JP2790639B2 - Electrophotographic equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, and further to an electrophotographic apparatus such as a printer and a facsimile.

2. Description of the Related Art Generally, an electrophotographic apparatus is provided with a plurality of AC corona discharge devices around a photoreceptor to perform charging, static elimination, and the like. Here, conventionally, a high-voltage power supply is provided for each of these corona dischargers and driven.

Problems to be Solved by the Invention According to such a conventional method, since the output frequency of the AC output high-voltage power supply is slightly different for each high-voltage power supply, the discharge sounds generated by the corona discharger interfere with each other, causing a humming sound. This causes the user of the electrophotographic apparatus to feel uncomfortable.

Further, an AC output high voltage power supply requires an AC output oscillator and the like in addition to the output control circuit, so that the configuration is complicated and expensive.

Means for Solving the Problems In an electrophotographic apparatus provided with a plurality of AC corona dischargers, a high-voltage transformer for generating an AC high voltage is connected to each of the AC corona dischargers and applied to these AC corona dischargers. The drive control means for synchronizing the frequency of the AC voltage from the AC high-voltage power supply is formed by an oscillator commonly connected to each of the high-voltage transformers.

Since the AC voltage applied to each AC corona discharger is provided by the drive control means via a high-voltage transformer connected to each AC corona discharger, the voltage by each AC corona discharger can be appropriately determined. And, since the frequency of the applied AC voltage is controlled by the drive control means so as to be synchronized, the discharge sounds also match,
No unpleasant roaring sounds.

Embodiment An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram of the configuration of the image forming section 1 in the copying machine and the high voltage power supply section 2 for corona discharge and the drive control section 3 used in the image forming section.

First, in the image forming section 1, a drum-shaped photoconductor 4 is grounded via a detection unit (hereinafter referred to as "Id detection unit") 5 for detecting a photoconductor charging current Id. The photoconductor 4 is mainly composed of selenium or the like, and is driven to rotate counterclockwise as shown by the arrow in the figure. Around the photoreceptor 4, process members including a plurality of AC corona dischargers and the like are arranged according to an electrophotographic process. That is, a charging corona discharger 6, an eraser 7, an exposure optical system 8, a developing device 10 including a developing sleeve 9, and a pre-transfer corona discharger (hereinafter referred to as a "PT corona discharger") which is one of AC corona dischargers. 11, transfer corona discharger 12, separation corona discharger 13 which is one of AC corona dischargers, and corona discharger before cleaning which is one of AC corona dischargers (hereinafter referred to as "PC corona discharger"). 14, cleaning device 17 including bias roller 15 and fur brush 16, static elimination corona discharger 1
8, quenching lamps 19 and the like are arranged in order. Further, between the PT corona charger 11 and the transfer corona discharger 12, a guide plate 20 and a feed roller (registration roller) 21 for a transfer paper entering path are provided, and a downstream side of the separation corona discharger 13 is provided. A transport device 22 is provided for feeding the transfer paper on which the image has been transferred to the fixing device side in the next step.

On the other hand, as the high-voltage power supply unit 2, a charging high-voltage power supply for the charging corona discharger 6 (hereinafter, referred to as a "C power supply").
23, a developing bias power supply (hereinafter referred to as “B power supply”) 24 for the developing sleeve 9, a pre-transfer neutralization high voltage power supply (hereinafter referred to as “PT transformer”) 25 for the PT corona discharger 10, A transfer high-voltage power supply (hereinafter referred to as “T power supply”) 26 for the transfer corona discharger 12 and a separation high-voltage power supply (hereinafter “D power supply”) for the separation corona discharger 13
27, a pre-cleaning high voltage power supply (hereinafter, referred to as “PC transformer”) 28 for the PC corona discharger 13, and a cleaning bias power supply (hereinafter, referred to as “BR power supply”) for the bias roller 15. ) 29,
A high-voltage power supply for static elimination to the static elimination corona discharger 18
30 referred to as “PQ transformer”). That is, what is indicated by the transformers 25, 27, 28 is an AC corona discharger.
It becomes a high voltage transformer as an AC high voltage power supply for 11,13,14.

These power supplies or transformers 23 to 30 are controlled mainly by a control circuit (CPU) 31 in the drive control unit 3. Therefore, these power supplies or transformers 23 to 30
Is a pulse width modulation signal P to the CPU 31 via the bus line 32.
It is connected via timers 33, 34, 35 that output WM. Among them, the DC high voltage timer 33 is a power supply for outputting the DC high voltage.
23,24,26,29,30 are connected. Also AC timer
An AC component driving circuit 36 is connected to 34, a DC component driving circuit 37 is connected to the DC component timer 35, and these driving circuits 36, 3
Reference numeral 7 is connected to transformers 25, 27, and 28 serving as AC high-voltage power supplies that output DC-biased AC. Further, the AC transformers 25, 27, and 28 are commonly connected to a 500 Hz AC oscillation circuit 38, and also commonly connected to a transformer output detection circuit 39 for detecting a high voltage output. The CPU 31 is connected to a main controller (not shown) that controls the operation of the entire copying machine by a serial communication path using an optical fiber.

In such a configuration, a copying process will be described. First, the photoconductor 4 is uniformly charged to a positive polarity (about 800 V) by corona discharge by the charging corona discharger 6. Next, the photosensitive member 4 is irradiated with reflected light from the original via an exposure optical system 8 from an original reading device (not shown), and an electrostatic latent image of the original is formed on the surface of the photosensitive member 4. This electrostatic latent image is
At 10, the toner on the developing sleeve 9 adheres in accordance with the potential of the electrostatic latent image and is visualized to form a toner image. Next, the alternating current corona discharge by the PT corona discharger 11 weakens the electrostatic attraction between the toner and the photoconductor 4. On the other hand, the transfer paper is fed to the photoconductor by the feed roller 19 at a predetermined timing, and is superimposed on the toner image. Therefore, the transfer corona discharger 12 applies an electric field having the opposite polarity to the charge (negative polarity) of the toner from the back surface of the transfer paper, and the toner image on the photoconductor 4 is transferred onto the transfer paper. At this time, since the transfer paper is electrostatically attracted to the photoreceptor 4 by the electric field in the transfer process, an AC electric field is applied from the back of the transfer paper by the separation corona discharger 13. As a result, the charge on the transfer paper is eliminated, separated from the photoreceptor 4 by its own weight, and transported by the transport device 22 to the fixing device side. Since paper dust and a small amount of untransferred toner adhere to the surface of the photoconductor 4 after separation,
After an AC electric field is applied by the PC corona discharger 14 to make the potential uniform, the toner is removed from the surface of the photoconductor 4 by the brush 16 of the cleaning device 17. The toner is removed from the brush 16 by the bias roller 15 and discharged to the waste toner tank. Next, the photoconductor 4 is a corona discharger for removing static electricity.
After the charge is removed by the DC electric field by 18, the light is removed by the charge removing lamp (quenching lamp) 19, the photosensitive member 4 returns to the initial state, and a series of image forming processes is completed.

Next, the operation of the high-voltage power supply unit 2 will be described. The control of the high-voltage power supply unit 2 is performed according to the flowchart of FIG. First, when the power is turned on, initialization is performed. In this initial setting, the count value of the DC high-voltage timer 33 and the immediately preceding values such as the target value of the constant current control and the photoconductor charging current setting mode are read from the backup memory in the main body control device and set in the CPU 31. Further, the FB interrupt timer for selecting the signal to be taken into the CPU 31 from the transformer output detection circuit 37 and setting the timing of the processing is started.
Therefore, after the setting is completed, when the trigger of the power supply and the transformer is turned on, the corresponding high voltage output is supplied to the corona discharger. In the initial setting, the photosensitive member charging current setting mode, the image forming mode, and the output abnormality process are looped, and these modes are set by an interrupt signal from the main body control device. Normally, after the photoconductor charging current setting mode is executed when the power is turned on, the process waits until the image forming mode is designated by the main body control device. In the output abnormality process, control is performed according to the load state of the transformers 25, 27, and 28.

 Next, individual functions and processes will be described.

First, a power supply and a transformer will be described. The C power supply 23, the T power supply 26, and the PQ power supply 30 in the high voltage power supply unit 2 are high voltage power supplies that output a direct current (about 6000 V) for corona discharge.
Output current is controlled by constant current. These power supplies 23,26,30
Have the same circuit configuration, for example, as shown in FIG. First, the PWM timer (DC high voltage timer) 33
Periodically as shown in Fig. 4 from the T ₁ (e.g., 1 kHz) by PWM signal (duty ratio of the period T ₂ of the L level changes = T
₂ / T ₁ × 100%) is output. For high voltage power supply, CPU31
Such PW from timer 33 based on the trigger signal from
After passing the M signal through the AND gate 41, the built-in integration circuit (D / A
The converter 43 converts the analog signal into an analog signal,
Reference voltage. The comparator 43 compares the reference voltage with the feedback signal from the output detecting means 44, and outputs the difference voltage, that is, the error signal, to a pulse width modulation circuit (PWM) 45.
Output to The pulse width modulation circuit 45 outputs a pulse signal having a time width corresponding to the error signal to the transistor 46 to drive the high voltage transformer 47. As a result, the transistor 46 performs switching with the ON / OFF duty corresponding to the error signal output from the comparator 43, and induces a high voltage on the secondary side of the high voltage transformer 47. This high voltage is converted to DC by a rectifier circuit (not shown),
It is supplied to the corona discharger 6 or 11 or 16 which is a load.
The load current is detected as a voltage by the output detecting means 44 connected to the low voltage side of the high voltage transformer 47, and is fed back to the comparator 43. The current flowing through the corona discharger 6 or 11 or 16 by this series of feedback loops is controlled at a constant current to a predetermined value (that is, the power supply itself has a control function for stabilizing the output), and the output value (load The current is a value corresponding to the duty ratio of the PWM signal output from the PWM timer 33 as shown in FIG.

As shown in FIG. 10, the reference voltage of the comparator 43 may be varied via a variable power supply VR.

Note that the B power supply 24 and the BR power supply 29 are DC output (about 600 V) bias power supplies, and control the output voltage at a constant voltage.
That is, in the power supplies 23, 26, and 30 described above, the output current is detected by the output detection means 44, but the power supplies 24 and 29 detect the output voltage and perform the constant voltage control.

Next, a PT transformer that outputs DC-biased AC
The 25, D transformer 27, and PC transformer 28 are high-voltage power supplies that output a DC-biased AC (500 Hz, 5500 vrms) for corona discharge, and control the output current at a constant current. These transformers 25, 27, and 28 have the same circuit configuration, and an example is shown in FIG. As shown in the drawing, control for stabilizing the output is performed by the CPU 31. To explain in detail, first, the AC component is a PWM timer (AC
The signal from the minute timer 34 is input to the AND gate 51 together with the trigger signal from the CPU 31. The output of the AND gate 51 causes the AC driving circuit 36 to supply a DC voltage to the primary side of the high-voltage transformer HVT1. Here, two transistors Q ₁ and Q ₂ as switch elements for generating an AC voltage in the primary winding of the high-voltage transformer HVT1 are provided at 500 Hz supplied from an oscillation circuit 38 common to all the transformers 25, 27 and 28. the pulse signal, alternately conduct in a predetermined cycle as shown in FIG. 7 (T _3/2). As a result, as shown in FIG.
The secondary side of the positive polarity period T ₄ and negative time T _5, and the peak value V ₊ and V _- AC high voltage and are each equal to the square wave is induced. At this time, although details will be described later, each transformer 25, 27, 28
, The pulse signal from the oscillation circuit 38 is shared, so that the period of the AC voltage induced on the secondary side of each of the transformers 25, 27, 28 (high-voltage transformer HVT1) is synchronized. The voltage value of this AC high voltage is supplied from the AC drive circuit 36 to the high voltage transformer HVT1.
Becomes a value proportional to the DC voltage supplied to.

This AC component driving circuit 36 includes, for example, a 2
A DC / DC converter of a jumper type comprising _three transistors Q ₃ and Q ₄ , a diode D, a diode yoke CH and a capacitor C is used. As a result, the output voltage becomes PWM
PWM supplied from the timer 34 to the base of the transistor Q ₄
The value corresponds to the duty ratio of the signal. The cycle of this PWM signal is about 20 kHz (= 0.05 ms). This PWM
The AC component of the high voltage output can be arbitrarily set by the duty ratio of the PWM signal output from the timer 34.

Next, the DC components of the transformers 25, 27 and 28 will be described with reference to FIG. The DC component is output by applying the output voltage of the high voltage transformer HVT2 between the AC component high voltage transformer HVT1 and the ground. Therefore, the load (HV-
AC voltage DC bias DC voltage V _DC as shown by the broken line in voltage V _AC of Figure 7 is supplied between the ground). The voltage of this DC component is supplied from the PWM timer 35 to the AND gate 52.
(Other input trigger signal from the CPU 31) by supplying PWM given via signal (cycle of about 20 kHz) to the base of the transistor Q ₅ is amplified by a DC component driving circuit 37, to switching-the transistor Q ₅ It is made by rectifying the high voltage induced on the secondary side of the high voltage transformer HVT2. Therefore,
Similarly to the AC component, the DC component of the high voltage output can be arbitrarily set by the duty ratio of the PWM signal output from the PWM timer 35.

Here, corona discharger 1 of these transformers 25, 27, 28
FIG. 1 shows a specific circuit configuration for synchronizing the AC outputs to 1, 13, and 14. First, the common oscillator circuit 38 has an internal oscillator OSC55 and a flip-flop F for dividing the output thereof.
/ F56 and output transistors Qi, ▲ ▼ are built in, and the transistor Q is synchronized with the oscillation output of the oscillator OSC55.
i and ▲ ▼ alternately conduct. A pair of transistors Q ₁₁ , Q ₂₁ , Q ₁₂ , Q connected respectively to the primary sides of high-voltage transformers HVT 11, HVT 12, HVT 13 for the AC of each transformer 25, 27, 28
_22, Q _13, Q among _23, each transistor Q ₆₁ transistors Q _21, Q _22, Q ₂₃ outputs a positive component of the ac output, Q _62, Q ₆₃
Is connected to the transistor Qi of the oscillation circuit 38 via the transistor Qi, and is commonly driven by the transistor Qi. On the other hand, transistors Q ₁₁ , Q
_12, Q ₁₃ are each transistors Q _71, Q _72, which is connected to the transistor ▲ ▼ of the oscillation circuit 38 via the Q _73, it is commonly driven by the transistor ▲ ▼. Accordingly, in synchronism with the transistors Qi, ▲ ▼ of the oscillation circuit 38, an in-phase AC voltage is supplied to the corona dischargers 11, 13, 14 from the respective transformers 25, 27, 28.

In FIG. 1, the high-voltage transformer HVT2 for DC in FIG. 6 includes HVT21, HVT22, HVT2 for each of the transformers 25, 27, 28.
Simplified and shown as 3. In addition, the transistors Q ₃ and CH yoke CH in the AC drive circuit 36 are also provided for each of the transformers 25, 27 and 28.
Q ₃₁ , Q ₃₂ , Q ₃₃ , CH1, CH2, and CH3 are shown.

Subsequently, output control of these transformers 25, 27, 28 will be described. Here, the output control procedure of each of the transformers 25, 27, and 28 is performed according to a flowchart of an output detection scan (see FIG. 14) described later.

Here, each output control will be described. First,
As for the output voltage and current, a detection signal detected as a low voltage by the output detection means 53 connected to the secondary winding side of the DC high voltage transformer HVT2 is selected by the output detection selection circuit 39, and the CPU 31
Input to the A / D converter.

The output current is taken at a predetermined cycle (for example, 14 ms) in accordance with the flowchart shown in FIG. 12 to perform constant current control. This constant current control uses A / D
The data is converted to digital data via a converter to perform proportional control. In the proportional control, the difference between the detection data and a preset target value (hereinafter, referred to as “error data”) multiplied by a preset proportional constant is used as a change in the PWM timer 3.
The new count value is written to the PWM timers 34 and 35 in addition to the current count value (manipulation amount) of 4,35.

Further, the output voltage is detected in a longer cycle (for example, 100 ms) than the detection of the output current, and is processed according to the flowchart shown in FIG. In this processing, the state of the load is detected by determining whether the output voltage is within the reference value, and processing according to each state is performed. First, after converting the output voltage detection signal into digital data, it is determined whether the detection data is within the reference value. Here, four reference values are provided for one high-voltage power supply. These are HLMT, HST, LST, and LLMT in descending order of voltage, as shown in FIG. If the detected data is between HST and LST, the output voltage is normal, and this process ends. Also, if the detection data is HS
If it is between T and HLMT or between LST and LLMT, the corona discharger 11, 13, or 14 is expected to be contaminated, so that the output abnormality flag FHST or FLST is set and this processing ends. . Further, when the detected data is equal to or more than HLMT or equal to or less than LLMT, since a serious abnormality is expected in the load, the output abnormality flag FHLMT or FLLMT is set, and the current processing is interrupted, and the “output Abnormal: 1 "(see Fig. 19) interrupt processing.

Next, an output detection procedure of each transformer will be described. Since the output control of each transformer is collectively performed by the CPU 31, the detection signal is fetched and processed in a predetermined procedure. Here, the output detection signals include those shown in Tables 1 and 2.

Of these detection signals, the current signals from No. 1 to No. 6 shown in Table 1 are detected and processed at a period of 14 ms, and shown in Table 2.
The voltage signals from No. 1 to No. 6 are detected and processed with a period of 84 ms. This process is performed according to the flowchart of “output detection scan” shown in FIG. This processing is executed by the FB interrupt that arrives every 2 ms in the CPU 31. In this processing, two program counters are provided. One of the I scan counters is counted each time the subroutine of FIG. 14 is executed (every 2 ms), and the other V scan counter is counted every time the I scan counter counts up (every 14 ms). You.
The count values of the respective I and V scan counters correspond to the detection signals in Tables 1 and 2.

Hereinafter, this output detection scan processing will be described with reference to the flowchart of FIG. When an FB interrupt occurs, the I scan counter is decremented and the corresponding detected value is selected. First, when the AC transformer output current PTI _AC of the PT transformer 25 is detected, it is determined whether or not the output of the PT transformer 25 is on (trigger on). If the output is off, the process is terminated. Is the output detection signal PTI _AC to A / D of CPU31.
Take in the converter. Next, the "constant current control" subroutine shown in FIG. 12 is executed, and this processing ends. Next FB
When an interrupt occurs, a DC component output current PTI _DC is detected. After that, D transformer 27, PC transformer
Regarding 28, the detection of the output current is similarly performed in the order of DI _AC , DI _DC , PCI _AC , and PCI _DC .

Thereafter, when an FB interrupt occurs further, the V scan counter is decremented next, and the "V scan" shown in FIG.
Is executed. This process also follows the process of FIG. 14, but for example, the AC voltage PTV of the first PT transformer 25
_{After AC} is detected, a subroutine of "output voltage detection" shown in FIG. 13 is executed. Next, when the I scan counter is reset and an FB interrupt occurs, the first PTI _AC
The detection is performed from. Therefore, every time the detection of the signals shown in Table 1 completes one cycle, the signals shown in Table 2 are detected one by one.

Next, a method of detecting the photoconductor charging current Id flowing through the photoconductor 4 by corona discharge in each corona discharger will be described with reference to the Id detecting means 5 shown in FIG. First, the conductive substrate 4a of the photoconductor 4 is grounded via a detection resistor Rs of, for example, 10 kΩ. Accordingly, the photoconductor charging current Id flowing through the photoconductor 4 from the corona discharge from the corona discharger is output as a voltage across the detection resistor Rs. Therefore, this detection resistor Rs
Rectifier circuit 60 for detecting the positive polarity component of the photosensitive member charging current Id, comprising a diode D ₁ , a capacitor C ₁ and a resistor R _1, and a diode D ₂ , a capacitor C ₂ and a resistor R ₂ detecting a negative polarity components of the photosensitive member charging current Id - and minute rectifier circuit 61, a diode D _3, D _4, to detect the AC component of the photosensitive member charging current Id becomes a capacitor C _3, C ₄ and the resistor R ₃ An alternating current rectifier circuit 62 is connected in parallel. The outputs of the rectifier circuits 60, 61, and 62 are independently connected to the A / D converter of the CPU 31. (Although not particularly shown, the negative rectifier circuit 61 reverses the polarity from negative to positive. Connected to the A / D converter of the CPU 31 via an inverting circuit). Therefore, the photoconductor charging current Id of positive / negative DC and AC can be detected at the same time, and the DC component (positive) included in the AC is obtained by summing the detection values of the positive and negative polarities. And a negative difference). CP in photoconductor charging current setting mode
These three types of detection signals input to the A / D converter of U31 are selected according to the corona discharger of interest.

Here, the photoconductor charging current setting mode will be described. When the photoconductor charging current Id is set to a predetermined value, the photoconductor charging current Id is substantially made constant by making it a high-current output value. That is, in the photoconductor charging current setting mode, the corona discharge is independently performed for each corona discharger, and the value of the PWM timer or the target value of the proportional control is changed so that the value detected by the Id detection unit 5 becomes a predetermined value. The output current value at the time when (predetermined photoconductor charging current) is reached is stored, and the constant current control is performed using this current value as a target value. This is because the output current Io is, as shown in FIG.
In 12 or 18), the photoreceptor charging current Id and the discharger casing current Ic are shunted. The ratio between the output current Io and the photoreceptor charging current ID (distribution ratio = 100 × Id / Io) is usually corona. Since the change only occurs due to dirt due to toner or paper dust in the discharger, a predetermined cycle (for example,
The output current Io when the power of the copier body is turned on or once a day).
This is because the constant current can be obtained even if the photoconductor charging current Id itself is not directly detected.

In this photoconductor charging current setting mode, the setting method differs between the power supplies 23, 26, 30 and the transformers 25, 27, 28. In the former, the count value of the PWM timer 33 is directly operated to set the photoconductor charging current Id, whereas in the latter, the target value of the proportional control is operated.

Therefore, the former method will be described with reference to a subroutine "Id setting: 1" in FIG. First, the output of the power supply is turned on (trigger on), and the output current at this time is based on the count value currently set in the PWM timer 33, or the standard count value set in advance if it is completely initial. Outputs the duty ratio PWM signal. Next, after waiting for several hundred ms,
The detection signal of the photoconductor charging current Id by the Id detection unit 5 is A / D converted into digital data, and it is determined whether or not the detection data is within a preset target value. If the value is within the target value, the process ends as it is.If the value is outside the target value, the current count value of the PWM timer 33 is increased or decreased.
A new count value is set in the PWM timer 33, and the processing of FIG. 16 is repeated until the detected data falls within the target value.

The latter method will be described with reference to a subroutine "Id setting: 2" in FIG. First, the subroutine "constant current control" shown in FIG. 12 is executed several times (for example, five times) to sufficiently start up the high-voltage output.
The D conversion and the determination of the detected data are performed. Here, as a result of the determination, when the detection data is out of the target value, the target value of the proportional control in the above-described “constant current control” subroutine is
The current value is increased or decreased, and the process is repeated until the detection data falls within the target value of the photoconductor charging current Id.

The processing of the photoconductor charging current setting mode will be described with reference to a subroutine shown in FIG. First, the photoconductor 4 is rotated. Next, the PQ corona discharger 18
After the discharge is performed with the output current of the count value set to 3 and the entire circumference of the photoconductor 4 is uniformly charged, the discharge is stopped. At the same time as the charging, the discharge lamp 19 is turned on to perform light discharge.
This static elimination lamp 19 is lit until this mode ends. Next, the photoreceptor charging current Id of the positive polarity due to the corona discharge of the PQ corona discharger 18 was set to "Id setting: 1" shown in FIG.
Will be described in accordance with the subroutine. Thereafter, the transfer corona discharger 12 and the charging corona discharger 6 are similarly set in accordance with “Id setting: 1”. When the charging corona discharger 6 is set, the eraser 7 is turned on to perform light elimination. next,
The setting is made for each of the corona dischargers 11, 13, and 14 which perform the DC-biased AC corona discharge. In this case, the AC component is set first, and then the DC component is set. First, after setting the AC component of the PT corona discharger 11 in accordance with the subroutine "Id setting: 2" shown in FIG.
The DC component is set using the subroutine (1). This DC component is obtained by comparing the difference between the positive and negative polarities with the target value, as described above. Next, after the entire circumference of the photoconductor 4 is uniformly charged by the PQ corona discharger 18, the PT corona As with the discharger 11, settings are made for the D corona discharger 13 and the PC corona discharger 14.

Further, the output abnormality processing will be described. In the present embodiment, the output abnormality is processed in two stages to perform the recovery work, so that the copying machine can be used as much as possible during the recovery processing, and the machine down time is shortened.

First, the subroutine of "output abnormal processing: 1" will be described with reference to FIG. At the time of executing this processing, since a serious abnormality is expected in the load, the ongoing processing is interrupted, and the processing is performed by interrupt processing. Here, when an abnormality is detected for the first time, the target value (set value) of the high voltage output is changed by a predetermined ratio (output is reduced), and a recovery process is performed. Again, when this abnormality is detected, all the high-voltage outputs are stopped and a "serviceman call" signal for prohibiting the use of the copying machine is transmitted to the main controller.

On the other hand, the subroutine "Output abnormal process: 2" will be described with reference to FIG. In this process, a process is performed when output is abnormal due to contamination of the corona discharger, and the flag FHST or FL is set in the subroutine of "output voltage detection" shown in FIG.
Executed when ST is set. When this process is executed for the first time, it is determined which flag FHST or FLST has been set. When the flag FHST is set, a request for cleaning the corona wire is sent to the main controller, and when the flag FLSY is set, a request for cleaning the casing of the corona discharger is sent to the main controller, and the "cleaner BUSY" flag is set. . In response to these cleaning requests, the main controller performs the setting of "cleaner END" and the reset of "cleaner BUSY" after the cleaning processing.
Next, even if “Cleaner END” is set, FHST or FLS
Whenever T is set, the target value of the high voltage output is changed. When the target value has been changed, a signal indicating “under abnormal processing” is transmitted. The main controller displays to the user of the copying machine that the error processing is being performed, and informs the serviceman that repair is required. This “under abnormal processing” does not prohibit the use of the copying machine.

Effect of the Invention As described above, the present invention relates to an electrophotographic apparatus having a plurality of AC corona dischargers, wherein a high-voltage transformer for generating an AC high voltage is connected to each of the AC corona dischargers, and these AC corona dischargers are connected. Since the drive control means for synchronizing the frequency of the AC voltage by the AC high-voltage power supply applied to the electric appliance is formed by an oscillator commonly connected to each of the high-voltage transformers, the AC voltage applied to each AC Morona discharger is:
Since it is given by the drive control means via a high voltage transformer connected to each AC corona discharger, the voltage by each AC corona discharger can be appropriately determined, and
Since the frequency of the applied AC voltage is controlled so as to be synchronized by the drive control means, the discharge sound also matches, and there is an effect that an unpleasant growling sound does not occur.

[Brief description of the drawings]

1 shows an embodiment of the present invention, FIG. 1 is a circuit diagram showing synchronous control of an AC output, FIG. 2 is a block diagram including a copying machine configuration, FIG. 3 is a circuit diagram of a power supply, and FIG. FIG. 5 is a waveform diagram of a PWM signal, FIG. 5 is a duty-load current characteristic diagram, and FIG.
The figure is a circuit diagram of a high voltage transformer, FIG. 7 is an operation waveform diagram thereof,
FIG. 8 is a circuit diagram of an AC drive circuit, FIG. 9 is a circuit diagram of an Id detecting means, FIG. 10 is a circuit diagram showing a modification of a power supply, FIG. 11 is a main flow chart, and FIG. FIG. 13 is a flowchart showing a subroutine of output voltage detection, FIG. 14 is a flowchart showing a subroutine of output detection scan, and FIG. 15 is a flowchart showing a subroutine of V scan scan. 16
The figure shows a flowchart showing the Id setting: 1 subroutine.
Fig. 17 is a flowchart showing the subroutine of Id setting: 2.
FIG. 18 is a flowchart showing a subroutine of a photoconductor charging current setting mode, FIG. 19 is a flowchart showing a subroutine of output abnormality processing: 1, and FIG. 20 is a flowchart showing a subroutine of output abnormality processing: 2. . 11,13,14 …… AC corona discharger, 25,27,28 …… AC high voltage power supply = high voltage transformer, 38 …… Oscillator, Q ₁₁ , Q ₂₁ , Q ₁₂ , Q ₂₂ ,
Q ₁₃ , Q ₂₃ ...... Switch element

Claims (1)

(57) [Claims] 1. An electrophotographic apparatus having a plurality of AC corona dischargers, wherein a high-voltage transformer for generating an AC high voltage is connected to each of the AC corona dischargers, and an AC high-voltage transformer is applied to these AC corona dischargers. An electrophotographic apparatus, wherein drive control means for synchronizing the frequency of an AC voltage from a power supply is formed by an oscillator commonly connected to each of the high-voltage transformers.