JPH10274901A - Power control device - Google Patents

Abstract

(57) [Problem] To provide a power control device which efficiently distributes power consumed by an image forming apparatus and has a short rise time. SOLUTION: A fixing device 14 supplied via a current detecting means 2 for detecting a current inputted to an image forming apparatus 1, a heater temperature detecting means 12 for detecting a temperature of the fixing device 14,
The current supplied to the fixing heater 10 is controlled by the temperature control unit 11 for controlling the temperature of the fixing device so that the input current of the image forming apparatus 1 becomes equal to or less than a predetermined value. In order to achieve the above object, the conduction ratio of the switch element 18 is controlled, and an output setting signal is supplied via the time constant means 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater power control device used for a fixing device such as a copying machine or a printer.

[0002]

2. Description of the Related Art Conventionally, a heater power control device used in a fixing device such as a copying machine or a printer is disclosed in
Rectifying the AC power supply as disclosed in 6358 publication,
2. Description of the Related Art There is known a power control device which is provided with a switch so as to control an output voltage of current supplied to a fixing device heater to be substantially constant.

FIG. 7 shows the transition of the current input from the AC power supply AC from the time when the power switch SW is turned on to the time when the image formation is completed in the above-mentioned conventional system. At time A in FIG. 7, the power switch SW is turned on, and a voltage is supplied to each power supply.
As a result, the driving power supply of the control circuit CONT is changed to the low voltage power supply PS.
Supplied from the U flows input current I _1. Next, the rise of the fixing roller R starts at the point B, and the heater power supply HEA
Current IHT flows T, thereby the input current increases to I _4. When the temperature of the heater HT reaches a predetermined value at the point C, short to maintain its temperature (C _1, C _2, ... Cn point)
Has been switched to the standby state in which the power is supplied to. Thus the applied voltage of the heater HT is averagely lower, the average input current is reduced to I _2. This current continues during standby until image formation starts.

[0004] Next energization for driving the mechanical elements of the power and the image forming apparatus of the lamp LP for document reading the image formation is started at point D is performed, the input current increases to I _3. When the temperature of the fixing roller by the image forming is lowered, the energization of the heater HT is performed, the input current increases to I _5.
When the lamp LP is turned off during image formation, the input current is also reduced to I ₃ L or I ₅ L. Therefore, the input current during image formation varies between I ₃ L and I ₅ . An input current image formation is completed is returned to the I ₂ in the standby state.

[0005]

From the above, it can be seen from the transition of the input current in FIG. 7 that the input current consumed by the heater HT is large. The maximum input current occurs when the lamp LP is turned on during image formation. For this reason, in the image forming apparatus, the current capacity of the heater HT is generally set so that the current value is equal to or less than a current value that can be used in a normal commercial power outlet even when the input current is the largest (rated current). In FIG. 7, I ₅ −
I ₃ = ΔIH is the current capacity of the heater HT. Therefore, at the time of startup at the point B where only the heater HT is activated, the value is lower than the rated current.

[0006] These prior arts described above have a drawback that a long rise time is required because the power consumption of the heater is fixed, although the ratio of the power consumption of the heater is extremely large. Further, when the heater is turned on and off, a large change in current occurs, which causes a problem that flicker occurs inside the lighting equipment and the image forming apparatus.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional power control device and to reduce the power consumption allocated to the machine so that the input current of the image forming device becomes a predetermined value or less. An object of the present invention is to provide a power control device that controls heater power consumption so that it can be used well and has a fast rise.

[0008]

In order to achieve the above object, the present invention provides an input current detecting means for detecting a current input from an AC power supply to an image forming apparatus. An image forming apparatus comprising: a fixing device to which power is supplied via an input current detecting unit; a heater temperature detecting unit that detects a temperature of the fixing device; and a temperature control unit that controls a temperature of the fixing device. The current supplied to the fixing heater is controlled so that the input current becomes a predetermined value or less.

According to a second aspect of the present invention, there is provided an input current detecting means for detecting a current input from an AC power supply, and a heating means and a switch element which perform full-wave rectification on the power supplied through the input current detecting means. In the power control device having a heater power supply for supplying the series circuit and the switch, the switching element is switched at a cycle shorter than the cycle of the AC power supply,
It is characterized in that the conduction ratio of the switch element is controlled according to the detection output of the input current detection means.

According to a third aspect of the present invention, there is provided an input current detecting means for detecting a current input from an AC power supply to an image forming apparatus, a lamp power supply and a heater driven by a power supply supplied through the input current detecting means. In a power control device having a power supply and including a control circuit for controlling an output of a heater power supply according to a value detected by an input current detection means, setting of an output to the heater power supply from the control circuit via a time constant means It is characterized in that a signal is supplied.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
In the embodiment, the same portions are denoted by the same reference numerals, and the portions described in the first embodiment are the same as those in the second and third embodiments.
In the embodiment, description will be omitted, and different portions will be mainly described. In the first embodiment shown in FIG.
Denotes an image forming apparatus, and 2 denotes a current detecting unit. The current detecting means 2 receives an input current from the AC power supply 3 via the power switch 4 and outputs the input current to the low-voltage power supply 5, the lamp power supply 6, and the heater power supply 7.
To supply. The low-voltage power supply 5 has an input side connected to the AC power supply 3 via the power switch 4 and an output side connected to a DC low-voltage load 8 such as a control circuit to supply a current IR thereto.

The lamp power supply 6 has an input side connected to the AC power supply 3 via the power supply switch 4 and the current detecting means 2 and an output side connected to a document reading lamp 9 to supply a current ILP thereto. doing. The heater power supply 7 has an input side connected to the AC power supply 3 via the power switch 4 and the current detecting means 2, and has an output side connected to the heater 10 and an output current I.
HT is supplied, and the output voltage VH of the heater 10 is controlled by the control circuit controller 11. The lamp 9 is used for reading a document. The lamp 9 is connected to the lamp power supply 6 and is turned on by the output current ILP. The control circuit controller 11 is connected to the current detecting means 2 and
An input signal from the thermistor 12, which is a temperature detecting means, is subjected to arithmetic processing, and a control signal is supplied to the heater power supply 7, the lamp power supply 6 (not shown), and the low-voltage load 8.

In FIG. 1, when a power switch 4 is turned on, a voltage is applied from an AC power supply 3 to a low-voltage power supply 5, a lamp power supply 6, and a heater power supply 7 via a current detection means 2,
When low-voltage power is supplied from the low-voltage power supply 5 to the control circuit controller 11, the image forming apparatus 1 starts operating. At the start of this operation, it is necessary to start up the fixing device 14, and therefore, a signal for turning on the heater power supply 7 is output from the control circuit controller 11, and the heater 10 is energized so that the fixing roller 13 containing the power is turned on. Heated. In order to control the temperature of the fixing roller 13 to a predetermined value, the temperature is detected by a thermistor 12 provided in the vicinity of the fixing roller 13, and the detected value is input to the control circuit controller 11, and the heater is operated in accordance with the detected value. The output voltage of the power supply 7 is controlled. When the temperature of the fixing roller 13 reaches a predetermined value, the image forming apparatus 1 is ready for use and starts image formation. Next, lamp power supply 6
Is turned on, the lamp 9 is turned on, and power is supplied from the low-voltage power supply 5 to the low-voltage load 8 according to the image forming process.

In the above case, the transition of the current input from the AC power supply from when the power switch (not shown) is turned on until the image formation is completed will be described with reference to FIG.
In the above-described conventional power control device, the input current is maximized when the lamp is turned on during image formation as shown in FIG. For this reason, the current capacity of the heater is set so as to be equal to or less than the current value that can be used in a normal outlet. Therefore, it can be seen that the value is lower than the rated current when the heater is activated. In this scheme of the present invention is the relationship, at the stage of putting the point B the power switch, to increase the input current supplied to the heater 10 to a maximum of I _5. Since the conventional method I ₅ -I ₄ only large current can flow to the heater 10 than it can be understood that the complete rise in a short time. The energization time during standby is also shortened. The period in which the lamp 9 at the time of image formation is off, the amount that the input current to the lamp 9 is decreased to increase the current flowing through the heater 10, during energization of the heater 10 I ₅
Of the input current.

Therefore, in the present invention, as described above, control is performed so that the maximum current is supplied to the heater while the current input to the image forming apparatus is kept below a predetermined value. This makes it possible to use a heater having a larger current capacity than in the conventional method, and to achieve this, a variable heater power supply capable of controlling the current supplied to the heater is used. This makes it possible to provide a control device that starts quickly.

FIG. 3 shows a configuration diagram of a second embodiment of the present invention. This is the second embodiment. A power supply supplied from the AC power supply 3 via the current detection means 2 is subjected to full-wave rectification and supplied to the heater power supply.
Is switched at a cycle shorter than the cycle of the AC power supply 3, and the conduction ratio of the switch element 18 is controlled in accordance with the detection output of the current detection means 2. A halogen lamp 19 is used for the heater. doing.

In this embodiment, a full-wave rectifier 15 is provided. The input side of the full-wave rectifier 15 is connected to the AC power supply 3 via the current detecting means 2, and the output side is formed by the coil 16 and the capacitor 17. The configured filter and the switch element 18
And the input power supply 3 is full-wave rectified. At the output side of the filter is a halogen lamp 19 that constitutes a heater.
And a series circuit of the switch element 18 and the switch element 18 are connected. The switch element 18 switches at a high frequency to make the conduction time variable, and a heater power supply control unit 20 is connected to an output side thereof. A control circuit controller 21 is connected to the heater power controller 20 via a time constant means 21. The time constant means 21 is provided for the AC power supply 3 due to a sudden increase or decrease in the heater power supply.
This prevents the occurrence of flicker due to a voltage change in the heater power control unit 20.
Tag is supplied.

In such a device, when a control signal Tag from the control circuit controller 11 is input to the heater power control unit 20, a drive signal for the switch element 18 is output from the heater power control unit 20, and the switch element 18 is driven at a high frequency (for example, 20K
Hz) to start switching. As a result, the halogen lamp 19 is energized to heat the fixing roller 13. Although a pulse-shaped current flows due to the switching by the switch element 18, the effect of the pulse is suppressed by a filter provided at the preceding stage, so that the input current of the AC power supply 3 is a sine wave, and thus the input current is Harmonics are reduced. Although the coil 16 and the capacitor 17 constituting the filter can be miniaturized as the switching frequency is increased, the switching loss in the switch element 18 increases.
Generally, it is set near the above-mentioned frequency.

The temperature of the fixing roller 13 is proportional to the current flowing through the halogen lamp 19, and this current is proportional to the conduction ratio of the switch element 18. Accordingly, the temperature of the fixing roller 13 can be controlled by making the conduction time of the switch element 18 switching at the above-mentioned frequency variable. Therefore, the control circuit controller 11 inputs a reference signal and a roller temperature detection signal to the heater power supply control unit 20 so that the temperature of the fixing roller 13 becomes a predetermined value (for example, 180 ° C.), and compares and inputs these signals. Outputs the conduction time as a detection signal,
PWM (pulse width modulation) is performed in response to this. P
WM fixes the switching period T, and changes the conduction time of the switch element 18 according to the temperature of the fixing roller 13. When the roller temperature detected by the thermistor 12 is lower than a predetermined value, the switch conduction time t is reduced. The conduction time t is narrowed when the switching element 18 is wide, and when it is high, the conduction ratio of the switch element 18 is controlled.

Further, the control circuit controller 11 controls the control signal T so that the current input to the image forming apparatus 1 becomes a predetermined value.
ag is corrected. The circuit shown in the block diagram of FIG.
The first comparator 22 calculates the temperature of the fixing roller 13 and the reference voltage, and generates a control signal Tag. The reference voltage of the first comparator 22 is corrected by the second comparator 23 of the input current to form a constant current control loop. The relationship between the conduction ratio and the input current is proportional as shown in FIG.

FIG. 4 shows a third embodiment of the present invention. In this embodiment, a time constant means 21 is connected between the control circuit controller 11 and the heater power control unit 20, and is connected to the heater power supply 7 via the heater power control unit 20. The time constant means 21 is for reducing a sudden change in the control signal Tag. The time constant means 21 prevents a sudden change in the input current of the heater power supply 7 from causing a sudden change in the voltage of the AC power supply 3 and the occurrence of flicker in lighting equipment and the like. This is to prevent it.

This embodiment uses an induction heating coil 24 as a heater. In the second embodiment, the switching frequency of the heater is constant, but in this embodiment, frequency modulation is performed by voltage resonance switching. Therefore, the conduction time of the switching element is fixed, and the non-conduction time is made variable according to the temperature of the fixing roller.When the temperature of the fixing roller is lower than a predetermined value, the non-conduction time is increased, and when the temperature is high, the non-conduction time is increased. The non-conduction time is shortened to control the temperature of the fixing roller and control the input current. For this reason, the voltage applied to the switching element is input to the heater power controller 20 as a detection signal. Other operations are the same as those of the second embodiment.
Description is omitted.

[0023]

According to the first aspect of the present invention, as described above, in the present invention, the current supplied to the fixing heater via the current detecting means is controlled so that the input current of the image forming apparatus becomes a predetermined value or less. Since the control is performed, it is possible to use a heater having a large current capacity, and it is possible to provide a power control device that has a quick start-up (short warm-up time).

According to a second aspect of the present invention, the current supplied to the heater via the input current detecting means is switched at a cycle shorter than the cycle of the AC power supply, and the detection output of the input current detecting means is supplied to the heater. Since the conduction ratio of the switch element is controlled accordingly, the current supplied to the heater can be arbitrarily controlled, and the heater HT having a large current capacity can be used.

According to a third aspect of the present invention, a control circuit for controlling a current input from an AC power supply to an image forming apparatus to an output of a heater power supply in accordance with a value detected by an input current detection means is provided by a time constant means. Since the output setting signal is supplied to the heater power supply via, the sudden change in the input current is reduced, and the occurrence of flicker in the lighting equipment can be prevented.
Also, in the image forming apparatus, since the power supply to the heater can be turned on and off at any time, the temperature ripple of the fixing device is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is an input current transition diagram according to the first embodiment;

FIG. 3 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of the inside of a control circuit according to second and third embodiments of the present invention.

FIG. 6 is a diagram showing a relationship between a conduction ratio and an input current according to the second and third embodiments of the present invention.

FIG. 7 is an input current transition diagram of an example of a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Current detection means 6 Lamp power supply 7 Heater power supply 10 Fixing heater 11 Temperature control means 12 Heater temperature detection means 14 Fixing apparatus 15 Full-wave rectifier 18 Switch element 19, 24 Heating means 20 Heater power control section 21 Time constant means

Claims (3)

[Claims] 1. An input current detecting means for detecting a current input to an image forming apparatus from an AC power supply, a fixing device supplied with power via the input current detecting means, and a heater temperature for detecting a temperature of the fixing device. In an image forming apparatus having a detection unit and a temperature control unit that controls a temperature of the fixing device,
A power control device for an image forming apparatus, wherein a current supplied to a fixing heater is controlled so that an input current of the image forming apparatus becomes a predetermined value or less. 2. An input current detection means for detecting a current input from an AC power supply, and a full-wave rectification of the power supplied via the input current detection means to supply the power to a series circuit of the heating means and the switch element. In a power control device having a heater power supply, the switching element is switched at a cycle shorter than the cycle of the AC power supply, and the conduction ratio of the switching element is controlled according to the detection output of the input current detection means. Power control device. 3. An input current detection means for detecting a current input from an AC power supply to the image forming apparatus, a lamp power supply and a heater power supply driven by a power supply supplied via the input current detection means, In a power control device including a control circuit for controlling an output of a heater power supply according to a value detected by a detection means, an output setting signal is supplied from the control circuit to the heater power supply via a time constant means. A power control device characterized by the above-mentioned.