JP2002251083A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit suitable for a low-priced thermally fixing device which enable the shortening of warm up time and quick start to be attained and can cope with electric power saving by using two electromagnetic induction heating coils of high heating efficiency. SOLUTION: A resonance condenser C1 is connected in parallel with either one among two heating coils M1 and M2 having different heat generation length which are disposed in a heating roller of an electromagnetic induction thermally fixing device incorporating a microcomputer P via a switch SW2, further connection is executed so that power source voltage V which is given by rectifying and smoothing a commercial power source AC by a rectifier circuit D is supplied via a switching element SW1 connected with an IC1 for driving and further the IC1 for driving and the switch SW2 are connected with the microcomputer P to constitute so that the power source voltage V is supplied to either one among the heating coil M1 and the heating coil M2 via the switch SW2 according to an output control signal S2 corresponding to a recording paper size change-over signal S1 inputted in the microcomputer P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electromagnetic induction heating for supplying high-frequency current to heating coils having different heat generation lengths which are wound in a circumferential direction and disposed in a heating roller constituting an image forming apparatus such as a copying machine. The present invention relates to a power supply circuit of a fixing device, and more particularly to a power supply circuit capable of saving power by switching a heating coil for heating according to a recording paper size.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, a fixing device for forming an image is provided, and a recording paper is formed by an appropriate image forming means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. (Transfer material sheet, electrostatic recording paper, electrofax paper, printing paper, etc.) to form and carry an image by transfer type or direct type, and the unfixed image (toner image) corresponding to the target image information is permanently stored on the recording paper surface. Fixed as an image. Conventionally, as shown in FIG. 3, a halogen lamp 4 serving as a heating source is inserted into a heating roller 3 made of aluminum or the like.
A heat fixing device 6A that is rotatably disposed and has a structure in which a pressure roller 5 is elastically contacted with a heating roller 3 is often used.

In the above-described heat fixing device 6A, heat generated by the halogen lamp 4 inserted inside the heating roller 3 and heat generated by light emission heat the heating roller 3 by radiation and convection.
Due to the heat conduction of the heating roller 3, the entire heating roller 3 has a uniform temperature distribution, and a permanent image is fixed on the recording paper 2 surface.

[0004]

However, the conventional heat fixing apparatus using the halogen lamp 4 has a drawback that the time required for the entire heating roller to have a uniform temperature distribution, that is, the so-called warm-up time, is long. However, it is difficult to respond to recent demands for power saving and quick start. For example, even if the heating range of the heating roller is changed according to the size of the recording paper, power can be saved by using a halogen heater with a single heating source. It was not possible to change the range.

Accordingly, an object of the present invention is to use two electromagnetic induction heating coils having high heating efficiency, to shorten the warm-up time and to enable quick start, and to be suitable for an inexpensive heat fixing device capable of coping with power saving. A power supply circuit is provided.

[0006]

According to a first aspect of the present invention, there are provided two heating coils M1 and M2 having different heating lengths and arranged in heating rollers of an electromagnetic induction heating fixing device having a microcomputer P therein.
A power supply circuit for supplying a high-frequency current to one of the two elements, wherein the heating element M1 or the heating element M2 and the resonance capacitor C1 are connected in parallel via a switch SW2, and the switching element is connected to the drive IC 1. Power supply voltage V obtained by rectifying and smoothing commercial power supply AC with rectifier circuit D via SW1
And the microcomputer P is connected to the drive IC 1 and the switch SW2, and the heating coil is switched via the switch SW2 by the output control signal S2 corresponding to the recording paper size switching signal S1 inputted to the microcomputer P. M
1, or a power supply circuit configured to supply a power supply voltage V to one of the heating coils M2. First
According to the point of view, the electromagnetic induction heating has a high heating efficiency, and the warm-up time can be reduced and a quick start can be performed. Further, by switching to the heating coils M1 and M2 having different heating lengths depending on the recording paper size, the heating range of the heating roller can be changed and power saving can be achieved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings. FIG. 1 is a block diagram illustrating an outline of a power supply circuit according to an embodiment of the present invention, and FIG. 2 is a simplified diagram illustrating a heating coil disposed in a heating roller. Note that the present invention is not limited by this.

-First Embodiment- In the drawings, reference numeral 3 denotes a heating roller made of a ferromagnetic iron, SUS430 or the like for electromagnetic induction constituting a heat fixing device 6A;
M1 and M2 are two heating coils having different heating lengths. Specifically, the heating coil M1 is set to the dimensions of the recording paper for A4 and A3, and is 300 mm to 340 mm in length, 20 mm in diameter, and 70 to 90 turns on the cylindrical coil bobbin 7 in the circumferential direction of the heating roller 3. The heating coil M2 is set to the dimensions of the recording paper for A4 and A3, and has a length of 25 mm on the heating coil M1 in the circumferential direction of the heating roller 3.
It is wound with 0mm-300mm, diameter 30mm, 70-90 turns.

Further, the heating coil M1 or the heating coil M2
Is connected in parallel with the resonance capacitor C1 by a mechanical switch SW2 such as a relay, and a transistor, FET, IG
The power supply voltage V rectified and smoothed by the rectifier circuit D is connected by a switching element SW1 made of a semiconductor element such as BT. Also, the switching element SW
1 is connected to the drive IC 1 controlled by the microcomputer P, and the switch SW2 is connected to the microcomputer P. Then, a recording paper size switching signal S1 is input to the microcomputer P,
An output control signal corresponding to the recording paper size switching signal S1
When S2 is output, the heating coil M1,
Alternatively, the switching is performed so that the power supply voltage V is supplied to one of the heating coils M2. The cylindrical coil bobbin 7
Has a Curie point of nickel or manganese inside
It is desirable to use a heat-resistant phenolic resin, ceramic, or the like on which a plurality of ferrite cores 9 of 200 ° or more are mounted.

In a power supply circuit having such a configuration, for example,
When the switching element SW1 is driven by switching to the heating coil M1 by the switch SW2, the heating coil M1 and the resonance capacitor C1 resonate at a resonance frequency of about 25 kHz. Generate. Then, a vortex induction current is generated on the surface of the heating roller 3 by the action of the magnetic flux, and is converted into Joule heat by the skin resistance of the heating roller 3 to heat the heating roller 3. Similarly, when the switching element SW1 is driven by switching to the heating coil M2 with the switch SW2, the heating coil M2 and the resonance capacitor C1 resonate at a resonance frequency of about 30 kHz, and the action of the magnetic flux generated from the heating coil M2 supplied with the high-frequency current is performed. As a result, a vortex induced current is generated on the surface of the heating roller 3, and this induced current is converted into Joule heat by the skin resistance of the heating roller 3, so that the heating roller 3 is heated.
Here, the constant of the resonance capacitor C1 is set in advance so as to correspond to the resonance frequency when the heating coils M1 and M2 are switched.

[0011] By the way, as the wire material for the heating coils M1 and M2, litz wire obtained by twisting 10 to 60 heat-resistant urethane wires having a wire diameter of 0.1 mm to 0.6 mm is used. , M2 can be reduced. Needless to say, a polyamide imide copper wire, a polyester imide copper wire or the like may be used as the wire for the heating coils M1 and M2.

Although not shown in detail, the heating roller 3 is made of a ferromagnetic and conductive iron or SUS430 and has a thickness of 0.1 mm to 1 mm and a magnetic conductive layer which facilitates peeling of the recording paper 2. The magnetic conductive layer is provided with a release layer having a thickness of 10 μm to 50 μm made of a fluorine-based heat-resistant resin formed on the outer peripheral side of the magnetic conductive layer. Heating coil M1,
Although M2 is provided, heating coils M1 and M2 themselves do not rotate.

The heat fixing device 6A has a basic structure of a pair of parallel pressing rollers of a heating roller 3 and a pressing roller 5,
By rotating the roller pairs 3,5, the recording paper 2 to be image-fixed is introduced into the heating nip portion 8, which is a pressure contact portion of the roller pairs 3,5, and nipped and conveyed. The unfixed image is heated and melted by the pressing force, soaked into the surface of the recording paper 2 and heat-fixed.

If the power supply circuit having such a configuration is used in the heating and fixing device, the electromagnetic induction heating has a high heating efficiency, a warm-up time is shortened, and a quick start becomes possible.
Further, if a heating coil having a different heating length is selected and heated according to the size of the recording paper, the heating range of the heating roller changes and power saving becomes possible.

[0015]

According to the present invention, it is possible to provide a heating fixing device which can shorten the warm-up time by simple means, has a high heating efficiency, and can respond to quick start. Further, since the heating range of the heating roller can be switched according to the size of the recording paper, power saving can be achieved. There is a great practical effect.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an outline of a power supply circuit according to an embodiment of the present invention.

FIG. 2 is a simplified diagram showing a heating coil disposed in a heating roller.

FIG. 3 is a perspective view illustrating a configuration of a main part of a heating roller in a conventional heat fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive IC 2 Recording paper 3 Heating roller 4 Halogen lamp 5 Pressure roller 6A Heating fixing device 7 Coil bobbin 8 Heating nip 9 Ferrite core AC commercial power supply C Resonant capacitor D Rectifier circuit M1, M2 Heating coil P Microcomputer SW1 Switching element SW2 Switch S1 Recording paper size switching signal S2 Output control signal V Power supply voltage

Claims (1)

[Claims] 1. A power supply circuit for supplying a high-frequency current to one of two heating coils M1 and M2 having different heating lengths disposed in a heating roller of an electromagnetic induction heating and fixing device incorporating a microcomputer P. The heating coil M1 or the heating coil M2 and the resonance capacitor C1 are connected in parallel via a switch SW2,
A commercial power supply AC is connected via a switching element SW1 connected to the drive IC 1 so as to supply a power supply voltage V rectified and smoothed by a rectifier circuit D, and the drive IC 1 and the switch SW2 are connected to the microcomputer P. Paper size switching signal input to
A power supply circuit configured to supply a power supply voltage V to one of the heating coil M1 and the heating coil M2 via the switch SW2 by an output control signal S2 corresponding to S1.