US4635475A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hot element mass airflow sensor
Assignee: Motors Liquidation Co
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Filing: 1985-10-31
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Granted: 1987-01-13
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Expires: 2005-10-31
Abstract
Abstract To reduce the temperature compensation error of a hot element mass airflow sensor due to thermal radiation losses, the element is coated with a low emissivity material. In the case of a hot film sensor which comprises a thin metal foil resistor sandwiched between polymer layers, the outer surface is covered with a low emissivity coating comprising a thin metal layer which is highly reflective to infrared radiation. A circuit supplies energy to the element to heat it to a prescribed temperature; the power required to maintain that temperature correlates with the rate of convective energy loss to the airflow and thus to the rate of mass airflow.
Inventors
- 👤 Gregory S. Jones
- 👤 William H. Steele
- 👤 Glenn A. Gurtcheff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 19:47
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/68; G01F1/684; G01F1/688; G01F1/69; G01F1/692
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
118 words
A mass airflow sensor having a heated element subject to heat loss by convection and radiation wherein the rate of heat loss by convection is a measure of mass airflow and the rate of heat loss by radiation introduces error into airflow measurement, the heated element including; a resistive element positioned in an airstream; a circuit for electrically heating the element to a prescribed operating temperature and maintaining heat input at a rate equal to heat loss at the operating temperature, such rate being useful as a measure of mass airflow; and means for minimizing the heat loss by radiation comprising a low emissivity coating on the element whereby any error in mass airflow measurement is also minimized.
Claim 2
Dependent Claim
118 words
A mass airflow sensor having a heated element subject to heat loss by convection and radiation wherein the rate of heat loss by convection is a measure of mass airflow and the rate of heat loss by radiation introduces error into airflow measurement, the heated element including; a resistive element positioned in an airstream; a circuit for electrically heating the element to a prescribed operating temperature and maintaining heat input at a rate equal to heat loss at the operating temperature, such rate being useful as a measure of mass airflow; and means for minimizing the heat loss by radiation comprising a low emissivity coating on the element whereby any error in mass airflow measurement is also minimized.
Claim 3
Dependent Claim
48 words
A mass airflow sensor as described in claim 1 wherein the resistive element is a composite foil including a resistor covered by insulating layers and the low emissivity coating on the element is an outer layer on the composite foil comprising a material highly reflective to infrared radiation.
Claim 4
Dependent Claim
36 words
A mass airflow sensor as described in claim 1 wherein the resistive element is a thin resistive layer encapsulated between two polymer films and the low emissivity coating is a metallic layer covering the polymer films.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-01-12 | 1990-07-14 | 1991-01-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-01-12 | 1994-07-14 | 1995-01-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-01-12 | 1998-07-14 | 1999-01-13 | $7700.00 | Window Closed / Lapsed |