JP2016025827A - Current controller and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current controller that makes it possible for current flowing in a load to be calculated by only current detection means that detects input current before branching into the load and a power source part from an AC power source such as a commercial power source, and to provide an image forming apparatus.SOLUTION: A current controller has a current detection circuit 514 that detects input current before a heater 432 for a fixing unit 431 and a converter 505 for a power source part branch from a commercial power source 201. The phase of the conduction angle θh of a current flowing in the heater 432 is controlled so as not to overlap the conduction angle θc of current flowing in the converter 505. In such a controlled state, while a first current effect value Idetected by the current detection circuit 514 and a load are off, the effective value Iof current flowing only in the heater 432 is calculated from a second current effective value Idetected by the current detection circuit 514.SELECTED DRAWING: Figure 6

Description

  In the present invention, a current supplied from an AC power source such as a commercial power source is branched and input to a load and a power supply unit, and in particular, current flowing through the load is detected by a current detection unit that detects an input current before branching. The present invention relates to a current control device capable of calculation and an image forming apparatus using the current control device.

As a conventional image forming apparatus to which this type of current control apparatus is applied, for example, an apparatus described in Patent Document 1 is known. That is, a fixing unit having a heater to which an alternating current is supplied from a commercial power source, and a power source unit that converts an alternating voltage supplied from the commercial power source into a direct current voltage. And branching to the power supply unit.
In recent years, the current consumption of image forming apparatuses has increased with the speeding up of image forming apparatuses. On the other hand, the current values that can be consumed are limited by the Electrical Appliance and Material Safety Law and UL (American Insurer Safety Laboratory). Has been. Therefore, conventionally, an effective current value input to the entire image forming apparatus is detected, and control is performed so that the total input current input to the image forming apparatus does not exceed the limit value. In Patent Document 1, the fixing unit and other loads are controlled so that the total input current does not exceed the limit value while detecting the current of the fixing unit so that the temperature of the fixing unit does not decrease as much as possible.

JP 2012-53482 A

However, in Patent Document 1, in addition to the current detection means for detecting the effective value of the input current before branching from the commercial power supply to the fixing unit and the power supply unit, the effective value of the current flowing only to the fixing unit after branching is detected. The second current detecting means is provided to increase the cost of the apparatus.
Since the effective value of the alternating current is the square root of the root mean square value, it is difficult to extract the effective current value flowing through the fixing unit by calculation or the like with only the current detection means that detects the input current before branching. A current detecting means for detecting the current is required.
An object of the present invention is to provide a current control device and an image forming apparatus that can calculate a current flowing through a load only by a current detection unit that detects an input current before branching from an AC power source such as a commercial power source to a load and a power source unit. It is to provide.

In order to achieve the above object, the current control device of the present invention comprises:
A load supplied with AC power from an AC power source;
Phase control means for controlling the phase of the conduction angle of the alternating current flowing through the load;
A power supply unit that generates a DC voltage from an AC voltage supplied from the AC power supply;
Current detection means for detecting an effective value of an input current before branching from the AC power supply to the load and the power supply unit,
In a state where a current is passed through the load at a predetermined conduction angle by the phase control means, a first current effective value detected by the current detection means and a state in which the load is turned off by the phase control means And means for calculating an effective value of the current flowing through the load based on the second effective current value detected by the current detecting means.
The image forming apparatus according to the present invention includes:
A fixing unit having a heating element to which AC power is supplied from an AC power source, and having a heating unit for heating and fixing a toner image formed on the recording material;
Phase control means for controlling the phase of the conduction angle of the alternating current flowing through the heating element;
A power supply unit for converting an AC voltage supplied from the AC power source into a DC voltage;
Current detection means for detecting an effective value of an input current before branching from the AC power source to the fixing unit and the power source unit,
The first current effective value detected by the current detection unit and the heating unit turned off by the phase control unit in a state where a current is passed through the heating unit by the phase control unit at a predetermined conduction angle. In this state, there is provided means for calculating an effective value of the current flowing through the heating element based on the second effective current value detected by the current detection means.

  According to the present invention, the current flowing through the load can be detected only by the current detection means for detecting the input current before branching from the AC power supply to the load such as the heating element and the power supply unit, so only the current flowing through the load is detected. The current detecting means for detecting the current becomes unnecessary, and the cost can be reduced.

1 is a circuit diagram of a fixing device and a power supply unit of an image forming apparatus according to Embodiment 1 of the present invention. The circuit diagram of the power supply part of FIG. FIG. 2 is a current waveform diagram for explaining phase control of a current flowing through the heater of FIG. 1. The wave form diagram of the heater of FIG. 1, a converter, and its synthetic current. Explanatory drawing of the input waveform and output waveform of the current detection circuit of FIG. The flowchart which shows the calculation procedure of the electric current effective value of the heater of FIG. FIG. 7 is a current waveform diagram corresponding to the flowchart of FIG. 6. The graph which shows the relationship between the square value of the electric current effective value of the heater of FIG. 1, and a conduction angle. The flowchart of the starting control of the heater of FIG. The graph which shows the relationship between the conduction angle of the heater of FIG. 1, and supply electric power. The circuit diagram of the power supply part in Embodiment 2 of this invention. The flowchart which shows the calculation procedure of the electric current effective value of the heater of FIG. The current waveform figure of each part corresponding to the flowchart of FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied.

The present invention will be described in detail below based on the embodiments shown in the drawings.
[Embodiment 1]
FIG. 14 shows an example of an image forming apparatus to which the current control device of the present invention is applied.
The image forming apparatus 400 is a multifunction machine in which various optional devices such as a paper feed unit 651, a transport unit 701, a paper discharge unit 801, and an image scanner 901 are mounted on a main body 401.
The apparatus main body 401 is a color laser printer that forms toner images with four colors of yellow Y, magenta M, cyan C, and black K. The apparatus main body 401 includes four process cartridges 410 constituting an image forming unit for each color, and four scanner units 420 for exposing the photosensitive drum 305 of each process cartridge 410.
Regarding these four process cartridges 410 and scanner unit 420, Y, M, C, and K are appended to the numerals of the constituent parts in the figure, but since they are the same configuration, in the following description, Y, M , C, A will be described in general with only the numbers without subscripts.

The process cartridge 410 includes a cleaning member 306 that removes toner on the photosensitive drum 305, a charging roller 303, a developing roller 302, and a toner storage container 411, and is detachable from the apparatus main body 401. Yes.
The scanner unit 420 includes a laser unit 421 that emits laser light modulated based on an image signal, a polygon mirror 422 for scanning the laser light on the photosensitive drum 305, and an imaging lens group 424. I have. The polygon mirror 422 is driven by the scanner motor 423.

In the figure, reference numeral 405 denotes a paper feed roller, which transports the recording paper 32 as a recording material fed from the paper feed cassette 402 by the pickup roller 404. Reference numeral 406 denotes a pair of paper feed rollers 405, a retard roller for preventing double feeding of the recording paper 32, and reference numeral 407 denotes a registration roller pair. Reference numeral 409 denotes an electrostatic attraction / conveyance transfer belt (hereinafter referred to as ETB) which electrostatically attracts the recording paper 32 and conveys it to each process cartridge 410. Reference numeral 430 denotes a transfer roller that transfers the toner image formed on each photosensitive drum 305 onto the recording paper 32.
On the other hand, reference numeral 431 denotes a fixing device as a fixing unit, which includes a fixing roller 433 provided with a heater 432 as a heating element, and a pressure roller 434 pressed against the fixing roller 433. A pair of fixing paper discharge rollers 435 for conveying the recording paper 32 from the nip portion between the fixing roller 433 and the pressure roller 434 is provided. The fixing roller 433 including the heater 432 and the pressure roller 434 constitute a heating unit that heats and fixes the toner image formed on the recording paper 32.

Reference numeral 451 denotes a main motor that drives each process cartridge 410, 452 denotes an ETB motor that drives the ETB 409, and 453 denotes a fixing motor that drives the fixing device 431, each of which uses a DC motor such as a DC brushless motor.
Reference numeral 201 denotes an engine control unit which includes a microcomputer (not shown) and various input / output control circuits (not shown). Reference numeral 505 denotes a low-voltage power supply (power supply unit), which is a later-described converter that converts an AC voltage input from the commercial power supply 202 into a DC voltage.
A video controller 440 receives image data sent from a host computer 441 such as a personal computer, expands the image data into bitmap data, and generates an image signal for image formation.

Next, an image forming operation of the apparatus main body 401 will be described.
First, image data is transmitted from the external host computer 441 to the video controller 440. The video controller 440 transmits a PRINT signal instructing the engine control unit 201 to start image formation, and converts the received image data into bitmap data. The engine control unit 201 that has received the PRINT signal starts driving the scanner motor 423, the main motor 451, the ETB motor 452, and the fixing motor 453 at a predetermined timing. At the same time, the pickup roller 404, the paper supply roller 405, and the retard roller 406 of the paper supply unit are driven to feed the recording paper 32 from the paper supply cassette 402. The recording paper 32 is conveyed to the registration roller pair 407 and temporarily stops.
Further, the ambient temperature of the apparatus main body 401 is detected by a temperature detection sensor 324 disposed near the paper feed roller 405, and the engine control unit 201 corrects the image forming conditions selected according to the detection result.
Next, the laser unit 421 is ON / OFF controlled in accordance with the image signal depending on the bitmap data, and the photosensitive drum 305 is charged to a predetermined potential by the charging roller 303 via the polygon mirror 422 and the imaging lens group 424. An electrostatic image is formed on the surface. Thereafter, a toner image is formed by the developing roller 302. This toner image forming operation is executed for each electrostatic image of yellow Y, magenta M, cyan C, and black K at a predetermined timing.

On the other hand, the recording paper 32 temporarily stopped by the registration roller pair 407 is re-fed to each process cartridge 410 by the ETB 409 at a predetermined timing according to the toner image forming operation. The toner images on the photosensitive drums 305 are sequentially transferred onto the recording paper 32 by the transfer roller 430 to form a color toner image.
The toner image formed on the recording paper 32 is further conveyed to a fixing device 431, heated and pressed by a fixing roller 433 and a pressure roller 434 heated to a predetermined temperature, and fixed on the recording paper 32. The paper is discharged out of the apparatus main body 401 by a pair of paper discharge rollers 435.

Next, the optional device described above will be briefly described.
The transport unit 701 transports the recording paper 32 discharged from the apparatus main body 401 to the paper discharge unit 801 and includes a transport motor 702 that drives the transport roller pairs 703 and 704.
The paper discharge unit 801 is a unit that sorts the recording paper 32 discharged from the apparatus main body 401 into a paper discharge tray 806 every predetermined number of sheets, and includes a transport motor 802 that drives a pair of transport rollers 804 and 805, and a paper discharge tray 806. And a lifting motor 803 that lifts and lowers.

  The image scanner 901 includes a document transport unit 930 and a document reading unit 931, and the document transport unit 930 is provided with a document transport motor 902 that transports the document 932. The document reading unit 931 includes an exposure unit 904 including an exposure unit 905 and a mirror 906, a fixed reflection device 907 and a light receiving device 910 including mirrors 908 and 909, and a scanner drive that horizontally moves the exposure unit 904. A motor 903 is provided. A controller unit 940 controls the operation of the image scanner 901 and converts a signal received by the light receiving device 910 into image data.

In the operation of the image scanner 901, after the document 932 is set on the document transport unit 930, first, the copy mode or the scanner mode for converting the read data into an electronic file is selected from a panel (not shown).
When the copy mode is selected, the document transport motor 902 transports the document 932 to the document reading unit 931 at a predetermined timing. Then, the exposure unit 904 is horizontally moved by the scanner driving motor 903, and the light of the exposure unit 905 is irradiated onto the document 932. Reflected light from the document 932 is received by the light receiving device 910 via the mirror 906 and the mirrors 908 and 909 in the reflecting means 907, and the received light signal is transmitted to the controller unit 940. The controller unit 940 converts the received signal into image data and transmits it to the video controller 440. Thereafter, image formation is performed by the host computer 441 in the same operation as image formation.
On the other hand, when the scanner mode is selected, the controller unit 940 converts the received signal into an electronic file in a predetermined file format and transmits it to the host computer 441 via the video controller 440.

Next, the current control of the input current of the image forming apparatus, which is a feature of the present invention, will be described.
FIG. 1 is a circuit block diagram illustrating in detail a converter 505 that is a low-voltage power source (power source unit) of the apparatus main body 401 and a control unit of the fixing device 431.
That is, the fixing device 431 provided with the heater 432 as a load supplied with AC power from the commercial power source 202 that is an AC power source, and phase control means for controlling the phase of the conduction angle of the AC current flowing through the heater 432. An engine control unit 201. Further, converter 505 as a power supply unit that generates a DC voltage from an AC voltage supplied from commercial power source 202, and current detection that detects an effective value of an input current before branching from commercial power source 202 to heater 432 and converter 505. And a current detection circuit 514 as means.

In the figure, reference numeral 512 denotes a current transformer provided on a line before branching from the inlet 501 to the heater 432 and the converter 505, and reference numeral 513 denotes a resistor that converts a current flowing through the current transformer 512 into a voltage.
Reference numeral 521 denotes an interlock switch that opens and closes in conjunction with a door (not shown) of the apparatus main body 401, and reference numeral 522 denotes a relay that outputs a switch ON / OFF signal. Also, 52
Reference numeral 3 denotes a triac, 524, 525, 527 and 531 are resistors, 526 is a phototriac coupler, 528 is a transistor, 529 is a thermoswitch which is a temperature protection element, and 530 is a thermistor which detects the temperature of the heater 432.

Next, phase control of the fixing device 431 will be described with reference to FIG. 3 in addition to FIG.
The engine control unit 201 detects the divided voltage of the thermistor 530 and the resistor 531 via the A / D1 port of the engine control unit 201. The thermistor 530 has a characteristic that the resistance value decreases as the temperature increases, and the engine control unit 201 detects the temperature of the heater 432 by reading the voltage of the A / D1 port and controls the fixing temperature.
An AC current from the commercial power source 202 is supplied to the heater 432 via the relay 522, the triac 523, and the thermo switch 529 (see FIG. 3A). This supply current is phase-controlled by a control signal from the engine control unit 201.

The engine control unit 201 uses the zero cross signal input from the zero cross detection circuit 515 to the IN1 port of the engine control unit 201 to detect the timing at which the commercial power source 202 switches between positive and negative (see FIG. 3B). The engine control unit 201 outputs High from the OUT1 port and turns on the transistor 528 after a predetermined time (Toff) has elapsed since the rising and falling of the zero cross signal were detected (hereinafter referred to as delay time Toff) (FIG. 3). (See (c)). When the transistor 528 is turned on, a current flows to the phototriac coupler 526 through the resistor 527, and the phototriac coupler 526 is turned on. When the phototriac coupler 526 is turned on, a gate current flows to the triac 523 serving as a switching element via the resistors 524 and 525, the triac 523 is turned on, and a current flows to the heater 432 to generate heat (FIG. 3D). reference).
The triac 523 is turned off at the timing of the next zero cross, that is, the gate current is zero. As a result, as shown in FIG. 3D, the waveform of the current flowing through the heater 432 has a shape in which the waveform is cut off to zero during the delay time Toff every half cycle of the sine wave. The conduction angle θh is the phase angle from the ON phase at which the delay time Toff elapses to ON to the next zero cross OFF time. The engine control unit 201 controls the heater 432 to a predetermined temperature by controlling the delay time Toff according to the voltage input to the A / D1 port, that is, controlling the conduction angle θh.

Subsequently, the converter 505 will be described in detail with reference to FIG.
Converter 505 generates 3.3V and 24V DC voltages. The AC voltage input from the commercial power source 202 is full-wave rectified by the diode bridge 502 and then smoothed by the capacitor 503. Thereafter, switching is performed by the power supply control IC 510, and power is transmitted to the secondary side via the transformer 504.
The pulse wave generated on the secondary side of the transformer 504 is rectified and smoothed by the diode 506 and the capacitor 507 to generate DC 24V. The secondary voltage is detected and error amplified by the shunt regulator 508 and fed back to the power supply control IC 510 by the photocoupler 509.
For example, the scanner motor 423, the main motor 451, the ETB motor 452, and the fixing motor 453 of the apparatus main body 401 are driven by the DC 24V. Further, the conveyance motor 702 of the conveyance unit 701, which is an optional device, the conveyance motor 802 and the elevation motor 803 of the paper discharge unit 801, and the document conveyance motor 902 and the scanner drive motor 903 of the image scanner 901 are driven.
Further, the converter 505 includes a choke converter unit 564 that generates 3.3 V from DC 24 V. The 3.3 V generated by the choke converter unit 564 is supplied to the engine control unit 201, for example.

Next, the current detection circuit 514 will be described with reference to FIGS.
4A shows a current waveform flowing through the heater 432, FIG. 4B shows a current waveform flowing through the converter 505, and FIG. 4C shows a current waveform flowing through the current transformer 512. The waveform of the current flowing through the current transformer 512 is a combined current of the current flowing through the heater 432 (FIG. 4A) and the converter 505 (FIG. 4B). The combined current flows through the current transformer 512 and is converted into a current voltage by the resistor 513. Since the current flowing through the converter 505 flows when the input voltage becomes higher than the voltage between the terminals of the smoothing capacitor 503, the conduction angle θc is in a narrow range.

The current detection circuit 514 has a function of square integration of the input voltage (Vin), and integrates a multiplier 516 that squares the voltage (Vin) input from the current transformer 512 and an output from the multiplier 516. The integrator 517 is configured. That is, as shown in FIGS. 5A and 5B, the current detection circuit 514 starts the square integration of the voltage (Vin) from the rise of the input zero-cross detection circuit 515, and the zero-cross detection circuit 515 rises. End with a fall.
Thereafter, as shown in FIG. 5C, the engine control unit 201 reads the output value (Vad) from the current detection circuit 514 at the A / D2 port after a predetermined time (Tad) from the falling edge.
The current detection circuit 514 holds the integrated value until the integrated value is reset to 0 V after a predetermined time (Tdis) from the falling edge. The engine control unit 201 obtains the square value of the effective value of the voltage by dividing the output value (Vad) read at the A / D2 port by the time (Tfreq) of one cycle (see Equation 1). Converts the square value of the effective value to the square value of the effective value of the current.

このように、エンジン制御部２０１は、電流検知回路５１４の出力から、装置本体４０１に流入する電流の実効値を検知し、プリント中の電流が商用電源２０２の供給可能電流を超えないよう制御する。この電流検知回路５１４で検知される入力電流は、定着器４３１とコンバータ５０５に流れる電流の合成電流である。

As described above, the engine control unit 201 detects the effective value of the current flowing into the apparatus main body 401 from the output of the current detection circuit 514, and performs control so that the current during printing does not exceed the current that can be supplied from the commercial power source 202. . The input current detected by the current detection circuit 514 is a combined current of currents flowing through the fixing device 431 and the converter 505.

Next, a procedure for calculating a current flowing only in the heater 432 that is a load, which is a feature of the present invention, will be described.
That is, the first current effective value (I ₁ ) is detected by the current detection circuit 514 in a state where a current is passed through the heater 432 at a predetermined conduction angle θh by the engine control unit 201. In addition, the current effective value (I ₂ ) is detected by the current detection circuit 514 in a state where the heater 432 is turned off by the engine control unit 201. From these first current effective value (I ₁ ) and second current effective value (I ₂ ), the effective value of the current flowing through the heater 432 is calculated.
In this example, the predetermined conduction angle θh does not overlap with the phase of the conduction angle θc of the current flowing through the converter 505, that is, the phase of the conduction angle θh of the current flowing through the heater 432 is equal to the current flowing through the power supply unit. Control is performed so that the phase is different from the phase of the conduction angle θc. Then, by calculating the difference between the square value (I ₁ ² ) of the first current effective value and the square value (I ₂ ² ) of the ^second current effective value, the effective value of the current flowing through the heater 432 is calculated. The square value is obtained.

FIG. 6 shows a specific flowchart for calculating the current flowing only in the heater 432 in the engine control unit 201. This flowchart is executed when the image forming apparatus is on standby.
First, in step 601, the energization to the heater 432 is OFF, and the current that flows only to the converter 505, that is, the second current effective value (I ₂ ) is detected from the output value from the current detection circuit 514. The output of the current detection circuit 514 is a square integral value of a voltage corresponding to a half-wave current. The square integral value of this voltage is read into the engine control unit 201, and the engine control unit 201 uses the second current effective value. To the square integral value (I ₂ ² ).
Next, in step 602, the triac 523 is controlled to a predetermined conduction angle θh, in this example, 30 °. In step 603, the first effective current value (I ₁ ) is detected from the output value from the current detection circuit 514 in a state where the heater 432 is energized. Also in this case, the output of the current detection circuit 514 is a square integral value of a voltage corresponding to a half-wave current, and the square integral value of this voltage is read into the engine control unit 201, and the engine control unit 201 performs the first integration. Is converted to the square integral value (I ₁ ² ) of the current effective value of.

  In this step 603, the input current detected by the current detection circuit 514 is the secondary that flows to the current transformer 512 of the total input current before branching to the heater 432 and the converter 505, as shown in FIG. Current. This total input current is a value obtained by adding the currents flowing through the heater 432 (FIG. 7A) and the converter 505 (FIG. 7B). In the present embodiment, the conduction angle θh of the heater 432 (FIG. 7A) is set to 30 °, and control is performed so as not to overlap with the phase of the conduction angle θc of the input current flowing through the converter 505 (FIG. 7B). ing. The conduction angle θh of the heater 432 is not limited to 30 °, and may be in a range that does not overlap with the phase of the conduction angle θc of the current flowing through the converter 505.

Next, in step 604, the value of the square value (I ₁ ² ) of the first current effective value detected in step 603 is stored in a memory (not shown) of the engine control unit 201. Step 60
5, it is determined whether or not a current of a plurality of sine wave periods, in this example, three periods (three waves) is detected.
Note that the timing at which the engine control unit 201 performs A / D conversion of the output from the current detection circuit 514 is T1, T2, and T3 as shown in FIG. 7D, and Tad from the trailing edge of the zero-cross detection circuit 515. What is later is as described in FIG.
If it is determined in step 605 that the current effective values for the three waves have been stored in the memory (not shown) of the engine control unit 201, the average value for the three waves is calculated in step 606, and the result (I ₁ ² ) and stored in a memory (not shown) of the engine control unit 201.

Thereafter, in step 607, the second current effective value (effective) when the heater 432 is turned off from the square value (I ₂ ² ) of the first effective current value when the control current of the conduction angle θh is supplied. The value (I ₃ ² ) obtained by subtracting the square value (I ₁ ² ) of the value) is calculated. This calculation result is stored in a memory (not shown) of the engine control unit 201 as a square value of the effective value of the fixing current (I ₃ ) that has flowed only to the heater 432 of the fixing device 431.
The graph of FIG. 8 shows the relationship between the square value of the effective current value flowing through the heater 432 and the conduction angle between the half waves of the sine wave. In FIG. 8, the solid line is the square value (I ₃ ² ) of the effective current value obtained by calculation according to the flowchart of FIG. 6, and the broken line is the square value of the actual effective current value flowing through the heater 432.
When the conduction angle θh of the current flowing through the heater 432 is in the range of 80 ° or less, the broken line and the solid line coincide with each other because the conduction angle θc of the current flowing through the converter 505 does not overlap. Therefore, the effective current value (I ₃ ) flowing through the heater 432 can be accurately obtained by calculation.
The input current flowing through the converter 505 is a current that flows in a range where the input voltage exceeds the terminal voltage of the smoothing capacitor. However, this conduction angle is not limited to 80 °, but is determined by the capacity of the smoothing capacitor of converter 505 and the like.

Next, startup control of the fixing device 431 will be described with reference to FIG.
In the start-up control, an effective current value I ₄ necessary for the start-up control of the heater 432 is set in advance when the temperature of the fixing device 431 is raised to a predetermined temperature. Then, a ratio between the square value I ₃ ² of the effective current value that flows only through the heater 432 calculated by the flow of FIG. 6 and the square value I ₄ ² of the effective current value necessary for the start-up control is calculated. The conduction angle of the current required for the start-up control is obtained from the ratio of the supplied power corresponding to this ratio, and the current flowing through the heater 432 is controlled by the engine control unit 201 at the obtained conduction angle.
The electric power supplied to the heater 432 is proportional to the square value of the effective current value of the heater current, and if the ratio of the supplied power corresponding to the effective current value at the start-up is known, the conduction angle to be controlled is determined. .

FIG. 9 shows a specific flowchart of the start-up control of the fixing device 431.
In step 901, upon receiving a PRINT signal from the video controller 440, the engine control unit 201 starts image formation control. In step 902, according to the flowchart of FIG. 6, the value of the square value (I ₃ ² ) of the effective value of the current flowing only through the heater calculated during standby is read from a memory (not shown). In step 903, the square value (I ₄ ² ) of the effective value of the startup current necessary for starting up the heater 432, which is stored in advance in a memory (not shown), is read from the memory (not shown).
Next, in step 904, the ratio (PS) of the supplied power corresponding to the square value (I ₄ ² ) of the effective value of the start-up current is calculated by the mathematical formula given in Equation 2 and stored in a memory (not shown). To do.
As shown in the flowchart of FIG. 6, the square value (I ₃ ² ) of the effective current value that flows only through the heater 432 is the square value of the effective current value when the heater 432 is turned on at 30 °. When the supplied power at the phase angle of 180 and the phase angle of 100 is 100, the ratio of the supplied power of the fixing current at the conduction angle of 30 ° corresponds to 3.02. From this ratio, the ratio (PS) of the supplied power corresponding to the square value (I ₄ ² ) of the current effective value of the startup current is obtained.

Next, in step 905, from the graph of FIG. 10 showing the relationship between the ratio PS of the supplied power obtained in step 904 and the conduction angle (θh), the conduction angle required for flowing the current having the effective current value I ₄ ( θh) is obtained.
Subsequently, in step 906, as described with reference to FIG. 3, the heater 432 is controlled by the conduction angle (θh) obtained in step 905, and in step 907, the temperature of the heater 432 is set to the fixing possible temperature (Temp1). ) Monitor the rise to -50 ° C.
If it is determined in step 907 that the temperature of the heater 432 has risen to the fixable temperature (Temp1) −50 ° C., the engine control unit 201 switches the temperature control of the heater 432 to PID control in step 908. Then, the temperature of the heater 432 is controlled to be Temp1 while monitoring the value of the A / D1 port.

If it is determined in step 907 that the temperature of the heater 432 has not risen to the fixable temperature (Temp1) −50 ° C., the process returns to step 906 and the heater 432 is kept ON at the conduction angle θh.
Thereafter, if it is determined in step 909 that the temperature of the heater 432 has reached Temp1, image formation is started in step 910. If it is determined in step 909 that the temperature of the heater 432 has not reached Temp1, the process returns to step 908 to control the temperature of the heater 432 to be Temp1.

As described above, according to the first embodiment, the current flowing only to the heater 432 is calculated by one current detection circuit 514 attached to detect the total input current input to the apparatus main body 401. It can be obtained.
Furthermore, when the effective current value is set during start-up control, etc., the conduction angle of the current value to be controlled is obtained by calculation from the relationship between the calculated effective current value and the conduction angle, and the control current is accurately determined. Can be controlled.

[Embodiment 2]
Next, a second embodiment of the present invention will be described.
In the second embodiment, the control for obtaining the effective value of the current flowing through the heater 432 is described in the configuration having the power factor improving power supply unit provided with the power factor improving circuit. In addition, since the principal part structure in this Embodiment 2 is the same as Embodiment 1, the same code | symbol is attached | subjected about the same component and the description is abbreviate | omitted.

First, converter 505 in the present embodiment will be described with reference to FIG.
The converter 505 is divided into a 3.3V converter unit 560 and a 24V converter unit 562 as a power factor improving power supply unit. The AC voltage input from the commercial power source 202 is supplied to the 3.3V converter unit 560 and the 24V converter unit 562. Entered.
The AC voltage input to the 3.3V converter unit 560 is full-wave rectified by the diode bridge 502 and then smoothed by the capacitor 503. Thereafter, switching is performed by the power supply control IC 510, and power is transmitted to the secondary side via the transformer 574.
The pulse wave generated on the secondary side of the transformer 574 is rectified and smoothed by the diode 566 and the capacitor 567 to generate DC 3.3V. The secondary voltage is detected and error amplified by the shunt regulator 568 and fed back to the power supply control IC 510 by the photocoupler 509. The generated 3.3V is supplied to the engine control unit 201 and the like.

  The AC voltage input to the 24V converter unit 562 is full-wave rectified by the diode bridge 541 and then input to the power factor correction circuit 561. The power factor correction circuit 561 includes a coil 548, a diode 549, a capacitor 552, a MOSFET 551, a control IC 550, and a resistor 563, and converts the input AC voltage after full-wave rectification into a DC voltage of 400V. As a specific circuit operation, first, the voltage after full-wave rectification is switched by the MOSFET 551 via the coil 548. When the MOSFET 551 is OFF, the energy stored in the coil 548 is regenerated by the diode 549, and a voltage of 400V is generated in the capacitor 552. The control IC 550 controls the On Duty of the MOSFET 551 according to the voltage of the capacitor 552 input via the resistor 563, and controls the voltage of the capacitor 552 to a predetermined value.

The DC 400V generated by the power factor correction circuit 561 is switched by the power supply control IC 558, and power is transmitted to the secondary side via the transformer 553. The pulse wave generated on the secondary side of the transformer 553 is rectified and smoothed by the diode 554 and the capacitor 555 to generate DC 24V. Note that the secondary voltage is detected and error amplified by the shunt regulator 556 and fed back to the power supply control IC 558 by the photocoupler 557.
The 24V converter unit 562 is provided with a triac 559 serving as a power cut-off unit that cuts off the power supply from the commercial power source 202, and is ON / OFF controlled by the engine control unit 201. A signal output from the OUT2 port of the engine control unit 201 is connected to the base terminal of the transistor 546 via the resistor 544. When the OUT2 port outputs High, the transistor 546 is turned on, a current flows to the phototriac coupler 545 through the resistor 547, and the phototriac coupler 545 is turned on. When the phototriac coupler 545 is turned on, a gate current flows to the triac 559 via the resistors 542 and 543, and the triac 559 is turned on. Conversely, when the OUT2 port outputs Low, the triac 559 is turned OFF.

For example, the engine control unit 201 stops the 24V converter unit 562 by turning off the triac 559 in the energy saving mode, thereby realizing a further low power consumption state.
Next, the effective value detection control of the current flowing through the heater 432 performed by the engine control unit 201 during standby of the apparatus main body 401 will be described with reference to the flowchart of FIG. 12 and FIG. In the present embodiment, the effective value of the current flowing through the heater 432 is detected using a current detection circuit 514 attached to the point where the combined current of the heater 432 and the converter 505 flows.

As shown in FIG. 13 (d), the current flowing from the commercial power source 202 to the apparatus main body 401 includes a heater 432 (FIG. 13 (c)), a 24V converter unit 562 (FIG. 13 (a)), and a 3.3V converter unit. 560 (FIG. 13B) is a combined current that flows.
First, in step 1201, the engine control unit 201 changes the OUT2 port to low to turn off the triac 559. In step 1202, the current detection circuit 514 detects the second current effective value (I ₂ ² ). Since the second current effective value (I ₂ ² ) detected in step 1202 is OFF as shown in period 1 of FIG. 13, the energization of the heater 432 and the 24V converter unit 562 is OFF, and the 3.3V converter unit The effective current value is only 560.
Next, in step 1203, the triac 523 is turned on at a conduction angle θh, in this example, 30 °, and in step 1204, a current effective value in a state where the heater 432 is energized is detected by the current detection circuit 514.

In step 1204, the current detected by the current detection circuit 514 includes the heater 432 (FIG. 13C) and the 3.3V converter 560 (FIG. 13B) as shown in period 2 of FIG. )).
In step 1205, the first current effective value (I ₁ ) detected in step 1204 is stored in a memory (not shown) of the engine control unit 201, and whether or not the current effective value for three waves is detected in step 1206. to decide. Note that the timing at which the engine control unit 201 performs A / D conversion of the output from the current detection circuit 514 is T1, T2, and T3 as shown in FIG. 13 (e), and Tad from the fall of the zero-cross detection circuit 515. What is later is as described with reference to FIG.

If it is determined in step 1206 that the effective current values for three waves can be stored in the memory (not shown) of the engine control unit 201, the OUT2 port is changed to high in step 1207, the triac 559 is turned on, and the 24V converter unit 562 is turned on. Restart the power supply to.
Thereafter, in step 1208, an average value for three waves is calculated, and the result is stored in a memory (not shown) of the engine control unit 201 as a square value (I ₁ ² ) of the first current effective value. Then, _I ^{2 2} calculates the value _I ^{3 2} minus from _I ^{1 2} in step 1209 and stored in the memory (not shown) of the engine control unit 201.

Note that the power supply to the 24V converter unit 562 is cut off during the period 1 and period 2 in FIG. 13 during the processing from step 1202 to step 1206. But,
The 24V converter unit 562 can continue to operate by the energy stored in the capacitor 552, and 24V is not cut off during the control.
As described above, even if the converter 550 has the power factor correction circuit 561, the heater is used by using the current detection circuit 514 by temporarily shutting off the power supply to the power factor improvement circuit 561. The effective current value that flows only to 432 can be calculated.

In each of the above embodiments, the difference between the square value of the first current effective value square value I ₁ ² and the second current effective value I ₂ ² is obtained to determine the effective value of the current flowing through the heater 432. Although the square value I ₃ ² is calculated, it is not limited to the subtraction of the square value. For example, even if the sum and difference of the first current effective value I ₁ and the second current effective value I ₂ are multiplied, the square value I ₃ ² of the effective value of the current flowing through the heater 432 is calculated. Can do.
In each of the above embodiments, when detecting the first current effective value I ₁ , the phase of the conduction angle θh of the current flowing through the heater 432 does not overlap the conduction angle θc of the current flowing through the converter 505. Although they are controlled, they may overlap in some cases. For example, the error data of FIG. 8 can be stored in advance, and the error can be corrected according to the conduction angle.
In the above-described embodiment, the commercial power source 201 is described as an example of the AC power source. However, the AC power source is not limited to the commercial power source, and can be applied to, for example, a case where an AC power source such as private power generation is used. is there.
Further, the image forming apparatus is not limited to the multi-function machine such as the image forming apparatus shown in FIG. 14, and is widely applied to an image forming apparatus having a fixing unit equipped with a heater such as a fax machine, a printer, and a copying machine. Is possible.
Furthermore, the apparatus to which the present invention is applied is not limited to an image forming apparatus, but is widely used in apparatuses having a circuit configuration in which an alternating current such as a commercial power supply is branched and input to a converter of a load and a power supply unit. Can be applied. Further, the load is not limited to the heater, and can be applied to various electric loads whose phases are controlled.

201 Engine control unit (phase control means)
202 Commercial power supply (AC power supply)
431 Fixing device (fixing part)
432 Heater (heating element)
505 Converter (power supply)
514 Current detection circuit (current detection means)
515 Zero Cross Detection Circuit 561 Power Factor Improvement Circuit 562 24V Converter Unit (Power Factor Improvement Power Supply Unit)
559 Triac (power cutoff means)
I ₁ First current effective value I ₂ Second current effective value θh Conduction angle of current flowing in the heater 432 θc Conduction angle of current flowing in the converter 505

Claims (11)

A load supplied with AC power from an AC power source;
Phase control means for controlling the phase of the conduction angle of the alternating current flowing through the load;
A power supply unit that generates a DC voltage from an AC voltage supplied from the AC power supply;
In a current control device comprising: current detection means for detecting an effective value of an input current before branching from the AC power supply to the load and the power supply unit;
In a state where a current is passed through the load at a predetermined conduction angle by the phase control means, a first current effective value detected by the current detection means and a state in which the load is turned off by the phase control means And a means for calculating an effective value of the current flowing through the load based on the second effective current value detected by the current detecting means.   2. The first effective current value is detected by controlling the phase of the conduction angle of the current flowing through the load to be different from the phase of the conduction angle of the current flowing through the power supply unit by the phase control unit. Current control device.   The square value of the effective value of the current flowing through the load is calculated by calculating a difference between a square value of the first effective current value and a square value of the second effective current value. The current control device described. Having zero-cross detection means for detecting a zero-cross of an AC voltage supplied from the AC power source;
4. The current control device according to claim 1, wherein the phase control unit controls a phase of a conduction angle of a current flowing through the load based on an output from the zero cross detection unit. 5. The first current effective value is an average value of values detected over a plurality of cycles.
The current control device according to any one of Items 4 to 4. The power supply unit includes a power factor correction power supply unit that generates a DC voltage via a power factor correction circuit, and a power cut-off unit that cuts off power supply from the commercial power supply,
6. The current control device according to claim 1, wherein, when calculating an effective current value flowing through the load, the power interrupting unit interrupts power supply to the power factor improving power supply unit. 7.   The power supply to the power factor improvement power supply unit is cut off from the power cut-off means within a time range in which the DC voltage generated through the power factor improvement circuit of the power factor improvement power supply unit does not decrease. The current control device according to claim 6. A fixing unit having a heating element to which AC power is supplied from an AC power source, and having a heating unit for heating and fixing a toner image formed on the recording material;
Phase control means for controlling the phase of the conduction angle of the alternating current flowing through the heating element;
A power supply unit for converting an AC voltage supplied from the AC power source into a DC voltage;
An image forming apparatus comprising: a current detection unit that detects an effective value of an input current before branching from the AC power source to the fixing unit and the power source unit;
8. An image forming apparatus, wherein the current control device according to claim 1 is applied to calculation of an effective current value flowing through the heating element.   The image forming apparatus according to claim 8, wherein an effective value of a current flowing through the load is calculated during standby of the image forming operation.   When the temperature of the fixing unit is raised to a predetermined temperature, a current effective value necessary for the start-up control of the heating element is set in advance, and is calculated from the first current effective value and the second current effective value. Necessary for start-up control by calculating the ratio between the square value of the effective current value that flows only to the generated heating element and the square value of the effective current value necessary for the start-up control, and from the ratio of the supplied power corresponding to this ratio The image forming apparatus according to claim 8, wherein a current conduction angle is obtained, and the current flowing through the heating element is controlled by the phase control unit at the obtained conduction angle.   The image according to any one of claims 8 to 10, wherein an optional device including a load driven by a DC voltage generated by the power supply unit is attached to the apparatus main body including the fixing unit. Forming equipment.

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