Abstract:
A combustion catalyst device for an internal combustion engine of the type including an engine unit a cylinder head, and a cylinder head gasket, including multilayered crimp or crimpless seals arranged therebetween, and cylinders, each housing a moving piston defining a combustion chamber. The catalyst is deposited on a catalyst support disposed in the combustion chamber at a position level with the edge of the cylinder head gasket.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of copending application Ser. No. 08/624,550, filed May 31, 1996, which was the 35 USC 371 national phase of International application PCT/FR95/01043 filed on Aug. 2, 1995, which designated the United States. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is related to a combustion catalyst device for an internal combustion engine. 
     2. Description of Background and Relevant Information 
     The current problems of pollution generated by internal combustion engines are well known, whether such engines use fuels comprising gas, gas-oil, liquefied petroleum gas or compressed natural gas. Emissions emanating from these internal combustion engines are of several types, including unburnt hydrocarbons, carbon monoxides, nitrogen oxides and particles. 
     Systems already exist that make it possible to reduce certain emissions. For instance, injection systems associated with an electronic control allow for loop-through operations. In these systems, a probe placed in the exhaust makes it possible to analyze the gases and control the determination during intake, in association with a catalytic muffler and in manner so as to make it work by oxidation or reduction with the highest efficiency. 
     In practice, conventional catalysts can be started, as is the case for oxygen probes, only if the temperature of the exhaust gases and the catalytic structure are sufficiently high. Heating systems have been developed to be arranged immediately upstream of the catalysts, but such systems remain complex and expensive. 
     Unburnt hydrocarbon emissions result essentially from four factors: 
     a) the quality of the combustion itself; 
     b) trapping of the hydrocarbons in the ullages of the combustion chamber which are very difficult to reach for complete burning; 
     c) the phenomena of hydrocarbon absorption/desorption in the oil films; and 
     d) the deposits capable of constituting substantial hydrocarbon retaining sources. 
     The trapping of the hydrocarbons in the ullages, which are difficult to reach for complete burning, constitutes the major source of unburnt gases that can reach up to 70% of the total evacuated hydrocarbons. The ullages are located between the first bearer and the cylinder and in the fire rings. The critical micro-volumes in the vicinity of the seats and valves are also a part of the ullages. 
     In the case of diesel engines, substantial quantities of unburnt particles are formed. If these particles are in hot zones, they will burn in the presence of oxygen. Those that could not burn are found in the exhaust conduits downstream of the combustion chambers. 
     In the case of natural gas, the emissions are essentially composed of methane, even with the use of catalytic converters. Indeed, the atoms of the methane molecule have very substantial bond strengths and the rate of combustion is low, which explains these high levels of emission. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to treat the combustion gases, in a catalytic fashion, directly in the combustion chamber. Another object is to provide a solution that operates in a cold engine, from the first revolutions of the engine. A further object of the invention is that the system remains inexpensive and it can be adapted to all types of internal combustion engines. 
     In addition, the solution proposed by the invention must allow for an adaptation, regardless of the type of cylinder head gasket used, including multilayered crimp or crimpless seals. 
     In this fashion, a combustion catalyst device is adapted for an internal combustion engine of the type comprising an engine unit a cylinder head and a cylinder head gasket, including multilayered crimp or crimpless seals arranged therebetween, and cylinders, each housing a moving piston defining a combustion chamber. The catalyst is deposited on a catalyst support disposed in the combustion chamber at a position level with the edge of the cylinder head gasket. 
     According to a particular embodiment, the catalyst support is the crimp or the fire ring of the cylinder head gasket itself. The support can be an element attached to the crimp or integrated therein. 
     In certain cases, this attached element projects in the combustion chamber and is spaced from the crimp level with the edge of the cylinder head gasket so as to provide an ullage forming a thermal shield between this crimp and this element. According to a particular embodiment regarding a crimpless multilayered cylinder head gasket, the catalyst support is an appendage formed by the projection, in the combustion chamber, of a portion of at least one of the layers of this gasket. 
     According to a variation of this particular embodiment, at least one of the layers is deformed to form a shield on the outer surface from which the catalyst is deposited. 
     According to an improvement of the invention, the device comprises heating means that are arranged in the immediate vicinity of the catalyst support. These heating means are isolated from the combustion chamber by the catalyst support. 
     According to a particular embodiment, the heating elements comprise an electrical resistance. The support and/or the heating means are possibly arranged on one or more sectors on the periphery of the edge of the cylinder head gasket. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described hereinafter, according to a particular non-limiting embodiment of the invention, with reference to the annexed drawings in which: 
     FIG. 1 is a schematic cross-sectional view of a cylinder with an attached catalyst support; 
     FIG. 1A is a schematic cross-sectional view of a cylinder with a catalyst support constituted by the crimp itself; 
     FIG. 2 is a cross-sectional view of a variation of the support according to the invention; 
     FIG. 3 is a cross-sectional view of another variation with a support projecting in the combustion chamber; 
     FIG. 4 is a cross-sectional view of a variation of the form of the crimp itself; 
     FIGS. 5 and 5A are variations with an ullage forming a thermal shield arranged respectively in the upper portion and in the lower portion; 
     FIGS. 6 and 7 are variations with heating means; 
     FIGS. 8, 9, 10, and 11 are variations of embodiment in the case of multilayered seals; 
     FIGS. 12A and 12B are diagrams of complete resistances with sectors; and 
     FIGS. 13 and 14 are schematic representations of the resistance positions and catalyst deposits. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a schematic view of a cylinder head gasket 10, mounted between an engine unit 12 and a cylinder head 14. In this figure, a portion of the cylinder 16 appears in which a piston, not shown for simplification reasons, determines the variable volume referred to as combustion chamber 18. 
     The cylinder head gasket 10, in a known system, comprises a matrix 20 and a metallic crimp portion 22, which is positioned at a vicinity of the edge of the combustion chamber, and specifically, at the periphery of the combustion chamber. 
     In the following description, the catalyst support will be referenced by the numeral 24. In FIG. 1, the catalyst support 24 is an attached element of the annular type, concentrically arranged at the crimp 22 with a catalyst layer 26 on the surface and in contact with the combustion chamber 18, i.e., exposed to the combustion chamber. 
     In the embodiment of FIG. 1A, the catalyst support 24 is the outer surface of the crimp 22 of the cylinder head gasket, i.e., the surface placed in contact with the combustion chamber 18. Thus, in this embodiment, the catalyst support is integrated into the crimp of the gasket. The catalyst 26 is deposited on the support by any appropriate means, and in this case, it is a projection or quenched deposit. 
     The catalytic structure generally comprises a steel or ceramic porous matrix associated with noble metals. Thus, in the example shown, the support is metallic and is coated with a layer &#34;rendered&#34; porous which is, in turn, coated with metals or materials having a catalytic effect such as platinum, palladium or rhodium. 
     In FIGS. 2, 3 and 4, the catalyst support 24 is modified in its form. In FIG. 2, the support 24 has a profile that is identical to that of the crimp 22, and it is superimposed on the outer surface thereof, in the manner of a double crimp. 
     The variation of FIG. 3 shows a support that is also blocked between the crimp 22 and the cylinder head 14, but it extends toward the inside of the combustion chamber 18. The developed surface, upon contact with the gases contained in the combustion chamber 18, is very substantial. A deformation 28 of the stamping type, provided level with the edge of the cylinder head gasket, imparts, to the portion of this support projecting in the combustion chamber 18, an elastic effect which tends to press it against the cylinder head 14. This deformation allows for an efficient centering of this support with respect to the crimp. 
     The catalyst is deposited, as in the preceding embodiments, on the surface opposite the combustion chamber 18. In FIG. 4, the crimp 22 has a particular profile, such that a wing 30 projects in the combustion chamber. The wing 30 is obtained by bending the crimp 22 into an S-shape. The wing 30 is likewise pressed on the cylinder head so as to limit the disturbances in the combustion chamber 18, and to prevent any contact with the moving elements in the cylinder 16. 
     The catalyst support of 24 FIGS. 5 and 5A is characterized in that the support is spaced apart from the crimp 22. An ullage forming a thermal shield 32 is thus provided. The support 24 comprises a wing 34 folded back around the crimp 22 of the cylinder head gasket. In the variation of FIG. 5, the wing 34 is blocked by its heel between the gasket 10 and the cylinder head 14, and the wing 34 is folded back downwardly, whereas in the variation of FIG. 5A, the heel is blocked between the engine unit 12 and the cylinder head gasket 10, the wing 34 being folded back upwardly. 
     In FIG. 6, an alternative embodiment is shown with a support 24 and means 36 for heating this support. Heating means 36 comprises an electric resistance 38 mounted beneath the crimp 22, which isolates resistance 38 from the combustion chamber. The crimp 22 constitutes the catalyst support as in the variation of FIG. 1. 
     In FIG. 7, the resistance 38 is arranged in a catalyst support 24 independent of the crimp 22. In this case, the support projects within the combustion chamber 18. 
     FIG. 8 shows a multilayered seal 50, comprising a metallic only or metal-elastomer composite. Seal 50 comprises, in a known fashion, a plurality of superimposed layers, in this case three layers 52, 54, and 56, arranged respectively at the upper portion, median portion and lower portion. In the embodiment shown in FIG. 8, the median layer 54 is extended by an appendage 26 originated from the layer itself, projecting in the combustion chamber, this appendage forming the catalyst support itself. The catalyst can also be arranged, in a complementary fashion, on the upper and lower surfaces of the upper layer and lower layer, for the portion that is inside the combustion chamber. It is noted that the boss 58 of the layers enabling the seal to ensure the sealing, is borne by the upper layer and the lower layer. 
     In FIG. 9, the only difference consists in providing the sealing boss solely on the median layer, one of the upper and lower layers being folded, the other planar. 
     The variation of FIG. 10 provides a folded lower layer, forming a shield 60, around the median layer so as to join the upper layer that is set back from this median layer. The boss is borne by the sole median layer and the catalyst 26 is borne by the outer surface of the shield. 
     For the variation of FIG. 11, it is noted that the catalyst 26 is borne by the upper layer that is projecting with respect to the other layers. 
     Such a variation makes it possible to place the layer carrying the catalyst in the immediate vicinity of the upper portion of the combustion chamber, without hindering the displacement of the piston. This variation has a real advantage in certain applications. In FIG. 12A, the resistance is represented schematically. In FIG. 12B, the resistance is only provided on a sector S of the periphery of the combustion chamber. 
     In the case of prechamber diesel engines, shown in FIG. 13, there is a combustion prechamber 40, and the gas catalytic treatment has an advantage being in the vicinity of the exhaust valve. In the case of prechamber diesel engines, the heated sector S is limited. 
     FIG. 14 relates to engines with spark ignition and shows the heating of sector S opposite the spark plug 42. This local electric heating can be controlled electronically by the engine computer and by a specific electronic box. This supply of heat presents a particular interest in cold temperatures, during starts or certain ranges of operation, at low load for example. The energy to be supplied is of a few hundred watts at the maximum. Indeed, this quantity is adapted as a function of the material, specific heat, the heated mass, the activity and quantity of the catalytic noble materials, and the desired temperature difference. The catalytic elements thus localized in the combustion chamber can be deposited by more sophisticated means such as vacuum deposition, which makes it possible to impregnate the surfaces to be treated and to improve the bonding. These catalytic elements are deposited on metallic or ceramic primary layers having, after treatment, large impregnation surfaces. Any attached element or any element demarcating the combustion chamber, or a combination of both, can be envisioned as a support.