JP6740725B2 - Heating device and image forming device - Google Patents

Description

The present invention relates to a heating device and an image forming apparatus.

2. Description of the Related Art In a heating device, high-frequency dielectric heating is used in which an object to be heated is irradiated with a high-frequency AC electric field to heat the object to be heated in a non-contact state. Such a heating device is used in various devices and systems, for example, it is used as a drying device for drying ink on recording paper in an image forming apparatus such as an inkjet printer.

For example, a device for dielectrically heating an object to be thawed such as frozen food, in which a plurality of electrodes are arranged in a thaw chamber that also serves as an electromagnetic shield, and conductors having different inductances between the three high-frequency power generation circuits and the electrodes. There is disclosed a configuration in which a plurality of impedance matching circuits including is installed (Patent Document 1).

In order to improve the heating efficiency in a heating device using high frequency induction heating, it is necessary to efficiently and safely increase the current (applied current) applied to the object to be heated by the AC electric field. The increase in the applied current is simply achieved by increasing the power supply voltage supplied to the electrode pair, but the increase in the power supply voltage may cause problems such as an increase in power consumption and heat generation in the transmission path.

A heating device using high-frequency dielectric heating usually includes a matching unit that matches an output impedance of a power source side and an input impedance of a load side (a heating unit side including an electrode pair, an object to be heated, etc.). Since the matching unit is configured to include various electronic devices, it may malfunction due to the influence of the AC electric field if it is installed near the electrode pair. Therefore, the matching section needs to be installed at a place apart from the electrode pair to some extent, and in many cases, the transmission path connecting the matching section and the electrode pair must be long. Since a long transmission line causes power loss, heat generation, etc., it is often impossible to simply increase the power supply voltage.

The present invention has been made in view of the above, and an object thereof is to safely and efficiently improve heating efficiency.

In order to solve the above-mentioned problems and achieve the object, the present invention provides a power source for generating an AC voltage and an AC electric field generated from an electrode pair to which the AC voltage is applied, by irradiating the object to be heated. A heating unit that heats an object to be heated, and a matching unit that is connected to the electrode pair through a transmission path and that matches the output impedance of the power source side and the input impedance of the heating unit side, the heating unit , the AC field by viewing including the current increase device increases the current applied to the object to be heated, the current increase element, said a inductor connected to the transmission line, the power supply when the inductor is not connected In the heating device, the operating frequency of the power source when the inductor is connected is closer to the parallel resonance frequency generated between the electrode pair and the transmission line than the operating frequency of .

According to the present invention, it is possible to improve heating efficiency safely and efficiently.

FIG. 1 is a diagram illustrating a functional configuration of the heating device according to the first embodiment. FIG. 2 is a diagram illustrating a hardware configuration of a heating device according to a comparative example. FIG. 3 is a diagram illustrating an equivalent circuit of the heating device according to the comparative example. FIG. 4 is a diagram illustrating the mutual relationship between the magnitude and phase of the current in the equivalent circuit shown in FIG. FIG. 5: is a figure which illustrates the ideal mutual relationship in the mutual relationship shown in FIG. FIG. 6 is a diagram illustrating a hardware configuration of the heating device according to the first embodiment. FIG. 7: is a figure which illustrates the equivalent circuit of the heating apparatus which concerns on 1st Embodiment. FIG. 8 is a diagram illustrating frequency characteristics of input impedance according to the first embodiment. FIG. 9: is a figure which illustrates the hardware constitutions of the heating apparatus which concerns on 2nd Embodiment. FIG. 10 is a diagram illustrating an equivalent circuit of the heating device according to the second embodiment. FIG. 11: is a figure which illustrates the hardware constitutions of the heating apparatus which concerns on 3rd Embodiment. FIG. 12 is a diagram illustrating an equivalent circuit of the heating device according to the third embodiment.

(First embodiment)
FIG. 1 is a diagram illustrating a functional configuration of a heating device 1 according to the first embodiment. The heating device 1 includes a power supply 11, a heating unit 12, and a matching unit 13.

The power supply 11 outputs a high frequency AC voltage. The frequency of the AC voltage may be any value that can realize known high-frequency dielectric heating and should be appropriately set according to the use environment, but can be a value of, for example, about 3 MHz to 300 MHz.

The heating unit 12 heats the object to be heated 20 by high frequency dielectric heating. The heating unit 12 includes an electrode pair 22 and a current increasing element 26. The electrode pair 22 generates a high frequency AC electric field M when an AC voltage supplied from the power source 11 is applied. Usually, a plurality of electrode pairs 22 are provided, and each electrode pair 22 generates an alternating electric field M. When the object 20 to be heated is irradiated with the AC electric field M, an applied current is generated in the object 20 to be heated, and the object 20 to be heated is heated. The current increasing element 26 is an element that acts to increase the applied current generated in the object to be heated 20.

The matching unit 13 is connected to the power supply 11 and the heating unit 12 (electrode pair 22), and matches the impedance (output impedance) on the power supply 11 side and the impedance (input impedance) on the heating unit 12 side. The matching unit 13 is configured by using an electronic device that controls the two so that they have the same value based on the difference between the output impedance and the input impedance, for example.

Since the heating device 1 according to the present embodiment includes the current increasing element 26 that acts to increase the applied current generated in the object to be heated 20, it depends only on the increase in the output voltage of the power supply 11. Therefore, the heating efficiency of the article to be heated 20 can be improved.

Here, with reference to the heating device 501 according to the comparative example shown in FIGS. 2 and 3, conditions and the like necessary for increasing the applied current generated in the object to be heated 20 will be described. FIG. 2 is a diagram illustrating a hardware configuration of the heating device 501 according to the comparative example. The heating device 501 according to the comparative example includes a power supply 11, a heating unit 512, and a matching unit 13.

The heating unit 512 includes a housing 21, a plurality of electrode pairs 22, a power supply wiring 23, and a ground wiring 24. The electrode pair 22, the power supply wiring 23, and the ground wiring 24 are arranged in the housing 21 having a magnetic shielding property. Each electrode pair 22 is composed of a set of a positive electrode 22A and a negative electrode 22B, and is connected to the matching section 13 via a power supply wiring 23 and is connected to GND via a ground wiring 24. Each electrode pair 22 generates an AC electric field by being applied with an AC voltage from the power supply 11 via the power supply wiring 23. The object to be heated 20 (liquid such as ink on the recording paper) is heated by being irradiated with an AC electric field generated from each electrode pair 22.

The matching unit 13 includes a housing 31, a directional coupler 32, a variable capacitance 33, an internal inductor 34, and a microcontroller 35. The directional coupler 32, the variable capacitor 33, and the internal inductor 34 are arranged in the housing 31 having magnetic shielding properties. The directional coupler 32 is connected to the power source 11 and the variable capacitor 33, and outputs a traveling wave and a reflected wave. The variable capacitance 33 is connected to the directional coupler 32 and the internal inductor 34, and changes the capacitance according to a control signal from the microcontroller 35. The microcontroller 35 changes the capacitance of the variable capacitor 34 based on the traveling wave and the reflected wave so that the reflected wave becomes 0, for example.

As described above, in order to prevent the AC electric field generated from the electrode pair 22 from causing the malfunction of the matching section 13, the spacing between the heating section 512 and the matching section 13 is set to be large, or the heating section 512 and the matching section 13 are separated. It is necessary to cover the components with the housings 21 and 31. Therefore, in many cases, the power supply wiring 23 has to be long. The longer the power supply wiring 23 is, the larger the power loss is, and the heating efficiency of the object to be heated 20 is deteriorated. Further, if the output voltage of the power supply 11 is increased to compensate for the power loss due to the power supply wiring 23, the power cost may increase or the heat generation of the power supply wiring 23 may become excessive.

FIG. 3 is a diagram illustrating an equivalent circuit of the heating device 501 according to the comparative example. Capacitances C0 and C1 indicate two kinds of capacitances that the variable capacitance 33 has. The inductance L0 represents the inductance of the internal inductor 34. The resistance R1 indicates the resistance of the power supply wiring 23. The capacitance C2 represents the parasitic capacitance of the power supply line 23 with respect to GND. The inductance L1 represents the inductance of the electrode pair 22 itself. The resistance R2 indicates the resistance of the electrode pair 22. The capacitance C3 represents the parasitic capacitance of the electrode pair 22. The resistance R3 and the capacity C4 indicate the resistance and the capacity of the object to be heated 20. The object to be heated 20, which is mainly a dielectric, is expressed as a series component of the resistance R3 and the capacitance C4. Impedance Z1 represents the output impedance on the power supply 11 side. Impedance Z2 indicates the input impedance on the load side.

The current I1 indicates the current flowing through the capacitor C2. The current I2 indicates the current flowing through the resistor R1. The current I3 indicates the current flowing through the inductance L1. The current I4 indicates the current flowing through the capacitor C3. The current I5 indicates the current flowing through the capacitor C4. The current I5 is an applied current applied to the object to be heated 20 by the AC electric field generated by the electrode pair 22.

In order to improve the heating efficiency of the object to be heated 20, the current I5 must be increased. In order to increase the current I5, the current I3 must be increased. In order to increase the current I3, it is necessary to increase the current I1 as much as possible and the current I2 as small as possible. The conditions of the currents I1 and I2 for increasing the current I3 will be described below.

FIG. 4 is a diagram illustrating the mutual relationship between the magnitudes and phases of the currents I1, I2, I3 in the equivalent circuit shown in FIG. FIG. 5: is a figure which illustrates the ideal mutual relationship in the mutual relationship shown in FIG. Here, if the currents I1, I2, I3 are expressed by the following equations (1), (2), (3), the following equation (4) is derived.

I1=|I1|exp(jθ1) (1)
I2=|I2|exp(jθ2) (2)
I3=|I3|exp(jθ3) (3)
^{| I3 | 2 = | I2-} I1 | 2 = | I2 | 2 + | I1 | 2 -2 | I1 || I2 | cos (θ2-θ1) ... (4)

From the equation (4), in order to increase |I3|, it is ideal that ∠I2-∠I1=θ2-θ1=180° and that |I1| is maximized. Further, it is ideal that ∠V2−∠I2=90° and the capacitance C2 is as large as possible. Further, it is ideal that ∠Z2≈90° (L property), that is, the absolute value |Z2| of the input impedance is made as large as possible. By increasing |Z2|, |I2| can be decreased. Further, when |I3| is constant, |I5| becomes larger as |I4| becomes smaller. Therefore, it is ideal to make |I4| as small as possible, that is, make the capacitance C3 as small as possible.

FIG. 6 is a diagram illustrating a hardware configuration of the heating device 1 according to the first embodiment. The heating device 1 includes a power supply 11, a heating unit 12, and a matching unit 13. The heating unit 12 according to the present embodiment includes the additional inductor 41 as the current increasing element 26, and the positive electrode 22A and the negative electrode 22B arranged in a staggered manner. The additional inductor 41 is an example of the current increasing element 26 that acts to reduce the current I2. The positive electrodes 22A and the negative electrodes 22B that are arranged in a staggered pattern are an example of the current increasing element 26 that acts to reduce the current I4.

The heating unit 12 includes a housing 21 (first housing), a plurality of electrode pairs 22, a power supply wiring 23 (transmission path), a ground wiring 24, and an additional inductor 41. The electrode pair 22, the power supply wiring 23, the ground wiring 24, and the additional inductor 41 are arranged in the housing 21 having magnetic shielding properties.

Each electrode pair 22 is composed of a set of a positive electrode 22A and a negative electrode 22B. Each electrode pair 22 is connected to the matching unit 13 via the power supply wiring 23 and the additional inductor 41, and is connected to GND via the ground wiring 24. Each electrode pair 22 generates an AC electric field M when an AC voltage supplied from the power supply 11 is applied via the power supply wiring 23 and the additional inductor 41.

The positive electrode 22A and the negative electrode 22B according to the present embodiment are arranged in a staggered pattern. The object to be heated 20 is heated by being irradiated with the alternating electric field M by passing between the positive electrode 22A and the negative electrode 22B which form a pair. By arranging the positive electrode 22A and the negative electrode 22B in a staggered pattern, the electric capacity becomes smaller than that in the case where they are linearly arranged. That is, the positive electrodes 22A and the negative electrodes 22B arranged in a staggered pattern function as elements (capacitance reducing elements) that reduce the parasitic capacitance of the electrode pair 22.

The additional inductor 41 is an element (impedance increasing element) that acts so as to increase the impedance of the entire heating unit 12 (input impedance Z2). The specific structure of the additional inductor 41 is not particularly limited, but examples thereof include an air-core solenoid type, a solenoid type having a core, and a toroidal type.

The matching unit 13 includes a housing 31 (second housing), a directional coupler 32, a variable capacitance 33, an internal inductor 34, and a microcontroller 35. The directional coupler 32, the variable capacitor 33, and the internal inductor 34 are arranged in the housing 31 having magnetic shielding properties. The directional coupler 32 is connected to the power source 11 and the variable capacitor 33, and outputs a traveling wave and a reflected wave. The variable capacitance 33 is connected to the directional coupler 32 and the internal inductor 34, and changes the capacitance according to a control signal from the microcontroller 35. The internal inductor 34 is connected to the variable capacitor 33 and the power supply wiring 23. The microcontroller 35 includes a microcomputer and the like, and generates and outputs a control signal for changing the variable capacitor 34 based on the traveling wave and the reflected wave from the directional coupler 32. The microcontroller 35 changes the capacitance of the variable capacitance 33 so that the reflected wave becomes 0, for example.

FIG. 7: is a figure which illustrates the equivalent circuit of the heating device 1 which concerns on 1st Embodiment. Capacitances C0 and C1 indicate two kinds of capacitances that the variable capacitance 33 has. The inductance L0 represents the inductance of the internal inductor 34. The resistance R1 indicates the resistance of the power supply wiring 23. The capacitance C2 represents the parasitic capacitance of the power supply line 23 with respect to GND. The inductance LA represents the inductance of the additional inductor 41. The inductance L1 represents the inductance of the electrode pair 22 itself. The resistance R2 indicates the resistance of the electrode pair 22. The capacitance C3 represents the parasitic capacitance of the electrode pair 22. The parasitic capacitance C3 of the electrode pair 22 composed of the positive electrode 22A and the negative electrode 22B arranged in a staggered manner as in the present embodiment is more than the parasitic capacitance of the electrode pair when the positive electrode and the negative electrode are linearly arranged. Get smaller. The resistance R3 and the capacity C4 indicate the resistance and the capacity of the object to be heated 20. The object to be heated 20, which is mainly a dielectric, is expressed as a series component of the resistance R3 and the capacitance C4. Impedance Z1 represents the output impedance on the power supply 11 side. Impedance Z2 indicates the input impedance on the load side.

The current I1 indicates the current flowing through the capacitor C2. The current I2 indicates the current flowing through the resistor R1. The current I3 indicates the current flowing through the inductance L1. The current I4 indicates the current flowing through the capacitor C3. The current I5 indicates the current flowing through the capacitor C4. The current I5 is an applied current applied to the object to be heated 20 by the AC electric field M generated by the electrode pair 22.

A directional coupler 32 is connected between the power source 11 and the variable capacitors C0 and C1. The directional coupler 32 has four ports (power input, power output, reflected wave output, and traveling wave output). The microcontroller 35 controls the variable capacitors C0 and C1 based on the reflected wave and the traveling wave. The microcontroller 35 switches the variable capacitors C0 and C1 so that, for example, the voltage corresponding to the reflected wave becomes as small as possible.

FIG. 8 is a diagram illustrating frequency characteristics of the input impedance Z2 according to the first embodiment. In the figure, the horizontal axis of the graph shows the frequency of the voltage (power) applied to the electrode pair 22. In the same figure, it is shown that the input impedance Z2 becomes minimum at the frequency fs and the input impedance Z2 becomes maximum at the frequency fp. At the frequency fs, series resonance occurs in which a resonance current circulates between the inductance L1 and the capacitors C3 and C4. At the frequency fp, parallel resonance occurs in which the resonance current circulates between the inductance L1 and the capacitors C2, C3 and C4.

In order to reduce the current I2, the input impedance Z2 may be increased. Therefore, the structure of the electrode pair 22, that is, the inductances LA, L1 and the capacitors C2, C3, C4 are set so that the frequency (power supply operating frequency) of the voltage (power) output from the power source 11 and the frequency fp are as close to each other as possible. Just design. When the power supply operating frequency is between the frequency fs and the frequency fp of the input impedance Z2, increasing the value of the inductance LA moves the frequency fp to the lower frequency side. By adjusting the inductance LA (designing the additional inductor 41) based on such characteristics, the frequency fp at which parallel resonance occurs can be brought close to the power supply operating frequency.

As described above, the input impedance Z2 can be increased by adding the additional inductor 41 having the appropriate inductance LA to the heating unit 12 (between the power supply wiring 23 and the electrode pair 22). As a result, the current I2 flowing through the power supply wiring 23 can be reduced and the current I3 can be increased. Thereby, the current I5 can be increased more than when the additional inductor 41 is not provided (the heating device 501 according to the comparative example), and the heating efficiency can be improved safely and efficiently.

Further, the parasitic capacitance C3 of the electrode pair 22 becomes relatively small by using the positive electrodes 22A and the negative electrodes 22B arranged in a zigzag manner as described above. Thereby, the current I4 flowing through the electrode pair 22 can be reduced without reducing the current I3. As a result, the current I5 can be increased as compared with the case where the positive electrode and the negative electrode are linearly arranged, and the heating efficiency can be safely and efficiently improved.

(Second embodiment)
FIG. 9: is a figure which illustrates the hardware constitutions of the heating apparatus 101 which concerns on 2nd Embodiment. FIG. 10 is a diagram illustrating an equivalent circuit of the heating device 101 according to the second embodiment. The heating unit 112 of the heating device 101 according to the present embodiment is obtained by replacing the additional inductor 41 of the heating unit 12 of the heating device 1 according to the first embodiment with a transformer 42. The transformer 42 according to the present embodiment is an example of the current increasing element 26, and the input impedance Z2 is increased as in the case of the additional inductor 41 according to the first embodiment, that is, the power supply wiring 23 (resistor R1). It is an element (impedance increasing element) that acts to reduce the flowing current I2.

The transformer 42 is arranged between the power supply wiring 23 and the electrode pair 22. The turns ratio of the transformer 42 is N1:N2 (primary side:secondary side), the primary side voltage is V1, the primary side current is I2, the secondary side voltage is V2, and the secondary side current is When I20, the relationships of the following formulas (5) and (6) are established between the voltages V1 and V2 and the currents I2 and I20.

(N1/N2)·V2=V1 (5)
(N2/N1)·I20=I2 (6)

Here, if the equivalent circuit constant of the electrode pair 22 and the equivalent circuit constant of the heated object 20 are the same, the power consumed by the electrode pair 22 and the heated object 20 is the same regardless of the winding ratio of the transformer 42. Therefore, the value of the current I20 is constant regardless of the winding ratio. Therefore, from the equation (6), if N1>N2, then I20>I2, and the current I2 flowing through the power supply wiring 23 (resistor R1) becomes small. That is, if N1>N2, the input impedance Z2 when viewed from the primary side of the transformer 42 appears to be as large as (N1/N2) ² times, so that the current I2 flowing through the resistor R1 is narrowed.

According to the present embodiment described above, the current I5 can be increased similarly to the first embodiment, and the heating efficiency can be safely and efficiently improved.

In the first embodiment and the second embodiment, the additional inductor 41 and the transformer 42 are illustrated as the current increasing element 26 that acts to reduce the current I2, and the current I4 acts to reduce the current I4. The positive electrode 22A and the negative electrode 22B arranged in a staggered manner are illustrated as the current increasing elements 26. However, the specific configurations of the current increasing element 26 that acts to reduce the current I2 and the current increasing element 26 that acts to reduce the current I4 are not limited to the above, and well-known or novel configurations may be appropriately used. Can be built by.

(Third Embodiment)
FIG. 11: is a figure which illustrates the hardware constitutions of the heating apparatus 201 which concerns on 3rd Embodiment. FIG. 12 is a diagram illustrating an equivalent circuit of the heating device 201 according to the third embodiment. The heating unit 212 of the heating device 201 according to the present embodiment is obtained by adding the additional condenser 43 to the heating unit 12 of the heating device 1 according to the first embodiment. The additional capacitor 43 according to the present embodiment is an example of the current increasing element 26, is an element (capacity increasing element) that acts to increase the parasitic capacitance of the power supply wiring 23 with respect to GND, and increases the current I1 flowing through the capacitor C2. It acts to make it larger.

One end of the additional capacitor 43 is connected to the connection portion between the power supply wiring 23 and the additional inductor 41 (the electrode pair 22 when the additional inductor 41 is not provided). As shown in FIG. 12, the capacitance C5 of the additional capacitor 43 is arranged so as to be parallel to the capacitance C2 of the power supply wiring 23. Thereby, the current I1 flowing through the capacitor C2 can be increased.

According to the present embodiment described above, the current I5 can be further increased as compared with the case of the first embodiment, and the heating efficiency can be improved.

Although the additional capacitor 43 is illustrated as the current increasing element 26 that acts to increase the current I1 in the third embodiment, the specific configuration of the current increasing element 26 that acts to increase the current I1. Is not limited to the above, and can be constructed by appropriately using a known or novel configuration.

The heating devices 1, 101, 201 and the modifications thereof according to the above-described embodiments are used in various devices and systems, and various substances can be the objects to be heated 20. For example, the heating devices 1, 101, 201 may be mounted on an image forming apparatus such as an inkjet printer, and used as a drying device that heats and dries liquids such as ink and coating agent adhered on recording paper. The object to be heated 20 is not limited to the sheet shape, and the heating device can be applied to, for example, a 3D printer having a three-dimensional object as the object to be heated 20.

Although the embodiments of the present invention have been described above, the above embodiments are presented as examples and are not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the spirit of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

1, 101, 201, 501 Heating device 11 Power source 12, 112, 212, 512 Heating part 13 Matching part 20 Heated object 21 (First) case 22 Electrode pair 23 Power supply wiring 24 Ground wiring 22A Positive electrode 22B Negative electrode 26 Current Increasing Element 31 (Second) Housing 32 Directional Coupler 33 Variable Capacitance 34 Internal Inductor 35 Microcontroller 41 Additional Inductor 42 Transformer 43 Additional Capacitor M AC Electric Field

Japanese Patent No. 4177963

Claims (9)

A power supply that generates an alternating voltage,
A heating unit for heating the object to be heated by irradiating the object to be heated with an AC electric field generated from the electrode pair to which the AC voltage is applied,
A matching unit, which is connected to the electrode pair via a transmission line, and matches the output impedance of the power supply side and the input impedance of the heating unit side,
Equipped with
The heating unit is viewed including the current increase device increases the current applied to the object to be heated by the AC electric field,
The current increasing element is an inductor connected to the transmission line,
The operating frequency of the power supply when the inductor is connected to the operating frequency of the power supply when the inductor is not connected has a value close to the parallel resonance frequency generated between the electrode pair and the transmission path.
Heating device. The current increasing element is a transformer connected to the transmission line,
The heating device according to claim 1 . The current increasing element includes a capacitance reducing element that reduces a parasitic capacitance of the electrode pair,
Heating apparatus according to claim 1 or 2. The capacitance reducing element constitutes the electrode pair, and includes positive electrodes and negative electrodes arranged in a staggered pattern,
The object to be heated passes between a pair of the positive electrode and the negative electrode,
The heating device according to claim 3 . The current increasing element includes a capacitance increasing element that increases a parasitic capacitance of the transmission path with respect to GND.
Heating apparatus according to any one of claims 1-4. The heating unit includes a first housing that houses the electrode pair and the transmission path and has a magnetic shielding property.
Heating apparatus according to any one of claims 1-5. The current increasing element is disposed in the first housing,
The heating device according to claim 6 . The matching unit includes a variable capacitor, an internal inductor connected between the variable capacitor and the transmission line, a directional coupling connected between the power source and the variable capacitor, and outputs a traveling wave and a reflected wave. And a control element that changes the variable capacitance based on the traveling wave and the reflected wave, a second casing that houses at least the variable capacitance, the internal inductor, and the directional coupler and has a magnetic shielding property. Including the body and
Heating apparatus according to any one of claims 1-7. The heating device according to any one of claims 1-8, heating the liquid deposited on the medium,
Image forming apparatus.

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