Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
2001-09-26
2002-11-19
Leung, Philip H. (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S670000, C219S672000, C219S675000, C399S330000
Reexamination Certificate
active
06483088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement of an electromagnetic induction heating device making use of an electromagnetic induction heating and an image recording device using such a heating device.
2. Related Art
Conventionally, as an image forming device such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, an image display device or an electrostatic recording device or the like, an image forming device which forms an image by following steps has been known. That is, a sensible image (an unfixed toner image) corresponding to target image information is formed on a surface of a recording member (an electronic-fax sheet, an electrostatic recording sheet, a transfer material sheet, a printing sheet or the like) in a direct method or an indirect (transfer) method using a toner made of heat-soluble resin or the like by a suitable image forming processing unit such as an electrophotography, an electrostatic recording, a magnetic recording or the like. Then, this recording member is guided and conveyed to a heating and fixing device (an image heating device) where a heating and fixing processing is performed to form the above-mentioned image as a permanently fixed image on a surface of the recording member.
As such a heating and fixing device (image heating device), a device which adopts a heat roller system or a film heating system has been widely used.
The heat roll system includes a basic constitution which includes, for example, a metal-made heating and fixing roller incorporating a heater therein and a pressure fixing roller having resiliency which is brought into pressure contact with the heating and fixing roller. By delivering the recording member in a fixing nip area defined by a pair of these fixing rollers, a toner image is fixed by heating and pressing.
In such a heat roller system, since the heat capacity of the fixing rollers is large, it takes a considerably long time to elevate the temperature of surfaces of the fixing rollers to a fixing temperature and hence, it necessitates a long warmup. Further, to shorten time necessary for delivering the first printing, it has been necessary to prepare a standby state so as to always place the fixing rollers in a heated state.
These days, however, to overcome such a problem, efforts have been made to lower the heat capacity of the fixing roller as much as possible and now have realized a level which can eliminate the standby state.
On the other hand, as the film heating system, a device includes, in its constitution, a heater as a heating body fixedly supported, a heat-resistant film which is conveyed while being brought into pressure contact with the heater in an opposed manner and a pressure applying member which makes an object to be heated come into close contact with the heater by way of the heat-resistant film and transmits the heat of the heater to the recording member by way of the heat-resistant film.
This film heating system is a device which adopts following steps as its basic constitution. That is, the heat-resistant film is made to travel in the normal direction at the same speed as the recording member on which an image is to be fixed and which is delivered between the heat-resistant film and the pressure member. Then, by making the recording member pass through a fixing nip area formed by a pressure contact of the heat-resistant film and the pressuring member, a sensible image carrying surface of the recording member is heated by the heater by way of the heat-resistant film so as to apply heat energy to the sensible image of the recording member thus softening or fusing the sensible image. Subsequently, after passing through the fixing nip area, the heat-resistant film and the recording member are separated at a separation point.
In these heat roller system and film heating system, as the pressure/fixing roller or the pressure member, a roller body made of silicone rubber or fluororubber which exhibits excellent heat resistance and mold release characteristics has been widely used in general.
Further, as the heater, a halogen lamp or a thermal heater of the low heat capacity has been used.
The heating and fixing device adopting such a heat roller system or a film heating system has suffered from following technical problems.
That is, when a roller or a film having a large thickness and hence having high rigidity is used in consideration of the durability, the high-speed processing or the like, the heat conduction is deteriorated or the heat capacity is increased so that the thermal response is lowered whereby the state which allows the rapid heating cannot be achieved.
In other words, the roller or the film having a large thickness becomes a thermal resistance and may deteriorate the heat transfer from the heater to the recording member which constitutes the object to be heated and hence, it becomes difficult to save energy and to realize the quick starting.
To solve these technical problems, inventors of the present application have extensively studied an electromagnetic induction heating device making use of the electromagnetic induction heating which can improve the thermal efficiency by making the roller per se or the film per se generate heat thus preventing the roller or the film from becoming the heat resistance.
In such an electromagnetic induction heating device, a magnetic field generated by a magnetic field generating unit which may be formed by combining a core made of magnetic material and an exciting coil, for example, is changed by an exciting circuit (for example, a circuit which applies high-frequency wave to the exciting coil) and a roller or a film which includes an electromagnetic induction heat generating layer (conductive member “induction magnetic material, magnetic field absorption conductive material”) and constitutes an object to be heated is made to pass through the generated magnetic field, and an eddy current is generated in the electromagnetic induction heat generating layer of the roller or the film due to the repetition of the generation and the extinction of the magnetic field (a fluctuation magnetic field).
In such a mode, the eddy current is transferred to heat (Joule heat) by the electric resistance of the electromagnetic induction heat generating layer and eventually only the roller or the film which is brought into close contact with the recording member which constitutes the object to be heated generates heat and hence, it becomes possible to provide a heating device capable of exhibiting the excellent thermal efficiency.
That is, when the fluctuating magnetic field traverses the inside of the conductive body (the electromagnetic induction heat generating layer in the roller or the film), the eddy current is generated in the electromagnetic induction heat generating layer of the roller or the film so as to generate a magnetic field which prevents the change of the magnetic field. Due to the skin resistance of the electromagnetic induction heat generating layer of the roller or the film, this eddy current makes the electromagnetic induction heat generating layer of the roller or the film generate heat proportional to the skin resistance.
Here, when the electromagnetic induction heat generating layer is formed close to a surface layer of the roller or the film, it becomes possible to make a portion of the roller or the film close to a surface layer directly generate heat and hence, an advantage that object to be heated can be rapidly heated irrespective of the thermal conductivity and the heat capacity of the roller or the base layer of the film.
Accordingly, it becomes possible to make the roller or the film base layer have a large thickness which ensures the high rigidity without damaging the energy saving and the quick start characteristics so that the roller or the film can satisfy the demand for high durability and the high-speed processing.
However, such an electromagnetic induction heating device still has following technical problems.
1) Since an elongated core around whi
Baba Motofumi
Uehara Yasuhiro
Fuji 'Xerox Co., Ltd.
Leung Philip H.
Oliff & Berridg,e PLC
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