JPS6294868A - Electronic copying machine - Google Patents

Abstract

PURPOSE:To obtain a stable corona discharging current even at a part which is easily stained regardless of temperature, humidity, and atmospheric pressure by using a high voltage power source which is brought under constant current control with the discharging current of a corona discharger for monitoring as the power source for a practical corona discharger. CONSTITUTION:The discharging current from a corotron 1 for monitoring a shield current is measured by a shield current measurement part 3' and a high voltage power supply part 4 is brought under constant-current feedback control through a voltage control part 41, so that a stable and proper current is supplied from a supply part. Therefore, when the supply part 4 is used as the power source for the charge corotron 2, transfer corotron 5, cleaning corotron 6, discharge corotron 7, etc., of the practical discharger in a copying machine, the stable corona discharging current is obtained even at a part which is easily stained regardless of temperature, humidity, atmospheric pressure, etc.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to high-voltage power supply control for a corona discharger of an electronic copying machine, and is particularly applicable to fluctuation factors such as changes in temperature, humidity, and atmospheric pressure, and dirt inside the discharger. This invention relates to the control of a common high voltage power supply output to obtain a stable discharge current.

[Conventional technology]

In an electronic copying machine, a corona discharger is used in each process such as charging a photosensitive drum, transferring a toner image, cleaning the photosensitive drum, and removing static electricity. Each corona discharger uses a high voltage power source that is individually controlled at constant voltage or constant current as a high voltage power source for corona discharge.

FIG. 2 shows a schematic diagram of a corona discharger and its power supply used in a conventional electronic copying machine. In the figure, 10 is a photosensitive drum, 2 is a charge corotron, 12 is a high voltage power supply for the charge corotron, 5 is a transfer corotron, 15 is a high voltage power supply for the transfer corotron 5, 6 is a pre-cleaning corotron, and 16 is a pre-cleaning・Corotron 6
7 is a high voltage power supply for the static elimination corotron, and 17 is a high voltage power supply for the static elimination corotron. In Figure 2, each corotron uses its own high-voltage power supply, but these power supplies are either controlled to provide a constant voltage for each corotron, or are controlled to have a constant current so that the discharge current of each corotron is constant. It is carried out.

In a corona discharger using a constant voltage power supply, the corona wire voltage is controlled to be kept constant at all times, so the discharge current tends to increase or decrease due to changes in temperature, humidity, or atmospheric pressure. In other words, in general, discharge tends to occur when the temperature is high, discharge occurs easily when the humidity is low, and even more easily discharges when the atmospheric pressure is low. If you use a constant voltage control power supply, it may discharge too much and cause leaks.
It can even cause trouble. In addition, the density of the copied image may decrease or blur due to the above-mentioned increase or decrease in the discharge current, paper jams may occur on copy paper due to fluctuations in the output of the static eliminator for paper peeling, and cleaning may occur due to fluctuations in the output of the static eliminator before cleaning the photosensitive drum surface. Problems such as defects may occur.

[Problem that the invention seeks to solve]

Compared to constant-voltage controlled power supplies, electronic copiers that use constant-current controlled power supplies have more stable output against changes in temperature, humidity, and atmospheric pressure, and do not suffer from the problems described above. The discharge current tends to fluctuate due to localized contamination, and there are problems such as the output increasing too much and causing arc discharge.

The outline is explained in FIG. In the figure, lo is a photosensitive drum, 30 is a corona discharger, 31 is a corona wire, 3
2 indicates the shield, and 33 indicates lq of dust, paper powder, etc. attached to the shield 32. Generally, the shield 32 of the corona discharger 3o installed near the photosensitive drum 1o is grounded, and a high negative voltage is applied to the corona wire 31, so that an electric force is uniformly applied to the shield 32 and the surface of the photosensitive drum 1o from the corona wire 31. It has a structure that creates lines. However, when dirt 33 adheres to the shield 32, electric charge is accumulated on it, and the potential difference between the corona wire 31 and the dirt 33 adhering to the shield 32 causes a potential difference between the corona wire 31 and the other parts of the shield 32 and the surface of the photosensitive drum 10. The potential difference between Then, the lines of electric force are concentrated in areas where the potential difference is large, so the lines of electric force become sparse in areas where charges are accumulated.

If the electric lines of force within the shield 32 become dense or dense in this way, the discharge conditions change, and it becomes necessary to apply an extra voltage to maintain a constant current. As a result, the top of the photosensitive drum 10 will be overcharged.

Conventional equipment has a high voltage power supply for each corona discharger as shown in Figure 2, so if the corona discharger is installed in a place where the inside of the discharger is relatively free of dirt, the above problem will not occur. However, if the corona discharge 23 is installed in a place where there is a lot of paper dust or toner, such as a transfer corotron or a static elimination corotron, the paper dust will adhere to the inside of the shield and the current in that area will decrease, so a constant current should be passed through the entire discharger. If this happens, problems such as high voltage and leakage current will occur.

[Means and effects for solving the problems] In order to solve the above-mentioned problems, the present invention provides a corona discharger for shield current monitoring using constant current control, which prevents contamination of electronic copying machines. A constant current controlled high voltage power supply that controls the current to be constant is used as a high voltage power supply for a corona discharger provided elsewhere in the electronic copying machine.

The present invention provides constant current control of a high-voltage power supply based on the shield current of a monitor corona discharger that rarely causes tTi, and simultaneously controls the high-voltage power supply of corona dischargers in other parts of the electronic copying machine. , each corona discharger can provide stable output even with changes in temperature, humidity, and atmospheric pressure. Furthermore, a stable discharge current can be obtained even in a corona discharger installed in a location where lη leakage is likely to adhere inside the discharger.

〔Example〕

The present invention will be described with reference to the embodiments shown in FIGS. 1, 4, and 5.

(1) First embodiment In FIG. 1, 1 is a corotron for shield current monitoring, 2 is a charge corotron for a photosensitive drum, 3 is a shield current measuring section, and 4 is a high voltage power supply section (hereinafter referred to as HVPS section). ), 41 is a voltage control section, 42 is a transformer, 43 is a rectifier, 5 is a transfer corotron, 6 is a pre-cleaning corotron, and 7 is a static elimination corotron. The shield current monitor corotron 1 is for measuring current for constant current control according to the present invention, and is installed in the copying machine near the optical system, where dust such as paper dust and toner are less likely to adhere. The shield current measuring section 3 measures the shield current of the shield current monitor corotron 1, which has little dirt. HV
The SP section 4 includes a voltage control section 41, a transformer 42, and a rectifier 43, and electronically converts a high voltage controlled so that the shield current is constant based on the shield current value inputted from the shield current measurement section 3. It supplies each corona discharger in the copying machine. The voltage control unit 41 includes a reference unit that provides a reference value and a comparison unit, which compares the input current input from the shield current measurement unit 3 with the reference value, and if the input current is large, the output voltage is decreased and the input current is If it is smaller, the output voltage is controlled to be larger. The rectifier 43 is connected to the secondary side of the transformer 42, thereby obtaining a negative DC output, which is feedhacked to the shield current monitor corotron 1, charge corotron 2, and transfer It is applied to the corotron 5 and the pre-cleaning corotron 6.

Further, the AC output from the secondary side of the transformer 42 is applied to the static eliminating corotron 7. As a result, the power supply for each Coro1-Ron can be a constant high voltage power supply with constant current control.
The constant current controlled power supply voltage is also applied to the transfer corotron 5, pre-cleaning corotron 6, and static elimination corotron 7, to which paper dust and toner tend to adhere inside the shield.

This makes it possible to improve the drawbacks caused by local contamination as described above.

In the above explanation, an example was explained in which the shield current monitor corotron 1 was used.
Based on this, the shield current of δ is determined and the HVPS
A similar effect can be obtained even if the section 4 is controlled with a constant current.

(2) Second embodiment A second embodiment of the present invention will be described based on FIG.

In Figure 4, 20 is a charge scorotron, 21
is corona wire, 22 is shield, 23 is grid, 3
' is a discharge current measuring section, and 8.9 is a varistor. In this embodiment, the shield 2 of the charge scorotron 20 is
The discharge current to the grid 2 and the grid 23 is measured by the discharge current measurement section 3' via the varistor 8, and the value is input to the voltage control section 41 of the HVPS section 4.
The output is controlled so that the discharge current of 0 is constant, and the output voltage is applied to the scorotron 20, the transfer corotron 5, and the precleaning corotron 6.
, is applied to the static eliminating corotron 7.

By connecting the varistor 9 here, charging and
The power supply voltage value between the scorotron 20, transfer corotron 5, and precleaning corotron 6 can be changed while controlling the shield current at a constant current.

With such a configuration, it is possible to obtain a discharge current that is more stable against changes in temperature and humidity compared to conventional constant voltage control methods and constant current control methods. FIG. 6 shows an example of the discharge current of the transfer corotron. 6th
In the figure, the three points on the horizontal axis are all 5 points at low temperature and low humidity.
°C relative humidity 20%, 20 °C 55%, high temperature and high humidity 30
It shows three-stripe property at 90% °C, and the vertical axis shows the magnitude of the transfer current flowing toward the photosensitive drum under that condition. (al is the conventional constant voltage control method, (bl is the conventional constant current control method in which a power supply is provided for each corotron), (C1 is the constant shield current method of this embodiment. These current change rates are
Shown in the table.

As is clear from Table 1, Figure 6, and Table 1, the current change rate (ratio of the difference between the maximum current value and the minimum current value of the three-line structure to the maximum current value) is very small. It can be seen that a stable current is obtained. Especially constant current method (BL
is basically the same as the method of the present invention (C1), but it is thought that the former method differs from the method of the present invention because the inside of the transfer corotron 5 is partially dirty. By using the less dirty charge scorotron 20 as the corotron that monitors the shield current, the outputs of the transfer corotron 5, precleaning corotron 6, and static elimination corotron 7, which are located in areas with a lot of dirt, are less affected by dirt. I was able to make it stable.

(3) Third embodiment FIG. 5 shows yet another embodiment of the invention.

In this embodiment, a rectifier 4 is provided in the HVPS section 4'.
A rectifier 44 of opposite polarity to 3 is provided and connected to the secondary side of the transformer 42 and its output voltage is applied to the precleaning corotron 6. As a result, the polarity becomes opposite to that of the output voltage applied to the transfer corotron 5, and its operation becomes perfect.

(Effects of the Invention) According to the present invention, it is possible to obtain a stable discharge current of the corona discharger of an electronic copying machine, which is less susceptible to changes in temperature, humidity, and atmospheric pressure, or to localized dirt inside the discharger. We can provide high quality copying machines.

[Brief explanation of drawings]

FIG. 1 is a detailed explanatory diagram of the present invention, FIGS. 2 and 3 are explanatory diagrams of a conventional example, FIGS. 4 and 5 are explanatory diagrams of other embodiments of the present invention, and FIG. It is a characteristic explanatory diagram of the invention. 1 --- Shield current monitor corotron 2 --- Charge corotron 3 --- Shield current measuring section 4.4' --- High voltage power supply section 5 --- Transfer corotron 6--7" Refreshing corotron 7 - Static elimination corotron 8.9 - Varistor 10 - One photosensitive drum

Claims (2)

[Claims] (1) In an electronic copying machine that uses a corona discharger, a high voltage power supply whose constant current is controlled by the discharge current of the monitoring corona discharger is provided, and this high voltage power supply whose constant current is controlled is connected to other parts within the electronic copying machine. An electronic copying machine characterized in that it is connected as a high voltage power source to a corona discharger. (2) The electronic copying machine according to claim 1, wherein a corona discharger for charging a photosensitive drum is used as the monitor corona discharger.