Fluid sprinkling – spraying – and diffusing – Including valve means in flow line – Reciprocating
Reexamination Certificate
2000-06-08
2001-07-31
Scherbel, David A. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Including valve means in flow line
Reciprocating
C239S585100, C239S584000, C239S104000
Reexamination Certificate
active
06267307
ABSTRACT:
The invention relates to fuel injectors for spark-ignition internal combustion engines in which the fuel is injected directly into the combustion chambers of the engine.
The invention relates to a fuel injector of the type in which the injector has a tip having at least one outlet orifice from which fuel enters an engine combustion chamber when the injector is in an open position and fuel is delivered to the outlet orifice, a movable throttle being moved back from a seat by actuating means against return means, generally resilient, which return the throttle to its seat and retain it against the latter when the injector is in a closed position.
Intermittently operated fuel injectors of this type are known in numerous designs and are used more particularly with diesel engines, in which the throttle forms part of a mobile assembly, sometimes referred to as a plunger, which, in an injector of the electromagnetic type, is displaced between closed and open positions by a power supply of a solenoid coil arranged in the body of the injector and moving the mobile assembly away from the throttle seat against at least one return spring, which closes the injector by applying the throttle against its seat as the electric supply is stopped.
If a fuel injector of the type described above is used in a system for injecting fuel directly into the combustion chambers of an engine, it is known that at least the tip of the injector opens directly into one combustion chamber. The injector is subjected to considerable stress as a result of this arrangement, in particular high stress due to heat during the combustion phases of the engine cycles.
In order to protect a fuel injector of a diesel engine against oxidation and corrosion during operation and in particular against cyclical oxidation and corrosion at temperatures which may be as much as 1000° C., it has been proposed that certain surfaces of the injectors should be covered with a ceramic coating, in particular in vitreous phase, or that certain components of the injector be made from wear-resistant materials or alternatively that the injector should be used in conjunction with complementary components made from these materials, for example ceramic or steel.
In particular, the article entitled “Comparative evaluation of high temperature coatings for corrosion protection of fuel injector tips” by MARK VAN ROODE and LULU HSU in “Surface and Coatings Technology”, 32 (1987), pages 153 to 167, proposes that a high-performance coating be deposited on injector tips made from a nickel and chrome alloy by a physical vapour deposition process using an electron beam, in particular a ceramic in vitreous phase, to provide additional protection against deterioration due to oxidation and corrosion.
Also with a view to protecting injectors of a similar type against corrosion, U.S. Pat. No. 4,266,729 proposes that the tip of the mobile assembly forming the throttle and the disc or bead having the outlet orifice, which is simultaneously the calibration orifice in the injector design in question, be made from an anti-corrosion material such as steel, a ceramic or an industrial glass in order to prevent the outlet orifice from becoming clogged due to corrosion. U.S. Pat. No. 4,991,771 proposes using a pair of ceramic rings, one being arranged on each of the two sides of an injector outlet orifice in order to reduce corrosion or erosion. U.S. Pat. No. 4,592,506 proposes an injector with a cone-shaped pintle and an injection nozzle ring made from a wear-resistant ceramic material and EP-A-677 656 discloses a mobile assembly or injector plunger in which the plunger and plunger tip, forming the throttle, are made from a wear-resistant material such as a ceramic or appropriate metals, in particular steel, in order to withstand the wear, deformation and fatigue to which these components are subjected during service.
The designs outlined above which have components made totally from ceramic, either to replace metal components of earlier, more conventional designs or to co-operate with injectors of a conventional design, have the disadvantage of being expensive on the one hand and unsatisfactory in terms of metering stability on the other (alignment of outflow sections at the injector tips). In effect, it is impossible to position ceramic beads provided with orifices of the same diameter as the outlet and optionally calibrating orifices of the injector tips in perfect coaxial alignment with the outlet orifice.
Furthermore, these designs are intended to protect the injectors against corrosion and oxidation.
However, these designs are not suitable as a means of protecting petrol injectors used in direct injection systems against deposits of carbon oil which, depending on the position of the injector under specific conditions and the surface state of its tip opening into the combustion chamber, can lead to significant deterioration in the performance of the injector and can do so within a very short period of engine operation (approximately 20 hours).
In effect, when a direct-injection injector is closed, the output rate of the fuel is low which promotes a deposit of liquid fuel on the surface of the injector tip due to capillary action. Furthermore, since this surface is metal, it has a high electrochemical potential and, depending on the manufacturing process, a micro-structure with a not insignificant roughness. Modem fuels, in particular petrol, are of a complex chemical composition and contain numerous aromatic compounds. When the liquid fuel deposited on the surface of the injector tip is suddenly subjected to high temperature, either by the subsequent combustion phase or, when the engine is in a hot condition and is stopped, by internal thermal convection, this liquid fuel is caused to decompose by a cracking process, which after a short time of engine operation can lead to deposits of carbon oil on the surface of the injector tip reducing its performance, because, instead of emitting a regular jet of fuel into the combustion chamber, the jet is altered and its orientation may be sharply modified, and the delivery rate may be reduced, which disrupts preparation of the charge injected into the combustion chamber which in turn can lead to a serious and unacceptable degradation in combustion (combustion may fail or there may only be partial combustion, both of which will lead to unacceptable emission of noxious gases).
The problem underlying the invention is to propose a gasoline injector for a direct-injection system which is better suited than those disclosed in the prior art to the different requirements of practical operation, in particular with regard to protecting against contamination by carbon oil deposits, i.e. hydrocarbon residues, and to do so even if the injector is located close to an ignition plug in a combustion chamber.
In particular, the objective of the invention is to propose a gasoline injector which is protected to prevent changes in the fuel delivery rate characteristics and the geometry of the jets of atomised petrol which might result from deposits of hydrocarbon residues on the injector tip, given that, compared with a clean injector (one with no carbon oil deposit), an injector which has a deposit of carbon oil on the surface of its tip may deliver a petrol jet into the combustion chamber which is deflected and deformed, supplied at a rate which may be reduced by 25 to 35% depending on the injection duration, i.e. depending on the width of the electric pulse controlling an electromagnetic injector.
To this end, the gasoline injector proposed by the invention, of the type outlined above, is characterised in that it has a ceramic coating deposited on the external face of the tip, at least around and immediately downstream of its or each outlet orifice relative to the direction in which the gasoline is delivered.
Advantageously, immediately downstream of and around said outlet orifice or each one thereof, the external face of the tip has at least one kink bounding a recess in the external face of the tip and the ceramic coating is deposited at le
Ganey Steven J.
Magneti Marelli France
Piper Marbury Rudnick & Wolfe
Scherbel David A.
LandOfFree
Fuel injector with anti-scale ceramic coating for direct... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuel injector with anti-scale ceramic coating for direct..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel injector with anti-scale ceramic coating for direct... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2557060