JP2002208469A - Heating device, and image forming device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device enabled to supply a constant electric power to a magnetic flux generating means independent of fluctuation of the voltage of power source, and enabled to apply a stable heat treatment by restraining the device from fluctuating at warm-up time, and to provide an image forming device equipped with this heating device. SOLUTION: A power control part 812 detects the voltage generated at a magnetic flux generating means 15, and the power, supplied from a commercial AC power source 801 to an exciting coil 18 of the magnetic flux generating means 15, is controlled corresponding with the detected voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for heating a recording material carrying an image and an image forming apparatus provided with the heating device.

[0002]

2. Description of the Related Art An example of a heating device provided in an image forming apparatus such as a copying machine and a printer is an electrophotographic process.
A recording material (transfer material sheet, electrofax) that carries an image (toner image) formed in accordance with image information by an appropriate image forming process such as an electrostatic recording process or a magnetic recording process in a transfer system or a direct system Sheet,
There has been known a fixing device in which an image is fixed on the recording material by subjecting an electrostatic recording sheet, an OHP sheet, a printing sheet, a format sheet, and the like) to a heat treatment to form a permanent fixed image.

In such a fixing device, a heat roller system is generally widely used. In recent years, from the viewpoint of quick start and energy saving, an apparatus employing a belt heating method has been put into practical use, and an apparatus employing an electromagnetic induction heating method has been proposed.

Here, a fixing device employing an induction heating method will be described.

Japanese Utility Model Laid-Open Publication No. 51-109739 discloses a fixing device employing an induction heating system in which a current is induced in a fixing roller as a heating member by magnetic flux to generate heat by Joule heat. This allows the fixing roller to directly generate heat by utilizing the generation of induced current,
It achieves a more efficient fixing process than a heat roller type fixing device using a halogen lamp as a heat source.

However, conventionally, since the energy of the alternating magnetic flux generated by the exciting coil as the magnetic flux generating means is used to raise the temperature of the entire fixing roller, heat dissipation is large, and the density of the fixing energy with respect to the input energy is low and the efficiency is low. There was a disadvantage.

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

The fixing device shown in FIG.
15, a fixing film 210 as a heating member, and a pressure roller 230 as a pressure member.

[0010] The fixing film 210 is a cylindrical electromagnetic induction heat generating rotator having an electromagnetic induction heat generation layer (a conductor layer, a magnetic layer, and a resistor layer). Also, the fixing film 210
Is a gutter-shaped film guide member 216 having a substantially semicircular cross section.
Is loosely fitted around the outer periphery of the device and is rotatable.

The magnetic flux generating means 215 includes an exciting coil 218
And an E-shaped excitation core (core material) 217, and are disposed inside the film guide member 216.

The pressure roller 230 is used for the fixing film 210.
Is pressed to the lower surface of the film guide member 216 with a predetermined pressing force, and has elasticity so as to form a fixing nip portion N as a nip region having a predetermined width. Magnetic flux generating means 2
The 15 magnetic cores 217 are disposed so as to correspond to the fixing nip N.

The pressure roller 230 is driven to rotate in a counterclockwise direction indicated by an arrow in FIG. Due to the frictional force between the pressing roller 230 and the outer surface of the fixing film 210 due to the rotational driving of the pressing roller 230, a rotational force acts on the fixing film 210, and the inner surface of the fixing film 210 is fixed at the fixing nip portion N. Member 21
14 while rotating in close contact with the lower surface of the film guide member 216 at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 230 in the clockwise direction of the arrow in FIG. Drive system).

The film guide member 216 presses the fixing nip portion N and excites the exciting coil 218 of the magnetic flux generating means 215.
Further, it has a role of supporting the magnetic core 217, supporting the fixing film 210, and stabilizing the conveyance of the fixing film 210 during rotation. Also, the film guide member 216
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 218 generates an alternating magnetic flux by an alternating current supplied from an exciting circuit (not shown). The alternating magnetic flux is intensively distributed to the fixing nip N by the E-shaped magnetic core 217 corresponding to the position of the fixing nip N, and the alternating magnetic flux is generated by the electromagnetic induction heat of the fixing film 210 at the fixing nip N. An eddy current is generated in the layer. This eddy current generates Joule heat in the potential induction heating layer due to the specific resistance of the electromagnetic induction heating layer.

The electromagnetically induced heat of the fixing film 210 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 detected by a temperature detecting means 2.
The temperature control system including 26 controls the current supply to the exciting coil 18 by a control means (not shown) so that the temperature is controlled so as to maintain a predetermined temperature.

Thus, the pressure roller 230 is driven to rotate, and the cylindrical fixing film 210 rotates around the film guide member 216 in accordance with the rotation, and power is supplied from the excitation circuit to the excitation coil 218 as described above. The fixing film 210 is heated by electromagnetic induction, so that the fixing nip N
In a state where the temperature rises to a predetermined temperature and is controlled,
The recording material P conveyed from the image forming means (not shown) and carrying the unfixed toner image t is positioned between the fixing film 210 and the pressure roller 230 in the fixing nip N, with the image surface facing upward, ie, fixing. The fixing nip N is conveyed together with the fixing film 210 while the image is brought into close contact with the outer surface of the fixing film 210 at the fixing nip N. In the process of nipping and conveying the recording material P together with the fixing film 210 in the fixing nip N, the unfixed toner image t on the recording material P is heated and fixed by heating by the electromagnetic induction heat of the fixing film 210. .
After passing through the fixing nip N, the recording material P is separated from the outer surface of the rotating fixing film 210 and is discharged and conveyed.

[0019]

However, in the fixing device employing the above-described conventional induction heating method, when the power supply voltage fluctuates, the voltage applied to the exciting coil is reduced to the power supply voltage. As shown in FIG. 15, when the power supply voltage is high, the heat generation amount of the fixing film by the excitation coil is large, and when the power supply voltage is low, the heat generation amount of the fixing film by the excitation coil becomes small. I will. For this reason, there is a large difference in the warm-up time between the case where the power supply voltage is high and the case where the power supply voltage is low at the start of heating of the fixing device. For example, when power is supplied from indoor electrical equipment wiring, fluctuations in power supply voltage cause fluctuations in the power supplied to the excitation coil, which is a magnetic flux generating unit, and cause the fixing device (that is, the image forming device) to warm up. The situation that time fluctuated occurred.

Further, in such a fixing device, the printing quality reaches a predetermined fixing temperature before the printing paper reaches the fixing device, thereby realizing stable printing quality.
Due to the influence of the decrease in the power supply voltage, the sheet reaches the fixing device before the temperature reaches the fixing temperature, and a situation occurs in which the quality of printing is reduced.

Therefore, the present invention provides a heating apparatus which can supply a constant power to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, suppress the fluctuation of the warm-up time of the apparatus, and perform a stable heating process. An object of the present invention is to provide an image forming apparatus including the heating device.

[0022]

According to the present application, the above object is achieved by a magnetic flux generating means for generating a magnetic flux by receiving electric power from a power supply, and a hollow cylindrical shape rotatable around an axis. A heating member that generates an induced current by a magnetic flux to generate heat, and a pressure member that presses against the heating member to form a nip region and rotates, and performs a heating process while passing a recording material bearing an image through the nip region. A heating device that includes a voltage detection unit that detects a voltage generated by a magnetic flux generation unit, and a control unit that controls power supply from a power supply to the magnetic flux generation unit in accordance with the voltage detected by the voltage detection unit. This is achieved by the first invention.

Further, according to the present application, the above object is achieved in the first invention in that the control means controls the magnetic flux from the power supply so that the voltage detected by the voltage detection means at the start of heating of the heating device increases under a constant condition. The present invention is also achieved by the second invention in which control of power supply to the generating means is set.

Further, according to the present application, the above object is achieved according to the first invention or the second invention, wherein the control means decreases the voltage detected by the voltage detection means when heating of the heating device is stopped under a certain condition. As described above, the present invention is also achieved by the third invention in which the control of the power supply from the power supply to the magnetic flux generating means is set.

According to the present application, the above object is also achieved by the fourth invention in any one of the first invention to the third invention, wherein the voltage detecting means is constituted by a linear element. You.

Further, according to the present application, the above object is achieved by the fifth invention in any one of the first to third inventions, wherein the voltage detecting means is constituted by a non-linear element. You.

According to the present application, the above object is attained by the sixth invention in which, in any one of the first to third inventions, the voltage detecting means is constituted by a transformer including an insulation type. Is also achieved.

Further, according to the present application, the above object is also achieved by the seventh invention in which the control means is a CPU in any of the first to sixth inventions.

According to the present application, the above object is achieved by any one of the first to seventh inventions, wherein the control means comprises:
The present invention is also achieved by an eighth aspect of the invention constituted by hardware.

Further, according to the present application, the above object is achieved in any one of the first to eighth inventions, wherein the control means detects that power supply from the power supply to the magnetic flux generation means is detected by the voltage detection means. The present invention is also achieved by a ninth invention in which a program set in advance corresponding to the voltage is provided.

According to the present application, the above object is provided in any one of the first to ninth inventions, comprising a zero voltage detecting means for detecting a zero voltage of the power supply, and the control means comprises the zero voltage detecting means. The present invention is also achieved by the tenth invention in which the power supply from the power supply to the magnetic flux generating means is set to be controlled in accordance with the elapsed time after the zero voltage is detected by the detecting means.

Further, according to the present application, an object of the present invention is an image forming apparatus which records an image formed by a series of image forming processes on a recording material. The present invention is also achieved by the eleventh invention including the heating device of (1).

[0033]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described.

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to the present embodiment. The image forming apparatus of this embodiment shown in FIG. 1 is an electrophotographic color printer.

The image forming apparatus according to the present embodiment includes a photosensitive drum (image carrier) 101 formed of an organic photosensitive member or an amorphous silicon photosensitive member.

In this image forming apparatus, first, the photosensitive drum 101 is driven to rotate at a predetermined process speed (peripheral speed) in a counterclockwise direction indicated by an arrow in FIG.

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 its rotation.

Next, the laser beam 1 output from the laser optical box (laser scanner) 110 is applied to the charged surface.
03 undergoes scanning exposure processing of the target image information.
The laser optical box 110 outputs a laser beam 103 modulated (on / off) corresponding to a time-series electric digital pixel signal of target image information from an image signal generating device (not shown) such as an image reading device. , Rotating photosensitive drum 10
The surface of the photosensitive drum 101 is scanned and exposed to form an electrostatic latent image on the photosensitive drum 101 corresponding to the target image information. The laser beam 103 output from the laser optical box 110 is
As a result, the photosensitive drum 101 is deflected to the exposure position.

In the case of full-color image formation, 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. Is developed as a yellow toner image by the operation of the yellow developing device 104Y.

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 close portion) between the photosensitive drum 101 and the intermediate transfer drum 105.

After the transfer of the toner image to the surface of the intermediate transfer drum 105, the surface of the rotating photosensitive drum 101 is cleaned by the cleaner 107 by removing the adhered residue such as untransferred toner.

As described above, the process cycle of charging, scanning exposure, development, primary transfer, and cleaning is performed by the second color separation component image of the target full-color image (for example, the magenta component image, the magenta developing device 104M operates), Third color separation component image (for example, cyan component image, cyan developing device 104C
Operates), a fourth color separation component image (for example, a black component image,
(The black developing unit 104BK is activated) for each color separation component image, and a yellow toner image, a magenta toner image, a cyan toner image,
A total of four color toner images of the black toner image are sequentially superimposed and transferred, and a color toner image corresponding to a target full-color image is 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 is in contact with or close to the photosensitive drum 101 and has substantially the same circumference as the photosensitive drum 101. 1 is rotated in the clockwise direction of the arrow shown in FIG. 1, a bias potential is applied to the metal drum of the intermediate transfer drum 105, and a toner image on the photosensitive drum 101 side is transferred by a potential difference from the photosensitive drum 101. Transfer to the 105 side.

The color toner image synthesized and formed on the surface of the rotating intermediate transfer drum 105 is subjected to a secondary transfer at a secondary transfer section T2 which is a contact nip between the rotating intermediate transfer drum 105 and the transfer roller 106. The image is transferred onto the surface of the recording material P sent to the transfer unit T2 at a predetermined timing from a sheet feeding unit (not shown). The transfer roller 106 supplies a charge of the opposite polarity to the toner from the back surface of the recording material P, and sequentially collectively transfers the combined color toner images 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 separated from the surface of the intermediate transfer drum 105 and introduced into the fixing device 100, which is a heating device. The paper is discharged to a paper discharge tray (not shown) outside the apparatus as a formed product. The fixing device 100 will be described later in detail.

After the transfer of the color toner image onto the recording material P, the rotating intermediate transfer drum 105 is
As a result, the residual toner such as transfer residual toner and paper dust is removed, and the toner is cleaned. The cleaner 108 is always kept in a non-contact state with the intermediate transfer drum 105, and is kept in a contact state with the intermediate transfer drum 105 in the process of performing the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. Is done.

The transfer roller 106 is always 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 member Drum 105
Is kept in contact with the recording material P via the recording material P.

The image forming apparatus according to this embodiment can 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 image print mode, the recording material P on which the first-side image has been printed out of the fixing device 100 is
The sheet is turned upside down via a recirculation transport mechanism (not shown), sent to the secondary transfer portion T2 again to receive the toner image transfer on the two surfaces, and is again introduced into the fixing device 100 to be transferred to the fixing device 100. By receiving the fixing process, 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
Without being turned upside down via a recirculation transport mechanism (not shown), the toner image is sent again to the secondary transfer portion T2 to receive the second transfer of the toner image on the surface on which the first image has been printed. The multi-image print is output by being subjected to the second toner image fixing process after being introduced.

Here, the fixing device 100 will be described in detail.

The fixing device 100 according to the present embodiment is a device that employs an electromagnetic induction heating method.

FIG. 2 is a cross-sectional side view of a main part of the fixing device 100 according to the present embodiment, FIG. 3 is a front view of the main part, and FIG. 4 is a longitudinal front view of the main part. FIG.

The fixing device 100 of this embodiment includes a magnetic flux generating means 15, a fixing film 10 as a heating member, and a pressure roller 30 as a pressure member.

The magnetic flux generating means 15 includes a magnetic core 17a, 1
7b, 17c and an exciting coil 18.

The magnetic cores 17a, 17b, and 17c are members having high magnetic permeability, and are preferably made of a material used for a transformer core such as ferrite or permalloy, and more preferably, ferrite having a small loss even at 100 kHz or more. .

As shown in FIG. 5, the exciting coil 18 has
The excitation circuit 27 is connected to the power supply units 18a and 18b. The excitation circuit 27 has a frequency of 20 kHz to 500 kHz.
Up to high frequencies can be generated by a switching power supply.

The exciting coil 18 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the exciting circuit 27.

The belt guide members 16a and 16b each having a substantially semicircular arc cross section have a substantially cylindrical body with their opening sides facing each other, and a fixing film 10, which is a cylindrical electromagnetic induction heating belt, is formed on the outside. Fitted loosely.

The belt guide members 16a and 16b are
Magnetic cores 17a, 17 provided in magnetic flux generating means 15
b, 17c and the exciting coil 18 are held inside.

Further, as shown in FIG. 4, the belt guide members 16a and 16b are provided with a good heat conductive member 40 extending in the direction perpendicular to the sheet of FIG. 4 on the side of the fixing nip portion N, which is a nip area, facing the pressure roller 30. And is disposed inside the fixing film 10.

In this embodiment, the good heat conductive member 4
Aluminum is used for 0. The good thermal conductive member 40 of the present embodiment has a thermal conductivity k = 240 [W · m ⁻¹ · K].
^-1 ] and the thickness is 1 [mm].

The good thermal conductive member 40 includes an exciting coil 18 and magnetic cores 17a, 17b, 1 serving as magnetic flux generating means.
It is arranged outside this magnetic field so as not to be affected by the magnetic field generated from 7c.

More specifically, the good heat conductive member 40 is disposed at a position separated by the magnetic core 17 c from the exciting coil 18, and is positioned outside the magnetic path formed by the exciting coil 18. 40 is not affected.

A horizontally long pressing rigid stay 22 is disposed in contact with the inner flat surface of the belt guide member 16b.

An exciting coil holding member 19 which is an insulating member for insulating the magnetic cores 17a, 17b, 17c and the exciting coil 18 from the rigid stay 22 for pressurizing.
Are arranged.

The flange members 23a and 23b are fitted to the left and right ends of the assembly of the belt guide members 16a and 16b, and are rotatably mounted while fixing the positions of the left and right ends. The belt guide member 16 of the fixing film 10
a, 16b serves to regulate the movement in the longitudinal direction.

The pressure roller 30 serving as a pressure member is made of a heat-resistant elastic material such as silicone rubber, fluoro rubber, or fluoro resin which is formed by concentrically forming a roller around the core 30a and the core 3a. The metal layer 30b is disposed so that both ends of the core 30a are rotatably supported by bearings between sheet metal (not shown) on the apparatus chassis side.

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 rigid stay 22. ing. This allows
The lower surface of the belt guide member 16a and the upper surface of the pressure roller 30 are pressed with the fixing film 10 interposed therebetween to form a fixing nip portion N having a predetermined width.

The pressure roller 30 is driven to rotate in the counterclockwise direction indicated by the arrow by the driving means M. A rotational force acts on the fixing film 10 by the 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, and the inner surface of the fixing film 10 has good thermal conductivity at the fixing nip portion N. The belt guide member 16 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 sliding in close contact with the lower surface of the member 40.
The outer periphery of a and 16b is rotated.

In this case, in order to reduce the mutual sliding friction force between the lower surface of the good heat conductive member 40 in the fixing nip N and the inner surface of the fixing film 10, the lower surface of the good heat conductive member 40 in the fixing nip N is reduced. A lubricant such as heat-resistant grease may be interposed between the inner surface of the fixing film 10 and the lower surface of the good heat conductive member 40. This is because when the surface sliding property is not good in material such as when aluminum is used as the good heat conductive 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 No. 10 from deteriorating.

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

As shown in FIG. 5, a convex rib portion 16e is formed on the peripheral surface of the belt guide member 16a at a predetermined interval along the length thereof.
The contact sliding resistance between the peripheral surface of the fixing film 10 and the inner surface of the fixing film 10 is reduced, so that the rotational load of the fixing film 10 is reduced.

Such a convex rib portion 16e can be similarly formed on the belt guide member 16b.

FIG. 6 schematically shows how alternating magnetic flux is generated by the magnetic flux generating means of this embodiment. In FIG. 6, a 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 is applied to the magnetic cores 17a and 17b.
Between the magnetic core 17a and the magnetic core 17c, an eddy current is generated in the heating layer 1 which is the electromagnetic induction heating layer of the fixing film 10. This eddy current generates Joule heat (eddy current loss) in the heat generating layer 1 due to the specific resistance of the heat generating layer 1. The heat value Q here is determined by the density of the magnetic flux passing through the heat generating 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 the angle θ with the center of the magnetic core 17 a being 0, and the horizontal axis indicates the heat generation amount Q in the heat generating layer 1 of the fixing film 10. Is shown. 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 area where a heat value required for fixing can be obtained.

The temperature of the fixing nip portion N is controlled by a temperature control system including a temperature sensor 26 as temperature detecting means shown in FIG.
The temperature is controlled so that a predetermined temperature is maintained by controlling the current supply to the exciting coil 18. In this temperature control system, the temperature sensor 26 such as a thermistor
Is detected, and in the present embodiment, the temperature sensor 2
The temperature of the fixing nip N is controlled based on the temperature information of the fixing film 10 measured in Step 6.

As the fixing film 10 rotates, the electric power is supplied from the excitation circuit 27 to the excitation coil 18 to generate the potential induced heat 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, to which the toner image t has been transferred in the secondary transfer portion T2, is positioned between the fixing film 10 in the fixing nip portion N and the pressure roller 30, with the image surface facing upward, that is, fixing. Film 1
In the fixing nip N, the image surface is brought into close contact with the outer surface of the fixing film 10 so that the fixing film 1
The fixing nip portion N is conveyed while being pinched together with 0. In the process of nipping and transporting the recording material P together with the fixing film 10 through the fixing nip N, the unfixed toner image t on the recording material P is heated and fixed by heating by the electromagnetic induction heat of the fixing film 10. After passing through the fixing nip N, the recording material P is separated from the outer surface of the rotating fixing film 10 and is discharged and conveyed. Thus, the heat-fixed toner image on the recording material P is cooled after passing through the fixing nip portion N to become a permanent fixed image.

In the present embodiment, as shown in FIG. 2, a thermo-detecting element, which is a temperature detecting element, is provided at the position of the fixing film 10 facing the heat generating area H shown in FIG. A switch 50 is provided.

FIG. 7 is a circuit diagram of the safety circuit used in this embodiment.

Thermoswitch 50 as Temperature Sensing Element
Is connected in series with the +24 VDC power supply and the relay switch 51. When the thermo switch 50 is turned off, the power supply to the relay switch 51 is cut off, and the relay switch 51 is turned off.
Operates, and the power supply to the excitation coil 18 is cut off when the power supply to the excitation circuit 27 is cut off. In the present embodiment, the OFF operation temperature of the thermoswitch 50 is set to 220 ° C.

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. The distance between the thermoswitch 50 and the fixing film 10 was approximately 2 mm. This allows
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 runs away due to a device failure, unlike the configuration in which heat is generated in the fixing nip portion N as shown in FIG. Is stopped, the power supply to the excitation coil 18 is continued, and the fixing film 10 continues to generate heat, so that the paper is not directly heated because no heat is generated in the fixing nip portion N where the paper is sandwiched. In addition, the heat generation area H where the heat generation amount is large.
Since the thermo switch 50 is disposed in the power supply, the thermo switch 50 senses 220 ° C., and when the thermo switch 50 is turned off, the power supply to the exciting coil 18 is cut off by the relay switch 51.

According to the present embodiment, the ignition temperature of the paper is about 4
Since the temperature is around 00 ° C., heat generation of the fixing film can be stopped without igniting the paper.

Incidentally, a temperature fuse can be used as the temperature detecting element in addition to the thermoswitch.

Further, in this embodiment, since the toner containing the low softening substance is used in the toner of the toner image t, the fixing device does not have the oil application mechanism for preventing the offset, but the low softening substance is contained. When toner not used is used, an oil applicator side may be provided. Furthermore,
When a toner containing a low softening substance is used, oil application or cooling separation may be performed.

FIG. 8 shows an excitation coil 1 according to this embodiment.
8 is a diagram illustrating a typical example of a configuration of a circuit around a drive device of No. 8; FIG.

In the present embodiment, as shown in FIG. 8, the excitation coil 18 receives the electric power from the commercial AC power supply 801 as a power supply and generates a magnetic flux. In the present embodiment, the output of the commercial AC power supply 801 is 85 Vrms to 140 Vrms.
In the case of Vrms, the output is 184 Vrms to 264 Vrms for Europe.
It may be. However, since the description of the operation of the present embodiment is the same for both, the output is 85 Vrms.
A description will be given of the case where it is 140 Vrms.

In this embodiment, the voltage from the commercial AC power supply 801 is full-wave rectified by the diode bridge 802, and after the noise component is removed by the noise component removing filter constituted by the inductance 804 and the capacitor 805, The power is supplied to the exciting coil 18. The constants are set so that the filter composed of the inductance 804 and the capacitor 805 passes the commercial frequency and cuts only the higher harmonic components.

The exciting coil 18 includes a resonance capacitor 80.
6 and a resonance circuit. Switching element 8
08 is a semiconductor element for driving the exciting coil 18;
A switching element represented by an IBGT, a transistor, an FET, or the like is used. The collector voltage of the switching element 808 is divided by a resistor 810 and a resistor 811 and connected to a power control unit 812 as a voltage detection unit and a control unit.

FIG. 9 shows voltage and current waveforms during the operation of the circuit of FIG.

In FIG. 9, reference numeral 901 denotes a collector voltage VQ1 of the switching element 808, 902 denotes a current flowing through the switching element 808, and 903 denotes a gate (base) voltage for turning on / off the switching element 808. .

The operation of the power control unit 812 shown in FIG.
By varying the ON width of the gate (base) voltage. In normal operation of the actual image forming apparatus, temperature information of the fixing film 10 heated by the magnetic flux generated by the exciting coil 18 is monitored by a temperature detecting element represented by a thermistor, and a switching element is provided so that the detected temperature becomes constant. The ON width of the gate (base) voltage 808 is varied.

Conventionally, when the image forming apparatus is cold,
When power is applied to the exciting coil 18 to raise the temperature of the fixing film 10 to a predetermined fixing temperature, the maximum period of time during which the gate (base) is turned on is set within a range that does not cause element destruction. Is controlled by Therefore, the time required to reach the fixing time depends on the power supply voltage, and when the power supply voltage is low, an extremely long time is required.

In the fixing device employing the induction heating method, the inductance of the device is stable.
It has been experimentally confirmed that there is little variation among devices, and that when the on-time of the switching element 808 is constant, the flyback voltage applied to the switching element 808 depends on the commercial AC power supply voltage. Have been.

Therefore, the fixing device 100 according to the present invention
When power is supplied to the exciting coil 18, the switching element 8
The fixing device 100 is operated with the on-time of the constant 08 being constant, and the flyback voltage applied to the switching element 808 is observed by a voltage detecting means (not shown), and the power control unit 812 is excited by the observed voltage value. The power supplied to the coil 18 is controlled so that a constant power is supplied to the exciting coil 18 regardless of the voltage from the commercial AC power supply 801.

FIG. 10 shows a change in the flyback voltage applied to switching element 808 with respect to the voltage from commercial AC power supply 801.

In FIG. 10, reference numeral 1001 denotes a case where the voltage from the commercial AC power supply 801 is 140 V.
02 indicates a flyback voltage applied to the switching element 808 when the voltage from the commercial AC power supply 801 is 120 V, and 1003 indicates a flyback voltage applied to the switching element 808 when the voltage from the commercial AC power supply 801 is 100 V. Shows voltage.

[0100] As shown in FIG.
The flyback voltage applied to the switching element 808 increases as the voltage from the switch increases. As described above, when the ON time of the switching element 808 is fixed, the flyback voltage applied to the switching element 808 is equal to the commercial A
It depends on the voltage from the C power supply 801.

When heating of the fixing device 100 is started, the power control unit 812 outputs a gate (base) voltage of the switching element 808 so as to supply power to the exciting coil 18 with a constant ON width. The flyback voltage at this time is
The voltage is divided by the resistors 810 and 811 and
When the voltage is input to the CPU 12, the CPU (not shown) of the power control unit 812 detects the analog voltage at the A / D terminal and captures the voltage as a digital value corresponding to the analog voltage inside the CPU.

The CPU of power control section 812 compares this digital value with a value described in advance in the program of the CPU to determine the level of the voltage from commercial AC power supply 801. , The default power to the fixing device 10
The on-time of the switching element 808 for switching to 0 is varied. By repeating such an operation, it is possible to realize a fixing system in which the power supplied to the fixing device 100 does not depend on the voltage from the commercial AC power supply 801.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 11 is a diagram showing a typical example of a circuit configuration around a drive device of the exciting coil 18 in the present embodiment.

In the fixing device according to this embodiment, FIG.
As shown in (1), the power control value for the flyback voltage of the exciting coil 18 is stored in a nonvolatile memory 1113 such as an EEPROM or a flash memory connected to the power control unit 1112 which is a voltage detection unit and a control unit. The commercial AC power supply 110 serving as a power supply depends on the relationship between the content of the nonvolatile memory 1113 and the detected voltage of the flyback voltage.
It is possible to input a constant power independent of the voltage from 1.

At the start of heating of the fixing device, the power control unit 1112 outputs a gate (base) voltage of the switching element 1108 so as to supply power to the exciting coil 18 with a constant ON width. The flyback voltage of the exciting coil 18 at this time is divided by the resistors 1110 and 1111 and input to the power control unit 1112, and the CPU (not shown) serving as a voltage detection unit of the power control unit 1112 outputs The analog voltage is detected at the A / D terminal, and is taken in as a digital value corresponding to the analog voltage in the CPU.

The CPU of power control section 1112 compares the digital value with a value described in advance in nonvolatile memory 1113 to determine the voltage level from commercial AC power supply 1101. The on-time of the switching element 1108 for supplying predetermined power to the fixing device is varied. Further, in the present embodiment, the values (flyback voltage detection voltage value, control ON width data) used at this time are stored in a specific address of the nonvolatile memory 1113, and at the next start-up, the value of this address is used as a reference. It is characterized in that control is performed to speed up control responsiveness.

(Third Embodiment) Next, a third embodiment of the present invention will be described. In addition, about the structure similar to 1st Embodiment or 2nd Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

In the present embodiment, a description will be given of power control based on detection of a zero crossing of the AC of the power supply voltage and on-time control of the switching element from the time of the zero crossing detection.

FIG. 12 is a diagram showing a typical example of a circuit configuration around a drive device of the exciting coil 18 in the present embodiment.

In this embodiment, the commercial AC power source 2
Diode bridge (DB1)
After full-wave rectification at 1202, the resistance (R20) 12
The AC voltage is divided by a resistor 15 and a resistor (R21) 1214 and connected to a timer unit 1213 as zero voltage detecting means.

The timer section 1213 detects zero volts of the AC voltage divided by the resistance and operates the internal timer.

At the start of heating of the fixing device of this embodiment,
By gradually increasing the on-time up to a half-wave of the AC waveform of the commercial AC power supply 1201 from the zero crossing point in the timer section 1213 as an upper limit, the peak value of the voltage applied to the exciting coil 18 also gradually increases. .

FIG. 13 is a diagram showing a change in the waveform of each part in this state.

In FIG. 13, reference numeral 1301 denotes a voltage waveform that has been full-wave rectified by the diode bridge (DB1) 1202, and reference numeral 1302 denotes an on-time Tzone generated by the timer unit 1213 with reference to zero voltage. , 1
Reference numeral 303 denotes a voltage waveform applied to the exciting coil 18.

As the ON time is sequentially increased by the timer section 1213, the voltage applied to the exciting coil 18 also increases. As the voltage applied to the exciting coil 18 increases sequentially, the flyback voltage generated in the switching element 1208 also increases gradually. The flyback voltage applied to the switching element 1208 is set to a resistance (R1).
The voltage is divided by a resistor 1210 and a resistor (R2) 1211 and input to a power control unit 1212 as a voltage detection unit and a control unit.

In the power control unit 1212, the timer unit 12
13 and switching element 1 divided by resistance
The flyback voltage applied to the commercial A
By estimating the voltage from the C power supply 1201, the setting for the amount of power to the fixing device to be a specified value is calculated, and the subsequent control is executed based on the calculation result.

The timer section 1213 increases the on-time under a certain condition so that the on-time is not set when the on-time exceeds a half cycle of the AC voltage so as to maintain the always-on state. After the ON time exceeds a half cycle, the fixing device is controlled by the power control value determined by the power control unit 1212.

As described above, the on-time from the zero-cross point of the AC power supply voltage is increased by a fixed amount, the flyback voltage of the switching element at that time is monitored, and the power control value is determined by determining the power control value. Independent power input is possible.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. The same components as those in the first to third embodiments are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, a description will be given of a low-power control method using power control based on on-time control of the switching element from the zero-cross time by detecting a zero cross of the AC of the power supply voltage.

In a fixing device using electromagnetic induction heating, on / off control (normal chopping control) of a switching element at a rate based on a time longer than a power supply frequency is used as a means for expanding a control range of input power. In the case where the heat capacity of the fixing device itself is reduced in order to shorten the warming-up time of the fixing device of the image forming apparatus, if the chopping control is performed, the temperature of the fixing device may have a temperature unevenness in synchronization with the cycle of the chopping control. I will.

Then, the temperature unevenness causes fixing unevenness, which causes deterioration of image quality of the image forming apparatus.

Therefore, in the present embodiment, a case where low power control is performed in addition to the method described in the third embodiment will be described. Note that the configuration of a heating drive control system of the heating device in this embodiment is the same as that of the third embodiment shown in FIG.

Since the relationship between the ON time in the timer section 1213 and the voltage applied to the exciting coil 18 is as shown in FIG. 13, when controlling the fixing device with low power, the power control section 1212 The time corresponding to the target power is set by the timer unit 1213 to perform low power control.

As described above, by controlling the on-time based on the zero cross point of the voltage from the commercial AC power supply 1201, it is possible to realize a fixing device with high power control linearity and a wide control range. Also, a commercial AC power supply 12
Since the operation of the switching element 1208 is always started at the zero cross point of the voltage from 01, the switching element 1208 does not need to perform high-voltage switching, so that the life of the element is not significantly shortened.

In the present embodiment, when control can be performed within the control range of the power control unit 1212, the timer unit 1213 keeps the ON state at all times and uses power smaller than the power control range of the power control unit 1212. When performing the control, the timer unit 1213 performs an operation to limit the ON time.

In the first to fourth embodiments, the description has been made by dividing the voltage detection by resistance. However, the voltage detection means is not limited to resistance division.
A non-linear element such as a semiconductor and a transformer may be used.

[0129]

As described above, according to the first aspect of the present invention, the voltage detecting means detects the voltage generated by the magnetic flux generating means, and the control means detects the voltage generated by the voltage detecting means. The power supply from the power supply to the magnetic flux generation means is controlled in accordance with the applied voltage, so that a constant power can be supplied to the magnetic flux generation means without depending on the voltage fluctuation of the power supply, and the warm-up time of the device can be reduced. Variations can be suppressed and stable heat treatment can be performed.

According to the second invention of the present application,
The voltage detecting means detects a voltage generated by the magnetic flux generating means, and the control means controls power supply from the power supply to the magnetic flux generating means in accordance with the voltage detected by the voltage detecting means. Since the power supply from the power supply to the magnetic flux generation means is controlled so that the voltage detected by the voltage detection means at the start of heating of the heating device increases under certain conditions, the power supply does not depend on the voltage fluctuation of the power supply. A constant electric power can be supplied to the magnetic flux generating means, fluctuations in the warm-up time of the apparatus can be suppressed, and stable heat treatment can be performed.

Further, according to the third invention of the present application, the voltage detecting means detects the voltage generated by the magnetic flux generating means, and the control means responds to the voltage detected by the voltage detecting means. Along with controlling the power supply from the power supply to the magnetic flux generating means, the control means controls the power supply from the power supply to the magnetic flux generating means so that the voltage detected by the voltage detecting means decreases when heating of the heating device is stopped. Since the control is performed, a constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, the fluctuation of the warm-up time of the apparatus can be suppressed, and a stable heating process can be performed.

According to the fourth invention of the present application,
Voltage detecting means constituted by a linear element detects a voltage generated by the magnetic flux generating means, and control means controls power supply from the power supply to the magnetic flux generating means in accordance with the voltage detected by the voltage detecting means. Since the control is performed, a constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, the fluctuation of the warm-up time of the apparatus can be suppressed, and a stable heating process can be performed.

Further, according to the fifth aspect of the present invention, the voltage detecting means constituted by the non-linear element detects the voltage generated by the magnetic flux generating means, and the control means detects the voltage by the voltage detecting means. The power supply from the power supply to the magnetic flux generating means is controlled according to the applied voltage, so that a constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, and the warm-up time of the device can be increased. And a stable heat treatment can be performed.

Further, according to the sixth invention of the present application,
Voltage detecting means configured with a transformer including an insulation type detects a voltage generated by the magnetic flux generating means, and control means responds to the voltage detected by the voltage detecting means from the power supply to the magnetic flux generating means. Since the power supply is controlled, a constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, the fluctuation of the warm-up time of the apparatus can be suppressed, and a stable heating process can be performed. .

Further, according to the seventh aspect of the present invention, the voltage detecting means detects the voltage generated by the magnetic flux generating means, and the control means which is a CPU controls the voltage detected by the voltage detecting means. Correspondingly, the power supply from the power supply to the magnetic flux generating means is controlled, so that a constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply,
Variations in the warm-up time of the apparatus can be suppressed, and stable heat treatment can be performed.

Further, according to the eighth invention of the present application,
The voltage detecting means detects the voltage generated by the magnetic flux generating means, and the control means constituted by hardware controls the power supply from the power supply to the magnetic flux generating means in accordance with the voltage detected by the voltage detecting means. Since the control is performed, a constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, the fluctuation of the warm-up time of the apparatus can be suppressed, and a stable heating process can be performed.

Further, according to the ninth aspect of the present invention, the voltage detecting means constituted by the linear element detects the voltage generated by the magnetic flux generating means, and the control means operates according to a preset program. Since the power supply from the power supply to the magnetic flux generating means is controlled in accordance with the voltage detected by the voltage detecting means, a constant power is supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply. As a result, fluctuations in the warm-up time of the apparatus can be suppressed, and stable heat treatment can be performed.

Further, according to the tenth aspect of the present invention,
Voltage detecting means constituted by a linear element detects a voltage generated by the magnetic flux generating means, and control means controls power supply from the power supply to the magnetic flux generating means in accordance with the voltage detected by the voltage detecting means. Control, the zero voltage detection means detects the zero voltage of the power supply, and the control means controls the power supply from the power supply to the magnetic flux generation means in accordance with the elapsed time since the zero voltage was detected by the zero voltage detection means. Since the supply is controlled, constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, fluctuations in the warm-up time of the apparatus can be suppressed, and stable heat treatment can be performed.

Further, according to the eleventh aspect of the present invention, the voltage detecting means detects the voltage generated by the magnetic flux generating means, and the control means responds to the voltage detected by the voltage detecting means. Control the power supply from the power supply to the magnetic flux generating means, so that a constant power can be supplied to the magnetic flux generating means without depending on the voltage fluctuation of the power supply, and the fluctuation of the warm-up time of the device is suppressed, and Heat treatment can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a schematic configuration of a heating device provided in the image forming apparatus of FIG.

FIG. 3 is a view of the heating device of FIG. 2 as viewed from a sheet discharging side.

FIG. 4 is a cross-sectional view of the heating device of FIG.

FIG. 5 is a diagram for explaining magnetic flux generating means provided in the heating device of FIG. 2;

FIG. 6 is a diagram for explaining the amount of heat generated by a heating member by a magnetic flux generator provided in the heating device of FIG. 2;

FIG. 7 is a diagram for explaining a safety circuit of the heating device according to the first embodiment of the present invention.

FIG. 8 is a block diagram illustrating a configuration of a heating drive control system of the heating device according to the first embodiment of the present invention.

FIG. 9 is a timing chart for explaining power supply from a power supply to a magnetic flux generation unit in the first embodiment.

FIG. 10 is a diagram illustrating a relationship between a voltage applied to a switching element and a power supply voltage.

FIG. 11 is a block diagram illustrating a configuration of a heating drive control system of a heating device according to a second embodiment of the present invention.

FIG. 12 is a block diagram illustrating a configuration of a heating drive control system of a heating device according to a third embodiment of the present invention.

FIG. 13 is a timing chart for explaining power supply from a power supply to a magnetic flux generating unit according to the third embodiment.

FIG. 14 is a schematic sectional view showing a schematic configuration of a conventional heating device.

FIG. 15 is a diagram showing a relationship between a warm-up time and a voltage of a power supply in the related art.

[Explanation of symbols]

 Reference Signs List 10 fixing film (heating member) 15 magnetic flux generating means 30 pressure roller (pressing member) 100 fixing device (heating device) 801 commercial AC power supply (power supply) 812 power control unit (voltage detection means, control means) 1101 commercial AC power supply (Power supply) 1112 Power control unit (voltage detection unit, control unit) 1201 Commercial AC power supply (power supply) 1212 Power control unit (voltage detection unit, control unit) 1213 Timer unit (zero voltage detection unit) N Fixing nip unit (nip area) ) P Recording material t Toner image (image)

Claims (11)

[Claims] A magnetic member for generating magnetic flux by receiving electric power from a power supply; a heating member having a hollow cylindrical shape rotatable around an axis, generating heat by generating an induced current by the magnetic flux generated by the magnetic flux generating means; A pressure member that forms a nip area by pressing against a member and rotates, and detects a voltage generated by a magnetic flux generating means in a heating device that performs a heating process while passing a recording material bearing an image through the nip area. A heating device, comprising: a voltage detecting means for controlling the power supply from the power supply to the magnetic flux generating means in accordance with the voltage detected by the voltage detecting means. 2. The control means is configured to control the power supply from the power supply to the magnetic flux generating means so that the voltage detected by the voltage detecting means at the start of heating of the heating device increases under certain conditions. The heating device according to claim 1. 3. The control means is configured to control the power supply from the power supply to the magnetic flux generating means so that the voltage detected by the voltage detecting means when heating of the heating device is stopped is reduced under certain conditions. The heating device according to claim 1. 4. The heating device according to claim 1, wherein the voltage detecting means is constituted by a linear element. 5. The heating device according to claim 1, wherein the voltage detecting means is constituted by a non-linear element. 6. The heating device according to claim 1, wherein the voltage detecting means is configured by a transformer including an insulation type. 7. The heating device according to claim 1, wherein the control means is a CPU. 8. The heating device according to claim 1, wherein the control means is constituted by hardware. 9. The control device according to claim 1, wherein the control unit has a program which is set in advance in accordance with the voltage detected by the voltage detection unit to supply power from the power supply to the magnetic flux generation unit. The heating device according to any one of claims 8 to 13. 10. A zero voltage detecting means for detecting a zero voltage of a power supply, wherein the control means sends a signal from the power supply to the magnetic flux generating means in response to an elapsed time after the zero voltage is detected by the zero voltage detecting means. The heating device according to claim 1, wherein the heating device is set to control power supply. 11. An image forming apparatus for recording an image formed by a series of image forming processes on a recording material,
An image forming apparatus comprising the heating device according to any one of claims 1 to 10.