Electrophotography – Machine operation – Having power supply
Reexamination Certificate
2000-01-19
2001-08-21
Chen, Sophia S. (Department: 2852)
Electrophotography
Machine operation
Having power supply
C219S216000, C219S619000, C399S069000
Reexamination Certificate
active
06278852
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus such as a copier or a printer, and particularly to an image forming apparatus having a fixing device for fixing an unfixed image on a recording material.
2. Related Background Art
An image forming apparatus using the electrophotographic method usually has a fixing device for pinching and conveying a transfer material and a toner comprising resin, a magnetic material, a coloring material, etc. and electrostatically borne on the sheet material by the pressure contact portion (nip portion) between a fixing roller and a pressing roller brought into pressure contact with each other and being rotated and applying heat and pressure to them to thereby melt and fix the toner, and most of electric power consumed by the image forming apparatus is used by the fixing device.
In almost all of image forming apparatuses, maximum electric power usable by an entire image forming apparatus is set, and during the starting of the image forming apparatus, predetermined electric power of 70% or more of the maximum electric power is inputted to the fixing device dominating the apparatus starting time, and the other portions of the image forming apparatus are started by electric power within the remaining 30% and thus, the apparatus becomes ready for the image forming operation.
When the image forming operation is entered, the preset maximum electric power usable by the image forming apparatus, minus maximum electric power which may be consumed by the other portions than the fixing device, for example, an image forming portion, a scanner portion, a driving portion, an accessory portion, etc. at a time is maximum electric power usable by the fixing device during the image forming operation, and the value thereof is always constant.
However, if the maximum electric power usable by the fixing device when in the above-described image forming apparatus according to the prior art, a great deal of continuous printing is effected, for example, under low temperature environment is always constant, the temperature of the fixing roller will greatly fall from a target temperature due to the deficiency of electric power as shown in
FIG. 3
of the accompanying drawings to thereby cause bad fixing, or in order to avoid it, the printing speed must be reduced.
For example, description will now be made by the use of a fixing device using a halogen lamp as a heating source.
The reference numeral
100
in
FIG. 5
of the accompanying drawings designates a halogen heater, and a CPU
101
ON/OFF-controls electric power supplied from a power source outlet by a heater driver
104
having a switch on the basis of a temperature detected by a thermistor
103
for detecting the temperature of a fixing roller
105
. The reference numeral
106
denotes a thermoswitch for preventing the excessive temperature rise of the halogen lamp, and the reference numeral
107
designates a motor driver for driving the fixing roller.
In the fixing device using the halogen lamp as described above, the electric power from the outlet is directly supplied to the halogen lamp. The heat generating amount of the halogen lamp per unit time is determined by only the ratio between the ON time and the OFF time of the switch
104
provided in an electric power supply line, and maximum suppliable electric power is constant when the ON time is 100%.
It is the merit of the fixing device using the halogen lamp that although the maximum suppliable electric power cannot be changed, it need not have a power source and therefore the cost thereof is low.
Accordingly, when as previously described, more electric power is required in such a situation as a great deal of printing under low temperature environment, for example, a fixing device like the fixing device using the halogen lamp has had only such a countermeasure as interrupting the printing or reducing the printing speed.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-noted problem and an object thereof is to provide an image forming apparatus which fully makes the most of the capability of the apparatus.
Another object of the present invention is to provide an image forming apparatus which can carry out the maximum printing process within the range of a predetermined power consumption amount.
Still another object of the present invention is to provide an image forming apparatus designed such that if there is electric power not used in the apparatus, the electric power can be used as much as possible by a fixing device.
Yet still another object of the present invention is to provide an image forming apparatus comprising:
image forming means for forming an image on a recording material;
image fixing means for fixing the image onto the recording material, the image fixing means including an electric conductor, a coil for inducing an eddy current in the electric conductor, and a power supply for supplying an alternating current to the coil; and
electric power adjusting means for adjusting maximum electric power the power supply can supply to the coil.
Further objects of the present invention will become apparent from the following detailed description when read with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a cross-sectional view of a fixing device of the induction heating type used in the image forming apparatus of the present invention.
FIG. 2
represents the relations among a variation in the surface temperature of a fixing roller when the present invention is used, electric power used in portions except the fixing device and electric power used in the fixing device.
FIG. 3
represents the relations among a variation in the surface temperature of the fixing roller of a fixing device using a halogen heater, electric power used in portions except the fixing device and electric power used in the fixing device.
FIG. 4
is a simple cross-sectional view for illustrating the image forming apparatus of the present invention.
FIG. 5
schematically shows the construction of the fixing device using the halogen heater.
FIG. 6
shows the power supply circuit and temperature control circuit of a fixing device according to an embodiment of the present invention.
REFERENCES:
patent: 6006051 (1999-12-01), Tomita et al.
patent: 9-114312 (1997-05-01), None
patent: 9-160406 (1997-06-01), None
Canon Kabushiki Kaisha
Chen Sophia S.
Fitzpatrick ,Cella, Harper & Scinto
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