JP2001307859A - Ion generator and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an impressed voltage for corona discharge, and enhance a discharge stability, and evade a life reduction of a corona discharge wire, and reduce longitudinal discharge dispersions. SOLUTION: In an ion generating device containing a case 23 having an opening wherein an electrode 21 is installed inside and produces ions by a high voltage discharge, the electrode 21 is characterized that it is composed of wires 21a+21b whose cross sectional shape is ellipse or oval and which are applied of plating treatment or carbon coating. After they are pressure rolled to form the ellipse or oval shape, the plating treatment or carbon coating is applied. The wires are twisted around a longitudinal shaft to form a spiral form.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ion generator comprising a discharger for generating ions by applying a high voltage to an electrode, and an image forming apparatus using the same.
This ion generator is a photoconductor charger (main charger) of an image forming apparatus such as a copying machine, a printer, and a facsimile, a static eliminator for adjusting a toner potential on the photoconductor, a transfer charger, a separation charger, and a static elimination of a photoconductor surface after toner transfer. It can be used for a static elimination charger or the like. Not only that, the present invention can be used for a charger or a static eliminator for adsorbing or separating fine particles or thin sheets, for example, for erasing an IC substrate.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus, such as a copying machine, a printer, and a facsimile machine, which charges a photosensitive member, forms an electrostatic latent image on a charged surface by exposure, and visualizes the electrostatic latent image with toner, employs a photosensitive member. A charger (main charger) for uniformly charging, a transfer unit (transfer charger) for transferring a toner image formed on a photoconductor to an image forming medium, and a static eliminator (static elimination charger) for removing residual charges from the photoconductor It has.

[0003] For example, a mainstream charging method for uniformly charging a photosensitive member is a method using corona discharge of a charger. According to this, a large amount of ozone is generated at the time of discharge, and a high voltage power supply of about 4 to 10 KV is required. Therefore, in recent years, a contact charging device has been put to practical use as an alternative charging method. This contact charging device is intended for low ozone and low power, and a conductive member such as a conductive roller, a conductive brush, or a conductive elastic blade is brought into contact with the surface of the image carrier, and the conductive member is electrically charged. A so-called contact charging system in which a voltage is applied to a member to charge an image carrier has been proposed (JP-A-56-14).
4453, JP-A-1-93762, etc.). Among these, a roller charging method using a conductive roller as the charging member is particularly preferably used from the viewpoint of charging stability. In the roller charging method, a conductive elastic roller is pressed against an object to be charged, and a voltage is applied thereto to charge the object.

[0004] However, recently, a new problem has arisen in the contact charging system (roller charging system). As a specific example, in a contact-type charging method using a high-resistance photoconductor, a small amount of ozone or NOx is generated, and the generated gas is generated very close to the photoconductor. There was a problem that the damage was large. In addition, in order to eliminate charging unevenness, it was necessary to apply an AC voltage to the conductive member. As specific examples, there are reported an image flow phenomenon which is considered to be caused by NOx adhering to the image carrier, and a phenomenon in which the CTL layer of the image carrier is easily scraped by direct discharge. Therefore, the corona charger is being reviewed again. However, in the conventional charging method using corona discharge, a large amount of ozone or NOx was generated due to a high applied voltage.

The corona charger disclosed in Japanese Patent Application Laid-Open No. 7-112004 attempts to reduce the applied voltage and obtain discharge stability by making the wire shape elliptical in cross section.
FIG. 3 shows a simulation result of the electric field intensity distribution around the charger wire 27. FIG. 3 shows the electric field intensity region where ozone is estimated to be generated by darkened portions (black) 28, where (a) shows one wire and (b) shows two wires. The case of is shown. As can be seen from these figures, the total area of the place 28 where the electric field strength is strong is:
There is almost no difference between one and two. In addition, FIG.
In the case of the two wires shown in (1), the electric field strength is weak at a place where the two wires are close, and a strong electric field is concentrated at a place away from the two wires.
It is assumed that the cross-sectional shape of one wire is substantially the same as that obtained by making the cross section into an ellipse or an ellipse. Therefore, when the cross-sectional shape is an ellipse or an ellipse, it is considered that a strong electric field is concentrated at a small radius of curvature at both ends of the long axis, thereby reducing applied voltage and stabilizing discharge.

However, since the usual wire material is tungsten and hard, when the cross-sectional shape is made to be elliptical or elliptical, for example, as shown in FIG. Discharge variation may occur.

[0007]

Since the conventional corona charger generates a large amount of ozone O ₃ and NOx, a structure is employed in which a filter is removed before being discharged to the outside of the image forming apparatus in consideration of the influence on the environment. Had become. Further, inside the image forming apparatus, a compound generated from nitrogen oxides reacts with moisture in the air and adheres to a photoconductor as an image carrier, causing a problem called image deletion. In addition, the durability of the image carrier has been reduced by vigorously cleaning the image carrier in order to prevent the occurrence of the image flow or to remove the image flow. When the cross-sectional shape of the wire is made elliptical or elliptical, it is expected that the discharge voltage will decrease and the generation of ozone O ₃ and NOx will decrease, but the wire will crack when the wire is made elliptical or elliptical. In this case, discharge variations occur, and durability becomes a problem.

SUMMARY OF THE INVENTION It is a first object of the present invention to reduce the applied voltage for corona discharge and enhance the discharge stability, and to reduce the life variation of the corona discharge wire and reduce the discharge variation in the longitudinal direction. This is the second purpose.

[0009]

(1) In an ion generator including a case (23) having an opening and an electrode installed inside the case and generating ions by high-voltage discharge, the electrode has an oval cross section. Alternatively, the ion generator is an elliptical, plated wire (21).

[0010] In order to facilitate understanding, the reference numerals of the corresponding elements of the embodiment shown in the drawings and described later are added for reference in parentheses. The same applies to the following.

According to this, since the wire (21) is an ellipse or an ellipse, the radius of curvature of the curved surfaces at both ends of the major axis is smaller than that of a perfect circle having the same cross-sectional area, and the curved surfaces at both ends of the minor axis are smaller. , The electric field is concentrated on the curved surfaces at both ends of the long axis, and a stable corona discharge is generated at an applied voltage lower than that in the case of a perfect circle. Therefore, generation of ozone O ₃ and NOx is reduced. Even if a crack (for example, 29d in FIG. 4) is formed when the wire is processed into an ellipse or an ellipse, the plating layer fills the crack. Dispersion in the direction of discharge does not occur particularly.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (2) The metal wire 21 has a cross section of a perfect circle or a substantially perfect circle. It was done. According to this, since the surface roughness and micro-cracks generated at the time of rolling are covered with the plating layer and buried, the wire surface is smooth, so that there is no particular variation in the discharge in the longitudinal direction.

(3) In an ion generator including a case (23) having an opening and an electrode installed inside the case and generating ions by high-voltage discharge, the electrode has a carbon coating having an elliptical or elliptical cross section. An ion generator characterized by being a treated wire.

According to this, since the wire is an ellipse or an ellipse, it is more effective than a case of a perfect circle having the same cross-sectional area.
The radius of curvature of the curved surface at both ends of the long axis is small, the radius of curvature of the curved surface at both ends of the short axis is large, the electric field is concentrated on the curved surface at both ends of the long axis, and a stable corona discharge can be performed with an applied voltage lower than that of a perfect circle. appear. Therefore, generation of ozone O ₃ and NOx is reduced. Even if a crack (for example, 29d in FIG. 4) is formed when the wire is processed into an ellipse or an ellipse, the carbon coating fills the crack. Dispersion in the direction of discharge does not occur particularly.

(4) The wire of the above (3) is obtained by subjecting a metal wire having a perfect circle or substantially perfect circle in cross section to an ellipse or ellipse by crushing the perfect circle by rolling, and then performing a carbon coating treatment. It is. According to this, surface roughness and micro cracks generated during rolling are covered with carbon coating and buried,
Since the surface of the wire is smooth, there is no particular variation in discharge in the longitudinal direction.

(5) The wire is twisted around its longitudinal axis. According to this, since a curved surface having a small radius of curvature at the long axis end of an ellipse or an ellipse is distributed spirally around the longitudinal axis of the wire, the distortion of the electric field is further increased and the electric field is uniformly distributed in the longitudinal direction. Therefore, it is possible to further reduce the discharge starting voltage and achieve uniformity of the discharge in the longitudinal direction.

(6) The photoreceptor (1), the ion generator (2) according to any one of the above (1) to (5), wherein the opening faces the photoreceptor, and the ion generator of the photoreceptor. Exposure means for forming an electrostatic latent image on a charged surface by exposure
(3), and means (4) for developing the electrostatic latent image into a visible image,
An image forming apparatus comprising:

According to this, the voltage applied to the corona discharge of the ion generator (2) can be lowered to reduce the generation of ozone O ₃ and NOx. The generation of nitrogen oxide compounds can be reduced, and the occurrence of image deletion can be reduced.

(7) It is arranged to face the image carrier (1),
In a charging device having at least the wire (21) and applying a high voltage to the wire to generate ions or electrons to charge the image carrier, the cross-sectional shape of the wire is made oval or elliptical. A charging device (2), wherein the wire surface is plated.

(8) It is arranged to face the image carrier (1),
In a charging device having at least a wire and applying a high voltage to the wire to generate ions or electrons to charge the image carrier, a cross-sectional shape of the wire is formed into an ellipse or an ellipse, and carbon is formed on the surface. A charging device, which has been subjected to a coating process.

(9) The charging device according to (7) or (8), wherein the wire (21) is twisted around its longitudinal axis.

(10) The gas (O) generated from the charging device by having the charging device according to any one of (1) to (3) above.
_3. An image forming apparatus characterized in that it prevents NOx) from adhering to the image carrier (1).

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0024]

FIG. 1 is a schematic diagram showing an example of an image forming apparatus provided with a charging device 2 which is an ion generator according to an embodiment of the present invention. The image forming apparatus of this example is a printer using a transfer type electrophotographic process or a printer unit of a copying machine.

Reference numeral 1 denotes an image carrier as a member to be charged. This embodiment is an electrophotographic OPC photoreceptor of a negative polarity and a rotating drum type having a diameter of 30 mm and a length of 340 mm, and is rotated in the clockwise direction of an arrow at a process speed (peripheral speed) of 125 mm / sec.

The charging device 2 is a corona charger 2 disposed opposite to the photoconductor 1, and applies a high voltage to the charge wire 21 to generate a discharge phenomenon to charge the OPC photoconductor. Normally, a grid 22 is arranged between the charge wire 21 and the photoconductor 1, so that more uniform charging can be performed. 21 PS is a charging bias application power supply for supplying power to the corona charger 2. In this embodiment, a predetermined charging bias is applied to the charge wire 21 from the power supply 21PS to uniformly charge the peripheral surface of the rotary photoconductor 1 to a surface potential of -960V.

The charged surface of the rotary photoreceptor 1 is subjected to laser beam scanning exposure of image information by the image exposing device 3 to form an electrostatic latent image corresponding to the exposed image information on the surface of the rotary photoreceptor 1. Is done. Next, the electrostatic latent image is stored in the developing device 4.
, The toner is attached, and the toner image is sequentially visualized as a toner image. The developing device 4 of the present embodiment is a two-component contact developing system, in which a rotating developing sleeve 41 as a developer carrying member is disposed at a distance of 0.6 mm from the photoconductor 1, and a power source 42 is connected to the developing sleeve 41. Therefore, a developing bias from a DC power supply of -600 V is applied. Further, a minus toner was used as the toner. Here, the two-component developing device 4
However, there is no problem even if another two-component developing device or one-component developing device is used.

On the other hand, a transfer paper 7
Is transported to a transfer portion, which is a contact nip portion between the photoconductor 1 and the transfer roller 5, at an appropriate timing synchronized with the rotation of the photoconductor 1, and is nipped and transported by the transfer portion. The transfer paper 7 which is nipped and conveyed by the power supply 51 to the transfer roller 5 from the power supply 51.
A predetermined transfer bias having a polarity opposite to that of the upper toner is applied. As a result, the reverse side of the transfer paper 7 is charged to the opposite polarity to the toner, and the toner images on the photoconductor 1 are sequentially electrostatically transferred to the front surface of the transfer paper 7. In the present example, a conductive sponge roller having a resistance of 5 × 10 ⁷ Ω and a diameter of 16 mm was used as the transfer roller 5, and a DC voltage was applied by constant current control to perform transfer.

Transfer material 7 on which a toner image has been transferred at the transfer section
Is separated from the surface of the photoreceptor 1 and is conveyed to the fixing device 9 where the toner image is fixed and then discharged to the outside of the apparatus main body. The sheet is re-conveyed to the transfer unit by the conveying unit.

On the other hand, the transfer residual toner remaining on the photoreceptor is peeled off from the photoreceptor 1 by the blade 61 of the cleaning device 6 and stored in the cleaning device 6. After that, those which are returned to the developing unit again are often seen in recent image forming apparatuses, and the image forming apparatus of the present embodiment has such a structure although not shown.

FIG. 2A is an enlarged view of the charger 2 with a part thereof cut away. The arrow x indicates the direction from the front cover side of the printer to the back side, the longitudinal direction in which the discharge wire 21 serving as the discharge electrode of the charger 2 extends, z indicates the upward direction, and y indicates the tangential direction of the photoconductor 1. FIG. 2 (a)
2 shows the charger 2 with its front side broken along the y, z plane and its back side cut away. The front end block 26
And a not-shown rear end block are integrally fixed to a shield case 23 made of a metal material, and a discharge wire 21 is stretched between the two end blocks. An opening is provided at the lower end of the shield case 23, and the grid electrode 2
There are two. Reference numerals 24 and 25 denote side plates of the shield case 23.

FIG. 2B is an enlarged cross-sectional view of the discharge wire 21. The discharge wire 21 has a short axis length of about 40 by rolling a substantially circular metal wire 21a having a diameter of about 60 μm.
μm, about 80 μm in major axis length, crushed into an ellipse, and plated with a metal coating 21b. As shown in FIG. 2 (c), it may be rolled into an ellipse and plated. In order to obtain the same strength as that of a conventional substantially circular charger wire having a diameter of approximately 60 μm, the size of the elliptical or oval shape may be about 40 × 80 μm. There is no particular problem if the material of the plating process is conductive, but gold (Au)
Alternatively, platinum (Pt) is preferable in terms of discharge stability and the like.

In another embodiment, a carbon coating process is performed instead of or in addition to the plating process. In one example, a carbon alloy layer, known as the carbon coating of a deposited carbon film resistor,
It is formed on the surface of the metal wire 21a by the thermal decomposition deposition process.

By the plating coating or the carbon coating 21b, it is possible to suppress the variation of the discharge and to improve the durability of the wire. The carbon coating treatment is preferred from the viewpoint of the durability of the coating surface and the like. In addition, in order to obtain the same strength as that of a conventional φ60 μm bare wire, the size of the ellipse or ellipse is about 40 × 80.
About μm is preferable for recording an A3 width (about 300 mm).

As described above, assuming a wire having the same strength as the conventional bare wire of φ60 μm, it is assumed that ozone is generated because the radius of curvature is reduced by making the cross-sectional shape elliptical or elliptical. The electric field intensity region can be made smaller, and as a result, the amount of ozone and NOx generated can be reduced. Further, as for the elliptical shape, it goes without saying that the smaller the radius of curvature of the major axis end is, the lower the firing voltage can be.

Since the wire diameter is small, the shield case 2
Since it is difficult to make the major axis of the cross-sectional shape of the charger wire 21 parallel to the y-axis (or the z-axis) over the entire length of the charger wire 3, as shown in FIG.
1 is preferably spirally wound around its longitudinal axis and stretched over the shield case 23. According to this, not only the distribution form of the cross-sectional shape of the charger wire 21 is homogenized over the entire length of the shield case 23, so that the tensioning operation of the charger wire 21 is simplified, but also the distortion of the electric field becomes larger, and the discharge starts. The voltage can be further reduced.

Conventionally, tungsten is usually used as the wire material. However, in the present invention, since the coating is performed by plating or carbon coating, it is not necessary to use tungsten. Can be used.

In this embodiment, the charger 2 has a grid 2
2 is provided. The ions or electrons generated in the vicinity of the wire 21 move toward the rotating photoreceptor 1 serving as an image carrier by an electric force. At this time, some electrons disappear and others collide with molecules to form new ions. When the surface potential of the photoconductor 1 reaches the voltage applied to the grid 22 by the movement of ions or electrons, the ions or electrons stop receiving an electric force from the surface of the photoconductor 1, The potential difference is drawn to the grid 22 and the casing 23 of the charger 2 where the potential difference exists. Therefore, the surface of the photoreceptor 1 is charged to a voltage substantially equal to the voltage applied to the grid 22, and the grid 22 has an effect that the voltage is not increased any more. Therefore, the charging potential of the photoconductor can be controlled by the voltage applied to the grid 22. If the cracked wire 29 is used, the grid is required to make the charged potential of the photoconductor uniform. In this embodiment, since the wire 21 coated with plating or carbon is used, the charged potential of the photosensitive member becomes uniform, and therefore, the grid can be omitted in this sense. However, a grid 22 is provided to control the charging potential of the photoconductor.

According to the embodiment described above, the amount of ozone and NOx generated can be reduced as compared with the conventional perfect circular wire.
It is possible to prevent the adverse effects of the discharge products on the image carrier and the like, and to suppress the adverse effects on the environment. Adhesion of nitric acid or nitrate, which is one of the discharge products, to the surface of the photoreceptor is suppressed, and image deletion (abnormal image generation) on the photoreceptor can be suppressed. By performing plating or carbon coating on the wire, there is no variation in discharge, and the durability of the wire is improved. The cleaning blade 61 does not need to scrape off the surface of the photoconductor, and the reduction of the pressing pressure slows down the deterioration of the photoconductor 1 and the blade 61, thereby extending the life. Elimination of toner sticking to the photoreceptor caused by the high pressing pressure is eliminated. Further, the amount of abrasion of the photoreceptor film over time is reduced, and the process control load is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a printer equipped with an ion generator according to one embodiment of the present invention.

2A is an enlarged perspective view showing a part of the charger 2 shown in FIG. 1 with a part cut away, FIG. 2B is an enlarged cross-sectional view of a charger wire 21 shown in FIG. 2A, and FIG. FIG. 9D is an enlarged cross-sectional view of a charger wire 21 of a modified example, and FIG.

3A and 3B are simulation cross-sectional views showing a distribution of a strong electric field 28 around a conventional bare wire 27, wherein FIG. 3A shows a case of one wire, and FIG. 3B shows a case of two wires.

FIG. 4 is an enlarged cross-sectional view showing a crack 29d which may occur when a conventional tungsten wire having a perfect circular cross section is crushed into an ellipse or an ellipse by rolling.

[Explanation of symbols]

 1: rotating photoconductor 2: charger 21: wire 21PS: charging power supply 21a: metal wire 21b: plating layer 22: grid 23: shield case 24, 25: side plate 26: end block 27: metal wire 28: strong electric field 29: metal Wire 29d: crack 3: image exposure device 4: developing device 41: developing roller 42: developing bias power supply 5: transfer roller 51: transfer power supply 6: cleaning device 61: cleaning blade 7: transfer paper 9: fixing roller

Claims (6)

[Claims] 1. An ion generating apparatus including a case having an opening and an electrode installed inside the case and generating ions by high-voltage discharge, wherein the electrode has a cross-sectional shape of an ellipse or an ellipse and is a plated wire. An ion generator characterized by the following. 2. The metal wire according to claim 1, wherein the metal wire has a cross section of a perfect circle or a substantially perfect circle, and is subjected to a plating process after crushing the perfect circle by rolling to form an ellipse or an ellipse. An ion generator according to any one of the preceding claims. 3. An ion generating apparatus including a case having an opening and an electrode installed in the case and generating ions by high-voltage discharge, wherein the electrode is subjected to a carbon coating treatment whose cross section is an ellipse or an ellipse. An ion generator characterized by being a wire. 4. The wire according to claim 1, wherein a metal wire having a cross section of a perfect circle or a substantially perfect circle is subjected to a carbon coating treatment after the perfect circle is crushed into an ellipse or an ellipse by rolling. 2. The ion generator according to 1. 5. The ion generator according to claim 1, wherein said wire is twisted around its longitudinal axis. 6. A photoconductor, wherein the opening faces the photoconductor.
6. An ion generating apparatus according to claim 1, wherein said exposure means forms an electrostatic latent image on a surface of said photoconductor charged by said ion generator by exposure, and said electrostatic latent image is visible. An image forming apparatus comprising: means for developing an image.