JPH1124371A - Electrifier abnormal discharge prevention circuit, high-voltage power source device and electrifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the adjustment of grid voltage and to surely prevent abnormal high-voltage leakage to a structure other than an electrifier. SOLUTION: By adjusting the resistance value of a resistance 4 giving the specified grid voltage and connected to the grid 5 of the electrifier, the grid voltage is adjusted. Then, the grid voltage is prevented from exceeding a fixed value by a varistor 6 connected in parallel with the resistance 4, and sparks at the time of abnormal discharge are prevented from reaching a photoreceptor and the like except the electrifier and damaging the photoreceptor and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for preventing abnormal discharge of a charger, a high-voltage power supply, and a charger. The present invention relates to a charger abnormal discharge prevention circuit, a high-voltage power supply, and a charger that can prevent leakage.

[0002]

2. Description of the Related Art As shown in the configuration diagram of FIG. 8 and the equivalent circuit diagram of FIG. And 5 KV by the high voltage power supply 2
A corona electrode 3 to which the above high voltage is applied is provided. In particular, a charger called a scorotron includes a grid 5 to which a grid voltage of, for example, 500 to 1000 V is applied by a resistor (grid resistor) 4 in order to stabilize corona discharge by the corona electrode 3. Since the voltage of the grid 5 is induced by the discharge from the corona electrode 3 to the photoconductor 1, there is no need to apply a special voltage to the grid 5.

As shown in the configuration diagram of FIG. 10, a varistor 6 in which a plurality of Zener diodes are connected in series is used in place of the resistor (Japanese Patent Laid-Open No. 61-294467).
No. reference. ).

[0004]

In the meantime, air discharge called corona discharge is normally generated stably, but abnormal discharge may occur due to intrusion of foreign substances such as dust. At this time, as shown in FIG. A, the grid voltage rapidly rises to the voltage of the corona electrode 3 in about 20 μs, for example, and gradually decreases due to the capacitance in the circuit.

[0005] When this abnormal discharge occurs, a spark may be generated to cause slight damage to the charger, and at this time, the surface of a structure such as the photoconductor 1 disposed adjacent to the charger may be damaged. Sparks, so-called leaks, can damage the surface of the structure.

In the conventional example in which the grid voltage is set by the varistor 6, since the grid voltage is prevented from rising to a certain level or more, it is possible to prevent leakage and damage to the charger due to the leak. However, in this conventional example, it is impossible to adjust the grid voltage. For example, when dust floating in the air, such as toner powder, adheres to the corona electrode 3 or the grid 5, or when there is a mounting dimensional error, the grid voltage is not adjusted. There is a problem that the voltage cannot be finely adjusted.

[0007] The present invention has been made in view of the above circumstances, and it is possible to adjust the grid voltage,
An object of the present invention is to provide a charger abnormal discharge prevention circuit, a high-voltage power supply device, and a charger that can reliably prevent abnormal high-pressure leakage to a structure other than the charger.

[0008]

In order to achieve the above object, a circuit for preventing abnormal discharge of a charger according to the present invention includes a resistor for applying a predetermined grid voltage to a grid of a charger having a corona electrode and a grid. And a varistor 6 connected in parallel with the varistor 4 and having a breakdown voltage set higher than the grid voltage set by the resistor 4.

According to this, the grid voltage can be finely adjusted by adjusting the resistance value of the resistor 4, and
The varistor 6 prevents the grid voltage from increasing above the breakdown voltage of the varistor 6, and reliably prevents leakage.

In order to achieve the above object, the high-voltage power supply according to the present invention includes a high-voltage power supply 2 for applying a high voltage to a corona electrode 3 of a charger, and a predetermined grid voltage applied to a grid 5 of the charger. And a varistor 6 connected in parallel with the resistor 4 and having a breakdown voltage set higher than the grid voltage set by the resistor 4.

By adjusting the resistance value of the resistor 4, the grid voltage can be finely adjusted, and the varistor 6 prevents the grid voltage from rising above the breakdown voltage of the varistor 6, thereby preventing the occurrence of leakage. Is reliably prevented.

Further, the charger according to the present invention includes a corona electrode 3 to which a high voltage is applied and a grid 5 to which a predetermined grid voltage is applied by a resistor 4 in a case. In order to achieve the above-mentioned object, in the charger attached to and detached from the high-voltage power supply circuit composed of the high-voltage power supply 2 and the resistor 4, the discharge voltage is set higher than the predetermined grid voltage, and the charging voltage is set in parallel with the resistance 4. The varistor 6 to be connected is detachably provided on the end face of the case connected to the high-voltage power supply.

Thus, the grid voltage can be finely adjusted by adjusting the resistance value of the resistor, and the varistor prevents the grid voltage from rising above the breakdown voltage of the varistor, thereby ensuring the occurrence of leakage. Is prevented. Also, remove the corona electrode, grid and varistor from the high-voltage power supply circuit for inspection, care,
It can be replaced, and the convenience of maintenance can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A charger abnormal discharge prevention circuit, a high-voltage power supply and a charger according to one embodiment of the present invention will be described below in detail with reference to the drawings.

A charger according to one embodiment of the present invention is used in an electrophotographic apparatus, and as shown in the configuration diagram of FIG.
A corona electrode 3 which is arranged at a predetermined distance on one side and is supplied with a high voltage of 5 KV or more, for example, 7 to 8 KV by the high voltage power supply 2 of the high voltage power supply device according to one embodiment of the present invention. I have.

To stabilize the corona discharge of the corona electrode 3, a grid 5 to which a grid voltage of, for example, 700 to 800 V is applied by the resistor 4 of the high-voltage power supply is provided.

The resistor 4 is constituted by a variable resistor. By adjusting the resistance value, for example, a dimensional error in the interval between the charger and the photosensitive member 1 generated during the assembly, and the interval between the corona electrode 3 and the grid 5 are generated. Dimensional error, corona electrode 3 accompanying use
And an error in the surface potential of the photoconductor 1 caused by contamination of the grid 5 or the like.

Further, in the charger abnormal discharge prevention circuit and the high voltage power supply including the same, the varistor is connected in parallel with the resistor 4 and the discharge voltage is set higher than the grid voltage set by the resistor 4. 6 are provided.

It is sufficient that the breakdown voltage of the varistor 6 is set higher than the grid voltage set by the resistor 4. However, in order to prevent the occurrence of leakage, the grid voltage set by the resistor 4 is set as small as possible. It is preferable to set the value close to. However, as described above, the dimensional error in the interval between the charger and the photoreceptor 1 generated during assembly, the dimensional error in the interval between the corona electrode 3 and the grid 5, the contamination of the corona electrode 3 and the grid 5 due to use, and the like occur. Photoconductor 1
In order to eliminate the error of the surface potential, it is necessary to set the voltage higher than the grid voltage by a certain value or more. In this embodiment, taking these circumstances into consideration, the breakdown voltage of the varistor 6 is set to be 100 to 500 V higher than the grid voltage set by the predetermined resistor 4.

It is most desirable that the varistor 6 starts discharging at the same time as the occurrence of abnormal discharge. However, as shown in FIG. 6, when the varistor 6 is not provided, the grid voltage VG is reduced from the occurrence of abnormal discharge. Since the maximum value is reached in the predetermined time a, when the breakdown voltage is set 100 to 500 V higher than the grid voltage set by the resistor 4 as described above, the discharge of the varistor 6 starts abnormal discharge. Will be started late. If the delay of the start of the discharge increases, a leak occurs, and the surface of the photoconductor 1 may be damaged.

Therefore, in this embodiment, the response speed of the varistor 6 is set to be shorter than this time in consideration of the time a from the occurrence of the abnormal discharge to the peak of the grid voltage VG being about 20 μs. ing. As a result,
For example, as shown in FIG. 7, the discharge of the varistor 6 starts within a very short time when the varistor 6 reaches the breakdown voltage before the grid voltage VG reaches the peak value without the varistor 6 due to the occurrence of abnormal discharge. Thus, the occurrence of a leak is reliably prevented.

By the way, in the electrophotographic apparatus, a high-voltage power supply 2 is used in order to enhance the maintenance of the charger.
In many cases, a charger can be attached to and detached from a high-voltage power supply device including a resistor and a resistor 4.

Therefore, as shown in the front view of FIG. 2, in this embodiment, one end of a case 7 of the charger is connected to a high-voltage power supply, a resistor and Three grounding jacks 8a, 8
b, 8c, and sockets 9a, 9b, 9 for inserting these jacks 8a, 8b, 8c into the main body of the electrophotographic apparatus.
c is provided so that the charger can be attached to and detached from the high-voltage power supply.

In this case, the varistor 6 connected in parallel with the resistor 4 may be attached to the main body of the electrophotographic apparatus as a part of the power supply circuit from the viewpoint of the circuit function, but in this embodiment, the replacement operation is easy. In order to achieve this, a recess as shown in the figure is formed and assembled on the end face of the case 7 provided with the power supply connection jack on the charger side.

In this embodiment, since the varistor 6 is opened when it is damaged, it cannot be apparently determined whether or not the varistor 6 is damaged.
The varistor 6 is used while being damaged, which may cause a leak.

Therefore, in a charger abnormal discharge prevention circuit and a high voltage power supply according to another embodiment of the present invention, as shown in the configuration diagram of FIG. 3, the high voltage power supply 2 is connected to the corona electrode 3 and the grid 5. A switch 10 for selectively connecting the high voltage power supply 2 to the grid 5 is used as a check power supply for applying a voltage lower than the breakdown voltage to the grid 5.

Further, the grid 5 is supplied by the high-voltage power supply 2.
When a voltage lower than the breakdown voltage is applied to the varistor 6
Current detecting means 11 for checking whether or not a check current flows is connected in series with the varistor 6; means for detecting whether or not the varistor 6 is damaged based on the presence or absence of the check current; And a notifying unit for notifying the varistor 6 of damage when detection (current does not flow).

The switch 10 is switched over to the grid 5 for a short time when the power of the electrophotographic apparatus is turned on. When a current flows through the varistor 6, the varistor 6 is normal. Is detected, and the operator is notified by notification means such as a buzzer, a bell, a sound generator, a lamp, and a character display.

Of course, instead of such a switch 10, as shown in FIG. 4, for example, the corona electrode 3 is always connected to the high voltage power supply 2, and the grid 5 is connected to and disconnected from the high voltage power supply 2 by the switch 10a. When the power is turned on or when printing is suspended, the grid 5 is connected to the
May be checked for damage, and as shown in FIG. 5, two relay switches 10b, 10c
After about 100 μS has passed immediately after power-on, the relay switch 10b is turned on to connect the high-voltage power supply 2 to the grid 5, and then check whether the varistor 6 has been damaged until about 100 μS has elapsed. After that, the normal operation may be started by turning off the relay switch 10b and turning on the relay switch 10c.

[0030]

As described above, the circuit for preventing abnormal discharge of the charger of the present invention is connected in parallel with the resistor for applying a predetermined grid voltage to the grid of the charger having the corona electrode and the grid, and the discharge voltage is reduced. Since the varistor has a varistor set higher than the grid voltage set by the resistor, the grid voltage can be finely adjusted by adjusting the resistance value of the resistor, and the varistor allows the grid voltage to be equal to or higher than the breakdown voltage of the varistor. Ascending is reliably prevented, and occurrence of leak is reliably prevented.

In the charger abnormal discharge prevention circuit according to the present invention, particularly when the response speed of the varistor is set to 20 μs or less, the grid voltage is reduced before the grid voltage reaches the peak value without the varistor due to the occurrence of abnormal discharge. 6, the discharge of the varistor 6 is started within a short time, and the occurrence of leakage can be more reliably prevented.

In particular, in the charger abnormal discharge prevention circuit of the present invention, a check power supply for applying a voltage lower than the discharge voltage to the grid, and a voltage lower than the discharge voltage is applied to the grid by the check power supply. If current detection means for checking whether a check current flows through the varistor when the varistor is provided, and means for detecting whether the varistor is damaged based on the presence or absence of the check current, when the energization of the charging device is started or when non-printing is performed, It is sometimes possible to check whether or not the varistor is normal, and it is possible to recognize whether or not there is a possibility that a leak may occur due to breakage of the varistor.

The high-voltage power supply device of the present invention comprises a high-voltage power supply for applying a high-voltage to the corona electrode of the charger, a resistor for applying a predetermined grid voltage to the grid of the charger, and a parallel connection with the resistor. A varistor whose voltage is set higher than the grid voltage set by the resistor, so that the resistance value of the resistor can be adjusted to finely adjust the grid voltage of the charger connected thereto, and the varistor can control the grid voltage. The voltage is reliably prevented from rising above the breakdown voltage of the varistor, and leakage is reliably prevented.

The charger of the present invention includes a corona electrode to which a high voltage is applied, and a grid to which a predetermined grid voltage is applied by a resistor, and includes a high voltage power supply for applying a high voltage to the corona electrode and a high voltage comprising a resistor. In the charger attached to and detached from the power supply circuit, the discharge voltage is set higher than the predetermined grid voltage, connected in parallel with the resistor, and provided with a varistor attached to and detached from the high-voltage power supply circuit. The resistance value can be adjusted to fine-tune the grid voltage of the charger connected to it, and the varistor reliably prevents the grid voltage from rising above the discharge voltage of the varistor, thereby reliably preventing leakage. Is done.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a front view of one embodiment of the present invention.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

FIG. 4 is a configuration diagram of still another embodiment of the present invention.

FIG. 5 is a configuration diagram of a modified example of still another embodiment of the present invention.

FIG. 6 is a grid voltage waveform diagram when an abnormal discharge occurs in the absence of a varistor.

FIG. 7 is a grid voltage waveform diagram when an abnormal discharge occurs in one embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional example.

FIG. 9 is an equivalent circuit diagram of a conventional example.

FIG. 10 is a configuration diagram of another conventional example.

[Explanation of symbols]

 2 High voltage power supply 3 Corona electrode 4 Resistance 5 Grid 6 Varistor

Claims (5)

[Claims] 1. A varistor connected to a grid of a charger having a corona electrode and a grid, wherein the varistor is connected in parallel to a resistor for applying a predetermined grid voltage, and a breakdown voltage is set higher than a grid voltage set by the resistor. A circuit for preventing abnormal charging of a charger. 2. The circuit for preventing abnormal discharge of a charger according to claim 1, wherein the response speed of the varistor is set to 20 μs or less. 3. A check power supply for applying a voltage lower than the breakdown voltage to the varistor, and whether a check current flows through the varistor when a voltage lower than the breakdown voltage is applied to the varistor by the check power supply. 3. The circuit for preventing abnormal discharge of a charger according to claim 1, further comprising a current detecting means for checking whether or not the varistor is damaged based on the presence or absence of the check current. 4. A high voltage power supply for applying a high voltage to a corona electrode of a charger, a resistor for applying a predetermined grid voltage to a grid of the charger, and a resistor connected in parallel with the resistor, and a discharge voltage is set by the resistor. And a varistor set higher than the grid voltage to be applied. 5. A high-voltage power supply circuit including a corona electrode to which a high voltage is applied, and a grid to which a predetermined grid voltage is applied by a resistor, and comprising a high-voltage power supply for applying a high-voltage to the corona electrode and a resistor. In the charger, the discharge voltage is set higher than the predetermined grid voltage, and a varistor connected in parallel with the resistor is detachably provided on an end face of the case connected to the high-voltage power supply. Characteristic charger.