Electrophotography – Control of electrophotography process – Control of fixing
Reexamination Certificate
2001-05-23
2003-03-25
Ngo, Hoang (Department: 2852)
Electrophotography
Control of electrophotography process
Control of fixing
C399S069000, C399S021000, C219S216000
Reexamination Certificate
active
06539185
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a fixing apparatus which has a heating roller having a heating means inside and a pressing roller being in pressure contact with said heating roller, and makes a transfer material having a toner image transferred on it pass between the above-described heating roller and pressing roller to thermally fix said toner image to said transfer material.
In conventional fixing apparatus, when the driving operation for the heating roller is stopped at the time of completion of the fixing operation, occurrence of jams, etc., the heating operation for the heating means equipped on the heating roller is also stopped at the same time.
In the abovementioned fixing apparatus, however, a quantity of heat being necessary during driving the heating roller is greater than a quantity of heat being necessary during stopping the heating roller, due to influence of loses of heat dispersing to the pressing roller and into the ambient atmosphere.
Accordingly, in case that the hating means is still driven just before the heating roller is stopped, the heating roller stores an excessive quantity of heat in it after it stops.
There has been a problem that, as shown in
FIG. 27
, when the heating roller stops in the abovementioned situation, a transient overshoot (to exceed a predetermined temperature) is generated in the temperature characteristic on the surface of the heating roller due to the excessive quantity of heat, resulting in deterioration of the surface layer durability of the heating roller and activation of an extraordinary high-temperature alarm of the fixing apparatus.
In addition, recently, the thickness of the heating roller base body has been made as thinner as possible to reduce its heat capacity in the saving energy point of view.
In this case, as shown in
FIG. 28
, the thinner the thickness of the heating roller base body, the larger the amount of the overshoot.
SUMMARY OF THE INVENTION
To overcome the abovementioned drawbacks in conventional fixing apparatus, it is an object of the present invention to provide a fixing apparatus, which makes it possible to suppress a temperature overshoot of the heating roller when the heating roller is stopped.
Accordingly, to overcome the cited shortcomings, the abovementioned object of the present invention can be attained by fixing apparatus and image-forming apparatus described as follow.
(1) A fixing apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; and a cooling device to cool the heating roller; wherein the cooling device is activated during a predetermined time period after consecutive fixing operations are completed.
(2) The fixing apparatus of item 1, wherein the consecutive fixing operations correspond to a number of prints included in a JOB designated in advance.
(3) The fixing apparatus of item 1, wherein a cooling region cooled by the cooling device is variable in a longitudinal direction of the heating roller.
(4) A fixing apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a temperature detecting device to detect a temperature of the heating roller; and a cooling device to cool the heating roller; wherein the cooling device is activated after consecutive fixing operations are completed, so as to lower the temperature of the heating roller to a predetermined temperature based on a result detected by the temperature detecting device.
(5) The fixing apparatus of item 4, wherein the consecutive fixing operations correspond to a number of prints included in a JOB designated in advance.
(6) A fixing apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; and a cooling device to cool the heating roller; wherein, in case of a jam occurrence, the heating element is deactivated and the cooling device is activated until a jam-processing is completed.
(7) The fixing apparatus of item 6, further comprising: a temperature detecting device to detect a temperature of the heating roller; wherein the cooling device is deactivated either when the jam processing is completed or when the temperature of the heating roller is lowered to a predetermined temperature based on a result detected by the temperature detecting device.
(8) The fixing apparatus of item 6, wherein the cooling device is deactivated either when the jam processing is completed or when a predetermined time period has elapsed.
(9) The fixing apparatus of item 6, wherein a cooling region cooled by the cooling device is variable in a longitudinal direction of the heating roller.
(10) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; and a cooling device to cool the heating roller; and a control section to activate the cooling device during a predetermined time period after consecutive fixing operations are completed.
(11) The image-forming apparatus of item 10, wherein a cooling region cooled by the cooling device is variable.
(12) The image-forming apparatus of item 11, wherein the cooling device comprises a plurality of fans arrayed in a longitudinal direction of the heating roller, and the image-forming apparatus further comprising: a cooling region varying device to shade the heating roller from wind blown by several fans included in a plurality of the fans, in order to vary a cooling region cooled by the cooling device.
(13) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller, a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a temperature detecting device to detect a temperature of the heating roller; a cooling device to cool the heating roller; and a control section to activate the cooling device after consecutive fixing operations are completed, so as to lower the temperature of the heating roller to a predetermined temperature based on a result detected by the temperature detecting device.
(14) An image-forming apparatus, comprising: a heating roller; a heating element disposed in the heating roller; a pressing roller pressure-contacting the heating roller to fix an image onto a transfer sheet passing through a pressure-contacting section between the heating roller and the pressing roller; a cooling device to cool the heating roller; a jam-detecting device to detect a jam occurrence; and a control section to deactivate the heating element and to activate the cooling device when the jam-detecting device detects the jam occurrence, until a jam-processing is completed.
(15) The image-forming apparatus of item 14, further comprising: a door member to be opened and closed when the jam-processing is performed; and a door status detecting device to detect an opened or closed status of the door member; wherein the control section deactivates the cooling device and activates again the heating element when the jam-detecting device detects a completion of the jam-processing and the door status detecting device detects the closed status of the door member.
(16) The image-forming apparatus of item 14, further comprising: a temperature detecting device to detect a temperature of the heating roller; wherein the control se
Anzai Eiji
Fujita Shinsuke
Hanyu Naohiko
Motoyoshi Tomoya
Tamura Yuji
Frishauf Holtz Goodman & Chick P.C.
Konica Corporation
Ngo Hoang
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