Patent Application
20050242212
This invention relates to fuel injectors for injecting atomized fuel spray into engine intake ports or manifold runners, and particularly to multiple orifice fuel spray director plates for such injectors, the plates having surfaces resistant to the formation of spray altering fuel deposits.
It is known in the art to provide automotive fuels with deposit controlling additives to avoid the formation of fuel deposits that might interfere with proper operation of fuel injectors or alter their desired spray patterns for atomizing fuel delivered to engine intake passages, such as manifold runners or cylinder intake ports. However, high temperatures reached during operation or after engine shutdown may result in fuel fractionation and deposition of high molecular weight material in the fuel as deposits on multiple orifice director plates. Further means for limiting such deposits have been desired to maintain fuel spray consistency.
For high pressure injectors delivering fuel through a single nozzle orifice directly into an engine combustion chamber, it has been proposed to limit deposits on the nozzle valve seat of combustion products formed in the chamber by altering the orifice configuration and by applying a coating to the needle valve seat. A carbon-based coating has been mentioned with alternatives of aluminum-based, ceramic and fluoropolymer-based materials. The conditions for direct injection of fuel to the combustion chamber differ from those for fuel injection into air intake passages. In the intake passages, pressures and temperatures are lower, combustion chamber deposits are not involved and multi-hole director plates may be used to direct the fuel spray.
The present invention provides a fuel injector for injecting fuel into an engine air intake passage, such as a manifold runner or an intake port. The injector is provided with a fuel deposit-resistant director plate formed as a generally planar sheet or thin plate having a plurality of spray openings for directing fuel spray into an air intake passage leading to a valve controlled cylinder intake port. The sheet has an inner side, adapted for exposure to vaporizable liquid fuel delivered to the director plate for injection, and an outer side, adapted for exposure to engine intake air and fuel spray mixing in the intake passage. The director plate includes at least a portion formed of a fuel deposit-resistant fluoropolymer material.
Numerous alternative embodiments include forming the entire director plate of the fluoropolymer material or coating a preformed substrate with a fluoropolymer coating. Various selected portions of the plate may be coated, preferably portions in or adjacent to the spray openings.
The family of fluoropolymers appears to be particularly suited for protecting a director plate against deposits of high molecular weight fuel components which would tend to coat the plate surface and form spray diverting or blocking deposits. PTFE (Teflon) material is an example of fluoropolymers considered suitable for this application. Other fluoropolymer materials which have adequate temperature and chemical resistance for use in engine fuel system applications could be used instead of PTFE. All the materials should be formulated to be conductive to avoid static charge buildup.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.
Referring now to the drawings in detail, numeral 10 generally indicates a needle valve-type fuel injector having a nozzle end 12 carrying a retainer sleeve 14 having a central opening in which is mounted a fuel director plate 16 having four spray directing orifices or spray openings 18 grouped near the center of the plate 16. The nozzle end 12 of the injector 10 is adapted to be received in an opening of an engine intake manifold or cylinder head connecting with an intake air passage, such as an intake runner or intake port, leading to a valve controlled engine cylinder, not shown.
During operation of the injector, high molecular weight fuel residuals and other substances in the fuel may form deposits 20, on inner or outer surfaces of the director plate 16 and sleeve 14. In time, these deposits may grow and interfere with the pattern of fuel spray through the spray holes 18 so as to adversely affect mixing of the air and fuel in the air intake passages.
In operation of injectors 24 and 48, after engine shutdown, fuel deposits can form on the inner and outer surfaces of the respective director plates 34, 56 and possibly on the inner peripheries of their orifices or spray openings 44, 46. Sources of the fuel deposits may include fractionation of the fuel as it evaporates. After shutdown of the engine, a small amount of fuel may be retained on the plate surfaces. When exposed to elevated temperatures and/or atmospheric pressure, it will slowly evaporate, distilling off the lighter compounds until only the high molecular weight material remains. This material will coat the exposed surfaces of the director plate and orifices without any chemical reactions being required. Polynuclear aromatics (PNAs) would form this type of deposit.
Components in the fuel may also react chemically with oxygen to form polar compounds. These polar compounds may be surface active and have an affinity for metal director plate spray openings or surfaces. They may have limited solubility in the fuel and precipitate out of solution, coating the surfaces of the plate plus the spray opening surfaces. Sulfur and nitrogen compounds also react with oxygen to form insoluble material that could also contribute to this type of deposit.
To prevent or resist formation of such fuel deposits on the sides and spray openings of the director plates 34, 56 of injectors 24, 48, the director plates may be made from or coated with deposit resisting conductive fluoropolymer materials such as polytetrafluoroethylene (PTFE), also known as Teflon. Other fluoropolymer materials which have adequate temperature and chemical resistance for use in engine fuel system applications could be used instead of PTFE. All the materials should be formulated to be conductive to avoid static charge buildup.
For example, the director plate 34 of injector 24 may be formed from a solid sheet of PTFE or other suitable fluoropolymer material. Alternatively, the sheet may be formed of a suitable substrate and coated with the PTFE or other deposit resisting material.
In the case of injector 48, shown in
As an example,
While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.
