Electrophotography – Internal machine environment – Forced air circulation
Reexamination Certificate
2000-05-03
2001-11-27
Beatty, Robert (Department: 2852)
Electrophotography
Internal machine environment
Forced air circulation
Reexamination Certificate
active
06324361
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cooling control unit and a method therefore for an electrophotographic apparatus, which fixed toner onto a sheet of paper during printing by controlling temperature to a printing temperature, and upon stoppage, cools an increase in temperature caused by a fixing unit and the like. More particularly, the invention relates to a cooling control unit and a method therefor for an electrophotographic apparatus, which controls a cooling fan by predicting an increase in temperature from the control status of the fixing unit without the need for a temperature sensor.
2. Description of the Related Arts
In a conventional electrophotographic apparatus such as a laser printer, provided with an apparatus cooling fan, toner is fixed on a sheet of paper by temperature-controlling a heater of a fixing unit. The fixing unit is controlled to a printing temperature of, for example, 150° C. during printing, and to a standby temperature of, for example, 120° C. during stoppage of printing. A cooling fan is therefore provided for the purpose of inhibiting an increase in machine internal temperature of the electrophotographic apparatus. The cooling fan is forcedly cooled through circulation of air under rotational control during printing. In a printing standby state of waiting printing, however, various motors for printing control are not driven, the cooling fan left to be driven only shows up wind howls. The wind howls may be prevented by discontinuing driving of the fan during stoppage of printing. Immediately after end of printing operation, however, the heat from heat generating components such as the heater of the fixing unit during printing causes an increase in the machine internal temperature. As a result, when fan driving is discontinued with stoppage of printing, there occurs an overshoot in which the machine internal temperature in creases over a safety temperature range, and the increase in temperature may cause occurrence of toner blocking or breakage of electric parts. In order to avoid this inconvenience, it is necessary to keep driving the fan for a certain period of time after stoppage of printing, or continue fan driving until the machine internal temperature is reduced to a safe level by providing a machine internal temperature sensor.
However, in a configuration in which the fan is driven for a certain period of time after stoppage of printing, it is necessary to drive the fan for the certain period of time even when the period of printing operation is short and the machine internal temperature is not so high, and during this certain period, occurrence of noise caused by extra fan driving poses a problem. In a configuration in which fan driving is continued until the machine internal temperature decreases to a safe level by providing an internal temperature sensor, the timing to stop the fan can be accurately known, but it is necessary to install the temperature sensor in the apparatus, thus leading to problem of a complicated apparatus configuration and a higher cost.
SUMMARY OF THE INVENTION
According to the present invention, there are provided a cooling control unit for an electrophotographic apparatus and a method therefor which can inhibit an increase in temperature after stoppage of printing without fail with minimum necessary driving of a cooling fan without the need for a temperature sensor.
The invention relates to an electrophotographic apparatus comprising a fixing unit, of which the temperature in controlled to prescribed printing temperature by a heater during printing to fix toner to a sheet of paper, and controlled to a prescribed standby temperature during stoppage; and a cooling fan rotation-controlled to prevent increase in the machine internal temperature. The invention provides a cooling control unit for such an electrophotographic apparatus comprising a ratio detecting unit which detects, during stoppage of printing, a fixing control ratio representing a ratio of time during which the fixing unit is controlled to the printing temperature for a certain period of time in the past; a predicting unit which predicts a fan driving time after stoppage of printing in response to the fixing control ratio; and a cooling fan control unit which rotation-controls a cooling fan during printing, and upon stoppage of printing, keeps a fan control status of printing during the prescribed period of time. The predicting unit predicts a fan driving time after stoppage of printing increasing substantially in proportion to the fixing control ratio K. The cooling fan control unit rotates the cooling fan at a prescribed speed, and upon stoppage of printing, stop the cooling fan after rotating the same for the predicted time. The cooling fan control unit may rotate the cooling fan at a high speed during printing, and upon stoppage of printing, may keep high-speed rotation of the cooling fan for the predicted time and then the rotation may be switched over to low-speed rotation. In the invention, as described above, the time of fan stoppage from the end of printing or switching to low-speed fan rotation is determined by predicting an increase in machine internal temperature at the end of printing on the basis of the fixing control ratio which represent the ratio of time during which the fixing unit was at the printing temperature for printing during a certain period of time in the past. More specifically since a larger fixing control ratio most probably leads to a large increase in machine internal temperature, fan operation is continued for a rather long period of time from stoppage of printing. In contrast, because a small fixing control ratio leads to small increase in machine internal temperature, fan operation is carried out for a shorter period of time from stoppage of printing. It is thus possible to keep the machine internal temperature after stoppage of printing at a safe level of temperature without the need for a sensor, minimize the driving time of the fan, and reduce noise during standby and avoid an excessive power consumption.
Further, the invention provides a cooling control method of an electrophotographic apparatus having a fixing unit, of which the temperature is controlled by a heater to a prescribed printing temperature during printing to fix toner on a sheet of paper, and upon stoppage of printing, controlled to a prescribed standby temperature, and a cooling fan rotation-controlled to prevent increase in the machine internal temperature; the method comprising the steps of:
detecting, during stoppage of printing, a fixing control ratio representing a ratio of time during which the fixing unit is controlled to a printing temperature in a certain period of time in the past;
predicting a fan driving time after stoppage of printing in response to the fixing control ratio; and
rotation-controlling the cooling fan during printing, and upon stoppage of printing, keeping a fan control status for printing during the predicted time.
Details of this cooling control method are basically the same as those of the apparatus configuration.
The above and other object, features, and advantages of the present invention will become more apparatus from the following detailed description with reference to the drawings.
REFERENCES:
patent: 5647727 (1997-07-01), Taniguchi et al.
patent: 5666187 (1997-09-01), Kim
patent: 5819136 (1998-10-01), Tomita et al.
patent: 5920749 (1999-07-01), Sugaya et al.
patent: 62-148986 (1987-07-01), None
patent: 63-159873 (1988-07-01), None
patent: 63-301063 (1988-12-01), None
patent: 04-084309 (1992-03-01), None
patent: 04-250473 (1992-09-01), None
patent: 04-316061 (1992-11-01), None
Itoh Fumihiro
Kojima Takeo
Watanabe Yoshihiro
Armstrong Westerman Hattori McLeland & Naughton LLP
Beatty Robert
Fujitsu Limited
LandOfFree
Cooling unit and method of cooling an electrophotographic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cooling unit and method of cooling an electrophotographic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cooling unit and method of cooling an electrophotographic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2599497