Magnetron

Details Magnetron Magnetron

2003-02-25

2004-04-06

Vu, David (Department: 2821)

Electric lamp and discharge devices: systems

Combined load device or load device temperature modifying...

Distributed parameter resonator-type magnetron

C315S039530, C315S039710

Reexamination Certificate

active

06717365

ABSTRACT:

This application claims the benefit of the Korean Application Nos. P2002-21231, and P2002-21232, both filed on Apr. 18, 2002, which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetron having an improved self-cooling performance.
2. Background of the Related Art
In general, the magnetron has applications in microwave ovens, plasma lighting fixtures, dryers, and other microwave systems.
The magnetron, a kind of vacuum tube, emits a thermal electron from a cathode thereof as a power is applied thereto, and the thermal electron emits a microwave by action of strong electric, and magnetic fields. The microwave is forwarded through an antenna, or a feeder, and used as a heat source for heating an object.
In general, the magnetron is provided with an oscillating part and a magnetic circuit part for generating the microwave, an input part for receiving and providing a power to the oscillating part, an output part for forwarding the microwave generated by the oscillating part and the magnetic circuit part, and a cooling part for cooling the magnetron, of which detailed system will be described with reference to FIG.
1
.
FIG. 1
illustrates a related art magnetron.
Referring to
FIG. 1
, there are elements of the input and output parts in upper and lower parts of a yoke
1
which forms a magnetic closed circuit as a part of the magnetic circuit part, and there are elements of the oscillating part and the magnetic circuit part inside of the yoke
1
.
The oscillating part has an anode
11
and a cathode
16
. As shown in
FIG. 1
, the anode
1
is cylinder fitted to a center of the yoke
1
. On an inside surface of the anode
11
, there are a plurality of vanes
15
fitted in a radial direction toward a center of the anode
11
, to form a interaction space
15
a
at the center of the anode
11
the vanes
15
and spaces between the vanes
15
inside of the anode
11
form resonance cavities. There is a cathode
16
of a filament fitted in the interaction space
15
a
, with a center lead
17
a
and a side lead
17
b
for receiving a power.
The magnetic circuit part is provided with one pair of magnets
12
a
and
12
b
, one pair of magnetic poles
13
a
and
13
b
, and a yoke
1
. As shown in
FIG. 1
, there is one pair of magnets
12
a
and
12
b
; an upper magnet
12
a
over the anode
11
and a lower magnet
12
b
under the anode
11
. Both the upper magnet
12
a
and a lower magnet
12
b
are hollow, each for leading an antenna feeder
32
, a center lead
17
a
, and a side lead
17
b
to outward. There are also one pair of magnetic poles
13
a
and
13
b
; an upper magnetic pole
13
a
between an upper side of the anode
11
and the upper magnet
12
, and a lower magnetic pole
13
b
between a lower side of the anode
11
and a lower magnet
12
b
. The upper magnetic pole
13
a
and the lower magnetic pole
13
b
is fitted perpendicular to axes of the anode
11
and the cathode
16
. The yoke
1
has a yoke upper plate
1
a
and a yoke lower plate
1
b
, which are joined together to form the magnetic closed circuit.
In the meantime, for keeping an air tightness and vacuum of the inside space of the magnetron, the magnetron is provided with components, such as an A seal
14
a
, F seal
14
b
, an upper end shield
18
a
, and a lower end shield. The A seal
14
a
, and the F seal
14
b
of cylindrical metal containers are fitted between a top part of the anode
11
and the output part, and a bottom part of the anode
11
and the input part, for maintaining sealing. For fitting the A seal
14
a
and the F seal
14
b
as shown in
FIG. 1
, it is required that the upper magnet
12
a
and the lower magnet
12
b
are inserted to outer circumferential surfaces of the A seal
14
a
and the F seal
14
b
respectively. An opened bottom part of the F seal
14
b
is closed by a ceramic stem
21
. As shown in
FIG. 1
, the upper end shield
18
a
and the lower end shield
18
b
are also fitted to top and bottom ends of the cathode
16
.
The input part has a condenser
23
and a choke coil
23
a
. For preventing leakage of the microwave from the oscillating part, and protecting the choke coil
23
a
and a ceramic system
21
, there is a filter box
22
fitted under the yoke
1
where the input part is fitted. There is a condenser
23
at one side of the filter box
22
, and the choke coil
23
a
is fitted inside of the filter box
22
so as to be connected with the condenser
23
. There are one pair of external connection leads
23
b
from the choke coil
23
a
, passed through a ceramic system
21
and connected to the center lead
17
a
and the side lead
17
b.
The output part has an antenna feeder
32
, an A ceramic
31
, an antenna cap
33
. The antenna feeder
32
has one end connected to the vane
15
, and the other end extended trough the magnet
12
to an outer upper side of the yoke
1
. As shown in
FIG. 1
, the A fitted to top of the A seal
14
a
, and the antenna cap
33
is on the A ceramic
31
, surrounding an end of the antenna feeder
32
.
The cooling part
34
has cooling fins
34
and a cooling fan (not shown). The cooling fin
34
has one end connected to an outside surface of the anode
11
, and the other end connected to an inside surface of the yoke
1
. The cooling fan is fitted to an outside of the yoke
1
for blowing external air toward the yoke
1
. To do this, there are an inlet (not shown) and an outlet (not shown) in an outside case (not shown) of the magnetron for drawing and discharging the external air therethrough by using the cooling fan.
The operation of the magnetron will be described.
When power is provided to the oscillating part through the input part, thermal electrons are emitted from the cathode
16
to the interaction space
15
a
, where a magnetic field formed by one pair of the magnets
12
a
and
12
b
is focused through the one pair of magnetic poles
13
a
and
13
b
. According to this, the thermal electrons in the interaction space
15
a
are made to circulate by the magnetic field, such that the microwave is generated as oscillation of the thermal electrons is kept excited as the thermal electrons are synchronized to the resonance spaces of the anode
11
.
The microwave generated thus is transmitted through the antenna feeder
32
extended from the vane
15
to an outside, and emitted to outside through the A ceramic
31
and the antenna cap
33
. The microwave emitted to outside of the magnetron cooks or warms up food when the magnetron is applied to a microwave oven, and emits light by exciting plasma when the magnetron is applied to lighting fixtures or the like.
In the meantime, a microwave energy which fails in emission to outside of the anode
11
after being generated in the oscillating part is dissipated as heat, which is dissipated by the cooling fin
34
and the cooling fan to outside of the anode
11
. That is, the heat is transmitted from the anode
11
to the yoke
1
through the plurality of cooling fins
34
, and the heat transmitted to the yoke
1
is heat exchanged with external air blown by the cooling fan, to dissipate the heat and cool down the magnetron.
However, not all the heat from the anode
11
is dissipated through the cooling fin
34
and the cooling fan, but a portion thereof is transmitted to the magnets
12
a
and
12
b
adjacent thereto. Because the magnets
12
a
and
12
b
on a direct heat transmission path from the anode
11
have no other heat dissipation path, the magnets
12
a
and
12
b
are involved in heating to a temperature similar to the anode
11
. The long time exposure of the magnets
12
a
and
12
b
to a high temperature affects an intensity of the magnetic field and the magnetic circuit, which cause power drift of the magnetron.
When the magnetron is cooled down with the cooling fan, the cooling fan generates noise and vibration when in operation, and the cooling fan requires a fitting space, that makes the magnetron larger.
The outside case requires the inlet and the outlet for introduction and discharge of the exte

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