JPH05150613A - Corona discharge device - Google Patents

Abstract

PURPOSE:To provide a corona discharge device in which complicated correcting action associated with a leakage current, etc., is eliminated and which can accurately detect and control a working current by extremely simple constitution. CONSTITUTION:A high voltage power source unit 25 for impressing high voltage on a discharge wire 11 is provided integrally with a shield member 12, at least a part of the unit 25 is covered with a conductive member 27a, and the member 27a is electrically connected to the member 12 so that a shield current flowing to the member 12 and the leakage current flowing to the member 27a may be directly fed back to the high voltage power source part of the unit 25 without passing through the detection part of the working current.

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 in image recording devices such as electrophotographic copying machines and printers.

[0002]

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

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

Conventionally, the corona discharge device 100 is shown in FIG.
2, a discharge wire 101 and a shield member 102 that surrounds the discharge wire 101 with one surface open is provided, and the discharge wire 101 has a DC voltage superimposed by a high-voltage power supply device 103. It is configured to generate a corona discharge by applying a high voltage or the like to separate recording sheets.

By the way, in the corona discharge device 100, a high voltage of alternating current obtained by superposing the direct current voltage on the discharge wire 101 is applied from the high voltage power supply device 103 through 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 the output voltage and the output current are held 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 configured to apply an alternating high voltage obtained by superposing the direct current voltage to the discharge wire 101 via the high voltage cord 104. Therefore, electrostatic coupling occurs between the high voltage cord 104 and the surrounding wiring or the frame,
A leakage current is generated from the high-voltage cord 104 to which an alternating high voltage obtained by superimposing a direct current voltage is applied to surrounding wiring or a frame. Then, this leakage current flows into the ground through the 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 in that the detection value of the operating current Idyn has an error due to being superimposed as an error current via the ground. As described above, if an error occurs in the detected value of the operating current Idyn of the corona discharge device 100, it becomes impossible to control the operating current Idyn of the corona discharge device 100 with high accuracy, and the corona discharge device 100 becomes inaccurate.
However, the image quality of an image obtained by the image recording device or the like used may vary or the image quality may deteriorate.

Therefore, in order to solve this problem, it is conceivable to use a high voltage cord 104 with a shield capable of preventing a leakage current as the high voltage cord 104, and it is actually used.

However, in this case, the high voltage cord 104
When a high-voltage cord with a shield is used as the above, not only the cost of the parts is high, but also the treatment of the shield is troublesome, and as shown in FIG.
There is a problem in that the leakage current generated from the connector periphery 104a and 104b of No. 04 cannot be prevented, and the operating current Idyn of the corona discharge device 100 cannot be detected with high accuracy.

Further, in an inexpensive image recording apparatus such as a copying machine, a shielded high-voltage cord cannot be used because of cost reasons, and a normal high-voltage cord must be used. Therefore, the high-voltage power supply device 103 detects only the operating current Idyn flowing in the member to be subjected to corona discharge from the corona discharging device 100 and controls the operating current with high accuracy. Therefore, 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 or the like is output current detection unit. The one configured so as to prevent the leakage into the air has already been proposed and is actually used.

However, even in this case, the high voltage cord 104
Leakage current is generated by the wiring of
As shown in FIG. 13, the operating current Idyn that flows into the ground through the surrounding frame or the like and is detected by the output current detection unit of the high-voltage power supply device 103 is superposed as an error current through the ground to generate the operating current Idyn. The problem remains that an error occurs in the detected value of.

Therefore, the problem that the operating current Idyn of the corona discharge device 100 cannot be detected with high accuracy due to this leakage current and the operation current Idyn can be detected with high accuracy is solved. There has already been proposed a device in which the leakage current is corrected at the time of detection (Japanese Patent Laid-Open No. 1-279271).

In the device according to this proposal, the voltage (Vpi) applied to the discharge wire 101 of the corona discharge device 100 is used.
n) is added to the pulse width modulation (PWM) controller to switch the primary side of the high voltage circuit with 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 to the shield member of the corona discharge device 100 and the photoconductor drum. The inflow current to the surface of the photoconductor drum is compared as a voltage, and a switching element composed of a high breakdown voltage type transistor or the like is controlled by the comparison output, and the corona discharge device 1
When 00 has a grid electrode, the grid potential is controlled to be a potential corresponding to the Vgrid remote. Then, the secondary side output voltage of the high-voltage power supply device, that is, the voltage applied to the corona discharge device 100 is detected as Vout, and the current flowing to the surface of the photosensitive drum is detected and monitored as Id, and the ground from the high-voltage power supply device is detected. Current to the side, that is, the shield current Is and Id are added to feed back the total current It 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 the sampling result is calculated in the difference calculation processing unit to calculate the difference from the target value in consideration of the error value due to the leakage current read from the target value table. After that, the output remote value calculation processing unit causes the corona discharge device 10 to
The AC component remote of 0 is transferred to the remote value output processing unit and fed back to the corona discharge device 100 via each D / A converter, and the output current is controlled to a predetermined value.

However, in the case of the device according to the above proposal,
Since complicated correction operation is required due to leakage current, the configuration of the device becomes complicated and the cost is significantly increased, and the digital error correction must be set for each image recording device. Has a new problem that it becomes complicated.

[0016]

Therefore, the present invention has been made in order to solve the above-mentioned problems of the prior art.
It is an object of the present invention to provide a corona discharge device which does not require a complicated correction operation due to a leakage current or the like and which can detect and control an operating current with a very simple structure with high accuracy.

That is, the present invention comprises a discharge wire and a shield member surrounding the discharge wire with at least one surface open, and a corona discharge is generated by applying a high voltage to the discharge wire. ,
In a corona discharge device for detecting an operating current flowing from the discharge wire to a member to be discharged and controlling the operating current, a high voltage power supply unit for applying a high voltage to the discharge wire is integrated with the shield member. Provided, and at least a part of this high-voltage power supply unit is covered with a conductive member, the conductive member is electrically connected to the shield member, the shield current flowing in the shield member and the leakage current flowing in 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]

In the present invention, the shield member is integrally provided with a high-voltage power supply unit for applying a high voltage to the discharge wire, and at least a part of the high-voltage power supply unit is covered with a conductive member and the conductivity The member is electrically connected to the shield member so that 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 operating current detection unit. Therefore, since the shield member is integrally provided with a high-voltage power supply unit for applying a high voltage to the discharge wire, a high-voltage cord for applying a high voltage from the high-voltage power supply unit to the shield member is unnecessary. Therefore, it is possible to prevent the generation of leakage current from the high voltage cord. Further, 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 Since it is configured to directly return to the high-voltage power supply unit of the high-voltage power supply unit without passing through the detection unit, leakage current generated directly from the high-voltage power supply unit can also be detected by the operation current detection unit along with the shield current flowing through the shield member. By directly returning to the high-voltage power supply section of the high-voltage power supply unit without passing it, it is possible to prevent the influence of leakage current from flowing into the operating current detection section with an extremely simple structure, and the operating current detection is highly accurate. Can be done.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

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, the surface of the photosensitive drum 1 is uniformly charged by a primary charger 2, and then an optical system 3 including a light source, a mirror, etc.
The image of the original is exposed through the to form an electrostatic latent image on the surface of the photoconductor drum 1, and the electrostatic latent image is developed by the developing device 4. Then, after the developed image formed on the surface of the photoconductor drum 1 is transferred onto the recording paper 6 by the charging of the transfer charger 5, the recording paper 6 onto which the developed image is transferred is charged by the separation charger 7. The image is recorded by separating it from the surface of the photoconductor drum 1 and fixing the developed image on the recording paper 6 by the fixing device 8.

By the way, the corona discharge device according to the present invention is used, for example, as the separation charger 7 or the like.

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

In the figure, reference numeral 10 denotes a corona discharge device, which is a discharge wire 1
1 and a metal shield member 12 surrounding the discharge wire 11 in a U-shaped cross-section with one surface open,
Fixed to both ends of the shield member 12 in the longitudinal direction,
Insulation blocks 13 and 14 for holding both ends of the discharge wire 11 in a stretched state are provided. Further, as shown in FIG. 3, a connection terminal 15 for applying a high alternating current voltage obtained by superposing a direct current voltage on the discharge wire 11 is provided on the outer end portion of the insulating block 13 in a lateral direction. It is projected.

The corona discharge device 10 is adapted to generate a corona discharge by applying a high voltage of alternating current obtained by superposing the direct current voltage by the high voltage power supply device 16 to separate recording sheets. There is.

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

In the figure, 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 thereof is The switching element Q is connected. Further, the secondary winding N2 of the step-up transformer T has a capacitor C connected between the windings, and
An alternating high voltage is output from one end of the secondary winding N2 via a resistor R.

Further, the high-voltage power supply device 16 has an output current detection 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 shown in FIG.
As shown in, the operating current I flowing through the recording paper 6 as a member to be discharged, which receives corona discharge from the corona discharge device 10.
In order to control the operating current with high accuracy by detecting only dyn, the current flowing from the discharge wire 11 to the shield member 12 is directly returned to the power supply unit of the high-voltage power supply device 16, so that the shield current is detected as the output current. It is configured to prevent it from flowing into the section.

FIG. 5 is a circuit diagram showing an essential part of the high-voltage power supply device 16.

In FIG. 5, reference numeral 20 shows an equivalent circuit of the corona discharge device. The equivalent circuit 20 of this corona discharge device is an insulation resistance Rb which is air from the discharge wire 11.
An operating current Idyn flows through the member to be discharged through the discharge target member, and the member to be discharged is charged to a predetermined potential, so that a DC voltage V
A voltage drop of ost occurs and the discharge wire 11
From the discharge wire 11 and the shield member 12 via the electrostatic capacitance C and the air resistance Rs between the air gaps.
It flows to 2. The current flowing through the shield member 12 flows through the resistor R1 to the one end 21 of the DC power supply of the power supply device 16. Further, the operation current Idyn flowing from the discharge wire 11 to the ground via the member to be discharged is the operation amplifier 2 which constitutes the output current detection circuit 18.
2 and the AC component and DC component of the operating current Idyn are detected. The AC component and the DC component of the operating current Idyn thus detected flow to the output control circuit 19 via the monitor box 23, and the output control circuit 19 controls the switching element Q to be turned on and off, whereby the output operating current Idyn is maintained at a constant value.

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

Further, among the various parts constituting the high-voltage power supply device 16, a step-up transformer T that generates a particularly high voltage is provided.
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 integrated into one block as the high-voltage power supply unit 25 in terms of insulation and the like. The parts are And
The components constituting the other control circuit constituting the high-voltage power supply device 16 are assembled 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.
Step-up transformer T and secondary winding N2 of the step-up transformer T
It is configured to accommodate circuit elements such as a capacitor C and a resistor R connected to the. In addition, the high voltage power supply unit 21
As shown in FIG. 1, the outer surface of the insulating case 27 is coated with a conductive paint 27a in which metal powder such as Al is dispersed, so that the insulating case 27 itself forms a conductive shield. Is becoming

By the way, in this embodiment, the shield member is integrally provided with a high-voltage power supply unit for applying a high voltage to the discharge wire, 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 leak 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 operating current detection unit. Is configured to let.

That is, as shown in FIG. 3, the shield member 12 of the corona discharge device 10 is integrally formed with the shield member 12 at one end portion in the longitudinal direction or the shield member 1 as shown in FIG.
2 is a flat plate-shaped mounting portion 3 which is provided as a member separate from the above.
5 are provided.

As shown in FIG. 1, the high voltage power supply unit 21 is integrally mounted on the mounting portion 35. To mount the high-voltage power supply unit 21 on the mounting portion 35, for example, as shown in FIG. 3, a fixing piece 36 projecting downward on one end of the high-voltage power supply unit 21 is mounted on the tip of the mounting portion 35 downward. It is performed by screwing or adhering to the fixing piece 37 that is provided in a protruding manner.

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

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

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

With the above-mentioned structure, the corona discharge device according to this embodiment detects the operating current as follows. That is, in the corona discharge device 10, as shown in FIG. 1, the high voltage power supply unit 21 of the high voltage power supply 16 applies a high alternating current voltage obtained by superimposing a direct current voltage on the discharge wire 11 to discharge the discharge wire 11. From this, a corona discharge is generated to charge or discharge the member to be discharged.

At this time, as shown in FIG. 5, the operating current Idyn flowing from the discharge wire 11 to the member to be discharged flows into the output current detection circuit 18 through the ground and the output current detection circuit 18 through the ground. The operating current Idyn is detected by. Then, the operating current Idyn
The output control circuit 19 controls the switching element Q to be turned on / off so that is 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 device 16 to the outside flows to the insulating case 27 of the high-voltage power supply unit 25 whose outside is treated with conductivity. As shown in FIG. 5, together with the shield current Is flowing through the shield member 12 electrically connected to the insulating case 27, flows through one end 21 of the DC power supply of the high voltage power supply device 16 to detect the output current of the high voltage power supply device 16. It does not flow into circuit 18. Therefore, the leakage current does not become an error current when detecting the operating current Idyn, and as shown in FIG. 16, only the operating current Idyn can be detected with high accuracy by the output current detection circuit 18.

As described above, in this embodiment, the shield member 12 is integrally provided 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 made 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 insulating case 27 having conductivity are
The operating current Idyn is configured to be directly returned to the high-voltage power supply section of the high-voltage power supply unit 25 without passing through the output current detection circuit 18, and therefore the shield member 12 is provided.
In addition, since the high voltage power supply unit 25 for applying a high voltage to the discharge wire 11 is integrally provided, a high voltage code for applying a high voltage from the high voltage power supply unit 25 to the shield member 12 is unnecessary, and the high voltage code is not required. It is possible to prevent the generation of leakage current from the. In addition, at least a part of the high-voltage power supply unit 25 has an insulating case 2 having conductivity.
7, the electrically conductive insulating case 27 is electrically connected to the shield member 12, and the shield current flowing in the shield member 12 and the leakage current flowing in the insulating case 27 are detected by the output current detection circuit 18 of the operating current Idyn. Since it is configured to directly return to the high-voltage power supply unit of the high-voltage power supply unit 25 without passing through, the leakage current directly generated from the high-voltage power supply unit 25, together with the shield current flowing through the shield member 12, is the operating current Idyn.
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 detection circuit 18 of FIG. 1, it is possible to prevent the influence of leakage current from flowing into the output current detection circuit 18 of the operating current Idyn with a very simple configuration. Therefore, the operating current Idyn can be detected with high accuracy.

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

That is, in this embodiment, FIGS.
As shown in FIG. 3, a rectangular parallelepiped mounting part 30 having both ends opened is integrally formed at one end of the shield member 12, and an insulating case 27 constituting the high-voltage power supply unit 16 is fitted and fixed to the mounting part 30. It is supposed to be done.
Therefore, as shown in FIG. 10, the side walls 31, 31 of the mounting portion 30 are provided with inwardly projecting claw portions 32, 32 integrally formed by cutting out a part of the side walls 31, 31. At the same time, the side walls 33, 33 of the insulating case 27 have recesses 34, 34 that engage with the claws 32, 32.
Are formed. Then, the high voltage power supply unit 16
By inserting the insulating case 27 constituting the mounting portion 30 into the mounting portion 30, the claw portions 32 and 32 provided on the side walls 31 and 31 of the mounting portion 30 are replaced by the recesses 34 provided on the side walls 33 and 33 of the insulating case 27. By relatively engaging with 34, the high voltage power supply unit 16 is integrally attached to the attachment portion 30.

The rest of the construction and operation are the same as in the first embodiment, so a description thereof will be omitted.

Third Embodiment FIG. 11 shows a third embodiment of the present invention. The same parts as those of the first embodiment will be designated by the same reference numerals and will be described below. The high-voltage power supply unit 25 of the high-voltage power supply device 16 and the printed wiring board 2 of the high-voltage output control unit
6 is integrally formed on the insulating substrate 40, and the surface of the insulating substrate 40 leaks to a region corresponding to a portion where a high voltage member such as the step-up transformer T of the high voltage power supply unit 25 is arranged. 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 structure and operation are the same as those of the first embodiment, and the description thereof will be omitted.

[0049]

The present invention, which has the above-described structure and operation, does not require a complicated correction operation associated with a leakage current or the like, and is capable of accurately detecting and controlling the operation current with an extremely simple structure. A discharge device can be provided.

[Brief description of drawings]

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

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

FIG. 3 is an exploded perspective view showing an 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 connecting 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.

10 (a) and 10 (b) are perspective views respectively showing a mounting portion 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

Claims (1)

[Claims] 1. A discharge wire and a shield member that surrounds the discharge wire with at least one surface open, and a corona discharge is generated by applying a high voltage to the discharge wire. In the corona discharge device for detecting the operating current flowing from the discharge target member to control the operating current, the shield member is integrally provided with a high-voltage power supply unit for applying a high voltage to the discharge wire. , Covering at least a part of this high-voltage power supply unit with a conductive member, electrically connecting the conductive member to a shield member, and reducing the shield current flowing through the shield member and the leakage current flowing through the conductive member to the operating current. Corona discharge, which is characterized in that it directly returns to the high-voltage power supply unit of the high-voltage power supply unit without passing through the detection unit. Electrical equipment.