JPS6154879A - Reducing method of radiation noise of high voltage device - Google Patents

Abstract

PURPOSE:To reduce high band radiation noise by coupling high frequency impedance element with the high voltage supply section or return section of a high voltage power source. CONSTITUTION:A ferrite bead 4 is mounted as a high band impedance element at electric leads (high voltage power supply section) between the capacitor C1 of a high voltage power source and a current limiting resistors R1, and ferrite beads 5, 6 are mounted as high band impedance element at electric leads between the resistor R1 and the tungsten electrode 21. A capacity is formed between a DC nonearth electric lead and a case 1a by a penetrating capacitor 8 provided in the case 1a of the power source 1. Thus, a high band radiation noise generated in the current loop of a transformer T1 is suppressed and absorbed by the beads 4-6, and biased to a device via the capacitor 8.

Description

[Detailed Description of the Invention] ■Technical Field The present invention relates to a power supply device that supplies high voltage to a charging and neutralizing charger (corona discharger) of a copying machine, a power supply device that supplies high voltage to a developing device of a copying machine, and other devices. The present invention relates to prevention of radiation noise of a similar high voltage power supply and radiation noise generated by an electrode device connected to the high voltage power supply.

(2) Prior Art For example, a conventional high voltage power supply device for supplying high voltage to a corona discharger of a copying machine is installed as shown in FIG. In this case, the DC voltage is converted into AC by the DC-AC converter 7 and applied to the primary winding of the step-up transformer T1. The high voltage AC of the secondary winding of the step-up transformer T1 is connected to the diode DI.
rectified by , smoothed by capacitor CI and resistor R2,
It is applied to the corona discharger 2 through the resistor R1.

The resistor R1 is a current limiting resistor (protective resistor), and when the discharge current increases due to leakage between the electrodes 21-23, abnormal discharge, etc. in the corona discharger 2, the voltage drop across the resistor R1 becomes large, suppressing the discharge current and increasing the voltage between the electrodes 21 and 23. Reduce the voltage between 21 and 23. That is, the resistor R1 is used to prevent electric shock and to prevent abnormal discharge.

This type of corona discharger 2 generates radiant noise.

To explain this, the tungsten electrode 21 and the counter electrode 2
When a normal AC high voltage for corona discharge is applied between 3 and 3, the relationship between the applied voltage 1 voltage and the discharge current becomes as shown in FIG. In the figure, V is the applied voltage and i is the discharge current. n is an induced current, and the tungsten discharge electrode 21 and the counter electrode 2
This is believed to be caused by stray capacitance between the two (for example, the conductive f! layer of the photoreceptor drum). Note that the current waveform i is obtained by connecting a low resistor between the counter electrode and the equipment ground, and looking at the voltage across the low resistor.

As shown in Fig. 8, the induced current n is at the peak of the current i.
That is, a high-frequency pulse (Trichel pulse) appears, and its frequency is a high frequency ranging up to 10 MHz.

Similarly, when applying a DC high voltage to the corona discharger 2 as shown in FIG. 7, a similar high-frequency pulse appears,
Radiation noise is also generated from a switching element (not shown) of the DC-AC converter 7.

These radiated noises often propagate to other electrical circuits, either through electrical leads or through space, and have an adverse effect.

(1) Purpose The present invention aims to reduce the radiation noise of a high-voltage power supply and the radiation noise generated by an electrode device connected to the high-voltage power supply.

■Description In order to achieve the above object, in the present invention, an impedance element for high frequency is coupled to the high voltage power supply part of the high voltage power supply device or to the return path of the high voltage power supply, and this impedance element is used to Suppress radiated noise.

In one embodiment of the invention, the impedance element is a ferrite bead.

In another embodiment of the invention, a high frequency bypass capacitor is inserted between the high voltage supply and the equipment ground.

In another embodiment of the present invention, an air hole in an equipment earthing case of an electrode device such as a corona discharger is used as a conductive mesh to earth the equipment.

In a preferred embodiment of the present invention, the core of the step-up transformer of the high-voltage power supply is further grounded to equipment ground.

In a preferred embodiment of the present invention, the case of the high-voltage power supply device is further used as a conductor to ground the equipment.

Further, in a preferred embodiment of the present invention, a feedthrough capacitor is used at the DC input terminal of the high voltage power supply, and the ground pole of the capacitor is connected to the equipment ground.

In another embodiment of the present invention, an impedance element is inserted between the conductor to be grounded and the ground of the high-voltage power supply.

This will be explained below with reference to the drawings.

FIG. 1a shows an apparatus configuration for implementing one embodiment of the present invention. In this example, a ferrite bead 4 is attached as a high-frequency impedance element to the electrical lead (high-voltage power supply part) between the capacitor C1 and current-limiting resistor R1 of the high-voltage power supply 1, and Ferrite beads 5 and 6 are attached as high-frequency impedance elements to the electrical leads (high-voltage power supply part) between them.

FIG. 1b shows the case 18 of the high voltage power supply device 1 shown in FIG. 1a. The case 1a is a conductor, to which a device ground end of a high-voltage power supply circuit is connected, as well as a device ground lead for DC input. Connect a feedthrough capacitor (feed shield) to the non-ground lead of the DC input.
rough capacitor) 8 are combined. A conductive sleeve serving as an equipment ground electrode of the feedthrough capacitor 8 passes through the case 1a, and a flange of the sleeve is fixed and connected to the case 1a. A dielectric and an electrical lead pass through the conductive sleeve and are connected to the DC-AC converter 7. A capacitance is formed between the DC non-grounded electrical lead and case 1a by the feedthrough capacitor 8, and this capacitance is caused by the high I of the electrical lead.
s: Bypass radiated noise to case 1a.

The core of the external pressure transformer T1 is equipment grounded.

In this embodiment, high-frequency radiation noise generated or induced in the current loop from the secondary coil of the transformer T1 to the equipment ground via the corona discharger 2 is caused by the ferrite bead 4,
5 and 6, the high-frequency radiation noise induced in the core of the step-up transformer T1 is bypassed to the equipment ground, and the high-frequency radiation noise induced in the DC-AC converter 7 and the converter 7 are suppressed and absorbed. High-frequency radiation noise generated by switching elements, etc., is bypassed to equipment ground by a feed-through capacitor 8, and high-frequency radiation noise that attempts to propagate through the DC input line or space is reduced.6 Figure 2a shows the present invention. 2 shows an apparatus configuration for implementing the method in another embodiment. In this case, ferrite beads 15 and 16 are attached to the high voltage power supply return lead (connected to the case 1a of the device 1) of the high voltage power supply device 1 as high frequency impedance elements. Note that R3 is a low resistor for feedback of the discharge current, and the constant current $
In case of control, the voltage of this resistor R3 is applied to the control circuit. C2 is a capacitor that serves as a bypass filter during current detection. FIG. 2b shows the connection relationship between resistor R3 and capacitor C2 and device case la. The equipment case 1a is equipment grounded.

In this example, the return loop of the high voltage supply is connected to the counter electrode 22.
- Equipment earth case 1a - Resistor R3 - Secondary coil of step-up transformer TI, in this return loop from the secondary coil of transformer Tl via corona discharger 2 by means of ferrite beads 15 and 16 The high-frequency radiation noise generated or induced in the current loop leading to FA 'jJ is suppressed and absorbed, and the
The high-frequency radiation noise induced in the DC-AC converter 7 and the high-frequency radiation noise generated by the switching elements of the converter 7 are bypassed to the equipment ground, and the high-frequency radiation noise induced in the DC-AC converter 7 and the high-frequency radiation noise generated by the switching elements of the converter 7 are bypassed by the feed-through capacitor. (Similar to 8 in Fig. 1b) is bypassed to equipment ground, and high-frequency radiation noise that attempts to propagate through the DC input line or space is reduced.

FIG. 3a shows an arrangement for implementing the invention in another embodiment;
1a'? Indicates s formation. In this case, a high-frequency impedance element L (similar to ferrite bead 4 in Figure 1a, or something else) is coupled to the high-voltage power supply lead, and a high-frequency impedance element L (similar to ferrite bead 4 in Fig. ) is connected with a high-frequency bypass capacitor C3. In this example, high-frequency radiation noise generated or induced in the current loop from the secondary coil of the transformer T1 to the equipment ground via the corona discharger 2 is suppressed and absorbed by the impedance element, and the capacitor C3 is used to ground the equipment. The high-frequency radiation noise induced in the core of the step-up transformer T1 is bypassed to the equipment ground,
In addition, the high-frequency radiation noise induced in the DC-AC converter 7 and the high-frequency radiation noise generated by the switching elements of the converter 7 are removed by a feed-through capacitor (similar to the one 8 shown in Figure 1a). This reduces high-frequency radiated noise that is bypassed to equipment ground and tries to propagate through the DC input lead or space.

Note that the output lead 3 may be a resistance wire instead of the resistor R2. Further, the lead 3 may be a high voltage shielded cable. Instead of capacitor C3 or capacitor C
3, as shown in Figure 3b, the high voltage output end (3)
A feed-through capacitor may also be used for this purpose, or the capacitor C3 may be attached to the device earth case 23 of the corona discharger 2, or a feed-through capacitor may be coupled to the case 23.

When connecting a feedthrough capacitor to the case 23 of the corona discharger 2, electric charge accumulates in the feedthrough capacitor when the case 23 of the corona discharger 2 is removed from the device 1.
Connect the discharge resistor in parallel to the feedthrough capacitor. A feedthrough capacitor may be coupled to a connector on the side plate of the copying machine main body, and a detachable connector for the corona discharger 2 may be attached to this connector.

There are various shapes of the case 22 of the corona discharger 2. Some examples are shown in Figures 4a, 4b and 4c. In both of these figures, a low-velocity air current is generated from the tungsten discharge pole 21 toward the counter electrode 23. This is called corona wind. FIG. 4a takes into consideration the flow of air in the copying machine.

When either the shape shown in FIG. 4b or 4c is selected, in the shape shown in FIGS. 4b and 4c, there is no back surface of the case 22, or there is an air hole on the back surface, so radiant noise enters the space through there. is emitted. Therefore, as a countermeasure, in the shapes shown in Figures 4b and 4C, the back space (opening, hole) of the case 21 is used as a mesh-like conductor to ground the equipment in the same way as the main body of the case 22, thereby controlling the ion flow and reducing radiation noise. balance the reduction of Note that if the ion flow is blown away by ordinary wind, effective charging of the photoreceptor will not be achieved. When there is little wind, photoreceptors (especially organic photoreceptors)
Deterioration is likely to occur.

If permitted by equipment design, the device case 1a is connected to a floating ground via a high-frequency impedance element, as shown in FIG. 5a. Alternatively, the equipment ground end of the high voltage power supply circuit is connected to the device case 1a via a high-frequency impedance element, and the case 1a is grounded. In any of these cases, the ground inflow current of high-frequency radiation noise is reduced.

FIG. 6 shows a device configuration for carrying out another embodiment of the present invention. This example is for reducing the radiation noise of the dry developing device 24 of a copying machine.

In the dry type developing device 24, regardless of whether it is a -component type or a two-component type, a developing cylinder and a stirring blade 25 are mechanically rotated in order to agitate and replenish toner carrier. Note that 23 is a photosensitive drum.

As a result, the toner carrier is triboelectrically charged and operates as part of the image forming mechanism. To this end, the developing device 24 generates electrical energy, and as a result, when charged to a high voltage, it discharges to nearby members. As a result, radiation noise occurs.

On the other hand, there is a development voltage application method in which a development control voltage is externally applied to the development electrode. There are three methods for applying this developing voltage: a floating method, a fixed voltage method, and a variable voltage method, and the applied voltage is a direct current.

There are various types such as pulse, alternating current, pulsating current, and alternating pulse.

The high voltage power supply device 1 shown in FIG. 6 applies direct current to a developing electrode. In this example, in order to reduce radiated noise, Ferray 1-bead 4 is attached to the high voltage power supply lead. Note that the various types of radiation noise countermeasures described above are used in combination.

What is special about this example is that the varistor BR is connected between the high voltage power supply lead and the equipment ground. The breakdown voltage of this varistor BR is a value slightly larger than the maximum value of the voltage applied during steady state. This varistor BR limits the voltage applied to the developing electrode to below its breakdown voltage and prevents abnormal discharge to the photoreceptor. If abnormal discharge occurs, the photoreceptor will deteriorate.

Abnormal discharge tends to occur, for example, when atmospheric pressure is low.

It is also good to connect a varistor to the doctor blade, developing case, stirring blade, etc.

(2) Effects As explained above, according to the present invention, high-frequency radiation noise generated or induced in the high-voltage power supply device or the electrode device □ receiving power from the high-voltage power supply device is reduced.

[Brief explanation of drawings]

FIG. 1a is an electric circuit diagram showing the configuration of a device implementing the present invention in one embodiment, and FIG. 1b is a sectional view showing the relationship between the case 1a of the high voltage power supply device 1 shown in FIG. 1a and the input/output lines of the device 1. It is. Fig. 2a is an electric circuit diagram showing the configuration of a device implementing the present invention in another embodiment, and Fig. 2b shows the connection relationship between the case 1a of the high voltage power supply 1 shown in Fig. 2a and the equipment ground lead. FIG. Fig. 3a is an electric circuit diagram showing the configuration of a device implementing the present invention in another embodiment, and Fig. 3b shows the connection relationship between the case 1a of the high voltage power supply 1 shown in Fig. 3a and the high voltage output line. FIG. Figures 4a, 4b and 4c are cross-sectional views of the corona discharger, respectively. FIGS. 5a and 5b are cross-sectional views showing the connection relationship between the case 1a of the high-voltage power supply 1 and equipment ground in a certain embodiment of the present invention. FIG. 6 is an electrical circuit diagram showing a device configuration for implementing another embodiment of the present invention. FIG. 7 is an electrical circuit diagram showing the configuration of a conventional high voltage power supply device. FIG. 8 is a graph showing the correlation between the voltage waveform and the current waveform when an alternating current voltage is applied to the corona discharger 2 shown in FIG. 7. 1: High voltage power supply 1a: Case 2: Corona discharger 21: Tungsten discharge electrode 22
: Case 23: Counter electrode 3: High voltage power supply leads 4.5, 6, 15, 16: Ferrite beads (high frequency impedance element) 7: DC-AC converter 8: Feedthrough capacitor C3: Capacitor (high frequency impedance element) )L: High frequency impedance element

Claims (10)

[Claims] (1) A high-voltage device that reduces high-frequency radiation noise of the high-voltage power supply and electrode device by coupling a high-frequency impedance element to the current loop connecting the high-voltage device and the electrode device to which high voltage is applied. How to reduce radiated noise. (2) A method for reducing radiated noise of a high-voltage device according to claim (1), wherein the current loop is a high-voltage feeder line insulated with respect to equipment ground. (3) A method for reducing radiated noise of a high-voltage device according to claim (1), wherein the current loop is a return path to equipment ground of the high-voltage device. (4) Claims (1), (2), or (3) above, wherein the impedance element is a ferrite bead.
Method for reducing radiated noise of high voltage equipment as described in . (5) A capacitor for high frequency bypass is inserted between the current loop and the device ground.
), (2), or (3), a method for reducing radiation noise of a high voltage device. (6) The air hole of the device earthing case of the electrode device is used as a conductive mesh to ground the device.
A method for reducing radiation noise of a high voltage device as described in item 1), item (2), or item (3). (7) A method for reducing radiation noise of a high voltage device as set forth in claim (1), (2) or (3), wherein the core of the step-up transformer of the high voltage power supply device is grounded. (8) A method for reducing radiation noise of a high-voltage device as set forth in claim (1), (2), or (3), in which the case of the high-voltage power supply device is used as a conductor to ground the device. (9) A feed-through capacitor is used at the DC input end of the high-voltage power supply device, and the grounding pole of the capacitor is grounded to the device, as described in Claims (1), (2), or (3) above. , a method for reducing radiated noise in high voltage equipment. (10) The method according to claim 1, 2, or 3, wherein an impedance element is inserted between the conductor to be grounded and the ground of the device of the high-voltage power supply device. Method for reducing radiated noise of high voltage equipment.