Electrophotography – Image formation – Fixing
Reexamination Certificate
2000-09-12
2003-07-22
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Fixing
Reexamination Certificate
active
06597888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image heating apparatus which is applied to an image forming apparatus such as a copying machine or a printer, and more specifically an apparatus which utilizes an endless belt.
2. Related Background Art
For convenience, description will be made taking as an example an image heating apparatus (fixing apparatus) which is used in an image forming apparatus such as a copying machine or a printer for heating a toner image and fixing the toner image to a recording material.
A heating roller type image forming apparatus is widely used as a fixing apparatus which heats and fixes, as an image permanently fixed on a surface of a recording material, an unfixed image (toner image) of image data which is formed and born (carried) in a transfer mode or a direct mode on a recording material (transfer material sheet, Electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, format paper or the like) by adequate image forming process means such as an electrophotographic process, an electrographic recording process or a magnetic recording process.
A heater contact film heating type apparatus has recently been put to practical use from viewpoints of quick start and energy saving. Furthermore, an electromagnetic induction heating type apparatus has been also proposed.
a) Heating Roller Type Fixing Apparatus
A heating roller type fixing apparatus has a basic configuration of a pair of pressure contact rollers consisting of a fixing roller (heating roller) and a pressurizing roller, and functions to introduce a recording material on which an unfixed toner image to be fixed is formed and carried into a fixing nip section (heating nip section) which is a mutual contact portion between the above described pair of rollers, sandwich and carry the recording material, and heat the unfixed toner image and fix the image to a surface of the recording material with heat of the fixing roller and a pressurizing force of the fixing nip section.
The fixing roller is generally composed of a hollow metal roller of aluminum as a base body (core metal) and a halogen lamp disposed in a hollow space as a heat source and is heated by heat generated by the halogen lamp, and power supply to the halogen lamp is controlled so as to maintain an outer circumferential surface of the fixing roller at a predetermined fixing temperature.
In case of a fixing apparatus of an image forming apparatus for forming an image in full colors which must have a capability to mix colors by sufficiently heating and melting four toner image layers at maximum and allows fixing to be improper due to insufficient heating down to an interface between a recording material and a toner layer in particular, an elastic layer of rubber is disposed so that a core metal of a fixing roller has a large heat capacity and a toner image is melted uniformly in a condition wrapped in an outer circumference of the core metal, and the toner image is heated by way of the elastic layer of rubber. Further, a certain fixing apparatus is configured to use a heat source disposed also in a pressurizing roller so that the pressurizing roller is also heated and kept at a controlled temperature.
b) Heater Contact Film Heating Type Fixing Apparatus
Heater contact film heating type fixing apparatuses are proposed, for example, by Japanese Patent Application Laid-Open No. 63-313182, No. 2-157878, No. 4-44075 and No. 4-204980.
Concretely speaking, a heater contact film heating type fixing apparatus is configured to form a fixing nip section generally by sandwiching a heat resistant film (fixing film or fixing belt) between a ceramic heater used as a heating body and a pressurizing roller used as a pressurizing member, introduce a recording material on which an unfixed toner image to be fixed is formed and carried between the fixing film and the pressurizing roller in the above described fixing nip section, and sandwich and carry the recording material together with the fixing film, thereby imparting heat of the ceramic heater to the recording material by way of the fixing film in the fixing nip section and fixing the unfixed toner image to a surface of the recording material with heat and a pressing force of the fixing nip section (portion).
This film heating type fixing apparatus permits composing an on-demand type apparatus using members having low heat capacities as the ceramic heater and the fixing film, and requires power supply to the ceramic heater used as a heat source to set it in a condition heated to a predetermined fixing temperature only during execution of image formation by an image forming apparatus, thereby providing merits to shorten a wait time from a power on time of the image forming apparatus till a condition ready for the execution of image formation (a quick start property) and remarkably lower power consumption in a standby condition (power saving property).
c) Electromagnetic Induction Heating Type Fixing Apparatus
Japanese Utility Model Application Laid-Open No. 51-109739 discloses an induction heating fixing apparatus which induces an electric current in a fixing roller with a magnetic flux, thereby heating the fixing roller with Joule heat. This fixing apparatus is capable of directly heating the fixing roller by utilizing generation of an induced current and providing a fixing process with an efficiency higher than that of the heating roller type fixing apparatus which uses a halogen lamp as a heat source.
A high efficiency fixing apparatus has been contrived by bringing an excitation coil nearer a fixing roller used as a heat generating body to obtain a fixing energy at a high density or concentrating a distribution of an alternating magnetic flux of an excitation coil in the vicinity of a fixing nip section.
FIG. 16
shows a schematic configuration of an example of electromagnetic induction heating type fixing apparatus which has an efficiency enhanced by concentrating a distribution of an alternating magnetic flux of an excitation coil on a fixing nip.
Reference numeral
10
denotes a fixing belt (fixing film) in a form of an endless (cylindrical) belt which has electromagnetic induction heat generating layers (a layer of an electrically conductive material, a layer of a magnetic material and a layer of resistor material), and is configured as a heating rotating body generating heat by electromagnetic induction.
Reference numeral
16
denotes a belt guide member (film guide member) in a form of a conduit which has a cross section nearly of a semicircle and the endless belt
10
is loosely fitted outside the belt guide member
16
.
Reference numeral
15
denotes magnetic field producing means which is disposed inside the belt guide member
16
, and consists of excitation coils
18
and an E shaped magnetic core (core member)
17
.
Reference numeral
30
denotes an elastic pressurizing roller which is pressed under a predetermined force to a bottom surface of the belt guide member
16
with the fixing belt
10
interposed so as to form a fixing nip portion N having a predetermined width. The magnetic core
17
of the above described magnetic field producing means
15
is disposed at a location corresponding to the fixing nip portion N.
The pressurizing roller
30
is rotatingly driven by driving means M counterclockwise as indicated by an arrow. When the pressurizing roller
30
is rotatingly driven, a frictional force between the pressurizing roller
30
and an outside surface of the fixing belt
10
exerts a rotating force to the fixing belt
10
in the fixing nip portion N, whereby the fixing belt
10
is set in a condition where it rotates clockwise along an outer circumference of the belt guide member
16
at a circumferential speed nearly corresponding to a circumferential rotating speed of the pressurizing roller
30
while sliding in close contact with a bottom surface of the belt guide member
16
in the fixing nip portion N (pressurizing roller driving type).
The belt guide member
16
functions to apply a pressure to the fixing n
Abe Atsuyoshi
Suzuki Masahiro
Brase Sandra
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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