Note: Descriptions are shown in the official language in which they were submitted.
~76~
~ackground of the invsntion
The pre3ent invention relate~ to o~ygen sen~or~
for measurlng the oxygen co~tent of ~o~ten metal3,
particularly molten iron, and more particularly the
invention relates to improvements in the slectrical
contact structure between the solid electrolyte galvaaic
cell and the powder reference material in ~uch oxygen
sensor~.
While research ~orks and development of devices
~or ~ea3uri~g the o~ygen content of ~olten iron have been
cRrriad out by many differ~nt comp~nie~ all over the world,
all of these devices ~re based on the proces~e3 ~hich
are basically similar in nature. Particulsrly, the solid
electrolyte galvanic cell~ (e.g., ZrO2-Ca2, ZrO2-Y20~
or ZrO2-M60) whioh are used 89 ionic conductors in such
devices are for the most part formed into a simple cylln-
drical shape, a~d the contact structure between the solid
electrolyte gal~anl~ cell and ~ powder reference material
(such a9, ml~ed powder o~ Cr and Cr20~ or ~ixed powder
o~ Mo and MoO2) i~ in the form of 8 simple surface-to-
ur~Rce contact.he typical shape snd mountlng of the ~olid electro-
lrte galvanic oells in the known o~y~en sensors areshown ln Fig. 1. In the Flgure, a cyli~drlcsl ~olld
electrolyte galvanlc cell 1 is mounbed inside a quartz
tube ~ by fusion or cementing (the portlon lndisated st
nu~eral 2)~ and the 901id electrolyte gal~a~ic cell 1
makes,~ wlthln thé qu~rtz tube 3, a surface-to-~urface
1 1 ~ .
2 - ~
7~i2~S
conta'~t wlth a powder re~erence materlal 4 contained in
the quartz tube 3 below the solid ~lectrolyt~s gslvanlc
cell 1. If the devlce in thi3 condition 18 imLerBed
into molten iron from the diraction of an arrow 7, ,an,
~lectromotive for~e correspondinR to the partlal prPs3ure
o~ o~ygen in the molten iron is produced acro3s the colid
electrolyte ~alvnic cell 1 or between the ,~,olten iron and
the powder r~oference materlal 4 and de~ivered by way o~
electrode lead ~ires 5 an,d 6, and consequently the
concentration of o~ygen dissol~ed in the~ molten iron can
be determined by measuring the thus dellvered electro-
motive ~orc~
When the oxy~en se~aor of the type shown in Fig.
1 iZ3 lmmsrsed lnto molten iron, sn ~pparent oontraction
is caused in the powder referenoe material 4 upon occurrance
o~ lt~ sintering phenomenon due to high temperature, and
the solid electrolyte g~lvanic cell 1 ,~nd th3 powder
reference materinl 4 contactlng aach other ln sur~ace-
to-sur~ace relatio,n are aeparat~d ~rom each other" thus
oau,~ing contact ~silure, c,~using ,e,lectrlcally deflective
conductior,with the re,sulting increase in electric
resistance, makl,ng it impo~sible to satisfactorily m~3,asure
the generated electromotlve force snd thereby deteriorating
the resulting em~ curv,e which will be d~scribed later
snd causlng the measurement to end ln failuro.
To overcome theee d~ficien~ies, the prior art
devioes o~ the t~pe di~clo~ed for exa~ple by the inven~
tion o~ U.,~. Pste~t No. 3,772,177 have been proposed.
In the prlor art devlce o~ this type, a~ shown ln Fi~. 2,
1~76Z~5
th~t p~rtion of an electrolyte galvanic cell 1 contacting
a referencs materlal 4 ha~ the ahape of ~ ~ru3trum; and
this frustrum 9 i9 embedded ln and surrounded by the
re~erence material 4~ Also in this ca~s, h~wever,
when the reference material 4 contracts, the re~erence
material 4 ~lidingly contract~ in the dlrection o~ the
arrow, thus in mo~t instanc~s cau~ing the electrolyte
g~lvanic cell 1 and the re~erence material 4 to ~eparate
~rom each other and thereby causing the ~easuremsnt to
end i~ ~ailure. The re~ults of the actual tests made
~ith thiQ prior art device showed that the measured em~
curves were for the most part ~nsatisfactory 89 shown in
Figs. 17, 18 and 19 of the accompanylng drawing~.
Also the re~ults of the tests m~de by modifying the shape
o~ ~he fru~trum 9, nsmely, by forming that portion of the
electrolyte galvanlc cell contactinK the reference
material i~to a conical ~hape entirely and embedding
thls conical portion in the reference material, showed
about the 8ame results a~ obtalned with the frustrum
and the rate of ~uccess in measur~me~t~ W8~ not lmpro~ed
considerably~
-,
:
Summary oY the invention
.
. .~.
. In acaordance with the pre~ent invention, ln an
I oxygen sen~or tha 3hape o~ a portion of a ~olid electro-
lyte galvanic cell embedded in a re~erence material is
I ~odifled, thu~ maintaIning the desir~d electric co~tact
i~ be~ween the selId electrolyte ~alvanic cell and the
re~er~ce materlal duri~ mea0ure~ent~ and thereby ensurine
''.
4 ~ ::
,
, : :
` .. ~
.
. . ~ . , . ;, . .. ~ . , . . ; . . .
~L~7~ 05
positive and accurate meas~rement of the oxygen content
of molten metals.
Thus, the invention is used in a device for
detecting oxygen content of a molten metal having a
solid electrolyte galvanlc cell moun~ed in a quartz tube
with one end of the galvanic cell projected from one end
of the ~uartz tube, and a powder reference material
placed inside the quart7 tube and enclosing electrode
lead m~ans and the solid electrolyte galvanic cell
whereby upon immersion into ~he molten metal the device
generates an electromotive force proportional to a partial
pressure of oxygen in the molten metal. The invention
relates to the improvement wherein the portion of thé
solid electrolyte galvanic cell contacting the powder
reference material is formed into a shape having at
least one circumferential groove to provide an increased
contac~ area between the solid electrolyte galvanic cell
and the powder reference material and to increase holding
power of the powder reference material.
The advantages, features and uses of the invention
will become =ore spparent as the descrip~ion pr~ceeds,
.
. . .
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'~ ' - .
mb/~o . ~ 5 ~
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~0~62(1 ~i;
when con~ide~ed with the acc~mp~nyina drawings.
Brle~ de~crlption of the dr~wln~9
Fig. 1 is a sectional view show~n~ the constructlon
'~
of a known ~xyge~ 9en90~ constitutl~g the ~ art for
the pre~ent invention.
~ ig. 2 i9 a s~ctionsl view 3howlng the con~tructlon
o~ another known o~ygen 82n~0r co~stituting the prior
art ior the present inrention.
Fig. ~ i9 a front view showlng an embodiment o~
the solld electrolyte galvanic cell u~ed in an oxygen
~ensor according to the invention.
Flg. 4 i~ a Yront vi~ showing another embodlment . .
o~ th~ solld electrolyte ~alvanic cell u~ed in th~ o~ygen
~c~or according to the invention.
Flg. 5 i~ a ~ront view showing ~till another embodi-
ment o~ the ~olid electrolyte galvanic cell u~ed in the
oxygen sen~or o~ t~is i~ntion.
: Fie. 6 i9 a ~ront Yiew showing still another
embodiment of the 301ia electrolyt~ galvanic cell used ln
the oxygen sen~or of thi~ inventionO
.¦ ~ Fig. 7 is a ~ront vle~ ~howin~ still another
e~bodiment o~ the solid electrolyte galvsnic c~ll u~ed
ln th00xygen genaor o~ this inventlon.
Fig. 8 is a front vlew showing ~till another :~:
e~bodl~en~ o~ th~ solid electrol~te gal~anlc ~ell used ~:-
1 ~ , ,: -,
~ ~ ln thQ o~yB2~ sensor o~ thi0 lnve~tio~
:: .
~ 6 - :~
1 ~ .~ . .
~97621D5
Fig. 9 1~ a ~ront view showing still another
e~bodli~ent of the solid electrolyte galvanlc cell u~ed
in the oxygen sensor of thls ln~ntion.
Fig. 10 is a sectional view showing the con3turc-
tion o~ the oxygen 3enqor of this invention using the
solid electrolyte galvanic cell 3hown ~n Fl~. 5.
Fig. 11 i8 a sectional view showing another con3t-
ruction of the oxygen ~e~sor o~ this invention using the
isolid electrolyte galvanic cell 3hewn in ~ig. 6.
Plg. 12 is an explsnstory diagram showing the
dimen~$on oi the variDu~ part~ o~ one solid electrolyte
.~ gal~anic cell ueea in the oxygen s~nsor of this inven-
tion.
Fig. 13 ~9 an explanatory diagram showing the
depth of the depresslons formcd in the contactlng portion
of another solid electralyta galvsnic cell u8ed ln the
oxygen sensor of this invention.
~ lg. 14 is 3n explanatory dlsgra~ shawing the
depth o~ the depres~ions formed in the contacting portion
o~ 3till 8nother solld electrolyte galvanic cell u3ed
i~ the o~ygeA ~ensor o~ this inventio~.
; . Fig. 15 is a grsph 3howin~ the am~ curvo obtained
, when the o~y6en content o~ rimmed 3,teel was successlvely
maasured wl~h the o~ygen sen30r of thl3 invention~
Fig, 16 is a graph showing the em~ curve obtaln2d
whien the o~ygen content o~ ~,emi-killed 3teel was ,succe,~slvely
e~aured wlth the o~ygen sen90r oi thii3 inve~tion.
Fig. 17 ls a eraph ahowlng the unstable em~ c~rvq
. i 7 _
., - ; .
: ~ . ~-
:~ ,
76~1~D5
produced by the unsiuccessful measurement made with the prior
art oxygen sensor.
Fig. 18 is a graph showing the emf curve with hunting
which was produced by the u~successful measurement made by
the prior art oxygen sensor.
Fig. 19 is a graph showing the emf curve with a
scaleover, which was produced by the unsuccessful measurements
made with the prior art oxygen sensor.
:.
Description of the pre~erred embodiments
The solid electrolyte galvanic cell used in an oxygen
sensor according to the invention provide~ the feature that
the portion of the solid electrolyte galvanic cell contacting
the powder reference material is irregularly shaped to prevent
the occurrance of sliding between the solid electrolyte
galvanic cell and the powder reference material, In other
words, in Fig, 3 the contacting portion comprises a
small-diameter portion 10 and a large-diameter portion 12
connected to the small-diameter portion 10 and in~luding a
conical head of the same outer diameter as a body ~ortion 8,
Fig. 4 shows the contactin~ portion of the same type shown
; in Fig, 3 except that the large-diameter portion has a
spherical head, Fig. 5 shows the contacting portion in which
the large-diameter portion 12 connected to the small-diameter
portion 10 is smaller in outer diameter than the body~ and in
Fig~ 6 the large-diameter portion 12 is greater in outer
~ diameter than the body portion. Fig, 7 shows a modification
i
-- 8 --
bm:~
. ~ . ; ; ;: '
iCI17~Z~;DS
of Fle. 3, in ~hlch the emall-diameter portion 10 i9
formed into a conical shape and connected to the large-
~ , C~s~4~t~D~
A diameter portion 12~ Fig. 8 ~hows the ~&~ i~n iAcluding
a ~eriee o~ conically draw~ ~mall-diameter portions 10
providlng a plurality of alternate projectione and depres-
sions~ and Pig. 9 ~how~ the construction ln which the : -
small-diameter portion 10 i9 dr&wn into 8 conical shspe
relative to the body 8 ~nd the large-diamster portlon 12.
Flgsr 10 and 11 sho~ e~emplsry manners of mounting the
solid electrolyte galvanic cell of thi~ invention havlng
such irregularly shaped co~tacting portion.
Fig. 10 ~hows an embodiment in which the ~olld
electrolyte galvsnic cell of Fig~ 5 i9 mouated, and Fig.
11 shows another embodlment in which the ~olid electrolyte
galvanic cell of Fig. 6 i9 mounted. More specifically,
the powder referenoe msterial 4 fittinely enclo~es the
irregularly shaped portion o~ the ~olid electrolyte
galvanic cell 8 compri~ing the large-diameter portion 12
and the ~msll-diameter portion 10. As a re~ult, when
: . the o~ygen ~ensor i3 immersed into molten iron 90 that
the powder rererence ~aterial 4 sinter3, the powder refer-
ence ~aterial 4 contract~ while enoloslng the irr~gularly
~haped portion in ~uch a ~anner that the powder re~erence
materlal 4 enters i~to the depre~sion of th~ irregularly
~h~p~d portlon and the irregularly 3hap~d p~rtio~ serves
~ as a alldlng preventive ~top. This has the ~ffect o~
I preventing the ~olid electrol~te g81vanic cell 8 a~d
~he powder re~eren~e material 4 ~rom oep~rRking ~rom each
other snd diminl~hin~ the el~ctrlcal conta~t therebet~een
g _
..
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1~76Z~S
.
and thsreby ensuring poeltive and accurBte measur~ment
of the generated electromotive force nnd achlev~ng a high
r~te o~ mea~uring success.
Wlth the ~ountin~ atructure sho~n in Fig. 11, the
portion o~ a quartz tube 3 near a fu~ed portion 2 i~
curved to be drawn. ~his i8 deaigned to ensure that the
powder re~erence material 4 can enclo~e the solid el~ctro-
lyte galvanic cell B more e~te~sively. In addition, by
virtue o~ the fact that the large-diameter portlon 12 of
the solid electrolyte g~l~snic cell 8 i~ pro~ected wlth
~c outer diameter grester than the body portlon, the
contsct ~rea between the solid electrolyte ealvanic
cell B and tha powder reference ~aterial 4 ~ 9 increased.
By virtue of the ~ountlng t~tructure which ensures sn
increased contact area, the mounting ~tructure of Fig.
11 can enaure more oatis~actory measurement re~ults than
that o~ Fi~. 10 and thu~ the e~bodiment of FLg. 11 csn be
~aid the mo~t suitable one.
The ~hape ~Y th~ lrregular contacting portion
hich i~ 80 termed ln this application, i9 not limlted
to those shown in the dra~ings, and lt 1~ of cour~e
po0sible to use sny shape to sult the intended u~e and
the de~red function~ and effectc.
~ urther~ ~he curvature Or the quarbz tub~ ln
Fi~. ll i~ such bhat the inner diameter of the qunrtz
t~be 3 i~ made greate~ th~n tha outer dia~eter of the
solld eleotrolyte gal~anlc cell B to provide a au~icien~
sp~¢e ~or containing and encloslng the po~der reference
~terlal 4 and then the qusrtz tube 3 ie eurvad by an
, ~.
: : ' ' ' ~' ' ' ' ; '., , . ' ` ~ ' . ' " , ' ' .
~63 7~Z~S
amount correspondlng to the epace. Of cour~e, the
qu~rtz tube ~ay be be~t at rl~ht anglas. In short, what
la important here 18 to pro~ide a sp~ce BO a~ to ea~ily
enclo3e the solid electrolyte ~alv~nlc cell 8 with the
powder reference material 4 and allo~ the powder refer~nce
materlal 4 to enter bet~een the eolld electrolyt~ galvanic
cell 8 and the quartz tube 3, and preferably the q~artz
tube 3 i8 curved for fusi~g the quartz tube ~ to the ~olld
electrolyte gal~anlc cell 8. The spsce between the
quartz tub~ 3 and the solid electrolyte galva~lc cell 8
i~ dependent on the particulate size o~ the powder refer-
ence mater~al. For exampie, when the particulate ~iæe
i~ ln the range o~ 1 to 50 micron~ the sp~ce of as 3m811
as about 0.006 mm i~ su~ficient for ~illing purposes with
the presently avallable fi}ling techniques and con~equently
it i9 only nece~sary to provide a space width o~ at least
over 0.06 mm. Of course, the 3pace width may be made
greater, although it 19 subJect to restrictions impo~ed
by the ~using technlque~.
Further, whil~ the depth of the spacs ~or lntro~
ducing the powder ra~ere~ce m~terial i~ dependent on the
ize of the solid electrolyte ~alvanlc cell 8t the ~ize
lts irregular contscting portion, ~tc., thu~ making
lt lmpo~ible to make a swoeping statement, where th~ ~olid
eleatrolyt~ galvanic call 8 i~ cylindrical the depth of
the spsce ~u~t be eqUlVBlent ~t leaet to the length
o~ the ~rregular contacti~g portion. Howe~er, lt i9
d~irabls that thfl depth o~ t~e sp~oe b~ made a0 long as
posslble ~o a9 to en9ure an 1~proved m~suring capscity. :~
: :.
, ` " ' '` . " '. " . ,. '., "',' ' ' ',' ` ' ' ` ". ' . ' ,', ' ' . ` '` ' "" '' '
~L~76~
Mora ~peci~icall,y, the width and depth of ~he
space are re3pectively ~elected 0.1 to 1 mm nnd about
4.5 mm for mounting the ~olid electrolyte galvanic cells
o~ the shape~ shown in Figs. 5 snd 6. While such a large
~pace i8 not needed from the standpoint of the principle,
the use o~ a practical size i~ rather propo~ed in con~ide-
ratio~ o~ the fu~ing operation, m~nufacture of clectrodes,
assemblin~ operation, etc., and the ~i~e should be as lar~e
as po~ible provided that these conditions are met.
B~ the ~ay, if the depth of the 3pace e~ceed 4.5 mm9
the contact dl~tance between the electrolyte gal~anic
cell and the powder reference material increase~, and
thereby a difference of electromotive force takes place
betuee~ the upper contacting part and the lower contacting
part of the electrolyte galva~ic cell, and thq electromotive
~orce reducea a~ an abnormal i3tatu~.
In order to minimize such dlffer~nce of electromotive
Sorce, it iB desirable to ad~ust the depth of the ~pace
to 1.5 ~.
. .
0~ the oth~r hand, the required number of . .
pro~ections and depressions ~ormed in ~e contacting
portion of the solid electrol,Yte galvsnic celL is ~uch
that while the desired effect of the invention can be
produced by providing at lesst one irre~ular section
nt one place on the circu~erencc o~ ths ~olid electrolyte
galYanic ce}l contacting the powder re~erence material,
better re~ult~ can be obt~ined by increa~in~ the number
and consequently it 1~ mcst de~irable to prov~de a plura-
:' ~
- 12 -
, ,
'~
1, .. . ~ . - ~ . . .
'~ ~ 7 6Z ~ 5
lity of projections and depres~ions over the entire
circumference oE the solid electrolyte galvanic cell. As
rega~ds the size of the irregular section, the same efEect
can be obtained by decreasing the size as the number of the
irregular sections is increased and the size of the
irregular sections must be increased with decrease in the
number.
Now, some specific examples of the irregular sections
formed over the entire circumference of the solid electrolyte
galvanic cell will be described with reference to Figs~ 12,
13 and 14. It will be seen that that the depth d of the
depressions on the solid electrolyte galvanîc cells shown
in Figs. 12 to 14 is decreased with increase in the number
of the depressions. When the number of depressions is
increased, angular depressions are p~eferred as shown in
Fig. 14. The actual measurement tests conducted by using
these solid electrolyte galvanic cells showed that quite
satisfactory electric contact characteristics could be
obtained with all of these solid electrolyte galvanic cells.
A comparision of the solid electrolyte galvanic cells shown
i~ Figs. 12, 13 and 14 has shown that the depth d of each
depression can be decreased as the number of the depressions
is increased in Figs. 12, 13 and 14 in this order, and
particularly in ~he case of Fig. 14 using a greater numb~r
of depres.sions, the desired effect can be obtained with the
depth d of as small as 0~1 mm, It has also been shown that
the desired effect can be produced with d=0,15 mm in the
case of Fig. 13.
- 13 -
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... ... . , .. : . , , , . ; . . . .. - .: ...
: . . .. - . , . ~ . . . .: .
376Z~5
Although the provision of a single small irregular
section will be sufficient for accomplishing the objects of
this invention, ideally it is desirable to provide a large
number of large depressions~ However, in consideration of
the actual manufacturing techniques o~ solid electrolyte
galvanic cell, that is, the molding of solid electrolyte
galvanic cell involving the process of preparing a split
die, introducing in~o and sinter.ing an electrolyte in the
split die and molding ~he sam~ into a solid electrolyte
galvanic cell by a molding press or injection molder, the
mounting techniques of solid electrolyte galvanic cell,
the assemblying techniques of electrodes, etc., the most
preferred shape will be the one shown in Fig. 12 employing
the depression having the depth d of about 0.25 mm,
The dimensions of the solid electrol~te galvanic
cell of Fig. 12 are as follows~
Dl = 2.0
D2 = 1.5 ~
Q1 = 8.0 mm
Q2 = 5~5 mm
~3 = 1.5 mm
Q4 = l.0 mm
The following Table 1 shows, in comparison with the
results obtained with the prior art devices, the rates of
success in the measurements made with the oxygen sensor of
this i~vention employing the solid electrolyte galvanic cells
of the above mentioned shapes. In ~able 1, each denominator
represents the number of the meas~rements made and each :: :
~umerator represents the number of the successful measurements4
.
-- 14 -- .
bm ~ O,
.: . . .
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~: . . . .. . .. .
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762~
Tsble 1 - Rate of Success~ul
Mea~urements (%)
~ . . ,, ~ .... _ . . _~_
Meusuring conditions Prior srtPre3ent lnventl n
. _ .~ ~ _. - I
: Furn~ce Type o~ ~teel Fig. l Fig. 2 Fl~. 3 Fig. 4
. _, __ ~ , __
. Test C molten ~teel ~ 6~ 17 7037_90 ~g5_98
.. _ . .~ ~ __ ~-- _.
~urnace O 0~ - O 30 % C, 49~-7~ lQ-70 237_90 ~o~-l
:~, _ . , . _ . _
Rimmed steel 301_60 1~_70 18_80 192_96
Lsdle _ _ _ _.~ . .
(250 t) ~emi-killed ste~l398_66 16=60 19-90 ~ 97
~ -- . _ __ _ ____ ~ ~ _ _ __ r
C.C, ~emi-killed ~teel 138_6~ 16_60 l~_B0 140_93
~' tundish A1l1~ ~t~l61 61 lo-70 190~90 50~94
~, . .~ .~ _ _ .
Rimmea ~teel 146 58 16_60 17_85 ~ 95
Mold ~ . . .
. . ~ = _ aæ~o-6~ 1 70 27-~5~a2 95 ~:
'''. ~
1 ..As will be ~een from Table 1, the rstea o~ succes~
.l; obtained with the devlcas of thls lnve~tion sre e~tremely . .
high B8 compsred wlth those of the prlor art devices.
In Table 1, the determi~atlon o~ the 9uccH~ul
~od unsucce~s~ul me~urements was mAde on the basis
,. ( :
1~ : that the euccess~ul ~easure~ent i9 one 1~ ~hich the ~ :
:j , recorded em~ curYe re8ult8 in a stable graph as shown -
I; I ln ~16. 15 or 16 ~nd the unsucce~ul ~es~ur~ment res-
,,1: ' ,,~ .
15 - ~ :
t ~
:h
~620S
pre~ent~ one resulting i~ such a graph as ~hown in Fig.
17, 18 or l9, and the devics of this inv~ntion showed
no such uns3ucce~3ful result.
Further, in order to i~crease the number of the
:~ succe,s~ful measurments, it i~ mo~t desirable to ~ake
~ the slze o~ eYery part in ~ig. 12 a~ ~ollows:
.~ . .
Dl _ 2.4 ~
D2 = 1.8 ~ :
~ 4= 4~5 mm ".
~2 = 3~ mm
.r ~ = l.o mm :
;
; ~4 = 0.5 mm
.~ '
While the ~olid el0ctrolyte galv~nic cell of thi~ :
invention i9 designed for use in an oxygen sensor of the
type which i3 usually used for mea~uring the concentra- :
tion of di~solved oxygen in molten iro~ as des~ribed
hnreinabo~s, the present invention is not inten~ed to be
limited to thls application, ~nd the device of this inven-
tion msy also be used as an electric contact 3tructure
for oxygen sensor,~ of th~ type u3ed for mea~uring the
o~ygen content of molten nonferrou9 metal~ (e.g-, CUr
Al, Zn, etc.) or e8 ~n electric contact otructure for
oxygen sen~or~ of the type u3ed for measuring the content
of element~ ln molten metals other than o~,yeen (e.g.,
, N, Al~ etc.) and it i~ capable of ensuring a high
rsge of 8u~cq89 in measur~ent.
~, . . .
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