U.S. patent application number 09/171717 was filed with the patent office on 2001-11-29 for sensor and method for the manufacture.
Invention is credited to FRIESE, KARL-HERMANN, GEIER, HEINZ, WEYL, HELMUT, WIEDENMANN, HANS-MARTIN.
Application Number | 20010045120 09/171717 |
Document ID | / |
Family ID | 7821386 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045120 |
Kind Code |
A1 |
FRIESE, KARL-HERMANN ; et
al. |
November 29, 2001 |
SENSOR AND METHOD FOR THE MANUFACTURE
Abstract
A sensor, in particular for determining the oxygen content in
exhaust gases of internal combustion engines, is proposed, as well
as a method for its manufacture. The sensor includes a receptacle,
arranged in a longitudinal bore (16) of a metal housing (10), for a
sensing element (12), in which receptacle the sensing element (12)
is received in gas-tight fashion via a sensing element seal, the
sensing element seal being a glass seal (57). The receptacle has a
measured-gas-side ceramic shaped element (20) and a connector-side
ceramic shaped element (27), which are arranged axially one behind
the other. A cavity (55) into which the glass seal (57) is pressed
while hot is configured between the two ceramic shaped element (20,
27).
Inventors: |
FRIESE, KARL-HERMANN;
(LEONBERG, DE) ; GEIER, HEINZ; (LEONBERG, DE)
; WEYL, HELMUT; (SCHWIEBERDINGEN, DE) ;
WIEDENMANN, HANS-MARTIN; (STUTTGART, DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
7821386 |
Appl. No.: |
09/171717 |
Filed: |
April 8, 1999 |
PCT Filed: |
January 7, 1998 |
PCT NO: |
PCT/DE98/00008 |
Current U.S.
Class: |
73/23.31 ;
422/98; 73/31.05 |
Current CPC
Class: |
G01N 27/4077 20130101;
G01N 27/407 20130101 |
Class at
Publication: |
73/23.31 ;
422/98; 73/31.05 |
International
Class: |
G01N 007/00; G01N
027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 1997 |
DE |
197 07 456.1 |
Claims
1. A sensor, in particular for determining the oxygen content in
exhaust gases of internal combustion engines, having a receptacle,
arranged in a longitudinal bore of a metal housing, for a sensing
element, in which receptacle the sensing element is received in
gas-tight fashion via a sensing element seal, the sensing element
seal containing a glass seal, wherein the receptacle for the
sensing element (12) has a measured-gas-side ceramic shaped element
(20) and a connector-side ceramic shaped element (27); and a cavity
(55) into which the glass seal (57) is pressed while hot is
configured between the two ceramic shaped elements (20, 27).
2. The sensor as defined in claim 1, wherein the measured-gas-side
ceramic shaped element (20) and the connector-side ceramic shaped
element (27) are arranged axially one behind another; the one
ceramic shaped element (20) has a punch-shaped extension (51) and
the other ceramic shaped element (27) has a recess (52); and the
cavity (55) is configured in the recess (52).
3. The sensor as defined in claim 2, wherein the punch-shaped
extension (51) is configured on the measured-gas-side ceramic
shaped element (20), and the recess (52) on the connector-side
ceramic shaped element (27).
4. The sensor as defined in claim 2 or 3, wherein the punch-shaped
extension (51) in the recess is surrounded by a radial gap
(53).
5. The sensor as defined in claim 1, wherein the glass seal (57)
contains a lithium aluminum silicate glass or a lithium barium
aluminum silicate glass.
6. The sensor as defined in claim 1 or 5, wherein the glass seal
(57) contains, in addition to the glass constituents, additives
such as plasticizers, fluxing agents, fillers, or a mixture of
these additives.
7. The sensor as defined in claim 6, wherein the plasticizers are
substances such as copper, aluminum, iron, brass, graphite, boron
nitride, MoS.sub.2, or a mixture of these substances.
8. The sensor as defined in claim 1, wherein the ceramic shaped
elements (20, 27) each have an axially extending passthrough (24,
30) for receiving the sensing element (12); and at least one of the
passthroughs (24, 30) of the ceramic shaped elements (20, 27) is
configured with an expansion (61) facing the cavity (55).
9. The sensor as defined in claim 1, wherein at least on the
measured-gas-side ceramic shaped element (20), the sensing element
seal has, in addition to the glass seal (57), at least one powdered
sealing packing.
10. The sensor as defined in claim 9, wherein the powdered sealing
packing is arranged in the cavity (55), adjacent to the glass seal
(57), on the side subject to greater thermal stress.
11. The sensor as defined in claim 10, wherein the powdered sealing
packing is made of a ceramic.
12. The sensor as defined in claim 9, 10, or 11, wherein the
powdered sealing packing is made of steatite, graphite, boron
nitride, Al.sub.2O.sub.3, ZrO.sub.2, or a mixture of these
substances.
13. A method for manufacturing a sensor as defined in one of claims
1 through 12, wherein a glass blank is inserted between the two
ceramic shaped elements; and the glass blank is hot-pressed to form
the glass seal at a temperature which corresponds at least to the
softening temperature of the glass or glass ceramic that is
used.
14. The method as defined in claim 12, wherein the compressive
force for pressing the glass blank (63) is 400 to 700
kilogram-force.
15. The method as defined in claim 12 or 13, wherein the
measured-gas-side ceramic shaped element, the sensing element, the
glass blank, the connector-side ceramic shaped element, and
optionally the powdered sealing packing are inserted in the
assembled position into a die; the glass blank is heated in the die
to at least the softening temperature; and the compressive force is
then applied onto the connector-side ceramic shaped element using a
punch.
Description
BACKGROUND INFORMATION
[0001] The invention proceeds from a sensor according to the
species defined in the principal claim. A sensor of this kind is
known from U.S. Pat. No. 5,467,636, in which a planar sensing
element is immobilized in gas-tight fashion, by way of a sealing
element, in a passthrough of an exhaust-gas-side lower ceramic
shaped element. The exhaust-gas-side ceramic shaped element has on
the end surface facing away from the exhaust gas a recess which
surrounds the passthrough and into which a glass seal is
introduced. A further ceramic shaped element, which is joined via a
metal solder join to the housing, sits on the glass seal. The glass
seal encloses the sensing element inside the recess, and
constitutes a gas-tight join between ceramic shaped element and
sensing element at this point.
SUMMARY OF THE INVENTION
[0002] The sensor according to the present invention, having the
characterizing features of the principal claim, has the advantage
that a mechanically stable and gas-tight join is possible between
the planar sensing element and both ceramic shaped elements.
[0003] The hermetic seal of the sensing element thereby achieved is
vibration-proof, so that while the sensor is being used in the
motor vehicle, the sensing element can be immobilized over the
utilization period in mechanically stable and hermetic fashion. The
method according to the present invention makes it possible for
gas-tight immobilization of the sensing element to be attained
efficiently.
[0004] The features set forth in the dependent claims make possible
developments of and improvements to the sensor according to the
invention and the method for its manufacture. A particularly
mechanically stable and gas-tight join between the sensing element
and the ceramic shaped elements is achieved if the glass seal
covers the sensing element over as large an area as possible, but
does not penetrate appreciably into the front region which is
subject to high thermal stress when the sensor is later operated.
The arrangement of a powdered additional seal on the measured-gas
site in front of the glass seal prevents the molten glass from
penetrating, during the melting process, into the front region of
the sensing element that is subject to high thermal stress. It is
advantageous for the manufacturing process that the two ceramic
shaped elements are configured, on the end faces which face toward
one another, in the form of a die and punch, and act accordingly on
one another. This makes possible compression of the glass seal, and
of the powdered additional seal that is optionally used, utilizing
the geometry of the ceramic shaped elements. The presence of a gap
between die and punch has the advantage that the glass seal can
escape into the gap upon compression. This makes it possible to
work with a high compressive force. At the same time, it prevents
the two end faces of the ceramic shaped elements from striking one
another. In addition, a further glass seal can be inserted into the
annular gap between the ceramic shaped elements, or an annular
metal foil or plate can be set in place, thus resulting in a
positive join between the two ceramic elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Three exemplary embodiments of the invention are depicted in
the drawings and explained in more detail in the description below.
In the drawings:
[0006] FIG. 1 shows a sectioned depiction through a sensor
according to the invention;
[0007] FIG. 2 shows a first exemplary embodiment of a sensing
element seal for the sensing element in the uninstalled state, with
an apparatus for manufacturing the seal;
[0008] FIG. 3 shows a second exemplary embodiment of a sensing
element seal in the uninstalled state; and
[0009] FIG. 4 shows a third exemplary embodiment of a sensing
element seal in the uninstalled state.
DETAILED DESCRIPTION
[0010] The sensor depicted in FIG. 1 is an electrochemical sensor
for determining the oxygen content in exhaust gases of internal
combustion engines. The sensor has a metal housing 10 in which a
flat-plate sensing element 12, having a measured-gas-side end
section 13 and a connector-side end section 14, is arranged.
Housing 10 is configured with threads as attachment means for
installation into an exhaust pipe (not depicted). Also arranged in
housing 10 is a longitudinal bore 16 having, for example, a first
shoulder-like annular surface 17 and a second shoulder-like annular
surface 18.
[0011] Arranged in longitudinal bore 16 is a measured-gas-side
ceramic shaped element 20 having a measured-gas-side passthrough
24, and having a measured-gas-side end face 21 and a connector-side
end face 22. Measured-gas-side end face 21 is configured with a
conically extending sealing seat 23 which sits on a metal sealing
ring 25 that rests against second shoulder-like annular surface 18.
Arranged above measured-gas-side ceramic shaped element 20 is a
connector-side ceramic shaped element 27 having a connector-side
passthrough 30 and having a measured-gas-side end face 28 and a
connector-side end face 29.
[0012] A disk spring 31 that is under mechanical preload, which
presses via a tubular retaining cap 32 onto measured-gas-side
ceramic shaped element 27 that projects out of housing 10, rests on
connector-side end face 29 of connector-side ceramic shaped element
27; retaining cap 32 engages via snap-lock tabs 34 into an annular
groove 33 arranged on the outer side of housing 10. The two ceramic
shaped elements 20, 27 are preloaded in the axial direction via
retaining cap 32 and disk spring 31, so that measured-gas-side
ceramic shaped element 20 presses with conical sealing seat 23 onto
sealing ring 25. A gas-tight sealing seat thus forms between
housing 10 and ceramic shaped element 20.
[0013] Measured-gas-side end section 13 projecting out of the
housing is, for example, surrounded at a distance by a
double-walled protective tube 37 having gas inlet and gas outlet
openings 38. On connector-side end section 14, sensing element 12
has contacts (not depicted further) which make contact with
connector cables 42 via a contact plug 41. Connector plug 41
includes, for example, two ceramic elements which are held together
by a clamping piece 43. Connector-side end section 14 of sensing
element 12, which projects out of connector-side ceramic shaped
element 27, is surrounded by a metal sleeve 45 which is welded in
gas-tight fashion to housing 10 and has a tubular opening 47 in
which a cable passthrough 48 is located for the passage of
connector cable 42.
[0014] Measured-gas-side ceramic shaped element 20 has on
connector-side end face 22 a punch-shaped extension 51 which
surrounds measured-gas-side passthrough 24. Connector-side ceramic
shaped element 27 has on measured-gas-side end face 28 a recess 52
into which punch-shaped extension 51 penetrates with a radial gap
53. A cavity 55, which is filled with a glass seal 57, is formed
between the end face of punch-shaped extension 51 and the bottom of
recess 53. It is also possible to configure punch-shaped extension
51 on connector-side ceramic shaped element 27, and recess 52 on
measured-gas-side ceramic shaped element 20.
[0015] Glass seal 57 causes sensing element 16 to be hermetically
sealed in ceramic shaped elements 20, 27. The dimensions of
punch-shaped extension 51 and of recess 52 are such that an annular
gap 59 is formed between the mutually facing annular surfaces of
measured-gas-side ceramic shaped element 20 and connector-side
ceramic shaped element 27. The purpose of annular gap 59 is to
allow the fusible glass of glass seal 57 to escape via radial gap
53 into annular gap 59 upon compression.
[0016] A fusible glass, for example a lithium aluminum silicate
glass or a lithium barium aluminum silicate glass, is suitable as
glass seal 57. Additives which improve the flow characteristics of
the molten glass can be added to the fusible glass.
[0017] Powdered substances such as copper, aluminum, iron, brass,
graphite, boron nitride, MoS.sub.2, or a mixture of these
substances, can be used as additives for plastification of glass
seal 57 during the joining process. Lithium carbonate, lithium
soap, borax, or boric acid are used, for example, as fluxes for
glass seal 57. The addition of compensating fillers, such as
aluminum nitride, silicon nitride, zirconium tungstate, or a
mixture of these substances, is suitable for adjusting the thermal
expansion. A further improvement in the join between glass seal 57
and the ceramic of ceramic shaped elements 20, 27 is achieved if a
ceramic binder, such as aluminum phosphate or chromium phosphate,
is added to glass seal 57.
[0018] In order to achieve large-area wetting of sensing element 12
with glass seal 57, in the present exemplary embodiments the side
surfaces of measured-gas-side passthrough 24 and of connector-side
passthrough 30 of ceramic shaped elements 20, 27 are each
configured, toward cavity 55, with a conically extending
enlargement 61 (FIGS. 2, 3, and 4).
[0019] Three exemplary embodiments of the sensing element seal in
the uninstalled state, in each case with an apparatus for
manufacturing glass seal 57, are evident from FIGS. 2, 3, and
4.
[0020] The apparatus has a support 70 acting as die, with a
receptacle 71 and a stop 72. Ceramic shaped elements 20 and 27 are
positioned in receptacle 71 with sensing element 12 received in
passthroughs 24, 30. The axial position of sensing element 12 is
defined in this context by stop 72, sensing element 12 resting with
measured-gas-side end section 13 on stop 72. Measured-gas-side
ceramic shaped element 20 is first inserted with sensing element 12
into receptacle 71. A glass blank 63, for example in the form of a
glass pellet or glass film, is placed onto the end surface of
punch-shaped extension 51, glass blank 63 having an opening with
which glass blank 63 is slid over sensing element 12.
Connector-side ceramic shaped element 27 is then placed onto glass
blank 63, so that connector-side end section 14 of sensing element
12 projects through passthrough 30. In the arrangement described, a
compressive force of, for example, 600 kg-force is applied onto
connector-side ceramic shaped element 27 using a pressing punch 74.
Beforehand, however, glass blank 63 was heated, for example by a
heating device housed in support 70, to a temperature above the
softening temperature of the fusible glass or glass ceramic being
used. Upon compression, the fluid glass blank 63 deforms and is
thereby pressed into conical enlargements 61 and into radial gap
53. Fusible glass flowing out via radial gap 53 can escape into
end-surface annular gap 53.
[0021] A second exemplary embodiment is depicted in FIG. 3. This
exemplary embodiment differs from the exemplary embodiment of FIG.
1 in that a further annular glass blank 64 is inserted into annular
gap 59. Upon compression, the fluid further glass blank 64, like
glass blank 63, deforms so that annular gap 59 is additionally
sealed with a further glass seal.
[0022] A further exemplary embodiment of a sensing element seal is
evident from the arrangement in FIG. 4. Here a further blank 65,
precompressed and optionally presintered, is arranged on the
measured-gas side below glass blank 63. Materials with good plastic
deformability, such as talc, kaolin, clay, bentonite, graphite,
boron nitride, etc. are in principle particularly suitable as the
material for further blank 65. As punch 74 is applied during
compression of the fluid glass blank 63, blank 65 is simultaneously
deformed into its powder constituents, thus resulting in a powdered
additional seal. Before the fusible glass flows in, the powder
penetrates into the gap of measured-gas-side passthrough 24 formed
by conical enlargement 61, so that the fusible glass is prevented
from flowing to the measured-gas end of ceramic shaped element 20
that is subject to high thermal stress.
[0023] The apparatuses depicted in FIGS. 3 and 4 correspond to the
apparatus of FIG. 2. The method for manufacturing glass seal 57
according to FIG. 4 can be carried out in accordance with the
method implemented using the apparatus in FIG. 2. It is also
possible, however, first to deform further blank 65 into powder
using a punch and press it into the gap between sensing element and
measured-gas-side passthrough, and then to compress glass blank 63
using the procedure according to FIG. 2. A further embodiment of
the sensing element seal according to FIG. 4, having a further
fused glass seal in annular gap 59 as in the case of the exemplary
embodiment in FIG. 3, is also possible.
* * * * *