JP2003295538A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize the output of an unfixed image and to prevent inside of an apparatus from getting dirty with unfixed toner, and a succeeding carried paper from getting dirty when power voltage drops in the middle of printing by detecting dropping of inputted commercial power source. <P>SOLUTION: This image forming apparatus comprises a power source voltage monitoring means, a density adjusting means, and a toner image generation means. When discriminating that the inputted commercial power source drops to be lower than a prescribed value, control for the emission stoppage of a semiconductor laser the image density of which is lowered and cutting off of energization to a conveyance driving motor is performed to minimize the output of fixed defective image and to prevent remaining of the unfixed toner. When discriminating that the inputted primary power source drops to be lower than a prescribed value in addition, a succeeding recording paper is put through as it is a white paper so as to fix the unfixed toner to this white paper. Thus, the output of an unfixed image is minimized, thereby inside of the apparatus is prevented from getting dirty with the unfixed toner and the succeeding carried paper is prevented from getting dirty. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a thermal fixing device for fixing a toner image on a recording sheet, and improves the toner fixing property.
The present invention also relates to an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, which prevents the inside of the device from being soiled by unfixed toner.

[0002]

2. Description of the Related Art In recent years, in a copying machine or printer using an electrophotographic process, a heat fixing device using a heater as a heating means has been used to fix a toner image formed on a recording sheet. To heat-fix the toner image,
Using a triac, a solid-state relay, or a thermistor as a means for detecting the temperature, a fixing heater is arbitrarily set in a form of ON / OFF control of a commercial power supply voltage waveform as shown in FIGS. 6 and 7 as image diagrams. The temperature control is performed so that the temperature T0 (hereinafter, referred to as the target temperature T0) becomes high. Here, when the commercial power supply voltage, which is the power source of the fixing heater, decreases during printing, the power supplied to the recording paper with respect to the transport speed decreases. If this state continues, that is, even if power is supplied continuously to turn on the fixing heater for an arbitrarily set time, the arbitrarily set temperature T1 (hereinafter, failure detection start Temperature T1), (T1 <T0) or less If a certain time t1 (hereinafter, failure detection time t1) continues for a certain period of time, it is determined that the temperature does not rise, and the control unit is in a low temperature state or energized. However, since the temperature does not rise, an abnormal state is set and the user is notified of the failure state.

[0003]

However, in the above-mentioned conventional example, when the commercial power supply voltage drops during continuous printing at the target temperature, the entire system necessary for fixing such as the fixing heater and the pressure roller is It often takes time to fall to the temperature at which a failure is recognized because the temperature is warm. During this period, of course, the fixing heater lacks the electric power supplied to the paper,
The toner image cannot be completely fixed, and an image having inferior fixability is output to some extent. As the transporting speed of the apparatus is higher, the number of images with improper fixing output is naturally increased. Further, at this time, unfixed toner that is not fixed remains in the thermal fixing device due to insufficient power supplied. In this phenomenon also, the residual amount of unfixed toner increases as the conveying speed of the apparatus increases. The unfixed toner sometimes stains the inside of the machine. Further, when the commercial power supply voltage returns to the rated voltage of the device before the control unit detects that the temperature is low or abnormal, the unfixed toner remaining inside the thermal fixing device is rapidly heated due to the increase in power. Therefore, there is a drawback that the image is fixed on the recording paper that is conveyed subsequently, and an image different from the user's intention is conveyed and discharged.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by adopting the structure described below. A first object of the present invention is to solve the problems with toner at a predetermined paper conveying speed. The toner image generating means for generating an image on a recording sheet, and the toner image by contacting the recording sheet having the toner image generated on the surface by the toner image generating means with a predetermined pressure and heating at the contact portion. A fixing means for fixing the recording paper at a paper conveyance speed, a temperature control means for transmitting the electric power received from the commercial power source to the fixing means to keep the temperature of the contact portion at a desired temperature, and a voltage of the commercial power source are monitored. In an image forming apparatus provided with a power supply voltage monitoring unit and a conveyance drive unit mechanically connected to the toner image generating unit and the fixing unit, the power supply voltage monitoring unit is used for commercialization. When it is determined that the source voltage has dropped below a predetermined value, the image density is lowered by the density adjusting means to avoid fixing failure when the commercial power supply voltage drops, and unfixed toner remains in the fixing means. It is to avoid stains on the recording paper conveyed in the machine and next.

A second object of the present invention is to stop the emission of laser light controlled by the laser modulation means when the power supply voltage monitoring means determines that the commercial power supply voltage has dropped below a predetermined value. That is, the image formation on the recording paper by the electrostatic latent image process is stopped, and the unfixed toner remains in the fixing means to avoid the contamination of the recording paper in the apparatus and next conveyed. The third aspect of the present invention
The purpose of is, when it is determined that the commercial power supply voltage has dropped below a predetermined value, before starting the image generation process that should be performed on the subsequent recording paper, the blank recording paper is conveyed as it is without image formation, By fixing the unfixed toner remaining in the fixing means, it is possible to prevent a desired print image from being stained.

A fourth object of the present invention is, when the commercial power supply voltage drops when the commercial power supply voltage is judged to be lower than a predetermined value by the power supply voltage monitoring means, by cutting off the power supply to the carrier driving means. That is, the conveyance of the unfixed image is stopped, and the unfixed toner remains in the fixing means to avoid the stain on the recording paper conveyed in the apparatus and next.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a sectional view showing the outline of the overall construction of an image forming apparatus showing the present invention,
FIG. 2 is a commercial power supply waveform diagram showing that the fixing heater is continuously turned on with respect to time.

FIG. 3 shows a power supply voltage monitoring method implemented in the present invention. In FIG. 1, reference numeral 1 is an image forming apparatus main body, 2
Is a paper cassette. 3a is a paper cassette 2
To a recording paper P (hereinafter, abbreviated as paper P) from the paper feed roller, 3b is a conveyance roller for conveying the paper P fed by the paper feed roller 3a to a conveyance path, and 4 is an image writing timing. Paper feed sensor to do. A laser scanner unit 5 is a semiconductor laser 5a based on image data.
The laser beam emitted from the scanning unit is scanned, and the folding mirror 6 scans the photosensitive drum 7a in the process cartridge 7 to form an electrostatic latent image on a portion charged by a charger 7b which is a charging unit. . The electrostatic latent image on the photosensitive drum 7a is toner-developed by a developing device 7c which is a developing means, and is transferred onto a sheet P by a transfer portion 7d which is a transfer means. The toner image on the paper P is fixed by applying heat and pressure in the heat fixing device 8 which is a fixing unit. The heat fixing device 8 is composed of a fixing heater 8a which is a heating resistor, a thermistor 8b which detects the temperature state of the heating resistor, a pressure roller 8c and a heat resistant film 8d. A paper discharge roller 9 discharges the paper P passing through the thermal fixing device 8 to the paper discharge tray 10.

Reference numeral 11 denotes an engine controller section as a control means, which is electrically connected to each device and controls integrally. Further, the control means 11 includes density adjusting means for adjusting the density, temperature controlling means for controlling the fixing heater 8a to a desired temperature, power source voltage monitoring means for monitoring the voltage of the commercial power source input, and the like. There is. 12
Is a conveyance motor which is mechanically connected to the process cartridge 7 and the thermal fixing device 8 and plays a central role for conveying the paper P at a predetermined paper conveyance speed.

As the power supply voltage monitoring means in this embodiment, as shown in FIGS. 2 and 3, the judgment is made by utilizing the time during which the fixing heater 8a is continuously turned on. Failure detection start temperature
When it is determined that the fixing heater 8a is continuously turned on for a predetermined time tA before detecting T1, it is determined that the commercial power supply voltage has dropped, and the charging bias applied to the charger 7b, Also, control is performed to reduce the density of the toner image by changing the developing bias applied to the developing device 7c.
For example, when the sheet P is being conveyed and the value of the commercial power supply voltage is within the rated voltage range, the charging bias Vp is Vp = -670V, and the developing bias Vd is Vd = -500V when the high voltage output control is performed. When the ON time of the fixing heater 8a is continued for tA and the decrease of the power supply voltage is recognized, the output of the charging bias Vp is controlled to Vp = -600V and the output of the developing bias Vd is controlled to Vd = -400V.

By carrying out the above-mentioned control, it is possible to improve the fixing failure image which is output due to the decrease in the density of the toner image, and at the same time, the unfixed toner remaining in the fixing device can be reduced. It will be possible. As yet another method, when it is determined that the fixing heater 8a is continuously turned on for a predetermined time tA before the failure detection start temperature T1 is detected, it is determined that the commercial power supply voltage has dropped, The emission of the semiconductor laser 5a is stopped and a blank sheet is output.

By performing the above-described control, the output of a defective fixing image is suppressed to a minimum, and the unfixed toner remaining in the fixing device is also output as a blank sheet to be fixed on the blank sheet. It is possible to reduce the amount of toner. As another method, the failure detection start temperature T
When it is determined that the fixing heater 8a is continuously turned on for a predetermined time tA before detecting 1, the commercial power supply voltage is determined to be low, and the driving of the carry motor 12 is stopped.

By performing the above-mentioned control, the output of the defective fixing image can be minimized. Here, in this embodiment, when the commercial power supply voltage is within the rated voltage range, it is natural that the fixing heater is considered even in consideration of the environment in which the apparatus is installed, for example, the low temperature environment, the type of the paper P to be conveyed, and the like. The condition is that the continuous ON time of is less than or equal to tA. In this embodiment, the fixing heater is a planar heater having good thermal conductivity, but the same applies to the case where a lamp heater is used.

(Second Embodiment) Since the apparatus configuration is the same as that of the first embodiment shown in FIG. 1, the same reference numerals will be used to describe the same devices. FIG. 4 shows a power supply voltage monitoring method performed in the second embodiment. The difference from the first embodiment is the method of monitoring the power supply voltage. That is, the voltage drop is determined by utilizing the fact that the temperature difference ΔT or more arbitrarily set with respect to the target temperature T0 is continued for the arbitrarily set time tB. As shown in FIG. 4, a predetermined time t after the detection of the temperature difference of ΔT or more with respect to the target temperature T0 before the failure detection start temperature T1 is detected.
When it is determined that the temperature difference ΔT is continuously exceeded for B, it is determined that the commercial power supply voltage is decreased, and the charging bias applied to the charger 7b and the developing bias applied to the developing device 7c are changed to change the toner image. The control is performed to reduce the concentration of. For example, when the charging bias Vp is Vp = -670V and the developing bias Vd is Vd = -500V when the power supply voltage is not decreased, the temperature difference ΔT from the target temperature or more is maintained for tB. When a decrease in the power supply voltage is recognized, the output of the charging bias Vp is controlled to Vp = -600V and the output of the developing bias Vd is controlled to Vd = -400V.

By carrying out the above-mentioned control, it is possible to improve the fixing failure image that is output due to the toner image having a low density, and at the same time, reduce the amount of unfixed toner remaining in the fixing device. It will be possible.

As another method, the failure detection start temperature
When it is determined that a temperature difference of ΔT or more occurs with respect to the target temperature T0 before T1 is detected, and it is determined that the temperature difference ΔT or more continues for an arbitrarily set time tB, commercial When it is determined that the power supply voltage has dropped, the semiconductor laser 5a stops emitting light and outputs a blank sheet.

By performing the above-described control, the output of a defective fixing image is suppressed to a minimum, and the unfixed toner remaining in the fixing device is also output as a blank sheet and fixed on this blank sheet to fix the unfixed portion. It is possible to reduce the amount of toner.

As another method, the failure detection start temperature
When it is determined that a temperature difference of ΔT or more occurs with respect to the target temperature T0 before T1 is detected, and it is determined that the temperature difference ΔT or more continues for an arbitrarily set time tB, commercial When it is determined that the power supply voltage has dropped, the drive of the carry motor 12 is stopped. By performing the above control,
The output of the poorly fixed image is minimized.

(Third Embodiment) Since the apparatus configuration is the same as that of the first embodiment shown in FIG. 1, the same reference numerals are used to describe the same devices. FIG. 5 shows a power supply voltage monitoring method performed in the third embodiment. 1st Example, and 2nd
The difference from the embodiment is the difference in the power supply voltage monitoring method. That is, the fixing heater 8a detected by the thermistor 8b
The voltage drop is judged according to the temperature. As shown in FIG. 5, the power supply voltage drop detection temperature Tv is set before the failure detection start temperature T1 is detected, and when Tv is detected, it is determined that the commercial power supply voltage is dropped and applied to the charger 7b. The charging bias and the developing bias applied to the developing device 7c are changed to control the density of the toner image to be thin. For example, when the output of the charging bias Vp is Vp = -670V and the developing bias Vd is Vd = -500V when the decrease of the power supply voltage is not recognized, the thermistor 8b is used.
Detects the temperature Tv, and when a decrease in the power supply voltage is recognized, the output of the charging bias Vp is controlled to Vp = -600V and the output of the developing bias Vd is controlled to Vd = -400V.

By performing the above control, it is possible to improve the fixing failure image that is output due to the decrease in the density of the toner image, and at the same time, reduce the unfixed toner remaining in the fixing device. It will be possible. As yet another method, before detecting the failure detection start temperature T1,
The power supply voltage drop detection temperature Tv is set, and when the thermistor 8b detects the temperature Tv, it is determined that the commercial power supply voltage has dropped, the semiconductor laser 5a is stopped from emitting light, and a blank sheet is output.

By performing the above-described control, the output of a fixing failure image is suppressed to a minimum, and the unfixed toner remaining in the fixing device is also output as a blank sheet, and the unfixed image is fixed on the blank sheet. It is possible to reduce the amount of toner.

As another method, the failure detection start temperature
Before detecting T1, the power supply voltage drop detection temperature Tv is set, and when the thermistor 8b detects the temperature Tv, it is determined that the commercial power supply voltage has dropped, and the driving of the carry motor 12 is stopped.

By performing the above-mentioned control, the output of the defective fixing image can be minimized.

[0024]

As described above, according to the first aspect of the present invention.
In the image forming apparatus described in any one of 1 to 5, when it is determined that the commercial power supply voltage is lower than a predetermined value, the image density is reduced to avoid fixing failure when the commercial power supply voltage is reduced, and unfixed toner is fixed. It is possible to prevent the recording paper from remaining in the apparatus and prevent the recording paper conveyed inside the machine and the next conveyed from being soiled. Further, when it is determined that the commercial power supply voltage has dropped below a predetermined value, the laser light emission controlled by the laser modulation means is stopped to stop the image formation on the recording paper by the electrostatic latent image process, and to be determined. It is possible to prevent the deposited toner from remaining in the fixing device, and also to prevent stains on the recording paper conveyed in the apparatus and next.

Furthermore, when it is determined that the commercial power supply voltage has dropped below a predetermined value, the blank recording paper is conveyed as it is without image formation before starting the image generation process to be performed on the subsequent recording paper. By fixing the unfixed toner remaining in the fixing device, it is possible to prevent a desired print image from being stained. Further, when it is determined that the commercial power supply voltage is lower than a predetermined value, the conveyance drive unit is de-energized to stop the conveyance of the defective fixing image when the commercial power supply voltage is reduced, and the unfixed toner is fixed. It is possible to prevent the recording paper from remaining in the apparatus and prevent the recording paper conveyed inside the machine and the next conveyed from being soiled.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an image forming apparatus of the present invention.

FIG. 2 is a commercial power supply voltage waveform diagram showing the time during which the fixing heater is continuously turned on.

FIG. 3 is a voltage monitoring method performed in the first embodiment of the present invention.

FIG. 4 is a voltage monitoring method performed in a second embodiment of the present invention.

FIG. 5 is a voltage monitoring method performed in a third embodiment of the present invention.

FIG. 6 is a fixing heater O during normal temperature control according to the related art.
Image diagram showing N hours

FIG. 7 is a temperature transition diagram of a fixing heater according to the related art.

[Explanation of symbols]

1 is an image forming apparatus main body, 2 is a paper cassette, 3a is a paper feed roller, 3b is a feed roller, 4 is a paper feed sensor, 5 is a laser scanner unit, 5a is a semiconductor laser, 6 is a folding mirror, 7 is a process cartridge, and 7a. Is a photosensitive drum, 7b is a charging device, 7c is a developing device, 7d is a transfer unit, 8 is a thermal fixing device, 8a is a fixing heater, 8b is a thermistor, 8
c is a pressure roller, 8d is a heat resistant film, 9 is a paper discharge roller, 10 is a paper discharge tray, 11 is a control means, and 12 is a conveyance motor.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuichi Seki             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Dai ▲ High ▼ Koichi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Atsushi Wada             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Takashi Sekiguchi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F term (reference) 2H027 DA03 DE07 EA01 EA02 EA15                       EA18 EC06 EJ17 FA27

Claims (5)

[Claims] 1. A toner image generating means for generating a toner image on a recording paper at a predetermined paper conveying speed, and a recording paper on the surface of which the toner image is generated by the toner image generating means is brought into contact with a predetermined pressure, and A fixing unit that fixes the toner image on the recording paper at the paper conveying speed by heating the contact unit, and the electric power received from the commercial power source is transmitted to the fixing unit to maintain the temperature of the contact unit at a desired temperature. Temperature control means, power supply voltage monitoring means for monitoring the voltage of the commercial power supply, conveyance driving means mechanically connected to the toner image generating means and the fixing means, and image density when generating the toner image. In the image forming apparatus including a density adjusting unit for adjusting the density, when the commercial power supply voltage is determined to be lower than a predetermined value by the power supply voltage monitoring unit, the density adjustment is performed. An image forming apparatus characterized in that the image density is changed by means. 2. The image forming apparatus according to claim 1,
The toner image generating unit is charged by a laser modulating unit that modulates a laser beam according to an image signal, a laser scanning unit that irradiates the rotary reflecting plate with the laser beam output by the laser modulating unit, and a charging unit. A rotary photosensitive unit, a developing unit that converts a charged image formed by irradiating the charged rotary photosensitive unit with the scanning laser light into a toner image, and a toner image formed by the developing unit. The density adjusting means is applied to the developing means and the charging means when the power supply voltage monitoring means determines that the commercial power supply voltage has dropped below a predetermined value. An image forming apparatus characterized by changing a bias voltage. 3. A toner image generating means for generating a toner image on a recording paper at a predetermined paper conveying speed, and a recording paper on the surface of which the toner image is generated by the toner image generating means is brought into contact with a predetermined pressure, and A fixing unit that fixes the toner image on the recording paper at the paper conveying speed by heating the contact unit, and the electric power received from the commercial power source is transmitted to the fixing unit to keep the temperature of the contact unit at a desired temperature. A temperature control means, a power supply voltage monitoring means for monitoring the voltage of the commercial power supply, and a conveyance driving means mechanically connected to the toner image generating means and the fixing means, and
The toner image generating unit is charged by a laser modulating unit that modulates a laser beam according to an image signal, a laser scanning unit that irradiates the rotary reflecting plate with the laser beam output by the laser modulating unit, and a charging unit. A rotary photosensitive unit, a developing unit that converts a charged image formed by irradiating the charged rotary photosensitive unit with the scanning laser light into a toner image, and a toner image formed by the developing unit. In an image forming apparatus having a transfer unit for transferring onto a sheet, when the power supply voltage monitoring unit determines that the commercial power supply voltage has dropped below a predetermined value, the emission of the laser beam controlled by the laser modulation unit is stopped. An image forming apparatus comprising: 4. A toner image generating means for generating a toner image on a recording paper at a predetermined paper conveyance speed, and a recording paper on the surface of which the toner image is generated by the toner image generating means is in contact with a predetermined pressure, and A fixing unit that fixes the toner image on the recording paper at the paper conveying speed by heating the contact unit, and the electric power received from the commercial power source is transmitted to the fixing unit to maintain the temperature of the contact unit at a desired temperature. Temperature control means, power supply voltage monitoring means for monitoring the voltage of the commercial power supply, conveyance driving means mechanically connected to the toner image generating means and the fixing means, and image density when generating the toner image. In the image forming apparatus having a density adjusting unit for adjusting the following, when the commercial power supply voltage is determined to be lower than a predetermined value by the power supply voltage monitoring unit, the succeeding recording paper An image forming apparatus, wherein a blank recording sheet is conveyed without performing the image generation process that should be performed in step 1, and without generating the toner image by the toner image generating means. 5. A toner image generating means for generating a toner image on a recording paper at a predetermined paper conveying speed, and a recording paper on the surface of which the toner image is generated by the toner image generating means is brought into contact with a predetermined pressure, and A fixing unit that fixes the toner image on the recording paper at the paper conveying speed by heating the contact unit, and the electric power received from the commercial power source is transmitted to the fixing unit to keep the temperature of the contact unit at a desired temperature. In the image forming apparatus including a temperature control unit, a power supply voltage monitoring unit that monitors the voltage of the commercial power supply, and a conveyance driving unit that is mechanically connected to the toner image generation unit and the fixing unit, An image forming apparatus, characterized in that when the monitoring means determines that the commercial power supply voltage has dropped below a predetermined value, the power supply to the conveyance drive means is cut off.