Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
2000-08-02
2001-06-12
Leung, Philip H. (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S652000, C219S670000, C219S674000, C219S676000, C399S330000, C399S336000
Reexamination Certificate
active
06246036
ABSTRACT:
This application is based on application No. 11-224570 field in Japan, the contents of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a fusing device used in an image forming apparatus such as an electrophotographic copying machine, printer or facsimile, and more particularly, to a fusing device that fuses a toner image to a recording medium using low-frequency induction heating.
2. Description of the Related Art
An electrophotographic copying machine, printer or facsimile has a fusing device that fuses onto a sheet a toner image formed on the sheet, which comprises the recording medium. While various methods may be used by the fusing device, fusing devices using the induction heating method have been proposed in response to the recent demand for energy conservation.
For example, Japanese Laid-Open Patent application Hei 10-123862 discloses an induction heating fusing device in which a core that forms a closed magnetic circuit runs through a conducive fusing roller and a coil comprising spirally formed wire is coaxially located inside the fusing roller. In this fusing device, a magnetic flux is caused inside the core by supplying electric current to the coil, and the magnetic flux induces an inductive current in the fusing roller so that the fusing roller is heated by means of Joule heating.
Due to the direct heating of the heating member, such as the fusing roller, by means of electromagnetic induction, a fusing device using the induction heating method has higher heat conversion efficiency than the halogen lamp heating method. Consequently, the temperature of the surface of the fusing roller may be quickly increased to the fusing temperature using a smaller amount of power, thereby satisfying the demand for energy conservation. In particular, devices having a core that forms a closed magnetic circuit, as in the laid-open patent application described above, exhibits little leakage of the magnetic flux, and can efficiently induce a secondary electric current in the fusing roller, offering a high energy conservation effect. They are therefore suited for large high-speed copying machines and high-speed printers.
In the induction heating fusing device disclosed in the laid-open patent application referred to above, the core comprises a first iron core and a second iron core that is rotatably mounted to the first iron core, and the fusing roller may be mounted or removed by opening the first and second iron cores relative to each other.
Using this conventional induction heating fusing device, the fusing roller may be easily mounted or removed. However, because the mounting or removal of the fusing roller is performed by opening the first and second iron cores relative to each other, an operation that is somewhat complex for a general user must be performed. Therefore, an induction heating fusing device that allows the user to be able to replace the fusing roller more easily is desired.
OBJECTS AND SUMMARY
In view of the situation described above, the object of the present invention is to provide an improved induction heating fusing device.
Another object of the present invention is to provide an induction heating fusing device that allows easy maintenance.
Yet another object of the present invention is to provide an induction heating fusing device that allows easy replacement of the rotary heating member such as the fusing roller.
Yet another object of the present invention is to provide an induction heating fusing device through which the cost of replacement of the rotary heating member such as the fusing roller may be reduced.
In order to attain those and other objects, according to one aspect of the present invention, the induction heating fusing device has:
a hollow rotary heating member that is made of a conductive material and heated based on induction heating;
a rotary pressure member that is in contact with the rotary heating member and that holds between itself and the rotary heating member the recording medium carrying toner;
a core that forms a closed magnetic circuit and that may be separated into a first core component that runs through the empty space of the rotary heating member and a second core component that is located outside the empty space of the rotary heating member,
an inductive coil that is located around the first core component and that heats the rotary heating member based on induction heating;
a casing that holds the rotary heating member, the first core component and the inductive coil; and
a support mechanism that supports the casing holding the rotary heating member, the first core component and the inductive coil so that it may be separated and removed from the second core component.
Using this induction heating fusing device, the core, which forms a closed magnetic circuit, comprises first and second core components that may be separated from each other, and the casing that holds the rotary heating member and the first core component, as well as the inductive coil, may be separated and removed from the second core component. Therefore, when the rotary heating member is replaced, it is not necessary to remove the second core component, and the weight of the unit that must be removed (the rotary heating member, the first core component, the inductive coil and the casing) is reduced. In addition, since the complex operation to open the cores referred to with regard to the conventional induction heating fusing device is not necessary, the rotary heating member may be replaced more easily. Furthermore, since the second core component is repeatedly used, the unit price of the fusing device may be reduced in comparison with the situation in which the entire core is replaced.
Moreover, according to another aspect of the present invention, the induction heating fusing device also has a pressure mechanism that places the end surfaces of the first core component and the end surfaces of the second core component in pressure contact with each other.
Using this mechanism, because the end surfaces of the first core component and the end surfaces of the second core component are pressed onto each other without a gap in between, the magnetic resistance of the entire core does not increase and the rotary heating member may be efficiently heated, leading to a larger energy conservation effect.
REFERENCES:
patent: 5970299 (1999-10-01), Sano et al.
patent: 6049691 (2000-04-01), Abe et al.
patent: 10-123862 (1998-05-01), None
Takasu Akira
Tsujimoto Takahiro
Leung Philip H.
McDermott & Will & Emery
Minolta Co. , Ltd.
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