JPH04520Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a magnetron device in which a waveguide is probe-coupled to the electromagnetic wave emission terminal of a magnetron, and in particular to a small and highly efficient magnetron device suitable for microwave ovens. It is.

2. Description of the Related Art In general, a magnetron device used in a microwave oven or the like is constructed as shown in FIG. The probe is connected by protruding into the wave tube 4. The magnetron 1 is excited by an external magnetic circuit consisting of a permanent magnet 5, a frame-shaped yoke 6, etc. On the other hand, a side wall of a shield case 7 attached to the frame-shaped yoke 6 has a through-hole. type capacitor 8 is fixed. And this capacitor 8
A chiyoke coil (not shown), which also constitutes an LC filter circuit, is connected to the cathode terminal of the magnetron 1 and the capacitor 8 within the shield case 7.

The axial length A of the electromagnetic wave emission terminal portion 2 is approximately 1/4λ, where λ is the oscillation wavelength of the magnetron 1, that is, close to 0.2λ to 0.25λ. In addition, the inner dimension w in the width direction and the inner dimension h in the height direction of the waveguide 4 are w=0.57λ～～
0.78λ, h>0.22λ, electromagnetic wave output terminal section 2
The distance d between the central axis of and the short plate 3 is d>0.5λ
It is said that As long as such design standards were followed, the electromagnetic wave output energy of the magnetron 1 could be efficiently transmitted into the waveguide 4.

Incidentally, in order to downsize microwave ovens or expand the internal volume of the microwave oven cooking chamber, there has been a strong demand for reducing the axial length A of the electromagnetic wave emitting terminal portion of the magnetroton. However, if the axial length A of the electromagnetic wave output terminal of the magnetron probe-coupled to the conventional waveguide as mentioned above is 0.18λ,
If the setting is set below, the excitation efficiency of the magnetron device will decrease, resulting in a decrease in the electromagnetic wave energy transmitted to the load.

Figure 4 is a characteristic diagram in which the horizontal axis is the axial length A of the electromagnetic wave emission terminal section, and the vertical axis is the excitation efficiency of electromagnetic energy transmitted to the load (magnetron device efficiency). In, A<
The excitation efficiency at 0.18λ is less than 55%, making it impractical.

Problems to be Solved by the Invention Therefore, the purpose of the invention is to solve the axial length A of the electromagnetic wave emitting terminal of the magnetron.
The object of the present invention is to provide a compact magnetron device that can efficiently transmit electromagnetic wave energy from the terminal portion to the load side through the waveguide while being shortened to 0.18λ or less.

Means for Solving the Problems According to the magnetron device of the present invention, the inner dimension w in the width direction of the waveguide is 0.5λ to 0.6125λ, and the inner dimension h in the height direction of the waveguide is 0.21λ or less. , the distance d between the central axis of the electromagnetic wave emitting terminal and the short plate is 0.25λ or less.

Effect With this configuration, the excitation efficiency (magnetron device efficiency) of electromagnetic wave energy transmitted to the load through the waveguide can be 70% or more even under the condition of A≦0.18λ.

Example A rectangular cylindrical waveguide probe-coupled to the electromagnetic wave emission terminal of a magnetron that oscillates at 2.45 GHz (λ = 122.4 mm) has an internal dimension w in the width direction of 65 mm (0.531 λ).
The inner dimension h in the height direction was 25 mm (0.204λ). The distance d between the central axis of the electromagnetic wave emitting terminal and the short plate was set to 25 mm (0.204λ), and the excitation efficiency was determined by varying the axial length A of the terminal, as shown in Figure 1. The following measurement results were obtained.

As is clear from this, even within the range of A = 0.12λ to 0.17λ, 67
A relatively high excitation efficiency of ~73% can be obtained.

In addition, the axial length A of the electromagnetic wave emission terminal part is 0.18λ.
The optimum joint dimensions between the following magnetron and the rectangular cylindrical waveguide probe-coupled thereto were determined from various experimental data and were as follows.

That is, the inner dimension w in the width direction of the waveguide is w=0.5λ~0.6125λ, and the inner dimension h in the height direction
is h<0.21λ, and the distance d between the central axis of the electromagnetic wave emission terminal and the short plate is d<0.25λ.

As can be seen from these, the inner dimension w in the width direction of the waveguide is set to a condition close to the cutoff wavelength λ=2w. Anything below the cutoff frequency determined by the cutoff wavelength is difficult to transmit due to large attenuation.As mentioned above, if the cutoff wavelength is brought closer to the oscillation wavelength, unnecessary radiation (noise) generated inside the magnetron will be moved closer to the oscillation wavelength. It can be cut to any extent.

FIG. 2 shows an example of the waveguide loss in the device according to the present invention. The smaller the inner dimension w of the waveguide in the width direction, the higher the cutoff frequency.
Loss at lower frequencies also increases.

Effects of the invention Since the invention is configured as described above, it is possible to obtain a magnetron device having highly efficient transmission characteristics while shortening the length of the magnetron, especially the electromagnetic wave emitting end, and to eliminate unnecessary radiation in the low frequency band. This is especially effective when applied to small magnetron devices.

[Brief explanation of the drawing]

Fig. 1 is an excitation efficiency characteristic diagram of a magnetron device implementing the present invention, Fig. 2 is a waveguide loss characteristic diagram of the same device, Fig. 3 is a partially cutaway perspective view of the magnetron device, and Fig. 4 is a diagram of the conventional magnetron device. It is an excitation efficiency characteristic diagram in a magnetron device. 1... Magnetron, 2... Electromagnetic wave emission terminal section, 3... Short plate, 4... Waveguide.

Claims (1)

[Scope of utility model registration request] A rectangular cylindrical waveguide inserted through the electromagnetic wave emission terminal of the magnetron and probe-coupled to the part has one opening closed by a shot plate, and when the oscillation wavelength is λ, the electromagnetic wave The axial length of the emission terminal portion is 0.18λ or less, the inner dimension in the width direction of the waveguide is 0.5λ to 0.6125λ, the inner dimension in the height direction of the waveguide is 0.21λ or less, and the electromagnetic wave is emitted. A magnetron device characterized in that a distance between a center axis of a terminal portion and the short plate is set to 0.25λ or less.