Workfunction based A/F sensor
US5310474A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 13, 1992 |
| Grant date | May 10, 1994 |
| Priority date | — |
| Expiry date | Jul 13, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/626
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A sensor for determining the stoichiometric air to fuel ratio (A/F) at the input to the cylinders of an internal combustion engine which is based on measuring the change in the workfunction of a material which occurs when the oxidizing and reducing species in the adjacent gas phase are at or near their stoichiometric ratio. In one method the sensor includes a material which is capable of thermionically emitting alkali metal or other appropriate ions into an exhaust gas atmosphere where they are subsequently collected by a nearby collector electrode and the magnitude of the emission current is measured. The interaction of the emitting surface with the gas phase reversibly changes the workfunction of the emitting surface from large to smaller values as that gas phase is varied through the stoichiometric ratio with respect to the amounts of the oxidizing and reducing species in the gas. Such a change in workfunction of the surface is accompanied by a change in the rate of the thermionic emission at the stoichiometric ratio thereby sensing that ratio in the gas phase which is proportional to the A/F at the input to the cylinders.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.