JP3319045B2 - Corona discharge 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 electrophotographic copying machine,
The present invention relates to a corona discharge device used for an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, an electrostatic latent image carrier, such as a photosensitive drum, is charged to uniformly charge the surface thereof prior to forming an electrostatic latent image corresponding to an original image. A corona discharge device as a charger, a transfer charger for transferring a toner image obtained by developing an electrostatic latent image to transfer paper, a separation charger for separating transfer paper after transfer of a toner image from an electrostatic latent image carrier, and the like Is widely used.

The corona discharge device usually employs a wire electrode continuously extending along the charged member as a discharge electrode. Recently, a DC corona discharge device as a charging charger employing a sawtooth electrode instead of a wire electrode has also been proposed (for example, Japanese Patent Laid-Open No. 5-19591).

[0004]

However, in the corona discharge device of the wire electrode type, most of the high voltage energy for discharge applied to the wire is consumed for ozone generation, and a large amount of ozone is generated during discharge. There is a problem of doing. When the ozone concentration is high, products oxidized by ozone (NOx) and the like adhere to the surface of the electrostatic latent image carrier such as a photosensitive drum, and the electric resistance of the surface of the electrostatic latent image carrier decreases, resulting in an electric charge. The movement of the (electrostatic latent image) causes a so-called image deletion.

[0005] Therefore, to set an exhaust fan and an ozone filter conventionally, but so as to eliminate such discharge products of ozone and the product from the image forming apparatus, apparatus with increasing recently <br/> Environmental Protection Discharge products discharged to the outside have been regarded as a problem. In particular, the blue angel mark permission standards for safety labeling in Japan and European countries, and the UL safety standard in the United States
According to the standard, the amount of ozone emitted from a copying machine or the like is limited. In this regard, in the DC corona discharge device using the above-described electrode having the sawtooth electrode, the amount of generated ozone is reduced to about 1/3 to 1/4 as compared with the device using the wire electrode.

However, in the discharge using a needle-shaped electrode such as a saw-tooth electrode, a charge is given to a charged member by a plurality of discharge points, so that the distance between the discharge points and the distance between the discharge point and the charged member are properly adjusted. If it is not set, the charge cannot be uniformly applied to the charged member. That is, when the interval (pitch) between the discharge points is small, electric fields between adjacent discharge points interfere with each other, causing uneven discharge. When the pitch is large, the discharge voltage is remarkable in the vicinity of the discharge point and in a portion other than the discharge point. Since they differ, uneven discharge occurs. In addition, if the distance (gap) between the discharge point and the charged member is small, electric charge is locally applied to the charged member, causing uneven discharge. If the gap is large, the power supply voltage for discharging must be increased. In addition, the size of the device is increased.

Accordingly, the present invention provides a corona discharge device used in an electrophotographic image forming apparatus, wherein the corona discharge device generates a small amount of ozone and can uniformly apply a charge to a charged member. Make it an issue.

[0008]

Means for Solving the Problems The inventors of the present invention have repeatedly studied to solve the above-mentioned problems. As a result, in order to suppress the generation of ozone, a discharge member having a plurality of sharp discharge ends such as a sawtooth electrode is employed. In some cases, uneven discharge can be suppressed,
The present invention was completed by finding out the correlation between the discharge end pitch and the discharge end-charged member gap without causing an increase in the size of the device.

That is, the present invention provides the following first and second corona discharge devices. (1) A corona discharge device in the image forming apparatus of the first corona discharge equipment electronic photographic method includes a discharge member having a plurality of sharp-shaped discharge end is arranged in a row, the discharge end and the image forming The gap distance D (mm) between the charged member or the moving trajectory of the charged member in the device and the pitch P (mm) of the discharge end are set to 2 ≦ D / P ≦ 8, and the discharge member is made of iron. A corona discharge device formed of an alloy containing 16 to 20% of chromium and 8 to 15% of nickel. (2) Second corona discharge device A corona discharge device in an electrophotographic image forming apparatus, comprising: a discharge member in which a plurality of sharp discharge ends are arranged in a line; A gap distance D (mm) between the charged member and the moving orbit of the charged member and a pitch P (mm) of the discharge end are set to 2 ≦ D / P ≦ 8, and the discharge end is made of a dielectric material. A corona discharge device characterized by being coated with a corona discharger.

The distance D is the distance between the charged member and the discharge end when the charged member is at a fixed position such as an electrostatic latent image carrier, and the charged member is the transfer paper. In the case where the charged member arrives as needed, the distance between the moving orbit of the charged member and the discharge end. Even if the value of D / P is smaller than 2 or larger than 8, uneven discharge which cannot be ignored in practical use occurs.

[0011] Discharge members having a sharp discharge end include:
In addition to the sawtooth discharge member as in the embodiment shown in FIG. 1, a razor-shaped discharge end a and a wire discharge end b are provided as shown in FIGS. 2A to 2C. It is also conceivable to use one having a needle-like discharge end c.

[0012]

In each of the first and second corona discharge devices of the present invention, the sharp discharge end of the discharge member is directed toward the charged member, and the condition of 2 ≦ D / P ≦ 8 with respect to the discharge end pitch P is satisfied. And a discharge voltage is applied to the discharge member, thereby generating a corona discharge and uniformly charging the charged member. Departure
According to the first corona discharge device of Ming, since the discharge member is formed of an alloy containing 16% to 20% of chromium and 8% to 15% of nickel in iron, corrosion resistance and heat resistance are improved. Therefore, oxidation can be suppressed, and adhesion of fine dust can be suppressed, whereby durability can be provided and discharge stability can be achieved. In order to further improve heat resistance and corrosion resistance, the alloy may contain molybdenum. Further, according to the second corona discharge device of the present invention, since the discharge end is covered with the dielectric material, the amount of ozone generated can be reduced accordingly, and the durability and discharge stability can be improved. First and second embodiments of the present invention
In any of the corona discharge devices described above, a discharge voltage including an AC voltage component having a frequency of 400 Hz or more and 1.5 kHz or less may be applied to the discharge member. By doing so, it is possible to further reduce the amount of generated ozone and improve discharge stability. The frequency of the AC voltage component of the applied discharge voltage is 400 Hz or more and 1.5 kHz.
Although it is not more than z, the higher the value is, the smaller the ozone generation amount is, but the higher the frequency is, the higher the leakage current is.
Further, any one of the first and second corona discharge devices of the present invention.
Also, the sharp discharge end of the discharge member has a sawtooth shape,
The tooth angle of the saw tooth is 5 ° or more and 30 ° or less, and the thickness of the saw tooth is approximately 0.
It may be set to 05 mm. By doing so,
Excellent in workability and strength while suppressing the amount of generated zon
It is.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a perspective view of a corona discharge device 10 according to one embodiment, and FIG. 1B is a partially enlarged perspective view of the discharge member. The discharge device 10 includes a discharge member 1 and a discharge power supply 4 connected to the discharge member 1. This discharge device is incorporated in an electrophotographic image forming apparatus, and is used, for example, to charge the surface of the photosensitive drum PC prior to forming an electrostatic latent image.

The discharge member 1 is a charged member (photosensitive drum PC in the illustrated example) with a sharp discharge end 11 at a constant pitch P.
They are arranged in a certain direction along the surface, and have a sawtooth shape as a whole. Each discharge end 11 is located at the tip of a triangular sawtooth portion 12, from which corona discharge occurs. Such a saw-tooth discharge member can be easily obtained by, for example, etching a plate made of a conductive material or rolling and pressing. In addition, in addition to the sawtooth-shaped discharge member, as shown in FIG. 2A to FIG. 2C, those having a razor-shaped discharge end a, those having a wire discharge end b, and those having a needle-shaped discharge end One having an end c is also conceivable.

The pitch P of the discharge end 11 is not preferably too large or too small in order to suppress uneven discharge and stabilize discharge. On the other hand, if the distance D between the charged member and the discharge end 11 is too short, electric charge is locally applied to the charged member, so that there is a problem that charging cannot be performed uniformly or abnormal discharge occurs. There are problems such as an increase in power supply voltage and an increase in the size of the discharge device.

In order to uniformly apply charges to the charged object, the relationship between the pitch P (mm) and the distance D (mm) between the charged member and the discharge end must satisfy the condition of 2 ≦ D / P ≦ 8. Set to a range that satisfies. Each saw tooth portion 1 shown in FIG.
2 is set to 30 ° or less because the amount of ozone generated increases as the tooth angle becomes larger.
Since a problem arises in strength, the angle is set to 5 ° or more and 15 ° or less.

The thickness t of the sawtooth portion 12 is less than 0.1 mm, preferably 0.05 m, since the ozone generation amount decreases as the thickness decreases, but the strength is insufficient if the thickness is too small.
m. The discharge member 1, particularly the portion including the discharge end 11, is oxidized by performing corona discharge, and fine dust adheres thereto, which causes uneven discharge. Therefore, the oxidation is suppressed to suppress fine dust adhesion. Make it durable,
It is desirable to stabilize the discharge. Since this improvement in durability can be achieved by improving the corrosion resistance and heat resistance, the conductive material forming the discharge member 1 is preferably an alloy containing chromium and nickel in iron from the viewpoint of heat resistance and corrosion resistance. Molybdenum may be included to further improve heat resistance and corrosion resistance. Cr16 in terms of material component ratio
-20 (%), more preferably 16-18 (%), Ni
8 to 15 (%), more preferably 10 to 14 (%) is contained. If these are added too much, the tensile strength and hardness are impaired and the production cost is increased. When molybdenum (Mo) is included, it is contained in an amount of about 2 to 3 (%). If too much is added, the electric resistance value increases and burdens the power supply. In addition, as the discharge member, a member obtained by subjecting a conductive base material such as a copper plate to a corrosion-resistant treatment such as nickel plating may be considered.

Further, as shown in FIG. 1C, the discharge member 1, particularly at least the discharge end 11 portion (the discharge end or a portion including the discharge end), is reduced in the amount of generated ozone, improved in durability, and discharged. For the purpose of improving stability, it may be covered with a material 13 having a high electrical resistance (for example, a dielectric material such as ceramics). Such a dielectric material is preferably a ceramic material, among which glass, silicon oxide (SiO ₂ ),
Silica, silica-alumina, alumina and the like are preferred. The coating thickness is set to 0.1 mm or less, preferably 0.01 mm or less, because if the coating thickness is too large, the dielectric voltage increases and sparks are likely to occur.

In forming such a coating film, vapor deposition, material application, covering of a tube material, and the like can be appropriately employed. Even when the shape of the discharge end is as shown in FIG. 2, the same effect can be obtained by coating at least the discharge end portion with an electrically high-resistance material 19 as shown in FIG.

The power supply 4 connected to the discharge member 1 is capable of applying a discharge voltage including at least an AC voltage component for the purpose of reducing the amount of generated ozone and improving discharge stability. The higher the frequency of the applied AC voltage, the lower the amount of ozone generated. However, the higher the frequency, the higher the leakage current.
The following is assumed. The ozone generation amount decreases as the sum of the components on the plus side and the minus side of the discharge current becomes closer to zero. Therefore, the sum of the current components is in the range of −200 μA to +100 μA.

The discharge member 1 described above is supported by the holding member 2 and is disposed between the stabilizers 3 on both sides extending in parallel with the discharge member 1. Holding member 2 and stabilizer 3
Are both supported by the ceiling stabilizer 30. In addition, if both ends of the holding member 1 are held like a conventional wire electrode, the holding member 2 can be omitted. The stabilizer 3 is not always required. Even if it is provided, it does not matter whether or not it is conductive. However, in order to stabilize the discharge, it is better to be formed from a conductive material. Further, a grid (not shown) may be provided between the charged member and the discharge member 1 on the open side of the stabilizers 3 to stabilize the discharge.

According to the corona discharge device 10 described above, the discharge end 11 rows of the discharge member 1 are arranged toward the charged member (the surface of the photosensitive drum PC in the illustrated example). At this time, the distance Dmm between the discharge end row and the surface of the drum PC is 2 ≦
It is set so as to satisfy the condition of D / P (discharge end pitch mm) ≦ 8. A discharge voltage including at least an AC voltage component is applied from the discharge power supply 4 to the discharge member 1, whereby a corona discharge occurs, and the surface of the photosensitive drum PC is charged.

In this discharge and drum charging, the voltage for discharge contains an AC voltage component, so that the generation of ozone is suppressed as compared with a conventional saw-tooth electrode in which only a DC voltage is applied. Further, since the apparatus setting is performed under the condition of 2 ≦ D / P ≦ 8, the surface of the photosensitive drum is uniformly charged. When the discharge end of the discharge member 1 is formed of a conductive material containing nickel and chromium or molybdenum, oxidation of the discharge end is suppressed by the nickel and the like, and the discharge end is electrically connected. Even when coated with a high-resistance material, the oxidation of the discharge end is thereby suppressed, so that the adhesion of fine dust is suppressed for a long time, and a stable discharge is performed. When the discharge end is covered with the electrically high-resistance material 13 (see FIG. 1C), generation of ozone during discharge is suppressed accordingly.

Various experimental examples and the like that support the effects of the embodiment of the present invention described above will be sequentially described.・ About the material of the discharge member 1 Observe the amount of fine dust adhering to the discharge end after discharging for 100 hours using the discharge members 1, 1, 1 manufactured by changing the material components, and evaluate the durability by an electron microscope. did.

Discharge member 1 main material-iron (95% or more) Discharge member 1 main material-iron + chromium (18%) + nickel (10%) Discharge member 1 main material-iron + chromium (18%) + nickel ( 10%) + molybdenum (2%) FIG. 4 is a view based on an electron micrograph showing a state of a discharge end portion after discharging for 100 hours by the discharge member 1, and a large amount of fine dust adheres to the electrode surface. FIG. 5 is a diagram based on an electron micrograph showing an initial state before the discharge of the discharge member 1, and there is almost no deposit. FIG. 6 is a diagram based on an electron micrograph showing the state of the same member 1 after discharging for 100 hours. Fine dust adheres to the electrode surface, but the amount is smaller than in the case of the discharge member 1. FIG. 7 is a view based on an electron micrograph after 100 hours of discharge by the discharge member 1, and fine dust adheres to the electrode surface, but the amount of adhesion is smaller than in the case of the discharge member 1.

From the above results, it can be seen that the amount of fine dust adhering to the discharge end is reduced by forming the discharge member, especially the discharge end thereof, with a conductive material containing chromium and nickel. That is, the durability is improved. Further, it can be seen that the durability is further improved by containing molybdenum. FIG. 8 is a graph showing measurement results of a discharge current flowing from each part in the longitudinal direction of the discharge member 1 made of an iron material to the charged member side. FIG. 9 is a graph showing a discharge made of a material containing nickel, chromium, and molybdenum in iron. 6 is a graph showing measurement results of a discharge current flowing from each part in the longitudinal direction of the member 1 to the charged member side.

FIG. 8 shows that in the discharge member 1, considerable "unevenness" occurs in the discharge current at each portion in the longitudinal direction of the member. Further, from FIG. 9, it can be seen that, in the discharge member 1, the discharge current is more uniformly distributed in each portion in the member longitudinal direction than in the member 1. The tooth angle θ of the sawtooth portion 12 of the discharge member 1, the discharge end pitch P, the distance D between charged members, and the like.

In a corona discharge device using a discharge member having a sharp discharge end, the shape of the discharge end, the shape of the stabilizing plate, and the like greatly affect discharge stability (in other words, discharge unevenness) and the amount of ozone generated. Hereinafter, the relationship between the tooth angle θ of the sawtooth portion 12 of the discharge member 1, the discharge end pitch P, the distance D to the charged member, and the like, and the discharge stability and the amount of ozone generation will be described. Regarding the “discharge unevenness”, the discharge current flowing from each discharge end in the longitudinal direction of the electrode to the charged member side during corona discharge is detected, and if the detected current amount varies along the longitudinal direction of the electrode, the discharge current is detected. And Note that the discharge unevenness corresponds to image noise at the time of collecting an image sample.

The amount of generated ozone was measured by an ozone measuring device 90 shown in FIG. That is, the duct 9
1, the corona discharge device 10 is put into the duct 1, and a fan 92 blows air into the duct 91 to apply a high DC voltage to the discharge device 10. The air after passing through the discharge device 10 in the duct 91 was measured by the ozone concentration meter 93 to determine the amount of ozone generated. Tooth Angle θ and Ozone Generation The following were prepared as the discharge member 1. That is, iron,
Each of the two types of materials, a material X made of chromium and nickel and a material Y made of iron, chromium, nickel and molybdenum, has a constant plate thickness of 0.05 mm and a discharge end pitch of 1 mm, 2 mm, and 4 mm. Each one or a part thereof was prepared by changing the tooth angle θ. Each of these discharge members was housed in the ozone measuring device 90, and the amount of generated ozone was examined. At this time, the apparatus 90 has a diameter of the duct 91 of 50 mm, a wind speed of 2 m / sec, a low temperature and low humidity environment (20 ° C., 34% RH), and a discharge current Ic = −800 μA.
And The results are as shown in FIG.

As can be seen from FIG. 11, the ozone generation amount generally decreases as the tooth angle θ decreases. FIG.
Is a type of a corona discharge device 10 which uses an ozone filter with a removal rate of 70% in a copying machine and charges the photosensitive drum, transfers a toner image to a transfer paper, and separates the transfer paper from the photosensitive drum after the transfer. FIG. 6 is a diagram showing the relationship between the discharge end tooth angle θ and the amount of generated ozone, and the relationship between the discharge member strength and the discharge end tooth angle when the above-mentioned material is used. As can be seen from FIG. 12, also in this case, the ozone generation amount decreases as the tooth angle θ decreases.

The details of the experiment at this time are as follows. When the tooth angle is 15 °, the ozone concentration after purification by the ozone filter is suppressed to 0.1 ppm which can meet the UL standard. It was confirmed that it was possible. The basic configuration of each discharge device uses a sawtooth discharge member 1 as shown in FIG.

Discharge device for charging: Scorotron charge (discharge current -400 μA). Discharge device for transfer: corotron charger (discharge current −
75 μA). Discharge device for separation: corotron charger (discharge current ±
50 μA). The ozone concentration is set at 27 m ³ according to the UL standard.
The temperature was measured by operating the copying machine until the ozone concentration was saturated.

The measurement results of the ozone concentration were as follows (see FIG. 12). As shown in the following table, the relationship between the strength of the discharge member and the tooth angle was changed by changing the tooth angle of the discharge member in the discharge device for charging, transferring, and separating, and performing 10,000 copy operations for each tooth angle. Thereafter, the shape of the discharge end was examined. In the following table, the symbol “印” indicates that no shape change was observed, and the symbol “×”
The mark indicates that a shape change was observed.

Tooth angle θ (°) 2 3 4 5 6 7 8 9 10 10 K After printing endurance × × × ○ ○ ○ ○ ○ ○ ○ As can be seen from the experimental results (see also FIG. 12), the tooth angle is 5 For those smaller than °, the shape of the discharge end changes, and uniform charging cannot be performed. It is considered that the reason for this is that if the tooth angle is too small, sufficient strength of the discharge end cannot be ensured, so that the discharge end is deformed by heat at the discharge point after printing. Therefore, in determining the shape of the tooth angle, it is necessary to sufficiently consider not only the amount of ozone generated but also the strength of the discharge end portion, and the strength must be such that the shape of the discharge end portion is not deformed by the discharge. It can be said that it is desirable to set a tooth angle (for example, 5 ° or more and 30 ° or less, preferably 15 ° or less) that can have the ozone generation amount. Discharge unevenness and discharge end pitch P, distance D between charged member and discharge end, and discharge unevenness The ratio of discharge end pitch P (mm) to discharge gap D (mm) is represented by D / P, and the relationship between D / P and discharge unevenness is examined. As shown in FIG. 13, when D / P is smaller than 2 or larger than 8, discharge unevenness which is regarded as a problem in practice occurs, but when D / P is 2 or more and 8 or less, discharge unevenness occurs. Is less, and the charged member can be charged substantially uniformly.
When it was 6 or less, the discharge unevenness was further reduced.

The evaluation of the discharge unevenness is from 1 to 5
(See FIG. 13). That is, as the effect on the obtained image quality, unevenness is clearly confirmed in the discharge unevenness rank 5 → image quality. Discharge unevenness rank 4 → Image quality can be visually confirmed. Discharge unevenness rank 3 → Image quality is not visually noticeable.

(It can be confirmed with a measuring instrument.) Discharge unevenness rank 2 → It is difficult to confirm uneven discharge even with a measuring instrument in image quality. Discharge unevenness rank 1 → No unevenness in image quality. In selecting the D / P optimum value, a discharge unevenness rank of 3 or less was selected so that unevenness was not visually observed in image quality. Serrated part 12
The following was prepared as the discharge member 1 for the plate thickness of the discharge end portion and the ozone generation amount. That is, by each of two kinds of materials, namely, a material X composed of iron, chromium and nickel, and a material Y composed of iron, chromium, nickel and molybdenum,
The tooth angle θ was changed for each of the discharge end pitches P1 mm, 2 mm, and 4 mm, and the plate thickness was changed for each. Each of these discharge members was housed in the ozone measuring device 90, and the amount of generated ozone was examined. At this time, the device 90 has a diameter of the duct 91 of 50 mm and a wind speed of 2 m.
/ Sec, low temperature and low humidity environment, discharge current Ic = -800 μA
And The results are as shown in FIG.

As can be seen from FIG. 14, the amount of ozone generated generally decreases as the plate thickness decreases. FIG.
Means that an ozone filter having a removal rate of 70% is used in a copying machine, and in the respective steps of charging the photosensitive drum, transferring the toner image to the transfer paper, and separating the transfer paper from the photosensitive drum after the transfer, Corona discharge device 10 as in the case of
FIG. 4 is a diagram showing a relationship between a discharge end portion plate thickness and an ozone generation amount and a relationship between the plate thickness and a discharge member strength when a discharge device of the following type is used. Here, the ozone generation amount was measured by an ozone measuring device 90 shown in FIG. As can be seen from FIG. 15, also in this case, the ozone generation amount decreases as the plate thickness decreases. -About covering the discharge end 11 part of the discharge member 1 electrically with a high resistance material etc.

In this regard, the corona discharge device 10 shown in FIG.
An experiment was performed by preparing a corona discharge device 100 having the same basic configuration as that described above and having the following discharge members. Forming method of discharge member 1 Etching process Material Stainless steel Plate thickness 0.05 mm Discharge end pitch 2 mm Tooth angle θ 20 ° of sawtooth portion 12 Coating film 13 at discharge end portion (see FIG. 1C) Forming method Ion beam assist evaporation material SiO ₂ film thickness 0.1μm Further, comparative example having as a comparative example, the basic form and a corona discharge device 10 is the same, the same discharge member 1 and the (but which does not form a coating film) An experiment was conducted by preparing an apparatus 1 and a comparative example apparatus 2 using a conventional wire method (a tungsten wire having a wire diameter of 50 μm was used as a discharge wire).

The apparatus shown in FIG. 10 was used to measure the amount of ozone generated. The duct 91 accommodating the discharge device had a diameter of 50 mm.
Then, a wind having a wind speed of 2 m / sec was sent to apply a DC high voltage to the discharge member. The air after passing through the discharge device in the duct 91 was measured by the ozone concentration meter 93. 1 mA discharge current
FIG. 16 shows the result of shaking up. As can be seen from FIG. 16, when the three types of discharge devices, the discharge device 100 according to the present invention, the comparative example device 1 and the comparative example device 2 are compared, the ozone generation amount is the same discharge current and the discharge device 100: the comparative example device 1: Comparative device 2 # 1: 3:12. That is,
It can be seen that the discharge device 100 using the discharge member covering the discharge end can reduce the ozone generation amount to about 1/12 compared to the conventional wire-type discharge device.

Next, the discharge current flowing from each portion in the longitudinal direction of the discharge member to the charged member side when corona discharge was performed in the discharge device 100 according to the present invention and the comparative example device 1 was measured. The result was obtained. Similarly, when the discharge current after discharging the discharge device 100 and the comparative example device 1 for a long time was measured, the results of FIGS. 18 and 20 were obtained. As can be seen from these figures, in the comparative example device 1 in which the discharge member 1 is not covered with the high-resistance material, the discharge current becomes uneven as shown in FIG. Even after prolonged discharge, FIG.
And uneven discharge current is unlikely to occur. In other words, it can be said that the durability is improved and the discharge stability is improved because the discharge end portion is covered with the high resistance material. -About the voltage etc. applied to a discharge member.

A corona discharge device 10 according to the present invention shown in FIG. 1 is prepared, and is mounted on an ozone measuring device 90 shown in FIG.
And the power supply was connected to the sawtooth discharge member 1 to measure the amount of ozone generated. Further, for comparison, a comparative example apparatus using a conventional wire method was prepared, and the ozone generation amount was similarly measured for this apparatus. Apparatus of the present invention, DC voltage of positive polarity for any of the comparative example device,
Discharge by applying a negative DC voltage and an AC voltage (hereinafter referred to as (+) discharge, (-) discharge, A
Recorded as C discharge. ) Was performed, and the amount of ozone generated at that time was measured. The result shown in FIG. 21 was obtained.

Conventionally, the ratio of the amount of ozone generated by the most general-purpose wire electrode discharge device is as follows, assuming that the amount of ozone generated when a positive direct current voltage is applied and the discharge current is 400 μA is 1. -) Discharge: AC discharge: (+) discharge
At 7: 4: 1, the amount of ozone generated by the AC discharge is the sum of the ozone generation amounts of the (+) component and the (-) component, that is, 7/2 + 1 /
2 = 4. On the other hand, in a discharge device using a sawtooth discharge member, the ratio of the ozone generation amount is (−) discharge: AC discharge: (+) discharge ≒ 2.5: 1: 1 to 2.5, and the ozone generation amount in AC is The least.

From the above, it can be seen that if a corona discharge is performed by using a discharge member having a sharp discharge end and applying a high voltage having an AC component thereto, the ozone generation amount can be reduced. FIGS. 22, 23, and 24 show a case where a corona discharge device 10 is used for charging a photosensitive drum PC of a copying machine, and a discharge voltage including an AC voltage component is applied to a discharge member 1 of the device. An example of the power supply 4 is shown. In FIG. 22, the corona discharge is performed by the AC transformer 41. In FIG. 23, the AC high-voltage power supply 42 and the DC generator 4
In FIG. 24, the AC transformer 44 and the DC power supply 45 superimpose an alternating current (AC) voltage on a direct current (DC) applied voltage in FIG. In the embodiment of FIGS. 23 and 24, it is possible to charge efficiently with the reduction in the amount of ozone generated by the application of AC.

In FIGS. 22 to 24, T is a transfer charger, and S is a separation charger. For these, a corona discharge device using a discharge member having a sharp discharge end is also used. For these power supplies, the same as those for the discharge device 10 can be considered. In the figure, D is a developing device, and CL is a cleaner for cleaning residual toner.

Finally, FIGS. 25 to 28 show ozone generated when a discharge device and a comparative device of the type shown in FIG. 1 were used for charging a photosensitive drum of a copying machine. Shows the amount generated. The discharge device discharge member 1 according to the present invention is formed from a stainless steel plate having a plate thickness of 0.05 mm with a discharge end pitch P = 2 mm and a tooth angle θ of the sawtooth portion 12 = 20 °. 1 μm
Cover with a thick SiO ₂ film. The distance D from the discharge end 11 to the surface of the photosensitive drum is set to 6 mm, and the distance (skirt length) from the discharge end to the end of the both-side stabilizer 3 in the direction from the discharge end to the photosensitive member surface is set to 4 mm.

Comparative Example Apparatus The apparatus of the present invention described above, but not coated with a SiO ₂ film. The ozone generation amount was measured by the device 90 in FIG. 10, and the diameter of the duct 91 was 50 mm, the wind speed was 2 m / sec,
0 ° C. and 34% RH. Figure 25 is, (-) Ic when performing discharge (discharge current) - indicates the amount of generated ozone, (-) obtained by SiO ₂ coated even when the discharge is seen that a high ozone reduction effect.

FIG. 26 shows that the discharge current I
The c to perform the discharge as ± 200 .mu.A, is indicative of the amount of ozone generated when waved frequency, that the ozone generation amount higher the frequency is lowered, as compared with those without coating, SiO ₂ The coating shows that it is possible to significantly reduce the amount of generated ozone. FIG.
FIG. 6 is a diagram showing a result when a discharge current Ic is varied in a case where (AC) discharge is performed. The frequency is 200
Hz and 1000 Hz were sampled. Compared to without coating, 1000Hz that those SiO ₂ coating to decrease ozone generation amount, the frequency of the applied high frequency is small ozone generation amount towards higher 1000Hz compared to 200 Hz, a material obtained by SiO ₂ coated It can be seen that when the AC discharge is performed, the ozone amount is significantly reduced.

FIG. 28 shows the amount of ozone generated in the case of no coating and the case of SiO ₂ coating when the sum of the AC voltage current components was varied. Here, the current component is set in the range of 0 to ± 200 μA for both positive and negative. It can be seen that the ozone generation amount is small when the sum of the positive and negative current components is in the range of -200 μA to +100 μA, and that the ozone generation amount decreases as the sum of the current components approaches zero.

[0049]

According to the present invention, there is provided a corona discharge device for use in an electrophotographic image forming apparatus, which generates a small amount of ozone and can uniformly apply a charge to a charged member. be able to.

[Brief description of the drawings]

FIG. 1A is a perspective view of one embodiment of the present invention, and FIG.
The figure is an enlarged perspective view of a part of the discharge member shown in FIG.
FIG. 3C is a perspective view showing a state where the discharge end of the discharge member shown in FIG.

FIG. 2 is a diagram showing another example of the shape of the discharge end portion of the discharge member.

FIG. 3 is a view showing an example in which each discharge end portion shown in FIG. 2 is coated with a high-resistance material.

FIG. 4 is an enlarged view showing a state after discharging for 100 hours at a discharge end portion of an iron material.

FIG. 5 is an enlarged view showing a state before use of a discharge end portion made of a material containing nickel and chromium in iron.

6 is an enlarged view showing a state after discharging for 100 hours at a discharge end portion shown in FIG. 5;

FIG. 7 is an enlarged view showing a state after discharging for 100 hours at a discharge end portion made of a material containing nickel, chromium, and molybdenum in iron.

FIG. 8 is a graph showing a measurement result of a discharge current flowing from each part in a longitudinal direction of a discharge member made of an iron material to a charged member side.

FIG. 9 is a graph showing a measurement result of a discharge current flowing from each portion in the longitudinal direction of the discharge member made of a material containing nickel, chromium, and molybdenum to iron to the charged member.

FIG. 10 is a diagram showing a schematic configuration of an ozone measuring device.

FIG. 11 is a graph showing the relationship between the tooth angle θ of the discharge end of the sawtooth discharge member and the amount of ozone generated.

FIG. 12 is a graph showing a relationship between a tooth angle θ of a discharge end of a discharge member and an ozone generation amount and a relation between a tooth angle θ and a partial intensity of a discharge end of a discharge member in a corona discharge device according to the present invention employed in a copying machine.

FIG. 13 is a graph showing the relationship between the discharge end pitch P of the discharge member, the distance D between the discharge end and the charged member, and the amount of ozone generation.

FIG. 14 is a graph showing the relationship between the plate thickness of the discharge end portion of the sawtooth discharge member and the amount of ozone generated.

FIG. 15 is a graph showing a relationship between a plate thickness of a discharge end portion of a discharge member and an ozone generation amount and a relationship between the plate thickness and a discharge end portion strength in a corona discharge device according to the present invention employed in a copying machine.

FIG. 16 is a graph showing a relationship between a discharge current amount and an ozone generation amount in a discharge device in which a discharge end portion is coated with a high-resistance material film, a discharge device without the coating film, and a wire electrode type discharge device.

FIG. 17 is a graph showing discharge unevenness in a longitudinal direction of a discharge member in which a discharge end portion is covered with a high-resistance material film before use.

18 is a graph showing discharge unevenness after a long-time discharge in the longitudinal direction of the discharge member of FIG.

FIG. 19 is a graph showing discharge unevenness in a longitudinal direction before use of a discharge member whose discharge end portion is not covered with a high-resistance material film.

FIG. 20 is a graph showing discharge unevenness after long-time discharge in the longitudinal direction of the discharge member of FIG. 19;

FIG. 21 is a graph showing a relationship between a discharge current amount and an ozone generation amount when a DC voltage is applied and an AC voltage is applied in a wire electrode discharge device and a discharge device having a sawtooth discharge member.

FIG. 22 is a diagram showing an example of a power supply for the discharge device of the present invention.

FIG. 23 is a diagram showing another example of the power supply for the discharge device of the present invention.

FIG. 24 is a diagram showing still another example of the power supply for the discharge device of the present invention.

FIG. 25 is a graph showing the amount of ozone generated when the discharge end portion of the discharge member is covered with a high-resistance material and when it is not.

FIG. 26 is a graph showing the relationship between the frequency of an applied high-frequency voltage and the amount of ozone generated when a discharge end portion of a discharge member is coated with a high-resistance material and when it is not.

FIG. 27 is a graph showing an ozone generation amount when a discharge current amount is varied in a case where (AC) discharge is performed.

FIG. 28: O ₃ when the sum of the current components of the AC voltage is changed
It is a graph which shows the amount of generation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Corona discharge device 1 Discharge member 11 Discharge end 12 Serrated part 13, 19 Coating film made of high-resistance material P Discharge end pitch D Discharge end-charged member distance 2 Holding member 3 Stabilizer 30 Ceiling stabilizer 4 Discharge Power supply 41 AC transformer 42 AC high-voltage power supply 43 DC generator 44 AC transformer 45 DC power supply

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-223768 (JP, A) JP-A-55-144267 (JP, A) JP-A-7-5746 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/02 101

Claims (5)

(57) [Claims] 1. A corona discharge device in an electrophotographic image forming apparatus, comprising: a discharge member in which a plurality of sharp discharge ends are arranged in a line, wherein the discharge end and a charged member in the image forming apparatus are provided. The gap distance D (mm) between the charged member and the moving orbit and the pitch P (mm) of the discharge end are 2
≦ D / P ≦ 8, and the discharge member is
A corona discharge device comprising an alloy containing 6 to 20% chromium and 8 to 15% nickel. 2. The corona discharge device according to claim 1, wherein said alloy contains molybdenum. 3. A corona discharge device in an electrophotographic image forming apparatus, comprising: a discharge member in which a plurality of sharp discharge ends are arranged in a line, wherein the discharge end and a charged member in the image forming apparatus. The gap distance D (mm) between the charged member and the moving orbit and the pitch P (mm) of the discharge end are 2
≦ D / P ≦ 8, wherein the discharge end is covered with a dielectric material. To wherein said discharge member, a corona discharge according to any one of claims 1 to 3, characterized in that frequency to apply a discharge voltage including an AC voltage component is 400Hz or more 1.5kHz or less apparatus. 5. The method according to claim 1, wherein the sharp discharge end has a saw-tooth shape.
The tooth angle of the tooth is 5 ° or more and 30 ° or less, and the saw tooth thickness is about 0.0
The corona discharge device according to claim 1, wherein the corona discharge device is 5 mm .