JPH09190870A - High voltage generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high voltage generating device which can sense failure in a corona charger and perform a proper treatment. SOLUTION: A high voltage generating device concerned is equipped with a high voltage generator circuit 1, a corona charger 2, a divided shield in three segments 21, 22, 23, divided shield current sensing circuits 51, 52, 53, an output current sensing circuit 3, a control signal generator circuit 4, a divided shield current sensing circuit 5, a charger failure diagnosing circuit 6, a judging circuit 7, and a monitor display circuit 8. It is judged as normal if the sensing values of the sensor circuits 51, 52, 53 are all within the range of allowable value. If the sensing values of the sensor circuits 51, 52, 53 are all smaller than the minimum of the allowable value, it is judged as abnormal as a failure current has flowed through other than the corona charger 2. If either of the sensing values is greater than the maximum of the allowable value, the corona discharge is concentrated on the applicable current sensor circuit, and diagnosis is such that no uniform corona discharge is made over the whole shield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage generator used for an image forming apparatus or the like.

[0002]

2. Description of the Related Art Conventionally, a high voltage generator of this type has a high voltage generating circuit for generating a high voltage at an output, a corona charger for applying the generated high voltage for corona discharge, and a high voltage output current. It is composed of an output current detection circuit for detection and a control signal generation circuit for controlling the output voltage of the high voltage generation circuit according to the detected output current value.

FIG. 4 is a circuit diagram showing the structure of a conventional high voltage generator. In the figure, 101 is a high voltage generating circuit, which includes a DC power supply 111, a transformer 112, and a transistor 1.
13, the diode 114, the capacitor 115, and the output terminal 116. Reference numeral 102 denotes a corona charger, which includes a charging wire 121 and a shield 122.
Reference numeral 103 is a resistor 131 as an output current detection circuit.
Reference numeral 104 denotes a control signal generation circuit, which includes a reference voltage 141, an amplifier 142, and a pulse width modulator 143.

[0004]

However, in the above-mentioned conventional example, the abnormal state is determined by detecting the output current of the high voltage generation circuit 101 by the output current detection circuit 103. Therefore, it is not possible to discriminate the abnormality in the corona charger 102 from the abnormality in the corona charger or the abnormality outside the corona charger. Further, since there is no means for detecting uneven charging due to the non-uniformity of corona discharge in the corona charger 102, it is difficult to properly process the abnormality.

Therefore, an object of the present invention is to provide a high-voltage generator capable of detecting an abnormality in a corona charger and appropriately treating it.

[0006]

In order to achieve the above object, a high voltage generator according to claim 1 of the present invention is a high voltage generating circuit for generating a high voltage, and the generated high voltage is applied, A corona charger that performs corona discharge, an output current detection circuit that detects the generated high-voltage output current, and a control circuit that controls the high-voltage generation circuit according to the detected output current value are provided. In the high voltage generator, a plurality of split shields provided in the corona charger, a split shield current detection circuit that detects split shield currents flowing in the split shields, and the split based on the output current of the output current detection circuit. An allowable value generation circuit that generates an allowable value of the shield current is compared with the generated allowable value and the detected divided shield current value, and the divided shield current value is within the allowable value range. Abnormality detection circuit that detects whether the detected abnormality is an abnormality in the corona charger, and the high voltage occurrence based on the detected abnormality. And an operation stop circuit for stopping the operation of the circuit.

According to a second aspect of the present invention, in the high voltage generator according to the first aspect, the abnormality detection circuit is configured such that at least one of the divided shield current values is greater than the maximum value of the permissible values, or all An abnormality is detected when the divided shield current value is smaller than the minimum allowable value, and a monitoring circuit is provided for displaying the detected abnormality according to each case.

In the high voltage generator according to claim 3, in the high voltage generator according to claim 1, the allowable value generating circuit is
An abnormality large judgment value and an abnormality small judgment value are generated outside the range of the allowable value, and the abnormality detection circuit is configured to detect an abnormality in which the divided shield current value exceeds the abnormal large judgment value and the abnormality small judgment value, and the divided shield. The current value is within the range of the abnormal large judgment value and the abnormal small judgment value and is outside the range of the allowable value, and the stop circuit detects that the split shield current value is the abnormal large judgment value or the abnormal state. The operation of the high voltage generation circuit is stopped when an abnormality exceeding a small judgment value is detected.

A high pressure generator according to a fourth aspect of the present invention is the third aspect.
In the high voltage generator according to the present invention, there is provided a monitoring circuit for displaying an abnormality in which the split shield current value is outside the allowable value range within the abnormal large judgment value and the abnormal small judgment value.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a high pressure generator of the present invention will be described.

[First Embodiment] FIG. 1 is a block diagram showing the structure of a high-voltage generator according to the first embodiment. In the figure, 1 is a high voltage generating circuit. Reference numeral 2 is a corona charger, the shield of which is composed of equally divided split shields 21, 22, 23.

Reference numeral 3 is an output current detection circuit, which includes a resistor 31,
It consists of 32 and 33. At the connection point between the resistor 31 and the resistor 32, the allowable minimum value of the split shield current is detected, and the resistor 32
The maximum allowable split shield current is detected at the connection point between the resistor 33 and the resistor 33, and the total output current value is detected at the connection point between the resistor 33 and the high voltage generation circuit 1.

Reference numeral 4 is a control signal generating circuit. Reference numeral 5 denotes a split shield current detection circuit, which is a split shield current detection circuit 51 for detecting the current of the split shield 21, a split shield current detection circuit 52 for detecting the current of the split shield 22,
And a split shield current detection circuit 53 for detecting the current of the split shield 23.

A charger abnormality diagnosis circuit 6 receives the detected values of the split shield current detection circuits 51, 52 and 53 as inputs and the allowable minimum and maximum values of the split shield current of the output current detection circuit 3 as inputs. Compare the inputs of. The charger abnormality diagnosis circuit 6 includes comparators 61 and 6 inside.
2, 63, 64, 65, 66, 3-input AND gate 6
It consists of 7 and 4 input OR gates 68.

Reference numeral 7 is a determination circuit, which receives the output of the charger abnormality diagnosis circuit 6 as an input and determines whether or not the input signal is truly abnormal. The output of the determination circuit 7 is sent to the high voltage generation circuit 1, and when there is a true abnormality, the generation operation of the high voltage generation circuit 1 is stopped and the output of the high voltage generation circuit 1 is cut off. Judgment circuit 7
Can be realized by various circuit configurations. For example, it is configured by a two-input AND gate that receives an output of a time constant circuit composed of a capacitor and a resistor and an output of the charger abnormality diagnosis circuit 6,
It may be a true abnormality when the abnormality signal continues for a certain period of time.

Reference numeral 8 is a monitor display circuit for displaying the diagnosis result of the charger abnormality diagnosis circuit 6 on the monitor. The monitor display circuit 8 includes buffer circuits 81, 82, 83, 84,
Resistors 85, 86, 87, 88 and LEDs 89, 9
It is composed of 0, 91 and 92.

FIG. 2 is a circuit diagram showing the configuration of the corona charger 2 and the split shield current detection circuit 5. The detection value of the split shield current detection circuit 51 is the charger abnormality diagnosis circuit 6
Are input to the comparators 61 and 64, respectively. Similarly, the detection value of the split shield current detection circuit 52 is input to the comparators 62 and 65 of the charger abnormality diagnosis circuit 6, respectively, and the detection value of the split shield current detection circuit 53 is the comparator 63 of the charger abnormality diagnosis circuit 6. , 66 respectively.

The maximum allowable split shield current value from the output current detection circuit 3 is used as the input to be compared by the comparators 61, 62 and 63. Further, the minimum allowable value of the split shield current from the output current detection circuit 3 is used for the inputs compared by the comparators 64, 65, 66. When the detected values of the split shield current detection circuits 51, 52 and 53 are larger than the maximum value of the split shield current allowable values generated from the output current detection circuit 3, the comparators 61, 62 and 63 determine that they are abnormal and output them. Generate an H level signal.

The comparators 64, 65, 66 are considered to be abnormal when the detection values of the split shield current detection circuits 51, 52, 53 are smaller than the minimum allowable split shield current value generated from the output current detection circuit 3. H at its output
Generate a level signal.

The outputs of the comparators 61, 62 and 63 and the outputs of the comparators 64, 65 and 66 are used as inputs and 3
The output from the input AND gate 67 is input to the 4-input OR gate 68. The output of the 4-input OR gate 68 is input to the determination circuit 7.

On the other hand, the output of the comparator 61 is supplied to the LED 89 via the buffer circuit 81 and the resistor 85 of the monitor display circuit 8. Similarly, the output of the comparator 62 is supplied to the LED 90 via the buffer circuit 82 and the resistor 86 of the monitor display circuit 8 and the comparator 6
3 is supplied to the LED 91 via the buffer circuit 83 and the resistor 87 of the monitor display circuit 8, and the output of the comparator 64 is the buffer circuit 84 of the monitor display circuit 8.
And is supplied to the LED 92 via the resistor 88.

Split shield current detection circuits 51, 52, 5
When the detected value of 3 is outside the range of the allowable value of the split shield current, the LE of the monitor display circuit 8 is changed according to each case.
D89, 90, 91 and 92 are lit and displayed.

Here, the corona charger 2 is composed of the divided shields 21, 22 obtained by dividing the shield of the corona charger into three equal parts.
It is equipped with 23. Split shields 21, 22, 2
Reference numeral 3 is a shield, which is electrically insulated from each other (see FIG. 2). The insulation strength is about several tens of volts. The split shields 21, 22, 23 are connected to the split shield current detection circuits 51, 52, 53, respectively. The divided shield current detection circuits 51, 52, 53 are the constant voltage power source 5
A positive current is supplied from 4, and the detection value of the split shield current, which is a negative current, is detected as a positive detection value by a circuit composed of three resistors and is output to the charger abnormality diagnosis circuit 6 of the next stage.

As described above, in the high voltage generator of this embodiment, the split shield current detection circuits 51, 5 are provided.
It is normal if the detected values of 2, 53 are all within the allowable range. On the other hand, the split shield current detection circuits 51, 52, 5
If all the detected values of 3 are smaller than the minimum allowable value, it means that an abnormal current has flowed other than the corona charger 2, and the abnormality is diagnosed. Further, the split shield current detection circuits 51, 52,
If any of the detected values of 53 is larger than the maximum allowable value, corona discharge concentrates on the divided shield current detection circuit, and it is diagnosed that uniform shield is not performed on the entire shield. That is, when an abnormality of corona discharge occurs, it is possible to diagnose whether the abnormality is outside the corona charger 2 or inside the corona charger 2, and moreover, where the abnormality inside the corona charger 2 is.

[Second Embodiment] FIG. 3 is a block diagram showing the structure of a high-voltage generator according to the second embodiment. The same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In the figure, 9 is a multiplexer (MPX), which receives the detection values of the split shield current detection circuits 51, 52 and 53 as input, and selects and outputs the input by a timing signal (not shown).

A resistor 3 newly provided in the output current detection circuit 3
For Nos. 4 and 35, a level difference is provided between the allowable value of the split shield current and the abnormal value of the split shield current, and the level is set outside the allowable value of the split shield current but difficult to determine as abnormal. It is a thing. That is, the level is set to a level which is smaller than the minimum allowable value of the split shield current, but is not so small as to be abnormal due to the resistor 34. Also, a level is set that is larger than the maximum allowable value of the split shield current, but not so large as abnormal.

Reference numeral 10 denotes a split shield current abnormality large determination circuit, which inputs the detection values of the split shield current detection circuits 51, 52, 53 via a multiplexer 9 and outputs the abnormality large determination value input for comparison. It is input from the current detection circuit 3 and output via the comparator 10a, the multiplexer 10b, the latch circuits 10c, 10d, 10e and the 3-input OR gate 10f. That is, when any of the detection values of the split shield current detection circuits 51, 52, and 53 is larger than the abnormality determination value, a signal indicating abnormality is output.

Reference numeral 11 denotes a split shield current abnormality small determination circuit which inputs the detection values of the split shield current detection circuits 51, 52 and 53 via a multiplexer 9 and outputs an abnormality small determination value input for comparison. It is input from the current detection circuit 3 and output via the comparator 11a, the multiplexer 11b, the latch circuits 11c, 11d, 11e and the 3-input OR gate 11f. That is, if any of the detection values of the split shield current detection circuits 51, 52, and 53 is smaller than the abnormality smallness determination value, the abnormality small signal is output.

Reference numeral 12 denotes a split shield current out-of-allowance value determination circuit, which inputs the detection values of the split shield current detection circuits 51, 52, 53 via a multiplexer 9 and outputs an allowable value range input for comparison. Input from the current detection circuit 3, comparators 12a, 12b, 2-input AND gate 12c, multiplexer 12d, latch circuit 12e, 1
Outputs via 2f, 12g and a 3-input OR gate 12h. That is, the split shield current detection circuits 51, 5
If any of the detected values of 2 and 53 is outside the range of the allowable value of the split shield current, a signal outside the range of the allowable value is output.

Reference numeral 14a is a monitor display circuit composed of a resistor and an LED, and a split shield current abnormality large determination circuit 10 is provided.
Is connected to the output of the monitor, and when it is determined that the split shield current is abnormally large, the LED is turned on to perform monitor display.
Reference numeral 14b is a monitor display circuit including a resistor and an LED, which is connected to the output of the split shield current abnormality small determination circuit 11 and is L when it is determined that the shield current is abnormally small.
The ED is turned on and the monitor is displayed. Reference numeral 14c is a monitor display circuit composed of a resistor and an LED, which is connected to the output of the split shield current out-of-allowance value determination circuit 12 and emits an LED when it is determined that the split shield current is out of the tolerance
Is lit to display the monitor.

Reference numeral 13 denotes a 2-input OR gate, which is a high voltage generation circuit 1 when the divided shield current is abnormally large or abnormally small as a result of the judgment by the divided shield current abnormally large judgment circuit 10 and the divided shield current abnormal small judgment circuit 11. The signal to stop the operation of is output.

The output of the split shield current out-of-allowance value determination circuit 12 is connected to a drive circuit for a charging wire cleaning member (not shown), and the split shield current out-of-allowance value determination circuit 12 is connected.
Is outside the allowable shield current value, it is used as a start signal for the drive circuit of the charging wire cleaning member.

As described above, in the high voltage generator according to the present embodiment, an abnormal state, which is outside the allowable range of the split shield current but does not stop the output of the high voltage, for example, simple wire adjustment. When the charging wire can be repaired by cleaning the charging wire, particularly when the charging wire can be cleaned automatically (electrically), the abnormal state can be eliminated by instructing the cleaning of the charging wire.

[0034]

According to the high voltage generator of the first aspect of the present invention, a high voltage is generated by the high voltage generation circuit, and corona discharge is performed by the corona charger to which the generated high voltage is applied. When detecting the generated high voltage output current by the current detection circuit and controlling the high voltage generation circuit according to the detected output current value by the control circuit, the divided shield current detection circuit causes the corona charger to operate. The divided shield current flowing through the plurality of divided shields provided is detected, and the allowable value generation circuit generates the allowable value of the divided shield current based on the output current of the output current detection circuit, and the generated allowable value. The detected divided shield current value is compared, and the abnormality detection circuit detects that the divided shield current value is out of the allowable range. It is determined whether or not the detected abnormality is an abnormality in the corona charger, and the operation stop circuit stops the operation of the high voltage generation circuit based on the detected abnormality. It is possible to discriminate whether the discharge abnormality is caused by or the discharge abnormality other than the corona charger. Further, by dividing the shield of the corona charger into two or more, it is possible to identify whether the state of corona discharge in the corona charger is uniform or uneven. Further, by setting the shield current depending on the characteristics of the high voltage generation circuit and the corona charger, the allowable value and the abnormal value of the split shield current can be set with high accuracy.

It is normal if the detected values of the split shield current are all within the allowable range. On the other hand, if the detected values of the split shield current are all smaller than the minimum allowable value,
An abnormal current has flowed to other than the corona charger. If any of the split shield current values is larger than the maximum allowable value, it is determined that the corona discharge concentrates on the split shield where the large split shield current has flowed, and uniform corona discharge is not performed on the entire shield. it can. That is,
When an abnormality in corona discharge occurs, it can be diagnosed whether it is an abnormality other than the corona charger or an abnormality inside the corona charger, and when it is an abnormality inside the corona charger, what part of the abnormality is The abnormal discharge condition can be diagnosed. Therefore, appropriate processing can be performed according to the abnormality.

According to a second aspect of the present invention, in the abnormality detecting circuit, when at least one of the divided shield current values is larger than the maximum value of the allowable values, or all of the divided shield current values are the above-mentioned. An abnormality is detected when it is smaller than the minimum allowable value, and a monitoring circuit for displaying the detected abnormality according to each case is provided. Therefore, the abnormality occurrence and the specific abnormality content can be grasped by the monitor display.

According to another aspect of the high voltage generator of the present invention, the allowable value generation circuit generates the abnormal large judgment value and the abnormal small judgment value outside the range of the allowable value, and the abnormal condition detection circuit,
An abnormality in which the split shield current value exceeds the abnormal large judgment value and the abnormal small judgment value, and the divided shield current value is outside the allowable value range within the abnormal large judgment value and the abnormal small judgment value. When an abnormality is detected and the stop circuit detects an abnormality in which the split shield current value exceeds the abnormality large judgment value or the abnormality small judgment value, the operation of the high voltage generation circuit is stopped. An abnormal condition that is out of range but does not stop the output of high voltage, for example, when it can be repaired by simple wire adjustment or cleaning of the charging wire, especially when the charging wire can be cleaned automatically (electrically). The abnormal state can be eliminated by instructing to clean the charging wire. For example, as the charging wire cleaning instruction signal, a signal indicating an abnormality in which the split shield current value of the abnormality detection circuit is outside the allowable value range within the abnormal large determination value and the abnormal small determination value may be used.

According to the high voltage generating apparatus of the fourth aspect, the monitoring circuit for displaying an abnormality in which the split shield current value is within the range of the abnormal large judgment value and the abnormal small judgment value and is outside the range of the allowable value. As a result, it is possible to know that the split shield current value is outside the allowable value range, and as a countermeasure, it is possible to understand on the monitor display that there is an abnormality that cannot be handled by adjusting the charging wire, cleaning the charging wire, etc. Is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a high-voltage generator according to a first embodiment.

FIG. 2 is a circuit diagram showing configurations of a corona charger 2 and a split shield current detection circuit 5.

FIG. 3 is a block diagram showing a configuration of a high voltage generator according to a second embodiment.

FIG. 4 is a circuit diagram showing a configuration of a conventional high voltage generator.

[Explanation of symbols]

 1 High voltage generation circuit 2 Corona charger 3 Output current detection circuit 4 Control signal generation circuit 5 Split shield current detection circuit 6 Charger abnormality diagnosis circuit 7 Judgment circuit 8 Monitor display circuit

Claims (4)

[Claims] 1. A high voltage generation circuit for generating a high voltage, a corona charger to which the generated high voltage is applied to perform corona discharge, and an output current detection circuit for detecting the generated high voltage output current. And a control circuit for controlling the high-voltage generating circuit according to the detected output current value, wherein a plurality of split shields provided in the corona charger and splits flowing in the split shield are provided. A split shield current detection circuit for detecting a shield current, a tolerance value generation circuit for generating a tolerance value of the split shield current based on an output current of the output current detection circuit, a generated tolerance value and the detected An abnormality detection circuit that compares the divided shield current value and detects that the divided shield current value is outside the allowable range, and the detected abnormality is the corona band. An abnormality determination circuit that determines whether an abnormality in the vessel, the detected abnormal based, high-pressure apparatus, characterized by comprising an operation stop circuit stops the operation of the high voltage generating circuit. 2. The abnormality detection circuit is abnormal when at least one of the divided shield current values is larger than the maximum value of the allowable value or when all the divided shield current values are smaller than the minimum value of the allowable value. 2. The high voltage generator according to claim 1, further comprising a monitoring circuit for detecting the abnormality and displaying the detected abnormality according to each case. 3. The tolerance value generation circuit generates an abnormality large determination value and an abnormality small determination value outside the range of the tolerance value, and the abnormality detection circuit determines that the split shield current value is the abnormality large determination value and the abnormality large determination value. An abnormality exceeding a small abnormality judgment value and an abnormality in which the divided shield current value is outside the allowable value range within the abnormality large judgment value and the abnormality small judgment value are detected, and the stop circuit divides the division current. 2. The high voltage generating apparatus according to claim 1, wherein the operation of the high voltage generating circuit is stopped when an abnormality is detected in which the shield current value exceeds the abnormal large judgment value or the abnormal small judgment value. 4. A monitoring circuit for displaying an abnormality in which the split shield current value is outside the allowable value range within the abnormal large judgment value and the abnormal small judgment value. 3. The high pressure generator according to 3.