JPH0652805A - Magnetron - Google Patents

Abstract

(57) [Abstract] [Purpose] The vane single-sided end face strapping method has a surge voltage at the start of oscillation operation and the oscillation efficiency of the magnetron, which are both within a practically valid range of 245.
It is to provide a 0 MHz band magnetron. [Structure] The height of the strap ring in the tube axis direction is 1.6 ~
It was set to 2.3 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention outputs microwave power with high efficiency, and suppresses the surge voltage generated in the step-up transformer of the power supply to a relatively low level even if the oscillation is stopped during the rise of the oscillation. 2450MHz ISM
(Industrial, Scientific and Medi-cal Use) Band-related magnetron.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional magnetron used in a microwave oven or the like, for example, disclosed in Japanese Patent Laid-Open No. 1-63245, taken along a plane passing through a tube axis. The cathode 1 is surrounded by an end portion of an even number of vanes 3 radially protruding from the inner surface of the anode cylinder 2, and the anode cylinder and the vane group form an even number of cavity resonators.
The space between the cathode 1 and the end of the vane 3 is called the working space, in which the annular permanent magnet 4 serves as a magnetomotive force source, the yoke 5 serves as an external magnetic circuit, and the magnetic pole 6 serves as a magnet in the tube axial direction. Static magnetic field is formed. The electrons emitted from the cathode 1 are attracted and accelerated to the side of the anode vane where a high DC positive voltage is applied to the cathode, but are accelerated by the magnetic field in the tube axis direction perpendicular to the movement direction. Electrons that are acted on by a force in the direction orthogonal to the direction of the magnetic field cross the tip of the vane in the circumferential direction and try to return to the cathode side, resulting in a high electron density portion and a sparse portion in the action space. A high-electron-density electron cloud orbits the working space at high speed to excite microwave electric vibrations in the cavity resonator group. Of the electric vibrations in the cavity resonator group, the strongest and most stable oscillation is the so-called π-mode oscillation in which the adjacent cavities have opposite phases. Electrically connect the points that have the same potential (same phase) by this π-mode vibration, and alternately connect every other vane to stabilize the π-mode vibration immediately, especially in the initial stage of oscillation. The inner strap ring 8 and the outer strap ring 9 are housed and installed inside the groove 7 provided on the end surface of the vane in the tube axial direction. The microwave electric vibration is guided to the microwave output extraction unit 11 by the antenna 10 connected to the end face of one vane, and is externally used, for example, in a microwave oven.
It is used for heating food. The cathode 1 is supported by the cathode stem via the heating power supply line.

Currently, the most mass-produced magnetrons in the 2450 MHz band are those for microwave ovens, but in the case of household electric appliances, it is extremely important that the performance and cost are low. Therefore, various efforts have been made to reduce the price of magnetrons for microwave ovens. In the above conventional magnetron, strap rings are arranged on both end surfaces of the vane in the tube axis direction,
If this is installed on only one end surface (actually the microwave output extraction portion side), the man-hours and parts cost can be reduced.

However, if the strap ring is installed only on one end face of the vane and the other part is left as it is, the resonance frequency becomes too high. this is,
Although the capacitance between the inner and outer strap rings or between the strap ring and the vane (which passes over the bottom surface of the storage groove without being connected to the strap ring) affects the resonance frequency, those capacitances Because it will be almost half. To suppress this frequency increase, Japanese Patent Application No. 2
No.-405641 encloses a groove on the microwave output extraction side end face of each vane equidistantly from the tube axis, and alternately connects every other vane inside. There is disclosed a technique for compensating for the above-mentioned lack of capacitance by providing a protruding portion at the tip of each vane symmetrically to the tip side of both adjacent vanes and facing the adjacent vane side in a plane parallel to the tube. According to this technique, the shortage of the electrostatic capacity of the resonator is compensated, and the frequency shift does not occur. Figure 4
FIG. 4A is a sectional view taken along a plane passing through the tube axis of each relevant portion of the magnetron according to the above technique, and FIG. 4B is a bottom view showing the shape of the protruding portion of the vane tip. In the figure, 31 is a projecting portion at the tip of the vane, and other reference numerals are the same as in the case of FIG. Providing such an overhanging portion at the tip of the vane makes the shape of the hob somewhat complicated when integrally molding the anode cylinder and the vane group by hobbing, but at the central portion of the material (pure copper) plate, Since the amount of material extruded is reduced, the resistance to the hob is reduced and the life of the hob is extended, and there is no problem such as cost increase.

[0005]

If the protruding portion is provided at the tip of the vane as described above, the shortage of the capacitance of the resonator can be compensated for. Therefore, the heights of the inner and outer strap rings in the tube axis direction are particularly limited. There is no need to increase the capacitance between them by increasing the capacitance. However, in the magnetron for microwave oven, the antenna that guides microwave power to the output is connected only to the end face of one vane, so there is no symmetry in the position of each resonator with respect to the antenna connection, and the strap ring Is π
A little current flows even during mode vibration. Furthermore, a considerable current always flows through the strap ring during vibrations other than the π mode. This difference in current value is useful for mode separation. Therefore, if the impedance of the strap ring is made too large, the isolation characteristic of the oscillation mode deteriorates, which causes abnormal oscillation, oscillation stop, and the like. On the other hand, if the cross-sectional area and hence the surface area of the strap ring are increased in an attempt to reduce the impedance of the strap ring, the microwave loss generated on the surface during energization increases and the oscillation efficiency of the magnetron decreases. If a strap ring is provided on only one end surface of the vane, there is also the problem of capacitance between the inner and outer strap rings, and even considering the above oscillation efficiency, the height of the strap ring in the tube axis direction can be adjusted. It cannot be made too low. The thickness of the strap ring in the radial direction is also pure copper, so if it is made too thin, it may be deformed during handling. is there. After all, the axial height of the strap ring has just an appropriate dimension related to the oscillation frequency.

In the case of a microwave oven, a cathode heating power source and a magnetron anode DC high-voltage power source (usually a voltage doubler rectification system) are usually provided in a secondary side winding of a common transformer in order to reduce costs. I got it from the line, and immediately after turning on the power,
Generally, the cathode temperature is still low and the amount of thermionic emission is small, but since a high anode voltage is applied, abnormal oscillation or temporary suspension of oscillation easily occurs. If the oscillation is suspended,
Since the cathode temperature is increasing and the amount of emitted electrons gradually increases, the oscillation does not stop. However, a surge voltage is generated in the high voltage winding of the power transformer, which has a large number of turns at the moment of the oscillation stop, and the resulting insulation breakdown of the winding or the like and short circuit accident are fearful.

The present invention is a magnetron for the 2450 MHz band, in which a strap ring is provided only on one side in the axial direction of the vane, even if a surge voltage is generated in the power transformer winding at the rise of microwave vibration. An object of the present invention is to provide a device having a low value and good oscillation efficiency.

[0008]

In order to solve the above problems, according to the present invention, an even number of vanes are radially projected from the inner circumference of an anode cylinder to form a cavity resonator group with the anode cylinder and the vanes. , Among the microwave vibrations excited in the cavity resonator group, in order to stabilize the π-mode vibration in the opposite phase between the adjacent cavities, every other vane is connected to the other at the same site. , The outer strap ring,
It is housed and installed in the groove engraved only on the end surface of each vane on the microwave output extraction side, and further projects symmetrically toward the tip side of both adjacent vanes at the tip of each vane and faces the adjacent vane side in a parallel plane. 2450MHz ISM with overhang
In the band magnetron, the height of the strap ring in the tube axis direction is set to 1.6 to 2.3 mm.

[0009]

When the strap ring is provided only on one side of the vane in the axial direction, there is a method of increasing the capacitance by shortening the distance between the inner and outer strap rings in order to compensate for the decrease in the capacitance. It is not possible because it is difficult to press both strap rings at the same time, and there is a high possibility that they will come into contact with each other when brazing silver with the vane.

As described above, if the height of the strap ring in the tube axis direction is increased, the inductance of the strap ring is lowered, so that the oscillation mode separation is good. On the other hand, microwave waves will be carried on the strap ring, but the loss caused by it will be
As mentioned above, the larger the surface area of the strap ring (if the radial thickness of the strap ring is constant,
As the height in the tube axis direction increases, the microwave output that can be supplied to the outside decreases, and the oscillation efficiency decreases.

Therefore, with respect to the height of the strap ring in the tube axis direction, it is better that it is lower in terms of oscillation efficiency and higher in terms of mode separation. We will seek a compromise between conflicting conditions. The frequency of microwaves generated is 245
Since it is determined to be 0 MHz, the shape and dimensions of the cavity resonator are almost determined, and if the condition that a strap ring is provided only on one end face of the vane is added to it, the cross-sectional shape dimension of the practical strap ring is within a certain range. It is natural that it is limited to. The present inventor has conducted many experiments and found that, in the case of the vane one-sided end face method, a compromise of the height of the strap ring in the tube axis direction is 1.6 to 10.
The range of 2.3 mm was defined. Within this range, there is no problem in mass production.

[0012]

EXAMPLE FIG. 1 shows an anode assembly in which a strap ring is provided only on one side of a vane, which is a main part of the magnetron of the present invention.
It is sectional drawing by the plane which passes along a pipe axis.

FIG. 2 shows the height of the strap ring in the tube axis direction when the inventor uses the vane one-sided end face system.
This is a summary of the results of the experiment conducted to determine the range of 1.6 to 2.3 mm. The horizontal axis shows the height of the strap ring in the tube axis direction in mm, and the left vertical axis shows the surge voltage k.
In V _P , the oscillation efficiency η is shown in% on the right vertical axis. When the height of the strap ring is 1.4 mm or less, the mode separation becomes poor, and the surge voltage sharply rises to 14 kV _P or more, and when the height of the strap ring becomes 2.3 mm or more, the oscillation efficiency becomes 70%. It drops sharply below%.

[0014]

As described above, according to the present invention, the height of the strap ring of the vane one side end face strap ring type magnetron in the tube axis direction is set to 1.6 to 2.3 mm, so that when the magnetron oscillation operation starts up. It was possible to set the surge voltage and the oscillation efficiency of the magnetron within the practically appropriate range.

[Brief description of drawings]

FIG. 1 is a sectional view taken along a plane passing through a tube axis of an anode assembly which is a main part of a magnetron of the present invention.

[Fig. 2] The horizontal axis indicates the height of the strap ring in the tube axis direction.
FIG. 3 is a diagram showing the relationship between m and m, and the left vertical axis shows the surge voltage in kV _P , and the right vertical axis shows the oscillation efficiency η in%.

FIG. 3 is a sectional view taken along a plane passing through a tube axis of a conventional magnetron used in a microwave oven or the like.

FIG. 4 (a) is a sectional view taken along the plane passing through the tube axis of the main part of the vane one-sided end face strap ring type magnetron according to the prior art, and FIG. 4 (b) shows the shape of the protruding portion of the vane tip. It is a bottom view.

[Explanation of symbols]

2 ... Anode cylinder, 3 ... Vane, 7 ... Strap ring storage groove, 8 ... Inner strap ring, 9 ... Outer strap ring, 10 ... Antenna, 31 ... Vane tip protrusion.

Claims (1)

[Claims] 1. An even number of vanes are radially projected from the inner circumference of an anode cylinder to form a cavity resonator group by the anode cylinder and the vane, and among the microwave vibrations excited in the cavity resonator group, In order to stabilize the π-mode vibration that is the opposite phase between adjacent cavities, every other vane is connected to each other at the same site, and the outer strap ring is connected to the end face of the microwave output side of each vane. Installed inside the groove engraved only on the chisel, and further provided at the tip of each vane with a protruding portion that symmetrically protrudes toward the tip side of both adjacent vanes and faces the adjacent vane side in a parallel plane. In the magnetron, the height of the strap ring in the tube axis direction is 1.6 to 2.3 mm.