JP2006092180A - Heater device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a heater device capable of reducing a high frequency component caused by suppression of a rush current, by a simple phase control sequence. <P>SOLUTION: While phase control is performed in each cycle of power voltage by a control angle (2π/0.02[s]) × t3[s] and a control angle (2π/0.02[s]) × t4[s] (t4 = t3 + 0.01[s]) in a conventional technology, the phase control is performed once two cycles of the power voltage by a control angle (2π/0.02[s]) × t1[s] and a control angle (2π/0.02[s]) × t2[s] (t2 = t1 + 0.01[s]), and one cycle is set as a blank cycle in this technology. One cycle of the power voltage performing the phase control is set as a first period, the blank cycle is set as a second period, a sum of both the sides is set as a unit period, and it is repeated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heater device used in a fixing device of an image forming apparatus.

  In a toner fixing type image forming apparatus such as a copying machine, a heater device for heating is provided in the fixing device. A heater lamp such as a halogen lamp or a nichrome wire heater is used as a heating source of the heater device. Normally, in such a heater device, the resistance value of the filament or heater wire in a state where current is not supplied is low, and the resistance value increases as the temperature gradually increases after the start of current supply. Therefore, an inrush current flows through the filament and the heater wire immediately after the start of energization. In order to suppress such an inrush current, immediately after the start of energization, phase control in which energization phase control is performed and the current is gradually increased, that is, soft start is performed. A thyristor or a bidirectional thyristor is used as a switching element for performing phase control, and is connected in series with a heating source. Due to the ON / OFF control of the heater current by such a switching element, the voltage waveform applied to the heating source becomes a distorted waveform deviated from the sine wave, so that the current flowing by the phase control has a large amount of high frequency components. This high frequency component is not preferable because it becomes radioactive noise and causes electromagnetic interference in nearby electrical equipment, or becomes conductive noise and returns to the AC power supply system.

In Patent Document 1, in order to reduce the harmonic noise due to the inrush current and the voltage drop causing flicker, for example, a voltage waveform as shown in FIG. 7 is applied to the load (heater lamp) from the start of energization. Describes that phase control is performed. In FIG. 7, during the period in which the switching means is at least one wavelength of the AC power supply wavelength, the first control mode for supplying the load with a relatively large amount of power of the first polarity than the power of the second polarity, and AC A second control mode for supplying power to the load with a relatively large amount of power of the second polarity than the amount of power of the first polarity during a period of one or more wavelengths of the power supply wavelength; and half-wave power of the first polarity And a third control mode for alternately supplying half-wave power of the second polarity to the load, and these are executed in the order of the first control mode, the third control mode, and the second control mode. In the figure, a full wave mode and a blank mode in which no voltage is applied are executed later.
Japanese Patent Laid-Open No. 11-27932 (published on January 29, 1999)

  Patent Document 1 described above is intended to suppress the high-frequency component of the inrush current within the safety standard by executing the first control mode, the third control mode, and the second control mode in this order. There is a problem that a high frequency component of each control mode is superimposed and a specific frequency may be emphasized.

  Further, as is apparent from FIG. 7, the control of Patent Document 1 does not repeat the unit period of phase control even when only the period of the first control mode to the third control mode is combined. There is a problem that the phase control sequence is complicated because the control angles of the voltages of the first polarity and the second polarity as a whole are formed as irregular change periods in which the control angles change in the middle.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to realize a heater device that can reduce high-frequency components due to suppression of inrush current with a simple phase control sequence. is there.

  In order to solve the above-described problems, the heater device of the present invention is a heater device that is fed from an AC power source and capable of energization phase control, and a first period in which the phase control is performed and a second period in which the energization is not performed. It is possible to supply power by repeating the unit period, with the sum of the period as a unit period, and the unit period is n times the half cycle of the voltage of the AC power supply (n is an integer of 3 or more). It is characterized by.

  According to the above-described invention, the energization period is longer than the period of the power supply voltage, whereby the fundamental wave frequency is lowered, the higher-order current components are reduced, and conduction noise and radiation noise can be reduced. In addition, the phase control sequence is simplified because only the unit period needs to be repeated.

  As described above, there is an effect that it is possible to realize a heater device that can reduce high-frequency components due to suppression of inrush current by a simple phase control sequence.

  In order to solve the above problems, the heater device of the present invention is characterized in that the first period has the same number of times as the positive polarity period and the negative polarity period of the current during energization.

  According to the above invention, in a single-phase three-wire generally used as an AC power supply for an electric device fed by a low-voltage indoor wiring, a one-way wiring formed by a neutral wire and one of two active wires. Since the voltage drop due to the direct current of the heater current that flows can be prevented, there is an effect that the unbalance of the voltage drop can be alleviated over the entire single-phase three-wire.

  In the heater device of the present invention, in order to solve the above problems, the first period is one cycle of the voltage of the AC power supply, and each of the positive polarity half cycle and the negative polarity half cycle of the voltage. It is characterized in that the energization is performed once.

  According to the above invention, in a single-phase three-wire generally used as an AC power supply for an electric device fed by a low-voltage indoor wiring, a one-way wiring formed by a neutral wire and one of two active wires. Since the voltage drop due to the direct current of the heater current that flows can be prevented, there is an effect that the unbalance of the voltage drop can be alleviated over the entire single-phase three-wire.

  In the heater device of the present invention, in order to solve the above problem, after the unit period is repeated a predetermined number of times, zero cross control is performed with respect to the energization using a zero cross point of the voltage of the AC power supply as a control angle. It is characterized by that.

  According to the above-described invention, since the high frequency component of the current is less likely to be generated in the zero cross control, the noise can be further reduced and the same switching element for phase control can be used from the start of energization to the steady operation. Play.

  As described above, the heater device according to the present invention may be supplied with power by repeating the unit period, with the sum of the first period in which the phase control is performed and the second period in which the energization is not performed as a unit period. The unit period is n times a half cycle of the voltage of the AC power supply (n is an integer of 3 or more).

  Therefore, there is an effect that it is possible to realize a heater device that can reduce high-frequency components due to suppression of inrush current by a simple phase control sequence.

  An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 4 shows a circuit diagram of the heater device 1 used in the fixing device of the copying machine. The heater device 1 includes a heater lamp 2, a bidirectional thyristor 3, and a gate circuit 4. The heater lamp 2 is composed of, for example, a halogen lamp, but is not limited to a lamp, and may be a heating element generally serving as a heating source such as a nichrome wire heater. The heater lamp 2 and the bidirectional thyristor 3 are connected in series, and the voltage of the commercial AC power supply 5 is applied to this series circuit.

  The gate circuit 4 is a circuit that generates a conduction trigger for the bidirectional thyristor 3, and includes an optical bidirectional thyristor 4a and resistors R1 and R2. The resistor R1, the optical bidirectional thyristor 4a, and the resistor R2 are connected in series in this order, and this series circuit is connected between the T1 terminal and the T2 terminal of the bidirectional thyristor 3. One end of the resistor R1 serving as one end of the series circuit is connected to the T2 terminal, and one end of the resistor R2 serving as the other end of the series circuit is connected to the T1 terminal. The connection point between the optical bidirectional thyristor 4a and the resistor R2 is connected to the gate terminal of the bidirectional thyristor 3.

  In the heater device 1, a control signal converted into a light pulse of a light emitting element such as a light emitting diode is input to the optical bidirectional thyristor 4a from a control circuit (not shown), and the optical bidirectional thyristor 4a becomes conductive at that timing. When the optical bidirectional thyristor 4a is turned on, the voltage of the AC power supply 5 having the phase at that time is divided by the resistors R1 and R2 and applied to the gate terminal of the bidirectional thyristor 3, and the gate current flows and the bidirectional thyristor flows. 3 conducts. Power is supplied to the heater lamp 2 by the conduction of the bidirectional thyristor 3. Therefore, by controlling the timing of the optical pulse input to the optical bidirectional thyristor 4a, the bidirectional thyristor 3 can be phase-controlled and the lighting time of the heater lamp 2 can be controlled. In the following, it is assumed that the circuit of the heater device 1 is composed only of a resistance component, that is, the phase of the current of the heater lamp 2 substantially matches the phase of the power supply voltage, and the current waveform is the waveform of the applied voltage of the heater lamp 2. Suppose they are similar. Therefore, the bidirectional thyristor 3 is turned on at the next zero cross point of the AC power supply 5 after being turned on at the conduction timing of the optical bidirectional thyristor 4a. However, the present invention is not limited to this, and the reactance component is included, so that the phase of the current shifts from the phase of the applied voltage of the heater lamp 2 or the waveform of the current is not similar to the waveform of the applied voltage of the heater lamp 2. It is possible that the bidirectional thyristor 3 is shut off after entering the next half cycle of the voltage. However, even in this case, the effects of the present invention described later can be obtained. In place of the bidirectional thyristor 3, two thyristors connected in reverse parallel can be used. Further, the conduction period can be freely controlled by using a self-extinguishing element such as a power MOSFET, a gate turn-off thyristor, an insulated gate bipolar transistor, or the like.

  Next, a basic concept of the phase control sequence immediately after the start of power supply to the heater lamp 2 in the present embodiment will be described with reference to FIG.

  FIG. 5 (a) illustrates the concept of the phase control sequence for soft start in the present embodiment, and FIG. 5 (b) illustrates the concept of the conventional phase control sequence. In both figures, the voltage application waveform of the heater lamp 2 during the conduction period of the switching element in which phase control is performed is approximated by a square wave. As described above, since it is assumed that the circuit of the heater device 1 is composed of only the resistance component, the waveform of the heater current is also a square wave having the same phase.

  Conventionally, as shown in FIG. 5B, energization is performed in which only a part of the half cycle is set to the conduction period by phase control every half cycle of the power supply voltage. In this case, the current flowing through the heater lamp 2 has a period of flowing at the positive voltage and a period of flowing at the negative voltage once, and the cycle is a distorted waveform equal to the cycle of the power supply voltage. On the other hand, in the present embodiment, as shown in FIG. 5A, the unit period is the sum of the first period in which phase control is performed and the second period in which no energization is performed. Is n times the half cycle of the power supply voltage (n is an integer of 3 or more) so as to be larger than the cycle of the power supply voltage. Since n = 4 in the figure, one conduction period is set to be twice that in the case of FIG. 5B, and both have the same amount of power in an integral multiple of the unit period. . The unit period is repeated a predetermined number of times at least until the period during which the inrush current to be suppressed flows is completed. In the figure, the first period is one period of the power supply voltage, and only a part of the half period is set as a conduction period by phase control every half cycle. Then, the bidirectional thyristor 3 is kept cut off with the next one cycle of the power supply voltage as a blank cycle. In this case, the current flowing through the heater lamp 2 has a period of flowing in the positive voltage and a period of flowing in the negative voltage once in the first period, and the cycle is four times the half cycle of the power supply voltage. That is, the distortion waveform is equal to twice the period. Note that the first period and the second period may be reversed in the context, and as a whole, the period may be n times the half period of the power supply voltage (n is an integer of 3 or more). .

  Next, FIG. 6 shows the calculation result of the square of the current amplitude of each frequency (the square of the spectral intensity) by the energization of FIGS. 5 (a) and 5 (b). In both cases, the number of samples of the current value was set to 512 per cycle of the power supply voltage, and the square of the current amplitude for each frequency was calculated by fast Fourier transform on the current waveform of 8 cycles (4096 samples). Regarding the frequency, 60 Hz, which is the frequency of the power supply voltage, is 8th order, and the first to 2048th order (220 kHz) is calculated. Since it is assumed that the applied voltage waveform and the current waveform of the heater lamp 2 during the conduction period are square waves having the same phase, the sum of all the orders of the square of the current amplitude is shown in FIGS. 5 (a) and 5 (b). The power supply voltage is proportional to the amount of power in eight cycles. In this respect, a similar result can be obtained even if fast Fourier transform is performed on the voltage waveform of FIG. If the sum of the squares of the first to 2048th order current amplitudes is made equal between the present embodiment and the prior art, that is, if the amount of power in the eight cycles is made equal between the prior art and the present embodiment, the 1024th to 2048th orders. The sum of the squares of the current amplitudes of the current embodiment is ½ that of the prior art. In FIG. 5A, since the unit period is twice the period of the power supply voltage, a spectrum of an integral multiple of 30 Hz is shown in FIG. 6, and the higher-order current intensity is reduced accordingly. . That is, the conventional energy on the high frequency side has moved to the low frequency side in the present embodiment. Thus, by making the energization cycle to the heater lamp 2 longer than the cycle of the power supply voltage, the frequency of the fundamental wave is lowered, the higher-order current components are reduced, and conductive noise and radioactive noise can be reduced. In the above example, a square wave is assumed for both the voltage and current in order to easily confirm the effect. However, as the frequency distribution, a similar distribution can be considered for waveforms other than the square wave, and noise reduction can be expected.

  Therefore, a phase control sequence for soft start immediately after the start of power supply to the heater lamp 2 was performed with the waveform shown in FIG. At the same time, the conventional phase control sequence is shown in FIG.

  1A and 1B, the frequency of the power supply voltage is 50 Hz. In FIG. 1B, the control angle (2π / 0.02 [s]) × t3 [s] and the control angle (2π / 0. 02 [s]) × t4 [s] (t4 = t3 + 0.01 [s]) is performed for each cycle phase control of the power supply voltage, whereas in FIG. 1A, the control angle (2π / 0.02 [ s]) × t1 [s] and control angle (2π / 0.02 [s]) × t2 [s] (t2 = t1 + 0.01 [s]), phase control is performed once every two cycles of the power supply voltage. One cycle is a blank cycle. In the unit period of FIG. 1A, one cycle of the power supply voltage for performing phase control corresponds to the first period, and the blank cycle corresponds to the second period.

  2A is a fast Fourier transform result of the current flowing as a result of FIG. 1A, and FIG. 2B is a fast Fourier transform result of the current flowing as a result of FIG. 1B. In FIG. 2A, since the unit period is set to twice the cycle of the power supply voltage, an order of an integral multiple of 25 Hz, which is a half of 50 Hz, is also observed as a clear peak.

  3 (a) and 3 (b) are graphs showing the results of comparing the current value of the order of an integral multiple of 50 Hz with the upper limit of the standard value with the harmonic current based on FIGS. 2 (a) and 2 (b). It is. In the second and higher orders, the current value in FIG. 3A is suppressed to be smaller than that in FIG. 3B, but a large reduction is seen particularly in even harmonics. Further, at higher orders not shown in the graphs of FIGS. 3A and 3B, the current value according to the present embodiment is suppressed to be smaller than that of the prior art. Thus, it has been found that it is possible to reduce conductive noise and radioactive noise immediately after the start of power supply to the heater lamp 2. The time until the inrush current to be suppressed ends is energized to the heater lamp 2 in the above-described phase control sequence, and thereafter, the zero cross control is applied to trigger the bidirectional thyristor 3 at each zero cross point of the power supply voltage. The temperature control of the heater lamp 2 is started.

  In FIG. 1A, the phase control is performed at the control angle described above in the first period. However, the present invention is not limited to this, and an effect of reducing the harmonic current can be obtained at an arbitrary control angle. Unlike the above example, even when the current of the heater lamp 2 is shifted from the phase of the power supply voltage, the effect of reducing the harmonic current can be obtained. Therefore, the first period and the second period are not necessarily integral multiples of a half cycle of the power supply voltage. It is only necessary that the cycle of the entire unit period is n times the half cycle of the power supply voltage (n is an integer of 3 or more). Even when the current waveform is not similar to the waveform of the voltage applied to the heater lamp 2, the effect of reducing the harmonic current can be obtained. As described above, the energization cycle of the heater lamp 2 is longer than the cycle of the power supply voltage, so that the fundamental wave frequency is lowered and the higher-order current components are reduced, thereby reducing conductive noise and radioactive noise. Become. In addition, the phase control sequence is simplified because only the unit period needs to be repeated. As described above, it is possible to realize a heater device that can reduce a high-frequency component caused by suppressing an inrush current by a simple phase control sequence.

  Further, in FIG. 3A, in the first period, the positive half cycle and the negative half cycle of the power supply voltage are conducted once each, but not limited to this, The effect is also obtained when conducting with biased polarity. However, as shown in FIG. 3A, when the average including the direction of the current in the positive half cycle and the negative half cycle becomes zero, the direct current component of the current flowing through the heater lamp 2 becomes zero. Therefore, in a single-phase three-wire generally used as an AC power supply for an electric device that is fed by a low-voltage indoor wiring such as a copying machine, a one-way wiring formed by a neutral wire and one of two active wires is used. Since the voltage drop due to the direct current of the heater current that flows can be prevented, the voltage drop unbalance can be avoided as much as possible in the entire single-phase three-wire. Even if the direct current component is not reduced to zero, if the phase control is performed so that the direct current component becomes small, the unbalance of the voltage drop can be alleviated over the entire single-phase three wires. Accordingly, in order to obtain this effect, it is advantageous that the first period has the same number of times as the positive polarity period and the negative polarity period of the current when the heater lamp 2 is energized. In the example of FIG. 3A, this is defined as one cycle of the power supply voltage in the first period, and the heater lamp 2 is energized once each in the positive half cycle and the negative half cycle of the power supply voltage. It is realized by doing.

  In addition, if the zero cross control is performed with respect to the energization to the heater lamp 2 after repeating the unit period a predetermined number of times, the zero cross control hardly generates a high frequency component of the current, and thus noise can be further reduced. From the start of energization to the steady operation can be performed with the same switching element for phase control.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for heater devices in general, and particularly for heater devices that are energized with a commercial frequency power source.

(A) shows embodiment of this invention and is a wave form diagram which shows a phase control sequence, (b) is a wave form diagram which shows the conventional phase control sequence. (A) is a graph which shows the result of the fast Fourier transform of Fig.1 (a), (b) is a graph which shows the result of the fast Fourier transform of FIG.1 (b). (A) is a graph showing the magnitude of the harmonic current based on FIG. 2 (a) in comparison with the upper limit of the standard value, and (b) is a standard showing the magnitude of the harmonic current based on FIG. 2 (b). It is a graph shown by comparing with the upper limit of the value. It is a circuit diagram which shows the circuit of a heater apparatus. It is a wave form diagram which shows the fundamental view of the phase control sequence of electricity supply of this Embodiment. It is a graph which shows the result of the fast Fourier transform of FIG. It is a wave form diagram which shows a prior art and shows the phase control sequence of electricity supply.

Explanation of symbols

1 Heater device 2 Heater lamp 3 Bidirectional thyristor 5 AC power supply

Claims (4)

In a heater device that is fed from an AC power source and capable of phase control of energization,
The unit period can be the sum of the first period in which the phase control is performed and the second period in which the energization is not performed.
The heater device according to claim 1, wherein the unit period is n times a half cycle of the voltage of the AC power supply (n is an integer of 3 or more).   2. The heater device according to claim 1, wherein the first period includes a positive period and a negative period of the current during energization the same number of times.   The first period is one cycle of the voltage of the AC power supply, and the energization is performed once each in a positive half cycle and a negative half cycle of the voltage. The heater device according to 1.   4. The zero cross control according to claim 1, wherein after the unit period is repeated a predetermined number of times, a zero cross control is performed with respect to the energization using a zero cross point of the voltage of the AC power supply as a control angle. 5. Heater device.

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