JP2015225125A - Image forming apparatus and method of controlling fuser of image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a normal power supply control over a fuser of an image forming apparatus is often impossible if a sudden fluctuation occurs to the frequency of an alternating-current power supply due to switchover of power stations or house-to-house power generators as a power source.SOLUTION: When it is determined that a frequency of an AC power supply is in a preset range, heating means for heating a heater of a fuser by carrying a current to the heater from the AC power supply is actuated to carry a current to the heater. On the other hand, when it is determined that the frequency is out of the preset range, current-carrying to the heater by the heating means is temporarily stopped. Furthermore, when the number of times of determining that the frequency is out of the preset range while stopping carrying a current to the heater is equal to or larger than a preset number of times, current-carrying to the heater is completely stopped. On the other hand, when the number of times of determining that the frequency is out of the preset range is smaller than the preset number of times, monitoring of the frequency of the AC power supply continues.

Description

  The present invention relates to an image forming apparatus and a fixing device control method thereof, and more particularly, to an image forming apparatus that forms a toner image on a recording medium in accordance with an electrophotographic method, and a fixing device control method provided in the image forming apparatus.

  In an image forming apparatus that transfers a toner image formed on an image carrier using an electrophotographic method onto a recording medium and then heat-fixes the toner image on the recording medium, the frequency of a commercial AC power source is measured, and the frequency In general, control is performed to supply power to the heat fixing device in synchronization with the heat fixing device. This is for the purpose of making the frequency of the commercial AC power supply correspond to two standards of 50 Hz and 60 Hz. Now, in order to further improve the safety of the device, in order to cope with the case where the commercial AC power supply fluctuates with respect to the standard frequency, the fluctuation is corrected, and power control is performed to further suppress the generation of flicker and harmonics. Yes.

  For example, Patent Document 1 and Patent Document 2 propose an image forming apparatus having the following configuration. That is, the frequency (zero cross point) is detected by detecting the timing when the voltage value of the commercial AC power supply crosses 0V, and when the frequency becomes high, that is, the cycle of detecting the zero cross point due to a voltage drop is short. Judge that it became. Then, in the power supply to the heat fixing device, control for correcting the frequency fluctuation and the voltage drop is performed. Further, when an instantaneous frequency variation, that is, an instantaneous zero cross point due to a pulse-like voltage drop is detected, it is determined as noise, and control is performed to continue power supply to the thermal fixing device at that time.

  On the other hand, Patent Document 3 proposes an image forming apparatus having the following configuration. In other words, the frequency of the commercial AC power supply is measured at the zero cross point immediately after the power supply to the device is turned on, but during the period when the frequency until the completion of the measurement is not determined, power is supplied to the heat fixing device using the temporary frequency. Control. After the frequency measurement is completed and the frequency is determined, the power supply to the heat fixing device is controlled using the measured frequency. Further, when the frequency of the commercial AC power source cannot be measured normally, the control of the power supply to the heat fixing device is continued using the temporary frequency.

  Also, if the frequency of the commercial AC power source exceeds a predetermined range, that is, if a frequency that is higher or lower than the range including the allowable error is detected with respect to 50 Hz / 60 Hz, it is determined as abnormal. Notify the user of the error (frequency error / zero cross error). In addition, it is common to control the operation of the image forming apparatus to stop.

JP 2013-097691 A JP 2011-237561 A Japanese Patent No. 4111893

  In recent years, changes in the power infrastructure environment have been seen, such as the separation of dispatched electricity from power suppliers and the spread of door-to-door power generation devices. However, in the above prior art, it is not considered that the frequency of the commercial AC power supply is suddenly changed by switching the power source supplied to the commercial AC power supply, that is, the power plant or the door-to-door power generation device. There is a concern that control of the apparatus cannot be continued normally. For example, when a sudden change in the frequency of a commercial AC power source due to switching of the power source occurs, frequency error detection using the conventional technology determines that the device has failed, but stops its operation, even though it is not a device failure. It may be done.

  Further, according to the techniques disclosed in Patent Document 1 and Patent Document 2, instantaneous frequency fluctuations are determined to be noise and control is performed so as to continue power supply to the thermal fixing device. If it changes greatly, power will be supplied with the AC waveform greatly distorted. For this reason, there is a possibility that normal power supply control cannot be performed due to harmonics.

  The present invention has been made in view of the above conventional example. Even when the frequency of the AC power supply fluctuates abruptly, it is possible to perform normal heat supply control and to appropriately heat fix a formed image. It is an object of the present invention to provide a control method for a forming apparatus and its fixing device.

  In order to achieve the above object, the image forming apparatus of the present invention has the following configuration.

  That is, an image forming apparatus that heats and fixes an image formed on a recording medium in accordance with an electrophotographic method by a fixing device, the heating means that heats the heater of the fixing device by an AC power source, and the frequency of the AC power source Measuring means for measuring the frequency, monitoring means for monitoring whether the frequency measured by the measuring means is within a predetermined range, and monitoring the monitoring means, the frequency is determined by the predetermined range. If it is determined that the frequency is outside the predetermined range, the heating means is operated to energize the heater, and if the frequency is determined to be outside the predetermined range, When the energization of the heater is temporarily stopped and the frequency is determined to be outside the predetermined range by monitoring by the monitoring means while the energization of the heater is stopped. When the number of times is equal to or greater than a predetermined number of times, image formation and monitoring by the monitoring unit are stopped, and the number of times that the frequency is determined to be outside the predetermined range is less than the predetermined number of times Comprises control means for controlling to continue monitoring by the monitoring means.

  According to another aspect of the present invention, there is provided a control method for a fixing device provided in an image forming apparatus for heating and fixing an image formed on a recording medium in accordance with an electrophotographic method, and supplying power to the image forming apparatus. A measurement step of measuring the frequency of the AC power supply, a monitoring step of monitoring whether the frequency measured in the measurement step is within a predetermined range, and the monitoring in the monitoring step, the frequency is When it is determined that the frequency is within a predetermined range, the AC power source operates a heating unit that energizes and heats the heater of the fixing device to energize the heater, and the frequency is within the predetermined range. If it is determined that the heater is outside, the energization of the heater by the heating means is temporarily stopped, and monitoring by the monitoring step is performed while the energization of the heater is stopped. When the number of times that the frequency is determined to be outside the predetermined range is greater than or equal to the predetermined number, image formation and monitoring by the monitoring process are stopped, and the frequency is determined in advance. And a control step of controlling to continue monitoring in the monitoring step when the number of times determined to be out of the range is less than a predetermined number of times.

  Therefore, according to the present invention, even when the frequency of the AC power supply fluctuates abruptly, for example, the influence of the generation of harmonics is suppressed, normal power supply control is performed, and the formed image is appropriately heat-fixed. There is an effect that can be.

1 is a side sectional view showing a schematic configuration of an image forming apparatus that is a typical embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic control configuration of the image forming apparatus illustrated in FIG. 1. It is a flowchart which shows the electric power supply control to a heat fixing device. It is a figure which shows the waveform of the alternating current power supply explaining the power supply control according to a prior art. It is a figure which shows the waveform of AC power supply explaining the electric power supply control according to the Example of this invention.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  In this specification, “recording” (sometimes referred to as “printing”) is not limited to the case of forming significant information such as characters and graphics, but may be significant. It also represents the case where an image, a pattern, a pattern, etc. are widely formed on a recording medium, or the medium is processed, regardless of whether it is manifested so that humans can perceive it visually. .

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  FIG. 1 is a side sectional view showing a schematic structure of an image forming apparatus for forming an image on a sheet-like recording medium according to an electrophotographic system which is a typical embodiment of the present invention.

  In this image forming apparatus, as shown in FIG. 1, a recording medium transport path 106 from the paper feed cassette 101 to the paper discharge tray 105 is formed inside the main body casing 100, and along the transport path 106, registration rollers 107 are formed. An image forming unit 108, a fixing device 109, and the like are arranged.

  The image forming unit 108 includes a photosensitive drum, a charger that uniformly charges the surface of the photosensitive drum, a developer that visualizes the electrostatic latent image formed on the surface of the photosensitive drum by scanning with light, and a toner image thereof. Is constituted by a transfer device or the like for transferring the image to a recording medium.

  The fixing device 109 includes a fixing film, a fixing heater, and a pressure roller. When the pressure roller is driven, the fixing film slides and rotates.

  In this image forming apparatus, in addition to the paper feed cassette 101, as an option, three paper feed cassettes 301 to 303 can be mounted. In these paper feed cassettes, a recording medium (for example, cut paper) having the same size as that set in the paper feed cassette 101 or a different size can be set.

  FIG. 2 is a block diagram showing a schematic control configuration of the image forming apparatus. FIG. 2 particularly shows a control configuration when power is supplied to the heater of the fixing device 109 in order to heat and fix the toner image by the fixing device 109.

  The image forming apparatus 1 includes a CPU 10, a ROM 11, a RAM 12, a heater 13, a temperature sensor 14, and a zero cross detection unit 15. The heater 13 is included in the fixing device 109 and is used to heat and fix the recording medium on which the toner image is transferred by the image forming unit 108. The temperature sensor 14 detects the temperature of the heater 13. Further, the zero cross detection unit 15 detects a timing (zero cross point) at which the AC power supplied from the external commercial alternating current (AC) power supply 2 crosses 0V.

  The CPU 10 controls the operation of the entire image forming apparatus by executing a control program stored in the ROM 11 using the RAM 12 as a work area and a temporary data storage area. In addition, a firmware program 20 for executing control for supplying power to the heater 13 of the fixing device 109 is written in the ROM 11 and is read and executed by the CPU 10.

  The firmware program 20 includes a temperature control unit 200 that controls the power supply amount to the heater 13 based on the control target temperature of the heater 13 and the temperature of the heater 13 detected by the temperature sensor 14. Further, the frequency of the AC power source 2 is calculated from the power control unit 201 that controls power supply to the heater 13 based on the power supply amount determined by the temperature control unit 200 and the zero cross point detected by the zero cross detection unit 15 and the detection time. And a frequency measuring unit 202 for measuring the frequency.

  Using such a configuration, each part of the image forming apparatus 1 is controlled as follows during the image forming operation.

  When an image forming operation is started by an instruction from an operation unit UI (not shown) or a host device (not shown) connected to the image forming apparatus 1, the CPU 10 detects the temperature control unit 200, the power control unit 201, and the heater 13. The temperature control and drive control of the fixing device 109 are executed using the temperature.

  Next, operations of the frequency measurement unit 202 and the power control unit 201 after the start of the image forming operation by the image forming apparatus will be described.

  FIG. 3 is a flowchart showing the frequency detection and power control processing of a commercial alternating current (AC) power supply.

  When a print job is received and a printing operation is started, in step S401, the power control unit 201 turns on a relay circuit included in the fixing device 109. When the relay circuit is turned on, the electric power from the commercial alternating current (AC) power source 2 is supplied to the fixing device 109, and the zero cross detection unit 15 monitors the voltage of the AC power source and detects the zero cross point. When the zero cross point is detected, the zero cross detection unit 15 interrupts the CPU 10.

  In step S402, the CPU 10 checks whether there is an interrupt. If the CPU 10 does not detect an interrupt, the process proceeds to step S412 to check whether the elapsed time (Tlapse1) from when the relay circuit is turned on is 500 milliseconds or more. Here, if Tlapse ≧ 500 milliseconds, the process proceeds to step S418, and if Tlapse <500 milliseconds, the process returns to step S402. In this way, after the relay circuit is turned on, the CPU 10 can wait for an interrupt from the zero cross detection unit 15 for a predetermined time of 500 milliseconds. If an interrupt is detected during that time, the process proceeds to step S403. When a zero-cross interrupt is detected within a predetermined time, the zero-cross cycle is equivalent to the frequency of the commercial alternating current (AC) power supply 2, and in actual control, the power supply control is performed using the zero-cross cycle without converting to the frequency. Do.

  In step S403, the frequency measurement unit 202 starts measuring the zero-cross interrupt period, and in step S404, monitors whether there is an interrupt from the zero-cross detection unit 15. Here, if the CPU 10 does not detect an interrupt, the process proceeds to step S413 to monitor whether the elapsed time (Tlapse2) from the start of the previous measurement has reached 12.5 milliseconds or more. Here, if Tlapse ≧ 12.5 milliseconds, the process proceeds to step S414, and if Tlapse <12.5 milliseconds, the process returns to step S404. In this way, it is possible to wait for an interrupt from the zero-crossing detection unit 15 for an elapsed time from the start of the previous measurement for another predetermined time of 12.5 milliseconds. If an interrupt is detected during that time, the process proceeds to step S405.

  In step S <b> 405, the CPU 10 causes the frequency measurement unit 202 to measure from the interrupt time measured last time to the interrupt time measured this time using a timer, and stores the measurement time (TP) in the temporary storage area of the RAM 12. In step S406, it is checked whether the stored measurement time (TP) is 6.9 milliseconds or more, which is another predetermined time. Here, if TP ≧ 6.9 milliseconds, the process proceeds to step S407, and if TP <6.9 milliseconds, the process proceeds to step S414. In step S407, it is checked whether the stored measurement time (TP) is 12.5 milliseconds or more. Here, if TP ≧ 12.5 milliseconds, the process proceeds to step S408, and if TP <12.5 milliseconds, the process proceeds to step S414.

  Here, the predetermined time (threshold value) for comparing the measurement time of the frequency of the AC power source will be described. Usually, the frequency of a commercial AC power supply has a standard of 50 Hz / 60 Hz. On the other hand, even if the frequency of the AC power supply fluctuates to some extent, the image forming apparatus 1 can execute the image forming operation normally if the fluctuation is within an allowable range. Here, the allowable range is set to ± 20% with respect to the standard frequency. That is, when the frequency of the AC power supply is 50 Hz, the allowable range is 40 Hz to 60 Hz, and when 60 Hz, the allowable range is 48 Hz to 72 Hz. Therefore, when 50 Hz / 60 Hz is assumed as the standard frequency, the minimum frequency in the allowable range is 40 Hz, and the maximum frequency is 72 Hz. Therefore, when the AC power supply has the minimum frequency, the zero cross period is 12.5 milliseconds, and when the AC power source has the maximum frequency, the zero cross period is 6.9 milliseconds. Therefore, these two values are used as threshold values in steps S406, S407, and S413.

  Returning to FIG. 3 and continuing the description, it can be determined that the frequency of the AC power source is stable when the measurement period of the zero cross interrupt is within a predetermined range. Therefore, in step S <b> 408, the CPU 10 calculates the output duty (Duty) to the heater 13 by the temperature control unit 200 and the power control unit 201. Next, in step S409, power is supplied to the heater 13 with the calculated duty (energization). Further, in step S410, the CPU 10 energizes the heater 13 by the temperature control unit 200 and the power control unit 201, and then resets the zero-cross interrupt measurement cycle NG count counter (CNT) to “0”.

  Thereafter, in step S411, it is checked whether or not the printing operation by the print job still continues. If it continues, the process returns to step 404. If not, the process ends.

  If the frequency fluctuation of the AC power supply is large and the zero-cross interrupt measurement period exceeds the predetermined range, the process proceeds to step S414 as described above. In step S414, energization of the heater 13 is temporarily stopped. In step S415, the zero cross interrupt measurement cycle NG count counter (CNT) is incremented by 1, and the number of cycles NG is counted. In step S416, the zero cross interrupt cycle is counted. Resume measurement. In step S417, it is checked whether the count value of the zero cross interrupt measurement cycle NG count counter (CNT) is 4 or more. If CNT ≧ 4 (predetermined number of times or more), the process proceeds to step S418. If CNT <4, the process returns to step S404 to continue monitoring the zero-cross interrupt measurement period. Therefore, if the value of the zero cross interrupt measurement cycle NG counter (CNT) is less than a predetermined number, the energization of the heater 13 is resumed when the measurement cycle of the next zero cross interrupt returns to the predetermined range again. .

  If a zero-cross interrupt cannot be detected within 500 milliseconds after the relay circuit is turned on, or if the number of cycles NG exceeds a predetermined number, the process proceeds to step S418, where the AC power supply 2 or the power supply circuit of the image forming apparatus is used. It is determined that an abnormality has occurred in the part. Then, a zero cross error is notified to the host device, and a message to that effect is displayed on the display unit of the operation panel of the image forming apparatus. Further, in step S419, the relay circuit is turned off, and then the process is terminated.

  Here, the power supply control according to the frequency fluctuation of the AC power supply according to this embodiment will be described in comparison with the conventional method.

  FIG. 4 is a diagram showing an AC power waveform when power is supplied to the heater by power control according to a conventional example.

  In the example shown in FIG. 4, it can be seen that there is a phase shift in the waveform of the AC power supply. In the portion where the phase shift surrounded by ◯ in FIG. 4 occurs, the above-described zero cross cycle becomes extremely long or short. However, in the power supply control according to the conventional example, even if the frequency is abnormal, the heater is energized unless these are within the allowable range and a zero cross error occurs. For this reason, it becomes a distorted energization phase and a harmonic component will become high.

  FIG. 5 is a diagram showing an AC power waveform when power is supplied to the heater by power supply control according to this embodiment.

  In the example shown in FIG. 5, when an abnormal frequency is detected, energization to the heater is immediately stopped, and energization is resumed when the normal frequency is restored. For this reason, the time for supplying power with a distorted phase is minimized. In addition, when the power source is switched from commercial power supply from a power company to power from a door-to-door power generation device such as sunlight, the frequency of the AC power supply fluctuates. is there. Further, if the number of cycles NG is equal to or less than the predetermined number, the image forming apparatus does not stop.

  Therefore, according to the embodiment described above, even if the frequency of the AC power supply suddenly changes greatly, the energization to the heater is once stopped immediately, and after that, when the frequency returns to the normal range, the heater is turned on. Can be energized again. In addition, switching of the power source of the AC power source (power company's power plant or door-to-door power generator) occurs, and even if the frequency of the AC power source changes, it is determined as an error and the operation of the entire image forming apparatus is stopped. Therefore, the operation of the apparatus can be continued normally.

  Furthermore, since the time for supplying power to the heater at an abnormal frequency can be minimized, it is possible to suppress the influence on the power supply control by the harmonic component.

  In the embodiment described above, power supply to the heater is performed by so-called half-wave control (zero cross control) based on a half cycle of the frequency of the alternating current, but the present invention is limited thereto. is not. For example, it goes without saying that the same effect can be obtained even by so-called phase control in which control is performed by changing the energization phase angle starting from the zero cross point.

1 image forming apparatus, 2 commercial AC power supply, 10 CPU, 11 ROM, 12 RAM,
13 fixing device, 14 temperature sensor, 15 zero cross detection unit,
20 Firmware program, 100 Main body casing, 101 Paper feed cassette,
105 paper discharge tray, 106 transport path, 107 registration roller, 108 image forming unit,
200 temperature control unit, 201 power control unit, 202 frequency measurement unit,
301 to 303 Paper cassette (optional)

Claims (10)

An image forming apparatus that heat-fixes an image formed on a recording medium according to an electrophotographic method using a fixing device,
Heating means for energizing and heating the heater of the fixing device by an AC power source;
Measuring means for measuring the frequency of the AC power source;
Monitoring means for monitoring whether the frequency measured by the measuring means is within a predetermined range;
When the monitoring means determines that the frequency is within the predetermined range, the heating means is operated to energize the heater, and the frequency is outside the predetermined range. If it is determined that there is a current, the energization of the heater by the heating unit is temporarily stopped, and the frequency is within the predetermined range by monitoring by the monitoring unit while the energization of the heater is stopped. When the number of times determined to be outside is equal to or greater than a predetermined number of times, image formation and monitoring by the monitoring unit are stopped, and the number of times the frequency is determined to be outside the predetermined range is determined. An image forming apparatus comprising: a control unit that controls to continue monitoring by the monitoring unit when the number of times is less than a predetermined number.   The control means is a case where the number of times that the frequency is determined to be outside the predetermined range by monitoring by the monitoring means is less than a predetermined number of times, and the frequency by the monitoring by the monitoring means 2 is controlled to resume energization of the heater by the heating means temporarily stopped when it is determined that the temperature has returned to the predetermined range again. Image forming apparatus. The control means includes
Counting means for temporarily stopping energization of the heater, and counting the number of times that the frequency is determined to be outside the predetermined range by monitoring by the monitoring means during energization stop;
First comparison means for comparing the number of times counted by the counting means with a predetermined threshold;
The image forming apparatus according to claim 2, further comprising: a reset unit that resets a count value by the counting unit when the energization of the heater by the temporarily stopped heating unit is resumed. . The monitoring means includes
Second comparison means for comparing the frequency measured by the measurement means with a predetermined maximum frequency;
4. The image forming apparatus according to claim 1, further comprising: a third comparison unit that compares a frequency measured by the measurement unit with a predetermined minimum frequency. 5.   The image forming apparatus according to claim 4, wherein the maximum frequency and the minimum frequency are determined based on an allowable range in which the image forming apparatus can normally execute an image forming operation.   The measurement means measures the time of a point at which the voltage of the AC power supply becomes zero, and measures the frequency based on a period obtained from the time of the previous measurement and the time of the current measurement. The image forming apparatus according to any one of 1 to 5.   When the energization of the heater is stopped more than a predetermined number of times and the energization of the heater by the heating unit is stopped, there is an abnormality in the AC power supply or the power supply circuit of the image forming apparatus. The image forming apparatus according to claim 1, further comprising a notifying unit that notifies that the occurrence has occurred.   The image forming apparatus according to claim 1, wherein the AC power source includes a commercial power source and a door-to-door power generator. It further has a detecting means for detecting the temperature of the heater,
The image forming apparatus according to claim 1, wherein the control unit further controls energization of the heater based on the temperature of the heater detected by the detection unit. . A control method of a fixing device provided in an image forming apparatus for heating and fixing an image formed on a recording medium according to an electrophotographic method,
A measuring step of measuring a frequency of an AC power source that supplies power of the image forming apparatus;
A monitoring step of monitoring whether the frequency measured in the measurement step is within a predetermined range;
When it is determined by the monitoring in the monitoring step that the frequency is within the predetermined range, the heater is energized by operating a heating means for energizing and heating the heater of the fixing device by the AC power source. If it is determined that the frequency is outside the predetermined range, the energization of the heater by the heating means is temporarily stopped, and the monitoring is performed while the energization of the heater is stopped. When the number of times that the frequency is determined to be outside the predetermined range by monitoring by the process is equal to or greater than the predetermined number, image formation and monitoring by the monitoring process are stopped, and the frequency is And a control process for controlling to continue monitoring in the monitoring process when the number of times determined to be outside the predetermined range is less than a predetermined number of times. The method according to claim.

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