Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/403—Cells and electrode assemblies
  • G01N27/406—Cells and probes with solid electrolytes
  • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/403—Cells and electrode assemblies
  • G01N27/406—Cells and probes with solid electrolytes
  • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
  • G01N27/4077—Means for protecting the electrolyte or the electrodes

Definitions

• the invention is based on a gas sensor, in particular for determining the oxygen content in exhaust gases
• a gas sensor with a sensor element is known from US Pat. No. 4,597,850, in which the sensor element at the exhaust-side end is surrounded by a double-walled protective tube with an outer cylinder part and an inner cylinder part.
• the two cylinder parts are manufactured separately from one another, assembled in at least one assembly step and then attached to the housing of the gas sensor.
• the gas sensor according to the invention with the characterizing features of claim 1 has the advantage that the assembly for joining the double-walled protective tube not applicable. As a result, the protective tube and thus the gas sensor can be produced more cost-effectively.
• the arrangement of the inner gas openings on the ring flange between the outer and inner protective sleeve has the effect that condensed water carried in the exhaust gas does not reach the sensitive area of the sensor element directly, but is directed in the direction of the interior of the housing.
• FIG. 1 shows a section on the exhaust gas side of the gas sensor according to the invention in longitudinal section
• FIG. 2 shows a section along line II-II according to FIG. 1
• FIG. 3 shows a section along line III-III according to FIG. 1
• FIG. 4 shows a further embodiment of a protective tube in longitudinal section .
• FIG. 1 shows a section of a gas sensor on the exhaust gas side, for example an electrochemical oxygen sensor, with a metallic housing section 11 on the exhaust gas side, in which a planar sensor element 12 is fixed gas-tight.
• the exhaust-side housing section 11 is part of a housing composed, for example, of two parts.
• a connection-side housing section, not shown, in which the contacting of the sensor element 12 is accommodated, is welded gas-tight to the exhaust-side housing section 11.
• the housing section 11 consists of a cylinder sleeve 14 with an opening 15 on the exhaust gas side.
• the cylinder sleeve 14 is designed at one point with a radially inwardly directed indentation 16.
• a first ceramic molded part 21 with a first passage 22, a second ceramic molded part 23 with a second passage 24 and a sealing element 25 arranged between them are held by the indentation 16.
• a contact pressure acts on the sealing element 25, which consists of pre-pressed steatite powder.
• the steatite powder of the sealing element 25 is pressed against the sensor element 12 and against the inner wall of the housing section 11 by the contact pressure, as a result of which the sensor element 12 is held gas-tight in the housing section 11.
• the sensor element 12 consists of an oxygen ion-conducting solid electrolyte ceramic with electrodes, not shown. At least one electrode is exposed to the exhaust gas and forms a sensitive area 13 on the sensor element 12.
• the planar sensor element 12 is laminated together from a plurality of ceramic foils, sintered and, in the sintered state, has a rectangular cross section.
• a double-walled protective tube 30 with an outer protective sleeve 31 and an inner one
• the inner protective sleeve 32 attached.
• the inner protective sleeve 32 surrounds a measuring gas space 34 into which the sensor element 12 with the sensitive section 13 is immersed.
• the outer protective sleeve 31 and the inner protective sleeve 32 are spaced apart from one another, so that there is a circumferential between them
• Intermediate space 35 is formed, which serves to forward the exhaust gas into the measuring gas space 34.
• the outer protective sleeve 31 is designed as a cylindrical sleeve 36 which tapers to a cylindrical section 37 at the end on the housing side, the outer diameter of the cylindrical section 37 corresponding to the inner diameter of the opening 15 of the housing section 11.
• the sleeve 36 is slightly bent outwards for manufacturing reasons. However, it is equally conceivable to allow the sleeve 36 to run out cylindrically at the exhaust-side end or to provide it with a bend directed towards the inner protective sleeve 32.
• the sleeve 36 is designed with a closed outer surface. The gas inlet and / or gas outlet with respect to the
• Intermediate space 35 is formed by an end gas opening 39.
• the inner protective sleeve 32 has a rectangular cross section corresponding to the cross section of the sensor element 12 and has four side walls 41.
• the four side walls 41 have a sufficient distance from the sensor element 12, the distance being approximately the same on all four sides. At the exhaust end, the four side walls 41 converge to form a floor 42.
• the side walls 41 and the bottom 42 surround the measuring gas space 34 (FIGS. 2 and 3).
• a gas opening 44 for gas outlet and / or gas inlet is arranged in the bottom 42 in alignment with the center line.
• the exhaust-side end of the inner protective sleeve 32 protrudes beyond the exhaust-side end of the outer protective sleeve 31. This creates a circumferential gap 50 between the inner wall of the sleeve 36 of the outer protective sleeve 31 and the outside of the side walls 41 of the inner protective sleeve 32, which gap forms the front gas opening 39 for gas entry and / or gas exit for the intermediate space 35.
• the four side walls 41 are connected to the cylindrical sleeve 36 of the outer protective sleeve 31 by means of an annular flange 46, the annular flange 46 running at least approximately at right angles to the side walls 41 and the sleeve 36.
• Two inner gas openings 48 are introduced into the ring flange 46.
• the two inner gas openings 48 are arranged, for example, opposite one another and parallel to the wide side walls 41 of the inner protective sleeve 32.
• the double-band protective tube 30 with the outer protective sleeve 31 and the inner protective sleeve 32 is made in one piece. In terms of production technology, this is realized by a deep-drawing process, the inner protective sleeve 31 with the side walls 41 and the bottom 42 being formed first. Then the sleeve 36 of the outer protective sleeve 31 is carried out, the ring flange 46 and the gap 50 being formed at the same time. The cylindrical section 37 of the sleeve 36 is realized when the outer protective sleeve 31 is formed.
• the production of the gas openings 44 and 48 is expediently integrated into the deep-drawing process.
• the protective tube 30, which is formed in one piece and provided with the gas openings 39, 44, 48, is inserted with the cylindrical section 37 into the opening 15 of the housing section 11 and is welded by means of a circumferential weld seam 52, for example by means of laser welding.
• the exhaust gas flows in the direction indicated by an arrow in FIG. 1, the exhaust gas reaching the gap 35 through the gap 50.
• the exhaust gas penetrates into the measurement gas space 34 through the inner gas openings 48.
• the exhaust gas flows out of the measurement gas space 34 through the gas opening 44.
• the exhaust gas also flows through the gas opening 44 into the measuring gas space 34, the flow in the measuring gas space 34 and in the intermediate space 35 then being reversed.
• FIG. 4 Another embodiment of the protective tube 30 is shown in FIG. 4.
• the outer protective sleeve 31 is provided at the circumferential gap 50 with an edge 55 facing the inner protective sleeve 32.
• the edge 55 With the edge 55, the circumferential annular gap 50 is reduced and thus the gas opening 39 on the end face is narrowed.
• the narrowing of the front gas opening 39 offers even better protection against the ingress of condensed water carried in the exhaust gas.
• the inner protective sleeve 32 with any cross section, for example with a circular cross section or a square one Cross-section.
• the exhaust-side end of the sleeve 36 with an end face in which the end gas openings 39 are made.

Landscapes

• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Physics & Mathematics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Molecular Biology (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Measuring Oxygen Concentration In Cells (AREA)

Applications Claiming Priority (5)

Publications (1)

Family

ID=26027577

Family Applications (1)

Country Status (6)

Cited By (1)

Families Citing this family (20)

Family Cites Families (5)

• 1997
  • 1997-02-13 DE DE19705402A patent/DE19705402B4/de not_active Expired - Fee Related
  • 1997-06-19 KR KR1019980701875A patent/KR20000064242A/ko not_active Application Discontinuation
  • 1997-06-19 JP JP50644198A patent/JP3983295B2/ja not_active Expired - Fee Related
  • 1997-06-19 WO PCT/DE1997/001366 patent/WO1998003861A1/de not_active Application Discontinuation
  • 1997-06-19 CN CN97190832A patent/CN1197512A/zh active Pending
  • 1997-06-19 EP EP97931686A patent/EP1038173A1/de not_active Withdrawn

Non-Patent Citations (1)

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