JP3000732B2 - 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 a corona discharge device used for an image recording apparatus such as an electrophotographic copying machine and a printer.

[0002]

2. Description of the Related Art Generally, in an image recording apparatus such as an electrophotographic copying machine or a printer, after a surface of a photosensitive drum is uniformly charged by a primary charger, an image is exposed to the photosensitive drum and the surface of the photosensitive drum is statically charged. An electrostatic latent image is formed, and the electrostatic latent image is developed by a developing device. Then, after the developed image formed on the surface of the photosensitive drum is transferred onto a recording sheet by charging of a transfer charger, the recording sheet on which the developed image has been transferred is charged by a separation charger, and then the surface of the photosensitive drum is charged. Separated from
An image is recorded by fixing a developed image on recording paper by a fixing device.

As described above, in an image recording apparatus such as the electrophotographic copying machine, a plurality of corona discharge devices utilizing corona discharge, such as a primary charger, a transfer charger, and a separation charger, are used.

Conventionally, the above-described corona discharge device 100 is shown in FIG.
2, a discharge wire 101 and a shield member 102 surrounding the discharge wire 101 with one surface open are provided, and the AC voltage obtained by superimposing a DC voltage on the discharge wire 101 by a high-voltage power supply device 103 is provided. By applying a high voltage or the like, a corona discharge is generated, and the recording paper is separated.

In the corona discharge device 100, an AC high voltage obtained by superimposing a DC voltage on the discharge wire 101 is applied from the high voltage power supply device 103 to the discharge wire 101 via the high voltage cord 104.

At this time, the high-voltage power supply device 103 is provided with an output voltage detection circuit and an output current detection circuit on the secondary side of the step-up transformer in order to output a constant voltage and a constant current. By detecting the output voltage and the output current by the voltage detection circuit and the output current detection circuit, the output control circuit controls on / off of the switching element, and keeps the output voltage and the output current constant.

[0007]

However, the above-mentioned prior art has the following problems. That is, in the corona discharge device 100, the high-voltage power supply device 10
3 is applied to the discharge wire 101 via the high voltage cord 104 to apply an AC high voltage obtained by superimposing a DC voltage. Therefore, electrostatic coupling occurs between the high-voltage cord 104 and the surrounding wiring or frame, and the like.
A leakage current is generated from a high voltage cord 104 to which an AC high voltage obtained by superimposing a DC voltage is applied to surrounding wiring or a frame. Then, the leakage current flows to the ground via a surrounding frame or the like, and the operating current Idyn to be detected by the output current detection unit of the high-voltage power supply device 103
In addition, as shown in FIG. 13, there is a problem that the error current is superposed as an error current via the ground and an error occurs in the detection value of the operating current Idyn. As described above, if an error occurs in the detected value of the operating current Idyn of the corona discharge device 100, the operating current Idyn of the corona discharge device 100 cannot be controlled with high accuracy, and the corona discharge device 100
Causes a problem that the image quality of an image obtained by an image recording apparatus or the like in which the image is used fluctuates or the image quality deteriorates.

In order to solve this problem, a high-voltage cord 104 having a shield capable of preventing a leakage current is considered as the high-voltage cord 104, and is actually used.

However, in this case, the high-voltage cord 104
When a high-voltage cord with a shield is used, not only does the cost of parts increase, but also the processing of the shield takes time, and as shown in FIG.
However, it is impossible to prevent the leakage current generated from the periphery 104a, 104b of the connector 04, and it is impossible to accurately detect the operating current Idyn of the corona discharge device 100.

In addition, inexpensive image recording apparatuses such as copying machines cannot use shielded high-voltage cords due to cost and the like, and must use ordinary high-pressure cords. Therefore, the high-voltage power supply device 103 detects only the operating current Idyn flowing to the member to be subjected to the corona discharge from the corona discharge device 100 and controls the operating current with high accuracy, as shown in FIG. By directly returning the current flowing from the discharge wire 101 to the shield member 102 to the power supply unit of the high-voltage power supply device 103 via the low-voltage cord 105 for returning the shield current, the shield current including the leakage current and the like is output. One that has been proposed to prevent it from flowing into has been proposed and has been used in practice.

However, even in this case, the high-voltage cord 104
Leakage leads to the leakage current, and this leakage current
As shown in FIG. 13, the operating current Idyn which flows into the ground via a surrounding frame or the like and is to be detected by the output current detecting unit of the high-voltage power supply device 103 is superposed as an error current via the ground as shown in FIG. However, there still remains a problem that an error occurs in the detected value of.

In order to solve the problem that the operating current Idyn of the corona discharge device 100 cannot be detected with high accuracy due to the leakage current, and to enable the operating current Idyn to be detected with high accuracy, the operating current is reduced. A device in which the leakage current is corrected at the time of detection has already been proposed (JP-A-1-279271).

In the device according to this proposal, the voltage applied to the discharge wire 101 of the corona discharge device 100 (Vpi
n) to a pulse width modulation (PWM) controller to switch the primary side of the high voltage circuit at a predetermined duty to control the output voltage on the secondary side, and apply this voltage to the discharge wire 101. This voltage causes a current to flow through the shield member of the corona discharge device 100 and the photosensitive drum. The current flowing into the surface of the photosensitive drum is compared as a voltage, and the comparison output is used to control a switching element such as a high-withstand-voltage type transistor.
When 00 has a grid electrode, control is performed so that the grid potential becomes a potential corresponding to the Vgrid remote. The secondary side output voltage of the high voltage power supply, that is, the voltage applied to the corona discharge device 100 is detected and monitored as Vout, and the current flowing to the surface of the photosensitive drum is detected and monitored as Id. The current to the side, that is, the shield currents Is and Id are added, and the total current It is fed back to the pulse width modulation (PWM) controller to change the duty, and the secondary side output voltage is changed by chopping with the switching element. Id is controlled to be constant.

Then, the AC component of the corona discharge device 100 is sampled, and a difference calculation processing unit calculates a difference between the sampling result and a target value in consideration of an error value due to a leakage current read from a target value table. Thereafter, the corona discharge device 10 is output from the output remote value calculation processing unit.
The AC component remote of 0 is transferred to the remote value output processing unit, and is fed back to the corona discharge device 100 via the D / A converter to control the output current to a predetermined value.

However, in the case of the device according to the above proposal,
Complicated correction operation due to leakage current, etc., is required, complicating the configuration of the apparatus and causing a significant increase in cost. Digital error correction must be set for each image recording apparatus. Has a new problem that it becomes complicated.

[0016]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art.
It is an object of the present invention to provide a corona discharge device that does not require complicated correction operation due to leakage current or the like, and that can detect and control an operation current with a very simple configuration and accurately.

That is, the present invention comprises a discharge wire and a shield member surrounding the discharge wire with at least one surface open, and generates a corona discharge by applying a high voltage to the discharge wire. ,
In the corona discharge device configured to detect an operation current flowing from the discharge wire to the member to be discharged and control the operation current, a high-voltage power supply unit for applying a high voltage to the discharge wire is integrated with the shield member. , And at least a part of the high-voltage power supply unit is covered with a conductive member, and the conductive member is electrically connected to the shield member, and a shield current flowing through the shield member and a leakage current flowing through the conductive member, It is configured to directly return to the high voltage power supply unit of the high voltage power supply unit without passing through the operation current detection unit.

[0018]

According to the present invention, a high-voltage power supply unit for applying a high voltage to a discharge wire is provided integrally with a shield member, and at least a part of the high-voltage power supply unit is covered with a conductive member. The member is electrically connected to the shield member, and the shield current flowing in the shield member and the leakage current flowing in the conductive member are directly returned to the high voltage power supply unit of the high voltage power supply unit without passing through the detection unit of the operation current. The high voltage power supply unit for applying high voltage to the discharge wire is provided integrally with the shield member, eliminating the need for a high voltage cord for applying high voltage from the high voltage power supply unit to the shield member. Thus, generation of leakage current from the high-voltage cord can be prevented. In addition, at least a part of the high-voltage power supply unit is covered with a conductive member, and the conductive member is electrically connected to the shield member. A shield current flowing through the shield member and a leakage current flowing through the conductive member are reduced by an operating current. Since it is configured to return directly to the high-voltage power supply unit of the high-voltage power supply unit without passing through the detection unit, the leakage current directly generated from the high-voltage power supply unit also detects the operating current together with the shield current flowing through the shield member. By directly returning to the high-voltage power supply unit of the high-voltage power supply unit without passing through, it is possible to prevent the influence of leakage current from flowing into the operating current detection unit with a very simple configuration, and to detect operating current with high accuracy Can be done.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

FIG. 2 shows an image recording apparatus to which the corona discharge device according to the present invention can be applied. In this image recording apparatus, after a surface of a photosensitive drum 1 is uniformly charged by a primary charger 2, an optical system 3 including a light source and a mirror is provided.
A latent image is formed on the surface of the photoreceptor drum 1 by exposing the image of the original through the developing device 4, and the electrostatic latent image is developed by the developing device 4. Then, after the developed image formed on the surface of the photosensitive drum 1 is transferred onto the recording paper 6 by charging the transfer charger 5, the recording paper 6 on which the developed image has been transferred is charged by the separation charger 7. An image is recorded by separating from the surface of the photosensitive drum 1 and fixing the developed image on the recording paper 6 by the fixing device 8.

The corona discharge device according to the present invention is used, for example, as the separate charger 7 and the like.

FIG. 1 shows an embodiment of a corona discharge device according to the present invention.

In the drawing, reference numeral 10 denotes a corona discharge device.
1, a metal shield member 12 surrounding the discharge wire 11 in a U-shaped cross section with one surface opened;
The shield member 12 is fixed to both ends in the longitudinal direction,
Insulating blocks 13 and 14 for holding both ends of the discharge wire 11 in a stretched state are provided. As shown in FIG. 3, a connection terminal 15 for applying a high AC voltage obtained by superimposing a DC voltage on the discharge wire 11 is provided at the outer end of the insulating block 13 toward the side. It is protruding.

The corona discharge device 10 generates a corona discharge by applying a high AC voltage obtained by multiplying a DC voltage by the high voltage power supply device 16 to separate recording paper. I have.

The high-voltage power supply 16 for applying a high voltage to the corona discharge device 10 is configured as shown in FIG.

In the drawing, T is a step-up transformer, and a predetermined DC voltage (for example, +24 V) is applied to one end of the primary winding N1 of the step-up transformer T, and the other end is The switching element Q is connected. A capacitor C is connected between the secondary winding N2 of the step-up transformer T and the winding.
From one end of the secondary winding N2, an AC high voltage is output via a resistor R.

The high-voltage power supply 16 has an output current detecting circuit 18 on the secondary side of the step-up transformer T in order to output a constant voltage and a constant current. By detecting the output voltage and the output current, the output control circuit 19 controls the on / off of the switching element Q to maintain the output voltage and the output current at constant values.

Further, in the high-voltage power supply device 16, FIG.
As shown in FIG. 1, the operating current I flowing through the recording sheet 6 as a member to be subjected to corona discharge from the corona discharge device 10
The current flowing from the discharge wire 11 to the shield member 12 is directly fed back to the power supply section of the high-voltage power supply device 16 in order to detect the dyn only and control the operating current with high accuracy. It is constituted so that it may not flow into a part.

FIG. 5 is a circuit diagram showing a main part of the high-voltage power supply device 16. As shown in FIG.

In FIG. 5, reference numeral 20 denotes an equivalent circuit of the corona discharge device. The equivalent circuit 20 of the corona discharge device includes an insulation resistance Rb which is air from the discharge wire 11.
, An operating current Idyn flows through the member to be discharged, and the member to be discharged is charged to a predetermined potential.
ost voltage drop and the discharge wire 11
From the shield member 1 via the capacitance C between the discharge wire 11 and the shield member 12 and the air resistance Rs in the air gap.
Flow to 2. The current flowing through the shield member 12 flows to one end 21 of the DC power supply of the power supply device 16 via the resistor R1. The operating current Idyn flowing from the discharge wire 11 to the ground via the member to be discharged is supplied to the operation amplifier 2 constituting the output current detection circuit 18.
2, an AC component and a DC component of the operating current Idyn are detected. The AC component and the DC component of the operating current Idyn detected in this way flow to the output control circuit 19 through the monitor box 23, and the output control circuit 19 controls the switching element Q to turn on and off. Idyn is maintained at a constant value.

In the figure, reference numeral 24 denotes a setting circuit provided on the operation panel or the like of the image recording apparatus for changing the set values of the AC and DC components of the output voltage.

Further, among the various components constituting the high-voltage power supply device 16, a step-up transformer T for generating a high voltage is particularly preferred.
As shown in FIG. 1, the circuit elements such as the capacitor C and the resistor R connected to the secondary winding N2 of the step-up transformer T are divided into one block as the high-voltage power supply unit 25 due to insulation and the like. Components. And
Components constituting another control circuit constituting the high voltage power supply device 16 are mounted on another printed wiring board 26 as a high voltage output control section.

Further, the high-voltage power supply unit 21 is provided inside a rectangular parallelepiped insulating case 27 made of synthetic resin or the like.
The step-up transformer T and the secondary winding N2 of the step-up transformer T
, And circuit elements such as a capacitor C and a resistor R connected thereto. The high-voltage power supply unit 21
As shown in FIG. 1, the outer peripheral surface of the insulating case 27 is entirely coated with a conductive paint 27a in which metal powder such as Al is dispersed, and the insulating case 27 itself forms a conductive shield. Has become.

In this embodiment, a high-voltage power supply unit for applying a high voltage to the discharge wire is provided integrally with the shield member, and at least a part of the high-voltage power supply unit is covered with a conductive member. The conductive member is electrically connected to the shield member, and the shield current flowing through the shield member and the leakage current flowing through the conductive member are directly returned to the high voltage power supply unit of the high voltage power supply unit without passing through the operation current detection unit. It is configured to be.

That is, as shown in FIG. 3, the shield member 12 of the corona discharge device 10 has one end in the longitudinal direction integral with the shield member 12 or the shield member 1.
A flat mounting portion 3 protruding as a member separate from 2
5 are provided.

As shown in FIG. 1, the high voltage power supply unit 21 is integrally mounted on the mounting portion 35. For example, as shown in FIG. 3, the high-voltage power supply unit 21 is mounted on the mounting portion 35 by attaching a fixing piece 36 projecting downward at one end of the high-voltage power supply unit 21 to the tip of the mounting portion 35. This is performed by screwing or bonding to the protruding fixing piece 37.

As shown in FIG. 6, the high-voltage power supply unit 21 is provided with a connection terminal 28 made of a coil spring for electrically connecting to the discharge wire 11 at the end on the shield member 12 side. The connection terminal 28 made of the coil spring is configured to be electrically connected to the connection terminal 15 connected to the discharge wire 11 by pressing.

Further, as shown in FIG. 1, the high-voltage power supply unit 21 is electrically connected to a conductive insulating case 23 by making direct contact with the shield member 12 via a lead wire or directly. Shield member 1
2 flows through the high-voltage power supply unit 21
Flows together with the leakage current flowing through the insulating case 23.

FIG. 7 is a circuit diagram showing a DC high-voltage power supply for applying a DC high voltage to the separation charger 5.

In the above configuration, the operating current is detected in the corona discharge device according to this embodiment as follows. That is, as shown in FIG. 1, the corona discharge device 10 applies an AC high voltage obtained by superimposing a DC voltage to the discharge wire 11 by the high-voltage power supply unit 21 of the high-voltage power supply 16, so that the discharge wire 11 , A corona discharge is generated to charge or discharge the member to be discharged.

At this time, the operating current Idyn flowing from the discharge wire 11 to the member to be discharged flows into the ground and flows through the ground to the output current detecting circuit 18 as shown in FIG. Thus, the operating current Idyn is detected. Then, the operating current Idyn
Is controlled by the output control circuit 19 so that the switching element Q becomes a predetermined value.

On the other hand, the leakage current leaking from the high-voltage power supply unit 25 of the high-voltage power supply unit 16 to the outside flows into the insulating case 27 of the high-voltage power supply unit 25 whose outside has been subjected to the conductive treatment. 5 flows to one end 21 of the DC power supply of the high-voltage power supply 16 together with the shield current Is flowing to the shield member 12 electrically connected to the insulating case 27, as shown in FIG. It does not flow into the circuit 18. Therefore, the leakage current does not become an error current when detecting the operation current Idyn, and only the operation current Idyn can be detected with high accuracy by the output current detection circuit 18 as shown in FIG.

As described above, in this embodiment, the shield member 12 is provided integrally with the high-voltage power supply unit 25 for applying a high voltage to the discharge wire 11, and the insulating case 27 of the high-voltage power supply unit 25 is electrically conductive. While covering with the paint, the conductive paint is electrically connected to the shield member 12, and the shield current Is flowing through the shield member 12 and the leakage current flowing through the conductive insulating case 27 are
The operating current Idyn is configured to return directly to the high-voltage power supply unit of the high-voltage power supply unit 25 without passing through the output current detection circuit 18.
In addition, since a high-voltage power supply unit 25 for applying a high voltage to the discharge wire 11 is integrally provided, a high-voltage cord for applying a high voltage from the high-voltage power supply unit 25 to the shield member 12 becomes unnecessary, and a high-voltage cord The occurrence of leakage current from the battery can be prevented. Further, at least a part of the high-voltage power supply unit 25 is made of an insulating case 2 having conductivity.
7 and electrically connects the conductive insulating case 27 to the shield member 12, and detects a shield current flowing through the shield member 12 and a leakage current flowing through the insulating case 27 by an output current detection circuit 18 of the operating current Idyn. Is passed directly back to the high-voltage power supply unit of the high-voltage power supply unit 25 without passing through the high-voltage power supply unit 25.
Of the operating current Idyn can be prevented from flowing into the output current detecting circuit 18 of the operating current Idyn with an extremely simple configuration by directly feeding back to the high voltage power supply unit of the high voltage power supply unit 25 without passing through the output current detecting circuit 18 of FIG. The operation current Idyn can be detected with high accuracy.

Second Embodiment FIGS. 8 and 9 show a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. In the embodiment, the high-voltage power supply unit is fitted and fixed to a mounting portion provided integrally with one end of the shield member.

That is, in this embodiment, FIGS.
As shown in FIG. 1, a rectangular parallelepiped mounting portion 30 having both ends opened at one end of the shield member 12 is integrally formed, and an insulating case 27 constituting the high-voltage power supply unit 16 is fitted and fixed to the mounting portion 30. It is supposed to be.
For this reason, as shown in FIG. 10, the side walls 31, 31 of the mounting portion 30 are provided with claw portions 32, 32 integrally formed by cutting out a part of the side walls 31, 31 to protrude inward. In addition, the side walls 33, 33 of the insulating case 27 are provided with concave portions 34, 34 which are relatively engaged with the claw portions 32, 32.
Are formed. The high-voltage power supply unit 16
By inserting the insulating case 27 into the mounting portion 30, the claw portions 32, 32 provided on the side walls 31, 31 of the mounting portion 30 are turned into the concave portions 34, provided on the side walls 33, 33 of the insulating case 27. The high-voltage power supply unit 16 is integrally attached to the attachment portion 30 by engaging relatively with 34.

The other constructions and operations are the same as those of the first embodiment, and a description thereof will be omitted.

Third Embodiment FIG. 11 shows a third embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. , High-voltage power supply unit 25 of high-voltage power supply 16 and printed wiring board 2 of high-voltage output control unit
6 are integrally formed on the insulating substrate 40, and the surface of the insulating substrate 40 has leakage in a region corresponding to a portion where the high-voltage member such as the step-up transformer T of the high-voltage power supply unit 25 is disposed. A conductive pattern 41 for current feedback is formed, and the conductive pattern 41 is electrically connected to the shield member 12 of the corona discharge device 10.

The other constructions and operations are the same as those of the first embodiment, and the description thereof will be omitted.

[0049]

According to the present invention, there is provided a corona capable of accurately detecting an operating current and controlling the same with a very simple configuration, eliminating the need for complicated correction operations due to leakage current and the like. A discharge device can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a corona discharge device according to the present invention.

FIG. 2 is a configuration diagram showing an image recording apparatus to which a corona discharge device according to the present invention can be applied.

FIG. 3 is an exploded perspective view showing one embodiment of a corona discharge device according to the present invention.

FIG. 4 is a circuit diagram showing a circuit for applying a high voltage to the corona discharge device according to the present invention.

FIG. 5 is a block diagram showing a control circuit for applying a high voltage to the corona discharge device according to the present invention.

FIG. 6 is a cross-sectional view showing a connection portion for applying a high voltage to the corona discharge device according to the present invention.

FIG. 7 is a block diagram showing a control circuit for applying a high voltage to another corona discharge device.

FIG. 8 is a perspective view showing a corona discharge device according to another embodiment of the present invention.

FIG. 9 is an exploded perspective view showing a corona discharge device according to another embodiment of the present invention.

FIGS. 10 (a) and 10 (b) are perspective views showing mounting portions of a corona discharge device according to another embodiment of the present invention.

FIG. 11 is a plan view, a front view, a bottom view, and a main part plan view showing a corona discharge device according to still another embodiment of the present invention.

FIG. 12 is a perspective view showing a conventional corona discharge device.

FIG. 13 is a graph showing current control in a conventional corona discharge device.

FIG. 14 is a perspective view showing a connecting portion in a conventional corona discharge device.

FIG. 15 is a circuit diagram showing a connection circuit in a conventional corona discharge device.

FIG. 16 is a graph showing current control in the corona discharge device according to the present invention.

[Explanation of symbols]

11 discharge wire, 12 shield member, 25 high voltage unit, 27 insulating case, 27a conductive member

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 15/14 G03G 15/16 G03G 21/06 H01T 19/00

Claims (1)

(57) [Claims] 1. A discharge wire comprising: a discharge wire; and a shield member surrounding the discharge wire in a state where at least one surface of the discharge wire is open. A corona discharge is generated by applying a high voltage to the discharge wire. In the corona discharge device which detects the operating current flowing from the member to be discharged to control the operating current, the shield member is provided integrally with a high-voltage power supply unit for applying a high voltage to the discharge wire. At least a part of the high-voltage power supply unit is covered with a conductive member, and the conductive member is electrically connected to the shield member. A shield current flowing through the shield member and a leakage current flowing through the conductive member are reduced by an operating current. Corona discharge characterized by returning directly to the high-voltage power supply unit of the high-voltage power supply unit without passing through the detection unit Electrical equipment.