JPH096180A - Power control device and fixing device - Google Patents

Abstract

PURPOSE: To provide a power controller and a fixing device capable of preventing flickering, without complicating the device, even in the case of sampling in a comparatively short time and executing PWM feedback control. CONSTITUTION: The number of waves for turning on a heater is set (S1). After a counter for counting the number of the waves was reset (S2), a counter value and a forcible OFF specifying value (for instance, the third wave, the sixth wave, etc.) are compared (S4), during counting up (S3). At the time of no coincidence, it is judged whether the counter value exceeds the set number of the waves or not (S5). When the counter value does not exceed the set number of the waves, the heater is turned on (S6). However, when the counter value coincides with the forcible OFF specifying value, the set number of the waves is increased by one (S7) and then, the heater is turned off (S8). By such a way, when the heater is turned off, the set number of the waves is increased by one, so that the heater is intermittently turned on/off, while the number of the waves for turning on is maintained as set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control device for controlling power supplied to a fixing device of an image forming apparatus such as a copying machine, a facsimile, a laser beam printer or the like by controlling the wave number of a power supply. And a fixing device.

[0002]

2. Description of the Related Art Conventionally, a fixing device of an image forming apparatus such as a copying machine is generally provided with a heater which is a heating body, and a toner transferred onto a transfer material such as paper in an image forming portion is transferred to the transfer material by heating the heater. Melt and stick on top.

Therefore, in order to perform good fixing in such a fixing device, it is necessary to maintain the temperature of the heater at a predetermined temperature, and therefore a power control device for controlling the supply of electric power to the heater is provided. This power control device
For example, it is equipped with a triac as a switching means for turning on and off the commercial power supply, and further with a trigger means for asynchronously turning on and off the triac near the zero cross of the commercial power supply, and an ON duty of a trigger output signal generated by this trigger means is appropriately set. The so-called PWM control is performed to control the electric power by changing the value to. Thus, the wave number supplied to the heater is controlled to keep the temperature of the heater at the target temperature suitable for toner fixing.

FIG. 9 shows a PWM output pattern for controlling the electric power by changing the ON duty of the trigger output signal. In the figure, the ON / OFF is performed once within a predetermined time (140 msec), and the minimum duty width is set to 10 msec width. Then, levels 1 to 13 are provided, and the ON duty is lengthened according to the level to adjust the amount of electric power supplied to the heater.

In the above-mentioned conventional example, the control which synchronizes with the zero cross of the commercial power source is not particularly performed, but as another current control device, the zero cross of the commercial power source is detected.
It is also known that the power is controlled by performing so-called phase control, which determines the phase angle based on this detection.

[0006]

However, in the above power control device, for example, it may be difficult to satisfactorily control the temperature of the fixing device using a fixing film having a small heat capacity. A fixing device equipped with a fixing film is a device in which a heat-resistant film is endlessly configured as a fixing film, and a transfer material is nipped and conveyed between a heater arranged inside the fixing film and a pressure roller arranged outside. When the transfer material is inserted into the fixing nip portion between the fixing film and the pressure roller, the thermal energy of the heater is applied to the toner on the transfer material through the fixing film to melt the toner and transfer the material. It is fixed on top.
The characteristic of the fixing device using the fixing film is that the heat capacity of the heating body and the fixing film is set small (the resistance value is small) in order to quickly raise the temperature.
Therefore, in the conventional power control, the following phenomenon may occur in such a fixing device.

1) Since the capacity of the fixing device is small, it is necessary to sample the temperature state of the fixing device and perform PWM feedback control in a relatively short time (for example, about 7 Hz in the past). If the resistance value is low and the line impedance of the commercial power source connected to the fixing device is high, there is a possibility that a flicker which the human being can see with the PWM cycle (for example, about 7 Hz in the past) may occur.

2) If phase control is performed to improve the flicker level, it is necessary to add terminal noise countermeasures and zero-cross detection, which increases the number of parts and complicates the overall configuration.

Therefore, an object of the present invention is to provide a power control device and a fixing device capable of preventing flicker without complicating the device even when sampling and PWM feedback control are performed in a relatively short time. There is.

[0010]

According to the first invention of the present application, the above object is to provide a switching means for switching a conduction state of a commercial power source to a controlled object, and the switching means in the vicinity of a zero cross of the commercial power source. Drive it,
The commercial power supply includes a wave number control unit that energizes and stops energization of the controlled object in half-wave units, and a detection unit that detects a control result value of the controlled object, wherein the wave number control unit is the controlled object. According to the deviation amount between the control target value and the control result value, the number of energized waves in the half-wave unit within a predetermined period is determined, and the energization to the controlled object is set by the energized wave number. In the electric power control device, the wave number control means is set to stop energization in units of the half waves and intermittently energize within the predetermined period by the energization wave number determined as described above. It is achieved by

Further, according to the second invention of the present application,
In the first aspect of the present invention, the wave number control means is set to stop energization for each preset predetermined half wave from the start of energization in half wave units within a predetermined period. It is achieved by

Further, according to the third invention of the present application, in the above-mentioned first invention, the wave number control means is configured such that the wave number and the energization are performed within a unit period obtained by further dividing the predetermined period. Achieved by being set to determine the percentage of wavenumbers to stop.

According to the fourth invention of the present application,
The above-mentioned object is achieved in the third aspect of the present invention, in which the ratio of the wave number for energization and the wave number for stopping energization is variable.

Further, according to the fifth invention of the present application, the above-mentioned object is to provide a heating body which generates heat when energized, a heat-resistant film arranged so as to rub against the heating body, and the heat-resistance. A pressure roller arranged so as to be in pressure contact with the heating body via a film, a switching means for switching a conduction state of the commercial power source to the heating body, and driving the switching means in the vicinity of the zero cross of the commercial power source, The commercial power supply includes a wave number control means for energizing and stopping energization of the heating body in units of half waves, and a temperature detecting means for detecting the temperature of the heating body, wherein the wave number control means controls the heating body. Depending on the amount of deviation between the target temperature value and the temperature value detected by the temperature detecting means, the number of energized waves in half-wave units within a predetermined period is determined, and energization to the heating body is performed by the number of energized waves. Set to In the fixing device, the wave number control unit is set so as to stop energization in units of the half wave and intermittently energize within the predetermined period by the energization wave number determined as described above. It is achieved by

According to the sixth invention of the present application,
In the fifth aspect of the invention, the wave number control means is set so as to stop energization for each preset predetermined half wave from the start of energization in half wave units within a predetermined period. It is achieved by

Further, according to a seventh invention of the present application, in the fifth invention, the wave number control means sets the wave number and the energization for energizing in a unit period obtained by further dividing the predetermined period. Achieved by being set to determine the percentage of wavenumbers to stop.

According to the eighth invention of the present application,
The above-mentioned object is achieved in the seventh aspect of the present invention in that the ratio of the wave number for energizing and the wave number for stopping energizing is variable.

[0018]

According to the first invention of the present application, the energization of the controlled object is a half of the commercial power supply within a predetermined period according to the deviation amount between the control target value of the controlled object and the control result value by the detection means. The energization wave number for each wave is determined, and the energization is performed by the energization wave number. At this time, the energization is stopped for each half wave, and the energization within the predetermined period is performed by the energization wave number determined as described above. Is performed intermittently, the energization period for the controlled object is substantially increased, and flicker is prevented.

According to the second aspect of the present invention,
In the first aspect of the invention, since energization is stopped for each preset predetermined number of half waves from the start of energization in half-wave units within a predetermined period, there is no effect on the determined energization wave number, and there is no interruption. Realization of specific electricity.

Further, according to the third invention of the present application, in the above-mentioned first invention, the wave number control means sets the number of waves to be energized and the number of waves to stop energizing within a unit period obtained by further dividing the predetermined period. Since the ratio is determined, it does not affect the conduction wave number determined according to the deviation amount,
Realizes intermittent energization.

According to the fourth invention of the present application,
In the third aspect of the invention, since the ratio of the number of waves to be energized and the number of waves to stop the energization is variable, appropriate control is performed according to the frequency of the commercial power source or the determined number of energized waves.

Further, according to the fifth invention of the present application, the heating element is energized in a commercial manner within a predetermined period according to the deviation amount between the control target temperature value of the heating element and the temperature value detected by the detecting means. Determine the half-wave energization wave number of the power supply,
It is performed by the energization wave number, at which time energization is stopped in units of half waves, and energization within the predetermined period by the energization wave number determined as described above is performed intermittently. Also in the fixing device of the type, the energization period to the heating body is substantially increased, and flicker is prevented.

According to the sixth invention of the present application,
In the fifth aspect of the invention, since energization is stopped for each preset predetermined half-wave from the start of energization in half-wave units within a predetermined period, there is no effect on the determined energization wave number, and there is no interruption. Realization of specific electricity.

Further, according to the seventh invention of the present application, in the fifth invention, the wave number control means sets the number of waves to be energized and the number of waves to stop energizing within a unit period obtained by further dividing the predetermined period. Since the ratio is determined, it does not affect the conduction wave number determined according to the deviation amount,
Realizes intermittent energization.

According to the eighth invention of the present application,
In the seventh aspect of the invention, since the ratio of the number of waves to be energized and the number of waves to stop the energization is variable, appropriate control is performed according to the frequency of the commercial power source or the determined number of energized waves.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a system configuration diagram when a control device for a fixing device such as a copying machine is applied to the power control device as an example of the power control device according to the present invention.

In the figure, reference numeral 1 is a commercial power supply, and the voltage of the commercial power supply 1 is transformed by a transformer T1 to charge a hold capacitor C1 via a diode D1.
The voltage of the hold capacitor C1 is adapted to be input to the A / D input port of the CPU 3 which is the wave number control means.
1 of the commercial power supply 1 is monitored.

Further, the commercial power source 1 is also connected to a ceramic heater R3 which is a heating body of the fixing device 2, and when the gate of the triac Q2 which is a switching means is ON, the ceramic heater R3 is energized and the triac Q2 is turned on. When the gate of is off, ceramic heater R3
Stop supplying power to

ON / O of the gate of this triac Q2
The FF can be switched based on the level of the FSRD signal output from the CPU3.
The temperature information is input from the A / D port by the thermistor TH, which is a detecting means disposed near the ceramic heater R3, and the FSRD signal is switched to the H or L level based on the temperature information.

That is, when the temperature detected by the thermistor TH is lower than the set temperature, the FSRD signal is set to the H level to turn on the transistor Q1 constituting the switching means, and the collector output thereof also constitutes the switching means. Turn on Photo Triac PC1
By turning on N, the gate of TRIAC Q2 is turned on.
Then, the commercial power supply 1 is triggered at a timing near zero cross to start energizing the ceramic heater R3. on the other hand,
When the temperature detected by the thermistor TH is higher than the set temperature, the FSRD signal is set to the L level to turn off the transistor Q1 and the phototriac PC1 to turn off the gate of the triac Q2, and the zero crossing is performed. It is triggered at a timing near to stop the energization of the ceramic heater R3.

As described above, the CPU 3 controls the thermistor TH.
Thus, while monitoring the temperature state of the fixing device 2 by the ceramic heater R3, the temperature of the fixing device 2 is maintained at a predetermined set temperature.

However, when a film type fixing device as shown in FIG. 2 is used as the fixing device 2,
The following phenomenon may occur.

As shown in FIG. 2, this film-type fixing device is composed of a heat-resistant film which is endless and is used as a fixing film 8, which includes a fixing heater 9 having a ceramic heater R3, a driving roller 11 and a driven roller 12. The fixing film 8 is stretched, a pressure roller 10 is pressed against a fixing heater 9 through the fixing film 8, and a transfer material is nipped and conveyed at this nip portion, and the heat capacity of the fixing device is small. It has the characteristics of Therefore,
In such a fixing device, it is necessary to sample the temperature state of the fixing device and perform PWM feedback control in a relatively short time (for example, about 7 Hz in the past), and the resistance value of the heating element is small as in the above-described configuration. Moreover, when the line impedance of the commercial power source connected to the fixing device is high, the above PWM cycle (for example, 7 Hz in the past) is used.
There was a risk of flicker that could be viewed by humans.

Therefore, in the present embodiment, the above-mentioned CP
U3 also functions as a heater forced OFF control means,
Unconditionally FSRD regardless of the temperature of the thermistor TH
The flicker is prevented by setting the signal to the L level to turn off the heater and substantially shortening the PWM cycle.

FIG. 3 shows a timing chart for explaining the wave number control method in this embodiment. Here, a method of controlling every half wave is used, and one sampling period is set to 20 waves. Then, for example, from the temperature detection result of the thermistor TH, 11 waves out of 20 waves are turned on, and further, the third wave, the sixth wave, the ninth wave, the twelfth wave, and the fifteenth wave are
It is decided in advance that it will be forcibly turned off. Therefore, of the 20 waves in one sampling period, the FSRD signal is set to the H level except for the order in which the above-mentioned is forcibly determined to be OFF forcibly from the beginning, and a total of 11 waves are turned ON. All waves are at L level. By providing the wave forcibly turning off the heater in this way, that is, the substantial frequency is 33.33 Hz here. On the other hand, in the conventional control, in such a case, the first one wave continues to be turned on, so that the frequency becomes 5 Hz as shown in FIG.

Next, the control of this embodiment will be described with reference to the flow chart of FIG. First, since the wave number control is performed by monitoring the temperature of the thermistor, the wave number for turning on the heater is set (step S1), and the counter for counting the set wave number is reset (step S1).
2) While counting up (step S3), compare the counter value with the forced OFF designation value (step S3).
4) If they do not match, it is judged whether or not the counter value exceeds the set wave number (step S5). If not, the FSRD signal is set to H level and the heater is turned on (step S6). , Ceramic heater R3
Energize. However, when the counter value matches the forced OFF designation value, the set wave number is incremented by one (step S7), and then the FSRD signal is set to the L level to turn off the heater (step S8). When the heater is turned off in this way, the number of waves to be turned on is maintained as set by incrementing the set number of waves by one. Then, as described above, the FSRD signal H /
While switching the L level, the counter value and the set wave number are compared (step S5), and when the counter value exceeds the set wave number, the control ends.

As described above, according to the present invention, the flicker can be prevented even in the film type fixing device.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The description of the common points with the first embodiment will be omitted.

In the present embodiment, it is assumed that the waves in a fixed order are not turned off as in the first embodiment, but they are turned off periodically at a ratio of X waves to Y waves.

That is, as described in the first embodiment,
When presetting the third wave, sixth wave, ninth wave, ...
In this embodiment, by setting X to 3 and Y to 1 and turning off at a ratio of 1 to 3 waves, the same operation as in the first embodiment is performed.

Here, the case where X = 5 and Y = 2 will be described with reference to the timing chart of FIG. In this embodiment, the power is turned off at a rate of 2 out of 5 waves as shown in the figure.
Eventually, 11 of 20 waves were turned on. Since the sampling period is 20 waves, for example, 50
In the case of the power source of Hz, the frequency becomes 5 Hz by the normal wave number control, but in the control of the present embodiment, the power is turned on and off in the cycle of 50 ms.
Since it is F, it becomes substantially equivalent to 20 Hz.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. The description of the common points with the first embodiment will be omitted.

It is a block diagram showing the present embodiment. CPU
It is exactly the same as that of the first embodiment except that the wave number control mode setting means connected to is provided.

The above-mentioned wave number control mode setting means may be set externally as shown in FIG. 7 or may be set inside the CPU and set by the CPU depending on the situation.

The contents of this control will be described with reference to the flowchart of FIG. In this system, since the mode is set and input from the outside, the presence or absence of the mode instruction is first detected (step S10), and if there is no particular mode instruction,
Normal wave number control is performed (step S11). However, when the modes having the contents described in the first and second embodiments are set from the outside, the respective controls described above are similarly performed (steps S12 and S13).

[0047]

As described above, the first embodiment according to the present application is described.
According to the invention, the current control means such as the fixing device is provided with the control means for forcibly turning off the predetermined number of waves in the sampling cycle. After that, instead of continuing to turn off, turning off at regular or random intervals between the waves to be turned on makes it possible to substantially prevent flicker of the frequency visible to humans without increasing costs.

According to the first invention of the present application, the energization of the controlled object is a half of the commercial power supply within a predetermined period depending on the deviation amount between the control target value of the controlled object and the control result value of the detection means. The energization wave number for each wave is determined, and the energization is performed by the energization wave number. At this time, the energization is stopped for each half wave, and the energization within the predetermined period is performed by the energization wave number determined as described above. Is performed intermittently, the energization period for the controlled object is substantially increased, and flicker is prevented.

According to the second aspect of the present invention,
In the first aspect of the invention, since energization is stopped for each preset predetermined number of half waves from the start of energization in half-wave units within a predetermined period, there is no effect on the determined energization wave number, and there is no interruption. Realization of specific electricity.

Further, according to the third invention of the present application, in the above-mentioned first invention, the wave number control means sets the number of waves to be energized and the number of waves to stop energizing within a unit period obtained by further dividing the predetermined period. Since the ratio is determined, it does not affect the conduction wave number determined according to the deviation amount,
Realizes intermittent energization.

According to the fourth invention of the present application,
In the third aspect of the invention, since the ratio of the number of waves to be energized and the number of waves to stop the energization is variable, appropriate control is performed according to the frequency of the commercial power source or the determined number of energized waves.

Further, according to the fifth invention of the present application, the energization of the heating element is performed within a predetermined period according to the deviation amount between the control target temperature value of the heating element and the temperature value detected by the detecting means. Determine the half-wave energization wave number of the power supply,
It is performed by the energization wave number, at which time energization is stopped in units of half waves, and energization within the predetermined period by the energization wave number determined as described above is performed intermittently. Also in the fixing device of the type, the energization period to the heating body is substantially increased, and flicker is prevented.

According to the sixth invention of the present application,
In the fifth aspect of the invention, since energization is stopped for each preset predetermined half-wave from the start of energization in half-wave units within a predetermined period, there is no effect on the determined energization wave number, and there is no interruption. Realization of specific electricity.

Further, according to the seventh invention of the present application, in the fifth invention, the wave number control means sets the number of waves to be energized and the number of waves to stop energizing within a unit period obtained by further dividing the predetermined period. Since the ratio is determined, it does not affect the conduction wave number determined according to the deviation amount,
Realizes intermittent energization.

According to the eighth invention of the present application,
In the seventh aspect of the invention, since the ratio of the number of waves to be energized and the number of waves to stop the energization is variable, appropriate control is performed according to the frequency of the commercial power source or the determined number of energized waves.

[Brief description of drawings]

FIG. 1 is a diagram showing a heater control circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a fixing device according to a first exemplary embodiment of the present invention.

FIG. 3 is a timing chart showing wave number control in the first embodiment of the present invention.

FIG. 4 is a timing chart showing conventional wave number control compared with the first embodiment of the present invention.

FIG. 5 is a flowchart showing wave number control in the first embodiment of the present invention.

FIG. 6 is a timing chart showing wave number control in the second embodiment of the present invention.

FIG. 7 is a diagram showing a heater control circuit according to a third embodiment of the present invention.

FIG. 8 is a flowchart showing wave number control in the third embodiment of the present invention.

FIG. 9 is a diagram showing a conventional PWM output pattern.

[Explanation of symbols]

 1 Commercial Power Supply 2 Fixing Device 3 CPU (Wave Number Controlling Means) 8 Fixing Film (Heat Resistant Film) 9 Fixing Heater (Heating Body) 10 Pressure Roller PC1 Photo Triac (Switching Means) Q1 Transistor (Switching Means) Q2 Triac (Switching Means) ) R3 ceramic heater (heating element) TH thermistor (detection means)

Claims (8)

[Claims] 1. A switching means for switching a conduction state of a commercial power source to a controlled object, and driving the switching means in the vicinity of a zero cross of the commercial power source, for energizing and energizing the controlled object in half-wave units of the commercial power source. It comprises a wave number control means for stopping, and a detection means for detecting the control result value of the control object, the wave number control means, depending on the amount of deviation between the control target value of the control object and the control result value, In a power control device that is set to determine the number of energized waves in the unit of half wave within a predetermined period and to energize the controlled object by the number of energized waves, the wave number control means includes The power control device is set so that the energization is stopped in step S3, and the energization is intermittently performed within the predetermined period by the energization wave number determined as described above. 2. The wave number control means is set so as to stop energization for every preset predetermined number of half waves from the start of energization in half wave units within a predetermined period. The power control device according to. 3. The wave number control means is set so as to determine a ratio of a wave number for energizing and a wave number for stopping energizing in a unit period obtained by further dividing a predetermined period. Power control device. 4. The power control device according to claim 3, wherein a ratio of a wave number for energizing and a wave number for stopping energizing is variable. 5. A heating body which generates heat when energized, a heat-resistant film which is arranged so as to rub against the heating body, and a heating body which is arranged so as to come into pressure contact with the heating body through the heat-resistant film. A pressure roller, a switching means for switching the conduction state of the commercial power source to the heating body, and a driving means for driving the switching means in the vicinity of the zero cross of the commercial power source, for energizing and energizing the heating body in half-wave units of the commercial power source. A wave number control means for stopping and a temperature detection means for detecting the temperature of the heating body are provided, and the wave number control means is a deviation amount between a control target temperature value of the heating body and a temperature value detected by the temperature detection means. According to the above, in the fixing device which is set to determine the energization wave number in the half-wave unit within a predetermined period, and to energize the heating body by the energization wave number, the wave number control means is The fixing device is set so that energization is stopped in half wave units and energization is intermittently performed within the predetermined period by the energization wave number determined as described above. 6. The wave number control means is set so as to stop energization at every preset predetermined number of half waves from the start of energization in half wave units within a predetermined period. The fixing device described in 1. 7. The wave number control means is set so as to determine a ratio of a wave number for energizing and a wave number for stopping energizing in a unit period obtained by further dividing a predetermined period. Fixing device. 8. The fixing device according to claim 7, wherein a ratio of a wave number for energizing and a wave number for stopping energizing is variable.