JP2001265163A - Fixing control device and image forming device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing control device which has no heat, due to a large current by controlling a heating means in a short cycle. SOLUTION: In the device, a zero-cross signal 'a' of a power source 31 is counted by timers 34 to 3 7, a triac 24 or 25 is conducted by output of timers 34 to 37 and a fixing heater 22 or 23 is heated. Power feeding control is made possible in the short cycle without imparting an excessive load to CPU28, by controlling feeding of the power based on the output of the timers 34 to 37 within an average current-limiting cycle, that is shorter than a temperature control cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly, to a heating control of a fixing device.

[0002]

2. Description of the Related Art A thermal fixing device which is mounted on an image forming apparatus such as a copying machine, a printer, a facsimile or the like and heats an unfixed image transferred onto a recording material such as transfer paper to fix it on the recording material is well known. is there.

[0003]

In a conventional image forming apparatus, by controlling the supply and cutoff of power from a power supply to a heating means of a fixing device, for example, a fixing heater, the temperature of the heating means and the average consumption of the apparatus are controlled. In the case of controlling the current, the average current consumption is the same regardless of the control cycle,
When the control cycle becomes longer, the time during which a large current flows continuously becomes longer, and there is a problem that the temperature rise due to heat generation becomes larger.

On the other hand, if the heating means is controlled in a short cycle, there is a problem that the processing of the CPU which controls the control cannot be performed in time. That is, there are problems in the case where the control cycle is lengthened and in the case where the control cycle is shortened, and conventionally, the problems of the temperature rise and the CPU load increase cannot be solved simultaneously.

There is another problem that a fluctuation (so-called flicker phenomenon) such as flickering of other equipment connected to the power supply line, such as a fluorescent lamp, is caused by a voltage change applied to the power supply.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in a conventional image forming apparatus and to provide a fixing control apparatus which controls a heating means in a short cycle and does not generate heat due to a large current, and an image forming apparatus having the same. And Another object of the present invention is to prevent voltage fluctuation of a power supply.

[0007]

According to the present invention, there is provided a fixing control for controlling the temperature of the heating means and the average current consumption of the apparatus by controlling the power supplied from an AC power supply to the fixing heating means. In the apparatus, a first control cycle for controlling the temperature of the heating means and a second control cycle for controlling the average current consumption shorter than the first control cycle are provided,
This problem can be solved by providing a time-measuring means for counting with a zero-cross signal of an AC power supply, and controlling the power supply to the heating means within the second control cycle based on the output of the time-measuring means.

According to another aspect of the present invention, there is provided an image forming apparatus including a fixing device, which controls an electric power supplied from an AC power supply to a fixing heating unit to control the temperature of the heating unit and the temperature of the apparatus. A first control cycle for controlling the temperature of the heating unit, the fixing control apparatus controlling an average current consumption, and a second control cycle for controlling the average current consumption shorter than the first control cycle. It is proposed to provide a time-measuring means for counting with a zero-cross signal of the AC power supply, and to control the energization to the heating means within the second control cycle based on the output of the time-measuring means.

In order to solve the above-mentioned problem, the present invention provides the above-mentioned first control cycle, wherein the first control cycle is an integral multiple of 2 or more of the AC power supply cycle and 0.1 seconds or less, or 0.2 seconds or more and 1 second or less. Propose to be less than a second.

Further, in order to solve the above-mentioned problem, the present invention has a plurality of heating means divided into two groups, and energization of one of the heating means is performed at a cycle of the second control cycle. It is proposed that the energization is started from the start and the energization to the heating means of the other group be terminated at the end of the second control cycle.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a copying machine which is an example of an image forming apparatus according to the present invention.
The copying machine shown in FIG.
DF3.

A scanner 4 is arranged at an upper position in the main body 1, and various devices necessary for an electrophotographic process are arranged below the scanner 4 around a photosensitive drum 5. In the figure, among the devices arranged around the photosensitive drum 5, the developing unit 6, the transfer / conveying unit 7, and the cleaning unit 8 are denoted by reference numerals. A fixing device 10 is provided beside the transfer and transport unit 7. Further, this copying machine has three paper feed trays 9b, 9c and 9d in the paper feed table 2 in addition to the paper feed tray 9a in the main body, and has a total of four paper feed trays. ing. A manual tray 9e is provided on a side surface of the main body 1.

The operation of the copying machine will be briefly described. The surface of the photosensitive drum 5, which is rotationally driven by a driving unit (not shown), is uniformly charged by a charger.
The original image on the contact glass is read by the scanner 4 and is exposed on the photosensitive drum 5 to form an electrostatic latent image. The latent image on the photosensitive drum 5 is visualized by the developing device 6 to form a toner image.

On the other hand, four-stage paper feed trays 9a, 9b, 9
Paper is called from any of c, 9d and the manual feed tray 9e, and is conveyed to the registration roller 11. Then, the toner image on the photosensitive drum 5 is transferred to the transfer position at a transfer timing.

The toner image on the photosensitive drum 5 is transferred onto the sheet sent to the transfer position by the transfer / conveyance unit 7, and the sheet is separated from the photosensitive drum 5 and fixed to the fixing device 1.
Sent to 0. After the unfixed toner image on the sheet is fixed by the fixing device 10, the sheet is
Is discharged to After the transfer of the toner image, the photosensitive drum 5 is cleaned by the cleaning device 8 to prepare for the next image formation.

In the fixing device 10, a pressure roller is pressed against a fixing roller at a predetermined pressure (by a pressure spring not shown). Since the basic configuration of the fixing device 10 is the same as that of a conventionally known fixing device, a description will be given mainly of a portion related to the present invention.

FIG. 2 is a schematic diagram conceptually showing the configuration of the fixing roller of the fixing device 10, the fixing heater disposed therein, and a control section thereof. As shown in FIG. 1, two halogen lamps 22 and 23 are provided in a fixing roller 21 as a fixing heater as a heating means. In the image forming apparatus of the present embodiment, the paper conveyance reference is the center reference,
The halogen heaters are an inner heater 22 corresponding to small-size paper and an outer heater 23 corresponding to large-size paper. The inner heater 22 is provided for the fixing roller 21 (in the axial direction).
The outer heater 23 has a heating area only in a predetermined range at both ends of the fixing roller 21.

The fixing roller 21 is provided with thermistors 29 and 30 as temperature detecting means. The central thermistor 29 measures the temperature at the center of the fixing roller 21,
The outer thermistor 30 measures the temperature near the end of the fixing roller 21. The output of each thermistor is a CP that controls the fusing control.
It is input to U28. Note that the CPU 28 may be the CPU of the image forming apparatus.

An AC power supply 31 is supplied to the fixing heaters 22 and 23.
Is supplied with power. The zero-cross timing of the AC power supply is detected by a zero-cross detector 38. The zero-cross detector 38 generates a zero-cross signal: a when the voltage of the AC power supply becomes 0 volt. This zero-cross signal is counted by timers 34, 35, 36 and 37. Each timer has an initial value set by the CPU 28.

The inner heater 22 is connected to an AC power supply 31 via a triac 24, and the outer heater 23 is connected to the AC power supply 31 via a triac 25. Each triac is a semiconductor rectifier that switches on / off the energization of each heater. Note that it is also possible to use a switching element other than the triac. A driver 26 is connected to the gate of the triac 24 that switches on / off the energization of the inner heater 22, and the triac 2 switches on / off of the energization of the outer heater 23.
The driver 27 is connected to the gate of No. 5.

The output b of the timer 34 and the output c of the timer 35 among the four timers are AND gates 3
2 is input. AND gate 32 includes timers 34 and 3
5 is sent to the driver 26.
When both the outputs of the timers 34 and 35 become high (H) level, the triac 24 conducts, and the energization to the inner heater 22 is turned on. The timers 34 and 35 are a first inside timer and a second inside timer for switching the energization of the inside heater 22.

The output d of the timer 36 and the output e of the timer 37 are input to the AND gate 33. The AND gate 33 outputs a signal obtained by multiplying the output of the timers 36 and 37 by: g
To the driver 27. When both the outputs of the timers 36 and 37 become high (H) level, the triac 25 conducts, and the energization to the outer heater 23 is turned on. Timer 3
Reference numerals 6 and 37 denote a first outside timer and a second outside timer for switching the energization of the outside heater 23.

In the present embodiment, the CPU 28 is determined by the operation mode (set in advance according to the operation mode).
Initial values of the first inner timer 34 and the first outer timer 36 are set according to the average current limit value. When the average current is set to 100% as in the warm-up mode immediately after the power is turned on, the entire control cycle is set to the H level. When the average current is set to 70% as in the case of copying, 70% of the control cycle is set to H level and 30% to L level.
The output phase after the control start is set so that the energization of the inner heater 22 starts at the start of the control cycle and the energization of the outer heater 23 ends at the end of the control cycle.
The first inside timer 34 is set to the H level, and the first outside timer 36
Is set to the L level.

FIG. 3 shows that the AC power supply frequency is 50 Hz,
Average current limit period: Ta is set to 0.1 second, and control when the average current limit value is set to 70% for both the inner heater 22 and the outer heater 23 is shown as a timing chart of each control signal. Note that the temperature control cycle: Tb> the average current limit cycle: T
a. For example, Tb = 1 second and Ta = 0.1 second.

As shown in FIG. 3, the average current limit period: T
If a is set to 0.1 second, the AC power supply of 50 Hz in the cycle Ta has five cycles. Therefore, the zero-cross signal is generated ten times with a period: t. 70 average current limit
%, The average current limiting signals of the inner heater 22 and the outer heater 23 are H (ON) for only 7t.
And L (OFF) for 3t. FIG. 3 shows a voltage applied to the inner heater 22 corresponding to the average current limit signal H (ON) of the inner heater 22.
The voltage applied to the outer heater 23 is not shown.

2 and 3, the CPU 28 sets initial values of the second inner timer 35 and the second outer timer 37 based on the temperature of the fixing roller 21 measured by the central thermistor 29 and the outer thermistor 30. Then, control signals are sent to the triacs 24 and 25 via the drivers 26 and 27 to control the energization of the inner heater 22 and the outer heater 23 so that the temperature of the fixing roller 21 is controlled to a predetermined temperature. .

Further, the CPU 28 determines the heater duty ratio in the next control cycle period based on the measured temperature of the fixing roller 21. A value obtained by dividing (dividing) this duty ratio by the average current limit value is set as the H level cycle of the second inner timer 35 and the second outer timer 37. For example, if the duty ratio is 55
%, If the average current limit value is 70%, 0.55
Assuming /0.7≒0.8, 80% of the control cycle is set to the H level, and 20% is set to the L level. Further, for example, if the average current limit value is 70% when the duty ratio is 40%, 0.4 / 0.7 ≒ 0.6, and the control cycle is 6
0% is set to the H level, and 40% is set to the L level. Further, the energization of the inner heater 22 is controlled in the control cycle (T
In order to start from the start of a) and terminate the energization to the outer heater 23 at the end of the control cycle (Ta), the output phase after the control start is set by setting the second inner timer 35 to the H level, The second outside timer 37 is set to be at the L level.

A signal obtained by multiplying the output of the first inner timer 34: b (FIG. 1) and the output of the second inner timer 35: c (FIG. 1): When the signal f (FIG. 1) is at the H level, the triac 24 Is turned on, and the inner heater 22 is energized to generate heat. Similarly, a signal obtained by multiplying the output of the first outer timer 36: d (FIG. 1) and the output of the second outer timer 37: e (FIG. 1): g
When (FIG. 1) is at the H level, the triac 25 is turned on and the outer heater 23 is energized to generate heat.

As described above, the temperature control cycle: the average current limiting cycle: Ta shorter than Tb is set, and the timers 34 to 37 for counting by the zero-cross signal of the AC power supply are provided to fix the fixing heater (the inner heater 22 and the Outside heater 2
By controlling the energization to 3), it is possible to control the supply and cutoff of power to the heater in a short cycle without increasing the load on the CPU, and to limit the current in a short control cycle (large current). The temperature rise can be prevented from becoming too large (by shortening the time during which the gas continuously flows).

When the temperature of the fixing heater (fixing roller) and the average current consumption of the apparatus are limited by controlling the supply and cutoff of electric power from the power supply to the heating means (fixing heater), a low-frequency power supply to the AC power supply of the apparatus is required. Voltage fluctuation, which is a disturbance of the signal, occurs at a period of 0.114 seconds (frequency 8.8 Hz)
The effect is greatest at.

Therefore, in the present embodiment, the temperature control cycle is set to an integral multiple of 2 or more of the AC power cycle and 0.1 second or less. Alternatively, the temperature control cycle may be 0.2 seconds or more and 1 second or less. Here, the temperature control cycle is set to 1 second,
FIG. 4 shows a case where the duty ratio of the inner heater 22 is 55%, the duty ratio of the outer heater 23 is 40%, and the average current limit value is 70% for both the inner heater 22 and the outer heater 23.

In FIG. 4, Tb = 1 second, Ta = 0.1
Since it is seconds, Tb = 10Ta. During this temperature control cycle: Tb, the average current limiting signals of the inner heater 22 and the outer heater 23 are turned ON / OF in the cycle Ta, respectively.
F (H / L), and this is repeated. At this time, as can be seen from the figure, the temperature control signal of the inner heater 22 is continuously generated for a period of 8 Ta from the start. Further, the temperature control signal of the outer heater 23 is continuously generated for the latter half 6Ta. Accordingly, the energization status of the inner heater 22 and the energization status of the outer heater 23 are illustrated as “energized” and “blank”, respectively.

The current consumption in the fixing device is the sum of the currents flowing when the inner heater 22 and the outer heater 23 are energized, and shows that the current consumption increases in the portion where the "energization" of both heaters overlaps. . The change cycle of this current (fixing device consumption current) is Ta, which is the average current limit cycle.
And the temperature control cycle Tb. Further, the inner heater 22 and the outer heater 23 are simultaneously turned ON / OFF.
Since it has not been turned off, no large current change has occurred.

As described above, by separately providing the temperature control cycle and the average current limit cycle, the cycle (0.114) which is most affected by the voltage fluctuation can be avoided, and problems such as flickering of the lighting equipment can be effectively prevented. Can be prevented. In addition, by not turning on / off a plurality of heaters at the same time, a change in current can be kept small, and voltage fluctuation can be further reduced.

As described above, the present invention has been described by taking the copying machine of the embodiment as an example, but the present invention is not limited to this. For example, the present invention can be applied to an image forming apparatus other than a copying machine, such as a printer or a facsimile. The configuration of the image forming unit of the image forming apparatus is also an example, and a digital system using laser writing or the like may be used.

Further, the heater as the heating means is not limited to a halogen lamp. Further, the number of fixing heaters is not limited to two, and a single heater or an arbitrary number of heaters may be used. For example, when three or more heaters are provided, three or more heaters can be divided into two groups, and the power supply to the heaters can be controlled for each group. Further, the paper conveyance reference is not limited to the center reference, and the distribution of the heat generating region of the fixing heater can be appropriately set according to the paper conveyance reference.

Further, the temperature control cycle and the average current limit cycle can be set to appropriate values within the scope of the present invention.
The duty ratio to the heating means, the average current limit value, and the like can also be set as appropriate.

[0038]

As described above, according to the fixing control device of the present invention and the image forming apparatus provided with the same, the second control cycle (average consumption) shorter than the first control cycle (temperature control cycle). Current control cycle), and by providing a time-measuring means (timer) for counting with the zero-cross signal of the AC power supply and controlling the energization to the heating means, energization control in a short cycle becomes possible and large currents can be continuously generated. The flowing time does not become long, and the temperature rise due to heat generation does not increase.

According to the configuration of the third aspect, the energization control can be performed while avoiding the cycle in which the influence of the voltage fluctuation is greatest, and various problems due to the fluctuation of the power supply voltage can be prevented.

According to the structure of the fourth aspect, since the plurality of heating means are not turned on / off at the same time, the current change can be kept small, and the fluctuation of the power supply voltage can be further reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a copying machine as an example of an image forming apparatus according to the present invention.

FIG. 2 is a schematic diagram conceptually showing a configuration of a fixing roller of a fixing device provided in the copying machine, a fixing heater disposed therein, and a control unit thereof.

FIG. 3 is a timing chart showing one mode of fixing control in the embodiment.

FIG. 4 is a timing chart showing another mode of the fixing control in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier main body 10 Fixing device 21 Fixing roller (heating roller) 22 Inner heater (heating means) 23 Outer heater (heating means) 24, 25 Triac 26, 27 Driver 28 CPU (control means) 29, 30 Thermistor 32, 33 AND Gate 34-37 Timer (measuring means)

Claims (4)

[Claims] 1. A fixing control device that controls power supplied from an AC power supply to a fixing heating unit to control a temperature of the heating unit and an average current consumption of the apparatus, wherein a first temperature of the heating unit is controlled. And a second control cycle for controlling the average current consumption, which is shorter than the first control cycle, provided with time-measuring means for counting with a zero-cross signal of an AC power supply, and based on an output of the time-measuring means. Wherein the power supply to the heating means is controlled within the second control cycle. 2. An image forming apparatus having a fixing device, comprising: controlling power supplied from an AC power supply to a fixing heating unit;
A fixing control device that controls a temperature of the heating unit and an average current consumption of the apparatus; a first control cycle for controlling the temperature of the heating unit; and the average current consumption shorter than the first control cycle. A second control cycle for controlling the temperature control means, and a timer means for counting by a zero cross signal of the AC power supply is provided, and energization to the heating means is controlled within the second control cycle based on an output of the clock means. An image forming apparatus comprising: 3. The method according to claim 1, wherein the first control cycle is an integral multiple of 2 or more of the AC power supply cycle and 0.1 second or less, or 0.2 second or more and 1 second or less. 3. The fixing control device according to claim 1, or the image forming device according to claim 2. 4. A plurality of heating units divided into two groups, and energization to one group of heating units is started from the start of the second control cycle, and heating to the other group is performed. 2. The energization of the second control cycle is terminated at the end of the second control cycle.
3. The fixing control device according to claim 1, or the image forming device according to claim 2.