JPH0228220B2 - MAGUNETORON - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to improvements in magnetrons.

[Technical background of the invention]

The conventional magnetron main body is shown in Figures 1 to 3.
As shown in the figure, a plurality of plate-shaped anode vanes 12 are arranged radially to surround a central cylindrical cathode 11, and the outer ends of the vanes 12 are connected to the anode cylinder 11.
It is fixed to 3. Upper and lower ends 14 of vane 12
a, 14b have two ring-shaped large and small integrated straps 15a, 15b, 15c, 15, respectively.
d are alternately connected to short-circuit every other vane 12, and the size relationship of the short-circuiting straps at the upper end 14a and lower end 14b of the same vane 12 is opposite. A space surrounded by the two adjacent vanes 12 and the inner wall of the anode cylinder 13 and partially open toward the cathode 11 forms a cavity resonator 16, and is located between the vane free end 17 and the cathode 11. This cavity resonator 16 coupled through the working space 18 determines the oscillation frequency of the magnetron, and the strap separates this oscillation frequency from unnecessary modes and stabilizes it.

[Problems with background technology]

In the magnetron configured as described above, the high-frequency electric field generated by the vane at the upper and lower ends of the working space 18 is deformed by the strap, which excites the cathode 11, causing the high-frequency electromagnetic field to leak to the input section 20 side. Become. Then, the high-frequency electric field distributions measured on the circumference around the cathode axis passing through three points P ₁ , P ₂ , and P ₃ in FIG. 3, which is an enlarged view of the working space 18, are shown in FIG. 4 b, c, and 3, respectively. Shown in d. In the figure, the vertical axis is the high-frequency electric field strength E directed from the cathode 11 toward the vane 12, and the horizontal axis is the rotation angle P around the axis of the cathode 11. The positional relationship between P and the vane 12 is shown in Figure 4a. It is shown. This figure is a linear development of the anode and cathode structure shown in FIG. 1. At point P ₂ in the center of the vane 12, the positive and negative amplitudes of the high-frequency electric field are equal, but at the ends of the vane, such as points P ₁ and P ₃ , where a strap 156 with an opposite potential exists nearby, the vane potential is lowered. Because the electric field is weakened, the positive and negative amplitudes differ greatly.

In such a situation, the high-frequency electric fields felt by the cathode 11 do not cancel each other out, and in the case of FIG. 4b, an electric field is felt in the negative direction. Up to this point, only one side end 14a of the vane 12 has been considered, but since the order of coupling of the large and small straps is also reversed at the other end 14b, a high frequency electric field E in the opposite direction is generated.
The cathode is excited by an electric field as shown by the broken line in FIG. Cathode 11 excited by the above mechanism
radiates a high frequency electromagnetic field to the filter box 21 shown in FIG. The high-frequency electromagnetic field energy reflected by the input section 20 and returned to the working space 18 may cause deterioration of magnetron characteristics such as abnormal heating of the cathode and reduction in efficiency. Therefore, countermeasures against the leakage electromagnetic field have conventionally been taken by configuring a λ/4 choke or a capacitor in the input section 20, by adjusting the input side impedance as seen from the working space 18, and the like. However, such a method is difficult to predict theoretically and is carried out mainly by trial and error, which results in a lot of time and economic waste.In addition, the shape and position of the input section 20, filter box 21, and choke coil 22 are largely defined. Therefore, the low-pass filter section has some drawbacks, such as not being able to provide a sufficient effect.

[Purpose of the invention]

An object of the present invention is to provide a magnetron that improves the above-mentioned drawbacks by reducing the amplitude difference of the high-frequency electric field seen from the cathode.

[Summary of the invention]

This invention is a magnetron in which the distance between the upper and lower ends of the vane free ends and the cathode is set to be shorter when the outer strap is connected than when the inner strap is connected.

[Embodiments of the invention]

The main parts of the magnetron of this invention are shown in Figures 6a and b.
It is constructed as shown in FIG.
1 is shown for each adjacent vane, and the same parts as in the conventional example are given the same reference numerals (excluding the vanes). That is, in this invention, in order to improve the above-mentioned conventional drawbacks, a
In this case, a tapered notch 31 is formed at the lower end of the free end of the vane 30. In the case of b, there is a tapered notch 4 at the upper end of the free end of the vane 40.
1 is formed. In either case, Bain 3
The distances l ₁ and l ₂ between the upper or lower ends of the free ends of the inner straps 15c and 15b and the cathode 11 are
The outer strap 15a,
The length where 15d is connected is set to be shorter. Then, as in a and b, the shortest distances are different from l ₁ and l ₂ for adjacent vanes, respectively.

On the other hand, if the radius from the axis of the cathode 11 to the surface of the vanes 30, 40 is ra, and the high-frequency electric field at the surface is Ea, then the high-frequency electric field E(r) at a point with radius r in the working space 18 is approximately as follows. There is a relationship.

E(r)/Ea=(r/ra) ^N/2 ...(1) However, N is the number of vanes 30 and 40, and the case of π mode oscillation is considered. Therefore, the high frequency electric field amplitudes on the surfaces of the vanes 30 and 40 adjacent to each other at the ends are E ₁ and E ₂ respectively, and the vanes 30 and 40 at this end are
If _{the radius} of the part of ^the cathode ₁₁ that _{is the} shortest _distance from As a result, the high frequency electric field that excites the cathode 11 is significantly reduced.

〔Effect of the invention〕

According to this invention, the distance between the upper and lower ends of the free ends of the vanes 30, 40 and the cathode 11 is
Since the side where the outer straps 15a and 15d are connected is set to be shorter than the side where the outer straps 15a and 15d are connected, the amplitude of the high-frequency electric field differs between the adjacent vanes 30 and 40 at the end of the vane. By adjusting the distance between each vane and the cathode 11, it is effectively canceled out and the excitation to the cathode 11 is prevented. As a result, the internal design of the input section 20 and filter box 21 can be done without being subject to strict regulations such as adjusting the impedance on the input section side as seen from inside the working space 18, which is also effective in improving the performance of the magnetron. .

In the above embodiment, the inner strap 15c,
The end portions of the vanes 30 and 40 to which the inner strap 15b is fixed are moved away from the cathode 11, but as shown in FIG. The upper end of the free end of the vane 50 may be made to protrude toward the cathode 11 side. In this case, the distance to the cathode 11 is adjusted by the protrusion 51.

In addition, in order to adjust the distance to the cathode 11,
Although various shapes are possible, the notch 3 in FIG.
It is desirable to have a tapered shape such that the electromagnetic field changes smoothly toward the center of the action space, such as the protrusion 51 in FIG.

[Brief explanation of drawings]

Figures 1 and 2 are a cross-sectional view and a vertical cross-sectional view showing a conventional magnetron, Figure 3 is an enlarged vertical cross-sectional view of the vicinity of the working space in Figure 2, and Figure 4 is a high-frequency diagram in the working space. An explanatory diagram showing the distribution of an electric field, FIG. 5 is a front view including the exterior of the magnetron, FIG. 6 is a longitudinal sectional view showing the main parts of a magnetron according to an embodiment of the present invention, and FIG. 7 is a diagram showing a magnetron other than the present invention. FIG. 11... Cathode, 13... Anode cylinder, 15a, 1
5b, 15c, 15d...Strap, 30, 4
0...Bane, 31, 41...Notch.

Claims (1)

[Scope of Claims] 1. A spiral directly heated cathode whose outer diameter is constant in the axial direction is disposed along the axis of the anode cylinder, and a plurality of cathodes are disposed inside the anode cylinder. The vanes are arranged radially, and a pair of inner strap rings and an outer strap ring are short-circuited to every other vane in grooves formed at the upper and lower ends of the vanes, In the magnetron, the inner strap ring is short-circuited in one groove, and the outer strap ring is short-circuited in the other groove, and the relationship is alternately reversed between the plurality of vanes, and the free end of the vane on the cathode side and The magnetron is characterized in that the distance from the cathode is set shorter on the end side to which the outer strap ring is connected than on the end side to which the inner strap ring is connected.