WO2004105442A1

WO2004105442A1 - Induction heating roller device, fixing device using this and image forming device

Info

Publication number: WO2004105442A1
Application number: PCT/JP2004/007840
Authority: WO
Inventors: Hiroyuki Doi; Ichiro Yokozeki; Manabu Kika; Takayuki Ogasawara; Toshiya Suzuki; Takaaki Tanaka; Syouhei Maeda
Original assignee: Harison Toshiba Lighting Corp.
Priority date: 2003-05-22
Filing date: 2004-05-19
Publication date: 2004-12-02

Abstract

An induction heating roller device comprising a high-frequency power source device (HFS) provided with a main circuit unit (MC) for converting a low-frequency ac voltage into a high-frequency ac voltage to output the result and with a control unit (CC) for controlling the main circuit unit (MC) and being capable of outputting a high-frequency ac voltage PWM-controlled at a frequency sufficiently higher than that of a low-frequency ac voltage and sufficiently lower than that of a high-frequency ac voltage, an induction coil (IC) to which the high-frequency ac voltage of the high-frequency power source device (HFS) is applied, and a heating roller (HR) for allowing a secondary current to flow to effect heating by being magnetically coupled with the induction coil (IC).

Description

Heat roller device, fixing device and image forming device using the same

The present invention relates to an improved induction heating roller device, a fixing device including the same, and an image forming apparatus. Background art

Conventionally, a heat roller using a halogen bulb as a heat source has been used to thermally fix a toner image. However, there is a problem that the efficiency is low and a large power is required. Therefore, development is underway to solve this problem by introducing an induction heating method. Induction heating methods for this type of purpose include, for example, an eddy current loss method as described in JP-A-2000-215974, and There is a transformer system as described in Japanese Patent Publication No. 337787. The eddy current loss method has the same operating principle as that used in an IH jar or the like, and heats a heating roller by eddy current generated in a heating roller by an induction coil. The transformer system described in the above-mentioned document is composed of a cylindrical roller body or a heating roller composed of a conductive member, a cylindrical bobbin concentrically arranged in the roller body, and spirally wound around the outer periphery of the bobbin. And an induction coil for inducing an induced current in the roller body by energization to heat the roller body. Then, the cylindrical roller body becomes the secondary coil of the closed circuit, the induction coil becomes the primary coil, and a transformer coupling occurs between the two, and a secondary voltage is induced in the secondary coil of the cylindrical roller body. Is done. As a result, the secondary current flows in the closed circuit of the secondary coil, and the cylindrical roller body generates heat.

By the way, the transformer method has a higher steady state efficiency due to stronger magnetic coupling than the eddy current loss method, and can heat the entire heating roller. There is an advantage that the structure of the fixing device is simplified as compared with the system. In addition, by setting the operating frequency to a high frequency of 20 kHz or more, preferably 1 MHz or more, the Q of the induction coil can be increased and the power transfer efficiency can be increased. For this reason, the overall efficiency of heating is increased, and power can be saved. Another advantage is that the structure of the fixing device is simplified as compared with the eddy current loss method. Further, the heat capacity can be considerably reduced as compared with the eddy current loss type heating roller. Therefore, the transformer method is very suitable for speeding up the heat deposition.

SUMMARY OF THE INVENTION The inventors of the present invention have proposed a rotatable and supported hollow heating roller that is air-core transformer-coupled to an induction coil, and has a secondary circuit comprising a closed circuit having a secondary resistance value substantially equal to the secondary reactance. By forming the coil, the efficiency of power transmission from the induction coil to the heating roller is increased, and a transformer-coupled invention is obtained in which a remarkable effect of efficiently heating the heating roller can be obtained. The present invention is described in Japanese Patent Application Laid-Open No. 2002-222628. According to the present invention, it is possible to save power for induction heating of the heating roller, and it is easy to speed up the heat fixing. The transformer-type induction heating roller device is one of the most promising applications for utilizing the high-frequency power extracted from the high-frequency power supply.

Regardless of the heating method, any induction heating roller device has a common feature in that the high-frequency voltage generated by the high-frequency power supply device is applied to the induction coil and the induction coil is energized. . In order to apply an induction heating roller device to a fixing device such as a copying machine, improvement to a high-frequency power supply device is desired. That is, first, it is desirable that the high-frequency power supply be suitable for mass production, secondly, that it be inexpensive, lightweight, and thirdly, be capable of changing the amount of heat generated by the heating roller. It is.

On the other hand, according to the conventional technology, a resonance circuit is provided at the output end of a high-frequency power supply that generates a high-frequency AC voltage of a high frequency, for example, 100 kHz or more. It is known that high-frequency AC power can be efficiently extracted when it is provided. However, when trying to obtain high-frequency AC power of about 1 kW from a 100 V commercial AC power supply, the input impedance of the resonance circuit of the high-frequency power supply becomes very low. When the input impedance is so low, the impedance of the resonance circuit changes due to the existence of a slight parasitic inductance or the like. For this reason, there is a problem that it is not possible to obtain a high-frequency power supply device suitable for mass production with the above-described configuration based on the conventional technology.

Therefore, the input impedance of the high-frequency output terminal is increased by increasing the input voltage of the high-frequency power supply by interposing a step-up means such as a booster step-up transformer between the low-frequency AC power supply and the high-frequency power supply. It can be considered higher. However, the above-described configuration based on the conventional technology has a problem in that cost and weight are increased. Also, when the induction heating roller device uses the heat generated by the heating roller for fixing a toner image of a copying machine or the like, it is desirable that the amount of heat generated can be changed according to the fixing speed. To achieve this, it is necessary to change the high-frequency AC power transmitted to the heating roller. Therefore, high-frequency power can be easily changed by interposing a booster chopper at the input stage of the high-frequency converter and operating the booster chopper to adjust the DC input voltage. -However, the conventional method of boosting the DC power supply voltage by intervening boosting means such as a boosting chopper and a boosting transformer as required increases the cost and weight, and is inexpensive and moreover. However, there is a problem that a demand for a lightweight high-frequency power supply device cannot be satisfied. Disclosure of the invention

The present invention controls the induction heating roller by controlling the high frequency power supply. PT / JP2004 / 007840

, Four

It is a general object to provide a controllable induction heating roller device, a fixing device having the same, and an image forming device.

Further, the present invention provides an induction heating roller device that controls the high-frequency power supply device in accordance with an external signal so that the degree of heating of the induction heating roller can be smoothly changed without causing flicker of current. Another object of the present invention is to provide a fixing device and an image forming apparatus provided with the above.

Further, the present invention provides a method of controlling the high-frequency power supply in accordance with an external signal to change the degree of heating of the induction heating roller and changing the heating area of the heating roller. Another object of the present invention is to provide an induction heating roller device capable of adapting a heating area of a heating roller to a heated object having a different size, a fixing device including the same, and an image forming apparatus.

Still further, the present invention provides a method of controlling the high-frequency power supply in accordance with an external signal so that the degree of heating of the induction heating roller can be changed, and the influence of the temperature characteristic of the induction heating roller can be reduced. Another object of the present invention is to provide an induction heating roller device having improved practicality by controlling a high-frequency power supply device, and a fixing device and an image forming apparatus provided with the induction heating roller device.

In a first main embodiment of the present invention, an induction heating roller device includes an induction coil, a heating roller which generates heat by a secondary current flowing by being magnetically coupled to the induction coil, and energizes the induction coil A high-frequency power supply, wherein the high-frequency power supply converts a low-frequency AC voltage into a high-frequency AC voltage and outputs the high-frequency AC voltage, and controls the main circuit in response to an external signal to generate a low-frequency AC voltage. A control unit capable of outputting a high-frequency AC voltage under PWM control at a frequency sufficiently higher than the frequency and sufficiently lower than the frequency of the high-frequency AC voltage is provided as at least a common configuration.

Hereinafter, common components of the present invention will be described. Unless otherwise specified, the definitions and technical meanings of the terms are based on It is also applied to the following embodiments.

<About the high-frequency power supply device> The high-frequency power supply device outputs a controllable high-frequency AC voltage to energize the induction coil described later, and thereby transfers energy for heating the heating roller to the heating roller via the induction coil. It is a means for supplying and has a main circuit section and a control section.

(Regarding the main circuit section) The main circuit section is a circuit means for generally converting a low-frequency AC voltage indirectly, for example, converting to a DC voltage and then forming a high-frequency AC voltage. This is the circuit part that handles. However, if necessary, the low-frequency AC voltage may be directly converted to the high-frequency AC voltage. The low-frequency AC voltage can be obtained, for example, from a commercial AC power supply.

In the present invention, “high frequency” refers to a frequency of 20 kHz or more. If the frequency is higher than 200 kHz, preferably higher than 100 kHz, not only the high-frequency power supply device to be described later but also the peripheral circuits to which the high-frequency AC voltage is applied are significantly reduced in size. Since this is possible, it is suitable from the viewpoint of reducing the cost and weight of the high-frequency power supply device. If the frequency is 4 MHz or less, high-frequency characteristics are excellent, and a relatively inexpensive MOSFET can be used as an active element of a main circuit section and a control section described later. Is relatively easy to control. Furthermore, when a high-frequency power supply is used as a heating power supply for an air-core transformer-coupled induction heating roller device, it is possible to further increase the power transfer efficiency by increasing the Q of the induction coil. . When the power transmission efficiency increases, the overall heating efficiency increases, and power can be saved. In this case, the range of 1 to 4 MHz is particularly preferable from the viewpoints of economy of a compatible active element (for example, MOSFET) and ease of suppressing high-frequency noise. Therefore, in the present invention, the high frequency is preferably in the range of 20 kHz to 4 MHz.

When indirectly converting a low-frequency AC voltage to form a high-frequency AC voltage, PC orchid 004 840

6

A rectified DC power supply circuit is interposed between the low-frequency AC power supply and the high-frequency conversion circuit. The rectified DC power supply circuit is means for converting low-frequency AC into DC, and may include a rectifying means and, if necessary, a smoothing means. That is, the DC output voltage may be a smoothed DC voltage formed using a smoothing circuit or a non-smoothed DC voltage. However, a non-smooth DC voltage eliminates the need for a smoothing circuit and simplifies the circuit configuration, which is advantageous for reducing the size and weight of the induction heating roller device and reducing the cost. .

—On the other hand, the high-frequency generation function of the main circuit is not limited to a specific circuit type. A circuit element such as an amplifier or an inverter can be used for a high-frequency conversion circuit that generates a high frequency. As the amplifier, for example, a class E amplifier having high power conversion efficiency can be used. Further, as the inverter, for example, a half-bridge type inverter can be used. Regardless of the type of amplifier or amplifier used, a unit main circuit unit consisting of a plurality of amplifiers or inverters is connected in parallel, and the high-frequency outputs output from each unit main circuit unit are combined, that is, Then, the main circuit section can be configured to apply the voltage to the induction coil. This allows the output of each circuit section to be small while maintaining the desired power. Therefore, even if a MOSFET having a relatively small capacity is used as the active element, high-frequency can be generated inexpensively and efficiently.

In addition, the main circuit outputs a high-frequency AC voltage that is PWM-controlled by a control unit described below in order to control the degree of heating of the heating roller as desired. Therefore, during the period when the PWM control is being performed by the control unit, the main circuit unit uses the high-frequency AC that is sufficiently higher than the frequency of the low-frequency AC voltage by the PWM control and that is output from the main circuit unit. Intermittent operation is performed periodically at a frequency sufficiently lower than the frequency of the voltage to generate a high-frequency AC voltage intermittently.

In addition, the main circuit section can use a high-frequency power supply as necessary under the control of the control section. The frequency of the output voltage of the device can be configured to be variable. In this configuration, first, a plurality of induction coils are dispersed and arranged in the axial direction of the heating roller, and a desired induction coil among the plurality of induction coils is selectively energized to thereby form the heating roller. This is suitable when the heating region in the axial direction is changed to be selectable. That is, by changing the frequency of the output of the high-frequency power supply according to the external signal, it becomes possible to individually control the high-frequency power supplied to the plurality of induction coils. Second, the output frequency can be automatically controlled, and the conversion efficiency of the high-frequency AC voltage can be maintained at a predetermined high value. Furthermore, if necessary, thirdly, for example, the heating power may be increased at the time of startup by changing the frequency of the high-frequency AC voltage to be larger than that at the time of normal operation, and rapid heating may be performed. it can.

Furthermore, the main circuit section includes a rectified DC power supply circuit at a stage preceding the high-frequency conversion circuit, and a power factor improving capacitor is connected at a stage before or after the rectified DC power supply circuit. It is preferable that the capacitance is set to a value that can maintain a power factor of 0.8 or more as a whole when viewed from low-frequency alternating current. As a result, it is possible to suppress noise generated from the high-frequency power supply device from flowing out to the low-frequency AC power supply. Furthermore, the main circuit section is allowed to include a resonance circuit in order to efficiently output the generated high-frequency AC voltage. Further, by providing the resonance circuit, the high-frequency AC voltage can be shaped into a sine wave by shaping the high-frequency AC voltage, whereby the high-frequency AC voltage can be extracted with high efficiency, and the generation of the 周波 -frequency noise is reduced.

(Control Unit) The control unit includes at least a mode of performing PWM control of the main circuit unit in response to an external signal, and is configured to perform other control as desired. Other controls allow the main circuit section to be controlled in response to an external signal or to be automatically controlled as required. The PWM control is performed in such a manner that the PWM control is performed at a frequency sufficiently higher than the frequency of the low-frequency AC voltage and sufficiently lower than the frequency of the high-frequency AC voltage. The frequency of the PWM control is preferably not less than 10 times the frequency of the low-frequency AC voltage and not more than 1/10 of the frequency of the high-frequency AC voltage. As an example, when the frequency of the low-frequency AC voltage is 50 Hz and the high-frequency AC voltage is 2 MHz, the PWM frequency can be set to 25 kHz to 30 kHz. According to this embodiment, the high-frequency AC voltage can be smoothly changed to such an extent that on / off of the low-frequency AC current cannot be observed, and therefore, flicker of the current does not substantially occur.

In addition, when the low-frequency AC power is turned on, the main circuit can perform a soft start in which the high-frequency AC voltage is sequentially increased when the high-frequency AC voltage rises by the PWM control. As a result, flicker that occurs on the low-frequency AC power supply side due to a sudden change in the power supply can be avoided. Also, as a method different from the above for soft start, when the low-frequency AC power is turned on, the high-frequency AC voltage is generated by cutting off or cutting off the ON signal several times when the high-frequency AC voltage rises by PWM control. By not doing so, it is possible to employ effective soft-start control that sequentially increases the effective value of the high-frequency AC voltage.

Furthermore, in the control of the control unit for the main circuit unit, the control unit can be configured so that the PWM control is not performed when the main circuit unit generates the maximum output of the high-frequency AC voltage. However, it is also possible to configure the control unit so that the PWM control is performed even when the main circuit unit generates the maximum output, and the duty ratio is less than 100% at the maximum output. Thus, the PWM control can be continuously performed over the entire output range of the main circuit section. As a result, control can be performed using a microcomputer.

When the main circuit section is a separately excited type, the control section can include an oscillator for excitation, and an active element of the main circuit section, for example, a switch is used by using the oscillation output. A driving signal for driving the switching element. When the main circuit is self-excited, a high-frequency feedback control circuit can be used.

If the circuit constant of the heating roller changes with, for example, temperature, the high-frequency conversion efficiency of the main circuit section changes. Therefore, feedback control can be performed so as to maintain this conversion efficiency at a high value and to keep it constant.

In the present invention, the term “external signal” means a signal arriving from outside the induction heating roller device. For example, in the case of an image forming apparatus such as a copying machine equipped with the induction heating roller device, the This signal is selectively generated so that the induction heating roller device performs a desired operation in response to a user operation.

The control unit is configured to generate, for example, a PWM control signal in order to perform the PWM control operation. If the external signal is a digital signal, use a DZA converter to convert the external signal to an analog format as a pre-stage for performing a process to perform a PWM control operation such as a PWM control signal when an external signal arrives. Can be. When the external signal is an analog signal, circuit means for performing waveform shaping can be added. However, if necessary, the PWM control signal may be formed using the external signal as it is. The PWM control signal is not particularly limited as long as the signal controls the high-frequency power supply device according to the magnitude of the external signal. The signal is, for example, a phase signal proportional to the effective value of the external signal.

Further, the control unit may include a PWM switching circuit for PWM control. The PWM switching circuit operates in response to the PWM control signal and interrupts the oscillation output from the oscillator and the high-frequency feedback control signal. As a result, the intermittent oscillation output is controlled and input to the active element of the main circuit section, for example, the switching element, and the high-frequency AC voltage is intermittently generated at a frequency sufficiently higher than the frequency of the low-frequency AC voltage according to the PWM control. I do. However, if desired, for example, the maximum high-frequency AC voltage 10 If the PWM control is not performed at 0.0% and the PWM control is performed only at a certain level below 100%, short-circuit or control to prevent the PWM switching circuit from operating. It may be configured so as to be excluded from the department.

In addition, the high-frequency power supply device can add desired circuit means such as a high-frequency filter and / or a power factor improvement circuit, for example, a power factor improvement capacitor, in addition to the main circuit unit and the control unit described above. The high-frequency filter is a means for suppressing the high frequency generated by the high-frequency power supply device from flowing out to the low-frequency AC power supply side, and can employ a known circuit configuration. When a power factor improving capacitor is connected in parallel before or after the rectified DC power supply circuit, the power factor of the entire induction heating roller device can be increased to, for example, 80% or more, and the power factor generated by the high-frequency conversion circuit can be increased. It also has the effect of preventing high-frequency noise from flowing out to the low-frequency AC power supply.

<Induction coil> The induction coil is arranged to extend in the axial direction of the heating roller, and is energized, that is, excited or excited by a high-frequency power supply device. This is a means for transferring high-frequency AC power to the coil. For this purpose, the induction coil is inserted into the hollow heating roller and functions as the primary coil of the transformer, for example, a transformer coupling, preferably an air-core transformer coupling, with the secondary coil of the heating roller. It is configured to perform eddy current loss type magnetic coupling. In the case of the eddy current loss method, the induction coil may be inserted into a part of the heating roller or may be provided outside. When the induction coil is inserted inside the heating roller, the induction coil may be stationary with respect to the rotating heating coil, or may rotate together with or separately from the heating roller. When rotating, a rotating current collecting mechanism may be interposed between the high-frequency power supply device and the induction coil. In addition, “air-core transformer coupling” means not only a complete air-core transformer coupling but also an air core The meaning includes the case of trans bonding. For example, the configuration is such that no magnetic material is provided inside the induction coil.

In addition, the induction coil can be provided with a coil bobbin manufactured using a material having as little dielectric loss as possible in order to maintain the induction coil in a predetermined shape and a predetermined arrangement position. The coil bobbin can be formed with a groove having an axial thickness for accommodating the winding groove for the alignment winding and the power supply lead wire. However, the induction coil can be configured to be maintained in a predetermined shape and position by directly forming or bonding the induction coil with a synthetic resin or a vitreous material instead of the coil bobbin.

Further, the induction coil can be connected to the high-frequency power supply device via a power supply lead wire. The power supply lead wire for supplying high-frequency AC power from the high-frequency power supply to the induction coil should be placed close to the inner or outer surface of the induction coil. When the power supply lead wire passes through the inside of the induction coil, if the power supply lead wire is close to the center axis of the induction coil, the magnetic flux interlinking with the power supply lead wire increases, causing eddy current loss inside. This is not preferable because power transmission efficiency is reduced. On the other hand, with the above-described configuration, the amount of magnetic flux interlinking with the power supply lead wire is reduced, so that a decrease in power transmission efficiency is relatively suppressed.

Furthermore, the induction coil may be composed of a plurality of windings connected in series or in parallel, or a plurality of windings that are conductively mutually independent. When a plurality of induction coils are used, the heating rollers can be arranged separately in the axial direction of the heating roller and can be selectively energized by using an induction coil selection circuit described later, so that heating that can be selected for the heating roller can be achieved. Regions can be formed.

About the heating roller> The heating roller is provided with a secondary coil that forms a closed circuit when performing transformer coupling with the induction coil. And this secondary coil is transformer coupled with the primary coil, preferably Is air-core transformer-coupled. The secondary-side resistance of the closed circuit preferably has a value substantially equal to the secondary reactance of the secondary coil. Note that the secondary resistance and the secondary reactance are `` substantially equal '' when the secondary resistance is R a, the secondary reactance is X a, and Range. Also, the secondary resistance can be determined by measurement. The secondary reactance can be obtained by calculation.

2 5 <α <4

Further, the heating roller can be disposed such that the secondary coil has a single or a plurality of forms. In the case of a single secondary coil, it is desirable to dispose the secondary coil so as to extend over substantially the entire effective length of the heating port along the axial direction. When arranging a plurality of secondary coils, it is desirable to dispose them in the axial direction of the heating roller.

On the other hand, when the eddy current loss type magnetic coupling is performed between the heating roller and the induction coil, a heating layer made of a ferromagnetic material is arranged in the circling direction of the heating roller, as in the case of the transformer coupling. I have. This heating layer allows the same configuration as the secondary coil in the case of the transformer coupling method.

Further, the secondary coil or the heat generating layer can be formed to have a conductor such as a conductor layer, a conductive wire and a conductive plate. For the conductor layer, the following materials and manufacturing methods can be adopted in order to obtain a desired secondary-side resistance value or resistance value. In the case of forming a thick-film forming method (coating + calcination) is, A g, A g + P d, A u, P t, a material mainly composed of metal selected from the group consisting of R u O ₂ and C It is better to use As a coating method, a screen printing method, a roll coater method, a spray method, or the like can be used. On the other hand, when forming by plating, vapor deposition or sputtering, it is preferable to use a metal material selected from the group of Au, Ag, Ni and Cu + (Au, Ag). . The conductive wire and the conductive plate Copper and aluminum can be used.

Next, in order to obtain a more practical heating port, it is permissible to add the following configuration as necessary.

1. Roller substrate

In order to support the secondary coil or the heat generating layer, a roller base made of an insulating material or a metal can be used. In this case, the secondary coil or the heat generating layer can be disposed on the outer surface, the inner surface, or the inside of the roller base. The insulating roller base can be formed using ceramics or glass. In consideration of the heat resistance, strong impact resistance, and mechanical strength of the roller base, for example, the following materials can be used. Examples of ceramics include alumina, mullite, aluminum nitride, and silicon nitride. Examples of the glass include crystallized glass, quartz glass, and Pyrex. In the case of a roller base made of metal, for example, iron can be used.

2. Thermal diffusion layer

The heat diffusion layer can be provided above the conductor layer as necessary as a means for improving the degree of temperature uniformity in the axial direction of the heating roller. For this reason, the heat diffusion layer is preferably made of a material having good heat conduction in the axial direction of the heating roller. Materials with high thermal conductivity are often found in metals with high conductivity, such as Cu, Al, Au, Ag, and Pt. However, the thermal diffusion layer only needs to have a thermal conductivity equal to or higher than the material of the conductor layer. Therefore, the heat diffusion layer may be made of the same material as the conductor layer.

When the heat diffusion layer is made of a conductive material, the heat diffusion layer may be in conductive contact with the conductor layer. However, the provision of the heat diffusion layer via an insulating film also has an effect of blocking noise radiation. Since the high-frequency magnetic field does not act on the heat diffusion layer, a secondary current that contributes to heat generation is not induced in the heat diffusion layer.

3. About the protective layer The protective layer can be provided as necessary for mechanical protection and electrical insulation of the heating roller, or for improving elastic contact property or toner releasability. Glass can be used as the constituent material of the protective layer for the former, and synthetic resin can be used as the constituent material of the protective layer for the latter. The glass can be selected from the group consisting of borosilicate sub-glass, lead borosilicate glass, borosilicate glass and aluminosilicate glass. The latter can be selected from the group consisting of silicone resin, fluororesin, polyimide resin + fluororesin, polyamide + fluororesin. In the case of polyimide resin + fluorine resin and polyamide + fluorine resin, the fluorine resin is disposed outside.

4. Shape of heating roller

If desired, a crown can be formed on the heating roller. The crown may be in the shape of a drum or barrel.

5. Heating roller rotation mechanism

As a mechanism for rotating the heating roller, a known configuration can be appropriately selected and adopted.

About other configurations>

Although not an essential component of the present invention, a more effective induction heating roller device can be obtained by selectively implementing the following configuration as desired.

1. Warm-up control

During the warm-up period after start-up, that is, after the start of power supply, the heating roller can be controlled to rotate at a lower rotational speed than in the normal operation.

2. Heat roller temperature control

In order to keep the temperature of the heating roller constant within a predetermined range, for example, at 200 ° C, a heat-sensitive element can be brought into thermal contact with the surface of the heating roller. You. Then, the thermal element is connected to the temperature control circuit. As the thermal element, a thermistor having a negative temperature characteristic and a non-linear resistance element having a positive temperature characteristic can be used.

3. Conveyance sheet.

When heating the heated object using the heating roller, the heating roller can be configured to directly contact the heated object, but if necessary, a transport sheet is interposed between the two. can do. In this case, the transport sheet may be in the form of endless or roll. By using the transfer sheet, heating and transfer of the object to be heated can be performed smoothly.

<Regarding the Operation of the Present Invention> The present invention has the configuration described above, and thus exhibits the following operation, and as a result, has the following effects.

That is, the high-frequency power supply converts the low-frequency AC voltage and outputs a high-frequency AC voltage. The output high-frequency AC voltage is applied to the induction coil. When a high-frequency AC voltage is applied to the induction coil, a high-frequency magnetic field is generated from the induction coil and interlinks with the secondary coil of the heating roller or the heating layer. Therefore, in the case of the transformer coupling method, the induction coil serves as a primary coil, and a transformer coupling, preferably an air core transformer coupling, is formed between the induction coil and the secondary coil. As a result, since the secondary coil is formed as a closed circuit in the circumferential direction of the heating roller, a secondary current flows inside the secondary coil in the circumferential direction of the heating roller. Since the secondary coil has an appropriate secondary resistance, Joule heat is generated by the secondary current, and the heating roller is heated to increase the temperature. In addition, if the transformer is connected by high-frequency AC of 20 k 2 or more, the power transfer efficiency will be increased by the air-core transformer connection, for example, it will be 95% or more.

On the other hand, in the case of the eddy current loss method, the high-frequency magnetic field generated from the induction coil Since the bundle penetrates the heat generating layer and interlinks, an eddy current is generated around the magnetic flux in the heat generating layer, so that the resistance of the heat generating layer generates Joule heat.

By the way, the high-frequency power supply device is configured so that the control unit performs PWM control in response to an external signal, and as a result, the main circuit unit can output a high-frequency AC voltage. It is possible to arbitrarily adjust or adjust the high-frequency AC power transmitted to the heating roller via the heater as desired. For example, when heating the induction heating roller device from a cold state, the high-frequency AC voltage is set to a maximum value, for example, 100% or a value close to 100%. This allows rapid heating to the required temperature in a short time. In addition, the fixing speed can be increased by setting the high-frequency AC voltage to 100% or a value close to 100%. Further, when the heat consumption of the heating roller is large, for example, when the size of the fixing paper is large, good fixing can be obtained by increasing the output value of the high-frequency AC voltage. Conversely, after the temperature of the heating roller has risen, the high-frequency AC voltage is controlled to be low by the PWM control, so that the predetermined temperature can be easily maintained. Also, when the size of the fixing paper is small, the heat consumption is relatively small, so that the high-frequency AC voltage can be reduced by the PWM control. In the present invention, since the high-frequency AC voltage is changed by the PWM control, an effective high-frequency AC voltage having a desired value can be obtained while always maintaining high power transmission efficiency. Also, a high-frequency AC voltage can always be stably generated. Therefore, an induction heating roller device having high efficiency, high reliability, and variable output can be obtained.

In addition, the above-described PWM control is performed at a frequency sufficiently higher than the frequency of the low-frequency AC voltage and at a frequency sufficiently lower than the frequency of the high-frequency AC voltage, and is supplied because the high-frequency AC voltage is intermittent. There is no sudden change in high frequency power. As a result, the supplied high frequency power does not suddenly change to cause flicker in the temperature of the heating roller. The on / off state of the alternating current cannot be observed, so that the flicker of the low-frequency alternating current does not occur.

Further, in the present invention, since the PWM control is performed by controlling the main circuit portion of the high-frequency power supply device that generates the high-frequency voltage, the circuit configuration is simplified, and a small and inexpensive induction heating roller device is obtained. Can be.

Hereinafter, other embodiments of the present invention will be described.

In the second embodiment, the induction heating roller device is configured such that a plurality of the induction coils are disposed corresponding to a plurality of heating regions of the heating roller in addition to the configuration of the main first embodiment. And an induction coil selecting device for selecting an induction coil corresponding to a desired heating area among the plurality of induction coils by means other than the PWM control in order to switch the plurality of heating areas of the heating roller. I have.

This embodiment has a configuration suitable for arbitrarily switching the heating area of the heating roller. That is, a plurality of induction coils are provided corresponding to a plurality of heating regions of the heating roller, and a high-frequency AC voltage can be mainly applied to the selected induction coil. The heating area can be switched.

In the present embodiment, the induction coil selection device only needs to be configured to select a desired induction coil by means other than the PWM control, and the specific configuration is not particularly limited. Note that the PWM system is used as a means for adjusting or adjusting the high-frequency power supplied to the heating roller as described above.

Therefore, as a means for selecting an induction coil, for example, a filter circuit, a resonance circuit, a switch circuit, or the like can be employed. If there is one or more induction coils for which constant high-frequency AC power is to be supplied at all times among a plurality of induction coils, an induction coil selection device is not interposed between the induction coil and the high-frequency power supply. Is also good. But the rest The remaining induction coils are configured to be controlled to selectively supply high-frequency AC power by an intervening induction coil selection device. Further, by using the induction coil selection device, the application time of the high-frequency AC voltage to the induction coil can be changed. This makes it possible to make the high-frequency AC power supplied per unit length of the first and second induction coils the same, and also to change the input power per unit length. In order to control the application time of the high-frequency AC voltage, for example, PWM control can be performed in addition to the change in frequency. As a result, the actual application time at which the high-frequency AC power is actually applied can be different even if the application time is apparently the same.

Hereinafter, each configuration example of the induction coil selection device will be described.

(1) Configuration by filter circuit The filter circuit is interposed between the variable-frequency high-frequency power supply and the induction coil. Then, by changing the frequency of the high-frequency AC voltage applied to the filter circuit, high-frequency AC power is selectively supplied mainly to one or more desired induction coils among a plurality of induction coils. be able to.

(2) Configuration using a resonance circuit A resonance circuit is configured with an induction coil as a resonance circuit element. Since an induction coil mainly includes inductance, a resonance circuit can be generally configured simply by adding a capacitor. The resonance circuit may be either a series resonance circuit, a parallel resonance circuit, or a series-parallel resonance circuit for the variable-frequency high-frequency power supply device. In the former, a series connection circuit of an induction coil and a capacitor is connected to a variable-frequency high-frequency power supply. The middle person connects a parallel circuit of an induction coil and a capacitor to the variable-frequency high-frequency power supply. The latter also connects a series-parallel circuit. However, if necessary, inductance can be added in addition to the induction coil. And a plurality of resonance circuits including the first and second induction coils as resonance circuit components. In the case of configuration, the resonance frequencies are made to differ by at least two or more types.

Furthermore, if necessary, the magnitude of the selectivity Q can be configured to have at least two different values together with the resonance frequency among a plurality of resonance circuits.

(3) Configuration by switch circuit The switch circuit may be either a contact type or a non-contact type. The connection of the switch circuit to the induction coil is generally performed in series with a force S. If necessary, connect it in parallel and short-circuit the induction coil to cut off the supply of high-frequency AC power to the induction coil. It may be configured to ' Note that, in the latter connection mode, a plurality of induction coils can be connected in series to the high-frequency power supply device.

According to the present embodiment, the adjustment or adjustment of the high-frequency power to the heating roller via the induction coil can be performed by the PWM control, and the selection of the induction coil can be performed smoothly.

According to a third embodiment, in addition to the configuration of the second embodiment, the induction heating roller device is configured such that the induction coil selection device is configured to include a plurality of induction heating roller devices in response to a frequency of a high-frequency voltage output from the high-frequency power supply device. In addition to selecting a desired induction coil from the induction coils, the control unit of the high-frequency power supply device causes the induction coil selection device to respond to the frequency of the high-frequency voltage output from the main circuit unit in response to an external signal. Change.

This embodiment includes an effective induction coil selection device. In other words, the frequency of the high-frequency AC voltage and the PWM control can be easily separated electrically and easily controlled individually and independently. When the induction coil is selected by changing the frequency, the above-described configuration mainly including the filter circuit or the resonance circuit can be adopted as the induction coil selection device. These means are: Especially suitable.

In the fourth embodiment, in addition to the configuration of the second embodiment, the induction heating roller device includes a zero-cross detection circuit that detects a zero-cross of a low-frequency AC voltage and generates a zero-cross signal, and a signal based on an external signal. An induction coil selection control circuit that controls so as to select an induction coil corresponding to a desired heating area among a plurality of induction coils in synchronization with a zero cross signal generated from the zero cross detection circuit.

In the present embodiment, the control unit of the high-frequency power supply device controls the main circuit unit to apply the high-frequency AC voltage to the switched induction coil in synchronization with the detection of the zero-cross of the low-frequency AC voltage. In the present invention, “zero cross” means a phase including zero port of a low-frequency AC voltage and its vicinity. The zero-cross detection circuit can use a conventional circuit configuration for zero-cross detection. The configuration of the induction coil selection device may be any of the configurations described in the third embodiment.

Thus, according to the present embodiment, when the desired heating area of the heating roller is selected, when the secondary coil or the heating layer of the selected heating area is cooled and its resistance value is small. Even so, a high-frequency AC voltage is applied to the induction coil responsible for this heating region in synchronization with the zero-cross of the low-frequency AC voltage. Therefore, since the active element of the main circuit portion of the high-frequency power supply device, for example, the switching element is in a zero-cross state at the time of switching, a large current, that is, an overcurrent does not flow to the load as described in detail below.

That is, when the high-frequency AC voltage is generated by operating the main circuit of the high-frequency power supply near the maximum value of the low-frequency AC voltage as in the prior art, the current flowing through the active element of the main circuit at the time of startup is Is as follows:

I = ACV in_max / R In the above equation, R is the impedance on the load side as viewed from the active element in the main circuit of the induction coil, and ACV in_max is the maximum value of the low frequency AC voltage. Since the value of the load-side impedance R is small in a low temperature state, the current I flowing through the switching element becomes very large. In particular, when a large amount of power is applied to the heating roller, the load side impedance R needs to be reduced, so that the current I flowing at the time of startup becomes an extremely large value. Active elements that can be operated at startup such as when a large current flows, for example, switching, such as MOSFETs, have an extremely large operating current, for example, switching current and permissible loss. It is expensive and narrows the selection range of active devices. Therefore, there is a problem that the induction heating roller device becomes expensive and the circuit design becomes difficult.

On the other hand, in the present embodiment, as can be understood from the above configuration, when the control unit controls the main circuit unit to change the high-frequency AC output, the control unit synchronizes with the detection when a zero cross is detected. As a result, the control section operates, so that the current flowing during startup decreases. Therefore, the active elements used in the main circuit section need only have relatively small operating current and allowable loss, so they are inexpensive, small, and have a wide selection range of active elements. 'Therefore, there is an advantage that the induction heating roller device is inexpensive, the circuit design is easy, and the reliability is high.

In the fifth embodiment, in the induction heating roller device, in addition to the configuration of the main first embodiment of the present invention, the control unit of the high-frequency power supply device receives an external signal and generates a PWM control signal. A PWM control signal generating circuit, an oscillator that determines the frequency of a high-frequency AC voltage, and a PWM that is interposed between the oscillator and the main circuit and that switches according to a PWM control signal generated by the PWM control signal generating circuit. It has a switching circuit.

In this embodiment, a circuit configuration suitable for controlling the high-frequency AC voltage by PWM is described. Is shown. That is, the PWM control signal generating circuit receives the external signal and generates a PWM control signal. The external signal may be either a digital signal or an analog signal. Digital signals can be converted to analog signals by interposing a DZA converter. In case of analog signal, it can be used as it is. However, when the waveform is distorted or the voltage is low, it can be used after shaping the waveform using a waveform shaping circuit.

The PWM control signal generating circuit is a circuit for converting the external signal into a PWM control signal corresponding to the external signal, that is, a signal having a PWM control phase, and a known circuit can be used. For example, an analog signal corresponding to an external signal is input to one input terminal of the operational amplifier, and a triangular wave signal or a sawtooth wave signal is input to the other input terminal. Alternatively, a soft comparator may be used in place of the above. Then, a PWM control signal can be obtained from the output terminal. In the PWM control signal, the ratio between the on-duty and the off-duty, that is, the duty ratio, is set to a predetermined value in a given switching cycle.

The oscillator supplies an excitation signal for indirectly or directly driving the main circuit unit at a predetermined cycle. Therefore, the oscillator determines the frequency of the high-frequency AC voltage. To drive indirectly, a drive signal generating circuit can be interposed between the oscillator and the main circuit section as described later.

The PWM switching circuit is interposed between the oscillator and the main circuit. Then, the oscillation signal of the oscillator is turned on and off according to the PWM control signal generated from the PWM control signal generation circuit. Generally, an oscillation signal output from an oscillator is converted into a drive signal by control input to a drive signal generation circuit. Note that, if desired, the PWM control signal generation circuit can be arranged so as to be inserted between the drive signal generation circuit and the main circuit section. When the drive signal generation circuit is not used, the connection between the oscillator and the main circuit In this case, a PWM switching circuit may be interposed.

In this embodiment, when an external signal arrives, the PWM control signal generation circuit generates a PWM control signal. Then, the PWM control signal is control-input to the PWM switching circuit of the control unit of the high-frequency power supply device. As a result, the PWM switching circuit performs switching according to the PWM control signal, so that the oscillation signal of the oscillator is interrupted in response to the PWM control signal. As a result, the high-frequency AC voltage generated in the main circuit is PWM-controlled.

Thus, according to the present embodiment, the circuit configuration for controlling the main circuit that generates the high-frequency AC voltage and performing the PWM control is simple, and high reliability can be obtained.

In the sixth embodiment, in the induction heating roller device, in addition to the configuration of the main first embodiment of the present invention, the maximum value of the high-frequency AC voltage output from the high-frequency power supply device is less than 100% in the duty ratio. It is configured to be obtained by the PWM control of the above.

The present embodiment is a configuration suitable for adjusting the high-frequency AC power transmitted to the heating roller as desired by controlling the high-frequency AC voltage by PWM. That is, the maximum value of the high-frequency AC voltage output from the high-frequency power supply can be obtained by PWM control with a duty ratio of less than 100%. Therefore, the high-frequency power supply device can be configured to perform the PWM control over the entire voltage adjustable range from the minimum value to the maximum value.

When the high-frequency AC voltage output from the high-frequency power supply is configured to be adjustable, the maximum value of the high-frequency AC voltage is 100% duty ratio, in other words, it is fully conductive, and the lower level is less than 100% duty ratio. It is common to set it to Then, when all conductions are made, the connection is made directly without passing through the PWM control circuit.

However, when performing PWM control of the high-frequency AC voltage of the high-frequency power supply device, the reactance in the drive signal generation circuit and the high-frequency conversion circuit, for example, connecting to the circuit. The rising of the high-frequency AC voltage when the PWM control is on is deteriorated due to the influence of the parasitic capacitance generated in the connected circuit and the circuit, and the linearity between the duty ratio and the high-frequency AC voltage tends to decrease. . Along with this, there is a problem that the on-duty ratio becomes discontinuous between 100% and less. Another problem is that circuit design becomes relatively difficult.

According to this embodiment, the discontinuity between the on-duty ratio of 100% and less does not occur. Also, by using a microcomputer, it is possible to cope with only the software surface, which facilitates the circuit design of the high-frequency power supply device and is advantageous in terms of cost. Furthermore, since control can be digitized, control accuracy can be increased.

In the seventh embodiment, in the induction heating roller device, in addition to the configuration of the main first embodiment of the present invention, the control unit of the high-frequency power supply device controls the phase of the high-frequency AC voltage and the phase of the high-frequency AC current. When the difference exceeds a predetermined value, the operation of generating the high frequency AC voltage is stopped.

The present embodiment has a configuration suitable for performing a protection operation when an abnormality of the high-frequency AC output occurs, as described below.

The voltage phase and the current phase of the high-frequency alternating current can be detected by providing respective detection circuits. Further, these can be detected on the high-frequency AC output side of the high-frequency power supply device, but the phase of the high-frequency AC voltage and the phase that approximates the phase of the high-frequency AC current may be detected on the low-voltage side. Then, detection becomes possible on the low voltage side, and the circuit configuration becomes simpler, and the cost becomes lower.

A circuit for detecting the phase difference between the high-frequency AC voltage and the high-frequency AC current is not particularly limited, but a PLL circuit is preferable.

Thus, according to the present embodiment, when the output of the high-frequency AC power is performed normally, the phase difference between the voltage phase and the current phase of the high-frequency AC power is appropriate. Within a predetermined range. However, if the output of the power S and the high-frequency AC power becomes abnormal, the above-mentioned phase difference becomes small or large and deviates from the predetermined range. Let In addition, the configuration of the protection circuit is simple, miniaturization and cost reduction are possible, abnormality detection and protection operation are assured, and the reliability of the induction heating roller device is improved.

In the eighth embodiment, in addition to the configuration of the main first embodiment of the present invention, the induction heating roller device further comprises a main circuit portion of the high-frequency power supply device, which has a rectifier for converting a low-frequency AC voltage into a DC voltage. DC heating circuit, high-frequency conversion circuit that converts DC voltage to high-frequency AC voltage, and induction heating roller that is connected in parallel to at least one of the first and second stages of the rectified DC power circuit and viewed from the low-frequency AC power supply The entire system is equipped with a capacitor having a capacitance capable of holding a power factor of 0.8 or more.

This embodiment is suitable for suppressing the noise generated from the high-frequency power supply from flowing out to the low-frequency AC power supply.

In the present invention, “power factor of 0.8 or more” is a value when the high-frequency power supply device has a rated output. Therefore, it is not at the time of high-speed heating at the maximum output state. The power factor is preferably 0.85 or more. In addition, if necessary, a single multi-yoke can be inserted in a stage preceding the capacitor, whereby the outflow of high-frequency noise can be further reduced.

Thus, according to the present embodiment, since the capacitor connected in parallel to at least one of the former stage and the latter stage of the rectified DC power supply circuit absorbs the noise generated from the high frequency power supply device, the noise is reduced to the low frequency. Suppress to flow to AC power supply. Further, since the power factor of the induction heating heater is maintained high by the connection of the capacitor, the load fluctuation of the high-frequency AC power is reduced.

In the ninth embodiment, the induction heating roller device is a In addition to the configuration of the first embodiment, the main circuit of the high-frequency power supply is connected in parallel with a rectified DC power supply circuit for converting a low-frequency AC voltage to a DC voltage. It is equipped with a plurality of high-frequency conversion circuits that convert the DC voltage from the integrated DC power supply circuit to a high-frequency AC voltage and output it collectively.

This embodiment is suitable for using a MOSFET in the main circuit of the high-frequency power supply device.

MOSFETs have excellent frequency characteristics for high frequencies of 20 kHz or higher, but do not provide elements with relatively large power, as handled by induction heating roller devices. In contrast, in the IGBT element, it is possible to obtain a large element of the power can not be obtained having a frequency characteristic to withstand 2 0 k H _Z over high frequency.

In this embodiment, a plurality of high-frequency conversion circuits are controlled collectively and output collectively. In order to control a plurality of high-frequency conversion circuits collectively, a distributor may be interposed between the control signal source and each control input terminal of the plurality of high-frequency conversion circuits. Also, in order to output the high-frequency AC voltages of a plurality of high-frequency conversion circuits at once, the output terminals of the plurality of high-frequency conversion circuits may be connected together via a synthesizer. 'Known distributors and synthesizers can be used. Further, when performing feedback control of the high-frequency AC voltage and / or the high-frequency AC current, the feedback signal may be fed back to the combined high-frequency output terminal or low-frequency AC input terminal via a synthesizer.

Then, according to the present embodiment, since a plurality of high-frequency conversion circuits operate in parallel, it is possible to control and operate as if they were a single high-frequency conversion circuit. Therefore, the configurations of the control circuit and the output circuit are simplified, the number of circuit components can be reduced, and the mounting area is reduced.

Also, the high-frequency AC power handled by each high-frequency conversion circuit Since the value can be divided by the number of conversion means, it is possible to use a switching element used in the high-frequency conversion circuit having a relatively small current capacity. Therefore, a high-frequency conversion circuit can be configured using MOSFETs having excellent frequency characteristics.

In the tenth embodiment, in addition to the configuration of the main first embodiment of the present invention, the induction heating roller device includes a control circuit of the high-frequency power supply device that converts a high-frequency AC voltage output from the main circuit unit. An analog control circuit that controls the frequency so as to maintain the efficiency at a predetermined level is included.

This embodiment has a configuration suitable for compensating for a change in electrical characteristics due to a temperature change of the heating roller.

In the induction heating roller device, in the heating roller, the secondary coil or the heating layer has a resistance value and an inductance. The resistance value is determined by the resistivity of the constituent material of the secondary coil or the heat generating layer, and the inductance is determined by the magnetic permeability of the base on which the secondary coil or the heat generating layer is supported. Therefore, these values are functions of the temperature of the heated roller. For this reason, fluctuations in these constants cannot be ignored between starting the induction heating roller device when the heating roller is cold and during operation while the heating roller is heated. Variations in these constants affect the operation of the induction heating roller device. For example, when the equivalent resistance of the secondary coil or the heating layer changes, the high-frequency AC power input to the heating roller changes. Also, when the equivalent inductance of the secondary coil or the heating layer changes, the phase difference between the high-frequency AC voltage and current changes, and the high-frequency conversion efficiency of the high-frequency power supply changes. Therefore, there is a problem that it is difficult to obtain a desired operation of the guide roller device.

In the present embodiment, the analog control circuit controls the frequency so as to maintain the conversion efficiency of the high-frequency power supply at a predetermined value. In the present invention, the “analog control circuit” refers to an analog circuit operation for controlling frequency control. Controlled circuit. If the magnetic permeability in the secondary coil or the heating layer of the heating roller fluctuates, the conversion efficiency of the main circuit part fluctuates as described above, so the analog control circuit functions to maintain the fluctuation of the conversion efficiency within a predetermined range I do. The specific configuration of the analog control circuit is not particularly limited. For example, a PLL (phase locked loop) circuit is suitable. When an analog control circuit is configured using a PLL circuit, the voltage and current of the high-frequency AC output are fed back, their phases are compared, and the phase difference signal is used to generate an oscillator, for example, the oscillation frequency of a voltage-controlled oscillator (VCO). Is subjected to negative feedback control. Then, a drive signal for the main circuit is generated using the oscillation output of the oscillator. In addition, a low-pass filter and an amplifier can be interposed in the feedback circuit of the phase difference signal. Further, the circuit for detecting the phase difference is allowed to be used also as the phase difference detection circuit used in the eighth embodiment.

Thus, in the present embodiment, undesired fluctuations in the conversion efficiency and high-frequency AC power output of the high-frequency power supply due to fluctuations in the inductance and resistance of the secondary coil or the heat generating layer due to the temperature change of the heating roller. It can be suppressed. In addition, since the analog control and the PWM control are combined, the circuit configuration of the control unit of the induction roller heating device can be relatively simplified, contributing to downsizing and cost reduction of the induction roller heating device. At the same time, desired high-frequency AC power can be stably supplied to the heating roller, thereby improving operability.

When a resonance circuit including an induction coil is connected to the high-frequency AC output terminal of the high-frequency power supply device, the phase difference between the voltage phase and the current phase of the high-frequency AC becomes constant using an analog control circuit. With such control, when the inductance of the induction coil changes, the operating point on the resonance characteristic curve is kept constant even if the resonance characteristic of the resonance circuit changes. As a result, the frequency conversion efficiency can be kept constant, and the high-frequency AC power can be kept constant. According to such a configuration, for PWM control Even without a circuit, fluctuations in high-frequency AC power due to changes in circuit constants due to temperature changes of the heating roller can be reduced, further simplifying the circuit configuration and contributing to downsizing and cost reduction. .

In the eleventh embodiment, the induction heating roller device includes, in addition to the configuration of the main first embodiment of the present invention, a zero-cross detection circuit that detects a zero-cross of a low-frequency AC voltage and generates a zero-cross signal. The control unit of the high-frequency power supply device is configured to switch the output of the high-frequency AC voltage from the main circuit from an off state to an on state in synchronization with a zero-cross signal in response to an external signal.

In this embodiment, when the high-frequency AC voltage output from the high-frequency power supply device is switched from the off state to the on state in order to start the heating of the heating roller, the switching is performed in synchronization with the zero cross signal. In this embodiment, the number of induction coils may be either single or plural, and in the case of plural, it is not necessary to switch between them. The zero-cross detection circuit can be shared with that in the fourth embodiment.

Thus, according to the present embodiment, the current flowing at the time of starting is reduced, so that the switching element used in the main circuit section is inexpensive, small-sized and has a small element selection, as in the fourth embodiment. Since the range is wide, the induction heating roller device is inexpensive, the circuit design is easy, and the reliability is high.

In the twelfth embodiment, the induction heating roller device has the same configuration as the main first embodiment of the present invention. In addition, the control unit of the high-frequency power supply device performs PWM control when the low-frequency AC power is turned on. When the on-duty rises, the main circuit is soft-start controlled.

In the present embodiment, the soft start control can use the configuration described in the main embodiment of the present invention.

Thus, according to the present embodiment, the power changes suddenly when the low-frequency AC power is turned on. The flicker of the low-frequency alternating current generated by the operation is reduced.

A fixing device according to an aspect of the invention includes a fixing device main body including a pressure roller, a recording medium having a heating roller facing the pressure roller of the fixing device main body, and a toner image formed between the two rollers. And the induction heating roller device of the present invention described above, which is disposed so as to fix the toner image while transporting the toner image.

In the present invention, the “main body of the fixing device” refers to a remaining portion excluding the induction heating roller device from the fixing device.

The pressing roller and the heating roller may be in ft contact pressure contact, but may be indirectly pressed via a conveyance sheet if necessary. Note that the transport sheet may be endless or roll-shaped.

Thus, in the present invention, the toner image can be fixed at a high speed while transporting the recording medium on which the toner image is formed between the heating roller and the pressing roller.

An image forming apparatus according to the present invention includes: an image forming apparatus main body including an image forming unit that forms a toner image on a recording medium; and an image forming apparatus main body that is provided in the image forming apparatus main body and fixes the toner image on the recording medium. And the fixing device.

In the present invention, the “image forming apparatus main body” refers to a remaining portion excluding the fixing device from the image forming apparatus. Further, the image forming means is means for forming an image for forming image information on a recording medium by a locking method or a direct method. The “indirect method” refers to a method of forming an image by transfer. Examples of the image forming apparatus include an electrophotographic copying machine, a printer, and a facsimile.

As the recording medium, for example, a transfer material sheet, a printing paper, an electric flux sheet, an electrostatic recording sheet, and the like are applicable.

Thus, the present invention provides an image forming apparatus suitable for a high-speed type. Can be BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a circuit block diagram of a main part showing a first embodiment for implementing the induction heating roller device of the present invention.

FIG. 2 is a circuit diagram of an inverter, an induction coil, and a heating roller of the main circuit of the high-frequency power supply device.

FIG. 3 is also a partially cut-away central longitudinal sectional view of the induction coil and the heating roller.

FIG. 4 is a cross-sectional view of the induction coil and the heating roller.

FIG. 5 is a voltage waveform diagram of each part.

FIG. 6 is a circuit block diagram of a main part showing a second embodiment for implementing the induction heating roller device of the present invention.

FIG. 7 is a circuit block diagram of a main part showing a third embodiment for implementing the induction heating roller device of the present invention.

FIG. 8 is a circuit block diagram of a main part showing a fourth embodiment for implementing the induction heating roller device of the present invention.

FIG. 9 is a circuit block diagram of a main part showing a fifth embodiment for implementing the induction heating roller device of the present invention.

FIG. 10 is a waveform diagram showing a high-frequency AC voltage waveform when the power is turned on.

FIG. 11 is a waveform diagram showing a high-frequency AC voltage waveform showing a sixth embodiment for implementing the induction heating roller device of the present invention.

FIG. 12 is a circuit block diagram of a main part showing a seventh embodiment for implementing the induction heating roller device of the present invention.

FIG. 13 is a waveform diagram showing voltage waveforms in the respective units. FIG. 14 shows an eighth embodiment for implementing the induction heating roller device of the present invention. FIG. 3 is a circuit block diagram of a main part showing an embodiment.

FIG. 15 is a circuit block diagram showing the connection relationship between the induction coil selection circuit, a plurality of induction coils, and the heating roller.

FIG. 16 is a waveform diagram showing voltage waveforms in the respective units. FIG. 17 is an overall circuit block diagram showing a ninth embodiment for implementing the induction heating roller device of the present invention.

FIG. 18 is a main circuit block diagram showing the control unit in more detail.

FIG. 19 is a circuit diagram of the analog control circuit.

FIG. 20 is an overall circuit block diagram showing a tenth embodiment for implementing the induction heating roller device of the present invention.

FIG. 21 is a circuit diagram of the protection judgment circuit.

FIG. 22 is a graph similarly explaining the protection operation.

FIG. 23 is a circuit block diagram showing a first embodiment for implementing the induction heating roller device of the present invention.

FIG. 24 is a circuit block diagram showing a twelfth embodiment for implementing the induction heating roller device of the present invention.

FIG. 25 is a circuit block diagram showing a thirteenth embodiment for implementing the induction heating roller device of the present invention.

FIG. 26 is a conceptual cross-sectional view showing one embodiment for implementing the image forming apparatus of the present invention.

FIG. 27 is a conceptual cross-sectional view of a copying machine as an embodiment for implementing the image forming apparatus of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments for implementing the present invention will be described with reference to the drawings.

As shown in FIG. 1 to FIG. 5, the induction heating roller device of the present invention The first mode for carrying out the invention includes a high-frequency power supply HFS, a heating roller HR, and an induction coil IC, and has an input terminal connected to a low-frequency AC power supply AS. This embodiment corresponds to the first and fifth embodiments of the present invention.

<About low-frequency AC power supply AS> The low-frequency AC power supply AS is composed of, for example, a 100 V commercial AC power supply.

> High-frequency power supply HFS> It is composed of a main circuit section MC and a control section CC.

The main circuit part MC consists of a rectified DC power supply circuit (not shown) and a half-bridge type inverter using the MOSFET shown in FIG. 2, that is, a high-frequency conversion circuit I NV.

The rectified tf current power supply circuit consists of a prism type rectifier circuit and a smoothing capacitor.The AC input terminal is connected to the low-frequency AC power supply AS, and the DC output terminal is connected to the main circuit MC described later. . A rectified and smoothed DC voltage is generated at the DC output terminal.

The high-frequency conversion circuit INV mainly includes a pair of MOSFETs Q1, Q2, a pair of capacitors C1, C2, a DC cut capacitor C3, and a resonance circuit RC. The pair of MOSFETs Ql and Q2 are connected in series between the DC output terminals of the rectified DC power supply circuit. The pair of capacitors Cl and C2 are connected in parallel to the pair of MOSFETs Ql and Q2. The DC power capacitor C3 is inserted in series so as to power the DC component when extracting a high-frequency switching voltage appearing between the drain and source of the MOSFET Q2. The resonance circuit RC forms a series resonance circuit of the resonance inductor L1 and the resonance capacitor C4. Then, a sine wave high frequency AC voltage is output between both ends of the resonance capacitor C4. Then, the high-frequency AC voltage is applied to the induction coil IC. In FIG. 2, ws is the secondary coil of the heating roller HR, and Ra is the equivalent resistance of the secondary coil SC. As shown in FIG. 1, the control unit CC includes a PWM control signal generation circuit PSG, Oscillator OSC, PWM switching circuit SC and drive signal generation circuit (not shown) are provided.

The PWM control signal generation circuit PSG includes a DZA converter DAC, a triangular wave generation circuit TG, and an operational amplifier PA, and generates a PWM control signal according to an external signal coming from an external signal source SS. The D / A converter DAC converts a digital signal type external signal into an analog signal. The triangular wave generation circuit TG generates a triangular wave. An operational amplifier PA receives an analog external signal at one input terminal and a triangular wave at the other input terminal, and generates a PWM control signal while the instantaneous value of the triangular wave is higher than the level of the external signal. I do. The external signal source S S generates an external signal in response to an operation of a device incorporating an induction heating roller device, for example, a main body of a copying machine or the like. In the present embodiment, the external signal is, for example, a digital signal of several bits.

The oscillator OSC generates an oscillation signal that determines the frequency of the high-frequency AC voltage generated from the main circuit unit MC.

The PWM switching circuit SC operates in response to the PWM control signal to interrupt the oscillation signal output from the oscillator OSC. The drive signal generation circuit converts the intermittent oscillation into an intermittent drive signal for MOSFETs Ql and Q2.

Heating roller HR> As shown in FIG. 3, the heating roller HR includes a roller base 1, a secondary coil ws, and a protective layer 2, and is driven to rotate by a rotation mechanism RM.

The roller substrate 1 is made of a cylindrical body made of alumina ceramics and has a length of, for example, 300 mm and a thickness of 3 mm.

The secondary coil _w s, formed of a cylindrical one-turn coil forms a film-like formed of deposited film of C u, the outer surface of the roller base 1, is disposed over substantially. Overall axial chromatic Kocho I have. The thickness of the secondary coil ws is determined by the secondary resistance in the circumferential direction, that is, the equivalent resistance R is equal to the secondary reactor It is set to 1 Ω which is almost the same value as

The protective layer 2 is made of a fluororesin, and is formed by covering the outer surface of the secondary coil SC.

The rotation mechanism RM is a mechanism for rotating the heating roller HR, and is configured as follows. That is, as shown in FIGS. 3 and 4, a first end member 3A, a second end member 3B, a pair of bearings 4, 4, a bevel gear 5, a spline gear 6, and a motor 7 are provided. It is composed of

The first end member 3A includes a cap 3a, a drive shaft 3b, and a point 3c. The cap 3a is fitted to the left end of the heating roller H in FIG. 3 of the heating roller H from the outside, and is fixed to the heating roller HR using a pressing screw (not shown) so that the left end of the heating roller HR is fixed. I support it. The drive shaft 3b projects outward from the center of the outer surface of the cap 3a. The point 3c protrudes inward from the center of the inner surface of the cap 3a.

The second end member 3B includes a ring 3d. The ring portion 3d is fitted to the right end in FIG. 2 of the heating roller HR from the outside, and is fixed to the heating roller HR by using a pressing screw (not shown) to thereby fix the heating roller HR. Supports the right end of the HR.

One of the pair of bearings 4, 4 rotatably supports the outer surface of the cap portion 3a of the first end member 3A. The other rotatably supports the outer surface of the second end member 3B. Therefore, the heating roller HR is rotatably supported by the first and second end members 3A and 3B fixed to both ends thereof and the pair of bearings 4 and 4.

The bevel gear 5 is mounted on a drive shaft 3b having a first terminal 3A. The spline gear 6 is combined with the bevel gear 5. The motor 7 has a motor shaft directly connected to the spline gear 5. Regarding the induction coil IC> As shown in FIG. 3 and FIG. 4, the induction coil IC is wound around the coil bobbin 8 and is dispersedly arranged in the axial direction of the heating roller HR. Also, a series connection is made between a pair of power supply leads 9a and 9b, and both ends are connected to the output terminal of the high-frequency power supply device HFS via the power supply leads 9a and 9b.

The coil bobbin 8 is made of a fluorocarbon resin cylinder, and has a Dfl portion 8a, a support portion 8b, and a communication groove 8c. The concave portion 8a is formed at the center of the distal end of the coil bobbin 8, and is relatively rotatably locked to the rotating mechanism RM. The support portion 8b is formed at the base end of the coil bobbin 8, and is fixed to a fixing portion (not shown). The communication groove 8c is formed in a part of the outer surface of the coil bobbin 8 in a gutter shape along the axial direction, and accommodates the power supply lead wires 9a and 9b therein. The power supply leads 9a and 9b are housed in the communication groove 8c as shown in FIG. 4, and are led out from the base end of the coil pobin 8 to the outside. Connect to the output end via a coaxial cable.

Then, the induction coil IC is used in a stationary state, and the power supply lead wires 9a and 9b are housed in the communication groove 8c and are close to the induction coil IC. Since there is almost no intersection, eddy current loss hardly occurs in the power supply leads 9a and 9b.

On the other hand, the induction coil IC is inserted into the inside of the heating roller HR from the ring portion 3d of the second end member 3B, and the concave portion 8a formed at the tip of the coil bobbin 8 has the first portion. The supporting portion 8 d formed at the base end is fixed to the fixed portion as described above, by engaging with the point 3 c of the end plate 3 A, thereby supporting the heating roller HR coaxially. The stationary state is maintained even when the heating roller HR rotates.

Circuit Operation> Next, the circuit operation in the present embodiment will be described with reference to FIG. 1 to FIG. 2004/007840

37

When the low-frequency AC power supply AS is turned on, the low-frequency AC voltage is converted into a rectified and smoothed DC voltage by the rectified DC power supply means, and the DC power is supplied to the DC input terminal of the main circuit section MC.

On the other hand, when the external signal SG1 shown in FIG. 5 (a) arrives from the external signal source SS via the DZA converter DAC, the external signal is sent from the PWM control signal generation circuit PSG as shown in FIG. 5 (b). A PWM control signal SG2 having an on-duty corresponding to the signal level is generated and input to the PWM switching circuit SC. The PWM control signal SG 2 has the time width Ton with respect to the cycle T, and the duty ratio DR becomes Ton / T = TonZ (Τοη + Toff). Toff is a pause period.

On the other hand, the oscillation signal SG3 is continuously generated from the oscillator OSC of the control section CC of the high-frequency power supply HFS as shown in FIG. 5 (c). The oscillation signal SG3 is intermittently generated by the PWM switching circuit SC according to the time width of the PWM control signal SG2 as shown in FIG. 5 (d) to form an oscillation signal SG4 which is PWM-controlled. The PWM-controlled oscillation signal SG4 is control-input to a drive signal generation circuit (not shown). The drive signal generation circuit converts the oscillation signal SG3 into an intermittent drive signal according to the duty ratio of the PWM control signal SG2, and inputs the control signal to the main circuit unit MC.

The main circuit MC of the high-frequency power supply HF S has a sine-wave high-frequency AC voltage HF that is PWM-controlled as shown in Fig. 5 (e) by switching the MO SFE TQ 1 and Q 2 alternately according to the drive signal. Is output. Since the high frequency AC voltage HF is generated intermittently by PWM control, its effective value is controlled according to the duty ratio DR. In addition, the frequency 1 / T of the PWM control is sufficiently higher than the frequency of the low-frequency AC voltage and sufficiently lower than the frequency of the high-frequency AC voltage HF, so that flicker does not occur. Since the high-frequency AC voltage HF is applied to the induction coil IC via the pair of power supply leads 9a and 9b, the induction coil IC is excited and Generates a magnetic field. Since the high-frequency magnetic field links with the secondary coil ws of the heating roller HR due to the air-core transformer coupling, an induced current flows through the secondary coil ws.

The heating roller HR generates Joule heat due to the induction current flowing through its secondary coil ws, and its temperature rises and is heated as required. Thus, the heating of the heat roller HR is appropriately controlled by the degree of the PWM control. Hereinafter, other embodiments for implementing the induction roller heating device of the present invention will be described with reference to FIG. 6 to FIG. In each of the drawings, the same parts as those in FIG. 1 to FIG.

In the second embodiment for implementing the induction heating roller device of the present invention shown in FIG. 6, in the external signal source SS, an external signal composed of an analog signal is supplied to a PWM control signal generation circuit PSG of the control unit CC. Send out. The PWM control signal generation circuit PSG includes a waveform shaping circuit RSC, and is configured to shape the waveform of an external signal by the waveform shaping circuit RSC, and then control-input the signal to the operational amplifier PA. Other configurations are the same as those in the first embodiment. This embodiment corresponds to the first and fourth embodiments of the present invention.

In a third embodiment for implementing the induction heating roller device of the present invention shown in FIG. 7, the external signal source SS is the same as the second embodiment in that the external signal is an analog signal. The PWM control signal generating circuit PSG is configured to control-input an external signal directly to the operational amplifier. It can be used when the waveform of the external signal does not collapse and when there is no problem in inputting control to the operational amplifier PA. This embodiment corresponds to the first and fourth embodiments of the present invention.

In a fourth embodiment for implementing the induction heating roller device of the present invention shown in FIG. 8, the maximum high-frequency AC voltage of the high-frequency power supply device is 100 ° /. PW less than It is configured to be output by M control. This embodiment corresponds to the sixth embodiment of the present invention.

The PWM control signal generation circuit PSG has a voltage divider VD interposed between the external signal source SS and the operational amplifier PA, and reduces the external signal so that it becomes smaller than the peak value of the reference voltage compared with this. Let me. Further, the reference voltage is composed of a saw-tooth wave formed by the saw-tooth wave generation circuit TG ′. Further, the PWM switching circuit SC is constituted by an AND circuit, and the output of the PWM switching circuit SC is controlled and input to the drive signal generation circuit GDC. Other configurations are the same as those of the first embodiment.

The fifth embodiment for implementing the induction heating roller device of the present invention shown in FIG. 9 and FIG. 10 corresponds to a modified example of the PWM control and is used when the low-frequency AC power supply to the induction heating roller device is turned on. , The high frequency power supply HFS is configured to be soft-started when the on-duty rises in the PWM control. This embodiment corresponds to the twelfth embodiment of the present invention.

The high-frequency power supply HFS has a main circuit part MC including a rectified DC power supply circuit R DC and a high-frequency conversion circuit I NV. The control section C C comprises a control operation circuit C O and a drive signal generation circuit G DC. The control operation circuit C0 includes a twisting circuit, a PWM switching circuit, and a soft start control circuit. The soft start control circuit sequentially increases the drive signal generated from the drive signal generation circuit GDC when the on-duty rises by the PWM control when the low-frequency AC power is turned on.

An input detection circuit IDC is provided to detect the input of the low-frequency AC power supply AS. The input detection circuit IDC is inserted between the low-frequency AC power supply AS and the rectified DC power supply means RDC. Then, the detection output is control-input to a soft start control circuit in the control operation circuit CO.

The PWM control signal generation circuit PSG receives an external signal from the external signal source SS. Then, a PWM control signal is generated and control input to the PWM switching circuit PC. Therefore, the oscillation signal is PWM-controlled and sent to the drive signal generating circuit GDC to control the high-frequency AC voltage by PWM.

Then, when the low-frequency AC power supply AS is turned on, the high-frequency power supply HFS is soft-started, and the high-frequency AC voltage sequentially increases as shown in FIG.

A sixth embodiment for implementing the induction heating roller device of the present invention shown in FIG. 11 is a modification of the fifth embodiment shown in FIG. 9 and FIG. This embodiment corresponds to the twelfth embodiment of the present invention.

That is, in the present embodiment, the high-frequency AC voltage output from the main circuit unit when the power to the induction heating roller device is turned on is dispersed over several half cycles to make the toothless. In short, the peak value of the high-frequency AC voltage is constant from the beginning, but by interrupting the conversion operation of the main circuit for several half cycles, the effective value of the high-frequency AC voltage is reduced from when the low-frequency AC power supply AS is turned on. It gradually rises so that an effective soft start is performed. Note that the waveform portion indicated by the dotted line in the figure indicates that the tooth is missing. The left end of the figure is when the power is turned on.

■ A seventh embodiment for implementing the induction heating roller device of the present invention shown in FIG. 12 and FIG. 13 includes a zero-cross detection circuit ZDC and a control unit CC which is a zero-cross control operation circuit. It consists of ZC and drive circuit GDC. Note that the present embodiment corresponds to the eleventh embodiment of the present invention. The zero-crossing detection circuit ZDC is a circuit for detecting the zero-crossing of the low-frequency AC voltage, and its detection output is control-input to the control unit CC.

Zero-cross control operation circuit ZC includes an oscillation circuit and a zero-cross control circuit. The oscillation circuit generates an oscillation signal equal to the frequency of the high-frequency AC voltage output from the main circuit unit MC. The zero-crossing control circuit receives the external signal and outputs the detection output of the zero-crossing detecting means ZDC, that is, the zero-crossing. It operates in synchronization with the generation of the loss detection signal to control-input the oscillation signal of the oscillator oSC to the drive signal generation circuit GtC.

In the high-frequency power supply HFS, the high-frequency conversion circuit I NV of the main circuit unit MC inputs a non-smooth DC voltage generated from the rectified DC power supply circuit RDC to generate a high-frequency AC voltage.

Next, the circuit operation in the present embodiment will be described with reference to FIG. FIG. 13 (a) is a low-frequency AC voltage Vin of a sine wave, and at the zero-cross phase, the zero-cross detection means Z DC detects this and generates a zero-cross detection signal SG1 shown in FIG. 13 (b). I do. The zero-crossing detection signal SG1 is control-input to the zero-crossing control operation circuit ZC.

On the other hand, when an external signal SG2 for commanding power-on shown in FIG. 13 (c) arrives from the external signal source SS, the control circuit ZC operates synchronously when the zero-cross detection signal SG1 is generated. As a result, a control signal SG3 shown in FIG. 13 (d) is generated. The high-frequency power supply HF starts the high-frequency generation operation by the control signal SG3.

Then, a high-frequency AC voltage Vhf shown in FIG. 13 (e) is generated from the output terminal of the high-frequency power supply HFS. Since this high-frequency AC voltage is generated from the initial phase of the low-frequency AC voltage, no overcurrent occurs when the power is turned on.

An eighth embodiment for implementing the induction heating roller device of the present invention shown in FIGS. 14 to 16 is a configuration in which the heating region of the heating roller is synchronized with a zero cross in addition to the configuration of the first embodiment. It is provided with a configuration for switching. This embodiment corresponds to the second to fourth embodiments of the present invention.

To realize the above configuration, control to control high frequency AC voltage applied to multiple induction coils IC1, IC2, IC3, induction coil selection device IS, multiple induction coils IC1, IC2, IC3 It has a unit CC and a plurality of external signal sources SS 1 and SS 2.

Multiple induction coils IC1, IC2, IC3 heat the heating roller HR They are distributed in accordance with the area. That is, the induction coils IC1 and IC3 correspond to the end region of the heating roller HR, and the induction coil IC2 corresponds to the center region. Each of the induction coils IC1, IC2, and IC3 is connected in parallel to a high frequency power supply HFS so that it can be individually energized, that is, excited or excited. .

The induction coil selector IS is inserted between each of the induction coils IC1, IC2, IC3 and the high-frequency power supply HFS. Then, a capacitor is connected in series, parallel or series-parallel to the inductance of the induction coil to form resonance circuits RC1, RC2, RC3 corresponding to each of the induction coils IC1, IC2, IC3. I have. The resonance frequencies of the resonance circuits RC 1 and RC 3 formed in the induction coil IC 2 corresponding to the central region of the heating roller HR and the induction coils IC 1 and IC 3 corresponding to the both end regions are different. It is set as follows. For example, the resonance frequency of the resonance circuit RC2 for the induction coil IC2 in the center region is f1, and the resonance frequency of the resonance circuits RC1 and RC3 for the induction coil IC1 and IC3 in the end region is f2. The relationship is f 1 ≠ f 2. '

The control unit CC includes a control operation circuit CO and a drive circuit GDC. The control operation circuit CO includes a controllable oscillator, a heating area switching operation control unit, and a power switching operation control unit. The oscillating frequency of the controllable oscillator is variable by the control of the heating area switching operation control unit. The heating area switching operation control unit controls the controllable oscillator when a first external signal and a zero-cross detection signal coming from a first external signal source SS 1 described later are synchronously controlled, thereby controlling the high-frequency AC. Acts to switch the frequency of the voltage. The power switching operation control unit includes a PWM control signal generation circuit PSG and a PWM switching circuit SC in the first embodiment shown in FIG. 1, and includes a second external signal source SS2 which will be described later. The high-frequency AC voltage is applied to the heating roller HR by PWM control in response to the external signal of It acts to switch high frequency AC power.

One of the plurality of external signal sources SS 1 and SS 2, that is, the first external signal source SS 1 generates an external signal for switching the heating area, and the other, that is, the second external signal source SS 2 switches the high frequency power switching. Generate an external signal for

Next, with reference to FIG. 16, mainly the heating region switching operation in this embodiment will be described.

For the low-frequency AC voltage Vin shown in FIG. 16 (a), the zero-crossing detection circuit Z DC sends out the zero-crossing detection signal SG1 as shown in FIG. 16 (b).

On the other hand, when the first external signal SG2 for selecting the heating area, which is the polarity that swings from the first external signal source SS1 to the upper side of FIG. When synchronization with the detection signal SG 1 is established, the zero-crossing control operation circuit ZC generates the setting signal SG 3 of the frequency f 2 shown in FIG. 16 (d). As a result, the zero-crossing control operation circuit ZC controls an oscillator incorporated therein to generate an oscillation signal of frequency f2. The drive signal generation circuit GDC generates a drive signal of frequency f2 and drives the high-frequency conversion circuit I NV, so that a high-frequency AC voltage Vhf2 of frequency f2 is generated as shown in FIG. 16 (e). .

Since the resonance circuits RC1 and RC3 resonate with the high-frequency AC voltage Vhf2 having the frequency f2, the induction coil selection device IS selectively applies the high-frequency voltage to the induction coils IC1 and IC3 corresponding to the end regions. It is applied and excited. On the other hand, the resonance circuit RC 2 corresponding to the central region does not resonate with the high-frequency AC voltage, and is not substantially energized, that is, not excited or excited. Next, when the first external signal SG 2 for selecting the heating area, which instructs to turn on the center, arrives from the first external signal source SS 1 with the polarity swinging to the lower side of FIG. 16 (c), When synchronization with the zero-crossing detection signal is established, the zero-crossing control operation circuit ZC sets the frequency f1 setting signal SG shown in FIG. 16 (d). 3 Generate one. As a result, the zero-crossing control operation circuit ZC controls an oscillator incorporated therein to generate an oscillation signal of frequency f1. The drive signal generation circuit GDC generates a drive signal of frequency f1 and drives the high-frequency conversion circuit INV, so that the high-frequency exchange voltage Vhfl of frequency f1 is generated as shown in FIG. 16 (e). I do.

Since the resonance circuit R C2 resonates with the high-frequency AC voltage Vhfl having the frequency f 1, the induction coil selection device IS selectively applies a high-frequency voltage to the induction coil R C2 corresponding to the central region and excites it. On the other hand, since the resonance circuits I C1 and I C3 corresponding to the end regions do not resonate with the high-frequency AC voltage, they are not substantially energized, that is, excited or excited.

Next, when the second external signal arrives from the second external signal source SS2, the same operation as in the first embodiment shown in FIG. 1 to FIG. 5 is performed, and the heating roller is turned on. Is switched.

The induction heating roller device of the present invention shown in FIG. 17 to FIG. 19 has the configuration of the main first embodiment of the present invention, and the control unit of the high-frequency power supply HF S has an analog Control circuit Equipped with ANC. This embodiment corresponds to the tenth embodiment of the present invention.

The high frequency power supply HFS includes a digital control circuit DIC and a drive signal generation circuit GDC in addition to the analog control circuit ANC.

As shown in FIG. 19, the analog control circuit AN C is mainly composed of a phase-locked loop circuit, which feeds back a high-frequency AC output and controls the frequency in a negative feedback manner to obtain a high-frequency conversion efficiency. Is maintained at a predetermined value. The phase-locked loop circuit consists of a phase difference comparator PC, amplifier A, low-pass filter LPF, and oscillator VCO. The phase difference comparator PC compares the voltage and current of the high-frequency AC output of the main circuit unit MC and outputs the phase difference signal. Amplifier A amplifies the phase difference signal. Low-pass filter LP F passes the low frequency component of the phase difference signal. The oscillator VCO controls the oscillation frequency based on the phase difference signal that has passed through the low-pass filter LPF so that the phase difference signal becomes smaller.

The digital control circuit DIC is mainly composed of a PWM control circuit, and maintains a high-frequency output power by controlling a high-frequency AC voltage to be constant. The PWM control circuit includes a PWM control signal generation circuit PSG and a PWM switching circuit SC, and has many parts similar to the configuration in the first embodiment shown in FIG. It is configured to detect voltage and current and feed back those detected values to perform negative feedback control by PWM control. Also, the PWM control circuit may switch the high-frequency AC voltage by the PWM control according to the external signal coming from the external signal source SS similarly to the first embodiment shown in FIG. 1 separately from the above. It is also configured to be able to.

The power factor improving capacitor C5 is connected in parallel with the induction coil IC at a position close to the induction coil IC.

Thus, in the present embodiment, the analog control circuit A NC can make the phase difference between the voltage and the current of the high-frequency AC output constant, so that the high-frequency conversion efficiency in the main circuit section is made constant.

Further, the digital control circuit DIC can stabilize the high-frequency AC power.

In a tenth embodiment for implementing the induction heating roller device of the present invention shown in FIG. 20 to FIG. 22, the induction heating roller device includes a high-frequency power supply device HFS, an induction coil IC, and a heating roller HR. In addition to this, a high-frequency power supply / discharge detection means ODC is provided, and the control unit CC of the high-frequency power supply HFS includes an analog control circuit ANC and a protection judgment circuit PJC. This embodiment corresponds to the seventh embodiment of the present invention. High frequency AC output detection means ODC is high frequency AC voltage and high frequency AC 4 007840

46

The currents are respectively detected, and their detection signals are input to the phase difference comparison circuit PC of the analog control circuit ANC.

The analog control circuit ANC of the control unit CC has the same configuration as that of the ninth embodiment shown in FIG. 18 to FIG. Then, the part corresponding to the amplifier A is replaced by the protection determination circuit PJC. As shown in FIG. 21, the protection determination circuit PJC forms a window comparator by connecting a pair of operational amplifiers A 1 and A 2 in parallel in an anti-phase relationship. That is, the positive-phase input terminal of the operational amplifier A1 and the negative-phase input terminal of the operational amplifier A2 are connected to the output terminal of the phase difference comparator PC, and the output terminals of the operational amplifiers A1 and A2 are Both are connected to the control input terminal of the voltage controlled oscillator VCO. The negative-phase input terminal of the operational amplifier A1 is connected to the reference voltage source V1, and the positive-phase input terminal of the operational amplifier A2 is connected to the reference voltage source V2. The reference voltage source V1 outputs the reference voltage V1. The reference voltage source V2 outputs a reference voltage V2 higher than the reference voltage V1.

Next, the circuit operation in the present embodiment will be described with reference to FIG. FIG. 22 (a) is a graph showing the protection characteristic against the phase difference signal voltage, the horizontal axis represents the phase difference signal voltage output from the phase comparator PC, and the vertical axis represents the frequency from the high-frequency power supply HFS. The output high-frequency AC voltage is shown. FIG. 22 (b) is a graph showing the protection range for the phase difference signal voltage, and the horizontal axis is aligned with the phase difference signal voltage of FIG. 22 (a). The vertical axis indicates the judgment output.

As can be understood from the figure, when the input phase difference signal voltage is between the reference voltages V 1 and V 2, the protection judgment circuit PJC judges that the phase difference signal is normal and operates as an amplifier, but is lower than the reference voltage V 1. At this time, and when the voltage is higher than the reference voltage V 2, it is determined to be abnormal, and the protection operation is performed by cutting off the phase difference signal voltage. As a result, the high-frequency power supply stops generating the high-frequency AC voltage, thereby ensuring safety. A first embodiment for implementing the induction heating roller apparatus of the present invention shown in FIG. 23 is a rectified DC power supply circuit in a main circuit part MC of a high-frequency power supply HFS. In addition, a capacitor C6 having a capacitance such that the power factor of the circuit becomes 0.8 or more is connected. This embodiment corresponds to the eighth embodiment of the present invention.

In this embodiment, the “power factor of the circuit” refers to a power factor when the entire induction heating roller device is viewed from the low-frequency AC power supply AS side.

In the present embodiment, high frequency noise is generated by the inverter, which is the high frequency conversion circuit INV, in the main circuit section MC of the high frequency power supply HFS, which generates high frequency noise. To be absorbed. In addition, the provision of the capacitor C6 increases the power factor of the induction heating roller device as a whole, thereby suppressing a wasteful increase in wiring capacity and reducing the load fluctuation of high-frequency AC power. .

A second embodiment for implementing the induction heating roller device of the present invention shown in FIG. 24 is a rectified DC power supply means in a main circuit portion MC of a high-frequency power supply device HFS. A capacitor C6 with a capacitance such that the power factor of the capacitor becomes 0.8 or more is connected, and a multi-yoke L2 is connected between the rectified DC power supply RDC and the capacitor C6. Inserted in series. This embodiment corresponds to the eighth embodiment of the present invention.

Thus, in the present embodiment, the outflow of noise can be more effectively suppressed than in the first embodiment shown in FIG. Even if the capacitance of the capacitor C 6 is reduced so that the power factor of the circuit becomes 0.8 or less, noise reduction equivalent to that in FIG. 23 can be achieved.

25 for implementing the induction heating roller device of the present invention shown in FIG.

13 is a high frequency conversion circuit in the main circuit section MC of the high frequency power supply device HFS. 1 NV 1 and INV 2 are connected in parallel via distributor D and combiner S. This embodiment corresponds to the ninth embodiment of the present invention.

The distributor D integrates the control input terminals of the pair of high-frequency conversion circuits INV1 and INV2. On the other hand, the synthesizer S integrates the output terminals of the high-frequency AC voltages of the pair of high-frequency conversion circuits INV1 and INV2. In this embodiment, the control unit CC has the same configuration as that of the first embodiment shown in FIG. 20 and FIG. However, in this embodiment, the configuration other than using a plurality of high-frequency conversion circuits INV in the main circuit unit MC of the high-frequency power supply device HFS is the same as the configuration in each of the first to 12th embodiments as desired. be able to.

In one embodiment for implementing the fixing device of the present invention shown in FIG. 26, 21 is an induction heating roller device, 22 is a pressure roller, 23 is a recording medium,

24 is a toner, 25 is a gantry, and IC is an induction coil.

As the induction heating roller device 21, each of the configurations shown in FIG. 1 to FIG. 25 can be used.

The pressure roller 22 is disposed in pressure contact with the heating roller HR of the induction heating roller device 21, and conveys the recording medium 23 while narrowing the pressure therebetween.

An image is formed on the recording medium 23 by attaching the toner 24 to the surface thereof.

The gantry 25 mounts the above components (excluding the recording medium 23) in a predetermined positional relationship.

Then, in the fixing device, the recording medium 23 onto which the toner 24 has adhered to form an image is inserted between the heating roller HR and the pressure roller 22 of the induction heating roller device 21. While being conveyed, the toner 24 is heated and melted by the heat of the heating roller HR, and is thermally fixed.

FIG. 27 shows an embodiment for implementing the image forming apparatus of the present invention. In this copying machine, 31 is a reading device, 32 is an image forming means, 33 is a fixing device, and 34 is an image forming device case.

The reading device 31 optically reads a base paper to form an image signal. The image forming means 32 forms an electrostatic latent image on the photosensitive drum 32a based on the image signal, attaches toner to the electrostatic latent image to form a reverse image, and records this on paper or the like. The image is transferred to a medium to form an image.

The fixing device 33 has a structure shown in FIG. 26, and heat-fuses and fixes the toner attached to the recording medium.

The image forming apparatus case 34 houses the above devices and means 31 to 33, and also includes a transport device, a power supply device, and a control device. Industrial applicability

INDUSTRIAL APPLICABILITY The induction heating roller device of the present invention heats the heating roller by induction heating, so that rapid heating is easy. Therefore, the induction heating roller device is useful for fixing in an image forming apparatus such as a copying machine, for example. The temperature of the heating roller can be changed as desired.

Claims

50 Scope of Claim

1. An induction coil, a heating roller that generates heat by a secondary current flowing by being magnetically coupled to the induction coil, and a high-frequency power supply that energizes the induction coil;

The high-frequency power supply device converts a low-frequency AC voltage into a high-frequency AC voltage and outputs the high-frequency AC voltage, and controls the main circuit unit in response to an external signal to sufficiently increase the frequency of the low-frequency AC voltage; A control unit 0 capable of outputting a high-frequency AC voltage controlled by PWM at a frequency sufficiently lower than the frequency of the AC voltage;

An induction heating roller device, characterized in that:

2. The induction heating roller according to claim 1, wherein the control unit controls the high-frequency power supplied to the induction coil to a desired value in accordance with an operation. apparatus.

L5 3. A plurality of the induction coils are disposed corresponding to a plurality of heating areas of the heating roller;

An induction coil selecting device for selecting an induction coil corresponding to a desired heating area among the plurality of induction coils by means other than the PWM control in order to switch the plurality of heating areas of the heating roller;

The induction heating roller device according to claim 1, wherein:

4. The induction coil selector is configured to select a desired induction coil from a plurality of induction coils in response to a frequency of a high frequency voltage output from the high frequency power supply;

In the high-frequency power supply device, the control unit changes the frequency of the high-frequency voltage output from the main circuit unit in response to an external signal so that the induction coil selection device responds;

4. The induction heating roller device according to claim 3, wherein:

5. a zero-cross detection circuit that detects a zero-cross of the low-frequency AC voltage and generates a zero-cross signal;

An induction coil selection control circuit for controlling an induction coil corresponding to a desired heating area among a plurality of induction coils in synchronization with a zero cross signal generated from a zero cross detection circuit based on an external signal; 4. The induction heating roller device according to claim 3, wherein:

6. The high-frequency power supply device includes a PWM control signal generating circuit that receives an external signal and generates a PWM control signal, and a high-frequency AC voltage generated from the main circuit unit by controlling the main circuit unit. An oscillator that determines the frequency, and a PWM switching circuit that is interposed between the oscillator and the main circuit and that switches the output of the oscillation circuit according to the PWM control signal generated by the PWM control signal generation circuit The induction heating roller device according to claim 1, further comprising:

7. The induction heating roller device according to claim 1, wherein the high-frequency power supply device obtains a maximum value of a high-frequency AC voltage output therefrom by PWM control with a duty ratio of less than 100%. .

8. The high-frequency power supply device, wherein the control unit is configured to stop the operation of generating the high-frequency AC voltage when the difference between the phase of the high-frequency AC voltage and the phase of the high-frequency AC current exceeds a predetermined value. There;

2. The induction heating roller device according to claim 1, wherein:

9. The high-frequency power supply device includes a rectified DC power supply circuit that converts a low-frequency AC voltage into a DC voltage, a high-frequency conversion circuit that converts a DC voltage from the rectified DC power supply circuit into a high-frequency AC voltage, And a parallel connection to at least one of the front and rear stages of the rectified DC power supply circuit, so that the induction heating roller device as a whole can maintain a power factor of 0.8 or more when viewed from the low-frequency AC power supply. 2. The induction heating roller device according to claim 1, further comprising a condenser having the same.

10. The high-frequency power supply device has a rectified DC power supply means whose main circuit section converts a low-frequency AC voltage into a DC voltage, and is connected in parallel and controlled collectively. 2. The induction heating roller device according to claim 1, further comprising a plurality of high-frequency converters that convert a DC voltage from the unit into a high-frequency AC voltage and output the collective output.

11. The high-frequency power supply device, wherein the control circuit includes an analog control circuit for controlling the frequency so that the conversion efficiency of the high-frequency AC voltage output from the main circuit unit is maintained at a predetermined level. Item 1. The induction heating roller device according to item 1.

12. The induction heating roller device according to claim 10, wherein the analog control circuit is mainly constituted by a phase locked loop (PLL) circuit.

13. A zero-cross detection circuit that detects a zero-cross of the low-frequency AC voltage and generates a zero-cross signal;

A control unit of the high-frequency power supply device, which switches an output of the high-frequency AC voltage from the main circuit from an off state to an on state in synchronization with a zero-cross signal according to an external signal;

The induction heating roller device according to claim 1, wherein:

14. The control unit of the high-frequency power supply device is characterized in that when the low-frequency AC power is turned on, the main circuit is soft-start-controlled when the on-duty rises due to the PWM control. The induction heating roller device according to claim 1.

15. A fixing device main body having a pressure roller;

A heating roller is provided opposite to the pressure roller of the fixing device body in a pressure-contact relationship, and is arranged so that the toner image is fixed while the recording medium on which the toner image is formed is conveyed between both rollers. The induction heating roller device according to claim 1, and; 53

A fixing device comprising:

16. An image forming apparatus provided with an image forming means for forming a toner image on a recording medium, and a fixing device provided on the image forming apparatus main body to fix the toner image on the recording medium;

The fixing device has a configuration according to claim 1;

An image forming apparatus comprising: