US 8,285,167 B2 · Fixing device

Abstract

A fixing device configured to fix a toner image on a moving printing medium includes: a fixing heat generator that generates heat by electromagnetic induction; a fixing medium that rotates and is heated while being carried by the heating medium; and a pressing member that presses a back surface of the printing medium coming into contact with the fixing medium, the fixing heat generator including a center coil and a pair of side coils provided at a center portion and both side portions thereof along a direction perpendicular to the direction of movement of the printing medium for heating the fixing medium by induction heating, the pressing member including a center heater and a side heater that heat a center portion and both side portions thereof in a direction perpendicular to the direction of movement of the printing medium integrated therein.

Drawings

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Drawings

Claims19

Dependent claims

A fixing device configured to fix a toner image on a moving printing medium, comprising:

a fixing heat generator that generates heat by electromagnetic induction;
a fixing medium that rotates and is heated;
and
a pressing member that presses a back surface of the printing medium which is brought into contact with the fixing medium, the fixing heat generator including a center coil and a pair of side coils provided at a center portion and both side portions thereof in terms of a perpendicular direction with respect to the direction of movement of the printing medium for heating the fixing medium by induction heating, the pressing member including a center heater and a side heater that heat the center portion and the side portions thereof in terms of the perpendicular direction with respect to the direction of movement of the printing medium respectively integrated therein, and further comprising:
a side temperature sensor that senses at least one of the temperatures of the both side portions of the pressing member in terms of a widthwise direction perpendicular to the direction of movement of the printing medium, and
a heater control unit that turns OFF the side heater if the temperature that the side temperature sensor senses exceeds a predetermined temperature while the fixing heat generator is operated at a constant power.

3 more elements

A fixing device configured to fix a toner image on a moving printing medium, comprising:

a fixing heat generator that generates heat by electromagnetic induction;
a fixing medium that rotates and is heated;
a pressing member that comes into press contact with a back surface of the printing medium which is brought into contact with the fixing medium,
the pressing member including a center heater and a side heater that heat a center portion and both side portions thereof in terms of a perpendicular direction with respect to the direction of movement of the printing medium respectively integrated therein,
the fixing heat generator including a center coil and a pair of side coils provided in the widthwise direction perpendicular to the direction of movement of the printing medium for heating the fixing medium by changing a duty ratio of the passage of electrical current through the center portion and the both side portions of the fixing medium,
a center temperature sensor and a side temperature sensor that sense the temperature of at least one of the center portion and the side portions of the pressing member and the fixing medium in terms of the widthwise direction perpendicular to the direction of rotation of the fixing medium,
a duty ratio control unit that prevents the temperature fall due to the printing medium passing through the inside the side temperature sensor by increasing the duty ratio of the passage of electrical current through the side coils if the temperature difference (Tps−Tpc) reaches or exceeds a predetermined temperature difference as a result of subtracting the temperature Tpc sensed by the center temperature sensor from the temperature Tps sensed by the side temperature sensor, and
a heater control unit that turns OFF the side heater if the temperature that the side temperature sensor senses exceeds a predetermined temperature while the fixing heat generator is operated at a constant power and turns ON the side heater if the temperature that the side temperature sensor senses falls below the predetermined temperature.

5 more elements

Dependencies are inferred from the claim text.

Description7,788 words

Summary1,828 words

#The present invention relates to a fixing device used in an image forming apparatus of an electrophotographic system and, more specifically to a fixing device having a structure including a plurality of heaters in a press roller.

#In an image forming apparatus such as an electrophotographic apparatus or the like, an electrostatic latent image is formed, and then the electrostatic latent image is developed by toner or the like, and a developed toner image is fixed to a printing sheet. In order to fix the image to the printing sheet, it is necessary to apply heat to the toner image and, normally, the fixation is achieved by heating the printing sheet having the toner image held thereon from the front surface with a fixing roller and applying a pressure from the back surface with a press roller.

#For example, heating of the fixing roller is achieved by winding a fixing belt between the fixing roller and a heat roller, heating the heat roller by a heater integrated in the heat roller, transferring the heat to the fixing belt, and transferring the transferred heat to the fixing roller (for example, JP-A-2001-318557).

Brief description of the drawings7 figures

#FIG. 1 is a drawing for explaining a problem of a fixing device in the related art.

#FIG. 2 is a drawing showing a relation between an induction heat device and a press roller in an embodiment of the invention.

#FIG. 3 is a cross-sectional view showing a structure of the fixing device according to the embodiment of the invention.

Detailed description5,807 words

#Referring now to the drawings, an embodiment of an image forming apparatus according to the invention will be described. The invention is applied to a case of heating a fixing belt and a fixing roller by an electromagnetic induction heating (IH) using divided coils, and is specifically effective for a fixing device in which the fixing belt and the fixing roller is directly heated from the outside.

#Referring now to FIG. 2 and FIG. 3, a configuration of the fixing device according to the embodiment of the invention will be described. FIG. 3 is a cross-sectional view showing the structure of the fixing device.

#The fixing device includes a fixing roller 30, a band-shaped fixing belt 31 wound around the fixing roller 30 and heated, a tension roller 32 around which the fixing belt 31 is wound for providing a tension to the belt, an induction heat coil 33 that heats the fixing belt 31 directly from the outside by the electromagnetic induction heating, an induction heat power source 34 that supplies a power to the induction heat coil 33, a fixing belt temperature sensor 35 that senses the surface temperature of the fixing belt 31, a fixing belt temperature control unit 36 that controls the induction heat power source 34 for controlling the temperature of an outer surface of the fixing belt according to the temperature sensed by the fixing belt temperature sensor 35, a press roller 37 provided so as to oppose the fixing roller 30 on which the fixing belt 31 is wound and brought into press contact with a printing sheet P from the back side thereof, a center heater 38a and a side heater 38b integrated in the press roller 37, a press roller temperature sensor 39 that senses the temperatures of the outer surfaces of the press roller 37, and a heater control unit 40 that controls the passage of electric current through the center heater 38a and the side heater 38b on the basis of the temperature that the press roller temperature sensor 39 senses.

Facts

Application

12/418,727Filed 6 Apr 2009 · us provisional application

Priority

10 Apr 2008

Published

US 2009/0257769 A115 Oct 2009

Granted

9 Oct 2012

Term ends

16 Jun 2030

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 436 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification2 codes

G03G 15/2039
Using contact heat: with means for controlling the fixing temperature
G03G
Electrography

Timeline

10 Apr 2008Priority claimedParent application 61/043,803
6 Apr 2009Application filedUS 12/418,727
6 Apr 2009Assigned to Kabushiki Kaisha Toshiba, Toshiba Tec Kabushiki Kaishaassignment of assignor's interest
15 Oct 2009PublishedUS 2009/0257769 A1
9 Oct 2012GrantedUS 8,285,167 B2
12 Oct 2026TodayWithin its term
16 Jun 2030Term endsEstimated, includes 436 days of adjustment

Fixing device

Life of this patent

Fixing device

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims19

Description7,788 words

Drawings

Classification2 codes

Life of this patent

Description7,788 words