JPH0980961A - Fixing device and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a flicker component by supplying power to a heater by the zero cross turning-on of inconsecutive driving pattern in accordance with a heater-on signal, and supplying a rated power by AC consecutive turning-on after a specified time. SOLUTION: A pulse generator 107 for discontinuous driving receives a zero cross pulse from a zero cross detecting circuit 105 detecting the timing of the zero cross of the voltage of a power source 1 and outputs only the zero cross pulse for the discontinuous driving of a specified pattern. A continuous/ discontinuous driving signal generating circuit 108 receives the on-signal of the heater 104 of a fixing device 100, generates a driving signal switching the continuous/discontinuous driving at the specified timing, and a selector 109 receives the driving signal so as to generate a pulse for driving an optical thyristor 102. The power is supplied on the heater 104 by the zero cross turning-on of the discontinuous driving pattern in accordance with the heater-on signal from an outside, and the rated power is supplied on the heater 104 by the AC continuous turning-in after the specified time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for controlling electric power supplied to a heater as a fixing heat source used in a copying machine or a printer, and an electrophotographic apparatus having such a fixing device. More specifically, the present invention relates to a fixing device and an electrophotographic device that consider flicker due to a voltage drop that occurs around the heater under the influence of a current flowing through the heater.

[0002]

2. Description of the Related Art Generally, in an electrophotographic image forming apparatus, an electric signal (image signal) corresponding to the density of image information (original image) of an original is converted into an electric signal (laser light) and the like. An electrostatic latent image is formed on the photoconductor drum by using it. Then, this electrostatic latent image is developed into a toner image and then transferred to a recording sheet, and the toner image on the recording sheet is heated by a heater of a fixing device to be fused and fixed.

As a heater (fixing heater) of such a fixing device, a heater such as a halogen lamp is used as a heat source. Then, such a fixing heater is built in the heat roller.

As a fixing heater of this kind, a fixing heater of several hundred W to 1,000 W is used in a small-sized image forming apparatus, and a fixing heater having a larger capacity is used in a case of performing image formation at high speed. It is used.

The number of heaters is one, or two to three.
There are various things such as books. Then, according to the heater ON signal generated according to the detection result of the temperature sensor arranged in the vicinity of the heat roller, ON / OFF control of power supply to the fixing heater is performed to control so as to maintain a constant fixing temperature.

[0006]

In this type of fixing device, a large rush current flows to the fixing heater at the moment when the power supply is switched from off to on.

This situation will be described with reference to FIG. FIG. 13A shows a voltage waveform of the commercial power supply (AC100V). The heater ON signal is turned ON at a certain timing (FIG. 13B), and AC 100V is supplied from the commercial power supply to the halogen heater.

The resistance value of the halogen heater to which no current has been supplied until then is in an extremely low state, which is generally about 1/10 of that of red heat. Therefore, since the halogen heater starts to flow to the low resistance value at the same time as the power is supplied, the inrush current I ′ flows (FIG. 13C).
Then, as the resistance value increases to a steady value, the heater current decreases to I and converges. For example, assuming that the resistance value of the halogen heater in the OFF state is 1/10 of that in the red heat state, and the heater ON signal is in the ON state when the voltage of the commercial power source is high, the current I ′ is about ten times as instantaneous. = 10I will flow.

When such an inrush current I'is generated, a voltage drop (V1) occurs due to the electrical resistance (impedance) around the outlet of a commercial power source which supplies power to the image forming apparatus or indoor wiring. After that, when the heater current converges on I, the power supply voltage also recovers to some extent.

This situation will be described with reference to FIG. 14 showing a waveform of the peak value of the voltage. Here, the heater is turned on at time t1, an inrush current is generated, and a large voltage drop is instantaneously generated. After that, the voltage drop converges to a small value (constant value). Then, at time t2, the heater is turned off and the voltage returns to the original level.

In particular, the voltage drop caused by the above-mentioned inrush current is momentarily large, so that it may affect peripheral equipment and lighting equipment. For example, when the voltage supplied to the lighting device drops, a phenomenon called flicker in which the illuminance drops momentarily may occur.

In the above case, a large inrush current was flowing because the heater-on signal was turned on when the alternating voltage was high. Therefore, a zero-cross circuit is installed and the power supply voltage is 0V.
It is considered that the heater on signal is turned on at a certain timing. By doing so, the heater resistance increases to some extent before the voltage reaches the peak, so that the value of the inrush current can be suppressed to a small value.

When such a zero-cross control is performed, the heater-on signal becomes O at the timing shown in FIG. 13 (d).
N, the current flows as shown in FIG. in this case,
Since the power supply voltage is turned on at the timing when the peak value is 0 V, the rush current at the moment when it is turned on is smaller than that described above.

That is, when an experiment was conducted under a certain condition, the inrush current I ″ was about 5I, which was half the value of the inrush current described above. However, a large inrush current flows as compared with the steady current. There is no change in flicker due to voltage drop.

Therefore, in order to prevent an inrush current, a method of using two heaters and lighting them step by step one by one has been considered. However, a two-system control circuit for controlling the two heaters is required, and the roller diameter needs to be set so that the two heaters fit inside the fixing roller.
Therefore, there is a problem that the manufacturing cost increases. Also, it cannot be applied to a fixing roller originally designed for one heater.

It is also conceivable that a resistor or thermistor is provided in series with the heater, the heater and the resistor or thermistor are connected in series for a predetermined period of time after turning on, and then the resistor or the like is disconnected to conduct electricity. However, there is a problem of heat generated from resistance, etc., and loss due to resistance etc.
There are many problems, such as the problem of reliability of connection / disconnection circuit, and the problem of reliability of connection / disconnection circuit.

Therefore, as a means for preventing such an inrush current, a circuit called a soft starter circuit for controlling the conduction angle by using a two-way three-terminal thyristor may be used.

FIG. 15 is a time chart showing waveforms in this kind of soft starter circuit.
Shows the waveform of the power supply voltage, and FIG. 15B shows the waveform of the current whose conduction angle is controlled. Here, it is shown that there is no delay in the phase of the voltage and the current.

In FIG. 15B, the solid line portion is the period during which the two-way three-terminal thyristor is actually turned on. That is, the generation of inrush current is suppressed by gradually increasing the conduction angle (the period during which conduction is performed in the half cycle).

In the case of this soft starter circuit, FIG.
As is apparent from (b), the rising at the moment of conduction in each cycle has a sharp waveform. For this reason,
It radiates noise over a wide range of frequencies and interferes with the reception of televisions and radios. Therefore, in order to satisfy the noise regulation defined as the terminal noise standard, it is essential to provide a noise filter in the power supply line, which causes a problem of cost increase.

FIG. 16 is a block diagram showing the structure of the power supply line near the fixing device when the conduction angle control is performed by the thyristor. In FIG. 16, power is supplied from a commercial power source via the power plug 11.
The noise filter 20 prevents noise from the fixing device 40 from leaking to the commercial power source. Here, the filter 20 includes a common choke 21, an X-con 22,
It is composed of Y controllers 23 and 24. The DC power supply 30 is a power supply for supplying a predetermined DC voltage to each unit.

For example, in the structure of FIG. 16, a current of about 8 to 10 A flows to the fixing device 40 side, and the DC power source 30
A current of about 1 to 2 A flows on the side. Therefore, the noise filter 20 is also configured to withstand a large current of about 12 A and becomes a large-scale filter. In particular, the common choke becomes large in size, which leads to a large scale of the device.

Further, even if the noise standard is individually satisfied by superimposing the odd harmonic current generated in the DC power source 30 and the odd harmonic current generated from the fixing device 40, As a whole, the level exceeding the noise standard may be reached.

Here, the odd harmonic current generated in the DC power supply 30 will be briefly described. DC power supply 30
17 has a circuit configuration as shown in FIG. 17, and the current rectified by the diode bridge 31 is the electrolytic capacitor 3
2 is charged, switched by SW element 33, SW
The required voltage is output from the transformer 34.

In this case, since the electrolytic capacitor 32 is charged up to near the peak voltage V0, the current i from the commercial power source flows in pulses only when the voltage V approaches V0. Since this current waveform (see FIG. 18) has positive and negative symmetry, it can be seen that the Fourier spectrum has only odd-order harmonics.

For the above reasons, there is a problem that the common choke has to be increased. As described above, there is a trade-off relationship between the occurrence of flicker due to an inrush current and the cost of noise prevention, and it has been desired to realize an inexpensive device that does not generate flicker.

The present invention has been made in view of the above problems, and an object of the present invention is to use a halogen lamp heater as a heat source, which has a simple circuit structure without controlling the conduction angle. It is an object of the present invention to realize a fixing device or an electrophotographic device capable of suppressing the problems of flicker and noise.

[0028]

That is, the present invention, which is a means for solving the problems, and its preferable range are as described in the following (1).

(1) A first aspect of the present invention is a fixing device for supplying AC power to a heater as a fixing heat source according to a heater ON signal, and a zero-cross detection circuit for detecting a zero-cross timing of a phase of a power source, and a heater. Zero cross lighting is performed by an AC discontinuous pattern in which at least the ON timing and the OFF timing are less than the rated energization power for AC continuous lighting for a predetermined time from the ON timing, and after a predetermined time, AC full-wave continuous drive is performed. Therefore, a discontinuous drive signal and a full-wave continuous drive signal are generated, and a discontinuous drive pulse corresponding to the discontinuous drive signal and a full-wave drive pulse corresponding to the full-wave continuous drive signal at the detected zero-cross timing. And a drive pulse generating circuit for selectively generating and outputting By the scan and the full-wave driving pulse, a fixing device being characterized in that a switching means for supplying power by switching between continuous driving discontinuous drive to the heater.

In the first aspect of the invention, electric power is supplied to the heater by zero cross lighting of the discontinuous drive pattern by switching by the switching means in response to the heater ON signal from the outside. Due to this discontinuous driving pattern, less than the rated energizing power is supplied, and after a predetermined time, the rated power for AC continuous lighting is supplied to the heater.

As described above, by performing the zero-cross lighting of the AC discontinuous pattern at least for a predetermined time from the on timing, it is possible to reduce the flicker component of a predetermined frequency which is easily felt by humans. Further, since the zero cross control is performed instead of the conduction angle control, switching noise is hardly generated.

(2) In the first invention of (1) above,
As an AC discontinuity pattern by the discontinuous drive pulse generated by the drive pulse generation circuit, energizing only half cycle of AC 1 cycle, energizing only 1 or 2 half cycles of AC 1.5 cycle, of AC 2 cycle Only 1 to 3 half cycles are energized, 1 to 4 half cycles are energized from 2.5 AC cycles, 1 to 5 half cycles are energized from 3 AC cycles, and 3 AC cycles are of the same polarity In order to reduce flicker, it is preferable that the pattern is one in which energization is performed only for two half cycles.

By driving with such an AC discontinuous pattern, the flicker frequency is 50 Hz and 33 H.
z, 25 Hz, 20 Hz, 16.6 Hz, and it is possible to reduce the flicker component of 8.8 Hz, which is easily felt by humans.

(3) Further, in the first invention shown in (1), it is preferable to use a heater having a color temperature of 2600 ° k or less as a fixing heat source in order to reduce flicker. When a heater having a color temperature of 2600 ° k or less is used as described above, even when the color temperature is higher than 2600 ° k, even when the number of W is the same, it is turned off (at low temperature) and turned on (at high temperature). ) And the resistance ratio becomes smaller. As a result, the inrush current is reduced, which leads to a reduction in flicker.

(4) A second aspect of the present invention is an electrophotographic apparatus for supplying AC power to a heater as a fixing heat source according to a heater ON signal, wherein a DC power source section having a non-sinusoidal input current waveform and a heater. Switching means for supplying electric power to the heater so as to perform zero-cross lighting by an AC discontinuous pattern in which a predetermined time from at least the on timing and the off timing of the on timing and the off timing is less than the rated energizing power by the alternating current continuous lighting. An electrophotographic apparatus comprising:

In the second aspect of the invention, electric power is supplied to the heater by zero cross lighting of the AC discontinuous pattern by switching by the switching means in response to the heater ON signal from the outside. This AC discontinuous pattern supplies less power than the rated energizing power, and after a predetermined time, the rated power for AC continuous lighting is supplied to the heater.

As described above, when the zero-cross lighting of the AC discontinuous pattern is performed at least for a predetermined time from the on timing, it is possible to reduce the flicker component of a predetermined frequency which is easily felt by humans. Further, since the zero cross control is performed instead of the conduction angle control, switching noise is hardly generated.

(5) Further, in the second aspect of the invention described in (4), it is preferable that the AC discontinuous pattern of the switching means is a half-wave drive pattern of constant polarity in order to reduce flicker and noise. .

By the AC half-wave driving in this way, the flicker frequency becomes 50 Hz, which is easy for humans to perceive.
The flicker component of 8 Hz can be reduced. In addition, the harmonics contained in the current that flows during AC half-wave driving are
Since it is an even-numbered harmonic, the order is different from the odd-numbered harmonic of the DC power supply unit. Therefore, even if each harmonic has the maximum value of the noise standard, it is allowed.

(6) Further, in the second invention shown in (5), the constant-wave half-wave drive pattern of the switching means is: ON in half cycle of one AC cycle, half cycle of two AC cycles In order to reduce flicker and noise, it is preferable to have a pattern in which any one of the following is repeated, that is, ON in half cycle of three AC cycles, and two half cycles of the same polarity in three AC cycles.

By performing the AC half-wave drive in this way, the flicker frequencies are 50 Hz, 25 Hz, 16.6.
Since the frequency becomes Hz, it is possible to reduce the flicker component of 8.8 Hz which is easily felt by humans.

Further, since the harmonics contained in the current flowing during AC half-wave driving are even-numbered harmonics, the order is different from the odd-numbered harmonics of the DC power supply section. Therefore, even if each harmonic has the maximum value of the noise standard, it is allowed.

(7) Further, in the second invention shown in (4), it is preferable to use a heater having a color temperature of 2600 ° k or less as a fixing heat source for reducing flicker. When a heater having a color temperature of 2600 ° k or less is used as described above, even when the color temperature is higher than 2600 ° k, even when the number of W is the same, it is turned off (at low temperature) and turned on (at high temperature). ) And the resistance ratio becomes smaller. As a result, the inrush current is reduced, which leads to a reduction in flicker.

(8) A third aspect of the present invention is an electrophotographic apparatus for supplying AC power from a commercial power source to a heater in accordance with a heater ON signal, and a switching regulator as a DC power source section, and ON timing and OFF timing of the heater. And a switching means for supplying power to the heater so as to perform zero-cross lighting by an AC discontinuous pattern such that the power is less than the rated energizing power by AC continuous lighting for at least a predetermined time from the on timing.
The electrophotographic apparatus is characterized in that a common choke for reducing noise is provided only on the side of a line flowing from a commercial power source to the switching regulator.

In the third aspect of the invention, the electric power is supplied to the heater by the switching of the switching means in response to the heater ON signal from the outside by the zero cross lighting of the AC discontinuous pattern. This AC discontinuous pattern supplies less power than the rated energizing power, and after a predetermined time, the rated power for AC continuous lighting is supplied to the heater. In this way, if the zero-cross lighting of the AC discontinuous pattern is performed for at least a predetermined time from the on timing,
It is possible to reduce the flicker component of a predetermined frequency that is easily felt by humans. Further, since the zero cross control is performed instead of the conduction angle control, switching noise is hardly generated. Therefore, the common choke for noise reduction is sufficient only on the DC power supply side. Therefore, the current flowing through the common choke is reduced, and a small choke having a small wire diameter is sufficient. This makes it possible to reduce the size of the device.

(9) In the third invention of (8) above,
As the AC discontinuous pattern of the switching means, energizing only half cycle of AC 1 cycle, energizing only one or two half cycles of AC 1.5 cycle, energizing only 1 to 3 half cycles of AC 2 cycle , Energizing only 1 to 4 half cycles of AC 2.5 cycles, energizing only 1 to 5 half cycles of AC 3 cycles, energizing only two half cycles of the same polarity of AC 3 cycles It is preferable that the pattern is repeated to reduce flicker.

By driving with such an AC discontinuous pattern, the flicker frequency is 50 Hz and 33 H.
z, 25 Hz, 20 Hz, 16.6 Hz, and it is possible to reduce the flicker component of 8.8 Hz, which is easily felt by humans.

Note that modifications other than these lighting patterns are possible. That is, there are various patterns in which ON and OFF are combined so that the power consumption is lower than that in continuous lighting. It does not matter if the pattern has no periodicity. However, the larger the cycle, the closer to 8.8 Hz the human feels, and the smaller the effect.

(10) A fourth aspect of the present invention is a fixing heat source,
A fixing device comprising a halogen lamp of 500 W or more and having a color temperature of 2200 ° k or less, and a power supply unit for supplying AC power to the heater according to a heater ON signal. .

As in the fourth aspect of the invention, the color temperature is 220.
If it is 0 ° k, flicker can be suppressed sufficiently small even with a single halogen lamp heater of 500 W or more.

[0051]

Embodiments of the present invention will be described below in detail with reference to the drawings. <Structure of Fixing Device> FIG. 1 shows a schematic structure of a fixing device 100 according to an embodiment of the present invention. Further, FIG. 2 shows a state of connection around the fixing device 100.

In these FIGS. 1 and 2, the power source 1 is a source of power for supplying electric power to the fixing device. In FIG. 1, a case where an alternating current (50 Hz or 60 Hz) commercial power source is used as it is is shown. There is. In addition to the commercial power supply,
It may be a power source such as various private power generators having similar frequencies.

The optical thyristor 102 is a thyristor that is turned on by the emitted light, and triggers a two-way three-terminal thyristor 103 described later. 2 directions 3
The terminal thyristor 103 is a switching element which is triggered by the optical thyristor 102 to switch between discontinuous driving and continuous driving.

The heater 104 is a halogen heater of the fixing device, and the current is controlled by the two-direction three-terminal thyristor 103. The zero-cross detection circuit 105 is a circuit that detects the timing of the zero-cross of the voltage of the power supply 1, and outputs a pulse (zero-cross pulse) at the timing of the zero-cross.

The discontinuous drive pulse generation circuit 107 receives the zero cross pulse from the zero cross detection circuit 105, and outputs only the pulse of the zero cross timing of the predetermined pattern (discontinuous drive zero cross pulse) for the discontinuous drive. The continuous / discontinuous drive signal generation circuit 108 receives the heater-on signal and switches the continuous / discontinuous drive at a predetermined timing (continuous drive signal and discontinuous drive signal: or continuous / discontinuous drive signal). Is generated, and its output is supplied to the selector 109. The selector 109 receives the zero cross pulse, the zero cross pulse for discontinuous drive, and the continuous / discontinuous drive signal,
A pulse (driving pulse) for driving the optical thyristor 102 is generated.

Incidentally, the discontinuous drive pulse generation circuit 107,
Continuous / discontinuous drive signal generation circuit 108, selector 109
Will be collectively referred to as a drive pulse generation circuit 106. The light emitting section 110 receives the drive pulse and generates light for driving the optical thyristor.
It is provided in the vicinity of the light receiving portion inside.

Further, the drive pulse generating circuit 106, the light emitting portion 110, the optical thyristor and the two-direction three-terminal thyristor 10
3 constitutes the switching means 101. <Specific Example of Discontinuous Driving> The present invention is characterized by performing zero-cross lighting of the discontinuous driving pattern at least during a predetermined time from the on timing in order to reduce flicker. Therefore, a specific example of this discontinuous drive pattern will be described with reference to the drawings.

FIG. 3 shows a drive pattern in which ON / OFF is repeated in 1.5 cycles. In FIG. 3A, 0.5 cycle ON and 1 cycle OFF are repeated, and FIG. 3B shows 1 cycle ON, 0. Repeated 5 cycles off.

FIG. 4 shows a drive pattern in which ON / OFF is repeated in two cycles. In FIG. 4A, 0.5 cycle ON and 1.5 cycle OFF are repeated, and in FIG. 4B, 1 cycle ON and 1 cycle. Cycle off is repeated, and in FIG. 4C, 1.5 cycle on and 0.5 cycle off are repeated.

FIG. 5 shows a drive pattern in which ON / OFF is repeated in 2.5 cycles. In FIG. 5A, 0.5 cycle ON and 2 cycle OFF are repeated, and FIG. 5B shows 1 cycle ON, 1 cycle. .5 cycles off repeatedly, as shown in FIG.
Shows that 1.5 cycles are turned on and 1 cycle is turned off repeatedly, and FIG. 5 (d) shows 2 cycles turned on and 0.5 cycles turned off.

FIG. 6 shows a drive pattern in which ON / OFF is repeated in three cycles. In FIG. 6A, 0.5 cycle ON and 2.5 cycle OFF are repeated, and FIG. 6B shows 1 cycle ON, 2 cycles. Cycle off is repeated, and FIG. 6 (c) shows 1.5 cycle on and 1.5 cycle off.
In FIG. 6D, 2 cycles are turned on and 1 cycle is turned off, and in FIG. 6E, 2.5 cycles are turned on and 0.5 cycles are turned off.

FIG. 7 shows an example of half-wave driving as the discontinuous driving. FIG. 7A repeatedly turns on and off 0.5 cycles, and FIG. 7B shows 0.5 cycles. Repeated on and 1.5 cycles off, and FIG.
Repeated 5 cycles on and 2.5 cycles off, as shown in FIG.
(D) shows that only two half waves of three cycles are turned on.

<Measurement of Flicker> FIG. 8 shows how flicker is measured. Regarding this flicker measurement, IEC868
It is stipulated that the following be performed. The RMS value of the power supply voltage is calculated every half cycle. Pass through a band pass filter of 0.05 Hz to 35 Hz. Pass through a bandpass filter with a center frequency of 8.8 Hz. Square detection is performed and normalized with the initial power supply voltage to obtain an instantaneous flicker S (t).

By doing so, the flicker of the voltage fluctuation component centered on the sensitivity of 8.8 Hz included in the power supply voltage can be obtained. It should be noted that this 8.8 Hz is defined as the frequency most easily felt by humans.

The cumulative probability function is obtained from the data obtained by measuring this S (t) for a predetermined time. FIG. 9 is a graph of a cumulative probability function in which S (t) is plotted on the horizontal axis and the cumulative appearance frequency of S (t) is plotted on the vertical axis in%.

From this function, the short-term flicker P is calculated by the following equation.
st is required. P (50S) = {P (30) + P (50) + P (80)} / 3 P (10S) = {P (6) + P (8) + P (10) + P (13) + P (1
7)} / 5 P (3S) = {P (2.2) + P (3) + P (4)} / 3 P (1S) = {P (0.7) + P (1) + P (1.5)} / 3 Pst = ( 0.0314 P (0.1) +0.0525 P (1S) +0.0657 P (3S)
+ 0.28P (10S) + 0.08P (50S)) ^1/2 where P (n) is the value of S (t) when the probability is n%.

The limit value for the short-time flicker value Pst thus obtained is defined in IEC1000-3-3, and Pst ≦ 1.0.

<Operation of Fixing Device> The operation of the fixing device configured as described above will be described below with reference to the time chart of FIG.

When the heater-on signal is turned on as the detection result of the temperature detection circuit (not shown), the continuous / discontinuous drive signal generation circuit 108 causes the discontinuous drive signal immediately after the heater is turned on, and after the AC discontinuous drive for a fixed time, the continuous drive signal. Drive signal, generates a discontinuous drive signal when turned off. The discontinuous drive signal may be generated at least immediately after the heater is turned on. Therefore, it is optional to generate a discontinuous drive signal when it is off.

FIG. 10A shows a heater ON signal. The discontinuous drive signal is turned ON immediately after it is turned ON (FIG. 10B), and the continuous drive signal is turned ON after a certain period of time. (FIG. 10C). Then, immediately after the heater on signal is turned off, the discontinuous drive signal is turned on again for a certain time (FIG. 10 (b)).

First, consider a certain period immediately after the heater ON signal is turned on. The selector 109 which receives the discontinuous drive signal as described above supplies the discontinuous drive zero-cross pulse as a drive pulse to the light emitting unit 110 during the period in which the discontinuous drive signal is received. Therefore, the optical thyristor that receives the light from the light emitting unit 110 is triggered for a predetermined period of discontinuity to be in a conductive state, and the two-way three-terminal thyristor 103 is also in a conductive state for a predetermined period of discontinuous (discontinuous rectification state). )become.

Either the discontinuous drive signal or the zero-cross pulse for discontinuous drive in this case is shown in FIGS.
Any signal or pulse that realizes any one of the driving patterns may be used.

Here, the case of half-wave driving shown in FIG. 7A will be described as an example. Therefore, the waveform of the current flowing through the two-way three-terminal thyristor 103 in the discontinuous rectification state is as shown in FIG. 10D during the discontinuous drive period. That is, since the resistance value of the heater 104 in the off state is low, the current value is large at the moment when the current starts flowing, and the current value gradually decreases. In this case, the peak value becomes the same value as in the case of the conventional zero-cross control shown in FIG.

Further, FIG. 10 (e) shows the state of the voltage drop, and in this case as well, it fluctuates with the power supply frequency, and the peak value is the same as in the case of the conventional zero-cross control. However, it is generally known that the characteristics of the human eye are highly sensitive to fluctuations around 8.8 Hz, and that sensitivity decreases below and above that. Therefore, the power supply frequency fluctuation portion in FIG. 10E is not felt, and it actually feels like a broken line.

That is, at the moment when the heater-on signal is turned on, a flicker equivalent to V1 is conventionally felt, but V2 is obtained by using the fixing device of this embodiment.
Only flicker of about (= 1/2 × V1) is felt.

Then, the time when the discontinuously rectified current value becomes about twice the steady current value is measured in advance, and the continuous drive signal is turned on at this timing. Then, the selector 109 receiving the continuous drive signal supplies the continuous drive zero-cross pulse to the light emitting unit 110 as a drive pulse. Therefore, the optical thyristor receiving the light from the light emitting unit 110 is triggered during the full wave period and becomes conductive, and the two directions 3
The terminal thyristor 103 also becomes conductive (full-wave rectification state) in both alternating current periods (FIG. 10D).

Immediately after the heater on signal is turned off, the continuous drive signal is turned off, and at the same time, the discontinuous drive signal is turned on (FIGS. 10 (c) and 10 (b)), which is kept on for a certain period of time.

In this manner, the selector 109 which receives the discontinuous drive signal again uses the zero-cross pulse for discontinuous drive as the drive pulse during the period when the discontinuous drive signal is received.
Supply to 10. Therefore, the optical thyristor that receives the light from the light emitting unit 110 is triggered for a predetermined period of discontinuity to be in a conductive state, and the two-way three-terminal thyristor 103 is also in a conductive state for a predetermined period of discontinuous (discontinuous rectification state). )become.

Therefore, the waveform of the current flowing through the two-way three-terminal thyristor 103 in the discontinuous rectification state is as shown in FIG. 10D during the discontinuous drive period. Therefore, the fluctuation portion V3 of the power supply frequency in FIG. 10 (e) is not felt, and actually, it is felt as a half fluctuation of 1/2 · V3 as indicated by the broken line.

That is, at the moment when the heater-on signal is turned off, conventionally, a flicker equivalent to V3 is felt, but by using the fixing device of this embodiment,
A half flicker of about ½ × V3 is felt in two times, one when the discontinuous drive signal is turned on and the other when it is turned off.

In the above embodiment, the heater is turned on.
Although the discontinuous driving is performed at both the timing of turning on N and the timing of turning off, a great effect can be obtained by performing the discontinuous driving at least when turning on the heater.

When discontinuous driving is performed both when the heater is turned on and when the heater is turned off, the discontinuous driving patterns may be the same or different.

Furthermore, in the above embodiment, two directions and three directions are used.
The terminal thyristor and the optical thyristor are used to switch between full-wave / half-wave, but the circuit is constructed using various switching elements that can switch full-wave / half-wave at the zero-cross timing according to the heater ON signal. It can be transformed.

As described above, by performing the zero-cross lighting of the AC discontinuous pattern for at least the predetermined time from the on timing, it is possible to reduce the flicker component of the predetermined frequency which is easily felt by humans. Further, since the zero cross control is performed instead of the conduction angle control, switching noise is hardly generated.

Therefore, as shown in FIG. 2, the common choke 21 for noise reduction is sufficient only on the DC power supply 30 side. Therefore, the current flowing through the common choke 21 is reduced, and a small choke having a small wire diameter is sufficient. This makes it possible to reduce the size of the device.

In the above embodiment, continuous /
Although the discontinuous pattern is generated independently and switched by the selector, the heater is turned on / off by the pulse generation circuit itself.
You may make it generate | occur | produce a continuous / discontinuous pattern of predetermined time synchronizing with an OFF signal.

[0087]

EXAMPLES The results of measuring the state of flicker change according to the above-described structure and drive pattern are shown below.

<Experimental Example 1: Driving Pattern and Flicker> Here, in Experimental Example 1, the results of the lighting cycle, the lighting timing, the repetition frequency, and the short-time flicker value Pst are shown in Table 1 below.

[0089]

[Table 1]

<Comparative Example 1: Driving pattern and flicker> For comparison, Table 2 below shows the result obtained as a comparative example for lighting cycles larger than three cycles.

[0091]

[Table 2]

<Evaluation of Experimental Example 1 and Comparative Example 1> As a result of the above, the short-time flicker value Pst is less than 1 in the lighting cycle up to 3 cycles as shown as a concrete example in FIGS. Good results were obtained. In these figures, the hatched parts are lit (ON)
Is shown.

<Experimental Example 2: Heater color temperature and flicker>
The inventor of the present application also paid attention to the relationship between the color temperature of the halogen lamp as the heater and the flicker, and found the condition capable of suppressing the flicker. 11 and 1
2 shows an example of the experiment.

Here, a 750 W lamp is used, and lighting is repeated for 30 seconds on and 30 seconds off. As is apparent from FIGS. 11 and 12, by using a heater having a color temperature of 2200 ° k, it is possible to use a heater that is normally used.
It is possible to satisfy the flicker standard even with one lamp of 00W to 1000W. That is, the color temperature is 220
When a heater of 0 ° k or less is used, the resistance ratio between when the lamp is turned off (at low temperature) and when it is turned on (at high temperature) is the same, even if the color temperature is higher than 2200 ° k. Becomes smaller. As a result, the inrush current is reduced, which leads to a reduction in flicker. If the color temperature is the same, W
The smaller the number, the better the result.

Even if the conditions other than those of Experimental Example 2 are satisfied,
It was also confirmed by experiments that good results can be obtained with a lamp having a temperature of 2600 ° k or less within the range of the conditions of Experimental Example 1 described above.

<Experimental Example 3: Driving pattern and noise> It is determined by Fourier transform that the harmonics contained in the current flowing in the case of the half-wave driving shown in FIG. 7 are even harmonics. Therefore, the direct current (DC) power supply unit 30 of FIG.
18 has a different order from the odd-numbered harmonics generated in the configuration shown in FIG. Therefore, it was also confirmed that each harmonic is allowed without exceeding the standard value even if it is the maximum value of the noise standard.

[0097]

As described above in detail, according to the invention of the fixing device or the electrophotographic device which performs the zero-cross lighting of the AC discontinuous pattern at least during the predetermined time from the on-timing, the human sense of the predetermined frequency feels. It is possible to reduce the easy flicker component, and the switching noise is hardly generated because the zero cross control is performed instead of the conduction angle control.

Flicker can also be reduced by considering the color temperature of the fixing heat source.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a configuration of a fixing device according to an exemplary embodiment of the present invention.

FIG. 2 is a configuration diagram showing an overall configuration of a fixing device according to an exemplary embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a lighting pattern according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a lighting pattern according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a lighting pattern according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a lighting pattern according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a lighting pattern according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing how flicker is measured.

FIG. 9 is a graph of a cumulative probability function showing how flicker is measured.

FIG. 10 is a time chart showing the operation of the fixing device according to the exemplary embodiment of the present invention.

FIG. 11 is a characteristic diagram showing experimental results of an example of the present invention.

FIG. 12 is a characteristic diagram showing experimental results of an example of the present invention.

FIG. 13 is a time chart showing a state of an inrush current in the operation of the conventional fixing device.

FIG. 14 is a time chart showing how the power supply voltage drops in the operation of the conventional fixing device.

FIG. 15 is a time chart showing voltage and current waveforms in a soft starter circuit using conduction angle control.

FIG. 16 is a configuration diagram showing an overall configuration of a conventional fixing device.

FIG. 17 is a configuration diagram showing an overall configuration of a conventional DC power supply.

FIG. 18 is a waveform diagram showing a current state of a DC power supply.

[Explanation of symbols]

 1 power supply (commercial power supply) 100 fixing device 102 optical thyristor 103 two-way three-terminal thyristor 104 heater 105 zero-cross detection circuit 106 drive pulse generation circuit 107 discontinuous drive pulse generation circuit 108 continuous / discontinuous drive signal generation circuit 109 selector 110 light emission Department

Claims (10)

[Claims] 1. A fixing device for supplying AC power to a heater as a fixing heat source according to a heater ON signal, comprising a zero-cross detection circuit for detecting a zero-cross timing of a phase of a power source, and a heater on-timing and off-timing. At least a predetermined time from the on timing, the zero crossing lighting is performed by the AC discontinuous pattern so that the power is less than the rated energizing power by the AC continuous lighting, and the AC full wave continuous drive is performed after the predetermined time. And a full-wave continuous drive signal are generated, and a discontinuous drive pulse according to the discontinuous drive signal and a full-wave drive pulse according to the full-wave continuous drive signal are selectively generated at the detected zero-cross timing. Drive pulse generator circuit that outputs the output pulse, and the discontinuous drive pulse and full-wave drive pulse from this drive pulse generator circuit. And a switching unit that supplies electric power to the heater by switching between discontinuous driving and continuous driving. 2. An alternating current discontinuity pattern formed by the discontinuous drive pulse generated by the drive pulse generating circuit is an alternating current 1
Energize only half of the cycles, energize only one or two half-cycles of AC 1.5 cycles, energize only half-cycles of 1 to 3 of AC 2 cycles,
Either energization of 1 to 4 half cycles of AC 2.5 cycles, energization of 1 to 5 half cycles of AC 3 cycles, or energization of only 2 half cycles of the same polarity of AC 3 cycles The fixing device according to claim 1, wherein the fixing device has a pattern in which 3. A color temperature of 2600 ° as the fixing heat source.
The fixing device according to claim 2, further comprising a heater of k or less. 4. An electrophotographic apparatus for supplying AC power to a heater as a fixing heat source in accordance with a heater ON signal, comprising a DC power supply section having an input current waveform of a non-sinusoidal wave, and heater ON timing and OFF timing. A switching means for supplying electric power to the heater so as to perform zero-cross lighting by an AC discontinuous pattern in which at least a predetermined time from the ON timing is less than the rated energizing power for AC continuous lighting. Electrophotographic device. 5. The electrophotographic apparatus according to claim 4, wherein the AC discontinuous pattern of the switching means is a half-wave drive pattern having a constant polarity. 6. A constant-polarity half-wave drive pattern of the switching means is turned on in a half cycle of AC 1 cycle, turned on in a half cycle of AC 2 cycle, turned ON in a half cycle of AC 3 cycle, and AC 3 cycle. The electrophotographic apparatus according to claim 5, wherein the electrophotographic apparatus has a pattern in which one of two half cycles of the same polarity is turned on. 7. A color temperature of 2600 ° as the fixing heat source.
7. The electrophotographic apparatus according to claim 6, further comprising a heater lamp of k or less. 8. An electrophotographic apparatus for supplying AC power from a commercial power source to a heater in accordance with a heater ON signal, wherein a switching regulator as a DC power source unit and a heater ON timing and OFF timing are predetermined from at least ON timing. The line side that flows from the commercial power source to the switching regulator is provided with a switching unit that supplies electric power to the heater so as to perform zero-cross lighting by an AC discontinuous pattern in which time is less than the rated energization power for AC continuous lighting. An electrophotographic device characterized in that a common choke for reducing noise is provided only on the front side. 9. The alternating discontinuity pattern of the switching means is such that energization of only one half cycle out of one AC cycle, energization of only one or two half cycles out of 1.5 AC cycles, and one or more of two AC cycles 3 Energize only the following half cycles, energize only 1 to 4 half cycles of AC 2.5 cycles, and energize 1 of 3 AC cycles
9. The electrophotographic apparatus according to claim 8, wherein the pattern has a pattern in which energization is performed only for half cycles of 5 or less and energization for only two half cycles of the same polarity among the three alternating current cycles. 10. A heater comprising a halogen lamp of 500 W or more as a fixing heat source and having a color temperature of 2200 ° k or less, and a power supply means for supplying AC power to the heater according to a heater ON signal. An electrophotographic device characterized in that