JP2017026659A - Image formation device, transfer device used in the same, power supply device used therein, and method for controlling power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device with which it is possible to avoid the accidental breakage of a circuit element included in the power supply device without lowering power efficiency even when there is a fluctuation of load.SOLUTION: Provided is a power supply device that repeatedly operates in order to transfer a toner image formed on an image carrier from the image carrier to a medium to which it is to be transferred, after removing a toner remaining on the image carrier from the image carrier, the power supply device comprising: a first power supply circuit for generating a cleaning bias for removing a toner from the image carrier; a second power supply circuit for generating a transfer bias for transferring a toner image from the image carrier to a medium to which it is to be transferred; and means which, when it is detected that a period before the generation of a transfer bias is started by oscillation of an oscillation unit of the second power supply circuit after the second power supply circuit received an indication to generate a transfer bias is prolonged, reduces a reverse current at the output terminal of the power supply device that is obstructing the oscillation of the oscillation unit and thereby quickens the start of oscillation of the oscillation unit.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus for forming an image, a transfer device used therefor, a power supply device used therefor, and a power supply device control method, and more particularly to an electrophotographic image forming apparatus and a transfer device used therefor. The present invention also relates to a power supply device used therefor and a power supply device control method.

  An electrophotographic image forming apparatus includes a transfer device that applies a transfer voltage for transferring a toner image of an image carrier toward a transfer member disposed opposite to the image carrier to the image carrier or the transfer member. I have. Examples of the combination of the image carrier and the transfer member include a photosensitive member and an intermediate transfer member, an intermediate transfer member and a secondary transfer member, and a photosensitive member and a paper transport belt.

  The toner remaining on the surface of the image carrier after the toner image is transferred is cleaned by an image carrier cleaning member to cause deterioration of image quality in the next image forming process. May adhere to the surface. The toner adhering to the surface of the transfer member may cause contamination of paper or the like during subsequent image forming processing, and thus the surface of the transfer member needs to be cleaned. If the transfer member is provided with a dedicated cleaning member, the transfer device Increases in size.

  Therefore, the conventional transfer device includes a first power supply unit that outputs the cleaning voltage at a constant voltage and a second power supply unit that outputs the transfer voltage having a polarity opposite to the cleaning voltage at a constant current. (For example, refer to Patent Document 1).

  The image forming apparatus includes a transfer period in which the toner image is transferred from the image carrier to the transfer target while a toner image is formed on the image carrier, and a cleaning period in which the toner remaining on the image carrier is removed. The cycle is repeated.

  FIG. 1 shows a power supply apparatus including a first power supply unit 912 that outputs a cleaning voltage at a constant voltage and a second power supply unit 914 that outputs a transfer voltage having a polarity opposite to the cleaning voltage at a constant current. An example of what is provided in the transfer device will be described.

  The constant voltage output from the first power supply unit 912 and the constant current output from the second power supply unit 914 are alternately given to the image carrier.

  Here, if the constant voltage output by the first power supply unit 912 to the image carrier is finished, the constant current output by the second power supply unit 914 is not always started immediately. In particular, when the image forming apparatus is installed in a humid environment and the capacity Ca of the image carrier is larger than usual, a current 916 in the direction opposite to the direction of constant current output from the capacity Ca included in the image carrier is generated. It may flow into the power supply. In such a case, the oscillation start of the oscillation circuit including the transistor TR941 included in the second power supply unit 914 is delayed, and accordingly, the output of the transfer voltage with a constant current is also delayed. If such a delay is repeated, the transistor TR941 may be damaged.

  In Patent Document 2, the above-described reverse current flows by operating not only the transfer voltage power supply but also the cleaning voltage power supply during the period in which the transfer voltage is output, thereby avoiding the start-up failure. A possible invention is disclosed.

JP-A-10-32979 JP 2014-202999 A

However, in the invention disclosed in Patent Document 2, since it is necessary to operate the power supply for the cleaning voltage even during the transfer period, the power efficiency is lowered, and the circuit components generate heat more than necessary.

  Therefore, the present invention provides a power supply device capable of avoiding damage to circuit elements included in the power supply device even when the load varies, without lowering power efficiency, a transfer device including the power supply device, and the like An image forming apparatus including the image forming apparatus and a power supply device control method.

  According to the present invention, the toner remaining on the image carrier is removed from the image carrier during the cleaning period, and then the toner image formed on the image carrier is transferred from the image carrier during the transfer period. A power supply device that repeatedly operates to transfer to a body, a first power supply circuit for generating a cleaning bias for removing toner from the image carrier, and toner from the image carrier to the transfer target A second power supply circuit for generating a transfer bias for transferring an image; and an oscillation unit of the second power supply circuit oscillates after the second power supply circuit receives an instruction to generate the transfer bias. If it is detected that the period until the start of the generation of the transfer bias is prolonged, at least the reverse current at the output terminal of the power supply device that inhibits the oscillation of the oscillation unit is reduced. By an oscillation control means to advance the start of oscillation of the oscillation portion, the power supply apparatus comprising: a is provided.

  In addition, according to the present invention, there is provided a transfer device including the power supply device described above.

  Furthermore, according to the present invention, there is provided an image forming apparatus comprising the power supply device described above.

  Furthermore, according to the present invention, a photosensitive drum, a charging unit for charging the photosensitive drum, an exposure unit for forming a latent image on the photosensitive drum charged by the charging unit, and the exposure unit The latent image formed by developing the toner image with toner and forming a toner image on the photosensitive drum; and the toner image formed on the photosensitive drum by the developing unit on the transfer body And an image forming apparatus using the transfer device according to claim 10 as the transfer unit.

  Further, according to the present invention, after the toner remaining on the image carrier is removed from the image carrier during the cleaning period, the toner image formed on the image carrier is removed from the image carrier during the transfer period. A power supply device control method for controlling a power supply device that repeatedly operates to transfer to a transfer target, wherein the power supply device generates a cleaning bias for removing toner from the image carrier. And a second power supply circuit for generating a transfer bias for transferring a toner image from the image carrier to the transfer target. The power supply device control method includes the second power supply circuit. Is detected that the period from when the instruction to generate the transfer bias is received until the generation of the transfer bias is started due to oscillation of the oscillation unit of the second power supply circuit is detected. And an oscillation control step for accelerating the start of oscillation of the oscillating unit by at least reducing a reverse current at an output terminal of the power source unit that inhibits oscillation of the oscillating unit. Is provided.

  Furthermore, according to the present invention, there is provided a power supply device control program for causing a computer to function as the above power supply device.

  ADVANTAGE OF THE INVENTION According to this invention, it can avoid that the circuit element contained in a power supply device is damaged even if there is a fluctuation | variation of load, without reducing power efficiency.

It is a circuit diagram which shows an example of the normal power supply device used with a transfer apparatus. 1 is a conceptual diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a conceptual diagram illustrating a photosensitive drum and a plurality of units around it according to the first embodiment of the present invention. 5 is a flowchart for explaining the operation of the image forming apparatus according to the embodiment of the present invention. 1 is a circuit diagram showing a power supply device according to a first embodiment of the present invention used in a transfer device. FIG. 6 is a block diagram illustrating a general configuration of a control unit illustrated in FIG. 5 and the like. It is a timing diagram for demonstrating the operation | movement of the power supply device by the 1st Embodiment of this invention, and it especially sees the switching from a cleaning period to a transfer period on a long time scale. FIG. 8 is a timing diagram for explaining the operation of the power supply device according to the first embodiment of the present invention in a normal environment, and particularly shows an enlarged view of a portion indicated by a broken line frame in FIG. 7. FIG. 8 is a timing diagram for explaining the operation when no countermeasure is taken in the high-humidity environment of the power supply device according to the first embodiment of the present invention, and in particular, an enlarged view of a portion indicated by a broken-line frame in FIG. 7. It is. FIG. 8 is a timing diagram for explaining the operation in the case where a countermeasure is taken in the humid environment of the power supply device according to the first embodiment of the present invention, and in particular, an enlarged view of a portion indicated by a broken line frame in FIG. 7. It is. It is a circuit diagram which shows only the difference with the power supply device by the 1st Embodiment of this invention of the power supply device by the 2nd Embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
An image forming apparatus including a secondary transfer unit which is a transfer apparatus according to the present invention will be described with reference to FIG. As shown in FIG. 2, as an example, the image forming apparatus 100 includes a process unit 1, an intermediate transfer unit 2, a secondary transfer unit 3, a power supply unit (corresponding to the power supply device of the present invention) 10, and a control unit 20. The image forming process is performed on a recording medium (paper or the like) using an image data input from an external device (not shown) based on an instruction from the control unit 20.

  The process unit 1 includes an exposure unit 11 and photosensitive drums 12A to 12D. The process unit 1 irradiates image light based on the image data from the exposure unit 11 to form electrostatic latent images on the surfaces of the photosensitive drums 12A to 12D, and supplies toner to visualize the electrostatic latent images as toner images. To do. In more detail with reference to FIG. 3, in addition to the photosensitive drums 12A to 12D respectively corresponding to the exposure unit 11 and the four colors YMCK, the process unit 1 includes a charging unit 53 and a developing unit 55 for each color. A cleaning unit 57 and a power-extinguishing unit 51 are provided.

  The charging unit 53 charges the photosensitive drum 12 by corona discharge or the like. The exposure unit 11 forms a latent image on the photosensitive drum charged by the charging unit 53. The developing unit 55 develops the latent image formed by the exposure unit 11 with toner, and forms a toner image on the photosensitive drum 12. As will be described later, the primary transfer roller 24 is used to transfer the toner image formed on the photosensitive drum 12 to the intermediate belt 21. The cleaning unit 57 is used to remove toner remaining on the photosensitive drum 12 after transfer. The power extinguishing unit 51 extinguishes power before the photosensitive drum 12 is charged.

  The intermediate transfer unit 2 includes an intermediate transfer belt (corresponding to the image carrier of the present invention) 21, a driving roller (corresponding to the transfer member of the present invention) 22, a driven roller 23, primary transfer rollers 24A to 24D, and And a cleaning unit 25. The intermediate transfer belt 21 is stretched around the driving roller 22 and the driven roller 23, and moves along a circulation path that passes through the photosensitive drums 12D, 12C, 12B, and 12A in this order. The primary transfer rollers 24A to 24D are disposed so as to face the photosensitive drums 12A to 12D with the intermediate transfer belt 21 interposed therebetween. The primary transfer rollers 24 </ b> A to 24 </ b> D primarily transfer the toner images formed on the surfaces of the photosensitive drums 12 </ b> A to 12 </ b> D to the surface of the intermediate transfer belt 21 in order by applying a primary transfer voltage.

  The secondary transfer unit 3 includes a secondary transfer belt (corresponding to a transfer body of the present invention) 31 and a secondary transfer roller 32. The secondary transfer roller 32 is grounded.

  The driving roller 22 is connected to the power supply unit 10 (corresponding to a part of the power supply apparatus of the present invention), and is applied between the intermediate transfer belt 21 and the secondary transfer belt 31 by application of the secondary transfer voltage. The toner image is secondarily transferred from the intermediate transfer belt 21 to a sheet passing through the next transfer position (corresponding to the transfer target of the present invention). The cleaning unit 25 removes the toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer of the toner image to the paper.

  A sensor 41 is disposed on the upstream side of the secondary transfer position in the paper transport direction. The sensor 41 detects the passage of paper.

  As shown in FIG. 6, the control unit 20 includes a CPU 201, a ROM 202, a RAM 203, and a motor driver 204, and is connected to the sensor 41, the motor 42, the power supply unit 10, and the operation unit 40.

  The CPU 201 reads out a control program recorded in the ROM 202 and executes the control program using the RAM 203 as a working area. The CPU 201 outputs drive data to the motor driver 204 at a predetermined timing in the image forming process. The motor driver 204 selectively supplies power to the rotatable motor 42 based on the drive data. Further, the CPU 201 controls the power supply unit 10 to selectively apply the secondary transfer voltage and the cleaning voltage to the drive roller 22.

  The operation unit 40 receives an instruction to start an image forming process from the user. The motor 42 is connected to a drive roller 22 that stretches the intermediate transfer belt 21, a roller that stretches the secondary transfer belt 31, and the like, and rotates these rollers when power is supplied.

  As shown in FIG. 5, the power supply unit 10 includes a first power supply circuit 101 that outputs a cleaning voltage, a second power supply circuit 201 that outputs a transfer voltage, and a control unit 301 that controls them. As shown, it is connected to a drive roller 22.

  Under the control of the control unit 301 or the like, the first power supply circuit 101 converts the cleaning voltage of the first polarity to a constant voltage and outputs it to the load during the cleaning period. Also, under the control of the control unit 301, the second power supply circuit 201 makes the transfer voltage of the second polarity opposite to the first polarity constant and outputs it to the load during the transfer period.

  In addition, the CPU 201 outputs a constant cleaning voltage to the load during the cleaning period, and outputs a constant current transfer voltage to the load during the transfer period. A switching function for switching the power supply circuit 201 is realized by executing a program.

  Further, the CPU 201 uses the switching function to change the switching transition time from the start of switching from the cleaning period to the transfer period until the second power supply circuit 201 starts outputting the transfer voltage with a constant current. If it is detected that the switching transition time is exceeded, the control function for performing the control for setting the switching transition time after the next time within the normal range is realized by executing the program.

  Further, when the operation unit 40 receives an instruction to start the image forming process, the CPU 201 starts the image forming process. The image forming process includes an image forming process for forming a toner image on the surface of the photoconductive drums 12A to 12D, a transfer process for transferring the toner image from the photoconductive drums 12A to 12D to a sheet via the intermediate transfer belt 21, and A fixing process for fixing the toner image transferred to the paper is included. Hereinafter, the transfer process in the CPU 201 will be described with reference to FIG. Note that the sheet is conveyed at a predetermined timing.

  As shown in FIG. 4, the CPU 201 waits until the transfer processing start timing comes (S11). The CPU 201 rotates the motor 42 at the start timing (S12). As the motor 42 rotates, the intermediate transfer belt 21 and the secondary transfer belt 31 move along the circulation path.

  The CPU 201 applies a primary transfer voltage to the primary transfer rollers 24A to 24D (S13). As a result, the toner images carried on the photosensitive drums 12 </ b> A to 12 </ b> D are transferred to the surface of the intermediate transfer belt 21.

  The CPU 201 and the control unit 301 control the first power supply circuit 101 so that the cleaning voltage is output at a constant voltage (S14), and the second power supply circuit 201 is output so that the secondary transfer voltage is output at a constant current. Control (S15). As a result, a secondary transfer voltage under constant current control is applied to the drive roller 22, and the toner image carried by the intermediate transfer belt 21 is transferred onto the paper.

  The CPU 201 waits until the sensor 41 detects the trailing edge of the sheet (S16). When the sensor 41 detects the trailing edge of the paper, the CPU 201 determines whether there is next image data (S17). If there is image data, the CPU 201 returns to the process of S13.

  The CPU 201 and the drive unit 301 stop applying the primary transfer voltage when there is no image data (S18). The CPU 201 controls the second power supply circuit 201 so as to stop the output of the secondary transfer voltage (S19), and controls the first power supply circuit 101 so as to output the cleaning voltage at a constant voltage (S20). As a result, a cleaning voltage under constant voltage control is applied to the drive roller 22, and the toner adhering to the secondary transfer belt 31 is transferred to the intermediate transfer belt 21. The toner attached to the surface of the intermediate transfer belt 21 is removed by the cleaning unit 25.

  The CPU 201 waits for a predetermined time to elapse after the cleaning voltage is made constant and output (S21). The predetermined time is the time required for the secondary transfer belt 31 to make one revolution.

  When a predetermined time has elapsed, the CPU 201 controls the first power supply circuit 1010 to stop the output of the cleaning voltage (S22), and stops the rotation of the motor 42 (S23).

  Next, the power supply device according to the first embodiment will be described in detail.

  FIG. 5 is a circuit diagram showing the configuration of the power supply device and its peripheral part according to the embodiment of the present invention.

  Referring to FIG. 5, the power supply device according to the embodiment of the present invention includes a power supply unit 10 and a control board 20 having a function of controlling the power supply unit 10. Since the power supply unit 10 generates a high voltage, it is also referred to as a high voltage substrate. The high voltage generated by the power supply unit 10 is applied to the image carrier that is the load 30.

  The high-voltage board 10 includes a first power supply circuit 101, a second power supply circuit 201, and a drive unit 301.

  The first power supply circuit 101 is for supplying a cleaning voltage as a constant voltage to the image carrier during a cleaning period in which the image carrier has a cleaning function, and the second power supply circuit 201 is transferred to the image carrier. This is for supplying the transfer voltage at a constant current to the image carrier during the transfer period for providing the function.

  In the cleaning period, the first power supply circuit 101 causes the voltage Va of the second output terminal 201-4 of the second power supply circuit 201, which is also the output terminal of the high-voltage substrate 10, to be a predetermined value Vx. Further, the second power supply circuit 201 causes the current Ia flowing through the second output terminal 201-4 of the second power supply circuit 201 to have a predetermined value Iy during the transfer period, and at this time, the voltage of the output terminal 201-4 Becomes Vy.

  The outputs of these power supply circuits 101 and 201 are connected in series, and both function alternately as power supplies so that the other does not function as a power supply during the period when one functions as a power supply. Accordingly, the high-voltage substrate 10 periodically functions as a power source for cleaning and a power source for transfer.

  The first power supply circuit 101 includes a first main control signal input terminal 101-1, a power supply input terminal 101-2, a first output terminal 101-3, a second output terminal 101-4, and a sub control signal input terminal 101-5. Prepare. The second power supply circuit 201 includes a second main control signal input terminal 201-1, a power input terminal 201-2, a first output terminal 201-3, and a second output terminal 201-4. A description of grounding is omitted here.

  The first main control signal input terminal 101-1 is a terminal for inputting a first main control signal for controlling ON / OFF of the first power supply circuit 101 and a voltage generated by the first power supply circuit 101.

  The power supply input terminal 101-2 is a terminal for the first power supply circuit 101 to receive power supply from a DC power supply voltage. In the example of FIG. 5, the power input terminal 101-2 is supplied with a DC power supply voltage of 24 volts.

  The first power supply circuit 101 generates a voltage between the first output terminal 101-3 and the second output terminal 101-4 so that the voltage Va of the output terminal 201-4 becomes a predetermined value Vx during the cleaning period. Let The first output terminal 103-3 is grounded.

  The sub control signal input terminal 101-5 is introduced according to the present invention, and inputs the sub control signal generated by the control board 20.

  The second main control signal input terminal 201-1 is a terminal for inputting a second main control signal for controlling on / off of the second power supply circuit 201 and a current generated by the second power supply circuit 201.

  The power input terminal 201-2 is a terminal for the second power supply circuit 201 to receive power supply from the DC power supply voltage. In the example of FIG. 5, the power input terminal 201-2 is supplied with a DC power supply voltage of 24 volts.

  The second power supply circuit 201 generates a transfer current at the second output terminal 201-4. The first output terminal 201-3 is connected to the second output terminal 101-4 of the first power supply circuit 101. The second output terminal 201-4 is connected to the drive roller 22 that is the load 30. The equivalent circuit of the load 30 is a parallel circuit of a capacitor Ca and a resistor Ra as shown in FIG. Here, the intermediate transfer belt 21 exists between the driving roller 22 and the ground, and the parallel circuit of the capacitor Ca and the resistor Ra shown in FIG. 5 is a combination of the driving roller and the intermediate belt 21 shown in FIG. It is a corresponding equivalent circuit.

  Further, as described above, during the period in which the first power supply circuit 101 functions as a cleaning power supply, the second power supply circuit 201 does not function as a power supply, and the second power supply circuit 201 functions as a transfer power supply. Both power supply circuits alternately function as power supplies so that the first power supply circuit 101 does not function as a power supply during a certain period. Therefore, the high voltage substrate 10 periodically generates a constant voltage for cleaning and a constant current for transfer alternately.

  Referring further to FIG. 5, the first power supply circuit 101 includes resistors R111, R113, R115, capacitors C121, C123, Cb, inductances L131, L133, L135, a transistor TR141, diodes D151, D153, and an electromagnetic steel plate 161. The first power supply circuit 101 further includes a switch opening / closing circuit 417, a switch SW163, and a capacitor C165 according to the present invention.

  The inductances L131, L133, L135, and the electromagnetic steel plate 161 constitute a first transformer. In this first transformer, the inductance L131 is on the input side (primary side), and the inductance L133 is on the output side (first secondary side). The inductance L135 is on the feedback side (second secondary side). The capacitors C121 and C123 and the inductance L135 constitute a first resonance circuit. The transistor TR141 is connected to the first resonance circuit via the resistor R213, and an AC signal is generated in the inductance L133 by the first oscillation circuit including the first transformer, the first resonance circuit, the transistor TR141, and the like. Further, the transistor TR141 is connected to the amplifier 305 via the resistor R111, and on / off of oscillation and amplitude of oscillation (accordingly, on / off of alternating voltage and alternating current in the inductance L133) by the output voltage of the amplifier 305. Voltage and alternating current values) are controlled.

  The AC voltage generated in the inductance L133 is basically converted into a DC voltage by a rectifier circuit including diodes D151 and D153, a resistor R115, and a capacitor Cb. In addition, when the switch SW163 is ON, the capacitor C165 also forms this rectifier circuit.

  The -CV control command output from the control unit 413 is supplied to one input terminal of the amplifier 305, and the control signal output from the -CV control circuit 307 is supplied to the other input terminal of the amplifier 305. The -CV control circuit 307 detects the output voltage at the second output terminal 201-4 of the second power supply circuit 201 by a predetermined method, and makes the output voltage become a predetermined voltage corresponding to the cleaning voltage. A control signal is supplied to the amplifier 305.

  The second power supply circuit 201 includes resistors R211, R213, R215, capacitors C221, C223, inductances L231, L233, L235, a transistor TR241, diodes D251, D253, and an electromagnetic steel plate 261.

  The inductances L231, L233, L235, and the electromagnetic steel plate 261 constitute a second transformer. In the second transformer, the inductance L231 is on the input side (primary side), and the inductance L233 is for output (first secondary side). The inductance L235 is for feedback (second secondary side). The capacitors C221 and C223 and the inductance L235 constitute a second resonance circuit. The transistor TR241 is connected to the second resonance circuit via the resistor R213, and an AC signal is generated in the inductance L233 by the second oscillation circuit including the second transformer, the second resonance circuit, the transistor TR241, and the like. The transistor TR241 is connected to the amplifier 315 via the resistor R211, and on / off of oscillation and the amplitude of oscillation (accordingly, on / off of AC voltage and AC current in the inductance L233 are determined by the output voltage of the amplifier 315. Voltage and alternating current values) are controlled.

  The alternating voltage and alternating current generated in the inductance L233 are converted into a direct current for transfer by a rectifier circuit including diodes D251 and D253, a resistor R215, and capacitors C225 and C227.

  Further, the + CC control command output from the control unit 413 is supplied to one input terminal of the amplifier 315, and the control signal output from the + CC control circuit 317 is supplied to the other input terminal of the amplifier 315. The + CC control circuit 317 detects the output current at the second output terminal 201-4 of the second power supply circuit 201 by a predetermined method (for example, a method of providing a detection element between the resistor R115 and the ground), and this output current. Supplies a control signal to the amplifier 315 so that a predetermined current corresponding to the transfer voltage becomes a predetermined current.

  Although it has already been described that the high-voltage substrate 10 functions periodically and alternately as a power source for cleaning and a power source for transfer, the control unit 413 periodically performs the first power supply circuit 101. A signal indicating an instruction (−CV control instruction) for controlling active / inactive of the signal and a signal indicating an instruction (+ CC control instruction) for controlling active / inactive of the second power supply circuit 201 are complementary. Are output alternately. That is, the control unit 413 determines that if one of the signals becomes an active level (a level corresponding to function enable) in the first half of each cycle and an inactive level (a level corresponding to function disable) in the second half of the cycle, These signals are output so that the other signal becomes inactive level (level corresponding to function invalidity) and becomes active level (level corresponding to function validity) thereafter in synchronization with the other signal.

FIG. 7 shows that at time t ₁ , the signal indicating the −CV control command changes from the active level (level corresponding to ON) to the inactive level (level corresponding to OFF), and at the same time, the signal indicating the + CC control command is It is a wave form diagram which shows a mode that it changes from an active level (level corresponding to OFF) to an active level (level corresponding to ON). Ideally, the high-voltage board 10 outputs −500 V at the output terminal 201-4 before this transition, and outputs a voltage corresponding to +40 microamperes after this transition.

  FIG. 8 shows the output voltage (voltage at the terminal 101-4) Vb of the first power supply circuit 101, the output voltage (voltage at the terminal 201-4) Va of the second power supply circuit 201, and the second power supply during normal operation. FIG. 8 is a waveform diagram showing a base voltage of a transistor TR241 included in a circuit 201, and has a common time axis with the waveform diagram of FIG.

During the period from time t _a1 to time t _a2 , the output voltage Va rises from −500 V to a voltage corresponding to +40 microamperes, and during the period from time t _b1 to time t _b2 , the output voltage Vb is − It rises from 800V to 0V. Here, since time t ₁ = time t _a1 = time t _b1 and time t _a2 = time t _b2 are substantially established, in consideration of the voltage value before and after the rise, in this period,
Va> Vb
The relationship is established. Therefore, the length of the period T1 from the time t _c1 (= t ₁ ) when the base potential of the transistor TR241 becomes equal to or higher than the threshold value from 0 V to the time t _c2 when the oscillation of the base potential of the transistor TR241 starts is normal. TR241 will not be destroyed.

  When the image forming apparatus is placed in a normal environment, the capacity of the transfer belt as a load hardly fluctuates, but when the image forming apparatus is placed in a high humidity environment, the capacity of the transfer belt as a load increases. End up. That is, the capacitance Ca included in the load in the equivalent circuit shown in FIG. When the capacitance Ca increases, the period during which the voltage at the output terminal 201-4 rises from the voltage set for the cleaning period to the voltage corresponding to the current set for the transfer period becomes longer.

This will be described with reference to FIGS. 8 and 9. When the value of the load capacitance Ca is in the normal range, the rise time (= time t _a2 −t _a1 ) as shown in FIG. If the value of the capacitance Ca becomes large, the rise time (= time t ^′ _a2 −t _a1 ) as shown in FIG. 9 is prolonged. In such a case, a starting failure of the transistor TR241 occurs.

  FIG. 9 is a waveform diagram showing the output voltage Vb of the first power supply circuit 101, the output voltage Va of the second power supply circuit 201, and the base voltage of the transistor TR241 during abnormal operation (when a start-up failure of the transistor TR241 occurs). Yes, as in FIG. 8, the waveform diagram of FIG. 7 and the time axis are common.

The period from time _{t a1} to time t _^'a2, the output voltage Va from -500 V, and rises to a voltage corresponding to + 40 microamperes, the period from time _{t b1} to time _{t b2,} the output voltage Vb, Increase from -800V to 0V. Here, a time _{t 1} = time _{t a1} = time _{t b1,} and, the period of ^'because _a2 is almost established and, from time _{t 1} time ^t' time _{t a2} = time _{t b2} <time t to _a2 In the early part of
Va> Vb
The relationship is established, but in the subsequent parts, this relationship is not established,
Va <Vb
The relationship is established. That is, the voltage Vb of the output terminal 101-4 or the output terminal 201-3 becomes larger than the voltage Va of the output terminal 201-4. As a result, in the second power supply circuit 201, a current flows from the first output terminal 201-3 to the second output terminal 201-4. Since this current is a current in the opposite direction to the normal current, it is referred to as a reverse current. When a reverse current flows between the first output terminal 201-3 and the second output terminal 201-4 of the second power supply circuit 201, no induced reverse voltage is generated in the feedback inductance L235, so that the transistor TR241 is not easily connected. It can no longer be turned off. That is, a period T2 from time t _c1 (= t ₁ ) when the base potential of the transistor TR241 becomes equal to or higher than the threshold value from 0 V to time t _c2 when the oscillation of the base potential of the transistor TR241 starts is compared with the normal period T1. It will be long. If this continues for many cycles, the transistor TR241 may be thermally destroyed.

  In the present embodiment, such thermal destruction is avoided by using the principle described below according to the present invention.

If it is detected in the second power supply circuit 201 that the rise time (= time t _a2 −t _a1 ) is prolonged to the rise time (= time t ^′ _a2 −t _a1 ) in a certain cycle, as shown in FIG. After the next cycle, the rise time (= time t _b2 −t _b1 ) is also set to rise time (= time t ^′ _b2 −t ^′ _b1 ) (where time t ^′ _b2 ) in the first power supply circuit 101 accordingly. ≒ time t _^'a2) prolong up. That is, in the first power supply circuit 101, the time for the voltage Vb of the second output terminal 101-4 to rise from −800V to 0V is lengthened. By doing this, as always,
Va> Vb
Can maintain the relationship. In this way, it is possible to prevent a reverse current from occurring between the first output terminal 201-3 and the second output terminal 201-4 of the second power supply circuit 201, and accordingly, the starting failure of the transistor TR241 can be prevented. It will be possible to prevent it. Further, even if the rise time (= time t _a2 −t _a1 ) in the second power supply circuit 201 is prolonged to the rise time (= time t ^′ _a2 −t _a1 ), a constant current corresponding to the transfer voltage starts to flow to the load. The period can be as usual.

In the present embodiment, in each cycle, the base voltage of the transistor TR241 maintains the threshold value or higher after the level of the signal indicating the -CV control command changes from the level corresponding to inactive to the level corresponding to active. The counter 411 measures the maintenance period T. The maintenance time T is the period T1 when normal, but the period T2 when abnormal. In order to detect that the period T1 changes to the period T2, a predetermined threshold Tth (where T1 <Tth = T2−ΔT) is stored inside or outside the PCU 201, and the control unit 413
T> Tth
In the next cycle, the first power supply circuit 101 extends the rise time (= time t _b2 −t _b1 ) to the rise time (= time t ^′ _b2 −t _b1 ) in the next cycle. Output extension command.

Although partially overlapping with what has already been described, in the first power supply circuit 101, the time constant of the rectifier circuit provided on the output side of the inductance L133 is that the resistor R115 and the capacitor Cb when the switch SW163 is OFF. The time constant of the circuit constituted by R115 × Cb
However, when the switch SW163 is ON, the time constant R115 × (Cb + C165) of the circuit constituted by the resistor R115 and the capacitors Cb and C165
It becomes.

Therefore, when an extension command is issued, the switch SW163 is switched from OFF to ON via the switch opening / closing control unit 215 and the switch opening / closing circuit 417, thereby increasing the time constant of the rectifier circuit, and thereby the first power supply. The rise time (= time t _b2 −t _b1 ) can be extended to the rise time (= time t ^′ _b2 −t _b1 ) between the output terminals 101-3 and 101-4 of the circuit 101.

By doing this, as described above, as always,
Va> Vb
Will be able to maintain the relationship. Accordingly, it is possible to prevent a start-up failure of the transistor TR241.

As described above, if it is detected in a certain cycle that the period T during which the base voltage of the transistor TR241 is maintained above the threshold exceeds the predetermined threshold Tth, the first power supply circuit 101 in the next cycle , By increasing the time constant of the rectifier circuit provided on the output side of the inductance L133, and always between the voltage Va of the output terminal 201-4 and the voltage Vb of the output terminal 201-3 as in the normal state,
Va> Vb
To be able to maintain a relationship.

  Here, the increased time constant may be maintained until the copying machine is turned off, and the time constant may be returned to a normal value when the copying machine is turned on again.

  Also, considering that the environment around the copier does not change frequently, after increasing the time constant, the specified number of sheets can be maintained while maintaining the time constant even if the copier is turned on / off. (Or copying over a predetermined number of days) and then returning the time constant to the normal value.

In any case, if it is detected again that the period T during which the base voltage of the TR 241 is above the threshold exceeds the predetermined threshold Tth, or if it is detected a predetermined number of times For example, after the next time, a similar process for extending the rise time (= time t _b2 −t _b1 ) to the rise time (= time t ^′ _b2 −t _b1 ) is performed.

[Second Embodiment]
In the first embodiment, the switch SW163 and the capacitor C165 are connected in series, and the three elements including the capacitor SW, the capacitor Cb, and the resistor R115 are connected in parallel.

  This is merely one configuration for making the time constant of the rectifier circuit provided on the output side of the inductance L133 longer in the first power supply circuit 101 than in the normal state when it is abnormal. If the same thing can be done, it may be realized by other configurations.

For example, as shown in FIG. 11, a switch SW163 ′ and an additional resistor R117 are connected in parallel, this and a resistor R115 are connected in series, and this is connected in parallel with a capacitor Cb. Then, the switch SW163 ′ is turned ON during normal operation, and the time constant of the rectifier circuit is
R115 x Cb
When the switch SW163 is turned off at the time of abnormality, the time constant of the rectifier circuit is
(R115 + R117) × Cb
It is good.

  The first embodiment and the second embodiment may be combined so that the time constant of the rectifier circuit at the time of abnormality is larger than the time constant of the rectifier circuit at the time of normal operation.

[Third Embodiment]
In the first embodiment and the second embodiment, if the period T during which the base voltage of the transistor TR241 is maintained at or above the threshold exceeds the predetermined threshold Tth, the inductance L133 in the first power supply circuit 101 is obtained. The time constant of the rectifier circuit provided on the output side is increased to a predetermined time constant. The predetermined time constant here is always between the voltage Va of the output terminal 201-4 and the voltage Vb of the output terminal 201-3, as in the normal state.
Va> Vb
This is set with a margin so that the relationship can be maintained.

On the other hand, in the third embodiment, the time constant of the rectifier circuit provided on the output side of the inductance L133 is set between the voltage Va at the output terminal 201-4 and the voltage Vb at the output terminal 201-3. ,
Va> Vb
Increase gradually until you can maintain the relationship. By doing so, it is possible to avoid unnecessarily increasing the time constant of the rectifier circuit provided on the output side of the inductance L133.

[Fourth Embodiment]
In the first embodiment to the third embodiment, during the cleaning period, the first power supply circuit 101 determines that the voltage at the second output terminal 201-4 of the second power supply circuit 201 corresponds to the cleaning voltage. In the transfer period, the second power supply circuit 201 is controlled so that the current at the second output terminal 201-4 of the second power supply circuit 201 becomes a constant current corresponding to the transfer voltage. It was supposed to be.

  In the fourth embodiment, for example, as in JP 2014-153374 A, the first power supply circuit 101 is controlled to be a constant current source corresponding to the cleaning voltage in the cleaning period, and in the transfer period, The first power supply circuit 101 is controlled to be a constant voltage source corresponding to the cleaning voltage, and the second power supply circuit 201 is controlled to be a constant current source corresponding to the transfer voltage. Good.

  Note that the power supply device described above can be realized by hardware, software, or a combination thereof. In addition, the method for controlling the power supply device described above can also be realized by hardware, software, or a combination thereof. Here, “realized by software” means realized by a computer reading and executing a program.

  The program may be stored using various types of non-transitory computer readable media and supplied to the computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD- R, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  The present invention can be used for a power supply device used in a transfer device.

3 Secondary transfer unit 10 Power supply unit (high voltage substrate)
20 Control Unit 21 Intermediate Transfer Belt 22 Drive Roller 22
30 Load 31 Secondary transfer belt 100 Image forming apparatus 101 First power supply circuit 201 Second power supply circuit 301 Drive unit R115 Resistor TR141, TR241 Transistor SW163 Switch Cb, C165 Capacitor

Claims (15)

To remove toner remaining on the image carrier from the image carrier during a cleaning period, and then transfer the toner image formed on the image carrier from the image carrier to a transfer body during a transfer period. A power supply that operates repeatedly,
A first power supply circuit for generating a cleaning bias for removing toner from the image carrier;
A second power supply circuit for generating a transfer bias for transferring a toner image from the image carrier to the transfer target;
It has been detected that the period from when the second power supply circuit receives the instruction to generate the transfer bias until the transfer bias is started due to the oscillation of the second power supply circuit oscillating is prolonged. Then, an oscillation control means for speeding up the start of the oscillation of the oscillation unit by at least reducing a reverse current at the output terminal of the power supply device that inhibits the oscillation of the oscillation unit;
A power supply apparatus comprising: The power supply device according to claim 1,
The oscillation control means adjusts the rate of change of the output voltage at the output terminal of the first power supply circuit in accordance with the rate of change of the voltage at the output terminal, thereby at least reducing the reverse current. Power supply. The power supply device according to claim 2,
The first power supply circuit includes two output terminals,
The second power supply circuit also includes two output terminals,
The first output terminal of the first power supply circuit is directly or indirectly grounded, the second output terminal of the first power supply circuit is connected to the first output terminal of the second power supply circuit, and the second power supply circuit The second output terminal is an output terminal of the power supply device,
The second power supply circuit connected to the second output terminal of the first power supply circuit in accordance with the voltage change rate at the second output terminal of the second power supply circuit, which is the output terminal of the power supply device. A power supply apparatus that adjusts a voltage between two output terminals of the second power supply circuit by adjusting a rate of change of an output voltage at one output terminal. The power supply device according to any one of claims 1 to 3,
The first power supply circuit outputs a cleaning voltage having a first polarity to the output terminal of the power supply device as the cleaning bias,
The second power supply device outputs a current corresponding to a transfer voltage having a polarity opposite to the first polarity as the transfer bias. The power supply device according to claim 4,
The first power supply circuit includes:
A first oscillation circuit using a first transformer;
A first rectifier circuit connected to a secondary coil of the first transformer;
Constant voltage control means for controlling the first rectifier circuit to output the cleaning voltage to an output terminal of the power supply device;
With
The oscillation control means adjusts a time constant of the first rectifier circuit to at least reduce a reverse current at an output terminal of the power supply device that inhibits oscillation of the oscillation unit. . The power supply device according to claim 5,
The power supply apparatus according to claim 1, wherein the oscillation control means includes means for adjusting a time constant of the first rectifier circuit by changing a value of a resistor and / or a capacitor included in the first rectifier circuit. The power supply device according to any one of claims 4 to 6,
The second power supply device
A second oscillation circuit including a second transformer and a positive feedback control unit for generating a transmission signal by performing positive feedback control on the second transformer;
A second rectifier circuit connected to the secondary side of the second transformer;
Constant current means for controlling the second rectifier circuit to flow a constant current corresponding to the transfer voltage to the output terminal of the power supply device;
With
The oscillation control means controls the second oscillation circuit as the oscillation unit. The power supply device according to any one of claims 1 to 7,
The power supply apparatus according to claim 1, wherein the oscillation control unit performs the control with a period of switching from the cleaning period to the transfer period as a minimum unit. The power supply device according to claim 8, wherein
The switching control means performs the control stepwise.   A transfer device comprising the power supply device according to claim 1.   An image forming apparatus comprising the power supply device according to claim 1.   An image forming apparatus comprising the transfer device according to claim 10. A photosensitive drum;
A charging unit for charging the photosensitive drum;
An exposure unit for forming a latent image on the photosensitive drum charged by the charging unit;
A developing unit for developing the latent image formed by the exposure unit with toner and forming a toner image on the photosensitive drum;
A transfer unit for transferring the toner image formed on the photosensitive drum by the developing unit to a transfer target;
With
An image forming apparatus using the transfer device according to claim 10 as the transfer unit. To remove toner remaining on the image carrier from the image carrier during a cleaning period, and then transfer the toner image formed on the image carrier from the image carrier to a transfer body during a transfer period. A power supply control method for controlling a power supply that operates repeatedly,
The power supply device
A first power supply circuit for generating a cleaning bias for removing toner from the image carrier;
A second power supply circuit for generating a transfer bias for transferring a toner image from the image carrier to the transfer target;
With
The power supply device control method is as follows:
It has been detected that the period from when the second power supply circuit receives the instruction to generate the transfer bias until the transfer bias is started due to the oscillation of the second power supply circuit oscillating is prolonged. If so, the power supply device further comprises an oscillation control step for accelerating the start of oscillation of the oscillation unit by at least reducing a reverse current at an output terminal of the power supply unit that inhibits oscillation of the oscillation unit. Control method.   The power supply device control program for functioning a computer as a power supply device in any one of Claims 1 thru | or 9.

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