JPS6112615B2 - - Google Patents
Info
- Publication number
- JPS6112615B2 JPS6112615B2 JP14044978A JP14044978A JPS6112615B2 JP S6112615 B2 JPS6112615 B2 JP S6112615B2 JP 14044978 A JP14044978 A JP 14044978A JP 14044978 A JP14044978 A JP 14044978A JP S6112615 B2 JPS6112615 B2 JP S6112615B2
- Authority
- JP
- Japan
- Prior art keywords
- cathode
- tungsten
- surface layer
- cathode structure
- electron emission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000010438 heat treatment Methods 0.000 claims description 15
- 239000002344 surface layer Substances 0.000 claims description 15
- 239000010410 layer Substances 0.000 claims description 9
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 7
- 229910052721 tungsten Inorganic materials 0.000 claims description 7
- 239000010937 tungsten Substances 0.000 claims description 7
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 claims description 5
- ZCUFMDLYAMJYST-UHFFFAOYSA-N thorium dioxide Chemical compound O=[Th]=O ZCUFMDLYAMJYST-UHFFFAOYSA-N 0.000 claims description 3
- 229910003452 thorium oxide Inorganic materials 0.000 claims description 3
- 230000002093 peripheral effect Effects 0.000 claims 1
- 230000004397 blinking Effects 0.000 description 5
- 230000010355 oscillation Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 230000008646 thermal stress Effects 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910052776 Thorium Inorganic materials 0.000 description 1
- 229910001080 W alloy Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000010411 cooking Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 235000013611 frozen food Nutrition 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000010257 thawing Methods 0.000 description 1
- WLTSUBTXQJEURO-UHFFFAOYSA-N thorium tungsten Chemical compound [W].[Th] WLTSUBTXQJEURO-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Microwave Tubes (AREA)
- Solid Thermionic Cathode (AREA)
Description
本発明は、電子管用陰極構体に係り、特に電子
レンジに用いるマグネトロンに好適な陰極構体に
関する。
電子管のなかでもマグネトロンは、マイクロ波
を効率よく発生することから電子レンジに組込ま
れ冷凍食品の解凍や加熱調理に用いられる。
従来マグネトロンのマイクロ波発生源である陰
極構体には、トリウムを含むタングステンでなる
加熱線条を螺旋状に形成し両端を支持部材で支持
したものが用いられている。
この陰極構体には、電子放射密度が高いこと瞬
時動作が可能なこと等のマグネトロン用の陰極と
して好ましい特性が要求される。このために通常
線条螺旋体の表面を炭化させて電子放射特性を安
定にすることが行なわれている。
しかしながら、大容量の電流を短時間の間隔で
点滅させて発振出力を調整する使用方法の場合、
従来の陰極構体では安定した電子放出を長期間維
持することが困難であつた。
したがつて本発明の目的は、いかなる使用に対
しても安定した電子放出が得られる陰極構体を提
供することである。
本発明の他の目的は、所定の電子放出状態を長
期間維持しうる陰極構体を提供することである。
本発明の他の目的は、急激な温度変化に対して
安定した特性を有する陰極構体を提供することで
ある。
本発明の他の目的は、高温にて機械的強度の大
きい陰極構体を提供することである。
本発明の他の目的は、発振出力を所望どおり調
整しうるマグネトロン用陰極構体を提供すること
である。
発明者等は、マグネトロンに用いる陰極構体に
ついて研究した結果、次のことを見出した。すな
わち、陰極構体の電子放出状態は、陰極構体を構
成する加熱線条の材質と表面状態、なかでも表面
に形成される表面層の状態に左右される。
発振出力を調整するために、電流を断続的に
「入」「切」すると、電流を「入」にした時の過電
流（ラツシユカレント）により加熱線条は急激に
温度が上昇する。この際、加熱線条の内部と表面
層の熱膨張の差等の性質の相違により応力が生
じ、表面層の特性を劣化させるものと考えられ
る。
本発明は、このような応力によつても特性が安
定した加熱線条を具備してなる陰極構体を提供す
る。
本発明に係る陰極構体は、加熱線条を酸化トリ
ウムを含むタングステン合金で構成し表面層を炭
化タングステンとタングステンが交互に配列した
多層状としたことを主たる特徴とする。
第１図および第２図に本発明陰極構体の一実施
例を示す。第１図において螺旋状の加熱線条１
は、両端末をエンドハツト材２により支持されて
いる。第２図は、加熱線条の断面の一部を示す写
真である。第２図Ａは、150倍に拡大したもの、
第２図Ｂは、800倍に拡大したものである。第２
図Ａ及びＢで表面層とは輪状の白い部分の内周に
沿つた部分であり、中心方向へ筋状に複数の線が
入つた部分である。この筋状の線と線との間に、
これらの線とはほぼ直角に層状組織が存在してい
る。この層状組織の白地部が炭化タングステン
（W2C）であり、黒地部がタングステン（Ｗ）で
ある。
表面層はW2C層とＷ層が交互に配列した多層
組織をなしている。この様な炭化タングステンと
タングステンとが均一に交互に配列した陰極構造
体を得る為には、タングステン−トリウム陰極体
を炭化水素ガス中で加熱し炭化させた後、非酸化
雰囲気中で加熱処理を施すことによつて得られ
る。
この表面層は、電子放出に寄与するW2C層が
Ｗ層より厚く構成されることが必要である。
以上のように構成された陰極構体により次の効
果が得られる。すなわち、電子放出に最も影響す
る加熱線条の表面層が特に熱応力に対して安定し
た組織であるので、所定の電子放出状態を長期間
維持できるとともに、安定した電子放出状態を得
ることができる。
本発明に係る陰極構体と同形状の従来の陰極構
体とをそれぞれマグネトロンに組み込み比較し
た。まず、５秒間隔で点滅をくり返した場合の加
熱線条の表面積の増加率を調べた。この結果を表
１に示す。これは、加熱線条の表面形状がくずれ
表面積が増加することにより陰極フイラメントの
温度が低下し電子放出状態が著しく劣化すると考
えられるからである。なお、表面積の増加率は、
線条を断面した時の外周の長さの増加で示す。
The present invention relates to a cathode assembly for an electron tube, and particularly to a cathode assembly suitable for a magnetron used in a microwave oven. Among electron tubes, magnetrons generate microwaves efficiently, so they are incorporated into microwave ovens and used for thawing and cooking frozen foods. Conventionally, the cathode structure of a magnetron, which is a microwave generation source, uses a heating wire made of tungsten containing thorium formed in a spiral shape and supported at both ends by support members. This cathode structure is required to have favorable characteristics as a cathode for a magnetron, such as high electron emission density and instantaneous operation. For this purpose, the surface of the filamentous spiral is usually carbonized to stabilize the electron emission characteristics. However, in the case of usage in which the oscillation output is adjusted by flashing a large amount of current at short intervals,
With conventional cathode structures, it has been difficult to maintain stable electron emission for a long period of time. Therefore, it is an object of the present invention to provide a cathode structure that provides stable electron emission for any use. Another object of the present invention is to provide a cathode structure that can maintain a predetermined electron emission state for a long period of time. Another object of the present invention is to provide a cathode structure having stable characteristics against rapid temperature changes. Another object of the present invention is to provide a cathode structure that has high mechanical strength at high temperatures. Another object of the present invention is to provide a cathode structure for a magnetron that allows the oscillation output to be adjusted as desired. As a result of research on cathode structures used in magnetrons, the inventors discovered the following. That is, the electron emission state of the cathode assembly depends on the material and surface condition of the heating wires constituting the cathode assembly, and especially on the condition of the surface layer formed on the surface. When the current is intermittently turned on and off in order to adjust the oscillation output, the temperature of the heating filament rapidly rises due to the rush current when the current is turned on. At this time, it is thought that stress is generated due to the difference in properties such as a difference in thermal expansion between the inside of the heating filament and the surface layer, which deteriorates the characteristics of the surface layer. The present invention provides a cathode assembly including a heating wire whose characteristics are stable even under such stress. The main feature of the cathode structure according to the present invention is that the heating wire is made of a tungsten alloy containing thorium oxide, and the surface layer has a multilayered structure in which tungsten carbide and tungsten are alternately arranged. FIGS. 1 and 2 show an embodiment of the cathode structure of the present invention. In Fig. 1, a spiral heating line 1
is supported by end hat material 2 at both ends. FIG. 2 is a photograph showing a part of the cross section of the heating filament. Figure 2 A is a 150x magnification.
Figure 2B is magnified 800 times. Second
In Figures A and B, the surface layer is a part along the inner periphery of a ring-shaped white part, and is a part in which a plurality of lines run toward the center. Between these striped lines,
A layered structure exists almost perpendicular to these lines. The white background portion of this layered structure is tungsten carbide (W 2 C), and the black background portion is tungsten (W). The surface layer has a multilayer structure in which W 2 C layers and W layers are alternately arranged. In order to obtain such a cathode structure in which tungsten carbide and tungsten are uniformly arranged alternately, the tungsten-thorium cathode body is heated in a hydrocarbon gas to carbonize it, and then heat-treated in a non-oxidizing atmosphere. It can be obtained by applying In this surface layer, it is necessary that the W 2 C layer, which contributes to electron emission, is thicker than the W layer. The cathode structure configured as described above provides the following effects. In other words, since the surface layer of the heated filament, which has the greatest influence on electron emission, has a structure that is particularly stable against thermal stress, a predetermined electron emission state can be maintained for a long period of time, and a stable electron emission state can be obtained. . The cathode assembly according to the present invention and a conventional cathode assembly having the same shape were each incorporated into a magnetron for comparison. First, the rate of increase in the surface area of the heated filament when blinking was repeated at 5-second intervals was investigated. The results are shown in Table 1. This is because the surface shape of the heating filament is distorted and the surface area increases, which lowers the temperature of the cathode filament and is thought to significantly deteriorate the electron emission state. Furthermore, the rate of increase in surface area is
It is indicated by the increase in the length of the outer circumference when the filament is cut in section.
【表】
表１より明らかなように、本発明の陰極構体
は、加熱線条の表面増加率が従来と比較して少な
い。これは熱応力に安定でかつ形状くずれが少な
い表面積を有していることを示すものである。こ
のことは安定した電子放射をもたらす。
つぎに点滅サイクルを５秒間隔とし、陰極構体
からの電子放射の低下の度合を比較した。この結
果を第３図に示す。第３図中Ａは、表１の試料１
に対応しＢは表１の試料３に対応する。
第３図から明らかなように、エミツシヨン低下
率50％を指標とすると本発明のものは従来のもの
の約３倍の寿命を有している。
さて、本発明電子管陰極構体の加熱線条におい
て酸化トリウムは、0.5％未満では所望の電子放
射を得ることが難かしく、逆に４％を越えると加
工性を損ねる。
加熱線条の表面層は、熱応力等を考慮すると薄
いことが望ましい。すなわち、表面層の形状くず
れは、点滅時の表面炭化形成層とＷ層との熱膨張
差、熱伝導度差および電気抵抗差によつても助長
されると考えられ、これらも少なくすることが望
ましいからである。しかしながら、表面層の厚さ
は線条の断面径に対して１％未満では、電子放出
を長時間持続させることは困難である。また、断
面径の10％を越えると表面層の形状くずれが著し
くなり好ましくない。通常表面の炭化形成層は、
10μ〜60μの厚さがよい。
以上述べたように本発明に係る陰極構体は安定
した電子放射状態を長期間維持することができる
もので、特に点滅動作によつても、電子放射の低
下の度合が少なく発振出力を容易に精度よく調整
することができる。したがつて、マグネトロン等
に用いて好ましい特性を奏する。[Table] As is clear from Table 1, the cathode structure of the present invention has a smaller surface increase rate of heating filaments than the conventional one. This indicates that the material is stable against thermal stress and has a surface area with little deformation. This results in stable electron emission. Next, the blinking cycle was set to an interval of 5 seconds, and the degree of reduction in electron emission from the cathode structure was compared. The results are shown in FIG. A in Figure 3 is sample 1 in Table 1.
and B corresponds to sample 3 in Table 1. As is clear from FIG. 3, when the emission reduction rate of 50% is used as an index, the product of the present invention has a life approximately three times longer than that of the conventional product. Now, if the amount of thorium oxide in the heating wire of the electron tube cathode assembly of the present invention is less than 0.5%, it is difficult to obtain the desired electron emission, and if it exceeds 4%, workability will be impaired. The surface layer of the heating filament is preferably thin in consideration of thermal stress and the like. In other words, the deformation of the surface layer is thought to be promoted by the difference in thermal expansion, difference in thermal conductivity, and difference in electrical resistance between the surface carbonization layer and the W layer during blinking, and these can also be reduced. Because it is desirable. However, if the thickness of the surface layer is less than 1% of the cross-sectional diameter of the filament, it is difficult to sustain electron emission for a long time. Moreover, if it exceeds 10% of the cross-sectional diameter, the shape of the surface layer will be significantly distorted, which is not preferable. The carbonized formation layer on the surface is usually
A thickness of 10μ to 60μ is best. As described above, the cathode structure according to the present invention is capable of maintaining a stable electron emission state for a long period of time, and in particular, even during blinking operation, the degree of decrease in electron emission is small and the oscillation output can be easily controlled with precision. Can be adjusted well. Therefore, it exhibits favorable characteristics when used in magnetrons and the like.
第１図は、本発明陰極構体の一実施例であり、
第２図はその加熱線条の断面の一部を拡大して示
す顕微鏡写真である。なお、倍率は第２図Ａが
150倍、第２図Ｂが800倍である。第３図は陰極構
体の点滅持続時間に対する電子放射低下率を示す
グラフである。
１……加熱線条、２……支持部材。
FIG. 1 shows an embodiment of the cathode structure of the present invention,
FIG. 2 is a micrograph showing an enlarged part of the cross section of the heated filament. In addition, the magnification is shown in Figure 2 A.
150 times, Figure 2 B is 800 times. FIG. 3 is a graph showing the electron emission reduction rate with respect to the blinking duration of the cathode assembly. 1... heating filament, 2... support member.
Claims (1)
されてなる陰極構体であつて、加熱線条は重量％
で酸化トリウム0.5〜4.0％、残部実質的にタング
ステンでなりその表面には炭化タングステンとタ
ングステンが交互に配列した多層の表面層を有す
ることを特徴とする電子管用陰極構体。 ２ 表面層は炭化タングステンの層がタングステ
ン層よりも厚く構成してなる特許請求の範囲第１
項に記載の電子管用陰極構体。 ３ 螺旋体の外周部分の表面層は線条の断面径を
Ａとしたとき0.01〜0.1Aの厚さを有する特許請求
の範囲第１項に記載の電子管用陰極構体。[Scope of Claims] 1. A cathode structure in which a spiral heating wire is supported between a pair of supporting members, wherein the heating wire has a weight percentage of
1. A cathode assembly for an electron tube, comprising 0.5 to 4.0% thorium oxide, the remainder being substantially tungsten, and having a multilayer surface layer in which tungsten carbide and tungsten are alternately arranged. 2. Claim 1 in which the surface layer has a tungsten carbide layer thicker than the tungsten layer.
The cathode structure for an electron tube as described in . 3. The cathode structure for an electron tube according to claim 1, wherein the surface layer of the outer peripheral portion of the spiral body has a thickness of 0.01 to 0.1 A, where A is the cross-sectional diameter of the filament.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14044978A JPS5568047A (en) | 1978-11-16 | 1978-11-16 | Cathode structure for electron tube |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14044978A JPS5568047A (en) | 1978-11-16 | 1978-11-16 | Cathode structure for electron tube |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5568047A JPS5568047A (en) | 1980-05-22 |
| JPS6112615B2 true JPS6112615B2 (en) | 1986-04-09 |
Family
ID=15268875
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14044978A Granted JPS5568047A (en) | 1978-11-16 | 1978-11-16 | Cathode structure for electron tube |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5568047A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5586043A (en) * | 1978-12-22 | 1980-06-28 | Toshiba Corp | Cathode frame structure for electron tube |
-
1978
- 1978-11-16 JP JP14044978A patent/JPS5568047A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5568047A (en) | 1980-05-22 |
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