JP2001142353A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of reducing voltage fluctuation being the interference of low frequency to a power source by reducing the number of the times of fluctuation occurrence of current to be supplied to a heating means from a power source. SOLUTION: This image forming device is provided with a CPU 8 controlling power to be supplied to heaters 2 and 3 by controlling an energizing time within a period through TRIACS 4 and 5 for supplying power selectively to the heaters 2 and 3. The CPU 8 has plural period times of different times and switches the period time selectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention comprises a heating means,
The present invention relates to an image forming apparatus having means for fixing an unfixed image on a recording material.

[0002]

2. Description of the Related Art Most image forming apparatuses such as copiers, printers, and facsimile machines use a fixing device having a fixing roller heated by a heating unit. This type of fixing device detects the surface temperature of a fixing roller, and controls on / off of a heater as a heating unit based on a signal of the detected temperature. In this control, the surface temperature is measured every predetermined control cycle time, and the energization time to the heater within the cycle is controlled via a triac.

In the case of such a device for performing temperature control, one on and one off occur within the control cycle time.
The current fluctuates each time. Therefore, if the control cycle time is set to be short, the number of times of current fluctuations within a certain time increases, and the voltage fluctuations, which are low-frequency disturbances to the device power supply, increase, causing a serious problem. Therefore, if the control cycle time is lengthened, the number of occurrences of current fluctuation within a certain time can be reduced, and the above-described voltage fluctuation can be advantageously reduced.

[0004]

However, in the above-described apparatus for performing temperature control, if the control cycle time is lengthened, the amount of power supplied to the heating means cannot be changed quickly. Therefore, when the control cycle time is long, there is no problem when the amount of heat that needs to be generated by the heating device is almost constant, but when the required amount of heat changes in a short period of time, it cannot cope with the change, and the generated heat amount Becomes excessive or insufficient, so that appropriate heating cannot be performed. Specifically, in a preheating state such as when the apparatus is in a standby state, the required amount of heat is almost constant, whereas during image formation, a large amount of heat is generated when the recording material passes through the fixing device. However, a small amount of heat is sufficient before and after that, and the required amount of heat changes in a short period of time. Therefore, if the control cycle is long, there is a problem that the temperature control of the fixing device becomes unstable during image formation even if there is no problem in the preheating state, and the temperature becomes too high or too low. .

[0005] The present invention solves the above-mentioned conventional problems,
It is an object of the present invention to provide an image forming apparatus capable of reducing voltage fluctuations, which are low-frequency disturbances to a power supply, by reducing the number of occurrences of fluctuations in current supplied from a power supply to a heating unit.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to an image forming apparatus having a heating means and a means for fixing an unfixed image on a recording material, wherein the heating means is selectively provided. Control means for controlling the power supplied to the heating means by controlling the power supply time within the cycle through the power supply means for supplying power, the control means having a plurality of cycle times having different times, It is characterized by selectively switching the time.

According to another aspect of the present invention, there is provided an image forming apparatus comprising: a plurality of grouped heating units; and a unit for fixing an unfixed image on a recording material. Control means for controlling the power supplied to the heating means by controlling the power supply time within the cycle via the power supply means for selectively supplying power, the control means comprising, for each group, the heating means It is characterized in that control is performed so that the cycle of the power supply time to the power supply is different.

Further, in order to solve the above problems, the present invention comprises a plurality of grouped heating means,
In an image forming apparatus having a unit for fixing an unfixed image on a recording material, the heating unit is supplied to the heating unit by controlling an energizing time within a cycle via an energizing unit that selectively supplies power to the heating unit. A control unit for controlling electric power and a unit for detecting a range in which the heating unit is heated are provided, and the control unit includes, for each group, an energization time to the heating unit based on the range detected by the heating range detection unit. Are controlled so as to have different periods.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a fixing roller of an image forming apparatus according to the present invention and a control system thereof.

In FIG. 1, 1 is a fixing roller, and 2 and 3 are heaters provided on the fixing roller 1 as heating means. A pressure roller (not shown) as pressure means is pressed against the fixing roller 1 to constitute a fixing means.
When the fixing roller 1 and the pressure roller are rotated and driven to nip and convey a recording material carrying an unfixed toner image,
The heat generated from the heaters 2 and 3 heats the unfixed toner image transferred onto the recording material via the fixing roller 1 to fix the toner image on the recording material.

In the case where the image forming apparatus conveys the recording material on the basis of the center and can record even a wide recording material such as A3 size, for example, even in the case of a narrow recording material such as A5 size, fixing is performed. It is necessary to reduce temperature unevenness in the width direction of the roller. For this reason, the heaters 2 and 3 are both halogen heaters. However, the heater 2 has a heat generating portion only at the central portion and is configured to supply heat only to the inside of the heating roller. The heat roller is provided only in the portion, and heat is supplied only to both outer sides of the heating roller. The heaters 2 and 3 are divided into, for example, two groups according to a region to be heated. Therefore, the heaters 2 and 3 whose heating regions are different between inside and outside belong to different groups.

One end of each of the heaters 2 and 3 is connected to an AC power source 1.
1 and the other ends of the heaters 2 and 3 and the AC power supply 1
A switch element composed of triacs 4 and 5 is connected between the other end of the switch 1 and the other end of the switch 1. The triacs 4 and 5 include control drivers 6 and
The control drivers 6 and 7 are controlled by a CPU 8 as control means. The fixing roller 1 includes
Thermistors 9 and 10 are provided as temperature detecting elements for detecting the surface temperature. The thermistor 9 is disposed in the inner region of the fixing roller 1 so as to measure the temperature of the heater 2 group. It is arranged outside the fixing roller 1 so as to measure the temperature.
The temperature detection signals of these thermistors 9 and 10 are sent to CPU 8
Is input to Reference numeral 12 denotes an image forming start / end signal, a paper feed tray selection signal, and paper feed tray size direction setting information sent from the paper feed control unit for conveying the recording material to be heated, which are input to the CPU 8. is there.

The CPU 8 measures the temperature with the thermistor 9 and thermistor 10 at every control period T time, and sends a control signal to the triacs 4 and 5 via the drivers 6 and 7.
The energization time of the heaters 2 and 3 during the next control cycle is determined by PID control so that the energization of the heaters 2 and 3 is controlled so that the surface temperature of the fixing roller 1 becomes a predetermined temperature. The CPU 8 of the present embodiment has two cycle times having different times, and controls the switching between the time of image formation and the time of preheating.

FIG. 2 is a timing chart showing an example of the control. First, when the image formation is started, a signal 12 for starting the image formation is sent from the paper feed control unit, and the CPU 8 controls the operation of the apparatus. It recognizes that it is in the image state. CP during imaging
U8 performs the control described above every control period T1. That is, the temperature is measured by the thermistors 9 and 10, control signals are sent to the triacs 4 and 5 via the drivers 6 and 7, and the energization of the heaters 2 and 3 is controlled so that the surface temperature of the fixing roller 1 becomes a predetermined temperature. So that PI
The energizing time of the heater 2 and the heater 3 during the next control cycle is determined by the D control. In the example of FIG. 2, a case where 70% of the control cycle T <b> 1 of both the heater 2 and the heater 3 becomes the energization time for three consecutive periods during the image forming period is shown. At this time, the heater 2 starts energization from the start of the cycle and stops energization after 0.7T1 time has elapsed.
The heater 3 starts energization 0.3 T1 after the start of the cycle, and ends the energization when the cycle ends.

Next, when the image formation is completed, an image formation end signal 12 is sent from the paper feed control unit, and the CPU 8 recognizes that the apparatus is in the preheating state. During the preheating period, the CPU
During the image forming period, the control cycle time is switched, and the heater 2 during the next control cycle is controlled by PID control so that the temperature of the fixing roller 1 becomes a predetermined temperature every T2 time corresponding to three times the time T1. And the energizing time of the heater 3 are determined. During the preheating period, the example of FIG. 2 shows a case where both the heater 2 and the heater 3 are energized for 20% of the control cycle T2. Also at this time, the heater 2 starts energization from the start of the cycle, and stops energization after 0.2T2 time elapses.
The heater 3 starts energization 0.8 T2 after the start of the cycle, and ends when the cycle ends.

FIG. 2 also shows the current consumption of the fixing device, which is the sum of the currents flowing when the heaters 2 and 3 are energized. I1 is the current flowing through the heater 2, I3 is the current flowing through the heater 3, and I2 is the sum of the currents flowing through both the heater 2 and the heater 3, that is, the sum of I1 and I3. Further, dI1 indicates that the consumption current of the heating current is I3.
DI2 indicates a current change amount when the consumption current of the heating current changes from I1 to I2, and dI3 indicates a current change amount when the consumption current of the heating current changes from I2 to I3. The amount of change is shown. During the preheating period, one control cycle time, that is, T2 time is 3 × T1 time,
The change in the current consumption is suppressed by the occurrence of dI1, dI2, and dI3 once each.

FIG. 3 shows an image forming period when an A5 size recording material is used in the vertical direction. This recording material is passed through the heating area of the heater 2. Therefore, the heater 2 supplies heat to the recording material, but the heater 3 does not supply heat to the recording material. In this case, since the image formation is being performed, initially, both the heater 2 and the heater 3 have the control period T.
1, the heater 3 that does not supply heat to the recording material keeps the power ratio, which is the ratio of the power-on time to the control cycle time, as small as the preheating state, and only the heater 2 has the large power-on ratio in the image forming state. Is energized. And heater 3
When the CPU 8 detects that the duty ratio of the heater 3 is small and stable, the control cycle of only the heater 3 is switched from T1 to T2. This switching is performed by the heater 3 in the control cycle T1.
It is determined that the energization of a plurality of times, for example, three times consecutively, is small CP
When U8 detects, the control cycle is set to T2 for only the heater 3. After this switching, since the time T2 is 3 × T1 time, the change in the current consumption is one for dI1 and one for dI2,
When dI3 is five, the number of occurrences is reduced.

The timing chart shown in FIG. 4 is also the same as FIG. 3 for the image forming period when the A5 size recording material is used in the vertical direction. In this case, the fact that the width of the recording material is small can be determined from the paper feed tray selection signal and the paper feed tray size direction setting information. Performs control in the control cycle T2. Therefore, T2 time, that is, 3 ×
The change in current consumption during the time T1 is that dI1 is 1 from the beginning.
Times, dI2 is suppressed to one time, and dI3 is suppressed to five times.

FIG. 5 shows the control period T for both the image forming period and the preheating period.
1 is a case of the prior art in which the energization of a plurality of heating means is controlled. As in FIG.
In both cases, the preheating period indicates a case where 20% of the control cycle is the energization time. In the change of the current consumption, dI1, dI2, and dI3 occur once each in time T1 within one control cycle. Therefore, the change in current consumption at time T2, which is three times the time T1, is dI1, dI2, and dI3.
Occur three times each.

In the preheating period, both heaters 2 and 3 have a power-on time of 20% of the control cycle.
Table 1 shows the results of comparing the current change amount and the number of times (= 3 × T1) with the present invention in FIG. 2 and the prior art in FIG.

[0021]

[Table 1] As is clear from Table 1, the present invention can reduce the number of current changes as compared with the prior art. Therefore, it is possible to reduce the voltage fluctuation which is a low-frequency disturbance to the device power supply.

FIG. 6 shows a case of the prior art in which energization to a plurality of groups of heating means is controlled at the same cycle.
4A and 4B show the image forming period of an A5 size recording material, as in FIGS. 3 and 4 of the present invention. The heater 2 shows a case where 70% of the control cycle is the energizing time, and the heater 3 shows a case where 20% is the energizing time. ing. In the change of the current consumption, dI1, dI2, and dI3 occur once each in time T1 within one control cycle. Therefore, in the change in the current consumption at the time T2, which is three times the time T1, the times dI1, dI2, and dI3 occur three times each.

When the heater 2 is energized for 70% of the control cycle and the heater 3 is energized for 20% of the control cycle, the present invention is implemented by the scheme of FIG. 4 and the prior art of FIG. Table 2 shows the results of comparing the current change amount and the number of times during the time T2 (= 3 × T1).

[0024]

[Table 2] As is clear from Table 2, the number of current changes can be reduced by using the present invention as compared with the prior art.

The present invention relates to the above embodiment,
In each of the groups, the heating means is constituted by one halogen heater for each of the heaters 2 and 3, but each group may be constituted by a plurality of halogen heaters such as two heaters. Further, when the electric heater is turned off for a sufficiently short time compared to the control cycle time at the start and end of energization, the energization angle from the AC power supply to the electric heater is controlled to be larger than 0 ° and smaller than 180 °. And then set the conduction angle to 0
If the phase angle control to make degrees is also performed to reduce the change in current consumption, it is possible to further reduce the disturbance of voltage fluctuation on the power supply.

[0026]

According to the first aspect of the present invention, in the preheating state, the power supply control cycle is made longer than that in the image forming state, so that the number of occurrences of fluctuation of the current supplied from the power supply to the heating means is reduced. Voltage fluctuations, which are low-frequency disturbances to the power supply, can be reduced.

In the apparatus according to the second aspect, when it is detected that the duty ratio is small and the change is small, the power supply control cycle of the heater is switched to be longer, thereby reducing the number of occurrences of the fluctuation of the current supplied from the power supply to the heating means. By
Voltage fluctuations, which are low-frequency disturbances to the power supply of the device, can be reduced.

In the apparatus according to the third aspect, by changing the energization control cycle of the heater, which is determined not to be used for heating from the size of the recording material, to be longer, the number of occurrences of fluctuation of the current supplied from the power supply to the heating means can be reduced. By doing so, it is possible to reduce the voltage fluctuation which is a low-frequency disturbance to the power supply of the device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a fixing roller of a fixing device according to the present invention and a control system thereof.

FIG. 2 is a graph showing an example of control of current supply to two heaters according to the present invention and a relationship between current consumption of a fixing device by the control;

FIG. 3 is a graph showing a relationship between another example of power supply control to two heaters and current consumption of a fixing device by the control according to the present invention.

FIG. 4 is a graph showing a relationship between still another example of power supply control to two heaters and current consumption of a fixing device by the control according to the present invention.

FIG. 5 is a graph showing a relationship between conventional power supply control to a heater and current consumption of a fixing device by the control.

FIG. 6 is a graph showing a relationship between another control of current supply to a conventional heater and current consumption of the fixing device by the control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2, 3 Heater 4, 5 Triac 8 CPU 9, 10 Thermistor

Claims (3)

[Claims] 1. An image forming apparatus comprising a heating unit and a unit for fixing an unfixed image on a recording material, wherein an energizing time within a cycle is set via an energizing unit for selectively supplying power to the heating unit. An image forming apparatus, comprising: control means for controlling power supplied to the heating means by controlling the control means, the control means having a plurality of cycle times having different times, and selectively switching the cycle times. 2. An image forming apparatus comprising: a plurality of grouped heating units; and a unit for fixing an unfixed image on a recording material, wherein the heating unit includes a power supply unit for selectively supplying power to the heating unit. Control means for controlling the power supplied to the heating means by controlling the power supply time within the cycle, and the control means controls the power supply time cycle to the heating means to be different for each group. An image forming apparatus. 3. An image forming apparatus comprising a plurality of grouped heating units and a unit for fixing an unfixed image on a recording material, wherein the heating unit is provided with a power supply unit for selectively supplying power to the heating unit. Control means for controlling the power supplied to the heating means by controlling the energization time within the cycle, and means for detecting the range of heating by the heating means are provided, the control means for each group, The image forming apparatus according to claim 1, wherein a period of a current supply time to said heating unit is controlled depending on a range detected by said heating range detection unit.