JPH04121932A - Magnetron for microwave oven - Google Patents

Abstract

PURPOSE:To prevent deformation or rupture in a high-output oscillation action by forming strap rings and an antenna lead with a deposition hardening type metal constituted of zirconium and oxygen at a specific ratio and copper for the remainder. CONSTITUTION:Multiple vanes 23 are radially arranged on the inside of an anode cylinder 22 constituting an oscillation section main body 21 to form a cavity resonator. Every other vanes 23 are connected together with a pair of large and small strap rings 24 at the upper and lower end sections. One end section of an output antenna lead 31 is electrically connected to one vane 23, the antenna lead 31 penetrates the through hole of a pole piece 29 and is extended in an output section 43 along the tube axis, and the other end section is pinched and fixed by an exhaust pipe 40. The strap rings 24 and the output antenna lead 31 are made of a deposition hardening type metal constituted of zirconium 0.005-0.3wt.%, oxygen 30ppm or below and copper for the remainder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetron for a microwave oven, and particularly to improvements in the materials of its strap ring and output antenna lead.

(Prior Art) In general, oxygen-free steel is used for the members constituting the cavity resonator in magnetrons for microwave ovens. Precipitation hardening metals with added zirconium (Z'') have come to be used in strap rings.

By the way, as a recent trend in microwave ovens, the microwave output is increasing from about 500W to about 700W. Furthermore, there is a movement to increase output to 100 OW with the same size as before, and conventional oxygen-free copper and partially zirconium-containing steel materials are no longer able to withstand the thermal stress that occurs.

This problem could be solved by increasing the size of the tube, but it would require a huge amount of cost to update the manufacturing equipment and increase the amount of parts used. Furthermore, for a microwave oven equipped with a magnetron, if high output can be achieved with the conventional oven volume, the added value is great, so there is a great advantage in making the magnetron more compact and increasing output.

(Problems to be Solved by the Invention) As is clear from the above, when a life test was conducted on a conventional tube assuming an output of 1000 W, each member could not withstand the thermal stress, causing the strap ring to break, the vane to break, and the output antenna lead to break. It will break and break down in a very short time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetron for a microwave oven that is capable of high-output oscillation without breaking the strap ring, vane, or output antenna lead, and with the same size as a conventional tube.

[Structure of the Invention (Means for Solving the Problems) This invention provides a strap ring and an output antenna lead that are precipitation-hardened, containing 0.005 to 0.3% by weight of zirconium, 30 ppM or less of oxygen, and the balance being copper. This is a microwave oven magnetron made of metal.

(Function) According to the present invention, even in the case of high-output oscillation operation, breakage of the strap ring, vane, and output antenna lead is prevented.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

A microwave oven magnetron that generates a fundamental wave in the 2450 MH band to which this invention is applied is constructed as shown in FIG. It is arranged as a cavity resonator.

The upper and lower ends of each vane 23 are connected to each other by a pair of large and small strap rings 24, respectively. In the electron action space surrounded by the inner free ends of the plurality of vanes 23,
A helical filament cathode 25 is disposed along the axis of the anode cylinder 22, and its ends are secured to end shields 26, 27, respectively. Further, substantially funnel-shaped pole pieces 29 and 30 are fixed to both ends of the anode cylinder 22, and a cylindrical metal container 32 and 33 is attached to each pole piece 29 and 30, respectively. are attached and fixed.

A sealing ring 44 having a half-section U-shape is hermetically welded between the open end of one metal container 32 and the ceramic cylinder 38 constituting the high-frequency output section. It is hermetically sealed to the lower end of 38. Further, a retaining ring 41 is hermetically sealed to the upper end surface of the ceramic cylinder 38. An output metal cap 42 is fixed to the side surface of the retaining ring 41, and the retaining ring 41
A metal exhaust pipe 40 is hermetically sealed and held at the inner bent portion. Output antenna lead 31 to one of the vanes 23
One end of the antenna lead 31 is electrically connected to the antenna lead 31.
passes through the through hole of the pole piece 29 and extends inside the output portion 43 along the tube axis, and the other end is clamped and fixed to the exhaust pipe 40.

Permanent magnets 34 are attached to the outer peripheries of the metal containers 32 and 33, respectively.
．． 35 are provided. Further, a yoke 36 made of a ferromagnetic material is provided so as to surround the permanent magnets 34, 35, the anode cylinder 22, the cooling fins 37 attached to the outer periphery of the anode cylinder 22, and the like. A gasket ring 39 is provided between the center hole of the yoke 36 and the sealing ring 44 .

Now, in the above case, the material of both the strap ring 24 and the output antenna lead 31 is 0.005 to 0.3% by weight of zirconium and 30 PPM or less of oxygen.
The remainder consists of copper precipitation hardening metal. More preferably, zirconium is in the range of 0.05 to 0.15
The weight percent oxygen ranges from 5 PPM to 20 PPM or less. As a specific example, zirconium is 0.075% by weight
, oxygen is IOPPM. In addition, if necessary, a highly conductive material such as pure copper or silver is coated on the surface of the output antenna lead 31.
The coating is applied to a thickness of 3 μm to 3 μm.

The inventor conducted various life tests with and without zirconium-containing steel in the vane 23, strap ring 24, and output antenna lead 31, and found the following.

■ If only the vane 23 is made of steel containing zirconium, the vane 23 is too strong and has an extremely short life.

■ If zirconium gets into the vane 23 and strap ring 24, the strap ring 24 will break.

■ Without zirconium in the vane 23, tests of various operating modes result in a practical level.

■ If zirconium is inserted into the output antenna lead 31,
It is effective alone and prevents creases.

In summary, as described above, in the present invention, both the strap ring 24 and the output antenna lead 31 are made of zirconium-containing steel material.

Furthermore, since a large microwave current flows through the output antenna lead 31, if the surface is coated with a highly conductive material such as pure copper or silver to a thickness of 2 to 3 μm, which corresponds to the skin effect, as described above, some of the zirconium-containing steel material It has been found that this method is even more desirable because it can compensate for the decrease in conductivity and the increase in high frequency resistance due to the zirconium surface oxidation layer.

Now, compared to conventional products that use pure copper for the strap ring and output antenna lead, the magnetron of this invention has the following advantages:
Operation stability has been significantly improved.

That is, as shown in FIG. 2, the operating time required for the magnetron of the present invention to exceed the level at which the deviation in oscillation frequency occurs is approximately 2, compared to the conventional magnetron (curve B) as shown by curve A. This shows that it can be doubled. The graph shown in FIG. 2 is a result of a forced test in which the test magnetron was attached to a microwave oven and the power input was turned on for 3 minutes and turned off for 1 minute. The horizontal axis shows the value obtained by changing the maximum temperature of the inner strap ring. Note that this temperature is a value derived by calculation from the actually measured temperature of the anode cylinder. The vertical axis represents the time when the deviation of the oscillation frequency (2450 MHz band) reached 10 MHz compared to the initial stage of operation. When the strap ring or output antenna lead is deformed or broken, the oscillation changes gradually or abruptly, and the degree of deformation or local breakage can be estimated from the amount of change in frequency.

As is clear from the results shown in FIG. 2, the time required for the strap ring or output antenna lead to deform or break to the same extent for both the conventional magnetron and the present invention is longer for the magnetron of the present invention than for the conventional magnetron. It is clear that the improvement is about twice that of the standard magnetron. still,
The data shown in the figure was compared in a forced test under high input, no load, or similar conditions, which are much harsher than the operating conditions of a normal microwave oven.

[Effects of the Invention] As explained above, according to the present invention, the strap ring and the antenna lead are made of a precipitation hardening metal containing 0.005 to 0.3% by weight of zirconium, 30 ppM or less of oxygen, and the balance being copper. Therefore, deformation or breakage is prevented even during high-power oscillation operation.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing a microwave oven magnetron according to an embodiment of the present invention, and Fig. 2 shows a difference in strap ring temperature and oscillation frequency of the conventional example and the microwave oven magnetron of the present invention reaching 10 MHz. It is a characteristic curve diagram showing the relationship with time. 22... Anode cylinder, 23... Anode vane, 24...
・Strap ring, 1... Output antenna lid.

Claims (1)

[Claims] A plurality of anode vanes are arranged radially inside the anode cylinder, and every other anode vane is connected by a strap ring, and an output antenna lead is led out from one of the anode vanes and inserted into the output section. In the extended microwave oven magnetron, the strap ring and the output antenna lead are
In both cases, zirconium is 0.005 to 0.3% by weight,
A magnetron for a microwave oven, characterized in that it contains 30 ppM or less of oxygen and the remainder is made of a precipitation hardening metal of copper.