JPH06290712A - Magnetron for microwave oven - Google Patents

Abstract

PURPOSE:To provide a magnetron for a microwave oven which prevent thermal deformation of pole pieces, electric short circuit between vanes and a cathode filament caused by contact or fusion between the pole pieces and end shield, and the deterioration of a degree of vacuum inside a tube. CONSTITUTION:A cathode filament 16 is provided along the axis of an anode cylinder 12 having a plurality of vanes 13 radially disposed therein. Both end of the cathode filament are fixed to end shields 17, 18, respectively. Pole pieces 21, 22 are secured to both opening ends of the anode cylinder, respectively. A<(B-1.11)X1.96 is satisfied, wherein A represents an interval in the axial direction between the end shield and the vane and B represents an interval in the axial direction between the inner circumferential end of the pole piece and the vane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron for a microwave oven.

[0002]

2. Description of the Related Art The main part of a magnetron for a microwave oven is conventionally constructed as shown in FIG. In the figure, reference numeral 11 is an oscillator main body, 12 is an anode cylinder, 13 is a plurality of vanes forming a part of a cavity resonator, 14 and 15 are strap rings, 16 is a cathode filament, and 17 and 18 are ends thereof. Shields, 19 and 20 are cathode support rods 21,
22 is a pole piece, 23 and 24 are metal containers, 25 is an output part, 26 and 27 are permanent magnets, 28 is a yoke, 29 is an antenna lead, 30 is a shim plate, and 31 is a gasket.

In such a magnetron, the end shields 17 and 18 are arranged in order to suppress the electrons emitted from the cathode filament 16 in the working space between the cathode filament 16 and the vane 13. Further, magnetic flux is collected from the permanent magnets 26, 27 into the working space by the pole pieces 21, 22. FIG. 5 shows the calculated electric field distribution and magnetic field distribution in the vicinity of the action space. The dotted line in the drawing represents the electric field distribution and the solid line represents the magnetic field distribution. As is clear from FIG. 5, the distortion of the electric field 32 is large in the electromagnetic field distribution at both ends in the axial direction Z. Also, the axial direction Z
The distribution of the electric field 32 and the magnetic field 33 at both ends determines the force for suppressing the electrons in the action space.

[0004]

However, in the above-mentioned conventional structure, the end shields 17 and 18 are provided, but when the dimensions of the end shields 17 and 18 vary,
On rare occasions, some electrons may leak out of the working space. The stray electrons may reach the pole piece 21 on the output side, generate heat, and the pole piece 21 may be melted and deformed. Although a high voltage is applied between the vane 13 and the cathode filament 16, the pole piece 21 is melted and deformed, so that the pole piece 21 and the end shield 1
7 may come into contact with each other or be welded to each other, resulting in an electrical short circuit. Further, the melting of the pole piece 21 may generate gas, which may deteriorate the degree of vacuum in the magnetron tube and prevent normal oscillation from being maintained.

The present invention has been made to solve the above-mentioned inconveniences, and thermal deformation of the pole piece, electrical short between the vane and the cathode filament due to contact or welding between the pole piece and the end shield, and inside the tube. An object of the present invention is to provide a magnetron for a microwave oven in which deterioration of vacuum degree is prevented.

[0006]

According to the present invention, a cathode filament is provided along an axis of an anode cylinder in which a plurality of vanes are radially arranged, and both ends of the cathode filament are fixed to end shields. In addition, pole pieces are fixed to both open ends of the anode cylinder, and the axial distance between the end shield and the vane is A.
And the axial distance between the inner peripheral end of the pole piece and the vane is B, the microwave magnetron is set to satisfy A <(B-1.11) × 1.96. .

[0007]

According to the present invention, the electrons (stray electrons) emitted from the cathode filament are prevented from excessively flowing into the pole piece, resulting in thermal deformation of the pole piece, contact between the pole piece and the end shield, or It is possible to prevent an electrical short circuit between the vane and the cathode filament due to welding and a deterioration in the vacuum degree in the tube.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

Frequency is 2450 band, output is 400-15
Taking the range of 00 W as an example, the magnetron according to the present invention is configured as shown in FIG. 1, and the same parts as those in the conventional example (FIG. 4) are designated by the same reference numerals.

That is, a plurality of copper vanes 13 are radially arranged inside the anode cylinder 12 constituting the oscillator body 11 to form a cavity resonator. The upper and lower ends of each vane 13 have a pair of large and small strap rings 14,
Every other 15 is connected. Multiple bain 1
A spiral cathode filament 16 is arranged along the axis of the anode cylinder 12 in the electron action space surrounded by the free ends of the electrode 3, and both ends thereof are fixed to the end shields 17 and 18, respectively. The end shields 17 and 18 are supported by the cathode support rods 19 and 20, respectively, and
Both 9 and 20 are fixed to the cathode stem of the input section (not shown). Furthermore, at both open ends of the anode cylinder 12,
The substantially funnel-shaped pole pieces 21 and 22 and the metal containers 23 and 24 are fixed. Each metal container 23, 2
An output unit 25 and an input unit (not shown) are provided on each of the projections 4. Further, permanent magnets 26 and 27 are coaxially arranged so as to surround the metal containers 23 and 24. Usually, a cooling fin (not shown) is provided on the outer circumference of the anode cylinder 12.
Is provided, and a yoke 28 is arranged so as to surround the cooling fins and the permanent magnets 26 and 27. Further, one end of the antenna lead 29 is electrically connected to one of the vanes 13, and the antenna lead 29 is connected to the pole piece 2
1 and extends in the output portion 25 along the tube axis. Reference numeral 30 in the figure is a shim plate, and 31 is a gasket.

By the way, the inventor conducted an experiment using a magnetron for a microwave oven as a test sample shown in FIG.
That is, the magnetron for the microwave oven for this experimental trial is
The dimension C1 of the pole piece flat part is 18 mm, the dimension C2 of the pole piece inner diameter is 9.4 mm, the plate thickness dimension D of the pole piece flat part is 1.34 mm, the number of vanes is 10, and the outer diameter of the end shield on the output side is The dimension E is 7.2 mm, the filament cathode outer diameter dimension F is 3.9 mm, the vane free end dimension G is 9.08 mm, the vane height dimension H is 8.5 mm, and the input side end shield outer diameter is The dimension I is 8.15 mm, and as shown in FIG. 1, the axial distance A between the end shield and the vane is 0.1 to 0.8 m.
The experiment was conducted by setting the axial distance B between the inner peripheral end of the pole piece and the vane to be 1.4 to 1.8 mm. The results of this experiment are shown in FIG. This means that A = (B−1.11) × 1.96

The expression (1) means that the stray electrons spilling out of the working space become the boundary line for excessively entering the pole piece or not. Therefore, in the present invention, the condition that A in the above equation is smaller than the right side is set. This corresponds to the shaded area in FIG.

[0013]

According to the present invention, when the axial distance between the end shield and the vane is A and the axial distance between the inner peripheral end of the pole piece and the vane is B, A <(B -1.11) x 1.96

Since it is set to satisfy the above condition, the electrons (stray electrons) emitted from the cathode filament are prevented from excessively flowing into the pole piece. as a result,
It is possible to prevent the thermal deformation of the pole piece, the electrical short circuit between the vane and the cathode filament due to the contact or welding of the pole piece and the end shield, and the deterioration of the vacuum degree in the tube.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a magnetron for a microwave oven according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a magnetron for a microwave oven for an experimental test according to the present invention.

FIG. 3 is an axial distance A between the end shield and the vane.
And a characteristic curve diagram showing the relationship between the inner peripheral end of the pole piece and the axial distance B between the vane.

FIG. 4 is a vertical cross-sectional view showing a conventional magnetron for a microwave oven.

FIG. 5 is an electromagnetic field distribution diagram in a conventional magnetron for a microwave oven.

[Explanation of symbols]

12 ... Anode cylinder, 13 ... Vane, 16 ... Cathode filament, 17, 18 ... End shield, 21, 22 ... Pole piece.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideyo Ohira 23, 1975, Minamigojo-dori, Asahikawa-shi, Hokkaido Hokuto Denshi Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A cathode filament is provided along an axial center of an anode cylinder in which a plurality of vanes are radially arranged, and both ends of the cathode filament are fixed to end shields. In a magnetron in which pole pieces are fixed to both opening ends, the axial distance between the end shield and the vane is A
When the axial distance between the inner peripheral end of the pole piece and the vane is B, it is set such that A <(B-1.11) × 1.96 is satisfied. A magnetron for a microwave oven.