JP2002365982A - Imaging device and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly apply optimal transfer voltage to a transfer roller, in the case of image forming operation in an imaging device of an electronic photograph system. SOLUTION: Voltage to be applied to the transfer roller 5 is measured by making fixed current flow through the roller 5, before image forming. In the case of imaging, output voltage based on the measured voltage value is applied to the roller 5. When an abnormality detection means detects abnormality of the output voltage, in the case of measuring the voltage to be applied to the roller before imaging, an error signal is transmitted to the controller 13 of an imaging device body, to stop the output of high voltage to the roller 5. When abnormality of the output current is detected, a signal to the effect that the measurement of the voltage to be applied to the roller before image forming is unsuccessful, is transmitted to the controller 13 of the imaging device body, to intermittently output-operate the output of the high voltage to the roller 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine and a printer and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a latent image is formed by exposing a charged rotating drum to light, toner is adhered to the latent image, transferred to a plain paper, and this is repeated. Thereby, a plurality of copies are generated. At this time, in the step of transferring to paper, a high voltage is applied to the photosensitive drum via a conductive rubber transfer roller in roller transfer. Since the resistance value of the transfer roller changes depending on the environment such as temperature and humidity, the production lot, the material, etc., the optimum transfer voltage applied to the transfer roller in order to perform the transfer most efficiently also varies depending on the environment and various conditions. It changes under various conditions.

Conventionally, this optimum transfer voltage has been set to ATVC (A
uto ・ Transfer ・ Voltage ・ Cont
orol) is determined by the following method.

Prior to image formation, a constant current is applied to the transfer roller to measure the voltage across the transfer roller.

At the time of image formation, an optimum voltage value for image formation based on the voltage value measured in step (1) is applied to the transfer roller.

That is, since the impedance of the transfer roller can be calculated by the equation (1), it is possible to apply an optimum transfer voltage according to a change in the external environment.

Further, in the above-mentioned conventional example, in terms of safety of the device,
Means for detecting a transfer output abnormality are provided. If an output voltage abnormality is detected during the transfer roller impedance measurement above, the transfer high voltage output is stopped, an error signal is returned to the image forming apparatus main body, and the output current In some cases, when an abnormality is detected, an intermittent operation is performed with respect to the output of the transfer high voltage to protect the output of the transfer high voltage to a level at which there is no problem in safety.

[0008]

However, in the conventional image forming apparatus as described above, if an output current abnormality is detected during the impedance measurement of the transfer roller,
Since the intermittent operation is performed for the output of the transfer high voltage, the output of the transfer high voltage is suppressed to a level that does not pose a problem for safety, but the current that is improper Despite the value, the impedance of the transfer roller is measured, so that there is a problem that an optimum transfer voltage cannot be applied to the transfer roller during the image forming operation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an image forming apparatus capable of always applying an optimum transfer voltage to a transfer roller during an image forming operation, and a control method thereof. It is an object.

[0010]

An image forming apparatus and a control method therefor according to the present invention are configured as follows.

(1) A transfer high-voltage power supply for supplying a high voltage from an output terminal to a transfer roller; voltage detecting means for detecting a voltage at the output terminal; current detecting means for detecting a current flowing through the transfer roller; Control means for determining a set output voltage at the output end according to the impedance of the transfer roller;
It has an abnormality detecting means for detecting an abnormality of an output current from the output end and an abnormality of an output voltage, and measures a voltage applied to the transfer roller by flowing a constant current to the transfer roller before forming an image, and At the time of formation, an output voltage based on the measured voltage value is applied to the transfer roller, and when an abnormality of the output voltage is detected by the abnormality detection unit at the time of measuring the voltage applied to the transfer roller before the image formation, The high-voltage output to the transfer roller is stopped by transmitting an error signal to the controller of the image forming apparatus main body, and when an abnormality of the output current is detected, the voltage applied to the transfer roller before the image formation is measured. A signal indicating the failure is transmitted to the controller of the image forming apparatus main body, and the high voltage output to the transfer roller is intermittently output.

(2) In the above (1), if an abnormality in the output current is detected during the measurement of the voltage applied to the transfer roller before image formation, the voltage applied to the transfer roller before image formation is detected. A signal indicating that the measurement has failed is transmitted to the controller of the main body of the image forming apparatus, the high voltage output to the transfer roller is intermittently output, and the voltage applied to the transfer roller is measured again.

(3) a transfer high-voltage power supply for supplying a high voltage from an output terminal to a transfer roller; voltage detecting means for detecting a voltage at the output terminal; current detecting means for detecting a current flowing through the transfer roller; Control means for determining a set output voltage at the output end according to the impedance of the transfer roller;
A method for controlling an image forming apparatus, comprising: an abnormality detecting unit that detects abnormality of an output current and an output voltage from the output terminal, wherein a constant current is applied to the transfer roller before image formation, and The applied voltage is measured, and at the time of image formation, an output voltage based on the measured voltage value is applied to the transfer roller, and when the voltage applied to the transfer roller before the image formation is measured, the output voltage is output by the abnormality detection unit. If an abnormal voltage is detected, an error signal is transmitted to the controller of the image forming apparatus main body to stop outputting high voltage to the transfer roller. If an abnormal output current is detected, the transfer before the image formation is performed. A signal indicating that the measurement of the voltage applied to the roller has failed is transmitted to a controller of the image forming apparatus main body, so that the high voltage output to the transfer roller is intermittently output.

(4) In the above (3), if an abnormality in the output current is detected at the time of measuring the voltage applied to the transfer roller before image formation, the voltage applied to the transfer roller before image formation is detected. A signal indicating that the measurement has failed is transmitted to the controller of the main body of the image forming apparatus, the high voltage output to the transfer roller is intermittently output, and the voltage applied to the transfer roller is measured again.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a block diagram showing the structure of a first embodiment of the present invention, and shows the structure of a high-voltage transfer power supply 1 constituting an electrophotographic image forming apparatus.

In FIG. 1, reference numeral 2 denotes one of the transfer transformers T1.
A voltage control circuit for controlling a voltage applied to the next main winding NP1, and a transistor Tr connected to the main winding NP1
Thereby, the transfer transformer T1 is driven. 3 is an oscillator (OS) that drives the transistor Tr at a constant frequency.
C), 4 is a current detection circuit (current detection means) for detecting an output current flowing to the transfer roller 5 as a load, and the alternating current generated in the output winding NS1 on the secondary side of the transfer transformer T1 is a diode D2 and a capacitor C2. Thus, the voltage at the output end, which is rectified and smoothed, is applied to the transfer roller 5. R1 is a bleeder resistor.

In FIG. 1, 6 and 14 are comparators, and 7 is D /
A conversion circuit, 8 is a register, 9 is an A / D conversion circuit, 10
Denotes a multiplexer, and 11 denotes a voltage detection circuit (voltage detection means) for detecting the voltage at the output terminal, which comprises a primary detection winding NP2 of the transfer transformer T1, a rectifying diode D1, and a smoothing capacitor C1. Have been. 12
Denotes a CPU for a high voltage power supply, and 13 denotes a controller of the main body of the image forming apparatus.

Although not shown, the transfer high-voltage power supply 1 is provided with output abnormality detecting means for detecting an abnormality in the output current and an abnormality in the output voltage.

In the transfer high-voltage power supply 1 configured as described above, the output of the current detection circuit 4 is
Is input to the A / D conversion circuit 9 to be subjected to analog-digital conversion and input to the CPU 12. The output of the voltage detection circuit 11 is also taken into the A / D conversion circuit 9 via the multiplexer 10, is subjected to analog-digital conversion, and is input to the CPU 12. The CPU (control means) 12 obtains an optimum transfer voltage based on the taken output voltage and output current, and sets the set value in the register (setting means) 8.

The set value of the register 8 is digital-to-analog converted by a D / A conversion circuit 7 and input to a comparator 6. The comparator 6 compares the output value of the D / A conversion circuit 7 with the detection value of the voltage detection circuit 11, and the voltage control circuit 2 is controlled by the output of the comparison result, so that the transfer output becomes a desired value. Thus, the voltage applied to main winding NP1 is controlled.

The comparator 14 compares the output value of the D / A conversion circuit 7 with the detection value of the current detection circuit 4, and the voltage control circuit 2 is controlled by the output of the comparison result, so that the transfer output current is reduced. Control is performed so as to have a desired value.

FIG. 2 is a cross-sectional view showing a main configuration of an electrophotographic image forming apparatus to which the transfer high-voltage power supply 1 of FIG. 1 is applied.

In FIG. 2, reference numeral 21 denotes a photosensitive drum. The photosensitive drum 21 is uniformly charged by a charger 22 and then irradiated with image light 23 to form an electrostatic latent image. 24
To form a toner image on the photosensitive drum. Then, the toner image is transferred onto the recording medium 26 by the transfer roller 5, further fixed by the fixing roller 27, and then discharged. At this time, a positive electric field is applied to the transfer roller 5 from the transfer high-voltage power supply 1 so that the negative toner is easily transferred to the recording medium 26.

Next, the measurement of the impedance of the transfer roller 5 performed before the image forming operation will be described.

First, a predetermined set value is set in the register 8 by the CPU 12 in order to supply a constant current to the transfer roller 5, and the set value is digital-to-analog converted by the D / A conversion circuit 7. . Then, D /
The output value of the A conversion circuit 7 and the output value of the current detection circuit 4 are compared, and the voltage control circuit 2 is controlled by the comparison output so that the transfer output current becomes a desired value.

At this time, the voltage detected by the voltage detecting circuit 11 including the detecting winding NP2 of the transfer transformer T1, the rectifying diode D1, and the smoothing capacitor C1 is supplied to the A / D converter circuit via the multiplexer 10. 9 and is converted from analog to digital.
Is input to The CPU 12 obtains an optimum voltage value applied to the transfer roller 5 at the time of image formation based on the taken output voltage, sets the set value in the register 8 at the time of image forming operation, and sets the voltage applied to the transfer roller 5 to this value. The voltage is controlled so as to be optimal for performing image formation determined in this manner.

Here, an operation in the case where an abnormality in the transfer high voltage output is detected by the output abnormality detecting means during the impedance measurement of the transfer roller 5 performed before the above-described image forming operation will be described.

FIG. 3 is a flowchart showing the sequence operation of the image forming apparatus according to the present embodiment.
(Constant current) shows a sequence for performing ATVC measurement. The control processing shown in this flowchart is executed by the CPU 12 in FIG. 1 according to a program stored in advance.

First, the ATVC measurement is started (S1).
If an abnormal output of the transfer voltage is detected during the TVC measurement (S2), the output voltage is detected by the output voltage detecting circuit 11 and is converted from analog to digital via the multiplexer 10 and the A / D converting circuit 9 (S3). If the detected value exceeds the output voltage abnormality detection value set on the program memory (not shown) of the CPU 12, it is determined that the output voltage is abnormal, and C
A signal for stopping the output is input from the PU 12 to the oscillator 3, whereby the transfer high voltage output is stopped. Also, in this case, an error signal notifying that the transfer high voltage output voltage is abnormal is returned to the controller 13 of the image forming apparatus main body, thereby stopping the image forming operation on the main body side, and confirming that the high voltage output voltage is abnormal. The information is transmitted to the image forming apparatus main body side (S5).

If an abnormal output of the transfer current is detected during the ATVC measurement (S4), the output current is detected by the output current detection circuit 4, and the multiplexer 10, the A / D conversion circuit 9
The detected value analog-to-digital converted through CP is CP
When the output current abnormality detection value set on the program memory (not shown) of U12 is exceeded, it is determined that the output current is abnormal, and a signal for stopping the output is input from the CPU 12 to the oscillator 3, whereby the transfer high voltage output is output. Stops. When the transfer high-voltage output stops, the detection value detected by the output current detection circuit 4 also decreases.

When the output current drops to the current detection value of the high-voltage output stop release level set in advance in the program memory of the CPU 12, the output automatically returns to the high voltage output, and the abnormality of the current is detected again. When the output current reaches a certain level, an intermittent oscillation operation is performed such that the high voltage output is stopped again. In this case, AT
By returning the VC failure signal to the controller 13 of the image forming apparatus main body, the fact that ATVC was not correctly performed is transmitted to the image forming apparatus main body side (S6).

By performing such control, an optimal transfer voltage can be always applied to the transfer roller 5 during the image forming operation.

[Embodiment 2] FIG. 4 is a block diagram showing the configuration of a second embodiment of the present invention. The same reference numerals as in FIG. 1 denote the same components. FIG. 5 is a flowchart showing the operation of the present embodiment, and the same step numbers as those in FIG. 3 indicate the same processing contents. The control process shown in this flowchart is executed by the CPU 12 of FIG. 4 according to a program stored in advance.

The second embodiment differs from the first embodiment in that when an output current abnormality is detected during the impedance measurement of the transfer roller 5 performed before the image forming operation, the first embodiment is different from the first embodiment. In this embodiment, the ATVC failure signal is returned to the controller 13 of the image forming apparatus main body to inform the image forming apparatus main body that the ATVC has not been correctly performed.
The re-measurement signal is input to the CPU 12 and the ATVC measurement is performed again, thereby making it possible to further improve the reliability.

[0036]

As described above, according to the present invention,
If the current value flowing through the transfer roller to measure the impedance of the transfer roller performed before the image forming operation is an inappropriate current value such that an abnormal output current is detected, the impedance of the transfer roller is measured. It is possible to recognize that the transfer has not been performed correctly, so that an optimum transfer voltage can always be applied to the transfer roller during the image forming operation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a main part of the image forming apparatus.

FIG. 3 is a flowchart showing a sequence operation of the first embodiment.

FIG. 4 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a flowchart showing a sequence operation of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transfer high voltage power supply 2 Voltage control circuit 3 Oscillator 4 Current detection circuit 5 Transfer roller 6, 14 Comparator 7 D / A converter 8 Register 9 A / D converter 10 Multiplexer 11 Voltage detection circuit 12 High voltage power supply CPU 13 Image forming apparatus body controller

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H027 DA01 DA50 DE04 DE07 EA03 EF10 EH10 EK03 EK15 HA12 ZA01 2H200 FA11 FA18 GA23 GA33 GB25 HA12 HB12 HB22 HB48 JA02 JA28 JA29 JA30 NA02 NA14 NA16 NA18 PA03 PA10 PA22 PA28 PB02P

Claims (4)

[Claims] A transfer high-voltage power supply for supplying a high voltage from an output end to a transfer roller; voltage detection means for detecting a voltage at the output end; current detection means for detecting a current flowing through the transfer roller; Control means for determining a set output voltage at the output end in accordance with the impedance of the roller; and abnormality detection means for detecting an abnormality in the output current and an abnormality in the output voltage from the output end, and the transfer before the image formation. A constant current is applied to the roller to measure a voltage applied to the transfer roller.At the time of image formation, an output voltage based on the measured voltage value is applied to the transfer roller, and applied to the transfer roller before the image formation. If an abnormality in the output voltage is detected by the abnormality detecting means during the measurement of the voltage, an error signal is transmitted to the controller of the image forming apparatus main body to stop the high voltage output to the transfer roller. If an abnormality in the output current is detected, a signal indicating that the measurement of the voltage applied to the transfer roller before the image formation has failed is transmitted to the controller of the image forming apparatus main body to output a high voltage to the transfer roller. An image forming apparatus for performing an intermittent output operation. 2. When an output current abnormality is detected during measurement of a voltage applied to the transfer roller before image formation, it is reported that the measurement of the voltage applied to the transfer roller before image formation has failed. 2. The image according to claim 1, wherein a signal to the effect is transmitted to a controller of the image forming apparatus main body, a high voltage output to the transfer roller is intermittently output, and a voltage applied to the transfer roller is measured again. Forming equipment. 3. A transfer high-voltage power supply for supplying a high voltage from an output end to a transfer roller; voltage detection means for detecting a voltage at the output end; current detection means for detecting a current flowing through the transfer roller; A control method for an image forming apparatus, comprising: a control unit that determines a set output voltage of the output terminal according to an impedance of a roller; and an abnormality detection unit that detects an abnormality of an output current from the output terminal and an abnormality of the output voltage. Therefore, before forming an image, a constant current is applied to the transfer roller to measure a voltage applied to the transfer roller.At the time of image formation, an output voltage based on the measured voltage value is applied to the transfer roller. If an abnormality in the output voltage is detected by the abnormality detecting means at the time of measuring the voltage applied to the transfer roller before image formation, an error signal is transmitted to a controller of the image forming apparatus main body to transfer the error. The high voltage output to the transfer roller is stopped, and if an abnormality in the output current is detected, a signal indicating that the measurement of the voltage applied to the transfer roller before the image formation has failed is sent to the controller of the image forming apparatus main body. A method for controlling an image forming apparatus, wherein a high voltage output to a transfer roller is transmitted to perform an intermittent output operation. 4. When an output current abnormality is detected during measurement of a voltage applied to the transfer roller before image formation, a notification that the measurement of the voltage applied to the transfer roller before image formation has failed is provided. 4. A signal to that effect is transmitted to a controller of the main body of the image forming apparatus, whereby a high voltage output to the transfer roller is intermittently output, and the voltage applied to the transfer roller is measured again. The control method of the image forming apparatus described in the above.