JPH0568823B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a magnetron for a microwave oven,
In particular, it concerns magnetrons with structures that can suppress harmonic radiation.

[Technical background of the invention and its problems]

In a microwave oven magnetron, a high frequency wave in the 2450 MHz band, for example, is generated in the resonant cavity of the anode, but in addition to this fundamental wave force, so-called harmonic components having frequencies that are integral multiples of the fundamental wave force are also generated. When this harmonic component is propagated to the heating cavity of the microwave oven together with the fundamental wave, the shorter the wavelength of this harmonic wave, the more difficult it becomes to shield electromagnetic waves in the microwave oven, and the harmonic component is more likely to leak to the outside. Even if this leakage radio wave is quite weak, it may cause radio interference, and the limit value of leakage is regulated by law.

Particularly in recent years, satellite communications have become commonplace, and if the frequencies of radio waves leaking from magnetrons and microwave ovens match the downlink frequency band, reception interference may occur. If the equipment that receives the communication waves transmitted from the satellite is sufficiently far away from, for example, a general household that uses a microwave oven, this will hardly be a problem. However, in the case of satellite broadcasting such as television, the receiving antenna is often located near the place where the microwave oven is used, so it is especially necessary to eliminate any radio wave interference to this satellite broadcasting. There are several internationally allocated frequency bands for satellite broadcast downlink, of which 2450±
The 12GHz band matches the harmonics of the microwave oven magnetron, which has a resonant frequency of 50Hz. This corresponds to exactly five times the fundamental oscillation frequency of a microwave oven magnetron. The wavelength of this fifth harmonic is approximately 24.5 mm.

By the way, it is already known that in order to suppress the generation of harmonics in the magnetron itself, a quarter-wavelength choke is formed in the output section to suppress the radiation of any specific harmonic component. An example of this is the 49th
It is disclosed in Japanese Patent Publication No. 80648, Japanese Patent Publication No. 56-21215, Japanese Patent Publication No. 6862-1982, Japanese Publication Law No. 54-18123, etc.

Such a magnetron has a structure approximately shown in FIGS. 20 and 21. The magnetron oscillation unit main body 30 includes an anode cylinder 31, a plurality of anode vanes 32, a pole piece 33, and a cathode 3.
4. An output antenna section 35 is provided. The output antenna section 35 includes an antenna lead 36 electrically coupled to the anode vane 32 and a cylindrical metal container 3.
7, an inner metal cylinder 38, an insulating cylinder 39 made of ceramics, a metal exhaust pipe 40, and an output cap 41. On the outer periphery of the anode cylinder 31,
A plurality of radiator fins 42 are fixed. Ferrite magnets 43 and 44 are placed at both ends of the oscillating unit main body 30 , and these magnets are surrounded by a ferromagnetic yoke 45. The output antenna section 35 extends through the magnet 43 and yoke 45. The shield box 46 is provided with a cathode input terminal 47.

The antenna lead 36 has a metal exhaust pipe 40 at the tip.
electrically coupled to. The depth l1 of the inner space A of the metal exhaust pipe to which the tip of the antenna lead is short-circuited is, for example, about 1/4 of the second harmonic wavelength, and the annular groove B is formed by the metal container and the inner metal cylinder.
The depth l2 is set to correspond to, for example, about 1/4 of the wavelength of the third harmonic, thereby forming a chi-yoke structure for the second and third harmonics. As is already well known, these quarter-wavelength cheese yokes for suppressing harmonics suppress the creepage distance L on the groove inner wall from point a to b on the conductor wall that forms the opening of the annular groove B, for example. For example, by reducing the wavelength to about half the wavelength of the third harmonic,
The harmonic phase of point B as seen from point A, which creates the aperture, is almost the opposite, and the impedance becomes extremely high.
This is based on the principle that propagation of this harmonic component toward the tip of the output section is suppressed.

Based on such conventional technology, for example, an annular groove B
It is considered that the radiation of this harmonic can be sufficiently suppressed by setting the depth dimension to about 1/4 of the fifth harmonic wavelength, that is, about 6.1 mm. However, even if such dimensions are actually set, the attenuation of the fifth harmonic is slight and far exceeds the radiated power level of the fifth harmonic that must be regulated today due to the above-mentioned circumstances, which is not satisfactory. Nakatsuta. The reason is,
Even if the depth of the annular groove B is simply set to about 1/4 of the wavelength of the fifth harmonic of interest, this harmonic will easily propagate through the space between the antenna lead and the metal container and its inner metal cylinder. It is presumed that this is because the energy is radiated to the outside.

In this regard, the oscillation fundamental frequency of magnetrons, which are particularly widely used in home microwave ovens, is approximately 2450 MHz as mentioned above, and the microwave output power is generally in the 500 to 800 W class. In a magnetron with such a rating, the dimensions of the insulating cylinder of the output section and its vicinity must be such that even when operated under no-load conditions, high-frequency electric fields generated therein will not cause high-frequency discharge. According to experience, the inner diameter of the insulating cylinder must be approximately 14 mm or more, and the axial length must be approximately 12 mm or more. If it is smaller than this, there is a high risk of high-frequency discharge occurring between the metal members sandwiching the insulating tube, or between the soldered part of the metal container to the insulating tube and the antenna lead passing inside it, which may cause the insulating tube to become damaged. Cracks are more likely to occur. In this way, the insulating tube and the metal cylinder require a diameter of a certain size or more, so the space between the metal cylinder and the antenna lead passing inside the metal cylinder becomes large. Therefore, it is presumed that, for example, the fifth harmonic component, which has an extremely short wavelength, is radiated to the outside despite the presence of the chiyoke due to the annular groove.

[Purpose of the invention]

In view of the above circumstances, the present invention provides a magnetron for a microwave oven having a chi-yoke structure that has a large radiation suppression effect on higher harmonics of the fourth order and above, especially the fifth harmonic.

[Summary of the invention]

The first invention provides a quarter-wavelength chiyoke composed of a cylindrical conductor disposed coaxially surrounding an output antenna lead inside a cylindrical metal container hermetically sealed to an anode. , has at least one annular groove for a chiyoke for high-order harmonics higher than the fourth harmonic, and a cylindrical conductor close to the antenna lead has a propagation suppressing effect by the annular groove for a chiyoke formed of this conductor. 2 of the wavelength of the harmonic received
This is a microwave oven magnetron whose inner diameter is set to less than 1/2 of the inner diameter.

In addition, the second invention is such that the quarter-wavelength chain suppresses the propagation of a plurality of high-order harmonics selected from the fourth harmonic, the fifth harmonic, the sixth harmonic, and the seventh harmonic. The cylindrical conductor close to the antenna lead has a wavelength of 1/2 or less of the highest harmonic among the harmonics whose propagation is suppressed by the plurality of annular grooves for the yoke. This is a magnetron for microwave ovens with an inner diameter dimension of .

This makes it possible to reliably suppress the radiation of higher harmonics higher than the fourth harmonic that would otherwise leak from the magnetron to the outside by the chiyoke disposed inside the cylindrical metal container. In addition, if a choke for the second and third harmonics is formed and combined at the tip of the antenna lead, that is, the upper end of the insulating cylinder, it will be possible to prevent these relatively strong low-order harmonics and even weak radio wave interference. Both high-order harmonics that are likely to occur can be reliably suppressed from being radiated.

[Embodiments of the invention]

Examples thereof will be described below with reference to the drawings. Note that the same parts are represented by the same symbols.

The embodiment shown in FIGS. 1 and 2 has the following structure. In the same figure, numeral 30 is the main body of the magnetron oscillation unit, 34 is its cathode, 34a, 34b
31 is a pair of end hats, 31 is an anode cylinder, 32 is a plurality of radial anode vanes, 32
a and 32b are strap rings, 33 is a funnel-shaped pole piece, 33a is a through hole for antenna lead penetration formed in a part of the pole piece, 37 is a cylindrical metal container of the output part, and 37a is hermetically sealed to the anode cylinder thereof. 37b is the tip opening thereof, 39 is the ceramic insulating cylinder of the output part, 40 is the metal exhaust pipe, 40a is the airtight sealing cut portion thereof, 36
4 is the output antenna lead; 36a is the lower end of the antenna lead which is flattened and connected to one of the anode vanes; 36b is the tip of the antenna lead which is held between the metal exhaust pipes and electrically short-circuited;
1 is an output cap; 48 is a metal tube for an outer choke that is hermetically sealed between the outer periphery of the exhaust pipe and the open end surface of the insulating tube; 34 is a cylindrical ferrite permanent magnet; 49
Reference numeral 45 indicates a shim plate made of a ferromagnetic material, 45 a yoke also made of a ferromagnetic material, and 50 a ring-shaped gasket made of a conductive mesh.

An annular space A1 formed between the metal exhaust pipe 40 electrically connected to the tip 36b of the antenna lead 36 and the inner antenna lead 36, and the metal cylinder 22 for the outer chiyoke and this metal exhaust pipe.
The annular space A2 formed between the two main parts constitutes a 1/4-wavelength choke mainly for the second harmonic and the third harmonic.

Now, inside the tip opening 37b of the metal container 37, which is hermetically sealed to the open end of the anode cylinder, an annular groove B having a predetermined depth is formed to exhibit a chioke effect on the fifth harmonic. Therefore, inside the tip opening 37b of the metal container 37,
An intermediate cylindrical conductor 51 is hermetically sealed, a gasket receiving metal ring 52 is bonded thereon, and an expanded flange portion 5 of an inner cylindrical conductor 53 is further bonded thereon.
3a are hermetically sealed. This expanded flange portion 53a is hermetically joined to the lower end surface of the insulating cylinder 39 by a soldered portion 39a.

The inner cylindrical conductor 53 and the intermediate cylindrical conductor 51 are coaxially arranged close to each other around the antenna lead 36 made of a round bar. The inner cylindrical conductor 53 is provided so as to protrude inward from the relatively large-diameter metal container 37 and the insulating tube 39 as shown in the figure. That is, the inner diameter dimension D1 of the inner cylindrical conductor 53 is approximately the same (±10%) as 1/2 (=12.5 mm) of the fifth harmonic wavelength to be suppressed.
or smaller in size. The conductor 53 and the antenna lead 36 are spaced apart from each other by a sufficient distance to prevent discharge from occurring due to a harmonic electric field generated between them.

Further, both the cylindrical conductors 53 and 51 are spaced apart from each other and form a chiyoke annular groove B for the fifth harmonic. The depth Lb of this annular groove B is
Electrically, approximately 1/4 of the 5th harmonic wavelength, that is, the depth between the open ends of both conductors forming the groove opening Bg exhibits high impedance to the 5th harmonic and has a chi-yoke effect. ing. Also, the radial dimension of the groove opening Bg, that is, the opening width Gb
is 1/10 (=2.5mm) of the 5th harmonic wavelength to be suppressed
Below, the dimension is particularly preferably 1/20 (=1.25 mm or less).Thereby, the fifth harmonic component is transmitted through the double cylindrical conductor 53 that surrounds the antenna lead relatively closely. , 51, external radiation is reliably suppressed.

Here, an example of the dimensions of each part is shown. The oscillation fundamental frequency of this microwave oven magnetron is
This is an example of a 2450MHz band with an output of about 800W.

The insulating tube 39 has an inner diameter of 13 mm and a direction length of 10 mm.
mm, the antenna lead 36 is a copper round bar with a diameter D0 of 2.5 mm, and the metal container 37 has an inner diameter of 19 mm and an axial height.
The inner cylindrical conductor 53 has a wall thickness of 0.5 mm, an inner diameter D1 of 9.5 mm, and an axial length of 6.5 mm. The intermediate cylindrical conductor 51 has an inner diameter D2 of 12.0 mm.
The axial length is 4.5 mm, and the depth of the annular groove B formed by both cylindrical conductors
Ld is 5.8 mm, and its opening width Gb is 0.8 mm.

By the way, the present inventors varied the lengths of the inner and intermediate cylindrical conductors 53, 51 and varied the depth Lb of the annular groove formed by them, and compared the external radiated power level of the fifth harmonic. The results are shown by curve P in FIG. The figure also shows a known structure as shown in Figure 21, in which the inner annular groove of the metal container, that is, the inner diameter dimension is larger than 1/2 of the fifth harmonic wavelength (set to 14 mm), and the groove opening is The characteristics of those whose width is larger than 1/10 of this harmonic wavelength (set to 3.0 mm) are shown by the dotted curve R and compared.

As is clear from the figure, according to the magnetron of the present invention, the fifth harmonic component could be suppressed to about -20 dB when the depth Lb of the annular groove B was around 5.8 mm. On the other hand, although the characteristic R of the comparative example shows a minimum level when the groove depth is around 5.7 mm, the level is not satisfactory.

Such actions and effects obtained by the present invention are achieved by the inner cylindrical conductor provided around the antenna lead close to approximately 1/2 or less of the harmonic wavelength whose radiation should be suppressed. This is thought to be due to the formation of a 1/4-wavelength chain in which the space between the shaped conductor and the antenna lead has a diameter smaller than 1/2 of the harmonic wavelength. In other words, since a small-diameter space is formed by the cylindrical conductor around the antenna lead, unnecessary modes of high-order harmonics are difficult to propagate, and the cylindrical conductor creates a chiyoke annular groove for suppressing harmonic propagation. Because of this, it is thought that the harmonic components of most modes are blocked from propagation by this high-impedance choke, and a reliable radiation suppression effect can be obtained. According to the above-mentioned dimension example, an inner cylindrical conductor 53 with a small diameter is provided in the inner region of the metal container 37, and a diameter dimension of about 7 mm (=D1-D0) is provided between this and the antenna lead 36. ) is formed by a narrow opening space. A channel for the fifth harmonic is formed in the inner region of the metal container 37. Therefore, the diameter D0 of the antenna lead is
The external radiation level of the fifth harmonic was measured while changing the inner diameter D1 of the inner cylindrical conductor 53 while keeping it at 2.5 mm. The depth dimension Lb of the annular groove B is 5.8 mm.
It remains as it is. The results are shown in FIG. From this result, if the inner diameter dimension D1 is less than 14 mm, a sufficiently satisfactory chi-yoke effect can be obtained.
In other words, it is confirmed that the inner diameter dimension D1 may be approximately 1/2 of the fifth harmonic wavelength corresponding to the yoke or less.

In addition, the opening width Gb of the annular groove that constitutes the yoke is
By making the harmonic wavelength 1/10 or less, an even sharper attenuation effect can be obtained.
In other words, as shown in Fig. 5, if the aperture width Gb is about 1/10 of the fifth harmonic wavelength corresponding to the chiyoke, and more preferably about 1/20 or less (not including 0), it is even better. A chiyoke effect can be obtained.

Note that the depth Lb of the chiyoke annular groove, which has the greatest suppressing effect, is 1/4 (= 6.1 mm) of the spatial wavelength of the 5th harmonic.
The reason why the dimension is shorter than that is due to the interaction with the annular groove C on the outer periphery, the fact that there is a conductor wall surface extending in the radial direction in a part of the annular groove, and the fringing at the openings of both cylindrical conductors. This is thought to be due to electrical interactions such as effects. In this way, the depth of the annular groove is 1/4 of the spatial wavelength of the harmonic to be suppressed.
Although the dimensions will be slightly shallower than those shown above, the dimensions should be set so that the maximum radiation suppression effect can be obtained in the vicinity.

Further, according to this embodiment, the inner cylindrical conductor is
Since it protrudes inward beyond the airtight solder joint on the lower end surface of the insulating tube, this solder joint is shielded from the high frequency electric field between the antenna lead and these conductors, preventing undesired high frequency discharge and the resulting There is less risk of cracking of the soldered parts.

The present inventors also confirmed that the fourth harmonic radiation level could be significantly suppressed at around 7.1 mm by further increasing the depth of the annular groove.
Therefore, it has been found that it is possible to selectively and reliably suppress any specific higher-order harmonics higher than the fourth harmonic in this manner.

In the embodiment shown in FIG.
is a magnetron that is hermetically soldered directly to the lower end surface of the insulating cylinder 39. Then, the upper end of the cylindrical metal container 37 is folded inward in a half-section U-shape to integrally form an intermediate cylindrical conductor 51, and a ring for receiving the end face of the inner cylindrical conductor 53 and a gasket is attached to the top surface of the folded portion. 52 are hermetically soldered and electrically short-circuited. The inner diameter D1 of the inner conductor 53 is set to about 1/2 of the fifth harmonic wavelength or less. For example, dimension D1 is 13.6mm, D2 is 15.8mm, Gb
is set to 0.6mm.

As a result, it is possible to construct a shield for high-order harmonics by surrounding the antenna lead in the inner region of the metal container with a relatively small number of parts.

In the embodiment shown in FIG. 7, the upper end of the metal container 37 is folded inward to form an intermediate cylindrical conductor 51, and the groove depth Lc of the annular groove C is set to approximately 1/4 of the fourth harmonic. It is sized to correspond to. The inner diameter D2 of the intermediate conductor 51 forming this annular groove C
is approximately 1/2 of the fourth harmonic wavelength, or less. The inner cylindrical conductor 53 is disposed coaxially close to the inner periphery of the intermediate cylindrical conductor 51, thereby forming a chain of the annular groove B for the fifth harmonic. In addition, the inner annular groove B
The depth dimension Lb of the cylindrical conductor 53 is set to 4.6 mm, the inner diameter of the cylindrical conductor 53 is set to 9.0 mm, and the groove opening width is set to 2.7 mm, and the depth Lc of the annular groove C on the outside thereof is set to 8.0 mm. 51
When the inner diameter was set to 15.4 mm and the aperture width was set to 3.0 mm, the fifth and third harmonics were suppressed best.

According to the magnetron of this embodiment, radiation of a plurality of harmonic components including the fifth harmonic can be reliably suppressed with a relatively simple structure.

In the embodiment shown in FIG. 8, an intermediate cylindrical conductor 51 is bent into a crank shape in half cross section, and its large-diameter end face is hermetically soldered to a ceramic insulating tube 39, and an inner cylindrical conductor 53 is fitted inside of it. The flange-shaped portion is electrically coupled to the shoulder portion of the intermediate conductor 51. The metal container 37 has its upper end bent inward and is hermetically fitted to the outer periphery of the intermediate conductor 51. In this case as well, the inner diameter of the inner conductor 53 is
The dimensions are approximately 1/2 of the harmonic wavelength or less.

Note that although the output cap 41 of the example shown in FIG. 1 or FIG. 6 is not shown in this figure, it goes without saying that the output cap of a predetermined length is attached to cover the metal exhaust pipe. . This also applies to each of the following examples.

Each of the embodiments described above is configured such that the opening of the yoke consisting of the annular groove for the fifth harmonic is directed toward the anode. However, the invention is not limited to this, and as shown in FIG. 9, both cylindrical conductors 51 and 53
The opening Bg of the annular groove B may be directed toward the insulating cylinder 39 side, and a channel for high-order high-frequency waves may be provided in the inner region of the metal container 37.

In addition, the annular groove constituting the chi yoke for high-order harmonics may be curved to have an L-shaped cross section as shown in Fig. 9, and in that case, the depth of the groove that acts as the chi yoke and the L-shaped space dimension. The electrical length is determined by Therefore, according to this, the length of the cylindrical conductor in the axial direction of the antenna can be shortened, and the antenna can be made compact.

In the embodiment shown in FIG. 10, a part of the metal container 37 hermetically sealed to the anode is bent inward to form a small-diameter portion 37c, and an inner cylindrical conductor 53 is electrically connected inside the small-diameter portion 37c. It is connected to. The inner diameter of this inner conductor 53 is set to be approximately 1/2 of the fifth harmonic wavelength or less. In this region, an annular groove B is provided which serves as a choke for the fifth harmonic. The dimensions of this groove B are similar to the implementation described above. According to this, the number of parts can be further reduced.

In the embodiment shown in FIG.
together with the insulating cylinder 39, approximately 1/ of the fifth harmonic wavelength.
An inner cylinder 53 (inner diameter D1=11.0 mm) is formed to have an inner diameter D3 (= about 13.6 mm) corresponding to mm).

According to this embodiment, almost the entire output section is configured to have a diameter corresponding to approximately 1/2 wavelength of the high-order harmonic corresponding to the harmonic choke provided in the inner region of the metal container. A reliable radiation suppression effect of harmonics can be obtained, and the cylindrical permanent magnet 43 disposed around the outer periphery of the metal container can be made relatively small in diameter. Therefore, the magnetic utilization efficiency of the magnet is increased and the entire magnetron can be made compact.

In the embodiment shown in FIG. 12, the metal container 37 is bent inward to form an intermediate cylindrical portion 51, thereby forming an outer annular groove B. Furthermore, this metal container is integrally molded with an inner cylindrical portion 53 that is folded back at the bending portion and extends in the direction of the insulating portion 39. In this way, the inner cylindrical part 53, the intermediate cylindrical part 51 and the metal ring 52 located on the outer periphery of the inner cylindrical part 53,
An inner annular groove C is formed with the inner cylindrical portion. The inner and outer double annular grooves B and C each have a chioke effect on arbitrary harmonics. For example, the depth Lb of the outer annular groove B corresponds to approximately 1/4 of the wavelength that suppresses the transmission of the fifth harmonic, and the depth Lc of the inner annular groove C suppresses the transmission of the fourth harmonic. The dimensions are set to correspond to approximately 1/4 wavelength of the wavelength. The openings of both annular grooves B and C are oriented in opposite directions with respect to the tube axis direction. That is, the opening of the outer annular groove B is oriented toward the anode vane, and the opening of the inner annular groove C is oriented toward the tip of the antenna lead. As a result, compared to the case where the openings of multiple quarter-wavelength cheese yokes are located on the same plane, interference between the cheese yokes, disturbance of the electromagnetic field due to fringing, etc., and generation of higher-order modes are suppressed. It is possible to enhance the effect of each chiyoke.

Note that the inner diameter dimension D1 of the inner cylindrical portion 53 is approximately 1/2 wavelength of the harmonic that is planned to be suppressed by the annular groove B located on the anode vane side, that is, the fifth harmonic in this embodiment. or smaller in size. However, the inner cylindrical portion and the antenna lead are separated by a sufficient distance to prevent discharge from occurring due to the high frequency electric field generated between them. Further, the radial dimension of each opening of both annular grooves B and C, that is, the groove opening width, is set to be 1/10 or less, particularly preferably 1/20 or less, of the harmonic wavelength to be suppressed. As a result, external radiation of the fourth and fifth harmonic components is more reliably suppressed by the yoke formed of double annular grooves surrounding the antenna lead relatively closely. Further, since the metal container 37 constituting the two yokes is a single component, the number of parts is small, mass production is possible, and the yokes structure can be manufactured with relatively high precision.

In the embodiment shown in FIG. 13, one end of a separately prepared inner metal cylinder 35 is joined to the inner periphery of an intermediate cylinder 51 integrally formed with a metal container 37.

In this embodiment, each part can be easily pressed, and the depth dimension of the annular groove C can be arbitrarily set at the time of joining.

The embodiment shown in FIG. 14 is a metal container 3 integrally formed with a half-section crank shape having the structure shown in FIG. 12.
The back surface of a bottomed metal ring 60 formed into a half U-shaped cross section is joined to the top surface of the second bent portion of No. 7. This bottomed metal ring 60 has an annular groove E whose depth corresponds to approximately 1/4 wavelength of the sixth harmonic, which suppresses transmission of the sixth harmonic. These two annular grooves E and B are opposite to each other in the tube axis direction, and have the same diameter and are arranged in a vertical line so as not to overlap each other in the radial direction. Further, the outer annular groove C includes the metal container 37, the intermediate cylindrical portion 51, and the outer cylindrical portion 60a of the bottomed metal ring 60. In this case, the annular groove C is a chiyoke for the fourth harmonic, and the annular groove B
is a chiyoke for the fifth harmonic. 2
The two inner cylindrical portions 60b and 53 have the same diameter and closely surround the antenna lead as described above. The inner diameter of this inner cylindrical part is
Of these three annular grooves, the annular grooves C and E located in the anode vane direction relative to the cylindrical part are the sixth annular groove that is designed to suppress the highest harmonic, that is, in this embodiment, the annular groove E is The size is approximately 1/2 of the harmonic, or smaller.

With this, it is possible to incorporate a radiation suppression choke for three higher harmonics without changing the external shape or complicating the structure too much. In addition, since the bottomed metal ring 60 having a U-shaped half-section is an integral part that is molded separately, its depth can be determined with high precision.
In particular, it is possible to construct a choke for higher-order harmonics.

In the embodiment shown in FIG. 15, a chiyoke annular groove C for the fourth harmonic is provided in the inner region of the metal container 37.
The chiyoke annular groove B for the fifth harmonic and the chiyoke annular groove E for the sixth harmonic are arranged alternately and coaxially. That is, a substantially U-shaped chiyoke member 61 is fixed inside the metal container 37, and two annular grooves C and B are formed with openings located in opposite directions. Another approximately U-shaped yoke member 62 is fixed inside this yoke member 61, and an annular groove E is formed therein. The depth of each annular groove corresponds to approximately 1/4 wavelength of the harmonic to be blocked. The inner diameter dimension D1 of the inner cylindrical portion of the innermost chiyoke member 62 is approximately 1/2 of the sixth harmonic wavelength.
or less, and the dimensions are such that harmonic discharge does not occur between the antenna lead 36 and the antenna lead 36.

According to this embodiment, it is possible to similarly suppress external radiation of the fourth to sixth harmonic components.

In the embodiment shown in FIG. 16, four conductor cylinders 6 constituting a chiyoke member are installed in the inner region of the metal container.
3, 64, 65, and 66 are fixed coaxially to each other. Chiyoke annular groove C due to them
corresponds to approximately 1/4 wavelength for the 4th harmonic, groove B for the 5th harmonic, groove E for the 6th harmonic, and groove F for the 7th harmonic. It has a depth dimension. The inner diameter D1 of the innermost conductive cylinder 66 is 9 mm, which corresponds to approximately 1/2 of the wavelength of the seventh harmonic. This makes it possible to suppress external radiation of harmonic components in a wide range from the fourth to the seventh harmonics. Note that the opening width of each annular groove is set to a dimension of 1/10 wavelength or less of each intended harmonic.

In the embodiment shown in FIG. 17, the outermost L-shaped annular groove C is a chiyoke groove of approximately 1/4 wavelength for the fourth harmonic, the inner groove B is for the fifth harmonic, and the groove E is for the fifth harmonic. The groove F corresponds to the 6th harmonic and the 7th harmonic, respectively, and a U-shaped conductor 67 and cylinders 68, 69 are formed.
A chiyoke member is constructed by combining these.

In the embodiment shown in FIG. 18, a metal container 37 and four conductor cylinders 63, 64, 65, 66 coaxially fixed inside the metal container 37 are provided with their open ends offset along the axial direction. be. This constitutes a plurality of chi-yoke annular grooves C, B, E, and F for different high-order harmonics.

In the embodiment shown in FIG. 19, the annular grooves C, B, and E for the fourth, fifth, and sixth harmonics are formed in the inner region of the metal container 37 with their openings facing toward the insulating cylinder 39. It was established. The inner diameter dimension D1 of the innermost conductive cylinder 66 is approximately 1/2 of the sixth harmonic wavelength.

〔Effect of the invention〕

As explained above, the annular groove formed by the cylindrical conductor surrounding the antenna lead is provided in the inner region of the cylindrical metal container that is hermetically sealed to the anode cylinder of the present invention and extends toward the output side. The chi-yoke structure is a chi-yoke for high-order harmonics higher than the fourth harmonic, and is characterized in that the inner diameter is configured to be approximately 1/2 of the harmonic wavelength or less.

As a result, any specific high-order harmonics higher than the fourth harmonic that are about to leak out from the magnetron can be removed by at least one chi-yoke structure consisting of an annular groove arranged in the inner region of the cylindrical metal container. Radiation can be suppressed reliably.

Note that the second and third
By forming and combining harmonics, it is possible to reliably suppress the radiation of both these relatively strong low-order harmonics and the high-order harmonics, which are weak but are likely to cause radio wave interference.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a main part showing an embodiment of the present invention, FIG. 2 is a cross-sectional view taken at 2-2 in FIG.
Fig. 3 is a characteristic diagram showing a comparison of the harmonic suppression levels of an embodiment of this invention and a conventional structure, and Figs. 4 and 5 are characteristic diagrams showing harmonic suppression levels of each embodiment of this invention. , FIG. 6 is a vertical cross-sectional view of a main part showing another embodiment of the present invention, FIGS. 7 to 19 are longitudinal cross-sectional views of main parts showing still other embodiments of the invention, and FIG. FIG. 21 is a side view showing the general structure of the conventional structure. 30 ... Oscillator main body, 31... Anode cylinder, 32... Anode vane, 33... Pole piece, 35... Output section, 36... Output antenna lead, 37... Cylindrical metal container, 39... Insulation Cylinder, 51... Intermediate cylindrical conductor, 53... Inner cylindrical conductor, B, C, E, F... Harmonic chiyoke annular groove, D1... Inner diameter dimension of cylindrical conductor, Lb, Lc
... Depth of the annular groove, Gb ... Groove opening width.

Claims (1)

[Claims] 1. A cathode, a cylindrical anode having a resonant cavity arranged around the cathode, a cylindrical metal container hermetically sealed to a part of the anode, and a cylindrical metal container that is directly attached to the metal container. or an output part insulating cylinder hermetically sealed via another joining member; an output antenna lead having one end electrically coupled to the resonant cavity of the anode and extending through the inner space of the metal container; and the metal In a magnetron for a microwave oven, which is equipped with a quarter-wavelength chock consisting of an annular groove for the chock, which exhibits a propagation suppressing effect on arbitrary specific harmonics by means of a cylindrical conductor conductively disposed inside the container. , the chiyoke has at least one chiyoke annular groove for high-order harmonics higher than the fourth harmonic, and the cylindrical conductor close to the antenna lead has an annular chiyoke groove formed of the conductor. 1/2 of the wavelength of the harmonic that is subject to propagation suppression
A magnetron for a microwave oven, characterized by having the following inner diameter dimensions. 2. The width of the opening of the annular groove is approximately 10 times the wavelength of the harmonic that is to be suppressed.
The magnetron for a microwave oven according to claim 1, wherein the magnetron is set to have a size that is one-fold or smaller. 3. A cathode, a cylindrical anode having a resonant cavity arranged around the cathode, a cylindrical metal container hermetically sealed to a part of the anode, and a cylindrical metal container that is connected directly or with another joining member to the metal container. an output section insulating tube hermetically sealed through an output part insulating tube; an output antenna lead having one end electrically coupled to the resonant cavity of the anode and extending through the inner space of the metal container; and an output antenna lead disposed inside the metal container. In a microwave oven magnetron, the microwave oven magnetron is equipped with a quarter-wavelength type chiyoke consisting of an annular chiyoke groove that exhibits a propagation suppressing effect on arbitrary specific harmonics using a cylindrical conductor. , a plurality of annular grooves for a chiyoke for suppressing propagation of a plurality of high-order harmonics selected from among the fifth harmonic, the sixth harmonic, and the seventh harmonic, and a tube close to the antenna lead. A magnetron for a microwave oven, characterized in that the shaped conductor has an inner diameter dimension that is equal to or less than half of the wavelength of the highest harmonic among the harmonics whose propagation is suppressed by the plurality of annular grooves for the yoke. . 4. The magnetron for a microwave oven according to claim 3, wherein the plurality of annular grooves for the yoke are opened in mutually different directions.