JPH0673279B2 - Magnetron for microwave oven - Google Patents

Description

The present invention relates to a magnetron for a microwave oven, and more particularly to a thermal demagnetization countermeasure structure for a permanent magnet.

(Prior Art) Conventionally, in a magnetron for a microwave oven, an output section and a cathode stem are projected from both ends of a copper anode cylinder that constitutes the main body of the oscillation section via metal sealing bodies. A ring-shaped permanent magnet is closely fitted and arranged around each metal sealing body. In this case, a small projection is provided on the flange portion of the metal sealing body joined to the anode cylinder, and the small projection prevents the permanent magnet from sticking to the flange portion of the metal sealing body. Prevents heat conduction to the magnet. Further, a plurality of aluminum radiator plates are heat-conductively joined to the outer circumference of the anode cylinder. Further, a magnetic yoke is magnetically connected to form a magnetic circuit, and a ferromagnetic yoke is arranged so as to surround the metal sealing body, the oscillator main body, the permanent magnet, the heat radiating plate and the like. A gasket contact ring is coupled to the output side end of the metal sealing body, and an annular gasket is provided between the gasket contact ring and the opening of the yoke and is held by the gasket contact ring.
The gasket is for maintaining electrical connection between the output part of the magnetron and the oven of the microwave oven, and is composed of a ring made of thin wires of brass or stainless steel.

(Problems to be Solved by the Invention) In the conventional magnetron for a microwave oven as described above, in operation, the heat generated in the anode cylinder is efficiently radiated by the heat radiating plate, but a part of the metal seal on the output side is used. It is transmitted to the body of the body and is also transferred to the permanent magnets to some extent. Since the metal sealing body is made of pure iron in the recent magnetron for microwave ovens, the heat conduction is good, and even the metal sealing body separated from the anode cylinder has a considerably high temperature.

By the way, although ferrite is usually used as the permanent magnet, the temperature rises due to heat transfer from the anode cylinder and the metal sealing body, and the magnetic force rapidly decreases. Further, since the yoke is close to the oven, the temperature is relatively low. In recent microwave ovens, the cooling blower air is directed more toward cooling the transformer than cooling the microwave oven magnetron, and along with the downsizing of the magnetron, the temperature of the magnetron rises rapidly from the beginning of operation. Tend to do.

At this time, the temperature of the permanent magnet rises sharply on the side of the anode cylinder, but the phenomenon of being cold on the side of the yoke occurs, and due to the poor heat conduction of ferrite and the property of being hard but brittle, it resists the difference in the amount of expansion between the hot and cold parts. There is a risk that the permanent magnet will break without being completely cut.

An object of the present invention is to provide a magnetron for a microwave oven in which thermal demagnetization of a permanent magnet is suppressed, magnet cracking is prevented, and reliability is improved.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, the outer peripheral surface of the gasket contact ring is set to have a larger diameter than the metal sealing body, and the central hole of the permanent magnet has a larger inner diameter on the oscillator body side. The magnetron for a microwave oven has a small inner diameter and is fitted close to the gasket contact ring.

(Operation) According to the present invention, heat conduction from the anode cylinder is reduced, and heat conduction from the metal sealing body is also reduced. As a result, thermal demagnetization of the permanent magnet is suppressed. Further, the temperature difference between the side surface of the yoke of the permanent magnet, the side surface of the anode cylinder, and the inside of the metal sealing body is reduced, and cracking of the permanent magnet is prevented. Further, it is easy to center the permanent magnets and prevent the displacement thereof.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

The magnetron for a microwave oven according to the present invention is constructed as shown in FIG. 1, and the output section 3 and the cathode stem (the cathode stem ( (Not shown). An annular permanent magnet 4 made of ferrite is closely fitted and arranged around each metal sealing body 2. Further, a plurality of aluminum heat dissipation plates 6 are thermally conductively bonded to the outer circumference of the anode cylinder 5. Further, a ferromagnetic yoke 7 which is magnetically connected to the permanent magnet 4 and constitutes a magnetic circuit is arranged so as to surround the oscillator body 1, the metal sealing body 2, the permanent magnet 4, and the heat dissipation plate 6. Has been done. A gasket contact ring 8 is coupled to the output side end of the metal sealing body 2, and an annular gasket 9 is fitted and held between the gasket contact ring 8 and the opening 7a of the yoke 7.

In this case, as is apparent from the drawing, the diameter D ₁ of the outer peripheral surface of the gasket contact ring 8 is set to be larger than the outer diameter dimension D ₂ of the metal sealing body 2, and the difference in the diameter is, for example, 1.0
It is set in the range of ~ 1.5mm. As a result, a relatively large space S is formed between the central hole 4a of the permanent magnet 4 and the metal sealing body 2. The small protrusions 2a provided on the flange portion of the metal sealing body 2 are formed in a height range of 0.7 to 1.0 mm.

Further, the central hole 4a of the permanent magnet 4 is formed such that the inner diameter of the oscillation body 1 is large and the inner diameter of the gasket 9 is small. In other words, it is tapered and the difference in inner diameter is 2.5
It is set in the range of ~ 3.0mm. In this permanent magnet 4, the small diameter portion of the central hole 4a is fitted close to the gasket contact ring 8.

In the figure, reference numeral 10 is an anode vane, 11 is a cathode, 12 is a pole piece, 13 is an output antenna lead, 14 is a harmonic choke tube, 15 is an insulating tube, 16 is an exhaust pipe, 17 is an output cap, and 18 is It represents a ferromagnetic shim plate.

According to the present invention, the gasket contact ring is set to have a larger diameter than the metal sealing body, and the central hole of the permanent magnet has a larger inner diameter on the oscillator body side and a smaller inner diameter on the gasket side. Since it is fitted close to the gasket contact ring, the metal sealing body and the permanent magnet are reliably separated, thermal demagnetization of the permanent magnet is suppressed, magnet cracking is prevented, and reliability is improved. To do.

Further, since the gasket contact ring and the small diameter portion of the central hole of the permanent magnet are closely fitted, the center of the permanent magnet can be naturally aligned and the assembling accuracy is improved.

That is, the results of measuring the thermal demagnetization by the conventional magnetron and the magnetron of the present invention are shown in Table 1 below, which clearly shows that the present invention is excellent.

However, air volume: 800 l / min for 15 minutes

[Brief description of drawings]

FIG. 1 is a sectional view showing a magnetron for a microwave oven according to an embodiment of the present invention. 1 ... Oscillator body, 2 ... Metal seal, 3 ... Output unit,
4 ... Permanent magnet, 5 ... Anode cylinder, 7 ... Yoke, 8 ...
… Gasket contact ring, 9 …… Gasket.

Claims (1)

[Claims] 1. An oscillator main body having an output portion projectingly provided via a metal sealing body, an annular permanent magnet disposed around the sealing body, and a magnetic element magnetically connected to the permanent magnet. A gasket is formed between a yoke made of a ferromagnetic material that constitutes a circuit and surrounds the sealing body, the body of the oscillating unit, a permanent magnet, etc., and an opening of the yoke that is coupled to the output side end of the sealing body. In a magnetron for a microwave oven having a gasket contact ring for holding, the outer peripheral surface of the gasket contact ring is set to have a diameter larger than that of the metal sealing body, and the central hole of the permanent magnet has an inner diameter on the oscillator body side. A magnetron for a microwave oven, characterized in that the gasket side has a small inner diameter and is fitted close to the gasket contact ring.