Glow plug with improved composite sintered silicon nitride ceramic heater
US5304778A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 23, 1992 |
| Grant date | Apr 19, 1994 |
| Priority date | — |
| Expiry date | Nov 23, 2012 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC04B2237/765
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
An improved ceramic heater to be incorporated in a glow plug is described. The heater is made up of a ceramic core enclosed by two layers sintered together to form a unitary ceramic heater. All three component elements of the heater are composed of silicon nitride containing different concentrations of an electrically conductive ceramic substance, such as titanium nitride, titanium carbonitride or molybdenum disilicide. Each component additionally contains low amounts of sintering additives. The core of the heater has the highest concentration (46-75 vol. %) of the electrically conductive substance. The core enclosed in a ceramic layer which is an electrical insulator and is composed of silicon nitride, less than 28 vol. % of the electrically conductive ceramic substance and sintering additives. An outer layer over the core contains the electrically conductive ceramic substance in a concentration (33-50 vol. %) which is in between that in the core and that in the insulator layer. One end of the core is integrally connected to the outer layer over it. The ceramic heater is fitted into a glow plug housing. The core and the outer layer properly joined to appropriate connectors in the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.