JP5222647B2 - Phase control device, fixing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a phase control device that performs phase control of a power supply voltage, and a fixing device including the phase control device.

  When starting supply of electric power from a commercial AC power source to an electric device, a large inrush current may flow through a load of the electric device. When a lighting device such as a fluorescent lamp shares a power source with this electric device, flickering (flicker phenomenon) may occur in the lighting device due to the generation of the inrush current.

  An image forming apparatus is taken as an example of an electrical device. Some image forming apparatuses include a heating element such as a halogen heater in order to fix an image on a recording sheet by thermocompression bonding. Since the heating element consumes a large amount of power, a large inrush current flows when the heating element is turned on. As a result, a flicker phenomenon is likely to occur in an illumination device that shares an AC power supply with the image forming apparatus.

  In order to prevent the flicker phenomenon, a technique for preventing the occurrence of a large inrush current by controlling the phase of voltage supply to the load has been proposed. For example, in Patent Document 1, an image forming apparatus that includes a switch for turning on / off the energization of the fixing heater, a trigger circuit that operates the switch, and a control unit that starts energization of the fixing heater after a predetermined time has elapsed from the zero cross point. Is described.

In the conventional phase control, when a certain time has elapsed from the edge of the zero cross signal output from the zero cross detection circuit, the zero cross point is set, and the energization of the fixing heater is switched on / off based on the zero cross point.
JP-A-9-106215 (paragraphs [0008] to [0009], FIG. 2 etc.)

  The width of the zero cross signal varies depending on factors such as fluctuations in power supply voltage, fluctuations in voltage frequency, variations in performance of each element constituting the circuit, temperature in the machine, and the like. Then, even if energization of the fixing heater is turned on when a predetermined time has elapsed from the edge of the zero cross signal, the difference between the on timing and the actual zero cross point becomes large. When the deviation becomes large in this way, the inrush current becomes large despite the phase control, and the flicker phenomenon cannot be effectively prevented.

  In view of the above-described conventional problems, an object of the present invention is to provide a technique capable of preventing the occurrence of a large inrush current in an electric device even under various conditions.

  The phase control device according to claim 1 is a phase control device that performs phase control of power supply from an AC power supply to a load, and outputs a pulse signal having a width of a period in which the amplitude of the AC voltage is equal to or less than a predetermined value. A zero cross signal output unit, a phase control unit that controls the phase of power supply to the load with a predetermined time from the rising edge of the pulse signal as a zero cross point, and a signal width that detects the width of the pulse signal A detection unit; and a correction unit that increases the predetermined time as the width of the pulse signal increases from the detection result of the signal width detection unit.

  According to this phase control device, even if various conditions such as fluctuation of the pulse signal width from the zero cross signal output unit occur, the effect of phase control can be exhibited and the generation of a large inrush current can be prevented. Become.

  Factors that cause the pulse signal width from the zero-cross signal output unit to vary include the frequency of the AC voltage, the maximum value of the amplitude of the AC voltage, the temperature in the apparatus, and the like.

  Therefore, as described in claim 2, in the phase control device according to claim 1, the signal width detection unit is a frequency detection unit that detects the frequency of the AC voltage, and the correction unit decreases as the frequency decreases. The predetermined time may be lengthened.

  According to a third aspect of the present invention, in the phase control device according to the first aspect, the signal width detection unit is an amplitude detection unit that detects the maximum value of the amplitude of the AC voltage, and the correction unit is the maximum The predetermined time may be lengthened as the value decreases.

  Further, as described in claim 4, in the phase control device according to any one of claims 1 to 3, the phase control device further includes a temperature detection unit that detects a temperature in the device, and the correction unit adjusts to the temperature. The predetermined time may be further corrected.

  The phase control device described above can be applied to a fixing device that fixes an image on a recording sheet. Accordingly, the fixing device according to claim 5 includes a heating unit that applies heat to the recording paper on which an image is placed, and a pulse having a width in a period in which the amplitude of the AC voltage supplied to the heating unit is a predetermined value or less. A zero cross signal output unit that outputs a signal, a phase control unit that performs phase control of power supply to the load, with a predetermined time from the rising edge of the pulse signal as a zero cross point, and a width of the pulse signal A signal width detection unit to detect, and a correction unit that increases the predetermined time as the width of the pulse signal increases from the detection result of the signal width detection unit.

  According to the phase control device of the present invention, even if various conditions such as fluctuation of the pulse signal width from the zero cross signal output unit occur, the effect of phase control is exhibited and the generation of a large inrush current can be prevented. It becomes possible.

[1] First Embodiment A copying machine 100 according to an embodiment of the present invention will be described below with reference to the drawings.

<1. Overview of Copier 100>
First, the outline of the copying machine 100 will be described with reference to FIG. FIG. 1 is a block diagram showing a main configuration of the copying machine 100.

  As shown in FIG. 1, a copying machine 100 includes an operation panel 2 that receives an instruction from a user, an image reading unit 3 that acquires image data from a document, and an image forming unit that forms an image made of a developer based on the image data. 4. A transfer unit 5 for transferring an image formed by the image forming unit 4 onto a recording paper, a fixing device 6 for fixing the image after transfer onto the recording paper by thermocompression, and each unit in the copying machine 100. A main controller 7 and the like are provided.

  The operation panel 2 includes hard keys and a touch panel having a liquid crystal display panel capable of displaying soft keys.

  The image reading unit 3 includes an optical member such as a lens or a mirror and a photoelectric conversion device such as a CCD.

  As the image forming unit 4, an apparatus for forming an image by an electrophotographic method can be suitably used.

  Regarding the fixing device 6, the following <2. Described in the> column.

  The control device 7 can be realized by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and other storage media. In this case, the control function of the control device 7 is realized by the CPU reading and executing the control program in the ROM. The RAM can function as a work area for the CPU.

<2. Fixing device 6>
(2-1) Overview of Fixing Device 6 Next, with reference to FIG. 2, the phase control of the power supply voltage in the fixing device 6 will be described.

  As shown in FIG. 2, the fixing device 6 includes a noise filter circuit 61, a rectifier circuit 62, an AC / DC power supply circuit, a switch unit 64, a heater 65, a phase control device 67, and the like. The heater 65 is connected to the AC power supply 200 via the power supply wiring R and the GND wiring G.

  The noise filter circuit 61 is disposed between the AC power supply 200 and the heater 65 on the power supply wiring R and the GND wiring G, and removes noise from the AC voltage.

  The rectifier circuit 62 is disposed between the noise filter circuit 61 and the heater 65 on the power supply wiring R and the GND wiring G, and full-wave rectifies the voltage from which noise has been removed. That is, the AC voltage is full-wave rectified by the rectifier circuit 62, so that the negative half-wave is inverted positively and the full-wave is adjusted in the positive direction. The waveform of the AC voltage after full-wave rectification is the same as the input voltage waveform Vr (FIG. 4A) to the Zener diode 671c. Therefore, the voltage after full-wave rectification may be described with reference to FIG.

  The AC / DC power supply circuit 63 is arranged between the rectifier circuit 62 and the heater 65 on the power supply wiring R and the GND wiring G, and the AC / DC conversion circuit and the voltage after full-wave rectification are suitable for the heater 65. Equipped with electronic components such as a transformer to adjust the value.

  The switch unit 64 is provided between the AC / DC power supply circuit 63 and the heater 65 on the power supply wiring R, and the heater 65 can be switched between an energized state and a non-energized state by being turned on / off. That is, the switch unit 64 turns on / off the power supply to the heater 65. As the switch unit 64, a conventionally known switch element such as SSR (Solid State Relay) can be used.

  The heater 65 is provided in a heat roller that is a roller member (not shown). The heater 65 is designed to increase in temperature when energized. The fixing device 6 includes a pressure roller disposed opposite to the heat roller. The recording paper is sandwiched between the pressure roller and the heat roller, and heat and pressure are applied to the recording paper, whereby an image is displayed. Fix on recording paper.

(2-2) Phase control device 67
As shown in FIG. 2, the phase control device 67 includes a zero-cross detection circuit 671, a thermometer 672, a control unit 673, and the like.

  The zero cross detection circuit 671 outputs a zero cross signal when the amplitude of the AC voltage is equal to or less than a certain value. Specifically, the zero cross detection circuit 671 includes an input side circuit 671a and an output side circuit 671b.

  The input side circuit 671a is connected between the rectifier circuit 62 and the noise filter 61, two diodes connected to the power supply wiring R and the GND wiring G, a resistor connected to each diode, and both resistors. A Zener diode 671c and a light emitting diode 671d connected to the Zener diode 671c. The light emitting diode 671d is connected to the Zener diode 671c in the opposite direction to the Zener diode 671c.

  The output side circuit 671b includes a phototransistor 671e that receives light from the light emitting diode 671d, various resistors, a transistor, and the like, and is connected to the control unit 67. The light emitting diode 671d and the phototransistor 671e of the input side circuit 671a constitute a phototransistor 671f. That is, the light emitting diode 671d is an input side element, and the phototransistor 671e is an output side element.

  The thermometer 672 is disposed in the vicinity of the heater 65. The temperature information obtained by the thermometer 672 is sent to the control unit 673.

  The control unit 673 can control on / off of the switch unit 64 by receiving power supply from a power source (not shown). The controller 673 will be described with reference to the block diagram of FIG.

  As shown in FIG. 3, the control unit 673 includes a frequency detection unit 673a, a voltage detection unit 673b, a memory 673c, a timing determination unit 673d, and a switch control unit 673e. Each unit of the control unit 673 may be realized by hardware or may be realized by software. When implemented by software, the control unit 673 includes a CPU, a ROM, a RAM, and other storage media. In the ROM, a program for the CPU to realize the functions of the respective functional units of the control unit 673 is stored.

The memory 673c is a non-volatile memory and stores a correction coefficient α. Specifically, the memory 673c stores three correction coefficient tables A1 to A3. In the correction coefficient table A1 to A3, the correction coefficient of the three types used in the correction of the time T _ON of the later α (α1~α3) is the frequency of the power supply voltage, the voltage value, associated with each such machine temperature Stored. Details of each correction coefficient α and other functional units of the control unit 673 will be described in the section (2-3) below.

(2-3) Phase Control The operation of the fixing device 6 at the time of phase control will be described with reference to FIGS.

[Zero cross signal]
A zero cross signal used in phase control will be described with reference to FIG. 4A is a chart showing the AC voltage Vr input to the Zener diode 671c, FIG. 4B is a forward voltage Vf of the photocoupler 671f, and FIG. 4C is a chart showing the waveform of the zero cross signal P.

  In the zero cross detection circuit 671, the AC voltage Vr that has passed through the diode and the resistance of the input side circuit 671a draws a waveform as shown in FIG. This voltage Vr is input to the Zener diode 671c. When the voltage Vr becomes larger than the Zener voltage Vz, a current in the direction opposite to the normal direction flows through the Zener diode 671c. Then, as shown in FIG. 4B, the forward voltage Vf of the photocoupler 671f is clipped by the Zener voltage Vz by the Zener diode 671c.

  As shown in FIG. 4C, in the output side circuit 671b, when the phototransistor 671e is off, a zero cross signal P that is a pulse signal is output to the control unit 673. When the AC voltage Vr exceeds the Zener voltage Vz, a current flows through the light emitting diode 671d and the phototransistor 671e is turned on, so that the zero cross signal P is not output. As described above, the width W of the zero cross signal P is the same as the width of the period in which the voltage Vr is equal to or less than the Zener voltage Vz.

[Phase control at power-on]
Phase control performed when the power of the copying machine 100 is turned on, that is, when energization of the heater 64 is started will be described with reference to FIG. FIG. 5 is a flowchart showing phase control by the switch control unit 673e.

Switch controller 673e, when the time _{T ON} from the rising edge of the zero-crossing signal P has elapsed (Yes in FIG. 4 (c), the step S11 in FIG. 5), the switch controller 673e is remote to turn on the switch portion 64 A signal is output ("ON" in FIG. 4A, step S12 in FIG. 5). When the switch unit 64 is turned on in this manner, the heater 65 is energized.

When the time T _OFF elapses after the switch unit 64 is turned on (FIG. 4A, Yes in step S13 in FIG. 5), the switch control unit 673e turns off the switch unit 64 (“OFF” in FIG. 4A). "Step S14 in FIG. 5).

The “time T _ON ” is set to a time corresponding to the distance from the rising edge of the zero cross signal P to the zero cross of the waveform of the AC voltage. Further, as will be described later, the time _TON is appropriately corrected.

The switch controller 673e, a plurality of time has a _{T OFF,} during one phase control operation, for each half-wave or one wave, the time _{T OFF} used becomes longer. That is, the phase angle when the switch 64 is turned off gradually increases. As a result, the period during which the switch unit 64 is turned on gradually increases, so that the power supplied to the heater 65 gradually increases.

  The above phase control is performed when the power of the copying machine 100 is turned on, when returning from the sleep state, or the like.

[Correction of time _{T ON]}
The pulse width W of the zero cross signal P varies depending on the frequency, voltage value, temperature, and the like of the AC voltage. Therefore, if the time _TON is fixed, the difference between the timing at which the switch unit 64 is turned on and the zero cross point increases when the pulse width W fluctuates due to these factors. If this deviation becomes large, the phase control effect of suppressing the inrush current at the time of power-on or the like cannot be sufficiently obtained. As a result, a flicker phenomenon occurs in the lighting device connected to the AC power supply 200.

In contrast, in the copying machine 100 of the present embodiment, the control unit 673, that the time T _ON in accordance with the variation of the pulse width W of the zero-crossing signal is corrected, the zero cross point is the timing to turn the switch portion 64 It can be adapted to. Therefore, it is possible to effectively prevent the occurrence of the flicker phenomenon in the lighting device when the copying machine 100 is powered on.

Details of the correction time T _ON, will be described with reference to FIG. Figure 6 is a flowchart illustrating a process of correcting the time of the control unit 673 of the time T _ON.

As illustrated in FIG. 6, the timing determination unit 673d refers to elements that affect the pulse width W of the zero-cross signal, such as the frequency of the power supply voltage, the voltage value, and the temperature in the apparatus (step S21). Then, correction coefficients α (α1 to α3) corresponding to the reference results are respectively selected from the correction coefficient tables A1 to A3 (step S22). Then, the timing determining unit 673d is selected correction coefficient α (α1~α3), by multiplying the initial value _{T 0,} it obtains the time _{T ON} after correction (step S23).

  The frequency of the AC voltage referred to by the timing determination unit 673d in step S21 is such that the frequency detection unit 673a detects the edges of several pulses of zero-cross signals before the start of phase control, and detects the number of detected edges within a unit time. Get by that. The voltage value is obtained by the voltage detection unit 673b detecting the maximum value of the amplitude of the power supply voltage. In the present embodiment, the voltage detection unit 673b detects the maximum value Vmax (FIG. 4A) of the amplitude of the AC voltage as the voltage value. The temperature is measured by a thermometer 672.

The correction coefficient α (α1 to α3) used in step S23 is set as follows. The pulse width W increases as the frequency of the AC voltage decreases. Thus, as more time T _ON frequency becomes longer becomes longer, the first correction coefficient α1 is set larger. Further, the pulse width W increases as the voltage value decreases. Therefore, the second correction coefficient α2 is set to be large so that the time _TON becomes longer as the voltage value becomes smaller. On the other hand, the fluctuation of the pulse width W due to temperature varies depending on the properties of the elements constituting the circuit and is not constant like the voltage frequency and voltage value. For this reason, the correction coefficient α3 for temperature is appropriately set in consideration of the configuration of individual devices and circuits, variation of each element, and the like.

Timing timing determination unit 673d performs the correction (Fig. 6) of the time T _ON when turning the copier 100, each every elapse of a predetermined time during power up, the number of printed sheets reaches a predetermined value or the like, be set as appropriate However, it is not specifically limited.

The switch control unit 673e can keep the temperature of the heater 65 constant by turning on / off the switch unit 64 based on the detection result of the thermometer 672. In other words, thermometer 672 is used for both temperature control set and the heater 65 of time _{T ON.} Therefore, the copying machine 100 has an advantage that the configuration of the apparatus can be simplified as compared with the case where separate thermometers are used for these two processes. However, thermometer used when setting these times T _ON may be provided separately from those used for the temperature adjustment of the heater 65.

[2] Other Embodiments (a) In the copying machine 100, the phase control may be performed by the switch controller 673e not only when the heater 64 is energized but also when the heater 64 is de-energized. . At this time, contrary to the start of energization, the period during which the switch unit 64 is on is gradually shortened so that the supply current to the heater 64 gradually decreases for each wave or half wave of the AC voltage. . In order to adjust the on / off timing of the switch unit 64 to the zero cross point, the timing correction by the same flow as in FIG.

(B) The copying machine 100 may include a second timing determination unit that corrects the time T _OFF in the phase control at the start of energization according to the frequency, voltage value, internal temperature, and the like of the AC voltage. The second timing determination unit, for example, the frequency is more time T _OFF the smaller, may be adapted to increase the extent time T _OFF voltage value decreases. As for the temperature, a correction coefficient corresponding to each temperature may be set according to the configuration of the device or circuit, the variation of each element, or the like.

  (C) In the phase control at the start of energization of the heater 64, the switch control unit 673e turns on the switch unit 64 at the zero cross point in the first embodiment, but conversely, between the adjacent zero cross points. The switch unit 64 may be turned on, and then the switch unit 64 may be turned off at a zero cross point.

  (D) The voltage detection unit 673d is an example of an amplitude detection unit that detects the maximum value of the amplitude of the AC voltage. The amplitude detection unit may detect indirectly the maximum value of the amplitude of the AC voltage as in the voltage detection unit 673d, but may detect it indirectly. For example, the amplitude detection unit may detect a voltage value after AC / DC conversion as a value reflecting the maximum value of the amplitude, or can detect a peak-to-peak of a sine waveform of an AC voltage. It may be.

  (E) The timing determination unit 673d is not limited to a configuration in which a correction coefficient set in advance for each element of voltage frequency, voltage value, and temperature is selected, and the correction coefficient is calculated by calculation from the above-described elements. It may be. In addition, the correction may not be performed based on all three elements, but may be performed based on only one of the frequency and the voltage value, or the temperature may be further combined with either one. Correction may be performed.

(F) The above-described three elements such as the frequency are merely examples of elements that affect the pulse width W of the zero-cross signal, so that the control unit 673 has the rising edge of the zero-cross signal instead of the frequency detection unit 673a and the like. In addition, a pulse width detector that measures the pulse width W by detecting a falling edge or the like may be provided. In this case, according to the pulse width W which is detected by the pulse width detector, the timing determining unit 673d it is sufficient so as to correct the time T _ON. The timing determination unit 673, in addition to the three elements described above, based on other factors that affect the pulse width W of the zero-crossing signal, may be adapted to correct the time T _ON.

  (G) In the first embodiment, as an example of the fixing device, the form incorporated in the copying machine has been described. However, in addition to this, a similar fixing device can be used as a printer, a facsimile machine, and a multifunction device having these functions. The present invention can be applied to various image forming apparatuses.

  As described above, embodiments obtained by appropriately combining the embodiments described in different columns are also included in the technical scope of the present invention.

1 is a block diagram showing a main configuration of a copying machine 100 according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a main configuration of the fixing device 6 of the copying machine 100. FIG. 3 is a block diagram showing a main configuration of a phase control device 67 of the fixing device 6. FIG. 4A is a chart showing voltages at various parts of the zero-cross detection circuit 671, FIG. 4A is an AC voltage Vr input to the Zener diode 671c, FIG. 4B is a forward voltage Vf of the photocoupler 671f, and FIG. ) Represents the waveform of the zero-cross signal P. The flowchart which shows the phase control by the switch control part 673e. Determination of timing of on of the switch section 64 at the time of phase control, i.e. a flowchart showing a correction processing time T _ON.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Copier 200 AC power supply 6 Fixing device 64 Switch part 65 Heater 67 Phase control apparatus 671 Zero cross detection circuit 672 Thermometer 673 Control part 673a Frequency detection part 673b Voltage detection part 673c Memory 673d Timing determination part (correction part)
673e Switch control unit (phase control unit)

Claims (4)

A phase control device that performs phase control of power supply from an AC power supply to a load,
A zero cross signal output unit that outputs a pulse signal having a width of a period in which the amplitude of the AC voltage is equal to or less than a predetermined value;
A phase control unit that performs phase control of power supply to the load, with a time point after a predetermined time has elapsed from the rising edge of the pulse signal as a zero cross point;
A signal width detector for detecting the width of the pulse signal;
From the detection result of the signal width detection unit, a correction unit that lengthens the predetermined time as the width of the pulse signal increases,
A temperature detection unit for detecting the temperature in the device ,
The signal width detector is a frequency detector that detects the frequency of the AC voltage,
The correction unit is a phase control device that lengthens the predetermined time as the frequency decreases, and further corrects the predetermined time according to the temperature . The signal width detection unit is an amplitude detection unit that detects the maximum value of the amplitude of the AC voltage,
The phase control device according to claim 1, wherein the correction unit increases the predetermined time as the maximum value decreases . A fixing device for fixing an image on a recording paper,
The phase control device according to claim 1 or 2,
A heating unit that applies heat to the recording paper on which the image is placed and is the load;
A fixing device. An image forming apparatus comprising the fixing device according to claim 3.

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