KR940006869Y1 - Magnetron of electric range - Google Patents

Abstract

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Description

Microwave Magnetron

The present invention relates to a vane forming a cavity resonant portion of a magnetron anode in a microwave oven. In particular, a non-uniform magnetic flux density and discontinuousity formed at the upper and lower ends of the vanes by cutting the angles of the upper and lower ends of the vanes obliquely. It is possible to ensure stable operation by avoiding the former motion region and to reduce unnecessary radiation waves leaking into the input terminal.

The structure of a general magnetron is shown in FIGS. 1 and 2.

Here, as shown in Fig. 1, even vanes 14 are arranged radially on the inner circumferential surface of the cylindrical anode body 15, and grooves are formed on the upper and lower ends of the vanes 14 to form a ring-shaped metal ring 14a, 14b) is inserted but the straps 14a and 14b and the vanes 14 are electrically contacted one by one.

An antenna rod 13 having a metal rod shape is connected to an upper end of any of the vanes 14 so that the antenna lead 13 penetrates on the axis of the cylindrical ashe 18 and the antenna ceramic 12 made of metal. do.

The vane 14 has a rectangular shape as shown in FIG. 2, and the edges of the ends adjacent to the centerline of the anode body 15 were angled at right angles.

And, on the upper and lower surfaces of the vane 14, the magnetic poles (16, 17) are symmetrically configured to be in contact with the asheel (18) and F-sheal (19) and are connected to the upper and lower ends of the anode body (15). Its interior is to maintain a vacuum tightness.

In addition, the upper end shield 20, the filament 21, and the lower shield 22, which are cathodes, are positioned on the center line of the cathode body 15, and metal rod-shaped side leads 23 and center leads 24 for supporting them are provided. ) Is electrically connected to the terminal 26 which is an input terminal through the metal cylindrical f shield 19 and the insulating ceramic 25. The magnetic poles 16 and 17 are connected to the permanent magnet 28 and the yoke 27 with the ashele 18 and the fushle 19 interposed therebetween to form a magnetically closed circuit.

Therefore, as shown in FIG. 2, which shows the coupling relationship between a predetermined vane and a strap through the side lead 23 and the center lead 24 on the filament 21, the inner peripheral surface of the cylindrical anode body 15 is shown in FIG. Even vanes 14 are arranged radially and grooves are formed at the upper and lower ends of the vanes 14 to insert the straps 14a and 14b, which are ring-shaped metal rings, to the straps 14a and 14b and the vanes 14. Are electrically contacted one by one.

An antenna rod 13 having a metal rod shape is connected to an upper end of any of the vanes 14 so that the antenna lead 13 penetrates on the axis of the cylindrical ashe 18 and the antenna ceramic 12 made of metal. do.

The vanes 14 have a rectangular shape, and the edges of the ends adjacent to the center line of the anode body 15 are formed at right angles.

And, on the upper and lower surfaces of the vane 14, the magnetic poles (16, 17) are symmetrically configured to be in contact with the asheel (18) and F-sheal (19) and are connected to the upper and lower ends of the anode body (15). Its interior is to maintain a vacuum tightness.

In addition, the upper end shield 20, the filament 21, and the lower shield 22, which are cathode parts, are positioned on the center line of the positive electrode body 15, and metal rod-shaped side leads 23 and center lids 24 for supporting them are provided. ) Is electrically connected to the terminal 26 which is an input terminal through the metal cylindrical f shield 19 and the insulating ceramic 25.

The magnetic poles 16 and 17 are connected to the permanent magnet 28 and the yoke 27 with the ashele 18 and the fushle 19 interposed therebetween to form a magnetically closed circuit.

Therefore, a large amount of hot electrons are emitted from the filament 21 when a constant current is supplied to the filament 21 through the side lead 23 and the center lead 24 to maintain the temperature of the filament at about 2000 ° K.

At this time, the DC high voltage (approximately 4KV) and the permanent magnet 28 and the magnetic poles 17 applied between the filament 21 and the vane 14 in the working space 33 formed between the filament 21 and the vane 14. The working space 33 and the yoke 27 form a magnetic closure circuit, and the hot electrons are rotated in the working space 33 by receiving the DC high voltage and the magnetic force at the same time.

In addition, between the vanes 14 and the vanes 14, a high frequency electric field is generated by the cavity resonance. In general, in the microwave magnetron, the high frequency electric field has a frequency of 2450 MHz, and the rotational speed of the electron and the high frequency electric field When the phase velocity is synchronized, the energy of the electron is given to the high frequency electric field, thereby obtaining microwave energy.

This energy is drawn out through the antenna lead 13 which is connected to one end of the vane 14.

At this time, the frequency of the microwave drawn out is about 2450 + 10 (MHz) and the microwave energy vibrates water molecules such as food to heat food.

However, in the conventional Marknetron as described above, the upper part of the filament 21, which is the cathode part, is fixed to the upper end shield 20, and the lower part is fixed to the lower end shield 22, and at the same time, the side lead 23 and the center lead are And heat generated from the filament 21 is conducted through the upper end shield 20 and the lower end shield 22, the center lead 24, and the side leads 23, so that the center portion of the filament (center) Turn (TRUN part) is higher than the turn part of the filament near the upper end shield 20 and the lower end shield 22. That is, in the filament 21, since the temperature of the upper and lower portions is lower than the temperature of the central portion, the amount of hot electron radiation is relatively smaller than that of the central portion.

This phenomenon can also be confirmed by the RIECHARDSON-DUSHMAN equation.

That is, Js = AT ² e (-Ø / KT) (A / ㎠)

Js: Saturation Current Density (A / ㎠)

A: DUSHMAN constant

T: Temperature of cathode (° K)

Ø: WORK FUNCTIOM (e, v)

K: BOLTZMAN constant (8.6 × 10 ^-5 ev / ° K)

According to the above equation, it can be seen that the thermal electron emission amount is different when the temperature distribution of the filament 21 is different.

Therefore, in the magnetron operation, the hot electrons reaching the anode 14, which is the anode, are relatively smaller than the center portion at the top or the bottom of the vane.

In addition, since the upper and lower portions of the vanes 14 are larger than the central portion, the magnetic flux density formed in the working section 33 also reduces the number of hot electrons that reach the vanes 14, and thus the region for normal high frequency oscillation ( MOB: MODE BOUNDARY (represented as the value of the anode current) is reduced.

Since the magnetic flux density distribution is large as described above, the frequency synchronized with the electron surroundings when the electrons move is determined by the following equation.

here,

b: 0,1,2,3 .... rc: radius of cathode

e: charge amount of electron Eb: anode voltage

B: magnetic flux density ra: radius of anode

m: mass of electron σ: re / ra

The constant frequency acts as a noise that is restricted from being used in the microwave oven, so it leaks into the input stage.

The present invention is intended to provide a means for improving the operational stability and reducing the unnecessary noise generation frequency band despite the non-uniform temperature of filament and the non-uniformity of hot electron radiation or magnetic flux density.

The present invention is to reduce the area of the top and bottom of the vane by obliquely cutting the upper and lower ends of the vanes facing the filament at a right angle for this purpose to reduce the cavity resonance frequency, as described in detail according to the accompanying drawings Same as

3 is a view showing the form of the vane of the present invention in detail, a radial vane 14 is fixed radially to the inner circumferential surface of the positive electrode body 15, and the upper and lower portions of the vane 14 are softer in the working space. , The inclined surfaces 14c and 14d are formed by cutting the edges of the lower end portions obliquely.

As mentioned above, d and h, the dimensions of the inclined cut portion, have various dimensions according to electrical characteristics such as microwave power, efficiency, anode voltage, or anode current, but h is 1.0 mm to 1.2 mm and 0.8 mm to 1.0 mm. It shows a good state of noise and operational stability (MOB) in the range.

Such action and effects of the present invention are as follows.

Since the inclined surfaces 14c and 14d are formed at the upper and lower ends of the vanes 14, the area of the upper and lower ends of the vanes 14 decreases the cavity resonance frequency, and the frequency increases when the inner diameter of the strap decreases. 14d) reduces the inner diameters of the straps 14a and 14d to maintain the normal oscillation frequency of 2450 MHz.

Therefore, the electron beam radiated from the filament 21, which is the cathode part, is collected toward the center of the vane 14, thereby avoiding the movement of the electron at the position where the magnetic flux density is nonuniform in the working space, and at the position where the electron emission amount is relatively small. Since the motion is avoided, the stable motion area (MOB) of the magnetron is improved.

In addition, the operation in the direction where the magnetic flux density is too high is avoided to narrow the frequency range synchronized with the electron surroundings, thereby reducing the area of unnecessary noise.

The present invention has the effect of improving the stability (MOB) from 500 to 500 (mA) at 450 to 500 (mA), and the unnecessary noise generation frequency band from 200 to 380 (MHZ) at 200 to 450 (MHZ). There is also an advantage to be reduced.

Claims (1)

In the magnetron formed with a plate-shaped vane 14 disposed radially on the inner circumferential surface of the metal cylindrical anode body 15, the end of the vane 14 that is soft in the working space 33 in the upper and lower portions of the vane 14. A magnetron for a microwave oven, characterized by comprising an inclined surface portion (14c, 14d) which reduces the unnecessary noise while reducing the stable operation area (MOB) of the magnetron by cutting the negative right angled surface inclined.