This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application No. 2015-098181 filed on May 13, 2015, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
1. Field of the Invention
The present invention relates to a high frequency dielectric heater.
2. Description of the Related Art
Some commercial inkjet printers, in particular, inkjet printers printing images on large-size posters or conducting gravure printing, include driers to dry the ink applied on recording media.
This type of drier employs methods using, for example, heated wind, a heat drum, infra red, or high frequency induced electricity. Of these, high frequency dielectric heating has less damage on a heated material, typically, paper than other drying methods.
According to the present disclosure, provided is an improved high frequency dielectric heater which includes a high frequency power supply configured to supply a power having a high frequency to heat a subject, electrodes including a positive electrode and a negative electrode, each electrode being disposed in such a manner that the longitudinal direction of each electrode crosses with the transfer direction of the subject and having a surface at least part of which is parallel to the subject; and a transfer device to transfer the subject.
Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same become better understood from the detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like corresponding parts throughout and wherein
The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
In describing example embodiments shown in the drawings, specific terminology is employed for the sake of clarity. However, the present disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.
The high frequency dielectric heater relating to the present disclosure is described with reference to accompanying drawings
First, the principle of high frequency dielectric heating is described.
As illustrated in
The amount of this heat generation P is known to be represented by the following relation 1.
In addition, the value of tanδ of the angle δ illustrated in
In this equation, j represents an imaginary number ((−1)1/2) and ω represents an angle rate of high frequency power.
The high frequency dielectric power source 11 has a high frequency oscillator to supply a high frequency power of several MHz or greater.
The matching box 12 matches the impedance between the output terminal of the high frequency power source 11 and the input terminal of the drier 14. The transfer device 13 transfers a recording medium having an image thereon to the drier 14 and ejects the recording medium from the drier 14 after drying. The drier 14 evaporates moisture of the recording medium by high frequency dielectric heating.
The electrical power line output from the positive electrode is toward the negative electrode via water 22 contained in paper 21 as the recording medium. An electric field is generated when the electrical power line enters into the water 22, resulting in high frequency dielectric heating.
The positive electrode 23 and the negative electrode 24 in a typical high frequency dielectric heater also serve as rollers to transfer the recording medium. Therefore, the positive electrode 23 and the negative electrode 24 have pillar-like forms. Therefore, the distance between the paper 21 as a heated material transferred in a planar manner and the surface of each electrode changes according to the position in the radial direction of the surface of each electrode, which causes an energy efficiency problem.
First, the current flowing in the capacitor CL is represented by the following equation 3 when a high frequency voltage V0 is applied from the positive electrode and the negative electrode.
In this equation, j represents an imaginary number ((−1)1/2) and ω represents an angle rate of high frequency power.
Furthermore, a high frequency voltage V1 applied to the water is represented by the following equation 4.
The absolute value |V1| of the high frequency voltage V1 is represented by the following equation 5.
The power consumption PL in the water is represented by the following equation 6 due to the equation 5 and the relation between RL and tanδ represented by the equation 2.
According to the equation 6, to increase the power consumption PL in the water, it is necessary to decrease CL/C1, in other words, increase C1/CL.
In addition, a current flowing in C0 is represented by I0. As a current I1 flowing in C1 increases, the amount of power consumption PL consumed at RL increases. That is, the current I0 flowing in C0 can be reduced by decreasing the capacity of the capacitor C0. It is possible to increase the current I1 and furthermore the amount of power consumption PL consumed at R1.
As illustrated in
The form of the electrode can be cuboid, semi-pillar, triangle pole, square pole having a cross section of trapezoid or parallelogram. Of these, a cuboid is preferable in terms of workability. Also, a chamfered cuboid is more preferable to prevent concentration of electric fields.
As an example,
In addition,
As illustrated in
As described above, the high frequency dielectric heater of the present embodiment includes the electrode having a plane surface and the plane surface is disposed in parallel with a subject to be heated.
Therefore, the distance between each electrode and the subject can be made smaller, so that a greater amount of power can be applied to the subject, resulting in improvement of energy efficiency.
The high frequency dielectric heater of the second embodiment has the same configuration as the first embodiment except that the form of the electrodes is different.
In this embodiment, the electrode has a flat-plate like form having a pair of facing flat-plate surfaces having an area (first area) larger than the area (second area) of the other surfaces. Also, the flat-plate surface having the largest area of the surfaces constituting the electrode is disposed in parallel with the subject to be heated.
When the length (depth), the width, and the height of the flat-plate form electrode are respectively defined as L, W, and H, H is shorter than L and H is shorter than W.
In addition, the base of the electrode on the bottom side is disposed at a distance of h0 from the surface of the water. The distance between each electrode is maintained a distance d.
In
As the capacity of the positive electrode and the negative electrode decreases, namely, the distance between the positive electrode and the negative electrode increases, the current I0 flowing into the capacitor C0 decreases and the current I1 flowing into the capacitor C1 increases. That is, as the distance between the positive electrode and the negative electrode increases, the power applied to the water increases.
On the other hand, when the electrode width W of the positive electrode and the negative electrode is caused to increase, C1/CL increases, so that the power applied to the water increases.
The power density is defined by the following equation 7.
L and H of the positive electrode and the negative electrode are determined taking into account the restrictions of the device. Accordingly, it is necessary to calculate the value of W to make the power density P_d maximum from a designing point of view.
In
As described above, the high frequency dielectric heater of the present embodiment includes the electrode having a flat plate-like form and the plane surface having the maximum area is disposed in parallel with a subject to be heated.
Therefore, the energy efficiency is improved.
The high frequency dielectric heater of the present embodiment has the same configuration as the second embodiment except that the electrodes sandwich the subject to be heated and the electrodes are spaced the distance d therebetween from the facing positions of the electrodes.
In addition, both the positive electrode and the negative electrode are disposed at the position of the height h0 in the vertical direction from the water and the distance d between the electrodes in the horizontal direction is 0 or greater.
As described above, the high frequency dielectric heater of the present embodiment sandwich the subject to be heated and the electrodes are spaced the distance d therebetween from the facing positions.
Therefore, it is possible to improve the energy efficiency even when not all the electrodes can be disposed on one side of the subject to be heated due to the restrictions of designing.
According to the present disclosure, a high frequency dielectric heater having improved energy efficiency is provided.
The present disclosure is described with reference to the preferred embodiments but the high frequency dielectric heater of the present disclosure is not limited thereto.
Man in the art is able to suitably modify the high frequency dielectric heater of the present disclosure based on known knowledge. In spite of such modifications, if the configuration of the high frequency dielectric heater of the present disclosure is maintained, the modified device is within the scope of the present disclosure.
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.
Number | Date | Country | Kind |
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2015-098181 | May 2015 | JP | national |