JP2002343262A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetron capable of improving the oscillation efficiency. SOLUTION: In this magnetron, formed by placing a cathode body on a central part of an anode cylindrical body, and forming an anode cavity around the cathode body, a magnetic field strength B is given according to following mathematical expression determined on the basis of dimension (mm) of the radius of a cathode rc, dimension (mm) of the radius of an anode ra, and peak anode voltage Va (V) to avoid or region of the magnetic field strength where the oscillating efficiency of the magnetron levels off or lowered, even when the magnetic field strength is increased. B=nλVa/942γa <2> (1-σ<2> )+10650/nλ(1-σ<2> ), where σ=rc/ra, n=number of divisions of anode/2, and λ is the wavelength (mm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetron. More specifically, for example, a magnetron used for microwave heating equipment such as a microwave oven or a radar, and provided with a magnetic circuit for generating a magnetic field strength corresponding to the dimensions of the anode radius, the cathode radius, and the peak anode voltage. About magnetrons.

[0002]

2. Description of the Related Art In recent years, energy saving and resource saving have been demanded worldwide due to global environmental problems, and the electric industry and the microwave oven industry have been actively working on them. In a microwave oven, it is desired to improve the oscillation efficiency as a magnetron while performing load impedance matching and improving the power factor of a microwave oven in order to improve the high-frequency heating efficiency.

As shown in FIGS. 3 and 4, for example, a magnetron used in a microwave oven or the like includes a cylindrical anode cylinder 51 and vanes radially arranged on the inner peripheral surface of the anode cylinder 51. 52, a cathode body 53 disposed on the center axis of the anode cylinder 51 in a space surrounded by the tip of the vane 52, and a cathode body connected to any one of the vanes 52, for example, a 2450 MHz micro An antenna conductor 54 for extracting a wave to the outside, and an antenna conductor 54 disposed on the upper and lower surfaces of the vane 52;
2 and an inner strap ring 55 and an outer strap ring 56 for stabilizing the π mode oscillation, and a magnetic material that is disposed at the periphery of the upper and lower openings of the anode cylinder 51 and concentrates the magnetic field in the working space. The pole pieces 57, 58, one end are connected to the sealing metal 59, 60 fixed to the periphery of the upper and lower openings of the anode cylinder 51, and one end is connected to the sealing metal 59 via the insulating cylinder 61. A vacuum tube comprising an exhaust pipe 62 and a cathode stem 64 fixed to the sealing metal 60 and supporting a cathode terminal 63 of the cathode body 53 is provided.

[0004] The magnetron comprises such a vacuum tube and annular magnets 65 arranged above and below the anode cylinder 51.
A plurality of heat sinks 66 fixed to the outer peripheral surface of the anode cylinder 51, a yoke 67 surrounding the anode cylinder 51, the annular magnet 65 and the heat sink 66, and a cathode stem 64 protruding from the yoke 67. An enclosing shield case 68, a choke coil 69 housed in the shield case 68 and having one end connected to the cathode terminal 63,
8 and a through capacitor 70 connected to the other end of the choke coil 69.

In the magnetron having such a structure, the thermoelectrons emitted from the cathode body 53 are injected into the cylindrical working space between the cathode body 53 and the vane 52 by a magnetic field applied perpendicular to the electric field. It circulates in the working space and generates microwaves of high-frequency energy.

Incidentally, the oscillation efficiency of a magnetron is generally determined by the product of the electronic efficiency and the circuit efficiency. The circuit efficiency is determined by the Q (selectivity indicating resonance sharpness) of the cavity resonator and the material properties. However, oxygen-free copper is generally used because it is limited by suitability as a vacuum tube material and cost. . On the other hand, the electron efficiency is the conversion efficiency from the DC input, which is the potential energy of electrons, to microwaves.
The radius of the cathode is rc (mm) and the radius of the anode is ra
(Mm), and the magnetic field strength determined by the capacity of the magnet, the material of the magnetic material, and other components constituting the magnetic circuit such as the pole piece is B (mT), and the critical magnetic field strength is B _OH (mT). The fact that the electron efficiency ηe is given by the following equation (1) is described in “Basics of Microwave Engineering” (by Toshio Makimoto and Yukito Matsuo: published by Hirokawa Shoten).

[0007]

(Equation 2)

Here, n is generally the number of divided anodes / 2 for π mode oscillation, and is, for example, 5 for a magnetron with 10 divided anodes. Λ is a wavelength (mm). For example, in the case of an oscillation frequency of 2450 MHz, about 1
22 (mm).

Therefore, as shown in FIG. 5 from the curve of the theoretical equation of the above equation (1), as the magnetic field strength B increases, the electron efficiency ηe increases. However, it was theoretically thought that the oscillation efficiency of the magnetron also increased.

[0010]

However, in order to improve the oscillation efficiency of the magnetron, many experiments were conducted. As the magnetic field intensity B was increased, the oscillation efficiency of the magnetron became flat or decreased. Theoretical formula (2)
It was found that there was a magnetic field intensity region that did not match the above. In other words, in order to increase the oscillation efficiency of the magnetron, increase the capacity of the magnet, improve the use of ferromagnetic materials, and improve other parts such as pole pieces, for example, by increasing the cross-sectional area and reducing the resistance. However, the oscillation efficiency of the actual magnetron does not increase. Since the conventional magnetron has not been required to have higher efficiency than before, a magnetic field intensity is not required so that the oscillation efficiency of the magnetron is flat or lower, and such a phenomenon has not been considered.

The present invention has been made in view of the above circumstances, and has as its object to provide a magnetron that can improve oscillation efficiency.

[0012]

According to the present invention, there is provided a magnetron in which a cathode body is disposed at a center of an anode cylinder and an anode cavity is formed around the cathode body.
Even if the magnetic field strength is increased, the magnetic field strength B given by the following equation is set to the dimension (m) of the cathode radius rc so as to avoid the field of the magnetic field strength where the oscillation efficiency of the magnetron is leveled or reduced.
m), dimensions of the anode radius ra (mm), peak anode voltage Va
It is set based on (V).

[0013]

(Equation 3)

Here, σ = rc / ra, anode division number / 2
Is n, and the wavelength (mm) is λ.

Preferably, the magnetic field intensity B is 218 (mT) or more.

The dimension of the anode radius ra is 4.00 to 5.05 (mm), the dimension of the cathode radius rc is 1.75 to 2.15 (mm), and the peak anode voltage Va is 6910 (V) or less, and the magnetic field density B is 21
It is preferably 8 (mT) or more.

It is preferable that the anode cylinder has an anode division number of 10.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magnetron according to the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, a magnetron according to an embodiment of the present invention is the same as the conventional magnetron shown in FIGS. Are arranged around the cathode body 2 to form an anode cavity, and other basic configurations, that is, the vanes 3 radially arranged on the inner peripheral surface of the anode cylinder 1 and the vanes 3 A cathode body 2 arranged in a space surrounded by the tip,
An antenna conductor 4 connected to any one of the vanes 3; an inner strap ring 5 and an outer strap ring 6 disposed on the upper and lower surfaces of the vane 3; Pole piece 7 arranged on the periphery of
A sealing metal having one end fixed to the periphery of the upper and lower openings of the anode cylinder 1; an exhaust pipe having one end connected to the sealing metal via an insulating cylinder; and a sealing metal fixed to the sealing metal. A cathode tube for supporting the cathode terminal of the cathode body 2.

In this embodiment, the capacity of the annular magnet is increased,
In addition to the improvement of the magnetic material and the components constituting the magnetic circuit, the magnetic field strength is applied to a region higher than the magnetic field intensity so as to avoid the region of the magnetic field intensity at which the oscillation efficiency temporarily levels off or decreases.

That is, when many experiments were conducted in order to improve the oscillation efficiency of the magnetron, the magnetic field intensity was increased, and even if the oscillation efficiency of the magnetron was flat or decreased, the magnetic field intensity was further increased. Oscillation efficiency increases according to the theoretical expression of Expression (1). At this time, the magnetic field strength B (mT) is 27
It is calculated as the following equation (3) from an equation that gives an operation straight line when the potential distribution is proportional to the square of the anode radius on page 3.

[0022]

(Equation 4)

Here, σ: the optimal anode radius ratio (rc /
ra) ra: anode radius (mm) rc: cathode radius (mm) n: anode division number / 2 λ: wavelength (mm) Va: peak anode voltage (V).

In this embodiment, the dimension of the anode radius ra is 4.50 (mm) and the dimension of the cathode radius rc is 2.00.
(Mm), σ = rc / ra = 0.444, n (assuming that the number of anode divisions is 10) is 5, wavelength λ is 122 (mm), and peak anode voltage Va is 4000 to 5900 (V). From the above equation (3), the magnetic field intensity B is set to 180 to
257 (mT) was applied. As a result, as shown in FIG. 2, it was confirmed that the oscillation efficiency of the magnetron leveled off or decreased when the magnetic field intensity B was in the range of 203 to 218 (mT). Along, the oscillation efficiency increases.

Next, in the present embodiment, the magnetic field intensity B
In order to obtain a region of magnetic field strength that causes a phenomenon in which the oscillation efficiency temporarily levels off or decreases, the anode radius ra
Is 4.00 to 5.05 (mm) and the range of the cathode radius rc is 1.75 to 2.15 (mm), the maximum magnetic field strength B is 257 (mT) and the maximum peak is The anode voltage Va was examined over a wide range of 6910 (V). As a result, the oscillation efficiency initially increased almost gently along the theoretical curve, as in FIG. 2, but then dropped halfway, then increased sharply toward the theoretical curve, and then gradually again. It was confirmed that the temperature rose and approached the theoretical curve.

Accordingly, in the present embodiment, the size of the anode radius is increased so that the magnet capacity is increased and the magnetic material is improved, and the magnetic field strength is applied to a region beyond the region where the oscillation heat rate temporarily levels off or decreases. By setting the dimensions of the cathode radius, the peak anode voltage, the number of divided anodes, and the wavelength, a magnetron with high oscillation efficiency can be obtained.

Further, since the oscillation efficiency of the magnetron can be increased by increasing the magnetic field strength by improving the magnetic circuit, etc., a magnetron having a high oscillation efficiency is required in a world where energy saving and resource saving are required. Can be obtained.

[0028]

As described above, according to the present invention,
An increase in the oscillation efficiency can be achieved by increasing the magnetic field strength by improving the magnetic circuit such as the anode radius.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part of a magnetron according to an embodiment of the present invention.

FIG. 2 is an actual measurement example of a magnetron oscillation efficiency with respect to a magnetic field intensity.

FIG. 3 is a cross-sectional view illustrating a structural example of a conventional magnetron.

FIG. 4 is an enlarged view of a main part of the magnetron of FIG. 3;

FIG. 5 is a curve of theoretical electron efficiency with respect to magnetic field strength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode cylinder 2 Cathode 3 Bain 4 Antenna conductor 5 Inner strap ring 6 Outer strap ring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Nakai 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F-term (reference) 5C029 FF09 FF12

Claims (4)

[Claims] A cathode body disposed at a center of the anode cylinder;
A magnetron having an anode cavity formed around the cathode body. Even if the magnetic field strength is increased, a magnetic field given by the following formula is used so as to avoid a region where the oscillation efficiency of the magnetron is flat or decreases. The intensity B is the cathode radius rc
Is set based on the dimensions (mm), the dimensions (mm) of the anode radius ra, and the peak anode voltage Va (V). (Equation 1) Here, σ = rc / ra, the number of anode divisions / 2 is n, and the wavelength (mm) is λ. 2. The magnetron according to claim 1, wherein said magnetic field intensity B is 218 (mT) or more. 3. The range of the dimension of the anode radius ra is 4.0.
0 to 5.05 (mm), the range of the dimension of the cathode radius rc is 1.75 to 2.15 (mm), and the peak anode voltage Va is 69.
10 (V) or less, and the magnetic field density B is 218
2. The magnetron according to claim 1, which is (mT) or more. 4. The magnetron according to claim 3, wherein the number of anode divisions of the anode cylinder is 10.