JPS6026441Y2 - magnetron - Google Patents

Description

[Detailed explanation of the idea] This idea concerns improvements to magnetrons.

Conventionally, the main part (magnetic circuit) of a magnetron that uses ferrite magnets as permanent magnets is constructed as shown in FIG.
3, ferrite magnets 4 and 5 coaxially disposed outside the pole piece 2.3, and a yoke 6 that connects the magnets 4 and 5 are magnetically coupled.

By the way, in general, in a magnetron, the temperature of the excitation permanent magnet increases due to heat due to anode loss during operation.

As a result, the magnet operating point changes and the strength of the magnetic field applied to the electron action space decreases, resulting in a decrease in the anode operating voltage.

Conventionally, ferrite magnets have been generally used as excitation permanent magnets in magnetrons.

The reversible temperature coefficient of this magnet is -0.2%/°C. Therefore, in a magnetron in which a ferrite magnet is incorporated into a magnetic circuit, the anode operating voltage decreases significantly due to an increase in magnet temperature.

When such a magnetron is driven by a microwave oven power supply having a leakage transformer, as the magnetron's magnet temperature rises, the anode current increases due to the power supply characteristics.
This will cause a decrease in input power.

As a result, heat loss in the transformer and a decrease in output may occur due to an increase in current.

Furthermore, as the anode operating voltage decreases, the oscillation efficiency of the magnetron also decreases.

This idea was made in view of the above circumstances, and offsets the temperature characteristics of the magnet.

That is, by providing a means in the magnetic circuit that can keep the strength of the magnetic field in the electron action space constant, it is possible to provide a magnetron that can keep the anode operating voltage almost constant even when the magnet temperature increases. With the goal.

Hereinafter, one embodiment of this invention will be described in detail with reference to the drawings.

The main part (magnetic circuit) of the magnetron of this invention is constructed as shown in Figs. 2 and 3, and has a plurality of vanes (not shown) arranged radially inside the anode cylinder 10 at both open ends. , funnel-shaped pole piece structures 13 and 14, respectively.
is fixed.

A ferrite magnet 11 is placed on the outside of this pole piece structure ff.
．． 11 are arranged coaxially, and a yoke 12 is further arranged to connect the ferrite magnets 11, 11.

In the above case, the pole piece structures 13 and 14 each have high thermal expansion coefficient materials 17a and 18a in the vicinity of the electron working space S of the funnel-shaped pole piece main body 15 and 16 made of ferromagnetic material, and the one farther from the working space S The one closer to the working space S is the bimetal 17 made by joining the low thermal expansion coefficient materials 17b and 18b.
．． 18 is fixed.

At least one of the art materials 17a, 18a, 17b, and 18b is made of ferromagnetic material.

Now, during operation, when the magnetron oscillates, heat is generated due to anode loss. Although this heat is radiated by cooling fins (not shown) fixed to the anode cylinder, some of the heat is absorbed by the pole piece structure 13°■. is conducted to the ferrite magnet through the ferrite magnet.

Therefore, the magnetomotive force of the ferrite magnet decreases depending on its temperature characteristics.

However, since the bimetal 17.18 made of ferromagnetic material is fixed to the portion of the pole piece main body close to the working space, the bimetal 17.18 is bent toward the electron working space due to heat.

Therefore, the spacing between the pole piece structures including bimetal becomes substantially narrower, and as a result, the magnetic field strength in the electron working space becomes approximately constant by offsetting the decrease in the magnetic field strength in the working space due to the decrease in the magnetomotive force of the ferrite magnet.

Therefore, the anode operating voltage can be made approximately equal at room temperature and when a stable state is reached at high temperature.

Incidentally, FIGS. 4 and 5 show a modification of this invention, and the same effects as in the above embodiment can be obtained.

That is, the pole piece structures 19 and 20 each consist of funnel-shaped pole piece bodies 21 and 22, auxiliary rings 23 and 24, and bimetals 25 and 26.

Auxiliary rings 23, 24 protrude into the working space.

In FIG. 5, reference numeral 27 is a slit, and the other auxiliary ring 23 and bimetal 25 have the same structure as in FIG.

As explained above, according to this invention, since the bimetal containing ferromagnetic material is fixed to the working space side of the pole piece body, the distance between the electron working space becomes smaller as the temperature rises, and the ferrite magnet Even if the temperature of the anode increases, the strength of the magnetic field in the electron action space can be maintained approximately constant.As a result, the anode operating voltage can be maintained approximately constant.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the main parts of a conventional magnetron, Figure 2
The figure is a sectional view showing the main parts of a magnetron according to an embodiment of this invention, FIG. 3 is an enlarged view of the main part, FIG. 4 is a sectional view showing a modification of this invention, and FIG. It is a perspective view which extracted and showed a part. 10... Anode cylinder, 13 14 19 20.
...Pole piece structure, 15, 16, 21, 22
...Pole piece body, 17, 18, 25, 2
6...Bimetal, 17a, 18a...
・High expansion coefficient material, 17b, 18b...Low expansion coefficient material, 11...Ferrite magnet, 12------
yoke.

Claims (1)

[Claim for Utility Model Registration] A funnel-shaped pole piece is fixed to the open end of an anode cylinder in which a plurality of vanes are arranged radially inside, and a ferrite magnet is magnetically bonded to the outer surface of the pole piece. In the magnetron, a bimetal is fixed to a portion of the pole piece near the electron working space, and the bimetal is made of a material with a low coefficient of thermal expansion near the working space and a material with a high coefficient of thermal expansion far from the working space, and A magnetron characterized in that at least one of the bimetallic low thermal expansion coefficient material or high thermal expansion coefficient material is composed of a ferromagnetic material.