Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Distributed parameter resonator-type magnetron
Reexamination Certificate
2001-10-17
2003-11-25
Nguyen, Hoang (Department: 2821)
Electric lamp and discharge devices: systems
Combined load device or load device temperature modifying...
Distributed parameter resonator-type magnetron
C315S039750
Reexamination Certificate
active
06653788
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetron which is an electron tube used for generating microwaves, and processing equipment employing the magnetron.
A magnetron can generate microwave power efficiently, and therefore is widely used in radar applications, medical applications, cooking appliances such as a microwave oven, semiconductor device manufacturing equipment, and other microwave applications.
FIG. 16
is a cross-sectional view of an essential part of an example of a conventional magnetron. In
FIG. 16
, reference numeral
1
denotes a filament serving as a thermionic electron source,
2
are plural anode vanes,
3
is an anode cylinder,
4
and
4
a
are annular permanent magnets,
5
and
5
a
are shallow-dish-shaped pole pieces,
6
and
6
a
are yokes,
7
is an antenna lead,
8
is an antenna,
9
is an exhaust tube,
10
is an antenna cover,
11
is an insulator,
12
is an exhaust-tube support,
13
is an interaction space,
14
and
15
are inner and outer straps, respectively,
16
and
17
are upper and lower cap-shaped sealing metals, respectively,
18
is a metal gasket, and
19
is an output section. The output section
19
includes the antenna lead
7
, the antenna
8
, the exhaust tube
9
and the antenna cover
10
. Reference numeral
20
denotes a magnetic circuit section which includes the permanent magnets
4
,
4
a
serving as sources of magnetic fields, the shallow-dish-shaped pole pieces
5
,
5
a
, and the yokes
6
,
6
a.
Reference numeral
21
denotes an upper end shield,
22
is a lower end shield,
23
and
24
are cathode leads (
23
is a center lead and
24
is a side lead),
25
is an input-side ceramic,
26
arecathode terminals,
27
are lead-in wires, and
28
is a cathode section. The cathode section
28
includes the cathode filament serving as a thermionic electron source, the upper and lower end shields
21
,
22
, and the cathode leads
23
,
24
.
Reference numeral
29
denotes an anode section, which includes the plural anode vanes
2
, the anode cylinder
3
, and the inner and outer straps
14
,
15
. Reference numeral
31
denote choke coils,
32
is a feed-through capacitor,
33
is a filter case,
34
is a lid, and
45
are cooling fins.
In
FIG. 16
, the plural anode vanes
2
are fixed to the anode cylinder
3
as by brazing, or are fabricated integrally with the anode cylinder
3
by press working, such that the plural anode vanes
2
surround the helical cathode filament
1
.
The pole pieces
5
,
5
a
made of ferromagnetic material such as soft iron and the annular permanent magnets
4
,
4
a
are disposed above and below the anode cylinder
3
.
Magnetic fluxes from the permanent magnets
4
,
4
a
enter the interaction space
13
defined between the cathode filament
1
and the anode vanes
2
through the pole pieces
5
,
5
a
, and thereby provide a required axial DC magnetic field.
The yokes
6
,
6
a
form part of amagnetic circuit for passing the magnetic fluxes from the permanent magnets
4
,
4
a
. The magnetic circuit comprises the yokes
6
,
6
a
, the permanent magnets
4
,
4
a
, and the pole pieces
5
,
5
a.
Electrons emitted from the cathode filament
1
at a negative high potential rotate about the cathode filament axis acted upon simultaneously an electric field and a magnetic field, and thereby generate a microwave electric field at each of the anode vanes
2
. The generated microwave electric fields reach the antenna
8
via the antenna lead
7
, and are output to an external device from the antenna cover
10
.
The cathode filament
1
is generally made of a tungsten wire containing about 1% of thorium oxide (ThO
2
) in view of electron emission characteristics and workability, and is supported by the upper end shield
21
, the lower end shield
22
, and the cathode leads
23
,
24
.
The cathode leads
23
,
24
are generally made of molybdenum (Mo) in view of heat resistance and workability, and are connected to the lead-in wires
27
,
27
via terminal plates
26
brazed on the top of the input side ceramic
25
as by silver solder. The lead-in wires
27
,
27
are connected to the choke coils
31
,
31
.
Attached to the underside of the magnetron is a filter structure comprising the filter case
33
housing the choke coils
31
and the feed-through capacitor
32
and the lid
34
for closing the opening of the filter case
33
.
The choke coils
31
connected to the lead-in wires
27
form an L-C filter with the feed-through capacitor
32
and suppress low frequency components propagating through the cathode leads
23
,
24
. Microwave components are shielded by the filter case
33
and the lid
34
.
The cooling fins
35
fitted around the anode cylinder
3
radiate heat generated by operation of the magnetron.
FIG. 17
is a schematic cross-sectional view of an essential part of a microwave oven serving as an example of conventional processing equipment of the coaxial waveguide type using a magnetron as a microwave generator. In
FIG. 17
, reference numeral
41
denotes a cooking chamber of the microwave oven, and material
43
to be heated is placed in the cooking chamber via a door
42
. Reference numeral
44
denotes the magnetron, and
45
is a heating antenna, which is connected to the magnetron
44
via the coaxial waveguide
46
. Microwaves generated by the magnetron
44
are supplied to the cooking chamber
41
in which the material
43
to be heated is placed, via the coaxial waveguide
46
, and heat the material
43
by irradiating the material
43
.
The coaxial waveguide
46
comprises a cylindrical outer conductor
47
and an inner conductor
48
placed concentrically with the outer conductor
47
.
Further, for a magnetron of the type having the antenna
8
of the structure in which the antenna lead
7
is sandwiched hermetically between the exhaust tube
9
as shown in
FIG. 16
, a structure is proposed in Japanese Patent Application Laid-open No. Hei 7-282737, for example, in which the inner conductor
48
of the coaxial waveguide
46
is connected to the antenna cover
10
, and the outer conductor
47
is fixed to the yoke
6
a.
Further, as another example of the conventional structure for coupling the magnetron to the waveguide, a structure employing a waveguide having no inner conductor is also proposed for processing equipment such as semiconductor device manufacturing equipment, as well as the heat processing equipment such as the microwave oven. In the processing equipment employing the waveguide having no inner conductor, microwaves are supplied to a processing chamber by projecting the antenna into the waveguide, unlike in the above-described case employing the coaxial waveguide.
The other references disclosing the structures of such magnetrons and processing equipment are Japanese Utility Model Application Laid-open Nos. Sho 53-9541, Sho 53-9542, Japanese Patent Application Laid-open Nos. Hei 2-79331, Hei 9-74083, Hei 9-82688, and Hei 9-82691, for example.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a small-sized, lightweight, high-power output magnetron, processing equipment employing this magnetron, and a coupling structure between the magnetron and a coaxial waveguide.
To achieve the above objects, in accordance with an embodiment of the present invention, there is provided a magnetron comprising: an anode cylinder; a plurality of vanes extending radially inwardly from the anode cylinder; a cathode filament extending along a center axis of the anode cylinder; an output section including an antenna coupled to one of the plurality of vanes; and a magnetic circuit section for supplying a magnetic field into the anode cylinder, whereby the magnetron oscillates at a fundamental frequency in a range from 400 MHz to 600 MHz.
To achieve the above objects, in accordance with another embodiment of the present invention, there is provided a magnetron comprising: an anode cylinder; a plurality of vanes extending radially inwardly from the anode cylinder; a cathode filament extending along a center axis of the anode cylinder
Kuga Masumi
Moriike Toru
Ogura Toshio
Oguro Tomokatsu
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
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