JP2002184563A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce temperature stress in an electromagnetic induction heating material and aim at longer life, with a heating device 100 of electromagnetic induction heating system. SOLUTION: The heating device heating an object with heat generated by an electromagnetic induction heating material consisting of magnetic field generating means 17, 18, and a material 10 which generates heat by electromagnetic induction heating of the magnetic field generating means, and a pressure member 30 forming a nip part N of a heated member P by mutual pressure contacting with the electromagnetic induction heating material is provided with a first temperature detecting means 26 detecting the temperature at the nip part of the electromagnetic induction heating material and a second temperature detecting means 41 for measuring the temperature of the electromagnetic induction heating material generating heat by combination of magnetic field the field generating means generates. Exciting current impressed on an exciting coil of the field generating means is controlled based on the detected temperature of the first temperature detecting means, and at the same time, power to be supplied to the exciting coil is controlled based on the difference in the detected temperature by the first temperature detecting means and that of the second temperature detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heating device and an image forming apparatus. More specifically, the present invention relates to an electromagnetic induction heating type heating device and an image forming apparatus including the heating device as an image heating device (fixing device, fixing device).

[0002]

2. Description of the Related Art a) Heating roller type fixing device This is basically composed of a pressure roller pair of a fixing roller (heating roller) and a pressure roller, and the roller pair is rotated to form a mutual pressure contact portion of the roller pair. The recording material on which an unfixed toner image to be image-fixed is to be formed and carried is introduced and nipped and conveyed, and the unfixed toner image is formed by the heat of the fixing roller and the pressing force of the fixing nip. The fixing is performed by heat and pressure on the surface of the recording material.

The fixing roller generally has a hollow metal roller made of aluminum as a base (core metal), and a halogen lamp as a heat source is inserted in the hollow space thereof. The power supply to the halogen lamp is controlled to control the temperature so that the predetermined fixing temperature is maintained.

In particular, as a fixing device of an image forming apparatus for forming a full-color image, which is required to be capable of sufficiently heating and melting a maximum of four toner image layers to mix colors, a core metal of a fixing roller has a high heat capacity. And a rubber elastic layer for wrapping the toner image around the core metal and uniformly melting the toner image, and heating the toner image via the rubber elastic layer. There is also a configuration in which a heat source is provided in the pressure roller to heat and control the temperature of the pressure roller.

However, in the heat roller type fixing device, even if the power of the image forming apparatus is turned on and the energization of the halogen lamp which is the heat source of the fixing device is started at the same time, the heat capacity of the fixing roller is large and the fixing roller and the like are cooled. A considerable waiting time (wait time) is required from the cutting state to the rise to a predetermined fixable temperature, and the quick start property is lacking. Further, it is necessary to keep the fixing roller in a predetermined temperature control state by energizing the halogen lamp so that the image forming operation can be performed at any time even when the image forming apparatus is in a standby state (non-image output). There were problems such as a large amount.

In a fixing device having a particularly large heat capacity, such as the fixing device of the above-described full-color image forming apparatus, a delay occurs between the temperature control and the temperature rise of the fixing roller surface. Problems such as uneven gloss and offset have occurred.

B) Fixing device of film heating system A fixing device of the film heating system is disclosed in, for example, JP-A-63-3
Japanese Patent Application Laid-Open No. 13182, Japanese Patent Application Laid-Open No. 2-1577878, Japanese Patent Application Laid-Open No. 4-44075, Japanese Patent Application Laid-Open No. 4-204980, and the like.

That is, a fixing nip portion is formed by sandwiching a heat-resistant film (fixing film) between a ceramic heater as a heating element and a pressing roller as a pressing member. A recording material on which an unfixed toner image to be image-fixed is formed and supported is introduced between a pressure roller and the film is nipped and conveyed together with the film, so that the heat of the ceramic heater is recorded at the nip portion via the film. The unfixed toner image is heated and fixed on the surface of the recording material by applying pressure to the material and applying pressure at the nip portion.

This film heating type fixing device can be constituted as an on-demand type device using a ceramic heater and a member having a low heat capacity as a film, and a ceramic heater as a heat source only when the image forming apparatus executes image formation. To a state in which heat is generated to a predetermined fixing temperature, the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is greatly reduced. There are advantages such as small (power saving).

C) Fixing Device of Electromagnetic Induction Heating System JP-A-51-109739 discloses an induction heating fixing device in which a current is induced in a fixing roller by magnetic flux to generate heat by Joule heat. This makes it possible to directly generate heat in the fixing roller by utilizing the generation of an induced current, and achieves a more efficient fixing process than a heat roller type fixing device using a halogen lamp as a heat source.

However, since the energy of the alternating magnetic flux generated by the exciting coil as the magnetic field generating means is used to raise the temperature of the entire fixing roller, heat dissipation is large, and the density of fixing energy with respect to the input energy is low, resulting in poor efficiency. there were.

Therefore, in order to obtain the energy acting on the fixing at a high density, the exciting coil is brought closer to the fixing roller as a heating element, or the alternating magnetic flux distribution of the exciting coil is concentrated near the fixing nip portion. An efficient fusing device has been devised.

FIG. 18 shows a schematic configuration of an example of the electromagnetic induction heating type fixing device in which the alternating magnetic flux distribution of the exciting coil is concentrated in the fixing nip portion to improve the efficiency.

Reference numeral 10 denotes a cylindrical fixing film having an electromagnetic induction heating layer (a conductor layer, a magnetic layer, and a resistor layer) and serving as an electromagnetic induction heating rotating body.

Reference numeral 16 denotes a film guide member having a trough-like shape with a substantially semi-circular cross section. The cylindrical fixing film 10 is loosely fitted outside the film guide member 16.

Numeral 15 denotes a magnetic field generating means disposed inside the film guide member 16 and comprises an exciting coil 18 and an E-shaped magnetic core (core material) 17.

Numeral 30 denotes an elastic pressure roller as a pressure member, which forms a fixing nip portion N having a predetermined width with a predetermined pressing force with the fixing film 10 interposed therebetween and a predetermined width to form a fixing nip portion N. It is.

The magnetic core 17 of the magnetic field generating means 15 is disposed so as to correspond to the fixing nip portion N.

The pressing roller 30 is driven by a driving means M to rotate counterclockwise as indicated by an arrow. A rotational force acts on the fixing film 10 by a frictional force between the pressing roller 30 and the outer surface of the fixing film 10 due to the rotational driving of the pressing roller 30,
The fixing film 10 has a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 30 in the clockwise direction indicated by the arrow while the inner surface of the fixing film 10 slides in the fixing nip portion N in close contact with the lower surface of the film guide member 16. The outer periphery of the film guide member 16 is rotated (pressure roller driving method).

The film guide member 16 is provided with an exciting coil 18 as a means for applying pressure to the fixing nip N and generating a magnetic field 15.
And supports the magnetic core 17, supports the fixing film 10, and improves the transport stability when the film 10 rotates. The film guide member 16 is an insulating member that does not hinder the passage of magnetic flux, and is made of a material that can withstand a high load.

The exciting coil 18 generates an alternating magnetic flux by an alternating current supplied from an exciting circuit (not shown). The alternating magnetic flux is intensively distributed in the fixing nip N by the E-shaped magnetic core 17 corresponding to the position of the fixing nip N, and the alternating magnetic flux is applied to the electromagnetic induction heating layer of the fixing film 10 in the fixing nip N. Generates eddy currents. This eddy current generates Joule heat in the electromagnetic induction heating layer due to the specific resistance of the electromagnetic induction heating layer.

The electromagnetically induced heat of the fixing film 10 is intensively generated in the fixing nip N where the alternating magnetic flux is intensively distributed, and the fixing nip N is heated with high efficiency.

The temperature of the fixing nip N is controlled such that a predetermined temperature is maintained by controlling the current supply to the exciting coil 18 by a temperature control system including a temperature detecting means (not shown).

Thus, the pressure roller 30 is driven to rotate,
Accordingly, the cylindrical fixing film 10 rotates around the film guide member 16, and the power is supplied from the excitation circuit to the excitation coil 18 to generate the electromagnetic induction heat of the fixing film 10 as described above. The recording material P on which the unfixed toner image t is transported from the image forming unit (not shown) is fixed to the fixing film 10 in the fixing nip portion N and the pressure roller 30 in a state where the temperature is raised to the temperature of FIG. The image surface faces upward, that is, is introduced opposite to the fixing film surface, and at the fixing nip portion N, the image surface comes into close contact with the outer surface of the fixing film 10 so that the fixing film 10
Together with the fixing nip portion N. In the process of nipping and conveying the recording material P together with the fixing film 10 in the fixing nip N, the unfixed toner image t on the recording material P is heated and fixed by the electromagnetic induction heating of the fixing film 10. You. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing film 10 and discharged and conveyed.

The inverter circuit used for the electromagnetic induction heating power supply having such a configuration is roughly classified into a current resonance type power supply system and a voltage resonance system.

The reason why the resonance method is used is that when dealing with relatively large power, in order to reduce the loss of the switching element for conversion, the oscillation state of the voltage or current generated at the time of switching is generated positively and the switching element is most likely to be generated. A method of switching when the voltage or current and the value of both are low, called soft switching, is the most effective method for handling large power,
Various schemes have been proposed.

[0027]

A recording medium in which a film as an electromagnetic induction heating member is heated by magnetic induction heating, a nip portion is formed with the heated film, and an unfixed toner image is carried on the nip portion. In the method of obtaining a fixed image by passing a material, the portion closest to the toner image to be fixed can be directly heated, and the temperature of the fixing device can be rapidly increased by making the fixing film thinner. Is also possible.

However, while this rapid temperature rise is possible, for example, when the film is not rotating sufficiently for some reason, or when the film is broken due to trouble or the like, the nip is heated. Since the temperature of the temperature detecting means that controls the fixing temperature does not rise and the heating result is not reflected, the control becomes impossible, and the stationary film facing the exciting coil is continuously heated. And the film is significantly thermally degraded.

The present invention relates to a method for controlling the electromagnetic induction heating element when the film, that is, the electromagnetic induction heating element does not rotate sufficiently, or when the electromagnetic induction heating element is damaged and does not rotate. An object of the present invention is to reduce the temperature stress of a member and achieve a longer life.

[0030]

According to the present invention, there is provided a heating apparatus and an image forming apparatus having the following constitutions.

(1) A magnetic field generating means, a member that generates electromagnetic induction heat by the action of the magnetic field of the magnetic field generating means, and a pressing member that forms a nip portion of a member to be heated by mutual pressure contact with the electromagnetic induction heating member. A heating device for heating a member to be heated by the heat generated by the electromagnetic induction heating member, a first temperature detection unit for detecting a temperature of a nip portion of the electromagnetic induction heating member, and the magnetic field generation unit And a second temperature detecting means for measuring the temperature of the electromagnetic induction heating member that generates heat by coupling the magnetic field generated by the heating device.

(2) The magnetic field generating means has an exciting coil and a magnetic material forming a magnetic path, and the second temperature detecting means is arranged on the magnetic path formed by the magnetic material. A heating device as described.

(3) The exciting current applied to the exciting coil of the magnetic field generating means is controlled based on the temperature detected by the first temperature detecting means, and the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means are controlled. The heating device according to (1) or (2), wherein electric power supplied to the excitation coil is controlled based on a difference from the detected temperature.

(4) When the temperature detected by the second temperature detecting means exceeds at least a predetermined value, the current supplied to the exciting coil of the magnetic field generating means is cut off. A heating device according to any one of the above.

(5) The heating device according to any one of (1) to (4), wherein the heated member is a recording material carrying an image.

(6) In an image forming apparatus having an image forming means for forming and carrying an image on a recording material and an image heating means for heating an image on the recording material, the image heating means is (1)
An image forming apparatus, which is the heating apparatus according to any one of (1) to (4).

<Operation> That is, the present invention relates to a method for detecting the temperature of the electromagnetic induction heating member (fixing film) in the area of the magnetic path forming portion for heating the exciting coil of the magnetic field generating means by the second temperature detecting means. The current input to the excitation coil is limited or cut off by comparing and verifying with the detected temperature of the first temperature detecting means for temperature control, thereby mainly inputting the heating input of the electromagnetic induction heating member at rest. To prevent overheating.

If the electromagnetic induction heating member does not rotate sufficiently, or if the electromagnetic induction heating member does not rotate due to damage due to damage, etc., the exciting power is promptly reduced or cut off. By protecting the electromagnetic induction heating member, by providing a limit on the difference between the detected temperature of the first temperature detecting means and the detected temperature of the second temperature detecting means,
Reduce the temperature stress of the electromagnetically induced heat generating member and achieve a longer life.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (1) Example of Image Forming Apparatus First, an example of an image forming apparatus will be described. FIG. 1 is a configuration diagram illustrating a configuration of the image forming apparatus of the present embodiment. In the present embodiment, an example in which an electrophotographic color printer is used as an image forming apparatus will be described as an example, but the present invention is not limited to this.

The image forming apparatus is a fixing device (image heating device)
100, photosensitive drum (image carrier) 101, charging device 1
02, 4-color developing device 104, intermediate transfer drum 1
05, a transfer roller 106, cleaners 107 and 108, a mirror 109, a laser optical box (laser scanner) 110, and the like.

The structure of each part will be described in detail together with the operation. The photosensitive drum 101 is composed of an organic photosensitive member or an amorphous silicon photosensitive member, and is rotated at a predetermined process speed (peripheral speed) in a counterclockwise direction indicated by an arrow. It is driven to rotate.

The photosensitive drum 101 undergoes a uniform charging process of a predetermined polarity and potential by a charging device 102 such as a charging roller during the rotation process.

Next, the photosensitive drum 101 has a laser light 10 output from the laser optical box 110 on its charged surface.
3 is subjected to scanning exposure processing of the target image information. The laser optical box 110 is a laser beam 103 modulated (on / off) corresponding to a time-series electric digital pixel signal of target image information from an image signal generator such as an image reader (not shown).
To form an electrostatic latent image corresponding to the target image information scanned and exposed on the surface of the rotating photosensitive drum 101. The mirror 109 deflects the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.

In the case of a full-color image, scanning exposure and latent image formation are performed on a first color-separated component image of a target full-color image, for example, a yellow component image. Yellow developing unit 10
The image is developed as a yellow toner image by the operation of 4Y.

The yellow toner image is transferred onto the surface of the intermediate transfer drum 105 at a primary transfer portion T1, which is a contact portion (or a nearby portion) between the photosensitive drum 101 and the intermediate transfer drum 105.

After the transfer of the toner image onto the surface of the intermediate transfer drum 105, the rotating photoreceptor drum 101
7 removes adhered residues such as transfer residual toner and is cleaned.

The above-described process cycle of charging, scanning exposure, development, primary transfer, and cleaning is performed by a second color separation component image (eg, a magenta component image,
The magenta developing device 104M is activated), the third color-separated component image (for example, the cyan component image, the cyan developing device 104C is activated), and the fourth color-separated component image (for example, the black component image, the black developing device 104BK is activated). Each color separation component image is sequentially executed, and four toner images of a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred onto the surface of the intermediate transfer drum 105, and a desired full-color image is transferred. Are synthesized and formed.

The intermediate transfer drum 105 has a medium-resistance elastic layer and a high-resistance surface layer on a metal drum, and has the same peripheral speed as the photosensitive drum 101 in contact with or close to the photosensitive drum 101. Is rotated clockwise as indicated by the arrow, a bias potential is applied to the metal drum of the intermediate transfer drum 105, and the toner image on the photosensitive drum 101 is transferred to the surface of the intermediate transfer drum 105 by the potential difference from the photosensitive drum 101 Transfer to

The color toner image synthesized and formed on the surface of the rotating intermediate transfer drum 105 is subjected to the secondary transfer at a secondary transfer portion T2 which is a contact nip portion between the rotary intermediate transfer drum 105 and the transfer roller 106. The image is transferred onto the surface of a recording material (transfer material such as paper) P fed from a paper feeding unit (not shown) to the unit T2 at a predetermined timing. Transfer roller 10
Numeral 6 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, so that the combined color toner images are sequentially and collectively transferred from the surface of the intermediate transfer drum 105 to the recording material P.

The recording material P that has passed through the secondary transfer portion T2 is
The fixing device 1 separated from the surface of the intermediate transfer drum 105
The sheet is subjected to a heat fixing process for an unfixed toner image, and is discharged as a color image formed product to a discharge tray (not shown) outside the apparatus. Regarding the fixing device 100, the following (2)
It will be described in detail in the section.

After the transfer of the color toner image onto the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 by removing the residual toner such as untransferred toner and paper dust. The cleaner 108 is normally kept in a non-contact state with the intermediate transfer drum 105, and during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P, the intermediate transfer drum 10
5 is kept in contact.

The transfer roller 106 is also normally kept in a non-contact state with the intermediate transfer drum 105, and during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P, the intermediate transfer is performed. Body drum 1
At 05, the contact state is maintained via the recording material P.

The image forming apparatus of this embodiment can also execute a print mode of a monocolor image such as a black and white image.

Also, a double-sided image print mode or a multiple image print mode can be executed. In the case of the double-sided print mode, the recording material on which the first-side image printed out of the fixing device 100 has been turned upside down via a recirculation transport mechanism (not shown), and is again sent to the secondary transfer unit T2 to receive the two-sided image. Is transferred to the fixing device 100 again and subjected to the fixing process of the toner image on the two surfaces, whereby a double-sided image print is output.

In the case of the multiple image print mode, the recording material P on which the first image has been printed out of the fixing device 100 is
The toner image is transferred to the secondary transfer portion T2 again without being turned upside down via a recirculation transport mechanism (not shown), receives the second toner image transfer on the surface on which the first image is printed, and is again introduced into the fixing device 100. The multi-image print is output by receiving the second toner image fixing process.

(2) Fixing Device 100 Next, the fixing device 100 of the above-described image forming apparatus will be described. The fixing device 100 according to the present embodiment includes a pressure roller using a cylindrical fixing film (fixing belt) having an electromagnetic induction heating layer (a conductor layer, a magnetic layer, and a resistor layer) as the electromagnetic induction heating member. It is a driving system and an electromagnetic induction heating system.

FIG. 2 is a configuration diagram showing a cross-sectional side configuration of a main portion of the fixing device 100, FIG. 3 is a configuration diagram showing a front configuration of a main portion of the fixing device, and FIG. 4 is a vertical sectional front configuration of a main portion of the fixing device. FIG.

The structure of each part of the fixing device 100 will be described in detail.
The magnetic field generating means includes the magnetic cores 17a, 17b, 17c and the exciting coil 18.

The magnetic cores 17a, 17b, and 17c are members having high magnetic permeability, and are preferably made of a material such as ferrite or permalloy used for a transformer core.
It is preferable to use ferrite with little loss even at a frequency of 00 kHz or more.

The excitation circuit 27 (FIG. 5) is connected to the power supply sections 18a and 18b of the excitation coil 18. The excitation circuit 27 is an inverter power supply that generates a high frequency of 20 kHz to 500 kHz. The exciting coil 18 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the exciting circuit 27.

Reference numerals 16a and 16b denote film guides (belt guides) each having a substantially semicircular trough-shaped cross section. The film guides (belt guides) have a substantially cylindrical body with their opening sides facing each other, and a cylindrical electromagnetic induction heating member on the outside. The fixing film 10 is loosely fitted. The film guide member 16a holds therein magnetic cores 17a, 17b and 17c as magnetic field generating means and an excitation coil 18.

As shown in FIGS. 2 and 4, a good heat conducting member 40 is provided on the film guide member 16a inside the fixing film 10 on the side of the fixing nip portion N facing the pressure roller 30. I have. In this example, the good conductive member 40
Is made of aluminum. The good conductive member 40 has a thermal conductivity of k = 240 [W · m ⁻¹ · K ⁻¹ ] and a thickness of 1 [mm].

The good heat conducting member 40 includes an exciting coil 18 as a magnetic field generating means and magnetic cores 17a, 17b, 17
It is arranged outside this magnetic field so as not to be affected by the magnetic field generated from c. Specifically, the good conduction member 40 is disposed at a position separated by the magnetic core 17b with respect to the excitation coil 18 and positioned outside the magnetic path formed by the excitation coil 18 so as not to affect the good conduction member 40. I have to.

Reference numeral 22 denotes a horizontally-long pressurizing rigid stay disposed in contact with the flat surface of the inner surface of the film guide member 16b.

Reference numeral 19 denotes an insulating member for insulating the magnetic cores 17a, 17b, and 17c and the exciting coil 18 from the rigid pressurizing stay 22.

The flange members 23a and 23b are externally fitted to the left and right ends of the assembly of the film guide members 16a and 16b, and are rotatably mounted while fixing the left and right positions.
When the fixing film 10 rotates, the fixing film 10 receives the end of the fixing film 10 and serves to regulate the shifting of the fixing film along the length of the film guide member.

The pressure roller 30 serving as a pressure member is made of a heat-resistant and elastic material such as silicone rubber, fluoro rubber, fluoro resin, etc., which is formed by concentrically forming a roller around the core metal 30a. The core 30a is arranged so that both ends of the core 30a are rotatably supported by bearings between sheet metal (not shown) of the apparatus.

Pressing springs 25a and 25b are respectively contracted between both ends of the pressing rigid stay 22 and the spring receiving members 29a and 29b on the apparatus chassis side to apply a pressing force to the pressing constituting stay 22. ing. Thus, the lower surface of the film guide member 16a and the upper surface of the pressure roller 30 are pressed against each other with the fixing film 10 interposed therebetween, thereby forming a fixing nip portion N having a predetermined width.

The pressing roller 30 is driven by the driving means M to rotate in the counterclockwise direction indicated by the arrow. A rotational force acts on the fixing film 10 by a frictional force between the pressure roller 30 and the outer surface of the fixing film 10 due to the rotational driving of the pressure roller 30,
The fixing film 10 has a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 30 in the clockwise direction indicated by the arrow while the inner surface of the fixing film 10 slides in the fixing nip portion N in close contact with the lower surface of the good heat conducting member 40. Guide members 16a and 16b
Of the outside turns.

In this case, in order to reduce the mutual sliding friction force between the lower surface of the good heat conducting member 40 in the fixing nip N and the inner surface of the fixing film 10, the lower surface of the good heat conducting member 40 in the fixing nip N is fixed. A lubricant such as heat-resistant grease may be interposed between the inner surface of the film 10 and the lower surface of the good heat conductive member 40 may be covered with a lubricating member. This is because when the surface sliding property is not good in material such as when aluminum is used as the good heat conducting member 40 or when the finishing process is simplified, the sliding fixing film 10 is damaged and the fixing film 10 is damaged. This is to prevent the durability of the device from being deteriorated.

The good heat conducting member 40 has the effect of making the temperature distribution uniform in the longitudinal direction. For example, when small-size paper is passed as a recording material, the heat amount of the non-sheet passing portion of the fixing film 10 is good. The heat is transferred to the heat conducting member 40, and the amount of heat in the non-sheet passing portion is transferred to the small size sheet passing portion by the heat conduction in the longitudinal direction of the good heat conducting member 40. As a result, an effect of reducing power consumption when passing small-sized paper is also obtained.

Further, as shown in FIG. 5, the peripheral surface of the film guide member 16a is provided with convex ribs 16e at predetermined intervals along the length thereof, so that the peripheral surface of the film guide member 16a is fixed to the fixing film. The rotational load of the fixing film 10 is reduced by reducing the contact sliding resistance with the inner surface of the fixing film 10.

FIG. 6 schematically shows how alternating magnetic flux is generated. The magnetic flux C represents a part of the generated alternating magnetic flux. The alternating magnetic flux C guided to the magnetic cores 17a, 17b, and 17c causes the electromagnetic induction heating layer 1 of the fixing film 10 between the magnetic core 17a and the magnetic core 17b and between the magnetic core 17a and the magnetic core 17c (see FIG. 8. An eddy current is generated in FIG. This eddy current generates Joule heat (eddy current loss) in the electromagnetic induction heating layer 1 due to the specific resistance of the electromagnetic induction heating layer 1.

The heat value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heating layer 1 and has a distribution as shown in the graph of FIG. In the graph of FIG. 6, the vertical axis indicates the circumferential position in the fixing film 10 represented by an angle θ with the center of the magnetic core 17 a being 0, and the horizontal axis indicates the heat generation in the electromagnetic induction heating layer 1 of the fixing film 10. Indicates the quantity Q. Here, the heating area H is defined as an area where the heating value is Q / e or more, where Q is the maximum heating value. This is an amount by which heat generated for fixing can be obtained.

The temperature of the fixing nip N is detected by the first temperature detecting means 26 (FIG. 2), and a predetermined temperature is maintained by controlling the current supply to the exciting coil 18 by the temperature control system. The temperature is controlled.

The first temperature detecting means 26 is a temperature sensor such as a thermistor for detecting the temperature of the fixing film 10. In this embodiment, the temperature information of the fixing film 10 measured by the first temperature detecting means 26 is used. Based on this, the temperature of the fixing nip N is controlled.

When the fixing film 10 rotates, the power is supplied from the excitation circuit 27 to the excitation coil 18 to generate electromagnetic induction of the fixing film 10 as described above, and the fixing nip N rises to a predetermined temperature. In the temperature-controlled state, the recording material P on which the unfixed toner image t conveyed from the image forming unit is formed is positioned such that the image surface faces upward between the fixing film 10 in the fixing nip N and the pressure roller 30. That is, the fixing nip N
The image surface is brought into close contact with the outer surface of the fixing film 10 and the fixing nip N is conveyed together with the fixing film 10.

In the process in which the recording material P is nipped and conveyed in the fixing nip portion N together with the fixing film 10, the recording material P is heated by the electromagnetic induction heat of the fixing film 10.
The upper unfixed toner image t is heat-fixed. Recording material P
After passing through the fixing nip N, the toner is separated from the outer surface of the rotary fixing film 10 and is discharged and conveyed. After passing through the fixing nip, the heat-fixed toner image on the recording material is cooled and becomes a permanent fixed image.

In this embodiment, as shown in FIGS. 2, 5 and 6, the second temperature detecting means 41 is arranged at a position facing the heat generating area H (FIG. 6) of the fixing film 10. A thermoswitch 50 (FIGS. 2 and 7) as a temperature detecting element is also provided to cut off the power supply to the exciting coil 18 during a runaway.

In FIG. 2, the temperature of the recording material P is determined by a first temperature detecting means 26 disposed near the fixing nip N.
It has been obtained through experiments that the position of # 1 most reflects the fixing temperature. Of course, it is best if the temperature of the fixing nip portion N can be measured, but in the present embodiment, it is arranged in a portion immediately after the fixing nip portion from a practical arrangement.

The first temperature detecting means 2 thus arranged
6, when the fixing film 10 is rotated and an exciting current is applied to the exciting coil 18 to measure the temperature, the fixing nip side, that is, the first temperature detecting means 26 is pressurized as shown in FIG. The curve 400 gradually increases the temperature while the heat is taken by the roller 30. On the other hand, the portion of the second temperature detecting means 41 arranged on the side where the magnetic flux is coupled and heated is relatively steep because the electromagnetic induction heating layer 1 of the fixing film 10 is made of nickel metal having a thickness of about 50 μm. The rising curve 401 is shown.

Next, paying attention to the temperature change of the first and second temperature detecting means 26 and 41 arranged as above, FIG. 15 shows a state when the recording material (paper) is passed. I have. In FIG. 15, first temperature detecting means 26 used for temperature control
Is temperature controlled and stabilized as shown by the curve 400. On the other hand, the second temperature detecting means 41 provided in the heating unit
Is the fixing nip N due to the conveyance of the recording material (A and B periods).
As a result of power control to supply heat deprived in
The temperature rises during paper passing.

Here, the temperature curve when the fixing film 10 falls into a state where it does not rotate due to some accident or the like is shown from the point C onward in FIG. Since the fixing film 10 is stopped, even if it is heated, the temperature rise is not detected, and the maximum power is supplied to the exciting coil 18.

On the other hand, in the second temperature detecting means 41 on the side of the heating section, power is supplied in a stationary state to the thin nickel metal which is the electromagnetic induction heating layer 1 of the fixing film 10, so that the temperature rises rapidly. Show. Of course, if left in this state, the nickel metal which is the electromagnetic induction heating layer 1 of the fixing film 10 deteriorates or breaks in a few seconds.

In the present case, attention is paid to such a temperature gradient, and the detected temperature difference between the two first and second temperature detecting means 26 and 41 is detected, and the excitation coil 18 is switched according to the degree of the temperature difference. The power to be supplied is controlled.

In the above example, the temperature of the first temperature detecting means 26 for controlling the fixing temperature is lowered despite the supply of the electric power, and the first temperature detecting means 26 is further connected to the heating section. Since the value of the second temperature detecting means 41 is rapidly increasing, it can be determined from the profile that the cause of the accident is an abnormal rotation of the fixing film 10 by the value of C in FIG.

When the value of C is monitored and exceeds a predetermined value, the fixing film 10 is protected by a structure in which the current applied to the exciting coil 18 is cut off.

FIG. 16 shows a state where the rotation of the fixing film 10 has already become abnormal at the time of startup. Since the fixing film 10 has not been rotated since the initial stage, it can be easily inferred that only the temperature of the second temperature detecting means 41 on the heating section side shows a sudden rise.

Of course, the fixing device is configured to cut off the circuit by the thermoswitch 50 for the purpose of ensuring its safety. This will be described with reference to FIG.

FIG. 7 is a circuit diagram of the safety circuit used in this example. In order to cut off the power supply to the exciting coil 18 at the time of runaway, the thermo switch 50 which is a temperature detecting element is + 24VDC.
When the thermo switch 50 is turned off, the power supply to the relay switch 51 is cut off, the relay switch 51 is operated, and the power supply to the excitation circuit 27 is cut off. Coil 18
It is configured to cut off the power supply to the power supply. The thermoswitch 50 set the OFF operation temperature to 220 ° C.

Further, the thermoswitch 50 is disposed in a non-contact manner on the outer surface of the fixing film 10 so as to face the heat generating area H of the fixing film 10. Thermoswitch 50 and fixing film 1
The distance between 0 and 2 was approximately 2 mm. Accordingly, the fixing film 10 is not damaged by the contact of the thermoswitch 50, and the deterioration of the fixed image due to durability can be prevented.

According to the present embodiment, when the fixing device goes out of control due to a device failure, the fixing nip portion N like the fixing device of FIG.
Unlike the configuration in which the heat is generated, the fixing device stops in a state where the recording material (paper) P is sandwiched in the fixing nip portion N, and the power is continuously supplied to the excitation coil 18 so that the fixing film 10 continues to generate heat. Fixing nip N where recording material P is sandwiched
The recording material P is not directly heated because no heat is generated. Further, since the thermoswitch 50 is provided in the heat generation area H where the heat generation is large, the thermoswitch 50 is provided.
Senses 220 ° C., and when the thermoswitch 50 is turned off, the power supply to the exciting coil 18 is cut off by the relay switch 51. Further, according to this example, since the ignition temperature of the paper as the recording material is around 400 ° C., the heat generation of the fixing film 10 can be stopped without the paper being ignited.

In order to cut off the power supply to the exciting coil 18 at the time of runaway, a thermo fuse or the like of the thermoswitch 50 can be used as a temperature detecting element.

In this example, since a toner containing a low softening substance was used in the toner t, an oil application mechanism for preventing offset was not provided in the fixing device, but a toner not containing a low softening substance was used. In this case, an oil application mechanism may be provided. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.

Next, the excitation coil 18 and the fixing film 10 of the fixing device 100 will be described in more detail.

A) Excitation Coil 18 As the excitation coil 18, a bundle (bundled wire) of a plurality of copper thin wires, each of which is insulated and coated, is used as a conductor (electric wire) constituting the coil (wire loop). Are wound several times to form the exciting coil. In this example, the exciting coil 18 is formed by winding 10 turns.

As the insulating coating, a coating having heat resistance is preferably used in consideration of heat conduction due to heat generation of the fixing film 10. For example, a coating of amide imide or polyimide may be used. The excitation coil 18 may improve the density by applying pressure from the outside.

The shape of the exciting coil 18 conforms to the curved surface of the heat generating layer 1 of the fixing film 10 as shown in FIGS. In this embodiment, the distance between the heating layer 1 of the fixing film 10 and the exciting coil 18 is set to be approximately 2 mm.

As the material of the exciting coil holding member 19, a material having excellent insulation properties and good heat resistance is preferable. For example, a phenol resin, a fluorine resin, a polyimide resin, a polyamide resin, a polyamide imide resin, a PEEK resin, a PES resin, a PPS resin, a PFA resin, a PTFE resin, a FEP resin, and an LCP resin may be selected.

The closer the distance between the magnetic cores 17a, 17b, 17c and the exciting coil 18 and the heat generating layer 1 of the fixing film 10 is to the extent possible, the higher the efficiency of absorbing magnetic flux. However, this distance exceeds 5 mm. Since this efficiency is significantly reduced, it is preferable to keep the efficiency within 5 mm. If the distance is within 5 mm, the heating layer 1 of the fixing film 10 and the exciting coil 1
The distance of 8 need not be constant.

Excitation coil holding member 19 of excitation coil 18
As for the lead wires 18a and 18b (FIG. 5), the outside of the bundled wire is insulated for the portion outside the exciting coil holding member 19.

B) Fixing Film 10 FIG. 8 is a schematic diagram of the layer structure of the fixing film 10 in this example. The fixing film 10 according to the present embodiment has a heating layer 1 made of a metal or the like which is a base layer of the fixing film 10 having electromagnetic induction and heat.
And an elastic layer 2 laminated on its outer surface and a release layer 3 laminated on its outer surface. A primer layer (not shown) may be provided between each layer for adhesion between the heat generating layer 1 and the elastic layer 2 and adhesion between the elastic layer 2 and the release layer 3.

In the fixing film 10 having a substantially cylindrical shape, the heat generating layer 1 is on the inner side, and the release layer 3 is on the outer side.
As described above, when the alternating magnetic flux acts on the heat generating layer 1, an eddy current is generated in the heat generating layer 1, and the heat generating layer 1 generates heat. The heat heats the fixing film 10 via the elastic layer 2 and the release layer 3, and heats the recording material P, which is the material to be passed through the fixing nip portion N, to heat and fix the toner image. Done.

A. Heating Layer 1 The heating layer 1 is preferably made of a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, and nickel-cobalt alloy.

A non-magnetic metal may be used, but more preferably a metal such as nickel, iron, magnetic stainless steel, or a cobalt-nickel alloy having good magnetic flux absorption.

It is preferable that the thickness is larger than the skin depth represented by the following formula and 200 μm or less. The skin depth σ [m] is determined by the frequency f [Hz] of the excitation circuit and the magnetic permeability μ.
And σ = 503 × (ρ / fμ) ^1/2 .

This indicates the depth of absorption of electromagnetic waves used in electromagnetic induction. At a depth deeper than this, the intensity of the electromagnetic waves is 1 / e or less. (See FIG. 9). FIG. 9 is a diagram showing the relationship between the electromagnetic intensity and the depth of the heating layer.

The thickness of the heat generating layer 1 is preferably 1 to 100 μm.
m is good. If the thickness of the heat generating layer 1 is smaller than 1 μm, most of the electromagnetic energy cannot be absorbed, so that the efficiency is deteriorated. On the other hand, if the heat generating layer 1 has a thickness of more than 100 μm, the rigidity becomes too high, and the bendability deteriorates, which is not practical for use as a rotating body. Therefore, the thickness of the heating layer 1 is 1 to
100 μm is preferred.

B. Elastic Layer 2 The elastic layer 2 is made of silicone rubber, fluorine rubber, fluorosilicone rubber, or the like, and has good heat resistance and good thermal conductivity.

The thickness of the elastic layer 2 is preferably from 10 to 500 μm. The elastic layer 2 has a thickness necessary to guarantee the quality of a fixed image.

When a color image is printed, a solid image is formed over a large area on the recording material P, especially for a photographic image. In this case, if the heating surface (the release layer 3) cannot follow the unevenness of the recording material or the unevenness of the toner layer, uneven heating occurs, and uneven gloss occurs in the image in portions where the amount of heat transfer is large and small.

A portion having a large amount of heat transfer has a high gloss, and a portion having a small amount of heat transfer has a low gloss. When the thickness of the elastic layer 2 is 10 μm or less, the elastic layer 2 cannot follow the unevenness of the recording material or the toner layer, and the image gloss unevenness occurs. Also,
When the thickness of the elastic layer 2 is 1000 μm or more, the thermal resistance of the elastic layer 2 becomes large, and it is difficult to realize a quick start. More preferably, the thickness of the elastic layer 2 is 50 to 500.
μm is good.

If the hardness of the elastic layer 2 is too high, the elasticity of the elastic layer 2 cannot follow the irregularities of the recording material or the toner layer, resulting in uneven image gloss. Therefore, the hardness of the elastic layer 2 is preferably 60 ° or less (JIS-A: JIS-K (using an A-type measuring device)) or less, more preferably 45 ° or less.

Regarding the thermal conductivity λ of the elastic layer 2, 2.5
× 10 ^{-1 to} 8.4 × 10 ^-1 W / m · ° C. (6 × 10 ^-4 to 2
× 10 ⁻³ cal / cm · sec · deg. ) Is good.

Thermal conductivity λ is 2.5 × 10 ⁻¹ W / m · ° C.
If it is smaller than (6 × 10 ⁻⁴ cal / cm · sec · deg.), The thermal resistance is large, and the temperature rise in the surface layer (release layer 3) of the fixing film 10 becomes slow.

Thermal conductivity λ is 8.4 × 10 ^-1 W / m · ° C.
If it is larger than (2 × 10 ⁻³ cal / cm · sec · deg.), The hardness becomes too high or the compression set becomes worse.

Therefore, the thermal conductivity λ is 2.5 × 10 ⁻¹ to 8.
4 × 10 ⁻¹ W / m · ° C. (6 × 10 ⁻⁴ to 2 × 10 ⁻³ cal)
/ Cm · sec · deg. ) Is good. More preferably, 3.3 × 10 ^{-1 to} 6.3 × 10 ^-1 W / m · ° C. (8 × 10 ^{-1
−4 to} 1.5 × 10 ⁻³ cal / cm · sec · deg. )
Is good.

C. Release Layer 3 Release layer 3 is made of fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, P
A material having good releasability and heat resistance, such as TFE and FEP, can be selected.

The thickness of the release layer 3 is preferably 1 to 100 μm. If the thickness of the release layer 3 is less than 1 μm, there arises a problem that uneven coating of the coating film causes a part having poor releasability or insufficient durability.

If the thickness of the release layer is more than 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layer 2 is lost.

Further, as shown in FIG.
In the configuration of No. 0, the heat insulating layer 4 may be provided on the film guide member surface side of the heat generating layer 1 (the side opposite to the elastic layer 2 of the heat generating layer 1).

The heat insulating layer 4 is made of a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, PE
EK resin, PES resin, PPS resin, PFA resin, PT
A heat-resistant resin such as FE resin or FEP resin is preferable.

The thickness of the heat insulating layer 4 is 10 to 10
00 μm is preferred. When the thickness of the heat insulating layer 4 is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient. On the other hand, if it exceeds 1000 μm, the magnetic core 17
The distances from the a, 17b, and 17c and the exciting coil 18 to the heating layer 1 increase, and the magnetic flux is not sufficiently absorbed by the heating layer 1.

The heat insulating layer 4 can insulate the heat generated in the heat generating layer 1 so as not to go to the inside of the fixing film 10. Will be better. Therefore, power consumption can be suppressed.

FIG. 11 is a block diagram showing the overall configuration of the induction heating control section including the output converter. The induction heating control unit of the image forming apparatus includes a voltage control circuit 309, a fixing unit (Fuser) 311 and a feedback control circuit 3.
13, a driver circuit 314. Further, the voltage control circuit 309 includes an overcurrent breaker 302, a relay 3
03, rectifier circuit (RECT) 304, gate control transformers 305/306, voltage resonance switching circuit 307,
A current transformer 308 is provided.

Reference numeral 301 denotes a power line input terminal, and reference numeral 312 denotes a heating on / off signal of the fixing device.

The structure of the above-mentioned main parts will be described in detail together with the operation.
The overcurrent breaker 302 protects overcurrent. The rectifier circuit 304 includes a bridge rectifier circuit that performs double-wave rectification from an AC input and a capacitor that performs a high-frequency filter. The voltage resonance switching circuit 307 supplies power by performing current switching at a resonance cycle to a resonance circuit formed by an excitation coil of the fixing unit, which is a voltage resonance circuit, and a resonance capacitor included in the voltage resonance switching circuit. The current transformer 308 includes the voltage resonance switching circuit 3
At 07, a transformer for detecting the switched switching current is connected to the exciting coil 18 of the fixing device 100.

The fixing unit 311 includes the above-described exciting coil 18 (not shown in FIG. 11) as an electric component.
It has a first temperature detecting means 26 (temperature detecting thermistor, temperature sensor) 26, a second temperature detecting means 41 (temperature detecting thermistor, temperature sensor), and a thermoswitch 50 for detecting excessive temperature rise. The heating on / off signal 312 of the fixing device is sent from a sequence controller of an image forming apparatus (printer) (not shown).

The feedback control circuit 313 controls the control amount based on the first temperature detecting means 26 while comparing with the target temperature.

The driver circuit 314 receives the feedback control signal from the feedback control circuit 313, and controls the converter while comparing it with the target temperature.

When AC power is received from a power line input terminal 301 and AC power is applied to a rectifier circuit 304 via an overcurrent breaker 302 and a relay 303, a pulsating DC is generated by a double-wave rectifier diode of the rectifier circuit 304. Generate power.

Thereafter, the voltage resonance switching circuit 307
By driving the gate control transformers 305 and 306 so that the switching elements are alternately switched, a high-frequency voltage is applied to the exciting coil 18.

By controlling the current flowing through the exciting coil 18, the eddy current flowing through the fixing film 10 is varied to control the heat generation power.

Further, referring to FIG. 11, when AC power is received from a power input terminal 301, the AC power enters a rectifier circuit 304 via a contact of an overcurrent breaker 302 for protecting overcurrent and a relay 303. With relay 30
The excitation winding No. 3 is configured to detect the temperature of the fixing film of the fixing device, and to excite through a contact of a thermo switch 50 which shuts off when the temperature of the fixing film exceeds a predetermined temperature and abnormally rises.

If a trouble occurs and the temperature of the fixing device rises abnormally, the relay 303 is shut off and the power supply of the excitation circuit is turned off to ensure the safety of the fixing device from thermal runaway.

In the rectifier circuit 304, a DC ripple wave is generated from an AC power supply by a rectifier bridge circuit (not shown).
Voltage resonance switching circuit 307 via LC filter
Power supply. Voltage resonance switching circuit 30
The operation at 7 will be described later with reference to FIG.

Current transformer (current detection transformer) 3
08, the gate control transformers 305 and 306 are configured to secure double insulation between the live voltage circuit and the secondary voltage circuit by transformer insulation processing. The fixing temperature is detected by a first temperature detecting means (thermistor) 26, and a control signal given an optimal control coefficient which differs depending on the paper passing state of the fixing device, the paper quality, and the fixing temperature is supplied to the driver circuit 314. The result of comparison with the target temperature by the resonance control is output as an ON width control signal to perform gate control of the semiconductor switching element.

In the voltage resonance converter, the excess or deficiency of the target temperature is controlled by the switching-on width. The configuration and operation will be described in detail with reference to FIGS.

FIG. 12 is a circuit diagram of a voltage resonance type converter. Switching element 201 (first switching means), main switching element 202 (second switching means), exciting coil 18 (magnetic field generating means), first resonance capacitor 204 (first power storage means), second resonance Capacitor 205 (second power storage means), regenerative diode 20
6 (first rectifier) and a regenerative diode 207 (second rectifier).

The connection state of each part will be described. The first resonance capacitor 204 is connected in series to the switching element 201 connected to the power supply, and the switching element 218 connected to the power supply is connected to the switching element 201. A second resonance capacitor 205 is connected in series, and one end of each of the first and second resonance capacitors is connected to the switching element 202. The first resonance capacitor 204 is connected in series to the main switching element 202. I have. The first resonance capacitor 204, between the connection point of the second resonance capacitor 205 and the main switching element 202 and the power supply,
An excitation coil 203 for magnetic induction heating is connected.
Further, regenerative diodes (rectifying elements) 206, 217, and 207 are connected in parallel to the switching elements 201, 218 and the main switching element 202, respectively.

FIG. 13 is an explanatory diagram showing operation waveforms in the circuit configuration of FIG. 208 is the gate voltage waveform of the switching element 201, 209 is the gate voltage waveform of the main switching element 202, 210 is the current waveform of the main switching element 202, and 211 is the main switching element 20
2, a current waveform 212 of the first resonance capacitor 204, a current waveform 213 of the second resonance capacitor 205, a current waveform 214 of the switching element 201,
Reference numeral 15 denotes a current waveform of the regenerative diode 206, and 216 denotes an exciting current waveform of the exciting coil 203.

Next, the operation of this circuit will be described in detail.
By switching on the main switching element 202,
An induced current waveform 210 flows from the power supply to the exciting coil 203.

At the same time as the switching off (point A), the exciting coil 203 applies the flyback voltage 2 in the direction for maintaining the current.
Generates 11.

In the method of the present embodiment, since a difference occurs between the residual charges of the first resonance capacitor 204 and the second resonance capacitor 205 (the effect of the residual charges of the first resonance capacitor 204 described later), the main switching element Immediately after turning off 202, an arc determined by a resonance period ω = √ (L × C) determined by the second resonance capacitor 205 and the exciting coil 203 is drawn, and a voltage resonance phenomenon occurs via the second regenerative diode 217.

Here, it is assumed that the capacity of the second resonance capacitor 205 is set to about 1/10 of that of the first resonance capacitor 204. Therefore, the voltage immediately after turning off generates a flyback voltage in a high cycle (period A to B).

The oscillation of the flyback voltage turns on the first regenerative diode 206 at the time (point B) when the voltage rises to the initial charge voltage of the first resonance capacitor 204, and the first resonance capacitor 204 and the second Resonant capacitor 2
At the combined capacity of 05, the voltage is switched to a gentle sine wave and the voltage rises. At this time, the current waveform of the first resonance capacitor 204 is 212, and the current waveform of the regenerative diode 206 is 215.
The current waveform of the second resonance capacitor 205 is shown in FIG.

The voltage rises with time and reaches the maximum value (point C) when ω / 4 has elapsed.

On the other hand, in the current waveform 212, a cosine wave corresponding to a differential waveform of the voltage waveform flows, and as a result, at the maximum point (point C) of the voltage, the current has a zero crossing minimum value.

After the zero cross point, the regenerative diode 206
Is turned off, the gate of the switching element 201 is turned on to regenerate current (C to D periods). The current waveform of the switching element 201 at this time is shown by 214.

When the switching element 201 is turned off (point D), the first resonance capacitor 204 is disconnected.
Resonance of the second capacitor 205 having a small capacitance occurs, and a high-cycle arc (D to E periods) is drawn.

This behavior is the most noticeable operation of the mode in the first embodiment. During periods D to E, the second resonance capacitor 205 is connected to the first resonance capacitor 2 at point D.
All of the discharge current flowing in 04 is loaded.

When this state is verified as a value contributing to the vibration of the circuit, damping = √ (L / C) change, as a result of reducing C, the damping factor increases in proportion to the decrease of C, and a short-period strong vibration is obtained. Is obtained.

This strong oscillating voltage is the most important element of the voltage resonance, and generates a zero cross of the flyback voltage waveform due to the voltage oscillation, that is, the point E of the voltage waveform 211.

This point E is low in both current and voltage, and it is possible to minimize the switching loss when switching the switching element.

The switching operation of the switching element 201 which has performed the switching of the regenerative current is relatively low in the vicinity of the power supply voltage, and the switching operation is performed at a low current value (point D) due to damping by the exciting load. Therefore, the switching element 201 and the main switching element 202 can perform extremely low-loss switching.

Further, in this configuration, even when the inverter is started, the switching element 201 connected to the first resonance capacitor 204 can be started from the off state, and the transient load generated when the resonance power supply is started can be extremely reduced. .

Further, in the above-described operation, the state where the main switching element 202 is switching relatively high power is described. Therefore, the on-time is long and the flyback power is sufficiently accumulated in the exciting coil 203. Therefore, a high-period amplitude in the period from D to E sufficiently generates a zero-cross state, and a sufficient margin is provided for the ON timing of the main switching element 202.

The rotation state of the fixing film is determined from the temperature detection state of the fixing film. If the rotation of the fixing film is abnormal, the power of the exciting coil for generating a magnetic field is shut off. To prevent damage to the fixing film.

It is also possible to protect the fixing film by judging the absolute value of the temperature. However, regarding the temperature setting, the difference between the values of the first and second temperature detecting means 26 and 41 is determined. You should set a large value.

As described above, in the present embodiment, in order to realize the on-demand fixing in which the fixing film (metal film) having the electromagnetic induction heat is heated by the electromagnetic induction heating method, the fixing device is naturally heated. The fixing film was protected by judging abnormalities based on the transient temperature change based on the speed of the thermal response in which the constant was kept low.

<Second Embodiment> In the first embodiment, the temperature of the heating section H of the fixing film 10 is detected by the second temperature detecting means 41, and the rotation state of the fixing film 10 is determined to determine the heating power. However, a new function can be added by arranging the second temperature detecting means 41 at a non-sheet passing portion.

As shown in FIG. 17, the first temperature detecting means 26, which is a temperature controlling detecting means, is disposed at a portion closest to the fixing nip temperature, and the second temperature detecting means for detecting the heating portion is provided. Reference numeral 41 denotes a region H where the magnetic flux is coupled to the fixing film 10 and is disposed in the small-size paper non-sheet passing portion. With this arrangement, when small-size paper is continuously passed as the fixing paper, the central part of the fixing device, which is the paper passing part, loses the heating temperature, while the end part has little heat release and gradually rises. Heat up (heat up the non-paper passing area).

In order to cope with such a situation, for example, a method of lowering the throughput of the printer to maintain the temperature uniformity is often used.

Therefore, based on the result of controlling the temperature of the fixing nip N based on the detection value of the second temperature detecting means 41 disposed at the end of the heating section, the value of the temperature control result of the fixing nip N becomes the target value. And, when the value of the detection value of the second temperature detection means 41 provided in the end heating section exceeds a specified value,
By reducing the throughput, it is possible to monitor the heating of the end portion and to monitor the rotation state of the fixing film 10.

<Other Embodiments> 1) The fixing film 10 with heat generated by electromagnetic induction may have a form in which the elastic layer 2 is omitted in the case of fixing by heating such as a monochrome or one-pass multi-color image. it can.
The electromagnetic induction heating layer 1 may be formed by mixing a metal filler in a resin. It can also be a single-layer member of the electromagnetic induction heating layer.

2) The pressing member 30 is not limited to the roller body, but may be another type of member such as a rotating belt type.

In order to supply thermal energy to the recording material also from the pressing member 30 side, a heating means such as electromagnetic induction heating is also provided on the pressing member 30 side to heat and control the temperature to a predetermined temperature. It can also be configured.

The rotation of the fixing film 10 is not limited to the pressure roller driving system of the embodiment.

3) The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but may be an image heating device for heating a recording material carrying an image to improve the surface properties such as gloss, It can be widely used as a means and a device for heating a material to be heated, such as a heating device, a device for heating and drying a material to be heated, a heating laminating device, and the like.

[0170]

As described above, according to the present invention, in an electromagnetic induction heating type heating device and an image forming apparatus having the heating device as an image heating device, the electromagnetic induction heating member is sufficiently rotated. When there is no or when the electromagnetic induction heating member is damaged and the sliding rotation does not occur, the temperature stress of the electromagnetic induction heating member is reduced,
A longer life can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic cross-sectional view of a fixing device.

FIG. 3 is a front view of the same main part.

FIG. 4 is a cross-sectional front view of the same main part.

FIG. 5 is a diagram showing a relationship between a magnetic field generating means and an excitation circuit.

FIG. 6 is a diagram showing a relationship between a magnetic field generating means and a heating value Q;

FIG. 7 shows a safety circuit.

FIG. 8 is a schematic diagram of a layer structure of a fixing film of electromagnetic induction heat generation (part 1).

FIG. 9 is a graph showing a relationship between a heating layer depth and an electromagnetic wave intensity.

FIG. 10 is a schematic diagram of a layer structure of an electromagnetically induced heating fixing film (part 2).

FIG. 11 is a block circuit diagram of a control system.

FIG. 12 is a circuit diagram of a voltage resonance type converter.

13 is an explanatory diagram showing operation waveforms in the circuit configuration of FIG.

FIG. 14 is a graph showing the detected temperature characteristics of the first and second temperature detecting means (part 1).

FIG. 15 is a graph showing the detected temperature characteristics of the first and second temperature detecting means (part 2);

FIG. 16 is a graph showing the detected temperature characteristics of the first and second temperature detecting means (part 3);

FIG. 17 is a configuration explanatory view of a fixing device according to a second embodiment.

FIG. 18 is a diagram illustrating the configuration of a conventional fixing device.

[Explanation of symbols]

1. Heat generation layer, 2. Elastic layer, 3. Release layer, 4. Thermal insulation layer, 10. Fixing film, 16 Film guide, 17 Magnetic core, 18 Excitation coil, 19・ ・
Excitation coil holding member, 23a, 23b ... Flange member for regulating / holding end of fixing film, 26 ... First temperature detecting means (thermistor), 27 ... Temperature detecting element for safety, 30 ... Pressing member (Pressurizing roller), 41 .. Second temperature detecting means (Thermistor), 50 .. High frequency power supply

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takashi Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H033 AA23 AA42 BA25 BA32 BA37 BB29 BB30 BE06 CA07 CA34 CA44 CA45 3K059 AB19 AC33 AD13 AD25 BD01 CD05

Claims (6)

[Claims] 1. A magnetic field generating means, a member which generates electromagnetic induction by the action of a magnetic field of the magnetic field generating means, and a pressing member which forms a nip portion of a member to be heated by mutual pressure contact with the electromagnetic induction heating member. A heating device for heating the member to be heated by the heat generated by the electromagnetic induction heating member, a first temperature detection unit for detecting a temperature of a nip portion of the electromagnetic induction heating member, and the magnetic field generation unit. A heating device, comprising: a second temperature detecting means for measuring the temperature of the electromagnetic induction heating member that generates heat by coupling the generated magnetic field. 2. The apparatus according to claim 1, wherein the magnetic field generating means has a magnetic body forming a magnetic path with the exciting coil, and the second temperature detecting means is arranged on the magnetic path formed by the magnetic body. Heating equipment. 3. An exciting current applied to an exciting coil of the magnetic field generating means is controlled based on a temperature detected by the first temperature detecting means, and a temperature detected by the first temperature detecting means and a temperature detected by the second temperature detecting means are controlled. 3. The electric power supplied to the exciting coil is controlled based on a difference from a temperature.
A heating device according to claim 1. 4. The system according to claim 1, wherein the current supplied to the exciting coil of the magnetic field generating means is cut off when the temperature detected by the second temperature detecting means exceeds at least a predetermined value.
The heating device according to any one of claims 1 to 3. 5. The heating device according to claim 1, wherein the member to be heated is a recording material carrying an image. 6. An image forming apparatus having an image forming means for forming and carrying an image on a recording material and an image heating means for heating an image on the recording material, wherein the image heating means is provided. An image forming apparatus, which is the heating device according to any one of the above.