JPH0629912Y2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a high-frequency heating device using a high-frequency inverter as a power supply device of a magnetron.

<Prior Art> A conventional circuit example will be described with reference to FIG. The commercial frequency power supply 1 is rectified and smoothed by a rectifying / smoothing circuit including a diode bridge 2, a choke coil 3, and a smoothing capacitor 4. The inverter circuit is composed of a high frequency transformer 5 for driving the magnetron, a resonance capacitor 6 connected in parallel with the primary winding 51 of the high frequency transformer 5, a switching element 7 and a diode 8, and the switching element 7 is controlled by an output signal of the control circuit 9. Turn on / off the high frequency transformer 5 2
A high frequency output is generated in the secondary winding 52. The high frequency output boosted by the secondary winding 52 of the high frequency transformer 5 is rectified by the high voltage capacitor 10 and the diode 11 and applied between the anode and cathode of the magnetron 12. The tertiary winding 53 of the high frequency transformer 5 is for supplying electric power to the filament of the magnetron 12, and is connected to the filament terminal of the magnetron 12 via a lead wire.

With the above configuration, the magnetron 12 oscillates to heat the object to be heated with high frequency radio waves.

<Problems to be Solved by the Invention> Since the high frequency transformer 5 generally operates at a high frequency of several tens KHz, the number of turns of the primary winding 51 is small, for example, about 18 turns. Therefore, the number of turns of the tertiary winding that supplies low voltage power to the filament is about 1 to 2 turns, and it is difficult to adjust the filament current to an optimum value by changing the number of turns. Therefore, if the filament current is insufficient, a moding phenomenon occurs and stable output cannot be obtained, and if the current is excessive, the life of the magnetron is shortened remarkably.

The present invention aims to provide a highly reliable high-frequency heating device that solves the above problems by adjusting the filament current to the optimum value.

<Means for Solving the Problems> A magnetic substance 14 for adjusting the inductance of the lead wire 13 is attached to the lead wire 13 that connects the tertiary winding 53 of the high frequency transformer 5 and the filament of the magnetron 12 to pass the filament current. Adjust to the optimum value.

<Operation> The inductance generated by the lead wire 13 and the magnetic body 14 becomes impedance in series with the filament to suppress the filament current.

Therefore, the filament current can be adjusted by selecting the size and number of the magnetic bodies 14.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

The electric circuit diagram of the high-frequency heating apparatus according to the present invention is the same as that of the conventional example shown in FIG. 2, and its description is omitted.

FIG. 1 is a perspective view of an essential part for explaining an embodiment of the present invention. Reference numeral 5 is a high frequency transformer, 13 and 13 are lead wires of a tertiary winding, and leads connected to a filament terminal 12a of a magnetron 12. Also serves as a line. Reference numerals 14 and 14 denote ring-shaped magnetic bodies (ferrite cores), which are fixed by an adhesive so as not to move through the lead wires 13. Core 14
May be fixed using a heat-shrinkable tube or a binding band, and the core 14 may have a bead shape or a cylindrical shape.

In a certain high-frequency heating device, the high-frequency output frequency of the inverter circuit changes within the range of 30 to 50 KHz depending on the magnitude of heating output. The primary winding of the high frequency transformer has 18 turns and the tertiary winding has 1 turn, and the lead wire 13 has a core 14
Without, the magnetron 12 has a filament current of about 13.5 A, and when two ring-shaped cores 14 having an inner diameter of φ5, an outer diameter of φ8 and a thickness of 3 mm are penetrated, the inductance of the lead wire 13 becomes about 3.8 μH, and the filament current Can be reduced to about 11A. That is, the filament current can be adjusted to the optimum value by adjusting the size and the number of the cores 14.

<Effect> The high-frequency heating device of the present invention having the above-described configuration can provide a highly reliable high-frequency heating device in which the filament current is adjusted to the optimum value only by attaching the magnetic material to the lead wire. The cost can be reduced as compared with a magnetron cathode in which a high voltage-type inductance is connected in series to a filament to which a high voltage is applied.

Further, the filament current of the magnetron can be adjusted to the optimum value for each magnetron by simply attaching a magnetic substance to the lead wire connecting the third winding of the high frequency transformer for driving the magnetron and the filament of the magnetron. Since it is possible to set the number and size of magnetic materials freely, even when using magnetrons with different ratings, the filament current can be easily adjusted by simply adjusting the number and size of magnetic materials. Can be accurately adjusted to the optimum value.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a high-frequency heating device according to the present invention, and FIG. 2 is an electric circuit diagram of the high-frequency heating device according to the present invention. Reference numeral 5: high frequency transformer, 53: tertiary winding, 12: magnetron, 13: lead wire, 14: ferrite core (magnetic material).

Claims (1)

[Scope of utility model registration request] 1. An inverter circuit having a high frequency transformer for driving a magnetron and a switching element, which uses a commercial power source as a high frequency power source, a magnetron drive circuit for driving a magnetron with the high frequency power source made by the inverter circuit, and the above inverter. A high-frequency heating device comprising a control circuit for controlling on / off of a switching element of the circuit, wherein a tertiary winding of the high-frequency transformer is provided for supplying power from the tertiary winding of the high-frequency transformer to the filament of the magnetron. And a filament of the magnetron are connected by a lead wire, and a magnetic material for filament current adjustment is attached to the lead wire to change the inductance of the lead wire to regulate the filament current flowing in the filament of the magnetron. High frequency heating device.