JP4900666B2 - Scorotron charger and image forming apparatus provided with the charger - Google Patents

Description

  The present invention relates to a scorotron charger and an image forming apparatus provided with the charger, and more specifically, a scorotron charger having a shield case having an opening at a side end, and such a scorotron charger. The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile, as shown in FIG. 6, a photosensitive member 2 is charged by a charger 101, and light irradiation by an exposure means 3 is performed based on image information. To form an electrostatic latent image, which is developed by the developing roller 4 to form a toner image on the surface of the photoreceptor 2. This toner image is transferred to the transfer paper 5 using electrostatic force, and is fixed to the transfer paper 5 by heat and pressure by the transfer roller 6 to form an image. After the transfer is completed, the toner remaining on the surface of the photoconductor 2 is cleaned by the cleaning blade 7, and the surface of the photoconductor 2 is discharged by the charge removing lamp 8, thereby completing one cycle of the image forming process.

  As described above, the scorotron charger 101 is widely used as a charger for charging the photosensitive member 2. In the scorotron charger 101, a grid 113 is provided on the discharge opening surface of the shield case 112 on which the wire 111 is stretched, and the grid 113 is disposed close to the surface of the photosensitive member 2, and the potential difference between the wire 111 and the grid 113 is caused. Corona discharge is performed from the wire 111 through the grid 113 to charge the surface of the photoreceptor 2.

A large amount of ozone is generated by this corona discharge. Ozone has a very strong oxidizing power. If high-concentration ozone stays on the surface of the photosensitive member 2, the charging ability is lowered, it becomes difficult to carry the charge, and a problem such as a fogged image due to a decrease in surface potential occurs. In order to prevent this, a device has been devised so that ozone is not retained on the surface of the photosensitive member 2 near the charger 101 by providing a blower fan, a duct, or the like in the image forming apparatus and blowing air to the charger 101.
For example, a blower fan of a blower unit is provided with a blower system that excludes ozone from the charger 101 and blows it out to the photosensitive member 2, and wind speed control is performed to change the wind speed of air sent by the blower unit (Patent Document 1 below). reference).

  In addition, even if air is blown into the shield case, if the air flow is not blown uniformly in the longitudinal direction of the shield case, the discharge wire may be locally soiled or oxidized corresponding to the weak air flow portion. As a result, discharge partitioning occurs, and a partition wall is erected along the longitudinal direction of the shield case in the air duct, and the pressure of the air flow blown toward the shield case is temporarily suspended on the front side of the partition wall. (See Patent Document 2 below).

  However, the inside of the image forming apparatus is designed in a very dense state, and it is difficult to provide a duct or the like for guiding outside air to the charger as described above with sufficient size and performance so that ozone does not stay. . Even if a duct or the like can be provided with sufficient size and performance, the entire apparatus becomes large and the cost increases.

Also, in the scorotron charger, both ends in the length direction of the shield case made of steel material are made of plastic insulator, so the insulator walls are at the ends of the charger in the longitudinal direction. Thus, since the escape space of the air in the longitudinal direction is limited, the wind speed is weaker than the central portion of the charger, and the air flow is hindered, making it difficult for the air to be replaced. Therefore, as described above, even if the wind speed blown toward the shield case is changed or the pressure of the air flow is increased, it is not effective for air staying in the insulator part in the shield. Absent.
Therefore, there is a need for means for scavenging ozone in the vicinity of the charger, particularly near the insulator wall in the shield case, without increasing the size of the blower fan and duct and improving the performance.

Japanese Patent Laid-Open No. 2000-147962 JP-A-10-198128

  The present invention has been made to solve the above-described problems of the prior art, and without increasing the size of the blower fan and duct or improving the performance, in the vicinity of the charger, particularly in the shield case. A scorotron charger capable of scavenging ozone staying near an insulator wall and an image forming apparatus provided with the charger.

The invention according to claim 1 is a scorotron charger that includes a shield case, a discharge wire, a grid electrode, and an insulator for connecting them, and charges the photosensitive member.
The shield case is a side surface on the downstream side in the moving direction of the photosensitive member to be charged, the scavenging holes provided between the insulators provided at both ends of the charger and the openings of the grid electrode , An air intake port provided for taking in an air flow from a duct provided above is provided on a surface facing the discharge opening surface provided with the grid electrode, and the air is introduced into the shield case from the air intake port. The present invention relates to a scorotron charger characterized in that a flow flows in and the air flow exits from the scavenging holes .

  The invention according to claim 2 relates to the scorotron charger according to claim 1, wherein the scavenging hole has a circular shape on the side surface of the shield case.

  A third aspect of the present invention relates to an image forming apparatus comprising the scorotron charger according to the first or second aspect.

  According to the first aspect of the present invention, in the shield case, the side surface on the downstream side in the photosensitive member moving direction, between the insulator and the opening of the grid electrode, that is, between the insulator wall and the opening end. By providing a scavenging hole in the shield case, it stays in the vicinity of the scorotron charger, particularly near the insulator wall in the shield case, without increasing the size of the blower fan and duct that blows into the shield case or increasing the performance. Ozone can be discharged, thereby preventing exposure of the photoreceptor to ozone.

  According to the second aspect of the present invention, by providing the scavenging holes in a circular shape on the side surface of the shield case, it is possible to avoid the influence of the charge concentration on the corners such as the quadrangle and the triangle and the influence on the charging of the photoconductor. In addition, it can be processed relatively easily, and the cost can be reduced.

  According to the third aspect of the present invention, an image forming apparatus capable of preventing exposure of ozone to the photoconductor without increasing the size of the blower fan and the duct or improving the performance can be obtained. be able to.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a scorotron charger and an image forming apparatus including the charger according to the invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an image forming unit in an image forming apparatus including a scorotron charger according to an embodiment of the present invention. This configuration is the same as that of the image forming apparatus provided with the conventional scorotron charger 101. Further, the arrows in the figure indicate the rotation direction of the photosensitive member 2.
The image forming unit includes a photoreceptor 2, a scorotron charger 1 (hereinafter also referred to as a charger 1) as a charging unit, which is sequentially arranged around the photosensitive member 2 along the rotation direction, an exposure unit 3, and a developing unit. The developing roller 4, the transfer roller 6, the cleaning blade 7, and the charge removal lamp 8 are included.

  In the charger 1, a wire (discharge wire) 11 is stretched in a conductive shield case 12, and a grid (which controls the charging potential on the surface of the photoreceptor 2 over almost the entire discharge opening surface of the shield case 12). (Grid electrode) 13 is provided. The charger 1 is disposed so that the discharge opening surface faces the surface of the photoreceptor 2.

  In the image forming unit configured as described above, by applying a high voltage between the wire 11 of the charger 1 and the grid 13, corona discharge is performed on the surface of the photoreceptor 2 from the wire 11 through the grid 13. The surface of the photoreceptor 2 is charged. Next, an electrostatic latent image is formed by light irradiation by the exposure means 3 based on the image information, and this is developed by the developing roller 4 to form a toner image on the surface of the photoreceptor 2. This toner image is transferred to the transfer paper 5 using electrostatic force, and is fixed on the transfer paper 5 by heat and pressure by the transfer roller 6 to form an image. After the transfer is completed, the toner remaining on the surface of the photoconductor 2 is cleaned by the cleaning blade 7, and the surface of the photoconductor 2 is discharged by the charge removing lamp 8, thereby completing one cycle of the image forming process.

FIG. 2 is a state diagram showing a state in which outside air is blown to the scorotron charger provided in the image forming apparatus shown in FIG.
Above the charger 1, a resin duct 21 is provided to guide the air outside the apparatus to the charger 1, and a blower fan (not shown) serving as a blowing means is provided at the air inlet of the duct 21. . In the figure, the arrow in the duct 12 indicates the air flow direction. In the shield case 12, an air intake port for taking in an air flow from the duct 21 is provided on a surface facing the discharge opening surface provided with the grid 13. The air intake port is established by providing a plurality of openings along the extending direction of the wire 11 over a length substantially corresponding to the discharge opening surface. In addition, as the duct 21 and the blower fan in the present embodiment, those having a conventionally used size and performance can be adopted, and it is not necessary to have a large size and a good performance. It does not matter even if it is.

  In the charger 1 and the duct 21 configured as described above, when the corona discharge is performed from the wire 11 to charge the surface of the photoreceptor 2, the sending fan draws outside air and passes through the duct 21 to the top of the charger 1. Induces outside air. This air is taken into the shield case 12 from the air intake port of the charger 1 and escapes to the outside of the charger 1 through the gap between the side surface of the shield case 12 and the surface of the photoreceptor 2 together with the ozone generated in the charger 1. . The shield case 12 has two side surfaces located upstream and downstream in the rotation direction of the photosensitive member 2, and air that has entered the shield case 12 is excluded from the upstream side surface and the downstream side surface, respectively. It will be.

  Here, the grid 13 controls the voltage (about 6 kV) due to corona discharge from the wire 11 to make the charged potential of the surface of the photoreceptor 2 constant, so that about 95% of the discharge from the wire 11 is made of conductive metal. The grid voltage (about 470 to 480 V) is controlled so that only about 5% is emitted to the shield case 12 and discharged to the surface of the photoreceptor 2. In order to increase the amount of charge on the surface of the photoreceptor 2 while performing such voltage control, the charger 1 is brought closer to the photoreceptor 2. Therefore, the air excluded from the gap between the shield case 12 and the photoreceptor 2 is limited.

Further, as described above, the vicinity of the insulator wall obstructs the flow of air in the longitudinal direction in the shield case 12 and makes it difficult for the air to be replaced. If the generated ozone stays and the amount of ozone increases because the air is not replaced, the potential on the surface of the photoreceptor 2 is lowered, and in the worst case, both ends of the paper are blackened with toner and a fogged image is formed.
Therefore, in this embodiment, a hole is formed in the side surface of the shield case 12.

FIG. 3 is a side view schematically showing the downstream side surface of the charger according to the present invention. FIG. 4 is a partial perspective view showing a state where the grid of the charger according to the present invention is removed.
The charger 1 includes an insulator 31 at both ends, a shield case 12, wires 11, and a grid 13. An insulator wall 33, which is an end of the insulator portion 31 on the center side of the charger 1, is covered with a shield case 12 having a shield case end 32. A scavenging hole 37 is provided 43 between the insulator wall 33 and the opening end 34 of the grid 13. Between the two insulator walls 33 at both ends of the charger 1 is an inter-insulator 36. A space between the two opening ends 34 is a grid opening, and its length is an effective charging length 35.

  Thus, the scavenging hole 37 is provided on the downstream side surface of the shield case 12 between the insulator wall 33 and the opening end 34 of the grid 13 at a position that does not affect the charging of the photoconductor. In addition, the air inside the shield case 12, particularly the air near the insulator wall 33, is easily replaced.

  When a hole is made in the upstream side surface of the shield case 12, the light from the static elimination lamp disposed immediately upstream of the charger 1 enters the shield case 12, and the chargeability is significantly reduced. In other words, the light from the static elimination lamp hits the surface of the photoconductor in the shield case 12 and is in an exposed state, and the static electricity disappears to the part where there is no character or the like that should be charged, and the toner is attached. It affects the charging of the photoreceptor.

  Further, when a hole is made from the opening end 34 of the grid 13 to the center of the charger 1, as described above, about 95% of the corona discharge from the wire 11 needs to be escaped by the conductive metal shield case 12. At some point, the potential cannot be controlled by the hole, which affects the charging of the photoreceptor. Needless to say, even if a hole is formed in the end of the charger 1 from the insulator wall 33, that is, in the insulator 31, the air inside the shield case 12 does not contribute.

  The scavenging hole 37 is made as large as possible between the insulator wall 33 and the opening end 34 of the grid 13 in consideration of the ease of air exchange inside the shield case 12, particularly in the vicinity of the insulator wall 33. It is preferable to provide them. If the interval is 43, there is no effect on the charging of the photosensitive member. Therefore, the larger the air is, the easier it is to remove the air and the more easily the air is replaced. Two scavenging holes 37 can be provided in the vicinity of the insulator walls 33 at both ends of the charger 1. However, due to the structure of the actual charger 1, the two insulator walls 33 and the grid 13 are provided. The opening 43 is slightly different from the opening end 34, but it is preferable to provide each of them as large as possible.

  Moreover, as the shape of the scavenging hole 37, a round shape without corners is preferable and an elliptical shape may be used, but a circular shape is most preferable in consideration of ease of processing. A shape having a corner such as a square or a triangle is not preferable because electric charges concentrate on the corner.

  The size of the scavenging hole 37 can be, for example, 10 mm in diameter when the photoconductor having a diameter of 30 mm is provided with the charger 1 having a charger width of 12 mm, an insulator spacing of 360 mm, and an effective charging length of 320 mm.

  As described above, just by providing a scavenging hole between the insulator wall and the end of the opening on the side surface on the downstream side in the rotation direction of the photosensitive member, the blower fan and duct for blowing air into the shield case can be enlarged, and the performance can be improved. Without rising, ozone staying in the vicinity of the scorotron charger, particularly near the insulator wall in the shield case, can be discharged.

The scorotron charger 1 according to the present invention shown in FIGS. 3 and 4 was used as an example, and a scorotron charger not provided with the scavenging holes 37 was used as a comparative example, and the state of air exchange in the shield case 12 was confirmed. . As a confirmation method, two methods of visual confirmation of the airflow distribution state and ozone concentration measurement in the shield case 12 were adopted.
The scorotron charger of the comparative example is mounted on a commercially available copying machine KM-1620 (manufactured by Kyocera Mita Co., Ltd.), and the charger of the embodiment is a charger in which scavenging holes 37 are provided in the charger of the comparative example. As in the comparative example, it was mounted on the copying machine KM-1620. The blower fan and duct were used as they were without improvement.

(Example 1) Visual confirmation of airflow distribution status The charger 1 of Example 1 has a charger width of 12 mm, an insulator spacing of 360 mm, and an effective charging length of 320 mm, and the insulator wall 33 and the opening end 34 of the grid 13 are In the middle, as shown in FIG. 3, a circular scavenging hole 37 having a diameter of 10 mm is provided on the left side of the sheet, and is provided at the charging position of the photosensitive member having a diameter of 30 mm. Note that the airflow distribution was confirmed by visual observation from the state of adhering air mixed with fine silica, which was white powder, for example. In both Example 1 and Comparative Example 1, the charger was prepared at the charging position by removing the grid 13 as shown in FIG.

  The charging device configured as described above was provided in the copying machine, silica (particle size: 80 nm) was introduced from the blower fan into the duct, and the amount of silica adhering to the inner surface of the shield case 12 was visually confirmed. In the charger in which the scavenging hole 37 of Comparative Example 1 is not provided, almost no silica is adhered from the insulator wall 33 to the position of about 40 to 50 mm in the central direction of the charger, and the air flow at this position Was confirmed to be bad. On the other hand, in the charger 1 of Example 1, silica is attached to the inner surface of the shield case 12 from the position where the scavenging holes 37 are provided, that is, the position of about 10 mm from the insulator wall 33 toward the center of the charger 1. It was confirmed that there was an air flow up to this position, and the scavenging performance was improved by the scavenging holes 37.

Example 2 Ozone Concentration Measurement The charger 1 of Example 2 has a charger width of 12 mm, an insulator spacing of 360 mm, and an effective charging length of 320 mm, and between the insulator wall 33 and the opening end 34 of the grid 13. As shown in FIG. 3, two circular scavenging holes 37 having a diameter of 10 mm on the left side of the paper and 7 mm in diameter on the right side of the paper were provided and provided at the charging position of the photoreceptor having a diameter of 30 mm.
Using the copying machine including the charger 1 configured as described above, the ozone concentration in the shield case 12 was measured while continuing to blow air from the duct 21. The ozone concentration was measured by using an ozone concentration meter (EG-2001 manufactured by Sugawara Jitsugyo) and collecting air from the gap between the photosensitive member side opening of the shield case and the surface of the photosensitive member, and from the gap on the developing roller side. . A voltage of 5 kV was applied to the wire 11 of the charger 1 to continuously discharge 500 μA. When the ozone concentration reached saturation, the concentration was recorded.

  FIG. 5 is a graph showing the ozone concentration measurement results described above. The example in which the circular scavenging holes 37 of Example 2 are not provided is referred to as Comparative Example 2. There are three ozone concentration measurement positions, that is, the center position of the grid opening and the 140 mm position from the center to the left and right sides of the paper in FIG. 3, and the graph shows the 170 mm position, the 40 mm position, and the 300 mm position, respectively.

  As a result, as shown in FIG. 5, in both Example 2 and Comparative Example 2, a remarkable decrease in ozone concentration was observed at the center position, and at the positions of 40 mm and 300 mm, that is, at both ends of the grid 13, Markedly decreased ozone concentration, but the ozone concentration was still high in the comparative example. In the examples, the ozone concentration at the 300 mm position was higher than that at the 40 mm position because the scavenging holes 37 were set to 10 mm and 7 mm, respectively. It was shown that it becomes easy to change. It was confirmed that by providing the scavenging holes 37, the amount of ozone staying in the vicinity of the charger 1, particularly the insulator wall 33, can be sufficiently reduced.

  The present invention is suitably used for an image forming apparatus such as a copying machine, a printer, and a facsimile machine having a scorotron charger.

1 is a schematic configuration diagram illustrating an image forming unit in an image forming apparatus including a scorotron charger according to an embodiment of the present invention. FIG. 2 is a state diagram illustrating a state in which outside air is blown to a scorotron charger provided in the image forming apparatus illustrated in FIG. 1. It is a side view which simplifies and shows the downstream side surface of the charger which concerns on this invention. It is a fragmentary perspective view which shows the state which removed the grid of the charger which concerns on this invention. It is a graph which shows the ozone concentration measurement result in Example 2. It is a schematic block diagram which shows the image formation part in the image forming apparatus provided with the conventional scorotron type charger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scorotron type charger 12 Shield case 31 Insulator part 33 Insulator wall 37 Scavenging hole

Claims (3)

In a scorotron charger having a shield case, a discharge wire, a grid electrode, and an insulator for connecting them, and charging the photosensitive member,
The shield case is a side surface on the downstream side in the moving direction of the photosensitive member to be charged, the scavenging holes provided between the insulators provided at both ends of the charger and the openings of the grid electrode , An air intake port provided to take in an air flow on a surface opposite to the discharge opening surface provided with the grid electrode, and from the air intake port into the shield case with respect to the longitudinal direction of the shield case A scorotron-type charger characterized in that the air flow flows in substantially vertically and the air flow passes through the scavenging holes . The scorotron charger according to claim 1, wherein the scavenging hole has a circular shape on a side surface of the shield case.   An image forming apparatus comprising the scorotron charger according to claim 1.

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