further, in order to keep the atmospheric pressure balanced after ozone is exhausted from the second opening 46a, an intake port (not shown) of the corona charger 40A is provided in a direction orthogonal to the rotation direction of the image carrier 10. The same applies to other embodiments described later.

  Here, the ozone removal method will be described. First, when the image forming apparatus is copying (discharging), a high voltage is applied to the discharge electrode 44 to uniformly charge the surface of the image carrier 10. The ozone generated at this time generates ozone wind and is exhausted from the second opening 46a. Further, while the image forming apparatus is not in operation, no new ozone is generated, but the ozone staying in the corona charger 40A is at the lowest position by utilizing the property that ozone is heavier than air and tends to accumulate downward. Ozone is diffused and removed efficiently from the second opening 46a provided at a lower portion.

  As described above, the image bearing member facing the corona charger can be efficiently exhausted by the simple configuration at low cost while the image forming apparatus is stopped and the ozone staying in the corona charger is efficiently exhausted. A good image can be obtained by preventing the deterioration of the portion. In addition, the exhaust of ozone during copying (during discharge) is performed well.

(Embodiment 2)
The second embodiment is a modification of the first embodiment, and parts that are mechanically the same as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 4 is a front view showing the configuration of the corona charger after the end of copying in the image forming apparatus according to the second embodiment.

  As shown in FIG. 4, the corona charger 40B is composed of a discharge electrode 44 and a shield part 41 for applying a charge to the image carrier 10, and the shield part 41 is composed of a back plate 41c and side plates 41a and 41b. .

  The side plate 41 a is disposed away from the discharge electrode 44 by the nearest distance h <b> 3, and the closest portion P is at a position closest to the discharge electrode 44. The discharge electrode 44 can stably and mainly efficiently discharge to the closest portion P.

  The second opening 46b is provided in the lower part at the lowest position of the shield part 41 so as to avoid the closest part P. While the image forming apparatus is at rest, the ozone staying inside the corona charger 40B is gradually diffused to the outside using the weight of ozone to remove the ozone. The second opening 46b also serves to exhaust ozone generated during copying (discharging).

  Here, the ozone removal method will be described. During copying (during discharge), a predetermined high voltage is applied to the discharge electrode 44, and discharge is mainly efficiently performed on the closest portion P on the side plate 41a, so that the surface of the image carrier 10 is uniformly charged. The ozone generated at this time is exhausted from the second opening 46b. Further, during the rest, the ozone staying inside the corona charger 40B gradually goes out of the second opening 46b by utilizing the property that the ozone is heavier than the air and tends to accumulate in the lower part. Diffuse to remove ozone.

  As described above, the discharge unevenness is small, the discharge efficiency is not impaired, the simple configuration is low-cost, and the ozone staying inside the corona charger is efficiently exhausted during the pause of the image forming apparatus. A good image can be obtained by preventing the deterioration of the portion of the image carrier facing the corona charger. In addition, the exhaust of ozone during copying (during discharge) is performed well.

(Embodiment 3)
The third embodiment is a modification of the second embodiment, and parts that are mechanically the same as those of the second embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 5 is a front view showing the configuration of the corona charger after the end of copying in the image forming apparatus according to the third embodiment.

  As shown in FIG. 5, the corona charger 40C includes a discharge electrode 44 and a shield part 41 for applying a charge to the image carrier 10, and the shield part 41 includes a back plate 41c and side plates 41a and 41b. Yes.

  The side plate 41 a is disposed at a distance of the nearest distance h 3 from the discharge electrode 44, and the closest portion P of the side plate 41 a is at a position closest to the discharge electrode 44. The discharge electrode 44 can stably and mainly efficiently discharge to the closest portion P.

  The second opening 46c avoids the nearest portion P at the lower portion of the shield 41, and the second opening 46c is provided between the image carrier 10 and the side plate 41a. It is possible to prevent ozone from staying on the surface of the image carrier 10 and the lower part of the corona charger 40C at the lowest position. Further, the second opening 46c removes ozone by gradually diffusing ozone staying inside the corona charger 40C to the outside using its own weight while the image forming apparatus is at rest. The second opening 46b also serves to exhaust ozone generated during copying (discharging).

  When the height from the surface of the image carrier 10 to the end of the side plate 41a is h1, and the height from the image carrier to the discharge electrode 44 is h2, 0.4 <h1 / h2 <0.9. .

  Here, the ozone removal method will be described. During copying (discharging), a predetermined high-voltage DC voltage is applied to the discharge electrode 44 to uniformly charge the surface of the image carrier 10. The ozone generated at this time is exhausted from the second opening 46c. Further, during the rest, the ozone staying inside the corona charger 40C gradually takes ozone from the second opening 46c by utilizing the property that the ozone is heavier than the air and tends to accumulate in the lower part. Disperse outside to remove ozone.

  As described above, ozone can be prevented from stagnation in the portion of the image carrier facing the corona charger 40C during the pause, the discharge unevenness is small, the discharge efficiency is not impaired, and the simple configuration is low cost. During the pause of the image forming apparatus, ozone accumulated in the corona charger is efficiently exhausted so that a good image can be obtained by preventing deterioration of the portion of the image carrier facing the corona charger. become. In addition, the exhaust of ozone during copying (during discharge) is performed well.

(Embodiment 4)
The fourth embodiment is a modification of the second embodiment, and parts that are mechanically the same as those of the second embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 6 is a front view showing the configuration of the corona charger after the end of copying in the image forming apparatus according to the fourth embodiment.

  As shown in FIG. 6, the corona charger 40D includes a discharge electrode 44 and a shield part 41, and the shield part 41 includes a back plate 41c and side plates 41a and 41b.

  The back plate 41 c is disposed at a distance of the nearest distance h 3 from the discharge electrode 44, and the closest portion P of the back plate 41 c is closest to the discharge electrode 44. The discharge electrode 44 can stably and mainly efficiently discharge to the closest portion P.

  The second opening 46d is provided in the lower part at the lowest position of the shield 41 in order to exhaust the ozone remaining inside the corona charger 40D to the outside during the rest, but during copying ( It also serves to exhaust ozone generated during discharge.

  Here, a method for removing ozone will be described. During copying (during discharge), a high voltage is applied to the discharge electrode 44 to uniformly charge the surface of the image carrier 10. The ozone generated at this time is exhausted from the second opening 46d. Further, during the rest, the ozone staying inside the corona charger 40D gradually takes ozone from the second opening 46d by utilizing the property that the ozone is heavier than the air and tends to collect in the lower part. It diffuses outside and removes ozone.

  As described above, discharge unevenness is reduced, discharge efficiency is not impaired, simple configuration, low cost, and efficient exhaust of ozone remaining in the corona charger during the rest of the image forming apparatus, A good image can be obtained by preventing the deterioration of the portion of the image carrier facing the corona charger. In addition, the exhaust of ozone during copying (during discharge) is performed well.

(Embodiment 5)
The fifth embodiment is a modification of the third embodiment, and parts that are mechanically the same as those in the third embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 7 is a front view showing the configuration of the corona charger after the end of copying in the image forming apparatus according to the fifth embodiment.

  As shown in FIG. 7, the corona charger 40E includes two discharge electrodes 44 (44a, 44b) and a shield part 41 that shields the discharge electrode 44. The shield part 41 further includes a back plate 41c, a side plate 41a, 41b.

  The corona charger 40E is provided with a first opening 47 facing the image carrier 10. A predetermined high voltage DC voltage is applied to the discharge electrode 44, and the side plate 41a is grounded.

  The side plate 41a is disposed away from the discharge electrode 44a by the nearest distance h3, and the closest portion P of the side plate 41a is closest to the discharge electrode 44a. The discharge electrode 44a can stably and mainly efficiently discharge the closest part P. The side plate 41b is also arranged at a distance of the closest distance h3 from the discharge electrode 44b, and the closest portion P of the side plate 41b is closest to the discharge electrode 44b.

  The second opening 46e is disposed between the image carrier 10 and the side plate 41a, and the height from the surface of the image carrier 10 to the end of the side plate 41a is h1, and the height from the image carrier to the discharge electrode 44a. When the height is h2, 0.4 <h1 / h2 <0.9.

  In addition, the second opening 46e is provided in the lower part at the lowest position of the shield 41 in order to allow the ozone staying inside the corona charger 40E to flow out to the outside during the pause. It also serves as an exhaust of ozone generated during discharge.

  Here, a method for removing ozone will be described. During copying (during discharge), a high voltage is applied to the discharge electrode 44 to uniformly charge the surface of the image carrier 10. The ozone generated at this time is exhausted from the second opening 46e. Further, during the pause, the ozone staying inside the corona charger 40E gradually takes ozone from the second opening 46e by utilizing the property that the ozone is heavier than the air and tends to accumulate in the lower part. It is removed by diffusing outside.

  As described above, the discharge unevenness is small, the discharge efficiency is not impaired, the simple configuration is low-cost, and the ozone staying inside the corona charger is efficiently exhausted during the pause of the image forming apparatus. A good image can be obtained by preventing the deterioration of the portion of the image carrier facing the corona charger.

  In the embodiment, the example in which the inlet of the corona charger is provided in the direction orthogonal to the rotation direction of the image carrier in order to keep the atmospheric pressure balanced after the ozone is exhausted from the second opening. However, the present invention is not limited to this. For example, even if the shield portion is provided at a position other than the second opening, the same effect can be obtained.

An embodiment according to the present invention will be described, but the present invention is not limited to this embodiment.
1) Image forming apparatus The image forming apparatus shown in FIGS. 1 and 2 is used.

Linear velocity is 230mm / sec
Discharge electrode: wire diameter φ60μm, material is tungsten wire, high voltage DC voltage is 5.7KV
Environmental conditions; humidity 20%, temperature 10 ° C
2) Evaluation item and measurement method Image blur: Evaluation using halftone Discharge unevenness: Visual evaluation 3) Evaluation method Evaluation with image carrier after continuous printing of 100,000 sheets 4) Evaluation scale Image blur: 5-point evaluation (A best, B good, C normal, D somewhat bad, E bad)
Discharge unevenness: 3-point evaluation (○ good, △ intermediate, × defective)
5) Data As shown in Table 1.

6) Test results As shown in Table 1, the second opening is arranged between the image carrier and the side plate end as in the corona charger shown in FIG. When the height from the image carrier to h1 is h1, and the height from the image carrier to the discharge electrode is h2, 0.4 <h1 / h2 <0.9 is satisfactory. If the lower limit of the allowable range is exceeded, ozone cannot be exhausted sufficiently to the outside, and if the upper limit of the allowable range is exceeded, it is difficult to efficiently discharge from the discharge electrode 44 to the nearest part P, resulting in uneven discharge. Discharge efficiency also deteriorates. Preferably 0.5 <h1 / h2 <0.8.

1 is a front view illustrating an overall configuration of an image forming apparatus including a corona charger. FIG. 2 is a front view illustrating a configuration of an image forming unit in FIG. 1. 3 is a front view showing a configuration of a corona charger after the end of copying in the image forming apparatus according to Embodiment 1. FIG. FIG. 10 is a front view illustrating a configuration of a corona charger after the end of copying in the image forming apparatus according to the second embodiment. FIG. 10 is a front view showing the configuration of a corona charger after the end of copying in the image forming apparatus according to Embodiment 3; FIG. 10 is a front view showing a configuration of a corona charger after the end of copying in an image forming apparatus according to Embodiment 4; FIG. 10 is a front view illustrating a configuration of a corona charger and an image carrier after completion of copying in an image forming apparatus according to Embodiment 5;

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image carrier 40A, 40B, 40C, 40D, 40E Corona charger 41 Shield part 41a, 41b Side plate 41c Back plate 44, 44a, 45b Discharge electrode 46a, 46b, 46c, 46d, 46e 2nd opening part 47 1st Opening P Nearest part

Claims (5)

A corona charger that forms a shield electrode composed of a discharge electrode for applying an electric charge to the image carrier, and a side plate and a back plate for shielding the discharge electrode, with the first opening on the front face the image carrier In the image forming apparatus arranged
2. An image forming apparatus according to claim 1, wherein a second opening for exhausting ozone remaining in the corona charger to the outside is provided at a lower portion of the shield portion at the lowest position. The image forming apparatus according to claim 1, wherein the second opening portion is provided so as to avoid the closest portion of the shield portion from the discharge electrode. The image forming apparatus according to claim 1, wherein the second opening is provided between the image carrier and an end of the side plate. When the height from the surface of the image carrier to the end of the side plate is h1, and the height from the image carrier to the discharge electrode is h2, 0.4 <h1 / h2 <0.9. The image forming apparatus according to claim 3. 5. The image forming apparatus according to claim 1, wherein the corona charger is provided with an air inlet for ventilation.

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