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EP0001511A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Thermistor and method of fabrication

Assignee: Ford-Werke GmbH
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Filing: 1978-10-05
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Granted: —
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Expires: 1998-10-05
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Abstract

Abstract A high temperature thermistor (24) is fabricated from titanium dioxide ceramic forming material which is processed to produce a sensor body (58) having a pair of electrical leads (34, 36) in spaced apart relation embedded within the body and with the body having a porosity compatible with use as a rapid response time partial pressure of oxygen responsive sensor. The sensor body (58) is then coated with a layer (60) of oxygen impervious barrier or maskant material. This material masks the sensor (58) from any changes in the partial pressure of oxygen of its environment and permits the sensor to respond electrically exclusively to changes in the temperature of its environment. At elevated temperatures above about 700°F the encapsulated titania ceramic material behaves as a semiconductor having a resistance which is responsive to the temperature of the sensor element (58). The thermistor (24) is fabricated by processing titania powder which includes a substantial majority of rutile phase material.

Inventors

  • 👤 Elmer Thomas Heiney
  • 👤 Stanley Richard Merchant

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-10-28 23:20
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/14; G01N27/16; G01N27/12; G09; G09B; G09B9/00; G09B9/54; H; H01; H01C; H01C7/00; H01C7/04; H01C7/042; H01C7/043; H01C7/045

Claims Analysis

Total Claims: 10
Claim 1
Independent Claim 56 words
A thermistor comprising a body of ceramic material; two electrical leads embedded in mutually noncontacting relation in said body; said ceramic material having an electrical resistance which varies with temperature and with partial pressure of oxygen at elevated:temperatures characterised in that the body of ceramic material is substantially completely encapsulated in a coating of oxygen-impervious material.
Claim 2
Dependent Claim 56 words
A thermistor comprising a body of ceramic material; two electrical leads embedded in mutually noncontacting relation in said body; said ceramic material having an electrical resistance which varies with temperature and with partial pressure of oxygen at elevated:temperatures characterised in that the body of ceramic material is substantially completely encapsulated in a coating of oxygen-impervious material.
Claim 3
Dependent Claim 14 words
A thermistor according to Claim 1 characterised in that said ceramic material is titania.
Claim 4
Dependent Claim 30 words
A thermistor according to Claim 1 or Claim 2 characterised in that said body has a density of from 72% to 85 of the theoretical density of the ceramic material.
Claim 5
Dependent Claim 22 words
A thermistor according to any one of Claims 1 to 3 characterised in that the oxygen impervious material comprises a borosilicate glass.
Claim 6
Dependent Claim 48 words
A temperature sensing device for an engine exhaust system comprising a housing adapted to be mounted in the engine exhaust system and a thermistor according to any one of Claims 1 to 4 supported in the housing for location in the exhaust gases passing through the exhaust system.
Claim 7
Dependent Claim 91 words
A device according to Claim 5 characterised in that a ceramic insulator having a forwardly-projecting sensor portion and a rearwardly-extending terminal portion is mounted in the housing, the forwardly-projecting sensor portion defining an open cavity within which the thermistor is received, said cavity having a depth sufficient to shield the thermistor from the flow of gaseous combustion products in the exhaust system, and passages extend rearwardly from the cavity within the ceramic insulator to the terminal portion, the electrical leads to the thermistor being received in respective ones of the passages.
Claim 8
Independent Claim 54 words
A method of manufacture of a thermistor comprising the steps of forming a powder of ceramic material having an electrical resistance which varies with temperature and with partial pressure of oxygen; preparing sinterable wafer from said ponder; affixing electrodes to said wafers; sintering said wafer and coating said body with an oxygen impervious encapsulant.
Claim 9
Independent Claim 54 words
A method of manufacture of a thermistor comprising the steps of forming a powder of ceramic material having an electrical resistance which varies with temperature and with partial pressure of oxygen; preparing sinterable wafer from said ponder; affixing electrodes to said wafers; sintering said wafer and coating said body with an oxygen impervious encapsulant.
Claim 10
Dependent Claim 31 words
A method according to Claim 7 wherein the wafer is sintered to produce a body having a density of from 72% to 85% of the theoretical density of the ceramic material.

References Cited (Backward Citations)

FR2115518A5 Cited
US3932246A Cited
US4011655A Cited
FR2280057A1 Cited
US4001758A Cited

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