JP2002229375A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a fixing device from taking a long warm-up time, and also prevent power from being oversupplied to a fixing heater in the fixing device of a picture forming device for forming a toner picture on recording paper. SOLUTION: This fixing device comprises a rectifier 302 for generating DC voltage by rectifying AC voltage from an AC power source 301, a voltage detection device 305 for detecting a decrease in an output voltage of the rectifier 302 with respect to a reference voltage, and a supply power generation device 306 for phase-controlling the AC voltage from the AC power source 301 according to detection information D1 from the rectifier 302 and supplying it to the fixing heater HL. When a voltage drop of the AC power source 301 causes a shortage of power supply to the fixing heater HL, the power supply generation device 306 controls the power supply to compensate for about 50% of the power supply shortage to the fixing heater HL based on the information D1 detected by the voltage detection device 305.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine for forming a toner image on a recording sheet.
The present invention relates to a fixing device for fixing a toner image on recording paper.

[0002]

2. Description of the Related Art Generally, an image forming apparatus such as a copying machine has
A fixing device is provided for fixing the toner image transferred to the recording paper to the recording paper. The fixing device includes an electric heater (hereinafter, referred to as a fixing heater) for melting the toner on the recording paper and attaching the toner to the recording paper.

Heretofore, as this type of fixing device, there has been known a fixing device which supplies AC power from an AC power supply to a fixing heater via a switch such as a triac. There is also known an apparatus in which AC power from an AC power supply is phase-controlled and supplied to a fixing heater.

[0004]

However, in the former fixing device, when the AC voltage from the AC power supply drops, the power supplied to the fixing heater also decreases, so that the warm-up time of the fixing device becomes longer. Problem.

Further, in the latter fixing device, when the AC voltage from the AC power supply drops, the adjustment of the correction amount of the supplied power corresponding to the drop is performed by adjusting the impedance of the wiring,
There is a problem that it is difficult due to a change in the temperature coefficient of the circuit element and the like, and if the correction amount is large, the power supplied to the fixing heater is over (excess).
When the power supplied to the fixing heater is excessive, not only does the power consumption of the entire apparatus increase, but also there is a danger of smoke or ignition.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is possible to prevent the warm-up time of the fixing device from being lengthened and to increase the power supplied to the fixing heater. It is an object of the present invention to provide a fixing device capable of preventing the occurrence of the problem.

[0007]

In order to achieve the above object, the present invention has the following arrangement. The present invention relates to a fixing device provided with an electric heater for fusing toner transferred to a recording sheet, a rectifying unit for rectifying an AC voltage from an AC power supply to generate a DC voltage, and the rectifying unit for a reference voltage. Voltage detecting means for detecting a decrease value of the output voltage, and supply power generating means for supplying an AC voltage from the AC power supply to the electric heater by controlling a phase in accordance with detection information from the voltage detecting means. Wherein the supply power generation means comprises:
When a shortage of power to be supplied to the electric heater occurs due to a decrease in the voltage of the AC power supply, the power supplied is increased so as to compensate for approximately 50% of the shortage of power supplied to the electric heater based on information detected by the voltage detecting means. In the fixing device.

Further, the supply power generation means obtains a phase control time corresponding to the supply power shortage based on the value detected by the voltage detection means, and calculates 1/1/3 of the phase control time.
Phase control is performed using the correction amount for two hours. The phase control time is corrected by correcting the pulse width of the phase control signal.

[0009]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic front sectional view showing a configuration of a digital color copying machine 1 which is an image forming apparatus according to an embodiment of the present invention. A document table 111 and an operation panel are provided on an upper surface of the copying machine main body 1, and an image reading section 110 and an image forming section 21 are provided inside the copying machine main body 1.
0 is provided.

The upper surface of the document table 111 is supported so as to be openable and closable with respect to the document table 111, and has a predetermined positional relationship with respect to the surface of the document table 111, and a double-sided automatic document feeder (R)
ADF: Reversing Automatic Document Feeder) 11
2 is installed.

Further, the automatic two-sided automatic document feeder 112 includes:
First, the document is conveyed such that one surface of the document faces the image reading unit 110 at a predetermined position on the document table 111,
After the image reading for this one side is completed,
The original is inverted so that the other surface faces the image reading unit 110 at a predetermined position on the original
To be conveyed toward.

The automatic two-sided automatic document feeder 112
After reading the image on both sides of one document, the document is discharged, and the double-sided conveyance operation for the next document is executed.

The operation of transporting the original and reversing the original is controlled in relation to the operation of the entire copying machine.

The image reading section 110 is arranged below the document table 111 for reading an image of the document conveyed onto the document table 111 by the automatic duplex document feeder 112.

An image reading section 110 includes an original scanning body 113, 1 which reciprocates in parallel along the lower surface of the original table 111.
14, an optical lens 115, and a photoelectric conversion element CC
And a D line sensor 116.

The original scanning bodies 113 and 114 are composed of a first scanning unit 113 and a second scanning unit 114. The first scanning unit 113 has an exposure lamp for exposing the surface of the original image, and a first mirror for directing a reflected light image from the original in a predetermined direction. Are reciprocated in parallel at a predetermined scanning speed while maintaining the above distance.

The second scanning unit 114 is a second scanning unit for further providing a reflected light image from the document deflected by the first mirror of the first scanning unit 113 in a predetermined direction.
And a third mirror, and the first scanning unit 113
And reciprocate in parallel while maintaining a constant speed relationship.

The optical lens 115 reduces the reflected light image from the document deflected by the third mirror of the second scanning unit, and forms the reduced light image at a predetermined position on the CCD line sensor 116. It is. The CCD line sensor 116 photoelectrically converts the formed light image in order and outputs it as an electric signal.

The CCD line sensor 116 reads a black-and-white image or a color image, and outputs R (red), G (green), B
This is a three-line color CCD that can output line data that is color-separated into each color component of (blue).

The document image information converted into an electric signal by the CCD line sensor 116 is further transferred to an image processing unit (not shown) and subjected to predetermined image data processing.

Next, the configuration of the image forming unit 210 and the configuration of each unit related to the image forming unit 210 will be described.
Below the image forming unit 210, there is provided a paper feed mechanism 211 that separates sheets (recording media) P stacked and accommodated in a sheet tray one by one and supplies the separated sheets to the image forming unit 210.

Then, the paper P supplied one by one is
The timing is controlled by a pair of registration rollers 212 disposed in front of the image forming unit 210 and the image forming unit 2 is controlled.
It is transported to 10.

Further, the sheet P on which an image is formed on one side is
The sheet is re-supplied and conveyed to the image forming unit 210 in synchronization with the image formation of the image forming unit 210.

Below the image forming section 210, a transfer belt mechanism 213 is disposed. The transfer / transport belt mechanism 213 is provided between the drive roller 214 and the driven roller 215 to extend substantially in parallel with the transfer / transport belt 21.
6, the paper P is electrostatically attracted and transported. In addition, a pattern image detection unit 232 is provided near the lower side of the transfer conveyance belt 216. Further, on the downstream side of the transfer / conveyance belt mechanism 213 in the paper conveyance path, the toner image transferred and formed on the paper
A fixing device 217 for performing fixing thereon is provided.

The sheet P having passed through the nip between the pair of fixing ports of the fixing device 217 passes through a conveyance direction switching gate 218, and is discharged by a discharge roller 219 to the sheet P attached to the outer wall of the copying machine body 1. It is discharged onto the tray 220.

The switching gate 218 is connected to the sheet P after fixing.
Is selectively switched between a path for discharging the sheet P to the copying machine main body 1 and a path for re-supplying the sheet P toward the image forming unit 210.

The paper P whose transport direction has been switched again toward the image forming unit 210 by the switching gate 218
Is turned over via the switchback transport path 221 and then supplied to the image forming unit 210 again.

In the digital color copying machine having the above configuration, cut sheet-shaped paper is used as the paper P. The sheet P is sent out from the sheet cassette and fed to the sheet feeding mechanism 2.
11, the leading end of the sheet P is detected by a sensor (not shown), and based on a detection signal output from the sensor, the pair of registration rollers 212 Once stopped.

The paper P is stored in each image station Pa.
Taking ~Pd and timing sent onto the transfer conveyor belt 216 rotating in the arrow Z direction in FIG. At this time, since the transfer / transport belt 216 is given a predetermined charge by the attraction charger 228 as described above, the sheet P is stably transported and supplied while passing through the image stations Pa to Pd. .

In each of the image stations Pa to Pd, a toner image of each color is formed, and is superposed on the support surface of the paper P conveyed by being electrostatically attracted and conveyed by the transfer conveyance belt 216.

When the transfer of the image by the fourth image station Pd is completed, the sheet P is sequentially separated from the transfer / conveying belt 216 by the negative discharger from the leading end thereof, and is guided to the fixing device 217.

Finally, the sheet P on which the toner image is fixed
Is discharged onto a paper discharge tray 220 from a paper exit (not shown).

In the above description, the laser beam is scanned and exposed by the laser beam scanner units 227a to 227d to write light on the photosensitive member. However, a writing optical system (LED head) including a light emitting diode array and an imaging lens array may be used instead of the laser beam scanner unit.

The LED head is smaller in size than the laser beam scanner unit, has no moving parts, and is silent. Therefore, it can be suitably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

Next, the fixing device 2 according to the characteristic portion of the present invention.
The seventeenth power control device 300 will be described with reference to FIGS. FIG. 2 is a circuit diagram showing the power control device 300. As shown in FIG. 2, the power control device 300 includes an AC power supply 301, a rectifier (rectifier) 302, a voltage detector (voltage detector) 305, a supply power generator (supply power generator) 306, Rectifier (rectifier)
302 and a voltage detection device (voltage detection means) 305.

The rectifier 302 is connected between the AC power supply 301 and the voltage detector 305, rectifies the AC voltage from the AC power supply 301, generates a DC voltage, and supplies the DC voltage to the voltage detector 305. For example, the rectifier 302 includes a diode bridge circuit 303 that rectifies an AC voltage from the AC power supply 301 to generate a DC voltage, and a smoothing circuit that smoothes the DC voltage from the diode bridge circuit 303 and applies the DC voltage to the voltage detector 305. 304. The smoothing circuit 304 is composed of capacitors connected in parallel between the output terminals of the diode bridge circuit 303, for example, two capacitors 304a and 304b, and is composed of an RC circuit (resistance is omitted). The rectifier 302 is
It may be constituted only by the diode bridge circuit 303.
The smoothing circuit 304 may be configured by an LC circuit using a coil and a capacitor.

In the rectifier 302 having the above configuration, the AC waveform of the commercial outlet (for example, 100 V AC * √ in Japan)
2 = 141 V) is converted to a DC voltage HLV through a diode bridge circuit 303 and a smoothing circuit 304.

The voltage detecting device 305 is constituted by a machine microcomputer or the like, and constantly monitors the value of the DC voltage HLV.

The supply power generator 306 is composed of a microcomputer capable of controlling the phase of the AC power supply voltage, is connected to an AC power supply 301 such as a commercial power supply, and the fixing heater HL of the fixing device 217. While controlling the phase of the AC voltage based on the information D1, the power supply to the large capacity load such as the fixing heater HL is generated.
Note that the detection information D1 may be any information that can transmit the voltage drop amount, such as a numerical value or a symbol.

Next, the operation of the power control device 300 will be described with reference to FIG. FIGS. 3A and 3B show the power supply waveforms when there is no voltage drop (a to c) and when there is a voltage drop (d to f). FIG. 3A shows an AC power supply waveform S1, and FIG. The power supply waveform S2 for the fixing heater, (c) is the phase control input signal waveform P1, (d) is the AC power supply waveform S1a at the time of drop, (e) is the power supply waveform S2a for the heater whose phase is controlled, (f) is the phase 5 shows an input signal waveform P2 to be controlled.

When power is supplied to the fixing heater HL, the AC waveform S1a (FIG. 3D) distorted due to the drop of the power supply waveform (sin waveform) S1 at the outlet, that is, the converted DC voltage HLV waveform Since the phase control time changes (decreases) due to the drop, the fixing heater HL is
The power supplied to the system becomes insufficient. In a specific example, the DC voltage HLV at the time of the AC voltage AC141 (V) is temporarily
It will be described below as 2.5 (V).

First, when the copier 1 is connected to an outlet serving as the AC power supply 301 and the power is turned on, the copier 1 enters a warm-up operation, so that power is naturally supplied to the fixing heater HL.

At this time, when power is being supplied to a large-capacity load such as the fixing heater HL, the voltage of the outlet will drop in most cases. Here, it is assumed that the drop voltage (voltage drop amount) is △ 5 V (detection information D1). That is, when the copying machine 1 is turned on, the voltage of the outlet becomes 141V-5V = 136V (FIG. 3D).

If there is no voltage drop (FIG. 3)
(A)) It is assumed that the phase-on time (pulse width) at the time of supplying power to the fixing heater HL from the supply power generation device 306 by the phase control with respect to the AC voltage 141 (V) is designed to be A (sec). I do. The ON time A is arbitrarily determined from a value for achieving the warm-up time.

FIG. 3B shows an actual AC voltage waveform applied to the fixing heater HL when the ON time A is input.

However, in practice, when power is supplied to the fixing heater HL, the voltage at the outlet drops by 5 V, so that the specified time until the warm-up of the fixing heater HL is completed exceeds the ON time A. Would. This means that the power required for the fixing heater HL is insufficient for the voltage drop # 5 (V) of the outlet. As a method of compensating for the insufficient power, the amount of change ΔHL of the DC voltage HLV obtained by DC-converting the voltage drop of △ 5 (V) is used.
When the voltage detection device 305 detects V and corrects the power with respect to the DC voltage change amount △ HLV corresponding to △ 5 (V), the correction amount may cause various problems. Come.

For example, due to a change in wiring impedance inside the copying machine 1, the influence of external noise, or a change in temperature coefficient of each component element of the control circuit board, the voltage drop # 5
It is impossible to detect 100% of the correction amount of (V) as far as there is no real problem, and the voltage detection device 305 detects a power shortage due to the power supply voltage drop # 5 (V) from the change amount of the DC voltage HLV. If the shortage is corrected, the correction may be overcorrected. In such a case, the power consumption of the entire copying machine 1 may be excessive, and the risk of smoke or ignition may be considered.

In this embodiment, the correction amount of the power supply shortage due to the power supply voltage drop occurring when the power is supplied to the large-capacity load such as the fixing heater HL is corrected to approximately half the voltage drop equivalent power.

First, the supply power generator 306 calculates a correction power amount from the value of the DC voltage HLV (detection information D1) that changes due to the drop of the power supply voltage (step 1).

Next, the phase control time (ON time) α of the correction amount is calculated from the correction power amount obtained in the calculation process (FIG. 3 (f)) (step 2).

In the present embodiment, the supply power generator 306
Since the correction power amount for actually performing the correction on the fixing heater HL is approximately half that, the phase control time (α / 2) corresponding to the half power amount is obtained (FIG. 3 (f)) (step 3). .

As described above, a power supply waveform S2a for the fixing heater including a correction voltage corresponding to the phase control time (α / 2) can be obtained from the supply power generation device 306 to the fixing heater HL. Therefore, it is possible to correct almost half of the voltage drop equivalent power from the supply power generation device 306 to the fixing heater HL. 3B. In FIG. 3E, reference character b indicates a fixing heater power supply waveform region corresponding to the phase control time α, and reference character c indicates a fixing heater power supply waveform region corresponding to the phase control time (α / 2). ing.

As described above, the virtual pulse width of the phase control signal corresponding to the shortage of the power supplied to the fixing heater 217 is obtained, and about 1/2 hour of the virtual pulse width is used as the actual correction amount. By correcting the pulse width of the phase control signal generated in step 306, the supply power can be controlled so as to compensate for the shortage of about 50% of the supply power to the fixing heater 217.

As described above, it is possible to prevent a shortage of power due to a voltage drop and to prevent the warm-up time from being exceeded, and to reduce the voltage drop by 100%, which is a concern over the total power consumption of the machine. The danger that leads to smoking and ignition can be prevented.

[0055]

As described above, according to the fixing device of the present invention, when the power supply to the fixing heater is insufficient due to the decrease in the voltage of the AC power supply, the power supply to the fixing heater is reduced by about 50%.
The power supply is controlled so as to compensate for the shortcomings, thus preventing the warm-up time from becoming longer and preventing the power supply to the fixing heater from becoming excessive, thus reducing power consumption. can do.

[Brief description of the drawings]

FIG. 1 is a front longitudinal sectional view of a copying machine having a fixing device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a power control device of the fixing device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a comparison of power supply waveforms and the like when there is no voltage drop (a to c) and when there is a voltage drop (d to f), wherein (a) shows AC power supply waveforms S1 and (b). ) Is the phase-controlled power supply waveform S2 for the fixing heater, (c) is the phase control input signal waveform P1, (d) is the AC power supply waveform S1a at the time of drop, (e) is the power supply waveform S2a for the phase-controlled heater, (F) shows the input signal waveform P2 to be phase-controlled.

[Explanation of symbols]

 1 Copying Machine (Image Forming Means) 217 Fixing Device 301 AC Power Supply 302 Rectifier (Rectifier) 303 Diode Bridge Circuit 304 Smoothing Circuit 305 Voltage Detector (Voltage Detector) 306 Supply Power Generator (Supply Power Generator) D1 Detection Information HL Fixing heater (electric heater)

Continued on the front page (72) Inventor Tamaki Mashiba 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside (Sharp) (72) Inventor Akihiko Taniguchi 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka (72) Inventor Shigeru Watayo 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Junichi Kajihara 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F-term (Reference) 2H027 DA01 DE05 DE07 EA12 EA15 ZA01 2H033 AA30 AA32 AA42 BB17 CA23 CA28 CA44 CA46 3K058 AA02 AA03 AA04 AA53 BA18 CA03 CA16 CA23 CB06 CC06 CD01 DA11 GA06

Claims (2)

[Claims] 1. A fixing device comprising an electric heater for melting toner transferred to a recording sheet, a rectifier for rectifying an AC voltage from an AC power supply to generate a DC voltage, and the rectifier for a reference voltage. Voltage detection means for detecting a decrease value of the output voltage of the means, and supply power generation means for supplying an AC voltage from the AC power supply to the electric heater by controlling a phase in accordance with detection information from the voltage detection means. The power supply generation means, when a shortage of power supply to the electric heater occurs due to a voltage drop of the AC power supply, based on information detected by the voltage detection means, the power supply shortage to the electric heater Wherein the supply power is controlled so as to compensate for approximately 50% of the fixing device. 2. The power supply generation means calculates a phase control time corresponding to the power supply shortage based on a value detected by the voltage detection means, and calculates a correction amount of 時間 of the phase control time. 2. The fixing device according to claim 1, wherein phase control is performed.