JPH0562741B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the invention [Industrial field of application] The present invention can be incorporated into image forming devices such as electrophotographic devices and electrostatic recording devices, surface activation processing devices for plastic films, etc. This invention relates to a corona discharge treatment device used in

More specifically, there is a corona discharge treatment device that has a corona discharge electrode and a shielding plate surrounding it, and charges or eliminates electricity on the surface of the charged object by moving the openings for corona discharge opposite the surface of the charged object and moving the two relative to each other. The present invention relates to a corona discharge treatment device (so-called scorotron device) which is further equipped with a discharge current control member (grid).

[Conventional technology]

For convenience, an electrophotographic apparatus will be described below as an example. 2. Description of the Related Art Electrophotographic apparatuses include, at various points in a series of image forming processes, steps for charging or neutralizing the surface of a photoreceptor or transfer material as a charged object.

Figure 1 shows an example of an electrophotographic device published in the 1970s.
This figure shows a very schematic structure of the image forming process disclosed in Publication No. 23910 or No. 24748 of 1972. Reference numeral 1 denotes a photosensitive drum as a charged body that rotates at a constant speed in the direction of arrow a. At the same time as it receives pre-exposure from a light source 2 ₁ , it is pre-neutralized by a corona discharge treatment device 3, so that the surface of the photosensitive drum is uniform. The potential level is maintained at a certain level. Next, the corona discharge treatment device 4 receives a primary charge with a polarity different from the above-mentioned pre-static charge removal, and the corona discharge treatment device 5 receives a secondary charge with a polarity different from the primary charge or charge removal with an AC corona. At the same time or immediately after, by receiving the light pattern irradiation L (slit exposure, laser beam scanning exposure, etc.) through the lens 6 of the optical system, electrostatic latent images facing the exposed light pattern are sequentially formed on the photosensitive drum. . Then, the entire surface is exposed to light source 2 ₂ ,
The potential contrast of the formed latent image is enhanced. Next, the latent image is developed with a developing colored powder (hereinafter referred to as toner) in a developing device 7 to become a visible image. This visible image is sequentially transferred onto the surface of the transfer material 9 by the charging action of the corona discharge treatment device 8.
The transfer material 9 on which the image has been transferred is separated from the photosensitive drum surface, introduced into a fixing device (not shown), where the image is fixed, and then discharged outside the machine as a copy. On the other hand, the surface of the photosensitive drum 1 after the transfer is cleaned by a cleaning device 10 to remove residual toner after transfer, and thereafter the same process as described above is repeated.

Figure 2 shows a typical corona discharge treatment device A that is incorporated into an electrophotographic device such as the one mentioned above.
(Corotron device) Figure a is a longitudinal sectional front view, Figure b is a plan view, and Figure C is the c-line of Figure A.
The sectional view taken along the line c and the figure d are also sectional views taken along the line dd. That is, a conductive shield plate 32 (made of stainless steel, for example) having a substantially U-shaped cross section with the side facing the photosensitive drum 1 as an object to be charged open as a discharge opening 34, and a conductive shield plate 32 (made of stainless steel, for example) attached to both ends of the shield plate. It consists of insulating blocks 33, 33, and a corona discharge wire 31 as a corona discharge electrode located within the shield plate and stretched between the insulating blocks at both ends.

Reference numeral 33a denotes a feeder provided on one side of the insulating block 33, and the corona discharge wire 31 connects its one end to the feeder 33 via a conductive tension spring 38.
a and the other end to the other insulating block 33.
It is locked by a locking piece 33b provided in the spring 3.
It is kept under constant tension with a tensile force of 8.

34a is the discharge opening 34 of the shield plate 32
This is an airflow (outside air) inflow opening formed along the length of the top plate on the opposite side. Some shield plates are designed so that the opening is provided at the boundary between the top plate and the side plate of the shield plate 32, or on the side plate side. In some cases, the opening is not particularly provided. In corona discharge treatment devices 3 and 5 in FIG. 1, which introduce light, the shield plate 32 is also opened on the side opposite to the discharge opening 34 for light guide, or a window hole for light guide is provided. Constructed into a formed form. Some have a transparent plate made of glass or the like stretched over the opening or window hole for guiding the light.

The corona discharge treatment apparatus A is designed to have a required length dimension according to the width dimension (dimension in the generatrix direction) of the photosensitive drum 1, which is the object to be charged.

The scorotron device is constructed by further equipping the above-described corotron device with a grid wire 39 (corona discharge treatment devices 3, 5 in FIG. 1) serving as a discharge current control member at the discharge opening.

The corona discharge wire 31 is supplied with a direct current high voltage (when obtaining positive or negative DC corona discharge) or an alternating current high voltage (when obtaining AC corona discharge) from a high voltage power source (not shown) via the feeder 33a. A superimposed high voltage of both DC and AC is applied, and the shield plate 3
2 is grounded, or by applying a bias voltage of an appropriate potential from a bias power source, the gas (air) around the corona discharge wire 31 becomes ionized. Then, the ionized charged particles move toward the discharge opening, give kinetic energy to the gas molecules at that time, and generate ionic wind b in the discharge opening 34, and this ionic wind b causes the surface of the photosensitive drum and The surface of the object to be charged, such as the back surface of the transfer material 9, is charged or neutralized.

[Problem that the invention seeks to solve]

The ion wind b is emitted from the shield plate 32.
However, the wind pressure distribution of the ion wind along the length of the discharge opening is weaker at both ends than at the center of the length of the discharge opening. This is because there are insulating blocks 33, 33 supporting the corona discharge wire 31 on both ends of the shield plate 32, so that the discharge becomes weak at the portions closer to the insulating blocks.

On the other hand, as the ion wind b is blown out, the pressure inside the shield plate 32 becomes negative. In order to compensate for this, outside air c flows into the interior of the shield plate from the air flow inflow opening 34a and the corona discharge opening at each longitudinal portion of the shield plate 32 in parallel with the blowing out of the ion wind b. The wind pressure distribution of this inflowing outside air c along the length of the corona discharge opening is as follows:
The wind pressure distribution of the above blown ion wind b is in the central part -
Since the strength is strong and the strength is weak at both ends, the distribution is opposite to this: weak at the center and strong at both ends.

In addition, as the drum 1 rotates, a laminar air flow d called a drum wind (Fig. 3 c, d) is generated around the drum.The drum wind d is caused by the shield plate at the location where the discharge treatment equipment is installed. 32, a part of the drum wind d ₁ becomes a turbulent flow and flows into the interior of the shield plate from _the corona discharge opening.
The inflow amount distribution along the length of the corona discharge opening is, as mentioned above, the ionic wind b along the length of the corona discharge opening.
Since the distribution of balloons is strong in the center and weak at both ends, on the contrary, the distribution is weak at the center (FIG. 2c) and strong at both ends (d in the same figure).

From the above, corona discharge and drum 1
The inflow of outside air c + drum wind d ₁ from the corona discharge opening side into the shield plate internal space due to the rotation of the corona discharge opening is substantially localized at both ends of the corona discharge opening with respect to the length of the corona discharge opening. Moreover, the current velocity is quite strong.

Therefore, external foreign matter is likely to actively get stuck into the shield plate 32 due to the locally strong outside air c + drum wind d ₁ flowing into the shield plate 32 at both ends thereof.

In an electrophotographic apparatus such as the example shown in FIG. 1, scattered toner from the developing device 7 and cleaning device 10, paper dust generated from the transfer material 9, and other dust are floating in the air inside the apparatus. In particular, since it is technically difficult to completely prevent toner from leaking and scattering from both ends of the photosensitive drum in the developing device 7 and cleaning device 10, the air around both ends of the photosensitive drum 1 is particularly prone to scattering. - The atmosphere tends to contain a lot of floating toner. In addition, toner, transfer material paper dust, and other dust attached to the peripheral surfaces of both ends of the photosensitive drum 1 tend to remain on the surface without being completely removed by the cleaning device. The air around the drum tends to contain detached materials such as the toner remaining after removal.

As a result, corona discharge processing equipment is inherently prone to dirt due to dust collection caused by high-voltage electric fields; Toner remaining after cleaning on the surrounding surface is generated by local strong outside air c + drum wind d ₁ at both ends of the discharge processing device.
The shield plate 32 is actively
By getting inside, the inner surfaces of the corona discharge wire 31 and the shield plate 32 are quickly and appropriately contaminated. Foreign matter contamination on the inner surfaces of the corona discharge wire 31 and shield plate 32 is one of the major causes of uneven discharge, and in the case of electrophotographic devices, it has a large negative effect on image quality, so cleaning must be performed frequently. Nakatsuta.

Here, in a type of corona discharge treatment apparatus that does not have an airflow inflow opening 34, the outside air c flows into the inner space of the shield plate 32 due to corona discharge only on the corona discharge opening side, and there is no flow at both ends of the apparatus. Since the inflow wind pressure of the outside air c becomes stronger than in the case of the type having the opening 34, the degree and progress of dirt on the inner surfaces of the corona discharge wire 31 and the shield plate 32 becomes even more remarkable.

Furthermore, by increasing the width of the airflow inflow opening 34, the amount of inflow of outside air c from the corona discharge opening side can be reduced to some extent, but if the width is a certain width, there is no effect even if it is made wider.

Therefore, as disclosed in Japanese Utility Model Application Publication No. 57-93942, it is known to provide air inflow prevention means at both ends of the discharge opening of the discharge treatment apparatus, but this method prevents outside air from entering the inside of the discharge treatment apparatus. The inflow was essential and had little effect in suppressing the inflow of outside air.

Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 57-188062, conductive members are provided on the top surfaces of insulating blocks at both ends of the discharge treatment apparatus to increase the amount of discharge at the ends of the discharge treatment apparatus. Some devices suppress the inflow of outside air c into the interior of the shield member from both ends of the discharge opening by strengthening the ion wind at the ends. This has a great effect, and an even greater effect can be obtained by providing an opening for outside air inflow in a part of the shield member. However, unnecessarily increasing the amount of discharge will cause problems such as increased ozone generation and the need for a high-capacity, high-voltage power supply.
In some cases, practical problems also occurred.

As mentioned above, the discharge treatment is based on the inflow of outside air c into the discharge treatment device due to discharge, and the inflow of outside air _d into the discharge treatment device due to the relative movement between the discharge treatment device and the surface of the charged object. The problem of contamination inside the device over time is not limited to electrophotographic devices as in the example above, but also to electrostatic recording devices, surface activation devices such as plastic films, etc. that have a corona discharge electrode and a shielding plate surrounding it. Using a corona discharge treatment device, the corona discharge opening of the discharge treatment device is opposed to the surface of the object to be charged, and the two are moved relative to each other to charge or neutralize the surface of the object to be charged. This is a common problem in devices that include such a charging or neutralizing step in the treatment process.

The present invention solves the above problems.

B. Structure of the Invention [Means for Solving Problems] The present invention provides a corona discharge electrode, a shield surrounding the electrode, and a shield including a corona discharge opening and a second opening, and the second opening. a blowing means for sending clean air into the shield from the opening, and a corona discharge for charging or neutralizing the surface of the charged object by relatively moving the opening for corona discharge and the surface of the charged object opposite thereto. In the processing device,
The blowing means is operated during or immediately before a period of relative movement between the corona discharge opening and the surface of the charged object,
The gist is a corona discharge treatment apparatus that is characterized in that it is in an operating state immediately after the treatment and is in a stopped state at other times.

[Effect]

That is, an opening separate from the opening for corona discharge is provided in the shielding plate of the corona discharge treatment device, and air is actively blown from the opening into the shielding pullet surrounding the corona discharge electrode using a blowing means. A blow-out air curtain is generated at the opening, which faces the external air flowing into the shielding plate from the discharge opening and the relative movement between the discharge processing device and the surface of the charged object.
Therefore, the air curtain of the blowing system should have a blowing force that can sufficiently counter the above-mentioned inflowing outside air force, and the air blown into the shield plate to form the air curtain should be dedusted and dehumidified. By providing such clean air, the inflow of outside air containing dust from the discharge opening into the shielding plate is inhibited, and foreign matter contamination within the discharge processing apparatus is prevented.

In addition, even if the corona discharge treatment device is not in the discharge state (discharge suspension period), if there is a relative movement between the discharge treatment device and the surface of the charged object, the discharge from the corona discharge opening is based on the relative movement. Outside air containing dust tries to flow into the shielding plate. Therefore, in the present invention, regardless of the discharge period or discharging period of the corona discharge treatment device, the blowing means is kept in an operating state at least during the period of relative movement between the discharge treatment device and the surface of the object to be charged. This prevents the inflow of outside air containing dust from the discharge opening into the shield plate during the discharge suspension period of the corona discharge treatment device and the period of relative movement between the discharge treatment device and the surface of the charged object. The interior of the discharge treatment apparatus can be protected from foreign matter contamination over a long period of time, and the frequency of cleaning operations can be significantly reduced or substantially eliminated.

〔Example〕

Example 1 (Figure 3) 37 is a blower, and the air from the blower is used for dust removal and
The air is dehumidified (the dust removal and dehumidification filters are omitted in the figure) and is actively introduced into the inner space of the shield plate 32 from the air flow inflow opening 34a through the air duct 35, and the air is blown from the corona discharge opening 34. Blows out as a blowout type air curtain e ₁ . The air curtain _e1 prevents the outside air c+drum wind _d1 (FIG. 2) containing dust from flowing into the interior of the shield member from the discharge opening 34 side. Reference numeral 36 denotes an air baffle plate appropriately disposed within the air duct 35 in order to provide a substantially uniform strong air flow to each longitudinal portion of the corona discharge wire 31.

Figures 4a to 4d show examples of control sequences for the blower means.

(a) The figure shows the most preferred example of the ventilation sequence.
That is, considering the rise of the air after the blower 37 is turned on, the blower 37 is turned on slightly before the rotation of the photoreceptor drum 1 starts, and the corona discharge period ends, and then the photoreceptor drum is turned on. The operation of the air blower 37 is turned off slightly after the post-rotation period of 1 ends and the drum 1 is completely stopped.

(b) The figure shows the drive signal synchronized with the photoreceptor drum drive signal.
The blowing sequence when the blower drive signal is obtained is shown. In a normal braille photographic device, when a drive signal is input to the drive source (main motor) that drives the photoreceptor drum, the photoreceptor drum starts rotating after a certain period of time, and after another period of time it reaches a steady state. Rotation is reached and each process of copying begins. That is, for a while after the photoreceptor drum drive start signal is input, the photoreceptor drum does not rotate or does not reach a predetermined normal rotation, and during this time it can be said that the photoreceptor drum is in a semi-operational state. . This phenomenon can be said to be caused by a large load being applied to the drive source of the photoreceptor drum. On the other hand, the load applied to the drive source of the blower is smaller than the load applied to the drive source of the photoreceptor drum, so it starts up quickly and transitions from the semi-operating state to the operating state in a relatively short time. It will be held in

Further, even if the photoreceptor drum is rotating, if corona discharge is not being performed, the inflow of outside air from the corona discharge opening can be prevented even if the amount of air blown is smaller than the amount of air blown required during corona discharge. That is, when the drive signals of the photoreceptor drum and the blower are synchronized, air blowing is started before the photoreceptor drum starts rotating steadily, and the purpose of the present invention is achieved. For example, in this embodiment, it took about 0.6 seconds for the drum to reach steady rotation after inputting the drive signal. Furthermore, if a simultaneous drive release signal is input to the photoreceptor drum and the blower after the copying process is completed, the air continues to be blown for a while even after the photoreceptor drum has stopped rotating due to the difference in the load applied to the drive source. That is, at the time of falling, the blower remains in a semi-operational state for a long time.

As explained above, even if the drive signals input to the photoreceptor drum and the blower are completely synchronized, the photoreceptor drum will be in the operating state if you take into account the rise and fall of the operation of the photoreceptor drum and the blower. During this time, the purpose of the present invention can be achieved by blowing air from the blower. In addition, considering the operation of the blower and the photoreceptor drum, it is also possible to synchronize other signals at approximately the same time as the rotational drive signal of the photoreceptor drum, such as the pre-exposure lamp drive signal and the blower drive signal in this embodiment. Also good.

(c) The figure shows a sequence in which the blower 37 is normally maintained in the operating state even during the standby period of the device. This sequence is undesirable because there are many wasted air blowing periods, which shortens the life of the filter of the blower 37.

(d) In the figure, the blower 37 is operated in synchronization with the on/off of the corona discharge treatment device. In this case, the drum wind d ₁ (FIG. 3c, d) flows into the corona discharge treatment apparatus during the pre-rotation period and the post-rotation period of the photosensitive drum 1, which is not preferable.

Example 2 (Figure 5) In this example, clean air is blown into the shielding plate so that the amount of air blown at both ends is larger than the amount of air blown at the center in the longitudinal direction of the corona discharge treatment device. It is configured to distribute wind.

40 and 40 are the wind speed or the air volume in the inner space of the shield plate 32, or both ends of the air e introduced from the air duct 35 into the inner space of the shield plate 32 through the air flow inflow opening 34a. The air distribution plate is arranged in the air duct 35 in such a position and angular orientation that the area near the side insulation blocks 33, 33 is larger than other areas.

As a result, a large amount of air e is distributed to both longitudinal ends of the corona discharge opening, resulting in a strong blowing air curtain e ₂ , that is, a strong outside air c + drum that tries to flow into the discharge processing apparatus from both longitudinal ends of the corona discharge opening. An air curtain e ₂ strong enough to sufficiently suppress the wind d ₁ is formed. At the longitudinal center of the corona discharge opening, the amount of air blown is reduced by the amount of air blown e being distributed to both ends, and the air curtain e ₁ formed is somewhat weaker, but the flow of air from that part into the discharge treatment equipment is smaller. Outside air trying to flow in c+
Since the wind pressure of the drum wind _d1 is weak, its inflow can be sufficiently suppressed in practice.

In other words, by using a small-capacity blower with advantages such as small size, low power consumption, and low noise, it is possible to sufficiently prevent foreign matter from entering the corona discharge treatment equipment and maintain stable discharge characteristics. Maintained for a long time.

Embodiment 3 (FIG. 6) This example is a modification of the above-mentioned Embodiment 2, and the air e from the air blower 37 is substantially concentrated and distributed only on both ends of the interior space of the shield plate 32. This is how it was done. The action and effect are the same as in Example 2.

C. Effects of the Invention As described above, according to the present invention, the inside of the corona discharge treatment device can be maintained in a clean state free of foreign matter contamination for a long period of time, and the frequency of cleaning work can be significantly reduced. , or can be substantially eliminated. For example, in the case of an electrophotographic apparatus, it is possible to maintain stable image forming processing performance over a long period of time.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an example of an electrophotographic device, and Fig. 2 a, b, c, and d are a vertical front view, a plan view, a cross-sectional view of the center portion, and a cross-sectional view of the end side of the corona discharge treatment device. Fig. 3 is a cross-sectional view of the first embodiment of the present invention, Fig. 4 a, b, c, and d are blower control sequence examples, respectively, and Fig. 5 a, b, and c are the second embodiment. FIG. 6 is a vertical sectional front view of the third embodiment; 1 is a photosensitive drum; 3, 4, 5, 8, and A are corona discharge treatment devices; and 37 is a blower.

Claims (1)

[Claims] 1. A corona discharge electrode, a shield surrounding the electrode, the shield having a corona discharge opening and a second opening, and supplying clean air into the shield from the second opening. A corona discharge treatment apparatus that charges or neutralizes the surface of the charged object by relatively moving the corona discharge opening and the surface of the charged object opposite thereto, the corona discharge processing apparatus comprising: A corona discharge treatment device characterized in that it is in an operating state during, immediately before, or immediately after a period of relative movement between the discharge opening and the surface of the charged object, and is in a stopped state at other times.