JPH1055122A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a flickering noise caused by the fluctuation of a power supply voltage by switching the rectification output of a rectifier means supplied to a heating/fixing means, at a frequency higher than that of a primary AC. SOLUTION: The output of an AC is rectified by a rectifier diode 106 and a capacitor 107, after a filter 102. The turning on/off of the ceramic heater 121 of a fixing unit 120 are controlled by a switching element 108. This switching element 108 is driven by a fixing unit control part 103 and a waveform rectified by the diode 106 becomes an ON or OFF state at a switching cycle having the frequency higher than that of the input of the AC. The fixing unit control part, 103 outputs an RDY signal for informing an operator that printing is possible to an engine controller 130, when the ceramic heater 121 reaches a desired temp., based on temperature detection information from a thermistor 122.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus characterized by fixing means for an electrophotographic process using a photosensitive member.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. FIG. 1 is a cross-sectional view of an image recording apparatus, showing a case of a laser printer.

A laser printer main body 100 (hereinafter referred to as main body 1)
00) has a cassette 2 for storing the recording paper S, a cassette paper presence / absence sensor 3 for detecting the presence or absence of the recording paper S in the cassette 2, and a cassette size sensor 4 (plurality) for detecting the size of the recording paper S in the cassette 2. And a paper feed roller 5 for feeding out the recording paper S from the cassette 2.

A recording paper S is located downstream of the paper feed roller 5.
Are provided synchronously.
An image forming unit 8 that forms a toner image on the recording paper S based on the laser beam from the laser scanner unit 7 is provided downstream of the registration roller pair 6.

Further, a fixing unit 120 for thermally fixing the toner image formed on the recording paper S is provided downstream of the image forming unit 8, and a paper conveying state of a paper discharge unit is provided downstream of the fixing unit 120. , A discharge roller 11 for discharging the recording paper S, and a loading tray 12 for loading the recording paper S on which recording has been completed.

The laser scanner unit 7 outputs an image signal (image signal VD) sent from an external device 31 described later.
O), a laser unit 13 that emits a laser beam modulated based on O), a polygon motor 14 for scanning the laser beam from the laser unit 13 onto a photosensitive drum 17, which will be described later, an imaging lens group 15, a folding mirror 16 And the like.

The image forming section 8 includes a photosensitive drum 17, a primary charging roller 19, a developing device 20, a transfer charging roller 21, and a cleaner 2 necessary for a known electrophotographic process.
2 and so on. The fixing device 120 includes a fixing film 123, a pressure roller 124, a ceramic heater 121 provided inside the fixing film, and a thermistor 122 for detecting a surface temperature of the ceramic heater.

The main motor 23 is connected to the paper feed roller 5.
, A driving force is applied to the registration roller pair 6 via a registration roller 25. Further, each unit of the image forming unit 8 including the photosensitive drum 17, a fixing device 120, and a paper discharge The driving force is also given to the roller 11.

Reference numeral 130 denotes an engine controller, which includes a laser scanner unit 7, an image forming unit 8, and a fixing unit 120.
Controls the electrophotographic process, and controls the conveyance of the recording paper in the main body 100.

Reference numeral 27 denotes a video controller, which is a general-purpose interface (such as Centronics, RS232C) 30 with an external device 31 such as a personal computer.
The image information sent from the general-purpose interface is expanded into bit data, and the bit data is converted to a VDO signal by the engine controller 130.
Sent to

In the conventional ceramic heater control, the temperature of the ceramic heater 121 is detected by the thermistor 122 and the triac is driven by the engine controller 130 to control the power supply to the ceramic heater 121. Further, the ON / OFF control of the ceramic heater is performed by controlling the wave number of the commercial power supply.

[0012]

Conventionally, for driving a ceramic heater, the wave number of a commercial power supply has been controlled using a triac. However, in this method, when the image forming apparatus becomes a high-speed machine, the power consumption of the fixing device increases, so that the amount of change in current between ON and OFF increases, and the influence of flicker noise caused by power supply voltage fluctuations occurs. There is a problem that it cannot be ignored.

Further, it has been more difficult to make the fixing device universally applicable regardless of the power supply frequency.

An object of the present invention is to provide an image forming apparatus which solves the above-mentioned problems.

[0015]

According to a first aspect of the present invention, there is provided a rectifying unit for rectifying a primary AC power supply and supplying the rectified primary AC power to a heat fixing unit for fixing an image on a recording medium. Switching means for switching the rectified output of the rectifying means to be supplied to the heat fixing means at a frequency higher than the primary alternating current; temperature detecting means for detecting the temperature of the heat fixing means; and detection by the temperature detecting means. Power control means for controlling the switching means based on the result to control the power consumption of the heat fixing means.

According to a second aspect of the present invention, a first aspect is provided.
In the power control means, an error detection means for detecting an error between a detection result from the temperature detection means and a reference value, a triangular wave generation means for generating a triangular wave of a frequency higher than the primary AC, A comparison unit compares the error detection output from the error detection unit with the triangular wave from the triangular wave generation unit and supplies the output as a control output to the switching unit.

Furthermore, the invention according to claim 3 is characterized in that, in claim 2, the reference value is variable.

Further, according to a fourth aspect of the present invention, in any one of the first to third aspects, the heating and fixing means has a ceramic heater.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the voltage control means of the low-voltage power supply circuit for generating a secondary circuit voltage from the primary AC and the power control means are provided. It is characterized by having a drive power supply for supplying power in common.

According to a sixth aspect of the present invention, in the fifth aspect, the low-voltage power supply circuit is a switching regulator, and an auxiliary winding provided in a switching transformer of the switching regulator is connected to an input of the drive power supply. It is characterized by.

According to a seventh aspect of the present invention, in the fifth aspect, the low-voltage power supply circuit has a DC-DC converter, and the voltage control means and the voltage control means are shared by the DC-DC converter. Power is supplied.

The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the voltage detection means for detecting the voltage of the primary AC power supply, and the power supply based on a detection result of the voltage detection means. Changing means for changing the control condition of the control means.

Further, the invention according to claim 9 is characterized in that, in claim 8, the control condition is at least one of an ON time and an OFF time of the switching means.

According to a tenth aspect of the present invention, in any one of the fifth to seventh aspects, a voltage detecting means for detecting a voltage of the primary AC power supply; Changing means for changing the control condition of the control means.

According to the present invention, the primary AC input is rectified,
By performing high-frequency switching of the heating and fixing unit using a switching unit such as an FET or an IGBT, flicker noise is reduced.

The ON / OF of the switching means
By changing the F duty, it is easy to cope with the universalization of the fixing device.

Further, when the switching control is performed by the primary circuit, the simplification of the circuit can be measured by making the drive power supply of the power control means common to the drive power supply of the voltage control means of the low voltage power supply.

When both the fixing device and the low-voltage power supply circuit are to be universally compatible, a primary AC input voltage detecting means is provided, and the control condition of the switching time of the low-voltage power supply circuit and the fixing device power control means is determined according to the detection result. Can be changed by changing

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 2 is a cross-sectional view for explaining the configuration of a main part of an image recording apparatus according to a first embodiment of the present invention, and shows, for example, the case of a laser printer.

The same parts as those in the first conventional example are denoted by the same reference numerals, and description thereof may be omitted.

Hereinafter, the configuration and operation will be described.

A commercial power supply (AC) is input from an inlet 101, and the AC input is distributed to two places, a fixing unit 120 and a low-voltage power supply, via a filter 102.

First, the control of the fixing device will be described.
The AC input is connected to the rectifier diode 10 after the filter 102.
6. Rectified by the capacitor 107. However, since it is not necessary to completely smooth the AC voltage in the fuser control,
The capacitor 107 may have a capacitance of about several μF. The ceramic heater 121 is turned on by the switching element 108.
・ OFF control is performed. Although an IGBT is used as the switching element 108 in this embodiment,
It is also possible to use ET and transistors. The switching element 108 is driven by the fixing control unit 103.

FIG. 3 shows a switching element 108 (IGB).
The collector voltage and current waveform of T) are shown. FIG. 3A shows the envelope waveform of the rectified waveform because the waveform rectified by the diode 106 is turned ON / OFF by the switching element 108 at a switching cycle of a frequency higher than the frequency of the AC input. Looks like (B) and (c) are switching waveforms. Note that the time scales of (a) and (b) and (c) do not match.

The fixing device control section 103 starts and stops according to a signal from the engine controller 130 according to an ON signal. Further, the fixing device control unit 103 includes a thermistor 1
22 based on the temperature detection information from the ceramic heater 1.
When the temperature reaches the desired temperature, the engine controller 13 sends an RDY signal notifying that printing is possible.
Output to 0.

FIG. 4 shows the internal configuration of the fixing unit control unit 103. In FIG. 4, a signal e is a voltage from the thermistor 122, is compared with a reference voltage 135, and is amplified by an error amplifier 131. Output a of error amplifier 131
Is the output b of the triangular wave oscillator 134 and the comparator 132
And output via the buffer amplifier 133.
An output c of the buffer amplifier 133 is an output of the fixing device control unit 103 and becomes a drive signal of the switching element 108. FIGS. 5A and 5B show the voltage waveforms of a, b and c, respectively.

As described above, since the thermistor voltage e is feedback-controlled so as to be equal to the reference voltage 135, the temperature of the ceramic heater 121 can be controlled. Further, by changing the reference voltage 135, the temperature of the ceramic heater 121 can be changed.

Next, the low voltage power supply circuit will be described. A
After passing through the filter 102, the C input
Rectified and smoothed by the capacitor 110. The switching power supply transformer 113 and the switching element 11
2 and the power supply (Vc
c, Gnd). When the control method of the power supply control unit 105 is the separately-excited control, a drive power supply for the primary-side control circuit is required. In this embodiment, an auxiliary winding c is provided in the switching transformer 113, the output of the auxiliary winding c is rectified by the rectifier circuit 104, and the power supply controller 105 and the fixing device controller 1
03.

In this embodiment, the switching transformer 11
Although a third auxiliary winding c is used, a rectified and smoothed DC / DC converter is constituted by the diode 109 and the capacitor 110, and the power supply control unit 105 and the fixing device control unit 103
It is also possible to supply power to the power supply.

(Second Embodiment) FIGS. 6 and 8 show a second embodiment.
1 shows a configuration diagram of an embodiment of the present invention.

The basic configuration is the first configuration shown in FIGS.
This is the same as the embodiment.

In the present embodiment, the configuration that enables the fixing device to be universal has been described.

A voltage detecting section 140 shown in FIG.
It is determined whether it is a V system. The voltage detection unit 140 outputs a determination signal to the fixing control unit 103 and the power supply control unit 141, and each control unit performs control based on the determination signal.

Here, the voltage detector 140 can be a detection by an electric circuit or a changeover switch set by a user who uses the apparatus.

The power control section 141 responds to a universal power supply such as a double rectification system or a boost converter system based on the determination signal.

The fixing control unit 103 switches the ON / OFF time of the pulse oscillator 136 according to the determination signal f as shown in FIGS. The pulse oscillator 136 outputs a triangular wave b1 and a rectangular wave b2 having a waveform that is turned on only during the voltage rising period of the triangular wave b1. Output a of error amplifier 131
The signal of the triangular wave b1 and the rectangular wave b2 is compared with a comparator 137.
The output c of the waveform that is turned on only during the voltage rise period of b1 that is higher than b1 is determined. FIG. 7 shows output waveforms of a, b1, and c.

As a result, the AC input becomes 100 V
Regardless of V, the optimal control of the ceramic heater 121 becomes possible. 7A and 7B correspond to a 100 V input, and FIGS. 7A and 7B correspond to a 200 V input. For a 200 V input, the power of the ceramic heater 121 is increased. Since (V ＾ 2 / R) becomes large, the ON time is shortened and the OFF time is lengthened to cope with the problem. According to the present embodiment, since both the low-voltage power supply and the fixing device can universally support regardless of the power supply frequency, it is possible to provide an image forming apparatus that can support worldwide.

[0048]

As described above, according to the present invention,
The following effects can be obtained.

(1) Flicker noise can be reduced.

(2) It is easy to cope with the universalization of the fixing device.

(3) Universal support of the image forming apparatus can be realized.

(4) The firmware of the image forming apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus.

FIG. 2 is a configuration diagram of a first embodiment.

FIG. 3 is a diagram showing operation waveforms of the first embodiment.

FIG. 4 is a configuration diagram of a fixing device control unit according to the first embodiment.

FIG. 5 is a diagram illustrating operation waveforms of a fixing device control unit according to the first embodiment.

FIG. 6 is a configuration diagram of a fixing device control unit according to a second embodiment.

FIG. 7 is a diagram illustrating operation waveforms of a fixing device control unit according to the second embodiment.

FIG. 8 is a configuration diagram of a second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 image forming apparatus 103 fixing unit control unit 105 power supply control unit 108 switching element (IGBT) 120 fixing unit 121 ceramic heater 130 engine controller 131 error amplifier 132 comparator 134 triangular wave oscillator

Claims (10)

[Claims] 1. A rectifying unit for rectifying a primary AC power supply and supplying the rectified output to a heating fixing unit for fixing an image on a recording medium, and a rectified output of the rectifying unit supplied to the heating fixing unit. A switching unit for switching at a frequency higher than the next alternating current; a temperature detecting unit for detecting a temperature of the heating and fixing unit; and a consumption of the heating and fixing unit by controlling the switching unit based on a detection result of the temperature detecting unit. An image forming apparatus comprising: power control means for controlling power. 2. The power control unit according to claim 1, wherein the power control unit detects an error between a detection result from the temperature detection unit and a reference value, and outputs a triangular wave having a frequency higher than the primary AC. Image forming means for generating a triangular wave, and comparing means for comparing an error detection output from the error detecting means with a triangular wave from the triangular wave generating means and supplying it as a control output to the switching means. apparatus. 3. The image forming apparatus according to claim 2, wherein the reference value is variable. 4. The image forming apparatus according to claim 1, wherein the heating and fixing unit has a ceramic heater. 5. A drive for supplying power commonly to a voltage control unit of a low-voltage power supply circuit that generates a secondary circuit voltage from the primary alternating current, and the power control unit. An image forming apparatus comprising a power supply. 6. The low-voltage power supply circuit according to claim 5, wherein the low-voltage power supply circuit is a switching regulator.
An image forming apparatus, wherein an auxiliary winding provided in a switching transformer of the switching regulator is connected to an input of the driving power supply. 7. The low-voltage power supply circuit according to claim 5, wherein the low-voltage power supply circuit has a DC-DC converter, and supplies power to the voltage control means and the voltage control means in common from the DC-DC converter. Image forming device. 8. A voltage detecting means for detecting a voltage of said primary AC power supply, and a control condition of said power control means is changed based on a detection result of said voltage detecting means. An image forming apparatus comprising: a change unit. 9. The image forming apparatus according to claim 8, wherein the control condition is at least one of an ON time and an OFF time of the switching unit. 10. A voltage detecting means for detecting a voltage of said primary AC power supply, and a control condition of said voltage controlling means is changed based on a detection result of said voltage detecting means. An image forming apparatus comprising: a change unit.