JP2000324677A - High voltage power supply, imaging apparatus and control method for high voltage power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an abnormality occurring in a load connected with a high voltage power supply from spreading to the photosensitive drum, or the like, of an imaging apparatus employing a high voltage power. SOLUTION: When a leak takes place in a load, e.g. a separate charger performing corona discharge, leak is blocked by interrupting output after a required time t1 later and then the output is reset (t2). When a leak takes place again after the output is reset, the output is interrupted after a required time t4 later. The required times t1, t4 and t6 are shortened as the intervals (t2+t3), t5 of occurrence of leak are shorted, as shown on the drawing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage power supply, an image forming apparatus, a control method of a high-voltage power supply, and a storage medium, and more particularly to an image forming apparatus having a high-voltage power supply circuit for supplying a high voltage to a separation charger. The present invention relates to an apparatus, a method, and a storage medium.

[0002]

2. Description of the Related Art In an electrophotographic system such as a copying machine, a photosensitive drum is uniformly charged by a primary charger, a latent image is formed by exposing the photosensitive drum with a laser or the like, and a developing device is used. Generally, a method of developing, transferring to a recording medium by a transfer charger, separating the recording medium from the photosensitive drum by a separation charger, and fixing an image to the recording medium by a fixing device is generally performed.

As described above, in the electrophotographic system,
A plurality of chargers may be used in the process of forming an image on a recording medium.

[0004] A high voltage is applied to the charger by a high voltage power supply, and usually performs corona discharge. However, depending on conditions such as deterioration as the durability advances, contamination with paper powder or toner, and environment, there is a possibility that the electric field may be out of balance and leak discharge may occur.

A high-voltage power supply for applying a high voltage to the charger is
Usually, from the viewpoint of safety, various protection means are provided so that the leak state does not continue.

For example, FIG. 7 shows an oscillator circuit B, a bridge circuit composed of transistors Q4 to Q7, a transformer T
1 generates a high-voltage AC output. The amplitude of the output at this time is determined by increasing the input voltage Vcc to V1 by the booster circuit.
And is variable by controlling V1. The amplitude of the output voltage is determined by the level of the CTL (control) signal, and a high voltage is output when the ON / OFF signal becomes High.

Further, when the leak detecting means D detects a leak, the output V5 of the leak detecting means D becomes High and is input to the oscillation circuit B, and the oscillation circuit is stopped.

The oscillation circuit B is an example (conventional example 1) of FIG.
The configuration is as shown in FIG. The operation will be described with reference to FIG. When V5 becomes High, the comparator Q
21 becomes High, and the transistor Q23 becomes O
N stops the oscillator. When the oscillator stops, the leak state is also released, V5 goes low again, and the charge of the capacitor C21 is discharged by the time constant of the capacitor C21 and the resistor R21. When V7> V6, the oscillation circuit operates again. An intermittent protection system that repeats this operation is often used.

FIG. 8B shows another example (conventional example 2).
As shown in the figure, when the leak detecting means D detects a leak, V5 becomes High,
As a timer, charging is performed with the time constant of the resistors R21 and R22 and the capacitor C21, and the output of the comparator Q21 is High.
, The thyristor Q22 turns on and the oscillator stops. That is, it is stopped only when the leak state continues for a certain period of time.

When the leak state ends, V5 becomes low and the output of the comparator Q21 is inverted, but the thyristor Q22 keeps the ON state and the oscillator remains stopped.

When the ON / OFF signal is turned OFF and ON once, the stop state is released, and the operation starts again. FIG. 10 shows the waveform of each part at that time. This latch protection method is also a commonly used protection means.

Further, there is a method in which the above-described intermittent protection method and latch method are combined, intermittent protection operation is performed a certain number of times (or period), and then the high voltage output is completely stopped by latch protection.

[0013]

However, in the intermittent protection method of the prior art example 1, the intermittent protection method of the prior art has a problem such as a high humidity environment, contamination of the charger, and the like.
In a state where a leak easily occurs, once the leak starts,
There is a possibility that the intermittent operation is continued for a long time, and the state where the output is extremely suppressed continues. In addition, even if an abnormality occurs in the charger completely, the charger continues to operate even if it is short-circuited.

Further, the latch protection system of the conventional example 2 is excellent in safety because the high voltage output is stopped when a leak occurs. However, once the high voltage output is stopped even at the time of a slight leak that does not continue, there is a problem that the automatic recovery cannot be performed. Therefore, there is a case where a timer is set from when a leak is detected to when the high-voltage output is stopped, and measures are taken to stop the high-voltage output after the leak continues for a preset period.

Further, when a protection method is performed such that once the leak continues for a preset period, the operation is stopped once, the operation is restarted, and the operation is completely stopped when the above operation is repeated a specified number of times. In the case where the leakage occurs twice and the output power is large, the photosensitive drum may be damaged.

The present invention has been made under such circumstances, and when an abnormality occurs in a load connected to a high-voltage power supply, this abnormality is detected, for example, by a photosensitive device of an image forming apparatus using the high-voltage power supply. It is an object of the present invention to provide a high-voltage power supply device, an image forming apparatus, a control method of a high-voltage power supply, and a storage medium that can prevent the influence on members such as a body drum.

[0017]

In order to achieve the above object, according to the present invention, a high-voltage power supply is configured as described in the following (1) to (4), and an image forming apparatus is configured as described in the following (5) and (4). 6), and the control method of the high voltage power supply is configured as in the following (7).

(1) In a high-voltage power supply device for applying a high-voltage output to a load for performing corona discharge and changing the amplitude of the high-voltage output by a CTL signal, a booster circuit whose output is controlled by the CTL signal; An oscillation circuit for driving a bridge circuit that generates an alternating current of the high-voltage output from the output of the circuit; a leak detection unit that detects a leak of the load; and stopping the oscillation circuit when the leak detection unit detects a leak. Means for causing the oscillation circuit to stop operating again, and means for changing the time from when the leak detection means detects the leak to when the oscillation circuit is stopped according to the interval at which the leak occurs. High voltage power supply with

(2) In a high-voltage power supply device for applying a high-voltage output to a load for performing corona discharge and changing the amplitude of the high-voltage output by a CTL signal, a booster circuit whose output is controlled by the CTL signal; An oscillation circuit for driving a bridge circuit that generates an alternating current of the high-voltage output from the output of the circuit, a leak detection unit that detects a leak of the load, and the oscillation circuit when a leak is continuously detected for a required time. Means for stopping, means for operating the stopped oscillation circuit again, and gradually decreasing the amplitude of the output from the time when the leak detection means detects the leak until the time when the oscillation circuit is stopped. Means for changing the time in accordance with the interval at which the leak occurs.

(3) Abnormality detecting means for detecting an abnormality in the load, stop-return means for stopping the high-voltage output after a required time has elapsed after detecting the abnormality with the abnormality detecting means, and restoring again. Control means for controlling the required time to be shorter as the time until the abnormality is detected by the abnormality detector is shorter.

(4) The high-voltage power supply according to (3), further comprising means for gradually reducing the high-voltage output within the required time.

(5) An image forming apparatus comprising the high-voltage power supply according to any one of (1) to (4).

(6) The image forming apparatus according to (5), wherein the load is a separate charger.

(7) Step A for judging the presence or absence of an abnormality in the load, and Step B for stopping the high-voltage output and returning again after a required time after judging the existence of the abnormality in this step A.
And a step C of controlling the required time to be shorter as the time from the stop of the high voltage output to the determination of the abnormality is shorter.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment of a copying machine. The present invention is not limited to the form of an image forming apparatus such as a copying machine, but can be similarly implemented in the form of a high-voltage power supply and a control method of a high-voltage power supply.

[0026]

(Embodiment 1) FIG. 1 is a diagram showing a configuration of a main part (high-voltage power supply circuit) of a "copier" according to Embodiment 1. FIG.
As shown in FIG.
A high voltage AC output is generated by a bridge circuit composed of Q7 and a transformer T1. The output amplitude at this time is variable by boosting the input voltage Vcc to V1 by a booster circuit and controlling the output voltage V1 of the booster circuit. The amplitude of the output voltage is determined by the level of the CTL signal.
When it becomes h, a high pressure is output.

Further, the apparatus has a leak detecting means D. When the leak detecting means D detects a leak, the output V5 of the leak detecting means D becomes High, is inputted to the oscillation circuit B, and the oscillation circuit is stopped.

FIG. 2 is a detailed diagram of the oscillation circuit B in FIG. In the figure, Q21 is a comparator, Q22 is a thyristor, V7 is a reference voltage, and when V6> V7, the output of the comparator Q21 becomes High, and Q22 becomes O
N.

The operation of the high-voltage power supply circuit will be described below with reference to FIGS. 1 and 2 and FIG. 3 showing the waveforms of various parts.

When a leak occurs, the load current Io increases, the output of the leak detecting means D goes high, and charges the capacitor C21 according to a time constant determined by the capacitor C21 and the resistors R21 and R22. V6 reaches V7 over a time t1 determined by this time constant. Then, the output of the comparator Q21 becomes High, and the thyristor Q2
When 2 is turned on, V8 goes low, the oscillator stops, the high-voltage output stops, and the leak is reduced. Then, after the time t2, the high-voltage power supply circuit operates again by the return means (not shown), and operates normally during the time t3. Meanwhile, the capacitor C21 is connected to the capacitor C21 and the resistor R
Discharge occurs at the time constant determined by 21 and V6 reaches 0V.

When a leak occurs again, the leak occurs for a time t4 (= t1), and the high-voltage output is stopped and restored, similarly to the above-described operation.

Next, in the case of a leak immediately after returning, if the time from the previous leak is shorter than the time constant at which V6 decreases, after the leak is detected, V6 is detected.
Until V reaches V7 (t6 <t1), and the time during which the leak continues is also shortened.

The number of times V5 becomes High is counted by a counting means (not shown).
Stop completely and do not return.

As described above, according to this embodiment,
Since the time from the occurrence of the leak to the stop of the high pressure is shortened as the interval at which the leak occurs becomes shorter, damage to the photosensitive drum due to the leak can be prevented.

(Embodiment 2) FIG. 4 is a diagram showing a configuration of a main part (high-voltage power supply circuit) of a "copier" according to Embodiment 2. In this figure, V5 is also input to the output control circuit A in addition to the configuration of FIG.

Here, the oscillation circuit B is the same as in FIG. 2, and the details of the output control circuit are shown in FIG.

The operation of the high-voltage power supply circuit according to the present embodiment will be described below with reference to FIGS. 4 and 5 and FIG. 6 showing waveforms of various parts.

When a leak occurs, the output current Io increases, the leak detecting means D detects the leak, and the output V5
Becomes High, and the transistor Q31 is turned on. When the transistor Q31 is turned on, the input voltage V9 to the PWM (pulse width modulation) circuit E is reduced by the time constant determined by the resistor R32 and the capacitor C32, and the output amplitude is reduced by decreasing V1 by PWM. Become.

In FIG. 6, a leak occurs during t11, and the amplitude of the output voltage Vo is gradually reduced by the above-described operation. When the amplitude is reduced and the leak is reduced,
It returns to the original amplitude again over the time of t12. When a leak occurs again after normal operation during t13, the amplitude also decreases.
If this leak continues for the same time as in Example 1, (t1
4), the high-voltage output is stopped, and restored after time t15.

The above operation is repeated, and the leak detecting means D
The number of times that the output voltage V5 has become High is counted by a counting means (not shown), and when the output voltage V5 reaches a specified number, the output is not restored.

As described above, according to the present embodiment,
Change the time from leak occurrence to high pressure stop according to the interval at which the leak occurs, and if a leak is detected,
By reducing the amplitude of the output voltage, damage to the photosensitive drum due to leakage can be prevented.

[0042]

As described above, according to the present invention,
When an abnormality occurs in the load connected to the high-voltage power supply, the abnormality can be prevented from spreading to a member such as a photosensitive drum of an image forming apparatus using the high-voltage power supply.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a main part of a first embodiment.

FIG. 2 shows a configuration of an oscillation circuit.

FIG. 3 is a diagram showing waveforms of respective parts.

FIG. 4 is a diagram showing a main part configuration of a second embodiment;

FIG. 5 is a diagram showing a configuration of an amplitude control circuit.

FIG. 6 is a diagram showing waveforms of respective parts.

FIG. 7 is a diagram showing a configuration of a main part of a conventional example.

FIG. 8 shows a configuration of an oscillation circuit.

FIG. 9 is a diagram showing waveforms at various parts in Conventional Example 1.

FIG. 10 is a diagram showing waveforms at various parts in Conventional Example 2.

[Explanation of symbols]

 B oscillation circuit C21 capacitor D leak detection means R21, R22 resistance

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H003 AA15 EE11 2H032 AA05 5G004 AA01 BA01 BA03 BA04 CA03 DB05 DC01 EA01 5H007 AA06 AA17 CA01 CB05 CC12 CC32 DB01 DC05 EA02 FA14 GA05 GA08 5H730 AA17 AS04 BB14 DD01 FE08

Claims (7)

[Claims] 1. A high-voltage power supply that applies a high-voltage output to a load that performs corona discharge and changes the amplitude of the high-voltage output according to a CTL signal. A booster circuit whose output is controlled by the CTL signal. An oscillation circuit for driving a bridge circuit that generates the AC of the high-voltage output from an output; a leak detection unit that detects a leak of the load; and stopping the oscillation circuit when the leak detection unit detects a leak. Means, means for operating the stopped oscillation circuit again, and means for changing the time from when the leak detection means detects a leak to when the oscillation circuit is stopped according to the interval at which the leak occurs. A high-voltage power supply device comprising: 2. A high-voltage power supply device for applying a high-voltage output to a load for performing corona discharge and changing the amplitude of the high-voltage output by a CTL signal, wherein a booster circuit whose output is controlled by the CTL signal; An oscillation circuit for driving a bridge circuit that generates an alternating current of the high voltage output from an output; a leak detection unit that detects a leak of the load; and stopping the oscillation circuit when a leak is detected for a required time continuously. Means for causing the oscillation circuit to stop operating, and means for gradually reducing the output amplitude from the time when the leak detection means detects the leak to the time when the oscillation circuit is stopped. To
Means for changing in accordance with intervals at which leaks occur. 3. An abnormality detecting means for detecting an abnormality in a load,
Stop recovery means for stopping the high voltage output and returning again after a required time after detecting the abnormality with the abnormality detection means, and the required time as the time from the stop of the high voltage output to the abnormality detection by the abnormality detection means becomes shorter. A high-voltage power supply device comprising: control means for controlling the power supply to be shorter. 4. The high-voltage power supply according to claim 3,
A high-voltage power supply device comprising means for gradually reducing the high-voltage output within the required time. 5. An image forming apparatus comprising the high-voltage power supply according to claim 1. Description: 6. The image forming apparatus according to claim 5, wherein
The image forming apparatus, wherein the load is a separation charger. 7. Step A for determining whether there is a load abnormality
And a step B in which the high-voltage output is stopped and returned again after a required time after determining that there is an abnormality in step A, and the required time is shorter as the time from the stop of the high-voltage output to the determination of the abnormality is shorter. And C. controlling the high-voltage power supply.