JP4533789B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that detects a drop in power supply voltage and controls operation.

  In an image forming apparatus using an electrophotographic system, a fixing device for fixing toner consumes a large amount of power, so that a large current flows through a power cable, which may cause a voltage drop. For example, when the image forming apparatus performs continuous printing, the heat of the surface of the fixing roller provided in the fixing device for fixing the toner to the paper is rapidly taken away by the toner and the paper. As a result, the surface temperature of the fixing roller is lowered. To compensate for this, the fixing device energizes a heat source provided in the fixing device, for example, a heater lamp of about 1200 W. As a result, for example, in the case of an AC power supply with a rated voltage of 100 V, a current of about 12 amperes flows through the power cable connecting the image forming apparatus to the outlet. Therefore, a corresponding voltage drop occurs until the power input unit of the image forming apparatus is reached due to the impedance of the power cable.

In setting the reference value, the rated voltage is considered to have a margin for fluctuations in the power supply voltage. That is, the margin is set to a value such that the power supply voltage does not fall below the reference value due to a power supply voltage fluctuation assumed under normal use conditions or a voltage drop due to the impedance of the power supply cable. If the power supply voltage is equal to or higher than the reference value, the image forming apparatus is designed to operate normally. However, if the power supply situation is very bad, the power supply voltage may fall below the reference value. Therefore, in order to avoid the runaway of the microcomputer that controls the operation of the device due to a drop in the power supply voltage, it is detected that the voltage at the power input section has dropped below the reference value and the power supply voltage drop countermeasure process There is one that performs a process of returning to the initial state after performing (for example, Patent Document 1).
When a voltage drop is detected during printing, the image forming apparatus immediately suspends the printing operation, and when returning to the initial state, the paper being printed stays in the apparatus and jams. In fact, in many cases, a voltage drop is detected during printing. This is because the rate at which heat is supplied to the fixing device is high during warm-up or printing.
JP-A-6-35562

  Image forming apparatuses such as copying machines, printers, and multi-function machines are often used even in environments where AC power supply voltage is unstable, such as in developing countries. Often, a drop in the power supply voltage is detected and the printing operation of the image forming apparatus is interrupted, and after the power supply voltage is restored, a paper jam that has been transported through the apparatus is detected. In order to resume the printing process, it is necessary for the user to remove the paper in the machine causing the paper jam and start the printing process from the beginning. In addition, even during a printing operation, if various settings are made on the operation panel of the image forming apparatus for copying, for example, and a voltage drop occurs during warm-up until the copying can be started, the set contents are initialized. It will be converted. This is because when the image forming apparatus main body detects a voltage drop, the same processing as when the power is turned off is performed.

  There is a demand for an apparatus capable of continuing a printing operation or a warm-up operation without interrupting and initializing the operation of the image forming apparatus when a voltage drop at the power input unit is detected.

  According to the present invention, an image forming unit that performs an operation relating to image formation in either the first operation mode or the second operation mode, and a normal power supply voltage supplied from outside is higher than a predetermined threshold voltage. A power supply voltage detection unit that detects whether the operating voltage is a voltage drop state that is equal to or lower than a threshold value, and when a voltage drop state is detected during operation in the first operation mode, the first operation mode is set to be higher than that mode. An image forming apparatus comprising: an image forming control unit that switches to a second operation mode that reduces an external power supply current.

  Here, the image forming apparatus is an apparatus that receives image data and prints it on a recording medium. For example, the image forming apparatus includes a printer, a copier, a facsimile, or a complex machine that combines them. The operation related to image formation does not simply indicate an operation during the printing process, but includes, for example, an initialization operation after turning on the power, an operation during warm-up, and a preparation operation necessary for image formation. Also includes post-processing operations after printing. The power supply current and the power supply voltage may refer to the effective value of the current or voltage, but are not limited to the actual value, for example, an instantaneous maximum value or other index having a correlation with the effective value. Also good. The index may be selected as appropriate by the apparatus designer in accordance with the characteristics of the apparatus. The operation mode refers to various modes in which the control of each unit is different when the image forming apparatus executes processing related to image formation. For example, when printing the same print data on the same paper, the printing operations under the control of different feeding intervals of the front and back paper are different operation modes. Further, it is a different operation mode to control a portion of the image forming apparatus that consumes a large amount of power, for example, power supplied to the fixing device in the electrophotographic apparatus to different power.

  In the image forming apparatus according to the present invention, when a voltage drop state is detected during operation in the first operation mode, the first operation mode is set to the second operation in which the power supply current from the outside is reduced as compared with the mode. Since the image forming control unit that switches to the mode is provided, when the power supply voltage detection unit detects a voltage drop state, the operation can be switched to the second operation mode to reduce the power supply current and continue the operation. Therefore, the printing process is interrupted by detecting a voltage drop state during the printing operation, and does not require complicated work such as causing the user to remove the jammed paper or restart the printing process from the beginning. . Alternatively, since the voltage drop state is detected during the warm-up and the operation panel settings are initialized, the user is not requested to perform the operation panel setting again after returning. This is very convenient for those who use the image forming apparatus under conditions with poor power supply conditions.

    An image formation interrupting unit that interrupts an operation related to image formation may be further provided when a power supply voltage detection unit detects a voltage drop state after a first predetermined period from switching to the second operation mode. In this way, when the voltage drop due to the impedance of the power supply cable is suppressed by reducing the power supply current of the image forming apparatus and becomes a normal voltage, the operation is continued in the second operation mode. If the state cannot be resolved in this operation mode, the operation in a state where the normal operation of the apparatus cannot be guaranteed can be interrupted to ensure safety.

  Further, the image formation control unit sets the second operation mode to the first operation mode when the normal operation voltage is detected by the power supply voltage detection unit after the second predetermined period from the switching to the second operation mode. You may make it switch further. In this way, when the power supply situation has recovered after a predetermined period has elapsed since switching to the second operation mode, the operation is automatically restored to the original operation mode and the operation is continued.

  The image forming control unit further includes a power supply history storage unit that stores a power supply history that is a history of power supply voltage detection by the power supply voltage detection unit, and the image formation control unit performs an operation when the power supply history satisfies a predetermined condition. You may make it switch to a 2nd operation mode. In this way, it is possible to switch the appropriate operation mode based on the past history as well as the state of the power supply voltage at that time.

  Further, the image formation control unit may detect a power supply history during a subsequent periodic period when a voltage drop state is detected a predetermined number of times or more during each control period obtained by dividing the periodic period into a plurality of control periods. During the control period, the operation may be switched to the second operation mode. In this way, when the power supply has a periodic regularity, the operation mode can be switched according to the regularity based on the past history.

  The image forming unit may be an electrophotographic image forming unit, and the second operation mode may be a mode in which less power is supplied to the fixing device than in the first operation mode. In this way, in the electrophotographic image forming apparatus, the power supply current can be effectively suppressed by controlling the power of the fixing unit that consumes a large amount of power.

  Further, the second operation mode may be a mode in which a printing processing speed is slower than that of the first operation mode. In this way, the image forming operation can be continued while maintaining the fixing property and the image quality by reducing the printing processing speed by an amount corresponding to the suppression of the power supply current.

Further, the image forming unit is an electrophotographic image forming unit, and the first operation mode and the second operation mode have the same process speed when forming an image, and have different sheet feeding intervals. May be. In this way, since the printing processing speed is changed while maintaining the process speed of the electrophotographic image forming unit, the operation mode switching control can be easily performed as compared with the case where the process speed is changed.
Here, the process speed refers to the speed at which the surface of a photoreceptor on which an image is formed in an electrophotographic system moves between each station of charging, exposure, development, and transfer.

  The image forming control unit may further include a display unit that displays that the switching between the first operation mode and the second operation mode is performed. In this way, the user is informed that the operation mode has been switched. For example, when the printing processing speed changes as the operation mode is switched, the user is informed of the current operation state. Can be given.

Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings.
<Mechanical configuration of image forming apparatus>
FIG. 2 is an explanatory diagram showing an example of a mechanical configuration of the image forming apparatus according to the present invention. In FIG. 2, the image forming apparatus 71 records and outputs an image read by the image reading apparatus and data from a device (for example, an image processing apparatus such as a personal computer) connected to the image forming apparatus 71 from the outside. This is an electrophotographic printer.

  In the image forming apparatus 71, each process unit responsible for each function of the image forming process is arranged around the photosensitive drum 202, and an image forming unit is formed by these. Around the photosensitive drum 202, a charging unit 203, a developing unit 200 as a developing unit, a transfer roller 207, a cleaning unit 208, an optical scanning unit 204, and the like are arranged in this order.

  The charging unit 203 uniformly charges the surface of the photosensitive drum 202. The optical scanning unit 204 scans an optical image on the uniformly charged photosensitive drum 202 and writes an electrostatic latent image. The developing unit 200 visualizes the electrostatic latent image written by the optical scanning unit 204 with a developer supplied from the developing unit 200. Further, the developing unit 200 is provided with a toner container 72 for supplying toner to the unit. The transfer roller 207 functions as a transfer unit that transfers an image visualized on the photosensitive drum 202 onto a sheet of recording material and forms a visible image on the sheet. The cleaning unit 208 removes the developer remaining on the photosensitive drum 202 and makes it possible to record a new image on the photosensitive drum 202.

  Below the image forming apparatus 71, a supply tray 201 that is housed in the main body of the image forming apparatus 71 is disposed. The supply tray 201 is a recording material storage tray that stores recording material (paper). The paper stored in the supply tray 201 is separated one by one at a predetermined time interval by a pickup roller 209 and the like, conveyed to the registration roller 210, and synchronized with the image formed on the photosensitive drum 202 by the registration roller 210. Is peeled off and supplied sequentially between the transfer roller 207 and the photosensitive drum 202. The image recorded and reproduced on the photosensitive drum 202 is transferred onto the sheet by the action of electrostatic force acting on the toner charged by the transfer voltage applied to the transfer roller 207. The supply of paper to the supply tray 201 is performed by pulling out the supply tray 201 to the front side (operation side) of the image forming apparatus 71.

In FIG. 2, three sheets S1, S2, and S3 are conveyed at predetermined intervals in the image forming apparatus 71. The paper transport timing is controlled by a control board 30 described later.
A fixing device 205 is disposed in the upper part of the image forming apparatus 71. The fixing device 205 sequentially receives the paper on which the image has been transferred, and fixes the developed image transferred on the paper by heat and pressure by the fixing roller 211, the pressure roller 212, and the like.

  The sheet on which the image is recorded is further conveyed upward. Then, it is discharged to a stacking tray 70 provided on the exterior of the image forming apparatus 71. When double-sided image formation or post-processing is designated, the paper is discharged toward the stacking tray 70, but the reverse roller 213 is reversed with the reverse edge of the paper held between the reverse rollers 213. Then, the paper is reversed and conveyed in the reverse direction, that is, in the direction of the conveyance path provided for double-sided image formation and post-processing.

  The control board 30 is a circuit board for controlling the operation of each part related to the image formation described above. An input / output circuit for inputting a signal from each sensor and outputting a signal for addition to the control board 30, a communication circuit for exchanging with a host computer (not shown), and controlling each input signal and communication A microcomputer 11, a ROM that stores a procedure of processing executed by the microcomputer 11, a RAM that provides a work area for the microcomputer to process images and data, and a nonvolatile memory element that holds data are mounted. .

  The control for detecting the power supply voltage and switching the operation mode is realized mainly by the microcomputer 11 of the control board 30 in FIG. 2 and a control program stored in a ROM (not shown). That is, the function of the image forming unit that controls the operation related to image formation and switches between the first and second operation modes and the function of the power supply voltage detection unit that detects whether the power supply voltage is a normal operating voltage or a voltage drop state are the microcomputer 11. Is realized by executing processing according to the control program and performing control based on the state of each input signal.

<Control block configuration>
FIG. 3 is a block diagram illustrating an example of a circuit block configuration relating to control in which the image forming apparatus 71 detects the power supply voltage and switches the operation mode. In FIG. 3, the AC power supply voltage from the AC power supply input terminal 1 is input to the DC power supply unit 7, and the DC power supply voltage for operating the circuit is supplied from the DC power supply to the control board 30 and other circuits. The AC input monitor unit 9 in the DC power supply unit 7 provides the control board 30 with a signal indicating the presence or absence of AC input.

  The power SW state monitor unit detects the ON / OFF state of the power switch of the image forming apparatus 71 and provides it to the control board 30. The power switch is a switch (not shown) provided on the exterior portion of the image forming apparatus 71 so that the user of the image forming apparatus 71 turns on / off the power of the image forming apparatus 71. The power switch does not cut off the AC voltage supplied to the image forming apparatus 71 in a circuit but is a switch for providing the control board 30 with an on / off state. The microcomputer 11 functions as a power supply voltage detection unit, an image formation control unit, and an image formation interruption unit by executing a program stored in advance in a ROM (not shown) of the control board 30. That is, when the microcomputer 11 detects that the power switch is turned off, the microcomputer 11 stops the operation of each part of the image forming apparatus, cuts off the power supply to the part that does not operate with respect to the DC power supply UN7, and shifts to the shutdown mode. To control. However, the microcomputer 11 operates even during the shutdown mode, and the power SW state monitor unit 3 is configured to detect the state of the power switch. When the power switch is turned on by the user, the on-state is detected, the image forming apparatus is shifted to the power-on mode, and DC power is supplied to each unit so that the image forming apparatus 71 is initialized. To control.

The AC input voltage monitor unit 5 detects whether the AC power supply voltage is a normal operating voltage higher than a predetermined threshold voltage or a voltage drop state below the threshold, and outputs a signal indicating whether the AC power supply voltage is a normal voltage or a voltage drop state. To provide.
The fixing power control circuit 15 is a circuit for controlling the power supplied to the fixing device 205 in accordance with the control of the microcomputer 11. A fixing heater lamp 17 is provided inside the fixing roller 211 of the fixing device 205 to overheat the fixing roller 211 and keep the surface of the roller at a predetermined temperature. The fixing power control circuit 15 includes a fixing heater lamp 15. The phase of the AC voltage supplied to 17 is controlled to control the power supplied when energized, and when the surface of the fixing roller 211 reaches a predetermined temperature or higher, the AC voltage supply to the fixing heater lamp 17 is cut off to fix the fixing roller 211. The surface of 211 is controlled to be a predetermined temperature.

  Further, the control board 30 may include a power supply state history storage circuit 13 that stores the history of the AC input voltage provided from the AC input voltage monitor unit 5. The power supply state history storage circuit 13 is realized by a non-illustrated nonvolatile memory element mounted on the control board 30 and functions as a power supply history storage unit.

<Operation mode switching control>
FIG. 1 is a time chart showing how the image forming apparatus of the present invention detects an AC input voltage and switches the operation mode based on the state of the detected AC input voltage. The power switch is turned on by the user at time T01 shown in FIG. The power SW state monitoring unit 3 provides a signal indicating that the power switch is turned on to the control board 30, and the microcomputer 11 shuts down the operation state of the image forming apparatus 71 in response to the power switch being turned on. Switch from off mode, perform initialization and warm up. During the warm-up at time T01 and thereafter, the AC input voltage monitor unit 3 detects that the power supply voltage state is the normal voltage, so the microcomputer 11 performs the initialization operation in the first operation mode corresponding to the normal voltage. And warm up. The microcomputer 11 performs phase control by the fixing power control circuit 15 so as to supply the fixing heater lamp 17 with the maximum power W ₁ corresponding to the first operation mode. That is, the fixing heater lamp 17 is on / off controlled so that the surface of the fixing roller 211 reaches a predetermined temperature, but the power W ₁ is supplied when it is on.

Next, when the AC power supply voltage drops during warm-up or printing and the AC input voltage becomes lower than the threshold value at time T02, the AC input voltage monitor unit 5 detects the voltage drop state. When the voltage drop state continues for a predetermined time period t1, the microcomputer 11 switches the operation of the image forming apparatus 71 from the first operation mode to the second operation mode at time T03 after the elapse of the period t1. The delay of t1 is for ignoring instantaneous power failure or instantaneous voltage drop. In the second operation mode, the microcomputer 11 performs phase control by the fixing power control circuit 15 so as to supply electric power W ₂ smaller than W ₁ when the fixing heater lamp 17 is turned on. Further, the microcomputer 11 switches the paper feeding time interval during printing between the first operation mode and the second operation mode, and makes the paper feeding interval in the second operation mode wider than the paper feeding interval in the first operation mode. Good. As a result, the amount of heat taken by the sheet passing through the fixing roller 211 within a certain period can be reduced, and a balance with the amount of power supplied to the fixing heater lamp 17 can be achieved.

  At time T04 after the elapse of a predetermined period t2 after switching the operation mode at time T03, the microcomputer 11 again determines the power supply voltage state. If the voltage drop state is also present at time T04, normal operation cannot be guaranteed, so the processing of the image forming apparatus 71 is interrupted and switched to the shut-off mode. In FIG. 1, waveforms B, D, and F indicated by two-dot chain lines indicate this state. At the time of switching to the shut-off mode, the microcomputer 11 performs a backup data saving process such as a counter. If there is a sheet being conveyed inside the image forming apparatus 71 during printing, the microcomputer 11 takes the sheet out of the machine. Since the operation is stopped without waiting for the paper to be discharged, the paper remains in the machine. Also, it is not guaranteed to save the print data during printing. In order to resume printing, the paper remaining in the machine must be removed by the user.

On the other hand, when the power supply voltage state has returned to the normal operating voltage at time T04, the microcomputer 11 continues the operation in the second operation mode without interrupting the operation of the image forming apparatus 71.
The microcomputer 11 switches the second operation mode to the first operation mode at time T05 after a predetermined period t3 has elapsed since the operation mode was switched at time T03. In FIG. 1, waveforms A, C, and E indicated by solid lines indicate this state. Thereafter, if the power supply voltage state is a normal operating voltage, the first operation mode is continued. If a voltage drop state is detected after switching to the first operation mode, the processing after time T02 is performed.

  Note that when the switching from the first operation mode to the second operation mode is performed, or vice versa, when the switching from the second operation mode to the first operation mode is performed, this is indicated in the illustration of the image forming apparatus 71. It may be displayed on the display unit of the operation panel to notify the user. In particular, when the paper feed interval is changed between the first operation mode and the second operation mode, the printing process speed is changed regardless of the user's will, so that it is possible to give the user a sense of security by notifying the switching of the operation mode. it can.

<Control based on power supply history>
In this embodiment, the microcomputer 11 provided on the control board 30 has a calendar function for measuring the date and time. When the AC input monitor unit 5 detects a decrease in the AC power supply voltage, the microcomputer 11 provided on the control board 11 stores the date and time information when the power supply voltage has decreased in the power supply state history storage circuit 13. The table shown below is shown in tabular form for easy understanding of an example of the contents stored in the power supply state history storage circuit 13. As shown in Table 1, the power supply state history storage circuit 13 stores the date, day of the week, and time of the period when the AC input voltage monitoring unit 5 detects the voltage drop state. That is, the power supply state history storage circuit 13 stores that a voltage drop state was detected during the period from 8:00 to 9:59 on Friday, January 7. Furthermore, it is stored that a voltage drop state was detected during the period from 16:40 to 17:59 on Monday, January 11. In addition, the period in which the voltage drop state is detected on Friday, January 14, Friday of January 21, and Friday of January 28 is also stored together with each day and day of the week.

  The microcomputer 11 determines a period in which the voltage drop state is frequently detected based on the power supply state history storage content stored in the power supply state history storage circuit 13. For example, it is determined from the date column that the probability that a power supply voltage drop state is detected every Friday is high, and it is further determined that the occurrence frequency of the power supply voltage drop is high between 8 am and 10 am on Friday. The determination that the occurrence frequency is high may be, for example, a day of the week when the voltage drop state is detected a predetermined number of times or more during a predetermined number of days as a high frequency day. Based on the determination, the microcomputer 11 switches the first operation mode to the second operation mode from 8 am to 10 am on Friday to operate the image forming apparatus 71 while suppressing power supply to the fixing device. As a result, during the period when the voltage drop state is detected frequently, that is, during the period when the power supply situation is bad and the probability that the power supply voltage drops is high, the image forming apparatus is operated in the second operation mode in which the power supply current is suppressed. The image forming apparatus can be operated in a state where the state is difficult to detect.

4 is a time chart showing how the image forming apparatus of the present invention detects an AC input voltage and switches the operation mode based on the state of the detected AC input voltage. It is explanatory drawing which shows an example of the mechanical structure of the image forming apparatus of this invention. FIG. 3 is a block diagram illustrating an example of a configuration of each circuit block relating to control in which the image forming apparatus detects a power supply voltage and switches an operation mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power input terminal 3 Power supply SW state monitor part 5 AC input voltage monitor part 7 DC power supply unit 9 AC input monitor part 11 Microcomputer 13 Power supply state history storage circuit 15 Fixing power control circuit 17 Fixing heater lamp 30 Control board 50 Toner supply Paths 53, 79 Toner bottle positioning unit 54 Toner bottle 60 Developing roller 70 Loading tray 71 Image forming device 72 Toner storage unit 200 Developing tank, developing unit 201 Supply tray 202 Photosensitive drum 203 Charging means 204 Optical scanning unit 205 Fixing device 207 Transfer Roller 208 Cleaning unit 209 Pickup roller 210 Registration roller 211 Fixing roller 212 Pressure roller 213 Reverse roller

Claims (8)

An image forming unit that performs an operation related to image formation in either the first operation mode or the second operation mode;
A power supply voltage detector for detecting whether the power supply voltage supplied from the outside is a normal operating voltage higher than a predetermined threshold voltage or a voltage drop state below a threshold;
An image formation control unit that switches the first operation mode to a second operation mode in which a power supply current from outside is smaller than that mode when a voltage drop state is detected during operation in the first operation mode; ,
A power supply history storage unit that stores the date, day of week, and time when the power supply voltage has dropped as a power supply history ,
The image formation control unit determines a period in which a voltage drop state is frequently detected based on the power history, and the same month, day, day of the week, and / or time as the period are imaged in the second operation mode. An image forming apparatus controlled to perform formation.   2. The image forming interrupting unit according to claim 1, further comprising an image forming interrupting unit that interrupts an operation related to image formation when a power supply voltage detecting unit detects a voltage drop state after a first predetermined period from switching to the second operation mode. Image forming apparatus.   The image formation control unit further switches the second operation mode to the first operation mode when a normal operation voltage is detected by the power supply voltage detection unit after a second predetermined period from switching to the second operation mode. The image forming apparatus according to claim 1 to be switched. The image forming apparatus according to claim 1, wherein the image forming control unit switches the operation to a predetermined first or second operation mode when a power history satisfies a predetermined condition.   The image forming apparatus according to claim 1, wherein the image forming unit is an electrophotographic image forming unit, and the second operation mode is a mode in which power supply to the fixing device is less than that in the first operation mode. .   The image forming apparatus according to claim 1, wherein the second operation mode is a mode in which a printing processing speed is slower than that of the first operation mode. The image forming unit includes an electrophotographic image forming unit, and the first operation mode and the second operation mode have the same process speed when forming an image, and have different sheet feeding intervals. 6. The image forming apparatus according to 6 .   The image forming apparatus according to claim 1, further comprising a display unit that displays that the image forming control unit has switched between the first operation mode and the second operation mode.

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