Electrophotography – Internal machine environment – Forced air circulation
Reexamination Certificate
2001-12-27
2003-06-17
Chen, Sophia S. (Department: 2852)
Electrophotography
Internal machine environment
Forced air circulation
C399S045000, C399S068000, C399S082000
Reexamination Certificate
active
06580884
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an image-forming device, a recording medium, and an image-forming device controlling method, and more particularly, to an image-forming device, such as a printer incorporating a heat-fixing device, and a multifunctional copying machine, to a recording medium, and to an image-forming device controlling method.
2. Description of the Related Art
Conventionally, in a well-known electrophotographic recording device (an image-forming device), such as a printer or a copying machine, which performs a printing by a heat-fixing method, a toner image formed on a photosensitive member is transferred to a recording paper by using an electrostatic power, and thereafter the recording paper bearing the toner image is conveyed to a heat-fixing device. In this heat-fixing device, while the recording paper is supported and conveyed by a fixing roller and a pressuring roller, a predetermined fixing heat is applied to the toner image on the recording paper under pressure imposed by nip portions of the fixing roller and the pressuring roller so as to fix the toner image on the recording paper. Such a heat-fixing device generally incorporates a heater generating a Joule heat in the fixing roller.
Since the temperature in the device may be excessively elevated due to the heat generated from the heater, the electrophotographic recording device further comprises a cooling fan revolving so as to prevent the temperature rise in the device.
However, the cooling fan is often laid out in the vicinity of the heat-fixing device; therefore, when the recording paper (especially the leading end thereof) enters the heat-fixing device, toner particles transferred to the recording paper flow around due to an air current generated by the cooling fan such that blurred images are likely and creases may be created in the recording paper. This effect is prominent especially when the recording paper is thinner than a predetermined thickness.
Thereupon, there has been proposed an image-forming device that reduces a revolving velocity (revolutions per unit time) of the cooling fan lower than normal throughout a conveyance path, and mechanically adjusts an amount of airflow, according to a type of a recording paper (Japanese Laid-Open Patent Application No. 07-319370).
Besides,
FIG. 1
shows a relation between a surface temperature of a fixing roller and an elapse time from the start of the fixing roller being revolved in a conventional heat-fixing device (a fixing unit). In
FIG. 1
, the axis of ordinates indicates the surface temperature of the fixing roller. T
FL
plotted on this ordinate axis indicates the lower limit of the fixing temperature. T
FH
indicates the upper limit of the fixing temperature. T
W
indicates a target value of the standby temperature. In
FIG. 1
, the surface temperature increases from the standby temperature T
W
to the upper limit T
FH
, and then decreases due to an effect of the cooling fan. Thereafter, the surface temperature is maintained at a temperature T
FO
above the lower limit T
FL
, while also being prevented from increasing excessively.
The technology disclosed in Japanese Laid-Open Patent Application No. 07-319370 can prevent the occurrence of the above-mentioned blurred images or creases by reducing the revolving velocity of the cooling fan lower than normal, especially when printing on a thin recording paper. However, an image-forming device is required not only to prevent ill influences due to an air current generated by revolutions of the cooling fan, but also to restrict a temperature increase in the device.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful image-forming device, a recording medium, and an image-forming device controlling method in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide an image-forming device, a recording medium, and an image-forming device controlling method which can not only prevent a transfer paper from being influenced by an air current generated by revolutions of a cooling fan, but also can sufficiently restrict a temperature increase in the image-forming device by revolving the cooling fan.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention an image-forming device comprising:
fixing means for fixing a toner visible image transferred to a transfer sheet;
feeding means for feeding and conveying the transfer sheet to the fixing means;
a cooling fan discharging a heat generated in the fixing means;
conveyance-position detecting means for detecting a conveyance position of the transfer sheet being conveyed; and
controlling means for controlling the cooling fan to start and stop revolving according to the conveyance position.
Normally, a cooling fan is used to prevent the temperature rise in an image-forming device. However, when a transfer sheet (especially the leading end thereof) enters a fixing device, toner particles transferred to the transfer sheet flow around due to an air current generated by the cooling fan such that blurred images are likely to be produced and creases may be created in the transfer sheet. Thereupon, by controlling the start/stop of the cooling fan according to the above-mentioned conveyance position, the air current generated by the cooling fan is prevented from affecting the transfer sheet after a transferring process until the completion of a fixing process. This makes it possible to eliminate the above-mentioned inconveniences of blurred images or creases in the transfer sheet, while keeping the reduction of cooling effects as little as possible.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention an image-forming device comprising:
fixing means for fixing a toner visible image transferred to a transfer sheet;
feeding means for feeding and conveying the transfer sheet to the fixing means;
a cooling fan discharging a heat generated in the fixing means by revolving at a variable revolving velocity;
conveyance-position detecting means for detecting a conveyance position of the transfer sheet being conveyed; and
controlling means for controlling the revolving velocity of the cooling fan according to the conveyance position.
When the revolving velocity (revolutions per unit time) of the cooling fan is variable, the revolving velocity of the cooling fan is controlled according to positions of the transfer sheet being conveyed. This makes it possible to prevent the reduction of cooling effects much further than when the start/stop of the cooling fan is controlled.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention an image-forming device comprising:
fixing means for fixing a toner visible image transferred to a transfer sheet;
feeding means for feeding and conveying the transfer sheet to the fixing means;
a cooling fan discharging a heat generated in the fixing means;
timing means for measuring a conveying time of the transfer sheet being conveyed; and
controlling means for calculating a conveyance position of the transfer sheet being conveyed, based on the conveying time and a predetermined conveying velocity, so as to control the cooling fan to start and stop revolving according to the conveyance position.
In cases where there are not provided conveyance sensors necessary for a cooling-fan control at sufficient positions on a conveyance path of the transfer sheet, a position of the transfer sheet being conveyed can be estimated by calculating a timing of the transfer sheet being conveyed, based on information detected by an existing conveyance sensor and a predetermined conveying velocity. Therefore, according to this estimation, the start/stop of the cooling fan can be controlled.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present inven
Chen Sophia S.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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