JP2002124369A - Induction heating device, and image processing device provided with the induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost induction heating device, that makes an optimum action to the plural induction coils for the fluctuation of the heating object (load), eliminates generation of abnormal noise from the coils and mutual interference between the induction coils, and performs stable operation. SOLUTION: FETs 51, 52 are respectively gate controlled by the driving circuits (1), (2), that are controlled by the frequency control circuit 7f and connect and disconnect the Vin input to each induction heating inverter. The temperature of the heating member 1 is fed back by the detecting sensors 121, 122 and the supply power to the inverter is controlled to attain object temperature. For this control, a delay circuit 8 of gate-on-pulse of the FET 52 is installed, and by adjusting the gate-on time by a method of delaying to the pulse of the FET 51 working synchronously, the supply power is controlled. An example of control operation by the size of the heating object is also shown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating apparatus provided with a plurality of induction coils to which a high-frequency current is supplied by an inverter. An inverter is constituted for each of a plurality of induction coils, and power supply to the inverters is individually performed. Controllable,
The present invention relates to an induction heating device which can control heat generation corresponding to a heating target in a simple and efficient manner and which can be used also in a heating and fixing section of a toner in an electrophotographic process.

[0002]

2. Description of the Related Art Conventionally, in an image processing apparatus such as a copying machine, a printer, and a facsimile, an image is formed by an electrophotographic system. In this method, in order to fix the developed toner image on an image forming material such as a recording sheet or paper,
A fixing device is provided. The main part of this fixing device is composed of a fixing roller that heats the sheet to which the unfixed toner is attached, and a pressure roller that presses the sheet between the fixing roller and pinches and conveys the sheet. Such a fixing device conventionally includes a halogen lamp or the like as a heater inside the fixing roller, heats the fixing roller with the lamp, and raises the fixing roller to a predetermined target temperature suitable for fixing required by the toner. Was something. However, such a heating method using a halogen lamp takes a long time to heat the fixing roller to a required temperature, and also causes a large loss of the heater itself, so that environmental problems such as global warming are present. There is a concern that the system will be closed up and adverse effects on the environment. To solve this problem, a fixing device with high efficiency and a short rise time is required.

Under such circumstances, it has been studied to use an induction heating device for heating during fixing. An induction heating device generates high frequency current through an induction coil disposed near a heating member, generates electromagnetic waves, and causes induction (eddy) current due to the electromagnetic waves to flow through a conductive layer of the heating member, thereby heating with Joule heat accompanying the induction current. Thus, heating to a predetermined temperature can be performed by controlling the high-frequency current. 2. Description of the Related Art A fixing device using an induction heating method has attracted attention because it has a characteristic that a fixing roller can be instantaneously heated by an eddy current caused by an electromagnetic wave, and the time required for heating can be dramatically shortened. In other words, the preheating operation required by the conventional halogen lamp method, that is, the operation of continuously supplying power to raise the temperature of the fixing unit to a predetermined temperature quickly at the time of re-use even when the apparatus is in standby without using the apparatus, results in a result. It is considered as one of the methods that can contribute to environmental problems because it can reduce wasteful electric power and has good heating efficiency. Copiers using fixing by induction heating usually detect the temperature of the fixing roller with a thermistor, control an inverter for induction heating according to the detected voltage, and supply a high-frequency current generated by the inverter to the induction coil. Then, the fixing roller is operated to reach the target temperature. Therefore, when the target temperature changes or the fixing temperature changes, the operation of the inverter is controlled so as to change the power supplied to the induction coil.

[0004]

However, in the case of the induction heating type fixing device, although the rise time can be shortened as compared with the conventional halogen heater type, it is difficult to use a single induction coil. When the width of the paper as the medium to be fixed is different, there is a problem that it is quite difficult to optimally control the fixing roller temperature to be constant over the entire heating section. Therefore, as a heating control method of the fixing device when the paper widths are different, for example, a plurality of main and sub induction coils are provided on the fixing roller, and drive signals for driving these coils are output in synchronization. A method of performing thinning-out control without driving a plurality of induction coils at the same time is being studied. In this method, the balance of the temperature can be controlled by the thinning rate, and it is possible to prevent mutual interference between a plurality of induction coils. However, according to such thinning control, when the thinning rate of the slave coil is increased, there is a problem that the drive frequency is in the audible range and abnormal noise is generated.
In addition, since a general control IC cannot be used for the thinning control circuit, it is necessary to develop a control IC for thinning, and there is a problem that the cost increases.
In addition, there is another problem that it is difficult to optimize the temperature control only by the thinning control. The present invention has been made in view of the above-mentioned problems of the related art in an induction heating device including a plurality of induction coils to which a high-frequency current is supplied by an inverter. Allows multiple induction coils to perform optimal operation with respect to fluctuations, does not generate abnormal noise of induction coils, which has been a problem in the past, and does not cause mutual interference between induction coils, resulting in stable An object of the present invention is to provide an inexpensive induction heating device capable of performing an operation. In addition, the above-described induction heating apparatus is used as an image heating and fixing processing unit in an electrophotographic system, and an image processing apparatus capable of performing stable fixing by optimal temperature control according to various medium (paper) sizes. (For example, a copying machine, a facsimile, a printer, or a composite machine thereof).

[0005]

According to the present invention, a plurality of induction coils for inductively heating a heating member, switching means for turning on / off an input to each induction coil, and turning on / off of the switching means are provided. In an induction heating apparatus having an induction heating inverter comprising control means for controlling, the control means synchronizes a switching operation for turning on / off an input to each induction coil, and obtains an on / off signal by pulse width modulation. An induction heating device characterized by the above.

According to a second aspect of the present invention, there is provided the induction heating apparatus according to the first aspect, further comprising a temperature detecting unit for the heating member heated by the induction coil, and feeding back the detected temperature via the control unit. It is characterized by the following.

According to a third aspect of the present invention, there is provided an image processing apparatus in which the induction heating device according to the first or second aspect is used as an electrophotographic image heating and fixing means.

According to a fourth aspect of the present invention, in the image processing apparatus according to the third aspect, the ratio of the ON signal pulse width of each induction coil is determined according to the power required according to the size of the recording medium to be fixed. It is characterized by having been determined.

A fifth aspect of the present invention comprises a plurality of induction coils for inductively heating a heating member, switching means for turning on / off an input to each induction coil, and control means for controlling on / off of the switching means. In an induction heating apparatus having an induction heating inverter, the control means synchronizes a switching operation for turning on / off an input to each induction coil, obtains an on / off signal by frequency modulation, and turns on / off each induction coil. An induction heating apparatus characterized in that a delay time is provided between signals.

According to a sixth aspect of the present invention, there is provided the induction heating device according to the fifth aspect, further comprising a temperature detecting means for the heating member heated by the induction coil, wherein the detected temperature is fed back via the control means. It is characterized by the following.

According to a seventh aspect of the present invention, there is provided an image processing apparatus wherein the induction heating device according to the fifth or sixth aspect is used as an electrophotographic image heating and fixing means.

According to an eighth aspect of the present invention, in the image processing apparatus of the seventh aspect, the delay time provided between the ON signals of the respective induction coils is determined according to the power required according to the size of the recording medium to be subjected to the fixing process. An image processing apparatus characterized in that the image processing apparatus is defined as follows.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the following embodiments shown in the accompanying drawings. Prior to the description of the present embodiment, an induction heating device (preceding example) on which the present embodiment is based will be described below. This example shows an apparatus applied to an image heating and fixing means in an electrophotographic image processing apparatus (for example, a copying machine, a facsimile, a printer, or a multifunction peripheral thereof). FIG. 6 shows a schematic configuration of the induction heating device of the prior art. FIG. 7 shows an example of an operation waveform of a switching element that supplies power to a coil (induction coil). Reference numeral 1 in FIG. 6 denotes a fixing roller to be heated. Reference numeral 2 denotes a coil (induction coil) for generating an electromagnetic wave, and reference numeral 4 denotes a capacitor. An input Vin supplied from a DC power supply (not shown) to the coil 2 and the capacitor 4 connected in parallel is connected to a switching element 5.
Interrupted by These are the basic elements that make up the induction heating inverter. The switching element 5 performs a switching operation by a drive circuit 60 and a drive control circuit 70 that controls the drive circuit 60. The temperature of the heated fixing roller 1 is detected by a temperature detector (for example, a thermistor or the like) 12, and the detected temperature value is a drive control circuit 7 of the switching element 5.
By feeding back to 0, the switching element 5 is controlled so as to keep the roller temperature constant, and the input power to the inverter is controlled.

In this prior example, the switching element 5
Is provided with a capacitor 4 which resonates with the inductance of the coil 2 in order to reduce the switching loss of
The drain-source voltage V of the operation waveform (current, voltage waveform, in this example, the drain current Id and the drain-source voltage Vds of the FET) of the switching element 5 shown in FIG.
As shown by ds, a resonance waveform is obtained. Further, as shown in the current waveform of the drawing, when the voltage of the resonance waveform becomes zero, the drain current Id enters the conduction period of the switching element 5, the current starts to flow, and continues to rise until the end of the conduction period. In this case, since the waveform of the resonance voltage Vds of the switching element 5 is determined by the resonance conditions (the inductance of the coil 2 and the resonance capacitor 4), when controlling the temperature of the fixing roller 1 to be constant, the time of the resonance voltage Vds The width cannot be changed, and PWM (pulse width modulation) control cannot be performed. Therefore, in the conventional example, the drive control of the switching element 5 is performed by a frequency change that changes the time width at the time of on while fixing the width of the off time.

By the way, there are various sizes of the medium (paper) to be fixed in the fixing device. The most common case is that the sheet is A4 lengthwise and sideways as shown, but in the case of induction heating, it is difficult to control one coil to keep the temperature constant for both sheet widths. Met. In other words, when the coil length is set to A4 length, the temperature at both ends of the A4 width paper becomes low when the A4 width paper medium is passed, and the fixing of the optimum quality for the A4 width paper passing. There is a problem that can not be done. On the other hand, if the coil length is A
If the width is adjusted to 4 widths, on the contrary, there is a large problem that the temperature rises too much when the paper is passed in the A4 lengthwise direction, and the temperature of the paper and the temperature of the fixing device itself rise abnormally. In the prior art proposed as a means for solving this problem, one fixing roller is provided with two primary and secondary coils,
It is stated that it is possible to cope by controlling each coil according to the difference in paper width. In this case, since only one fixing roller acts as a load on each coil, it is necessary to control a plurality of coils to operate synchronously. In addition, it is necessary to drive the sub-coil so that the sub-coil supplies the optimum power to the main coil in accordance with the change of the paper medium width. Trying to do. However, in the case of such a control, the power amount of the slave coil is small, and when the interval of the thinning is large, the frequency of the slave coil is equivalently decreased, and
If this frequency drop falls into the audible range, an abnormal sound will be generated. Further, an unstable operation causing mutual interference between the frequency for driving the main coil and the frequency for driving the sub coil is caused, and these interference frequencies themselves are in the audible range. Further, when the interval of the thinning of the slave coil is increased due to the thinning control, the control time becomes long, and accurate temperature control cannot be performed.

The present invention is intended to overcome the problems of the above-mentioned prior art and the prior art. In the prior art, the frequency of an inverter for driving a plurality of induction coils is controlled to control the thinning of various paper sizes. In place of the method that is intended to cope with the above, by adopting a method in which an inverter for driving a plurality of induction coils is operated synchronously by PWM control so that the drive frequency of each coil is always constant. It constitutes an induction heating device. Hereinafter, an embodiment of the induction heating apparatus according to the present invention will be described. This example is based on an electrophotographic image processing apparatus (for example,
1 shows an apparatus applied to an image heating and fixing means in a copier, a facsimile, a printer, or a multifunction machine thereof. FIG. 1 is a diagram illustrating a configuration of an induction heating device according to the present embodiment. FIG. 2 shows the driving circuit (1) shown in FIG.
FIG. 3 is a diagram showing an example of a circuit applicable to the driving circuit (2). FIG. 3 shows an operation waveform for driving an induction coil generated by the circuit of FIG. The circuits (1) and (B) show one example of the waveform of the drive circuit (2).

In FIG. 1, reference numeral 1 denotes a fixing roller to be induction-heated. Reference numerals 2 ₁ and 2 ₂ denote a plurality of induction coils (a main coil 2 ₁ and a slave coil 2 ₂₎ for generating electromagnetic waves acting on the fixing roller 1. ). Each induction coil ₂ 1, _{2 2} are respectively the drive circuit (1) _{6 1,} driven by a drive circuit (2) _{6 2.} Driving circuit (1) 6 _{1 (or} the driving circuit (2) 6 _2), as shown in FIG. 2, the capacitor 4a, 4b (provided that the capacitor 4a connected in series in this example, 4b capacitor 4
b moiety intermittently to the circuit is controlled by the PWM control circuit 7) is connected in parallel with the induction coil 2 _{1 (or} 2 _2),
Parallel connected induction coil _{2 1} (or _{2 2)} the capacitor 4a, the input Vin from a DC power source E is supplied to 4b
Are interrupted by the switching element 5. These are the basic elements that make up the induction heating inverter. The switching operation of the switching element 5 is controlled by the PWM control circuit 7. For example, thermistors 12 ₁ and 12 ₂ are provided as temperature detecting sensors at appropriate positions of the fixing roller 1 near the positions of the induction coils 2 ₁ and 2 ₂ , and the detected voltage is PW.
Is fed back to the M control circuit 7 performs drive pulse width control to supply power in accordance with the variation of the load to a target temperature set for the fixing roller 1 for each induction coil 2 _1, 2 _2.

[0018] In one example of operation in this embodiment, the operation waveforms related to the switching element 5 for driving the respective induction coil 2 _1, 2 ₂ and the waveform as is schematically illustrated by an operation waveform of FIG. 3 Become. In FIG. 3 illustrates an example of the waveform of (A) the main induction coil 2 _first driving circuit (1), (B) sub induction coil 2 _second driving circuit (2). In FIG. 3, V
g1, Vg2 are respectively a waveform applied to the gate of the switching element 5 from the PWM control circuit 7 to drive each induction coil 2 _1, 2 _2, likewise Id1, Id2, respectively,
It also shows the current flowing through the gate-controlled switching element 5. As shown in the figure, the main induction coil _{2 1} drive (A), the sub induction coil _{2 second} drive (B),
In each operation, gate control is performed at a constant frequency. That is, the gate is turned on at the same time, the gate on-time is controlled the power required according to the respective thermistors 12 _1, 12 ₂ of the detected value as a time for supplying the inverter, in the illustrated example the main induction coil 2 ₁ side of the switching element The current Id1 of No. 5 flows for a longer time. In the present invention, as shown in this embodiment, the sub induction coil 2 _second current Id2 is the main induction coil 2 ₁ current Id1, because less than the ON time width is but not equal to 0 less, this Therefore, the driving frequency does not fall in the audible range.

The following embodiment is a modification of the above embodiment.
From the PWM control circuit 7 to the gate of the switching element 5
Controlling the on-time width obtained by controlling the temperature of the fixing roller 1
However, in the following embodiment, the PWM control circuit
ON time width by path 7 is controlled by recording medium (paper) width
1 shows an induction heating device to be controlled. Depending on paper width
To control the on-time width of multiple induction coils respectively
In the present embodiment, each of the induction coils is
The width of the recording medium needs the ratio of the ON time width to drive
Depending on the method of operating so that the ratio according to the power
Do. That is, in the operation waveform of FIG. 3, the waveforms of Vg1 and Vg2
Of ON time width to power ratio required for paper width
According to the ratio (Vg2 ON time as the paper width increases
(Increase the width ratio). Paper width
The on-time width ratio is determined according to the
Need to get data. Therefore, the paper width size
And a means for detecting the size according to the detected size signal.
It can be implemented by a method that determines the loose width ratio
it can. If the paper is specified in advance,
Set the optimum pulse width ratio for the specified paper.
It can be easily implemented. Also, depending on such paper width
In the case of the method of controlling the ratio of the ON time width by
Unlike the embodiment shown, the PWM control circuit 7 includes a driving circuit
(1) 6₁, Drive circuit (2) 6₂Multiple control circuits for
Drive control with a single control circuit
become. The ON time width depends on the width of the recording medium (paper).
Control by paper width.
The temperature of the fixing roller may exceed the control range
In such a case,
Degree detection sensor 12₁, 12₂Feedback control
It is preferable to compensate the operation so that the temperature becomes constant. Also,
In the case of, the temperature detection is performed by the temperature detection sensor 12.₁Only as warm
Degree detection sensor 12 ₂Can be eliminated.

Next, instead of the method of controlling the frequency of the inverter for driving a plurality of induction coils shown in the above-mentioned prior art, so as to be able to cope with various paper sizes by thinning control, a plurality of paper sizes are replaced. An induction heating device that employs a method that operates the inverter for driving the induction coil in synchronization with frequency control, but can respond to load fluctuations by delaying the operation timing of the switching element from the synchronization signal. Will be described. The induction heating apparatus according to the present embodiment described below is also applied to an image heating and fixing unit in an electrophotographic image processing apparatus (for example, a copying machine, a facsimile, a printer, or a multifunction peripheral thereof). The device is exemplified. FIG.
FIG. 1 is a diagram showing a configuration of an induction heating device of the present embodiment. Further, FIG. 5, the operation waveform (current, voltage waveforms of the switching elements for supplying electric power to the coil (induction coil) of FIG. 4, in this example, F was used as the switching element 5 _1, 5 ₂
This shows one example of the drain currents Id1, Id2 of the ET and the drain-source voltage Vds). 1 in FIG.
Is a fixing roller that is induction-heated, and 2 ₁ and 2 ₂ are
A plurality of induction coils for generating an electromagnetic wave that acts on the fixing roller 1 (the main coil _{2 1,} sub coil _{2 2),} 4 1, _{4 2} are capacitors. DC power is two sets of parallel connection (not shown) and the main induction coil _{2 1} capacitor _{4 1,} intermittent input Vin supplied to the sub induction coil _{2 2} and capacitors _{4 2} by the switching element ₅ 1, _{5 2} I do. These are the basic elements that make up two sets of induction heating inverters.

[0021] Each switching element ₅ 1, _{5 2,} driving circuit controlled by the frequency control circuit 7f (1)
6 1 _performs the switching operation is gated controlled via the driving circuit (2) 6 _2. For example, thermistors 12 ₁ and 12 ₂ are provided as temperature detecting sensors at appropriate positions on the fixing roller 1 near the positions of the induction coils 2 ₁ and 2 ₂ , and the detected voltage is fed back to the frequency control circuit 7 f, so that the fixing roller 1 Control is performed so as to supply electric power according to the load fluctuation to each induction heating inverter in order to reach the set target temperature. At this time, operation of the switching element 5 _1, 5 ₂ is performed as in the conventional example shown in FIG.
Further, as a method for controlling the power supplied to the induction heating inverter, a circuit 8 for delaying the pulse for ON operation of the switching element 5 ₂ provided, is turned on the switching element 5 ₁ induction heating inverters operate synchronously A method of delaying the pulse by the delay time td is adopted. In this case, the switching element _{5 2,} as shown in FIG. 5, the operating current Id2 having a delay time td with respect to the operating current Id1 of the switching element _{5 1} flows. The delay time td is by determining in accordance with a signal detected by the thermistor 12 _2, control such that the temperature in the width direction of the fixing roller 1 becomes constant is performed.

In the above embodiment, the frequency control circuit 7f
Delay time td operated by
Therefore, the control is performed.
The delay time td by the wave number control circuit 7f is stored in a recording medium (for
Induction heating device controlled by width)
You. The delay time td of a plurality of induction coils depends on the paper width.
As a control method, in this embodiment, the switch
Element 5₂Turn on the recording media width required power
A method of operating with a delay time td corresponding to the above is adopted. Immediately
In the operation waveform of FIG. 5, the operating currents Id1 and Id2
When the delay time td is set according to the required power ratio of the paper width
(The delay of the operating current Id2 increases as the paper width increases.
Adjustment). Slow depending on paper width
Since the delay time td is determined, the width of the paper medium is
Delay time, if known in advance, such as
Since td may be constant, the driving circuit (2) 6₂Control times
Road is drive circuit (1) 6₁When the control circuit of the
Simplified with a gate circuit with a set interval
It becomes possible to do. Note that the delay time td is
When controlling by body (paper) width, paper
Even if the width is controlled, the temperature of the fixing roller is controlled
It is possible that the range may be exceeded.
In such a case, the temperature detection sensor 12₁, 12₂by
Compensate for constant temperature by feedback control operation
Good to be. In this case, the temperature detection is performed using a temperature detection sensor.
12₁Only as temperature detection sensor 12 ₂No need for
Can be.

[0023]

(1) Effects corresponding to the first aspect of the invention Since the plurality of induction coils are driven by synchronized pulse width modulation control, how the load of the heating target changes is controlled. However, the frequency of each coil is always constant, so that it is possible to provide an induction heating device that operates stably without the problem of abnormal sound or interference as described in the prior art. Further, unlike the thinning control in the related art, since the frequency is constant even when the load on the slave coil is reduced, the response speed to the load fluctuation is fast and the operation can be performed with high accuracy. Furthermore, since the thinning-out control method is not a general method, there is no general-purpose control IC or the like, and it is necessary to configure all of the circuits by the thinning-out control with discrete circuits, and the design is difficult and expensive. However, according to the present invention, it is possible to provide a low-cost apparatus that can be configured using a conventional general pulse width modulation control IC. (2) Effects corresponding to the second aspect of the present invention In addition to the effects of the above (1), by performing feedback control based on the temperature detected by the temperature detecting means of the heating member, heating is performed regardless of the load fluctuation of the heating member. The temperature of the member can be controlled, and an induction heating device having accurate temperature control performance can be provided. (3) Effects corresponding to the third aspect of the invention An image processing apparatus (for example, a copying machine, Facsimile, printer, or a multifunction peripheral thereof)
By realizing the effect of (2), accurate temperature control in the fixing process can be performed, and the performance of the image processing apparatus can be improved. (4) Effects corresponding to the invention of claim 4 In addition to the effect of (3), the ratio of the ON signal pulse width of each induction coil can be determined based on the size of the recording medium, and the ratio is constant. , The pulse width modulation control circuit can be simplified.

(5) Effects corresponding to the fifth aspect of the present invention. A switching operation for turning on / off an input to each induction coil is performed in synchronization, and an on / off signal is obtained by frequency modulation. By providing a delay time between the ON signals, each induction coil does not operate at a low drive frequency no matter how the load to be heated changes, as described in the prior art. It is possible to provide an induction heating device that operates stably without causing abnormal noise or interference. Further, the response speed to the load fluctuation is faster than in the thinning control in the prior art, and the operation can be performed with high accuracy. Furthermore, there is no difficulty in circuit design in the thinning control method,
Further, the present invention can be implemented by a simple circuit without requiring a plurality of switching elements as in the case of the PWM control in the first aspect. (6) Effects corresponding to the sixth aspect of the invention In addition to the effect of the above (5), by performing feedback control based on the temperature detected by the temperature detecting means of the heating member, heating is performed irrespective of the load fluctuation of the heating member. The temperature of the member can be controlled, and an induction heating device having accurate temperature control performance can be provided. (7) Effects corresponding to the invention of claim 7 An image processing apparatus (for example, a copying machine, Facsimile, printer, or a multifunction machine thereof), the above (5),
By realizing the effect (6), accurate temperature control in the fixing process becomes possible, and the performance of the image processing apparatus can be improved. (8) Effects corresponding to the invention of claim 8 In addition to the effect of the above (1), the delay time provided between the ON signals of the induction coil is determined based on the size of the recording medium to be subjected to the fixing process, and Since the operation can be performed with the ratio kept constant, the frequency modulation control circuit can be simplified.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of an embodiment of an induction heating device having a plurality of induction coils according to the present invention.

FIG. 2 shows a driving circuit (1) and a driving circuit (2) shown in FIG.
An example of a circuit applicable to the present invention is shown below.

3A and 3B show operation waveforms for driving an induction coil, wherein FIG. 3A shows an example of a waveform of a drive circuit (1), and FIG. 3B shows an example of a waveform of a drive circuit (2).

FIG. 4 shows a schematic configuration of another embodiment of the induction heating device having a plurality of induction coils according to the present invention.

5 shows an example of an operation waveform of a switching element that supplies power to the induction coil of FIG.

FIG. 6 shows a schematic configuration of an example of a prior art induction heating device having a plurality of induction coils.

7 shows an example of an operation waveform of a switching element for supplying power to the induction coil of FIG.

[Explanation of symbols]

1 ... heating member (fixing roller), _{2 1,} 2 2 _... induction _coil, 4, 4 _1, 4 2, 4a, 4b ... capacitors,
5, 5 ₁ , 5 ₂ ... switching element, 6 ₁ , 6 ₂ , 60
... driving circuit, 7 ... PWM (pulse width modulation) control circuit, 7f ... frequency modulation control circuit, 70 ... drive control circuit, 8 ... delay circuit, 12, 12 _1, 12
_2. Temperature detecting means (thermistor, etc.).

Continued on the front page (72) Inventor Jiro Ouchi 3-1 F-term (reference) 2H033 AA21 BA25 BA30 BE06 CA07 CA27 CA45 CA46 3K059 AA08 AB28 AC20 AC23 AC33 AC35 AD02 AD04 AD35 AD37 CD03 CD22 CD23 CD65 CD73 CD75 CD77

Claims (8)

[Claims] 1. An induction heating inverter comprising a plurality of induction coils for inductively heating a heating member, switching means for turning on / off an input to each induction coil, and control means for controlling on / off of the switching means. In the induction heating apparatus, the control means synchronizes a switching operation for turning on / off an input to each induction coil, and obtains an on / off signal by pulse width modulation. . 2. The induction heating apparatus according to claim 1, further comprising temperature detecting means for detecting a temperature of the heating member heated by the induction coil, wherein the detected temperature is fed back via the control means. Heating equipment. 3. An image processing apparatus, wherein the induction heating apparatus according to claim 1 is used as an electrophotographic image heating / fixing unit. 4. The image processing apparatus according to claim 3, wherein the ratio of the on-signal pulse width of each induction coil is determined according to the power required according to the size of the recording medium to be subjected to the fixing process. An image processing apparatus characterized by the above-mentioned. 5. An induction heating inverter comprising a plurality of induction coils for inductively heating a heating member, switching means for turning on / off an input to each induction coil, and control means for controlling on / off of the switching means. In the induction heating apparatus, the control means synchronizes a switching operation for turning on / off an input to each induction coil, obtains an on / off signal by frequency modulation, and delays an on / off signal of each induction coil. An induction heating device characterized in that a heating device is provided. 6. The induction heating apparatus according to claim 5, further comprising temperature detection means for the heating member heated by the induction coil, wherein the detected temperature is fed back via the control means. Heating equipment. 7. An image processing apparatus, wherein the induction heating apparatus according to claim 5 is used as an image heating and fixing means in an electrophotographic system. 8. The image processing apparatus according to claim 7, wherein the delay time provided between the ON signals of the respective induction coils is:
An image processing apparatus characterized in that the image processing apparatus is determined according to power required according to the size of a recording medium to be subjected to a fixing process.