JP2009048090A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which hardly causes flickering of a fluorescent lamp, even if controlling partial supply of power to be supplied to a fixing heater. <P>SOLUTION: The image forming apparatus 1 is equipped with a fixing part for heating and fixing a toner image formed on transfer material P and can perform control of thinning of the partial supply of the power to be supplied to the fixing heater 42 of the fixing part, according to ON/OFF in half wave units of commercial power supply voltage. The image forming apparatus 1 is equipped with a load means 70 which is provided separately from the fixing heater 42, and a power supply control means 61 which supplies power to the load means 70, during a half period where the power is not supplied to the fixing heater 42 and which does not supply power to the load means 70 during the half period, when the power is supplied to the fixing heater 42 during the control of partial supply. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a fixing unit that heats and fixes a toner image formed on a transfer material.

In the image forming apparatus having the above-described configuration, it is conventionally known that the power supplied to the fixing heater of the fixing unit is thinned out in units of half a commercial frequency. For example, in the image forming apparatus described in Patent Document 1, in the temperature control of the fixing heater, the above-described thinning control is performed in order to prevent the occurrence of temperature ripple due to overshoot. Specifically, temperature detecting means for detecting the temperature of the fixing heater, switch means for turning on / off the energization of the fixing heater, and switching at a predetermined control timing in accordance with the detected temperature to set the heating roller to the target temperature. Average change obtained by dividing the difference between the current detected temperature and the detected temperature detected at the immediately preceding control timing by the control interval therebetween, in an image forming apparatus comprising a switch control means for setting the ON / OFF ratio of the means It is disclosed that the predicted temperature of the fixing heater at the next control timing is calculated using the rate, and when the predicted temperature exceeds the target temperature, the ON / OFF ratio is changed to reduce the average rate of change.
JP 2004-233543 A

However, if the thinning control as described above is performed when the image forming apparatus and the fluorescent lamp are connected to the same distribution line, the fixing heater consumes a large amount of power. Flows, and a voltage drop occurs according to the resistance value of the distribution line, while the half cycle during non-energization does not cause such a voltage drop, and the fluorescent lamp may flicker.
More specifically, for example, in the conventional image forming apparatus 101 shown in FIG. 9A, the power of the commercial power source is transformed to a low voltage by the low voltage power source 102 and supplied to the overall control circuit 103. Further, the power of the commercial power supply is also supplied to the fixing heater 105 through the switch means 104 while maintaining a high voltage. The power supplied to the fixing heater 105 is thinned out by the switch control circuit 106 at a predetermined timing.

  In such an image forming apparatus 101, when thinning control is performed to thin out one half wave into three half waves, the voltage waveform of the current path (indicated by B in FIG. 9A) to the fixing heater 105 is as shown in FIG. c), the voltage waveform in the current path (indicated by A in FIG. 9A) from the commercial power source to the switch means 104 is the voltage that originally becomes a broken line in FIG. 9B. It is disturbed as shown by the solid line in FIG. Therefore, if the image forming apparatus 101 and the fluorescent lamp 107 are connected to the same distribution line 108, the fluorescent lamp 107 becomes dark and flickers every time the voltage drops. This flicker is conspicuous when the distribution line is thin or long and the resistance value of the distribution line is high.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which a fluorescent lamp hardly flickers even if thinning control of power supplied to a fixing heater is performed.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a fixing unit that heat-fixes a toner image formed on a transfer material, and supplies power supplied to a fixing heater of the fixing unit to a half wave of a commercial power source. An image forming apparatus capable of thinning out by a unit, wherein the load unit is provided separately from the fixing heater, and a half cycle in which power is not supplied to the fixing heater during the thinning control is provided to the load unit. And a power supply control means that does not supply power to the load means during a half cycle in which power is supplied to the fixing heater.

  In the image forming apparatus according to the present invention, during the thinning control, power is supplied to the load means during a half cycle when power is not supplied to the fixing heater, and power is not supplied to the load means during half cycle when power is supplied to the fixing heater. Since the power supply control means is provided, voltage fluctuation due to thinning-out control can be suppressed, and the fluorescent lamp hardly flickers.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
[First Embodiment]
<Configuration of image forming apparatus>
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to the first embodiment. As shown in FIG. 1, the image forming apparatus 1 is an electrophotographic copying machine, and includes a document reading unit 10, an image forming unit 20, a paper feeding unit 30, a fixing unit 40, a post-processing unit 50, and a control unit 60. Is provided.

The document reading unit 10 reads an image of a document and outputs digital image data, and includes a document feeding table 11, a platen roller 12, a platen glass 13, an image sensor 14, and a document discharge table 15.
Documents placed on the document feeder 11 are conveyed one by one to the reading position on the platen glass 13 by the platen roller 12. The image sensor 14 receives image light from the original conveyed to the reading position and converts it into an image signal. The read originals are accumulated on the original discharge table 15. It is also possible to place the document directly on the platen glass 13 and read it with the image sensor 14.

The image forming unit 20 forms an image on a recording paper P as a transfer material by an electrophotographic method, and includes a photosensitive drum 21, a charging device 22, an exposure device 23, a developing device 24, a transfer device 25, and a cleaning device 26. Prepare.
The surface of the photosensitive drum 21 is uniformly charged to a predetermined potential by the charging device 22. A toner image is formed on the surface of the photosensitive drum 21 after the uniform charging process by image exposure by the exposure device 23 and development by the developing device 24. The formed toner image is transferred onto the recording paper P by the transfer device 25. The toner remaining on the surface of the photosensitive drum 21 after the transfer is scraped off by the cleaning device 26 and removed.

The paper supply unit 30 supplies the recording paper P to the image forming unit 20 and includes cassettes 31 a to 31 d, paper supply units 32 a to 32 d, registration rollers 33, a conveyance belt 34, and a reverse conveyance device 35.
The recording sheets P accommodated in the cassettes 31a to 31d are separated and fed one by one by sheet feeding means 32a to 32d that operate upon receiving a sheet feeding start signal. The fed recording paper P is supplied between the photosensitive drum 21 and the transfer device 25 by the registration roller 33, and is transferred to the fixing unit 40 by the transfer belt 34 after the toner image is transferred. In the case of double-sided printing, the recording paper P is reversed by the reverse conveying device 35 and supplied again upstream of the registration roller 33.

The fixing unit 40 fixes the toner image on the recording paper P. Details of the fixing unit 40 will be described later.
The post-processing unit 50 performs post-processing such as sorting, stapling, and punching on the recording paper P discharged from the fixing unit 40.
The control unit 60 outputs control signals for controlling the operations of the image forming unit 20, the paper feeding unit 30, the fixing unit 40, the post-processing unit 50, and the like according to the print data and the printer control command. It performs a forming operation, and includes a power supply control means 61, a power conversion circuit 62, and an overall control circuit 63 which will be described later.

FIG. 2 is a diagram illustrating a configuration of the fixing unit. As shown in FIG. 2, the fixing unit 40 includes a heating roller 41, a fixing heater 42, a pressure roller 43, a cleaning roller 44, separation claws 45 and 46, a conveyance roller 47, and a temperature detection unit 48.
The recording paper P to which the toner image has been transferred is conveyed to the nip portion between the heating roller 41 and the pressure roller 43 that are arranged to face each other. The fixing heater 42 is, for example, a halogen lamp built in the heating roller 41 and heats the heating roller 41. When the recording paper P passes through the nip portion, heat from the heating roller 41 and pressure due to the action of the pressure roller 43 are applied, and unfixed toner is melted and fixed on the recording paper P by these heat and pressure. To do.

The recording paper P that has passed through the nip portion is peeled off from the heating roller 41 or the pressure roller 43 by the separation claws 45 and 46 arranged so that the leading end thereof is in contact with the heating roller 41 or the pressure roller 43, and is conveyed by the conveying roller 47. It is conveyed to the processing unit 50. The surface of the heating roller 41 is cleaned by the cleaning roller 44 constantly or periodically.
The temperature detection unit 48 is an infrared temperature sensor with a lens, for example, and detects the surface temperature of the heating roller 41 and outputs the detection result to the power supply control unit 61 as temperature information. The temperature detection means 48 may be configured to detect the temperatures of both the heating roller 41 and the pressure roller 43 and output the detection results to the power supply control means 61 as temperature information.

<Configuration of power supply control means>
The power supply control means 61 turns on and off the fixing heater 42, which is a halogen lamp, based on the temperature information, and maintains the surface temperature of the heating roller 41 at the target temperature. Further, when the fixing heater 42 is turned on, the supply power to the fixing heater 42 is controlled to be thinned out at a predetermined timing.

  The predetermined timing is, for example, when the temperature of the heating roller 41 approaches the target temperature. By controlling the thinning at this timing, the power supplied to the fixing heater 42 is reduced, and the temperature ripple due to overshoot is reduced. Can be prevented. The power supply control means 61 determines whether or not to perform the thinning control based on the temperature information from the temperature detection means 48.

3A and 3B are diagrams for explaining the thinning control according to the first embodiment, in which FIG. 3A is a block diagram showing a configuration relating to thinning control, and FIG. 3B is a voltage waveform of a current path indicated by A in FIG. FIG. 4C is a voltage waveform diagram of a current path indicated by B in FIG. 4A, and FIG. 4D is a voltage waveform diagram of a current path indicated by C in FIG.
As shown in FIG. 3A, the power supply control unit 61 includes a switch unit 611 and a switch control circuit 612, and switches and supplies the power input to the image forming apparatus 1 to the fixing heater 42 and the battery 70. The battery 70 is a secondary battery, for example, and is charged by a charging device 71 interposed between the switch unit 611 and the battery 70.

The switch means 611 is, for example, a pair of triacs inserted individually in a current path to the fixing heater 42 and a current path to the battery 70 via the charging device 71, and is output from the switch control circuit 612. The conduction is controlled by the control signal.
The switch control circuit 612 determines whether or not to perform thinning control based on the temperature information from the temperature detection means 48, and outputs a control signal for thinning control to the switch means 611 when it is determined to perform thinning control. To do. The thinning-out control is performed in units of a half wave of the commercial power supply. Electric power is supplied to the capacitor 70 in a half cycle in which power is supplied to the fixing heater 42, and power is supplied to the capacitor 70 in a half cycle in which power is not supplied to the fixing heater 42. Is done.

  For example, when the thinning control is performed so that the power applied to the fixing heater 42 is thinned out to one half wave, the voltage waveform of the current path (indicated by B in FIG. 3A) to the fixing heater 42. Is as shown in FIG. On the other hand, the voltage waveform of the current path (indicated by C in FIG. 3A) leading to the charging device 71 is as shown in FIG. Therefore, the voltage waveform of the current path from the commercial power source to the switch means 611 (indicated by A in FIG. 3 (a)) is a stable voltage balanced in each positive and negative half cycle as shown in FIG. 3 (b). Even if the image forming apparatus 1 and the fluorescent lamp 2 are connected to the same distribution line 3, the fluorescent lamp 2 hardly flickers.

Note that when the capacitor 70 has the same amount of load as the fixing heater 42, the voltage waveform of the current path from the commercial power source to the switch unit 611 is more stable, and therefore the fluorescent lamp 2 is less likely to flicker.
FIG. 4 is a circuit diagram for explaining the details of the power supply control means. FIG. 5 is a diagram showing a timing table of the thinning control signal.

  A portion surrounded by a broken line in FIG. 4 is the power supply control means 61. A zero cross detection circuit 64 for detecting a zero cross of the alternating current is connected to an INT input terminal of the CPU as the switch control circuit 612. The CPU receives the zero-cross pulse transmitted from the zero-cross detection circuit 64, and immediately after the zero-cross pulse falls, to the control signal OUT1 for supplying power to the fixing heater 42 or to the battery 70 as shown in FIG. A control signal OUT2 for supplying power is output.

When the control signal OUT1 is at the H level, the transistor TR1 is turned off and the light emitting diode on the light emitting side of the phototriac PT1 is turned off. Therefore, the light receiving side of the phototriac is also turned off, and no gate current flows through the triac T1. Therefore, the triac T1 is OFF and no power is supplied to the fixing heater 42.
On the other hand, when the control signal OUT1 is at the L level, the transistor TR1 is turned on, the light emitting diode of the phototriac PT1 is turned on, the light receiving side of the phototriac PT1 is also turned on, and the current is limited to the triac T1 by the resistor R1 or R2. Gate current flows. Therefore, the triac T1 is turned on and electric power is supplied to the fixing heater 42.

The connection between the resistor R3 and the capacitor C1 connected in parallel to the triac T1 is a so-called snubber circuit, and the triac T1 is automatically turned on when there is a sudden change in the power supply voltage due to the influence of external noise or the like. To prevent.
Note that the flow of output of the control signal OUT2 is the same as that of the control signal OUT1, and description thereof is omitted.

  The control signal OUT1 and the control signal OUT2 are composed of a signal consisting of a predetermined number of ONs and a predetermined number of OFFs that regularly change in half-wave units. Based on the count result of the number of zero cross pulses, for example, as shown in FIG. It is output at such timing. In the example illustrated in FIG. 5, the CPU outputs the control signal OUT1 for the first two half-waves with three half-waves as one cycle, and outputs the control signal OUT2 for the remaining one half-wave. The fixing heater 42 is energized for a period of 2 half-waves in the 3 half-waves by the control signal OUT1, and the capacitor 70 is energized for the period of 1 half-wave in the 3 half-waves by the control signal OUT2.

<Power conversion circuit>
Returning to FIG. 3, the electric power charged in the battery 70 is supplied to the fixing heater 42 or supplied to the overall control circuit 63 after the voltage level is adjusted by the power conversion circuit 62 of the control unit 60.
FIG. 6 is a circuit diagram for explaining details of the power conversion circuit. As shown in FIG. 6, the power conversion circuit 62 includes a power supply control circuit 621, a power supply switch means 622, and an auxiliary power supply means 624 including a DC / AC converter 623, a discharge control circuit 625, a discharge switch means 626, and And a discharging means 628 including a DC / DC converter 627.

  The auxiliary power supply unit 624 supplies the electric power of the battery 70 to the fixing heater 42. The capacitor 70 and the fixing heater 42 are connected via a power supply switch unit 622 and a DC / AC converter 623. When the power supply control circuit 621 turns on the power supply switch unit 622 at a predetermined timing, the DC / AC converter The electric power of the battery 70 is converted from direct current to alternating current by 623 and supplied to the fixing heater 42. By doing in this way, the electric power charged in the battery 70 can be used effectively. In addition, when supplying the electric power of the battery 70 to the fixing heater 42, it is preferable to supply the electric power so as to be synchronized with the frequency of the commercial power source.

  The predetermined timing for supplying the electric power of the battery 70 to the fixing heater 42 is, for example, during the energy saving mode of the image forming apparatus 1. In that case, if the power supply control circuit 621 monitors whether or not the image forming apparatus 1 is in the energy saving mode and the image forming apparatus 1 needs to turn on the fixing heater 42 during the energy saving mode, the power supply control circuit 621 performs power supply. The switch means 622 is turned on. The predetermined timing is not limited to during the energy saving mode. However, in order to stably supply power to the fixing heater 42, it is preferable that the thinning control is not being performed.

  The discharging means 628 discharges the electric power of the battery 70 from the overall control circuit 63. The battery 70 and the overall control circuit 63 are connected via a discharge switch means 626 and a DC / DC converter 627. When the voltage of the battery 70 exceeds a predetermined value, the discharge control circuit 625 causes the discharge switch means 626 to be Turned on. Then, the electric power of the battery 70 is converted into a frequency suitable for the overall control circuit 63 by the DC / DC converter 627 and discharged outside the apparatus through the overall control circuit 63. Thereby, the overvoltage of the battery 70 can be prevented.

The power supply by the auxiliary power supply unit 624 and the discharge by the discharge unit 628 may be performed simultaneously.
[Second Embodiment]
The second embodiment is greatly different from the first embodiment in that the load means is a dehumidifying heater that dehumidifies each component in the apparatus. Therefore, points different from the first embodiment will be mainly described, and the same points as those of the first embodiment will be omitted to avoid duplication, and the same constituent elements will be denoted by the same reference numerals.

FIG. 7 is a diagram illustrating a configuration of an image forming apparatus according to the second embodiment. As shown in FIG. 7, the image forming apparatus 4 includes a document reading unit 10, an image forming unit 20, a paper feeding unit 30, a fixing unit 40, a post-processing unit 50, and a control unit 60.
Further, the image forming apparatus 4 includes a photoconductor heater 81, a dew condensation prevention heater 82, and a paper feed dehumidifying heater 83 as a dehumidifying heater of a dehumidifier for dehumidifying the inside of the apparatus. The photoconductor heater 81 is disposed inside the photoconductor drum 21 and prevents condensation of the photoconductor drum 21. The dew condensation prevention heater 82 is disposed in the vicinity of the transfer device 25 and prevents the dew condensation around it. The paper feed dehumidifying heater 83 is disposed at the lower part of the cassette 31C and dehumidifies the surrounding area.

8A and 8B are diagrams for explaining the thinning control according to the second embodiment, in which FIG. 8A is a configuration block diagram related to thinning control, FIG. 8B is a voltage waveform diagram of a current path indicated by A in FIG. (C) is a voltage waveform diagram of a current path indicated by B in (a), and (d) is a voltage waveform diagram of a current path indicated by C in (a).
As shown in FIG. 8A, the power input to the image forming apparatus 4 is supplied to the fixing heater 42 or the dehumidifying heaters 81 to 83 via the power supply control unit 90 as a power control unit. The power supply control unit 90 includes a fixing heater switch unit 91 interposed between the commercial power source and the fixing heater 42, a dehumidifying heater switch unit 92 interposed between the commercial power source and the dehumidifying heaters 81 to 83, and The switch control circuit 93 controls the switch means 91 and 92.

The switch means 91 and 92 are, for example, a pair of triacs inserted individually in a current path to the fixing heater 42 and a current path to the dehumidifying heaters 81 to 83, and are output from the switch control circuit 93. The conduction is controlled by a signal.
The switch control circuit 93 determines whether or not to perform the thinning control based on the temperature information from the temperature detecting means 48. When it is determined that the thinning control is performed, different control signals are output to the switch units 91 and 92, respectively. The control signal is output based on the temperature information from the temperature detection means 48 and the zero cross pulse from the zero cross detection circuit 94. The switch units 91 and 92 turn on / off the fixing heater 42 and the dehumidifying heaters 81 to 83 based on the control signals.

The thinning control is performed in units of half wave of commercial power. The switch means 91 and 92 supply power to the dehumidifying heaters 81 to 83 during a half cycle when power is not supplied to the fixing heater 42, and supply power to the dehumidifying heaters 81 to 83 during a half cycle when power is not supplied to the fixing heater 42. Are controlled in synchronism with each other.
For example, when the thinning control for thinning out one half wave to three half waves is performed on the fixing heater 42, the voltage waveform of the current path (indicated by B in FIG. 8A) to the fixing heater 42 is as shown in FIG. As shown in c). On the other hand, the voltage waveform of the current path (denoted by C in FIG. 8A) leading to the dehumidifying heaters 81 to 83 is as shown in FIG. Therefore, the voltage waveform of the current path (indicated by A in FIG. 8A) from the commercial power source to each of the switch means 91 and 92 is balanced and stable in each positive and negative half cycle as shown in FIG. 8B. Even if the image forming apparatus 4 and the fluorescent lamp 2 are connected to the same distribution line 3, the fluorescent lamp 2 is less likely to flicker.

[Modification]
Although the image forming apparatus according to the present invention has been described based on the embodiments, the present invention is not limited to these embodiments.
For example, the load means is not limited to a capacitor or a dehumidifying heater, and may be any device that consumes a large amount of power, and preferably has a load amount similar to that of the fixing heater.

  The thinning-out control is not limited to thinning out the waveform of one half-wave with three half-waves as one cycle as in the above embodiment, and any thinning-out control may be used as long as it is thinned out in units of commercial power. Further, the thinning-out control may be performed at a predetermined timing during lighting as in the above-described embodiment, or may be always performed during lighting of the fixing heater.

  The present invention can be widely applied to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these.

1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment. FIG. 3 is a diagram illustrating a configuration of a fixing unit. It is a figure explaining the thinning-out control which concerns on 1st Embodiment, (a) is a block diagram which shows the structure regarding thinning-out control, (b) is a voltage waveform figure of the current path shown by A in (a), (c ) Is a voltage waveform diagram of a current path indicated by B in (a), and (d) is a voltage waveform diagram of a current path indicated by C in (a). It is a circuit diagram for demonstrating the detail of an electric power supply control means. It is a figure which shows the timing table of a thinning-out control signal. It is a circuit diagram for demonstrating the detail of a power converter circuit. It is a figure which shows the structure of the image forming apparatus which concerns on 2nd Embodiment. It is a figure explaining the thinning-out control which concerns on 2nd Embodiment, Comprising: (a) is a block diagram regarding a thinning-out control, (b) is a voltage waveform figure of the current path shown by A in (a), (c) is 4A is a voltage waveform diagram of a current path indicated by B in FIG. 4A, and FIG. 3D is a voltage waveform diagram of a current path indicated by C in FIG. It is a figure explaining the thinning-out control which concerns on a prior art example, Comprising: (a) is a structure block diagram regarding thinning-out control, (b) is a voltage waveform figure of the current path shown by A in (a), (c) is (a). FIG. 6 is a voltage waveform diagram of a current path indicated by B in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,4 Image forming apparatus 40 Fixing part 42 Fixing heater 63, 81-83 Load means P Transfer material

Claims (7)

An image forming apparatus that includes a fixing unit that heat-fixes a toner image formed on a transfer material, and that can control thinning out power to be supplied to a fixing heater of the fixing unit in units of a half wave of a commercial power source.
Load means provided separately from the fixing heater;
During the thinning control, power supply control means for supplying power to the load means during a half cycle in which power is not supplied to the fixing heater, and for supplying power to the load means in a half cycle in which power is supplied to the fixing heater. An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the load unit has a load amount similar to that of the fixing heater.   The image forming apparatus according to claim 1, wherein the load unit is a capacitor.   The image forming apparatus according to claim 3, further comprising an auxiliary power supply unit configured to supply power charged in the capacitor to the fixing heater.   The image forming apparatus according to claim 4, wherein the auxiliary power supply unit supplies power to the fixing heater when the thinning control is not being performed.   The image forming apparatus according to claim 3, further comprising: a discharging unit that discharges the electric power charged in the capacitor.   The image forming apparatus according to claim 1, wherein the load unit is a dehumidifying heater that dehumidifies each component in the apparatus.

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