JPH0668804A - Magnetron - Google Patents

Abstract

PURPOSE:To prevent the lowering of output due to the demagnetization of permanent magents. CONSTITUTION:First and second ring permanent magnets 4 and 5 are provided on respective external ends of a pair of pole pieces 2 and 3 in a magnetron 1. Both permanent magents 4 and 5 are connected in series to each other by means of a frame-like yoke 12, and a filter case 7 is provided on the bottom plate part of the frame-like yoke 12, while providing many radiating fins in multistage fashion on the external periphery of an anode cylindrical body 9. A recessed groove 13 is provided on the external end of the frame-like yoke 12 so as to form a communicating path for a cooling air-stream between the filter case 7 and it. Accordingly, a cooling air-stream can be guided to flow through not only between plates of the radiating fins, but also between the frame-like yoke and the filter case. In addition, since this air-stream also touches the metallic tube part connecting the anode cylindrical body to the stem part in the magnetron, the demagnetization due to the temperature rise of the permanent magnet can be effectively suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forced air cooling type magnetron device used for microwave heating equipment such as a microwave oven.

[0002]

2. Description of the Related Art Generally, a magnetron device used in a microwave heating device such as a microwave oven is constructed as shown in FIG. That is, the first and second annular permanent magnets 4 and 5 provided on the outer end surfaces of the pair of magnetic pole pieces 2 and 3 of the magnetron 1 are made of ferrite, and each of them has one magnetic pole S or N. It is magnetically coupled to the pole piece. The other magnetic poles are magnetically coupled by the frame yoke 6. As a result, the first and second annular permanent magnets 4, 5 are connected in series between the magnetic pole pieces 2, 3 of the magnetron 1. The filter case 7, which is fixed on the bottom plate of the frame-shaped yoke 6 having a square cross section, accommodates the cathode terminal lead-out stem of the magnetron 1 and the choke coil that is a filter circuit element, and the through-type capacitor 8 Is attached to the side wall. A large number of heat radiation fins 10 are mounted in multiple stages on the outer peripheral surface of the anode cylinder 9 of the magnetron 1. Reference numeral 11 denotes an electromagnetic wave emission terminal.

In the conventional magnetron device having such a structure, an electric fan (not shown) rotates with the start of operation of the device, and the forced air-cooling airflow sent from the fan rotates across the plates of the heat radiating fins 10 onto the paper surface. It distributes in a right angle direction. Therefore, the permanent magnets 4 and 5 are heated to a high temperature, and the coercive force is reduced.

[0004]

However, the size and the number of the radiation fins 10 that can be used are naturally limited, and no matter how efficiently the air-cooling airflow is circulated, the heat generated in the magnetron 1 causes the annular permanent magnets to be generated. The temperature of 4,5 rises, sometimes irreversible demagnetization occurs, and the output drops.

[0005]

According to the present invention, a concave groove for circulating an air-cooling airflow is provided between the frame yoke and the filter case on the outer end surface of the bottom plate portion of the frame yoke.

[0006]

According to this structure, the air-cooling airflow flows not only between the plates of the radiation fins but also between the frame-shaped yoke and the filter case, and further flows between the frame-shaped yoke and the filter case. Since the air-cooling air flow contacts the metal tube portion that connects the anode cylinder of the magnetron and the stem portion, that is, the high temperature portion, an effective cooling action can be obtained. In addition, the airflow that has entered this portion also flows into the second annular permanent magnet side, so that the effect is further enhanced.

[0007]

The present invention will be described below with reference to the embodiments shown in the drawings. The configuration shown in FIG. 1 differs from the configuration shown in FIG. 3 in that the frame yoke 12 has a concave groove 13 in its bottom plate portion, and that an air cooling airflow is circulated in the concave groove 13. There is no difference in other configurations. However, the recessed groove 13 extends from one opening of the frame yoke 12 in a direction leading to the other opening, that is, in a direction perpendicular to the paper surface. be able to.

The recessed groove 13 forms a flow passage for the air cooling air flow between the bottom plate portion of the frame yoke 12 and the filter case 7. The air cooling air flow sent into this flow passage is a plate of a radiation fin. It was created by a common electric fan along with the airflow for air cooling sent in between.

As shown in FIG. 2, the air-cooling airflow sent through the concave groove 13 not only contacts the metal tube portion 15 extending from the anode cylinder 9 of the magnetron 1 to the stem portion 14, but also the second annular permanent member. It also goes inside the magnet 5. Therefore, in particular, the temperature rise of the second annular permanent magnet 5 can be further suppressed.

[0010]

As described above, according to the present invention, the air-cooled airflow can be made to flow not only between the plates of the radiation fins but also between the frame yoke and the filter case, and moreover, the anode cylinder of the magnetron and the stem. Since the airflow is also in contact with the metal tube portion connecting the parts, it is possible to effectively suppress the demagnetization due to the temperature rise of the permanent magnet, and to prevent the output reduction due to the demagnetization of the permanent magnet.

[Brief description of drawings]

FIG. 1 is a side view of a magnetron device embodying the present invention.

FIG. 2 is a sectional view of the main part of the same device.

FIG. 3 is a side view of a conventional magnetron device.

[Explanation of symbols]

 1 Magnetron 2 Magnetic pole piece 3 Magnetic pole piece 4 Annular permanent magnet 5 Annular permanent magnet 7 Filter case 9 Anode cylinder 10 Radiating fin 12 Frame-like yoke 13 Recessed groove

Claims (1)

[Claims] 1. A first and a second annular permanent magnet, which are provided on each outer end surface of a pair of magnetic pole pieces of a magnetron so as to be overlapped with each other, and one of the magnetic poles is magnetically coupled to the magnetic pole piece. 1
And a frame yoke for magnetically coupling the other magnetic poles of the second annular permanent magnet, a stem portion for fixing the magnet terminal to a cathode terminal, which is fixed on the bottom plate portion of the frame yoke, A filter case that houses a filter circuit element, and heat radiation that is provided in multiple stages on the outer peripheral surface of the anode cylinder of the magnetron and that allows an air-cooling airflow that flows from one opening of the frame yoke to the other to flow between the plates. With fins,
A magnetron device characterized in that a concave groove for circulating an air-cooling airflow is provided between the frame yoke and the filter case on an outer end surface of the bottom plate portion.