JPH04301862A - Scorotron electrifier - Google Patents

Abstract

PURPOSE:To prevent the degradation of an image caused by an electrifying action by always realizing the stable electrification processing of a potential over a wide area with respect to a photosensitive body so that a discharge is stabilized from low-potential electrification to high-potential electrification and ununiform electrification is avoided. CONSTITUTION:In this scorotron electrifier having a discharging wire 102a, a shielding case 102b disposed so as to surround the discharging wire 102a, and a grid 102c, and variably controlling the voltage of the grid 102c to control the potential by electrification with respect to the photosensitive body 101, a varistor 120 keeping a potential difference between the discharging wire 102a and the grid 102c almost constant, is provided.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention comprises a discharge wire, a shield disposed to surround the discharge wire, and a grid, and the voltage of the grid is variably controlled to control the charging potential to a photoreceptor. The present invention relates to a scorotron charging device, and more particularly to a scorotron charging device that stably charges a photoreceptor over a wide range of potentials.

0002

2. Description of the Related Art In an electrophotographic apparatus, as one of a series of image forming processes, there is a charging process that charges the surface of a photoreceptor, which is a member to be charged. A grid is provided between the and photoreceptor,
There is a so-called scorotron charging device that applies a voltage to the grid to control the charging potential on the photoreceptor.

A scorotron charging device performs charging processing by corona discharge. In order to obtain a good copy image, it is essential to charge the material to a uniform and constant charging potential, and therefore, a charging device that can perform stable corona discharge is desired. For example, Japanese Patent Application Laid-Open No. 63-183
"Charger" disclosed in Publication No. 464, JP-A-64
- "Image forming apparatus" disclosed in Publication No. 20580
There is an "image forming apparatus" disclosed in Japanese Unexamined Patent Publication No. 64-59263.

In Japanese Patent Laid-Open No. 63-183464, current is detected by detecting the voltage between the shield or grid and ground by resistor division, and this is further amplified by a high voltage transistor, and at the same time, a varistor and a high voltage TR are connected in parallel. By doing so, the potential of the shield or grid is stabilized.

Furthermore, in Japanese Patent Laid-Open No. 64-20580, a voltage adjustment device for finely adjusting the grid voltage is provided on the side of the cartridge in which the image forming process section is integrated, thereby accurately controlling the charging voltage on the surface of the photoreceptor. is controlled.

Furthermore, in Japanese Patent Laid-Open No. 64-59263, a series regulator that controls the output according to the detected output is inserted between the grid or shield and the ground, thereby stabilizing the output voltage and improving power efficiency. We are trying to improve.

[0007] In addition, in order to obtain a good image, a charging device must not only perform stable corona discharge, but also be able to charge from a low potential (for example, -200 to -400V) to a high potential (for example, , -700 to -1000V) that can control charging over a wide range of potentials.

[0008]

[Problems to be Solved by the Invention] However, in the methods disclosed in JP-A-63-183464, JP-A-64-20580, and JP-A-64-59263, the charging potential is controlled by adjusting the grid or shield voltage, but the load resistance of the discharge wire in the scorotron charging device is lower than that between the discharge wire and the photoreceptor, and the load resistance of the grid (or the shield case if it is a conductive shield case). Generally, the influence of the potential difference and distance between the grid and/or shield voltage and the discharge wire changes.
For example, even if stable discharge can be performed when charging at a low potential, there is a problem in that when charging at a high potential, the discharge becomes unstable and uneven charging is likely to occur.

The present invention has been made in view of the above, and it stabilizes discharge from low potential charging to high potential charging, and avoids non-uniform charging so as to always provide stable and wide range charging to the photoreceptor. The purpose of this invention is to prevent image deterioration caused by charging operation by realizing potential charging processing.

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a discharge electrode, a shield member disposed so as to surround the discharge electrode, and a control electrode, and the voltage of the control electrode is The present invention provides a scorotron charging device that controls the charging potential of a photoreceptor by variable control, and is provided with a holding means for keeping the potential difference between the discharge electrode and the control electrode substantially constant.

[0011] The present invention also includes cleaning means for the discharge electrode and the control electrode, and detection means for detecting a current value flowing through one or both of the control electrode and the shield member or the photoreceptor under predetermined discharge conditions. and a control means for driving and controlling the cleaning means when the current value becomes equal to or less than a predetermined value by the detection means.

[0012] Also, a cleaning means for the discharge electrode and the control electrode, a detection means for detecting the surface potential of the photoreceptor, and when the surface potential of the photoreceptor becomes equal to or less than a predetermined value by the detection means, at least the control means for driving and controlling the cleaning means with respect to the discharge electrode, and driving and controlling the cleaning means with respect to at least the control electrode when the surface potential of the photoreceptor becomes equal to or higher than a predetermined value by the detection means; A scorotron charging device is provided.

[0013] Further, a detection means for detecting the surface potential of the photoreceptor, and a voltage applied to the control electrode and/or a voltage applied to the discharge electrode are controlled according to the surface potential level detected by the detection means. The present invention provides a scorotron charging device having a control means for controlling the scorotron charging device.

[0014] Furthermore, a detection means for detecting a current value flowing through the discharge electrode, the control electrode, or the shield member or a current value flowing through the photoreceptor; The present invention provides a scorotron charging device comprising a voltage applied to a control electrode and/or a control means for controlling the voltage applied to the discharge electrode.

[0015]

[Operation] In the scorotron charging device according to the present invention, a constant voltage power source is used as the discharge wire and the grid power source, and the potential difference between the discharge wire and the grid is made approximately constant, thereby stabilizing the discharge and charging over a wide range of potentials. It improves control performance, and also detects the current flowing through the grid, shield, and photoconductor, as well as the charged potential of the photoconductor.Based on these detection results, the discharge wire or grid is cleaned and the applied voltage is controlled. Prevent image deterioration caused by motion.

[0016]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of the periphery of a photoreceptor in a copying machine to which a scorotron charging device 102 according to the present invention is applied. A charger (scorotron charging device) 102 that uniformly charges the surface of the body 101 by corona discharge, and a photoreceptor 10
1, an optical system 104 for projecting reading light (exposure) of a document (not shown) onto the photoreceptor 101, which has been charged, and the photoreceptor 101.
An eraser 105 that erases charges in the upper non-image area, a developing device 106 that attaches toner to the electrostatic latent image formed by exposure processing and visualizes it, and a recording paper (not shown).
a registration roller 107 for sending the toner image to the photoreceptor 101 at a predetermined timing; a transfer charger 108 for transferring the toner image formed on the photoreceptor 101 to recording paper;
A separation charger 109 that separates the recording paper after the transfer process from the photoconductor 101, a separation claw 110 that reliably separates the recording paper from the photoconductor 101, and a separation claw 110 that removes the toner remaining on the photoconductor 101 after the transfer process is finished. The cleaning device 111 includes a cleaning device 111 for cleaning the photoreceptor 101, and a discharge lamp 112 for erasing residual charges on the photoreceptor 101 after the cleaning process has been completed.

The image forming operation in the above configuration will be explained. The photoreceptor 101 is uniformly charged in advance by a charger 102, and then an electrostatic latent image corresponding to image information is formed on its surface by information light from an optical system 104. The electrostatic latent image is visualized by a developing device 106 and transferred by a transfer charger 108 onto a recording sheet conveyed by a registration roller 107. After the transfer process, the recording paper is separated by a separation charger 109 and a separation claw 110.
The images are separated by a fixing device (not shown), fixed by a fixing device (not shown), and discharged to the outside of the device. In addition, the photoconductor 10 after the transfer process
1, the residual toner is removed by the cleaning device 111, and the residual charge is further removed by the charge removal lamp 112, and the device enters a standby state in preparation for the next image forming process.

FIG. 2 shows an enlarged sectional view of the charging charger 102, and the charging charger 102 has a discharge wire 102a.
, a shield case 102b, and a grid 102c, and includes an upper discharge wire cleaning member 201a and a lower discharge wire cleaning member 201b for cleaning the discharge wire 102a, and a grid cleaning member 202 for cleaning the grid 102c. It has Note that these cleaning members are arranged on one support member, and the discharge wire 10
Cleaning of the support member 2a and the grid 102c is performed by sliding this support member along the wire by a drive system (not shown).

Furthermore, as shown in FIG. 1, the charger 102 includes a high voltage power source 113 for a discharge electrode that applies a voltage to the discharge wire 102a, a high voltage power source 114 for a grid that applies a voltage to the grid 102c, and each power source 113. and 1
A control circuit 11 that controls the applied voltage, timing, etc. of 14
5, a grid current detection circuit 116 that detects the current flowing through the grid 102c, and a grid current detection circuit 116.
An applied voltage correction amount calculation circuit 117 calculates a correction amount of the voltage applied to the discharge wire 102a based on the detected value and outputs the corrected amount to the control circuit, and detects the charged potential of the photoreceptor 101 based on a signal from the probe 103. and an applied voltage correction amount calculation circuit 119 that calculates a correction amount of the voltage applied to the discharge wire 102a based on the detection result of the surface potential detection circuit 118 and sends it to the control circuit. There is.

120 is the discharge wire 102a and the grid 1
In order to keep the voltage difference between 02c and 02c approximately constant, the discharge wire 10
2a and the grid 102c, and is a varistor connected between the high voltage power source 113 for the discharge electrode and the high voltage power source 11 for the grid.
4 is a constant voltage power supply.

The operation of the above configuration will be explained. When the copying process starts, the control circuit 115 sends a predetermined signal to the high voltage power source 113 for the discharge electrode and the high voltage power source 1 for the grid.
14, the application of voltage to the discharge wire 102a and the grid 102c is started. The current actually flowing through the grid 102c is detected by the grid current detection circuit 116, and the applied voltage correction amount calculation circuit 117 calculates the correction amount of the voltage applied to the discharge wire 102a based on the detected value, and calculates the correction amount for the voltage applied to the discharge wire 102a. is output to the control circuit 115. Here, what is detected by the grid current detection circuit 116 is:
This is the current value flowing into the grid 102c from the discharge wire 102a.

Further, the probe 103 is of a chopper type, and emits a detection signal according to the charged potential on the photoreceptor 101.
A charged potential is detected by the surface potential detection circuit 118 based on the detection signal, and the surface potential detection circuit 118 determines a correction amount for the voltage applied to the discharge wire 102a based on the detected value, and outputs the correction amount to the control circuit 115. do. When the control circuit 115 receives these correction amounts, it outputs a control signal to the discharge electrode high voltage power supply 113 so that an appropriate voltage is applied to the discharge wire 102a.

[0023] Here, the voltage difference between the discharge wire 102a and the grid 102c is kept approximately constant by the varistor 120, and the control circuit 115 uses the calculation results of the applied voltage correction amount calculation circuits 117 and 119. Based on the correction amount, it is determined whether or not to clean the discharge wire 102a and the grid 102c (the cleaning members for the discharge wire 102a and the grid 102c are disposed on one support member), and when cleaning is performed. If it is determined, the support member is moved after the copying process is completed, and the upper discharge wire cleaning member 201a, the lower discharge wire cleaning member 201b, and the grid cleaning member 2 are removed.
02, the discharge wire 102a and the grid 102c are controlled to be cleaned. In this embodiment, this cleaning process is performed when the amount of correction is quite large. In other words, this is because the charged potential of the photoreceptor 101 or the current flowing through the grid 102c is extremely large. It means that it has become smaller or smaller.

Below, applied voltage correction amount calculation circuit 117, 1
A mode of cleaning the discharge wire 102a or the grid 102c and controlling the voltage applied to the discharge wire 102a or the grid 102c will be explained based on the correction amount that is the calculation result of No. 19.

Under predetermined discharge conditions, the control wire 10
2a, the current value flowing through one or both of the shield cases 102b or the photoreceptor 101 is detected, and when the current value becomes below a certain value, the upper discharge wire cleaning member 201
a. Driving and controlling the lower discharge wire cleaning member 201b and the grid cleaning member 202.

Furthermore, the surface potential of the photoreceptor 101 is detected,
When the surface potential of the photoreceptor 101 becomes equal to or less than a predetermined value, the upper discharge wire cleaning member 201a and the lower discharge wire cleaning member 201b are driven and controlled for at least the discharge wire 102a, so that the surface potential of the photoreceptor 101 reaches a predetermined value. When this happens, the grid cleaning member 202 is driven and controlled for at least the grid 102c.

Furthermore, the surface potential of the photoreceptor 101 is detected,
Depending on the detected surface potential level, grid 102c
and/or the voltage applied to the discharge wire 102a.

Furthermore, the discharge wire 102a and the grid 10
2c, detect the current value flowing through the shield case 102b or the current value flowing through the photoreceptor 101, and control the voltage applied to the grid 102c and/or the voltage applied to the discharge wire 102a based on the detected current value. Note that the above embodiments are not limited to these.

Next, the charging characteristics of the scorotron charging device according to the present invention will be explained with reference to FIGS. 3 to 5.

FIG. 3 shows grid voltage Vg−charged potential Vo
The characteristic curve of Here, in the figure, the solid line A indicates the charger 102 of the present invention (constant potential difference between the discharge wire 102a and the grid 102c: -5.5KV), and the dashed line B indicates the constant voltage applied to the discharge wire (-6.0KV), The dashed dotted line C shows a curve when the discharge current is constant (-800 μA), and the broken line shows a straight line of Vg=Vo. As is clear from the figure, according to the present invention (solid line A), the charge control performance is better over a wide range than in the other cases (dotted chain line B, double-dotted chain line C). This means, for example, that image density can be adjusted by controlling the charging potential.

The image density can also be adjusted by controlling the voltage applied to the developing bias.
When the developing bias applied voltage is increased in a developing device using a two-component dry developer, there is a risk that carriers will adhere to the photoreceptor, resulting in staining inside the device, poor transfer, and damage to the cleaning member.

FIG. 4 shows a characteristic curve of grid voltage Vg versus charging potential unevenness. Here, the charging potential unevenness refers to the difference between the maximum charging potential and the minimum charging potential on the photoreceptor 101, and A, B, and C shown in the figure are the same as in FIG. 3, respectively. As is clear from the figure, the present invention (solid line A)
It can be seen that, compared to other cases, even if the grid voltage Vg is varied over a wide range, the charging potential unevenness is small and the fluctuation is also small.

FIG. 5 shows a capacitance-charged potential Vo characteristic curve of the photoreceptor 101. Here, as discharge conditions, the solid line A shows the curve when the voltage applied to the discharge wire is constant at -6.3KV and the voltage applied to the grid is constant at -800V, and the dashed double-dashed line B
shows a curve when the voltage applied to the discharge wire is constant at -800 μA and the voltage applied to the grid is constant at -800 V. From the figure, it is better to apply a constant voltage to the discharge wire 102a than a constant current.
It can be seen that the charging potential Vo is stabilized when there is a difference in the capacitance of the photoreceptor 101 at the initial stage or over time.

From the above results, in the scorotron charging device, the load resistance of the discharge wire 102a is
Generally, the influence of the potential difference and distance between the grid 102c (or the shield case 102b in the case of a conductive shield case) is greater than that between the discharge wire 102a and the grid 101 as in the present invention.
By keeping the potential difference between the discharge wire 102b and the discharge wire 102 constant, changes in the discharge state such as discharge current and discharge unevenness can be reduced.
When a constant voltage is applied to a, the control performance of the charging process is improved more than when a constant current is applied.

In this embodiment, the discharge wire 102a
and the grid 102c, respectively, but a single power source may be used to create a substantially constant voltage difference between the discharge wire 102a and the grid 102c. Alternatively, the discharge current from the discharge wire 102a to the photoreceptor 101 may be detected. In this case, for example, when the conductive shield case 102b is provided, it is not necessary to detect the discharge current to the photoreceptor 101 by detecting the current flowing through the shield case 102b and the grid 102c. This means that the total discharge current is
This is because it can be considered that the value is the sum of the discharge currents to the grid 102c, the shield case 102b, and the photoreceptor 101.

[0036]

As is clear from the above, the present invention includes a discharge electrode, a shield member disposed to surround the discharge electrode, and a control electrode, and variably controls the voltage of the control electrode. In a scorotron charging device that controls the charging potential on a photoconductor, the charging device is equipped with a holding means for keeping the potential difference between the discharge electrode and the control electrode substantially constant, and a cleaning means that is driven under predetermined conditions. Prevents image deterioration caused by charging operation by stabilizing discharge from potential charging to high potential charging, and by avoiding non-uniform charging and constantly charging the photoreceptor with a stable potential over a wide range. can do.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a control system of a scorotron charging device according to the present invention and an explanatory diagram showing the surroundings of a photoreceptor.

FIG. 2 is an explanatory diagram showing a portion of the scorotron charging device according to the present invention that performs discharge.

FIG. 3 is a graph showing the characteristics of a scorotron charging device according to the present invention.

FIG. 4 is a graph showing the characteristics of a scorotron charging device according to the present invention.

FIG. 5 is a graph showing the characteristics of a scorotron charging device according to the present invention.

[Explanation of symbols]

102 Scorotron charging device
102a Discharge wire 102b Shield case
102c Grid 102c 103 Probe 113 High voltage power supply for discharge electrode
114 High voltage power supply for grid 115 Control circuit
116 Grid current detection circuit 117 Applied voltage correction amount calculation circuit 1
18 Surface potential detection circuit 119 Applied voltage correction amount calculation circuit 1
20 Barista

Claims (5)

[Claims] 1. A scorotron charging device comprising a discharge electrode, a shield member disposed to surround the discharge electrode, and a control electrode, and variably controls the voltage of the control electrode to control the charging potential of a photoreceptor. A scorotron charging device characterized in that a holding means is provided for holding the potential difference between the discharge electrode and the control electrode substantially constant. 2. Cleaning means for the discharge electrode and the control electrode; and a cleaning means for cleaning the control electrode under predetermined discharge conditions.
A detection means for detecting a current value flowing in one or both of the shield members or the photoreceptor, and a control means for driving and controlling the cleaning means when the current value becomes equal to or less than a predetermined value by the detection means. The scorotron charging device according to claim 1, characterized in that: 3. Cleaning means for the discharge electrode and the control electrode, and detection means for detecting the surface potential of the photoreceptor;
When the surface potential of the photoreceptor becomes equal to or less than a predetermined value by the detection means, driving and controlling the cleaning means for at least the discharge electrode, and when the surface potential of the photoreceptor becomes equal to or more than a predetermined value by the detection means. A scorotron charging device comprising: a control means for driving and controlling the cleaning means with respect to at least the control electrode. 4. A detection means for detecting a surface potential of the photoreceptor, and a voltage applied to the control electrode and/or a voltage applied to the discharge electrode according to the surface potential level detected by the detection means. The scorotron charging device according to claim 1, further comprising a control means for controlling the scorotron charging device. 5. A detection means for detecting a current value flowing through the discharge electrode, the control electrode, or the shield member, or a current value flowing through the photoreceptor; 2. The scorotron charging device according to claim 1, further comprising a control means for controlling the voltage applied to the control electrode and/or the voltage applied to the discharge electrode.