(19)
(11)EP 3 329 107 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
26.06.2019 Bulletin 2019/26

(21)Application number: 16745593.0

(22)Date of filing:  20.07.2016
(51)International Patent Classification (IPC): 
F02F 3/28(2006.01)
F02B 23/06(2006.01)
F01B 7/14(2006.01)
F02M 61/14(2006.01)
F02B 25/08(2006.01)
F02M 26/14(2016.01)
F02B 75/28(2006.01)
(86)International application number:
PCT/US2016/043127
(87)International publication number:
WO 2017/023550 (09.02.2017 Gazette  2017/06)

(54)

OPPOSED-PISTON ENGINES WITH SKEWED COMBUSTION CHAMBER

GEGENKOLBENMOTOREN MIT SCHIEFER BRENNKAMMER

MOTEURS À PISTONS OPPOSÉS AVEC CHAMBRE DE COMBUSTION INCLINÉE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 31.07.2015 US 201514815747

(43)Date of publication of application:
06.06.2018 Bulletin 2018/23

(73)Proprietor: Achates Power, Inc.
San Diego, CA 92121 (US)

(72)Inventor:
  • VENUGOPAL, Rishikesh
    San Diego, CA 92130 (US)

(74)Representative: Hanna Moore + Curley 
Garryard House 25/26 Earlsfort Terrace
Dublin 2, D02 PX51
Dublin 2, D02 PX51 (IE)


(56)References cited: : 
US-A- 1 582 792
US-A1- 2013 036 999
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    RELATED APPLICATIONS



    [0001] US 13/066,589, now US patent 8,800,528; US 13/136,954, now US patent 8,820,294; US 14/117,831, published as US 2014/0083396; US 13/843,686, published as US 2013/0213342; US 14/026,931, published as US 2014/0014063; US 14/074,580, published as US 2015/0122227; and, US 14/675,407 disclose engines related to the subject-matter of the present invention.

    FIELD OF THE DISCLOSURE



    [0002] The field includes opposed-piston engines in which a combustion chamber is defined between end surfaces of pistons disposed in opposition in the bore of a cylinder. More particularly, the field includes opposed-piston engines with combustion chambers having shapes that promote mixing of charge air with injected fuel.

    BACKGROUND OF THE DISCLOSURE



    [0003] The related patent applications describe two-stroke cycle, compression-ignition, opposed-piston engines in which pairs of pistons move in opposition in the bores of ported cylinders. A two-stroke cycle opposed-piston engine completes a cycle of engine operation with two strokes of a pair of opposed pistons. During a compression stroke, as the pistons begin to move toward each other, charge air is admitted into the cylinder, between the end surfaces of the pistons. As the pistons approach respective top center ("TC") locations to form a combustion chamber the charge air is increasingly compressed between the approaching end surfaces. When the end surfaces are closest to each other, near the end of the compression stroke, a minimum combustion chamber volume ("minimum volume") occurs. Fuel injected directly into the cylinder mixes with the compressed charge air. Combustion is initiated when the compressed air reaches temperature and pressure levels that cause the fuel to begin to burn; this is called "compression ignition". Combustion timing is frequently referenced to minimum volume. In some instances, injection occurs at or near minimum volume; in other instances, injection may occur before minimum volume. In any case, in response to combustion the pistons reverse direction and move away from each other in a power stroke. During a power stroke, the pistons move toward bottom center ("BC") locations in the bore. As the pistons reciprocate between top and bottom center locations they open and close ports formed in respective intake and exhaust locations of the cylinder in timed sequences that control the flow of charge air into, and exhaust from, the cylinder.

    [0004] Combustion is influenced by the degree to which compressed charge air is mixed with injected fuel. Motion and turbulence of charge air in the cylinder are critical factors in facilitating air/fuel mixing and combustion. In an opposed-piston engine, pressurized charge air may enter the cylinder in a tangential direction, which causes the formation of a vortex structure (commonly referred to as "swirl") that spirals longitudinally in the cylinder, across the direction of fuel injection. The bulk swirling motion breaks up the injected fuel streams and entrains fuel droplets into the moving charge air. In the short amount of time preceding ignition it is desirable to intensify the turbulence of charge air motion by generating additional bulk air flow structures. For this purpose, two-stroke, opposed-piston engines are equipped with pistons having crowns with contoured end surfaces that interact with swirling charge air in the cylinder and with squish flow of charge air from the circular peripheries of the piston end surfaces. The interaction produces additional bulk motion structures (commonly referred to as "tumble") in the form of vortexes oriented transversely or tangentially to the swirl vortex. The result is complex, turbulent charge air motion in the combustion chamber that facilitates combustion and that continues to encourage oxidation of unburned fuel and the products of combustion as the power stroke begins.

    [0005] The related applications are directed to two-stroke cycle, compression-ignition, opposed-piston applications in which the piston end surfaces have shapes that add tumble to the bulk airflow structures. In these applications the combustion chamber is defined by bowls running along end surface ridges that extend on opposite sides of a chamber centerline. Concave inner surfaces of the bowls and ridges guide air flow and fuel plumes in the combustion chamber. Convex outer surfaces of the ridges act like ramps to generate tumble from squish flows. While these ridges do contribute to production of tumble, they also pose significant challenges to engine operation and piston thermal management. The ridges present irregular contours with sharp edges that protrude outwardly from the piston end surfaces and cause hot spots in the piston crowns when combustion occurs. The hot spots impair combustion, which reduces the engine's efficiency. They also produce irregular thermal profiles on crown undersurfaces, which are difficult to manage and which necessitate complex internal piston structures to transport liquid coolant. Finally, the ridged end surfaces and the required cooling structures make the pistons difficult to manufacture and add to the costs of engine production and maintenance.

    [0006] US 1,582,792 discloses an example of a diesel engine.

    SUMMARY



    [0007] The present application provides a two-stroke cycle, compression ignition, opposed-piston engine and a method of operating same in accordance with the claims which follow.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0008] 

    FIG. 1 is a schematic illustration of an opposed-piston engine of the prior art.

    FIG. 2 is an isometric view of a piston of the prior art which has an end surface shaped to form a combustion chamber with the end surface of a counterpart opposed piston

    FIG. 3 is an isometric view of a piston according to this disclosure.

    FIG. 4 is a plan view of an end surface of the piston of FIG. 3 showing a bowl formed in the end surface; FIG. 4A is a longitudinal diametric sectional view of the facing sidewalls of the bowl, the view being through a longitudinal plane that is orthogonal to a diameter of the end surface.

    FIGS. 5A, 5B, and 5C are longitudinal diametric sectional views of a combustion chamber formed between the opposing end surfaces of a pair of pistons having end surfaces shaped as per FIG. 4, in which the views correspond to parallel planes indicated by lines A-A, B-B, and C-C of FIG. 4.

    FIG. 5D is a longitudinal diametric sectional view of the combustion chamber of FIGS. 5A, 5B, and 5C, in which the view corresponds to the line D-D of FIG. 4, which is orthogonal to the lines A-A, B-B, and C-C of FIG. 4.


    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS



    [0009] FIG. 1 is a schematic representation of a two-stroke cycle internal combustion engine 8 of the opposed-piston type that includes at least one cylinder 10. The cylinder includes a bore 12 and longitudinally displaced intake and exhaust ports 14 and 16 machined or formed in the cylinder, near respective ends thereof. Each of the intake and exhaust ports includes one or more circumferential arrays of openings in which adjacent openings are separated by a solid portion of the cylinder wall (also called a "bridge"). In some descriptions, each opening is referred to as a "port"; however, the construction of a circumferential array of such "ports" is no different than the port constructions in FIG. 1.

    [0010] Fuel injection nozzles 17 are secured in threaded holes that open through the side surface of the cylinder. Two pistons 20, 22 are disposed in the bore 12 with their end surfaces 20e, 22e in opposition to each other. For convenience, the piston 20 is referred to as the "intake" piston because of its proximity to the intake port 14. Similarly, the piston 22 is referred to as the "exhaust" piston because of its proximity to the exhaust port 16. Preferably, but not necessarily, the intake piston 20 and all other intake pistons are coupled to a crankshaft 30 disposed along one side of the engine 8; and, the exhaust piston 22 and all other exhaust pistons are coupled to a crankshaft 32 disposed along the opposite side of the engine 8.

    [0011] Operation of an opposed-piston engine such as the engine 8 with one or more ported cylinders (cylinders with intake and exhaust ports formed near ends thereof) such as the cylinder 10 is well understood. In this regard, in response to combustion the opposed pistons move away from respective TC positions where they are at their innermost positions in the cylinder 10. While moving from TC, the pistons keep their associated ports closed until they approach respective BC positions where they are at their outermost positions in the cylinder and the associated ports are open. The pistons may move in phase so that the intake and exhaust ports 14, 16 open and close in unison. Alternatively, one piston may lead the other in phase, in which case the intake and exhaust ports have different opening and closing times.

    [0012] As charge air enters the cylinder 10 through the intake port 14, the shapes of the intake port openings cause the charge air to rotate in a vortex 34 about the cylinders longitudinal axis, which spirals in the direction of the exhaust port 16. A swirl vortex 34 promotes air/fuel mixing, combustion, and suppression of pollutants. Swirl velocity increases as the end surfaces 20e and 22e move together.

    [0013] Figure 2 is an isometric view of a prior art piston for an opposed-piston engine that is taught in related US patent 8,800,528. The piston 50 has an end surface 51 that is shaped to form a combustion chamber with the end surface of an opposing piston. The end surface 51 of the piston has a periphery 53 surrounding a bowl 54 defining a concave surface 56. The concave surface 56 includes a first portion 58 curving away from the periphery 53 toward the interior of the piston 50. The concave surface 56 further includes a second portion 62 curving away from the first portion 58 and protruding outwardly in part from the end surface 51. A convex surface 64 opposite the bowl 54 curves away from the periphery 53 and protrudes outwardly from the end surface 51. The convex surface 64 meets the second portion 62 of the concave surface 56 to form a ridge 70 therewith. The ridge 70 has an edge 72. The end surface structure is provided on both pistons and the pistons are disposed in the bore of a ported cylinder with their end surfaces oriented to place complementary curved surfaces of the end surface structures in opposition so as to define a combustion chamber. The combustion chamber space defined between these two end surfaces has a geometry that reinforces and sustains a charge air tumble motion which encourages fuel/air mixing. However, when combustion occurs, the edge 72 of the ridge becomes an elongated, curved hot spot.

    [0014] Skewed Combustion Chamber Construction: Opposing pistons constructed according to this disclosure have flat end surfaces. An oblong concave bowl (also called a "recess" or a "cavity") with a skewed construction is formed in each end surface. The pistons are rotationally oriented in a cylinder bore so as to align their bowls in opposition. Near the end of a compression stroke when the pistons are nearest together, the opposing bowls define a combustion chamber having a skewed shape that interacts with swirl to generate tumble flow structures in bulk air motion. Opposed pairs of notches in the end surfaces form diametrically-opposed openings through which fuel is injected into the combustion chamber. The flat aspect of the end surface eliminates hot spots caused by outwardly-extending ridges.

    [0015] Piston Construction: The flat end surface of each piston meets a piston sidewall at a peripheral edge. The peripheral edge has a circular shape that is centered on a longitudinal axis of the piston and disposed at a single longitudinal level of the piston. A pair of notches is formed in the end surface. The notches are positioned in opposition on the peripheral edge, in alignment with an end surface diameter. The concave bowl formed in the end surface has an oblong shape that is elongated along the end surface diameter, between the notches. The bowl is flanked on either side by flat end surface portions that extend to the peripheral edge. The bowl has opposing sidewalls and a curved bottom portion which connects the sidewalls smoothly in a vertical section, wherein a maximum depth of the bowl is measured from a point of the bottom portion which is offset from, that is to say, positioned to one side of, a plane containing the piston's longitudinal axis and the end surface diameter.

    [0016] FIG. 3 is an isometric view of a piston 100 for an opposed-piston engine; FIG. 4 is a plan view of the end surface of the piston. Referring now to FIGS. 3 and 4, the structural features of piston end surfaces that define the combustion chamber are essentially the same, if not identical, for each piston; accordingly, the piston 100 shown in these figures represents intake and exhaust pistons. The piston 100 comprises a crown 102 attached to, affixed to, or manufactured with a skirt 104 to form a continuous cylindrical sidewall of the piston. The crown 102 comprises a flat end surface 108. The sidewall and end surface 108 meet at a peripheral edge 110. The peripheral edge 110 has a circular shape that is centered on the longitudinal axis 112 of the piston as shown in the plan view of FIG. 4. A pair of notches 118 and a concave bowl 120 are formed in the end surface 108. The notches 118 are positioned in opposition in the peripheral edge 110, in alignment with a diameter 122 of the piston at the end surface.

    [0017] FIG. 4A is a longitudinal, diametric sectional view of the facing sidewalls of the bowl 120, the view being through a longitudinal plane that is orthogonal to a diameter of the end surface. With reference to FIGS. 4 and 4A, the concave bowl 120 has an oblong shape that is elongated along the diameter 122 and that connects smoothly with each notch 118. The concave bowl 120 is abutted on opposing sides of its opening by flat end surface portions 108a and 108b that extend to the peripheral edge 110. The peripheral edge 110 and the flat end surface portions 108a and 108b are disposed at a single longitudinal level of the piston where an end surface plane PES, orthogonal to the longitudinal axis 112 and intersecting the end surface diameter 122, is defined.

    [0018] As shown in the sectional view of FIG. 4A, the concave bowl 120 has opposing sidewalls 123 and 124 and a curved bottom portion 125 which connects the sidewalls smoothly in the illustrated vertical section. With reference to FIGS. 4 and 4A, the sidewall 123 includes a rounded lip 1231 where the sidewall 123 is connected smoothly to the end surface portion 108a, and the sidewall 124 includes a rounded lip 1241 where the sidewall 124 is connected smoothly to the end surface portion 108b.

    [0019] As shown in the sectional view of FIG. 4A, a bowl depth D is the maximum distance between the curved bottom portion 125 and the end surface plane PES that is measured in each of a succession of vertical sections taken along the diameter 122. There is a maximum depth Dmax of the concave bowl 120 in a vertical section. According to this disclosure, the bowl 120 is constructed such that each bowl depth D is measured from a point of the bottom portion 125 that is offset in an orthogonal direction from (positioned to one side of) a longitudinal cut plane PL. The plane PL contains the piston's longitudinal axis and the diameter 122; and, the planes PL and PES are mutually orthogonal. In some instances, the bowl depth D may diminish smoothly from a Dmax position aligned with the midpoint M of the diameter 122, toward each of the notches 118. As seen in the plan view of FIG. 4, the depth D positions are traced along the bottom portion 125 by a curved arc shape 126 having a concave side that faces the plane PL. In some cases where the Dmax position is aligned with the midpoint M, the maximum depth D may diminish at the same rate in each direction from the midpoint so that the curved arc shape is symmetrical with respect to the plane PL. Although one such instance is shown in FIGS. 4 and 4A, it is not intended to be limiting. For example, the bowl depth D may diminishes smoothly from a maximum bowl depth Dmax that is located between the midpoint M of the end surface diameter in plan and a respective one of the notches 118.

    [0020] As shown in the sectional view of FIG. 4A, the offset of the bowl depth locations along the curved arc 126 causes the sidewall 123 to slope more steeply toward the bottom portion 125 than the sidewall 124. The sidewall 124 has a deflection portion A which is approximately linear. The deflection portion A is inclined on the inside of the bowl 120 at a chute angle α with respect to the end surface plane PES. In some instances, the chute angle α diminishes smoothly from a maximum value (αmax) position relative to the midpoint M of the diameter 122 toward each of the notches 118. In such instances, the chute angle α may diminish at the same rate in each direction from the midpoint M, toward a respective notch 118. Although one such instance is shown in FIGS. 4 and 4A, it is not intended to be limiting.

    [0021] As shown in the sectional view of FIG. 4A, the steepness of the slope of the sidewall 123 is dependent on a depth D and an offset OD. The steepness is further dependent on a distance along a line L that is orthogonal to the plane PL, and that extends between the plane PL and a point where the curvature of the lip 123I transitions to the flat end surface portion 108a.

    [0022] The intended effect of locating the maximum depths D to one side of the longitudinal cut plane is to give the bowl 120 a skewed shape in a longitudinal diametric sectional view. The shape and degree of the bowl's skew can be altered by variation of one or more of the bowl parameters D, α, L, and OD, and possibly others. Further, although the bowl's skew seen in FIG. 4A is leftward, it should be evident that the skew may be rightward.

    [0023] The longitudinal diametric sectional views of a combustion chamber seen in FIGS. 5A, 5B, and 5C show a combustion chamber 150 formed between end surfaces of two pistons 100' and 100" disposed in opposition in the bore of a cylinder 160. These sectional views are transverse to a combustion chamber centerline CC, which is best seen in FIG. 5D. For example, these sectional views are orthogonal to the chamber centerline CC. The end surfaces 108' and 108" are constructed according to FIGS. 3, 4, and 4A. The pistons 100' and 100" are rotated on their longitudinal axes to positions in which the notches 118 of the end surfaces are aligned in longitudinal opposition, and the bowls 120 are mutually oriented so that deflection portions A' and A" are in opposition respectively with steeply curved sidewalls 123" and 123'. This disposes the skewed shapes of the bowls in an opposed facing alignment that defines a combustion chamber 150 having a shape that is rotationally skewed in the longitudinal sectional views of FIGS. 5A, 5B, and 5C. Although the figures illustrate a rotational skew in a clockwise direction, it should be evident that the pistons may be rotated to orient the skew in a counterclockwise direction. The combustion chamber's shape is rotationally skewed because the deepest portions of the bowls 120' and 120" are disposed on opposite sides of a longitudinal plane PCYL that contains a longitudinal axis 152 of the cylinder and that coincides with the longitudinal planes of the pistons 100' and 100". Further, the skew is centered on the combustion chamber centerline CC, which is aligned with the piston diameters 122. In a longitudinal sectional view of the combustion chamber shown in FIG. 5D, which is orthogonal to the views of FIGS. 5A, 5B, and 5C, the combustion chamber has an elongated shape with opposite end portions that taper along the combustion chamber centerline CC toward fuel injectors 165 that are mounted in a cylinder sidewall 170. The fuel injectors 165 are aligned with the combustion chamber centerline CC and positioned to inject opposing fuel sprays into the combustion chamber 150 through injection ports that are defined between opposing notches 108' and 108". For example, the fuel injectors 165 may be constructed to emit fuel sprays that comprise a plurality of plumes having injection axes that are either collinear with the chamber centerline CC, in the manner illustrated in FIGS. 10A-10C of related US patent 8,820,294, or that are tangential the chamber centerline CC. For example, the fuel sprays may comprise three plumes or four plumes.

    [0024] In the sectional views of FIGS. 5A-5D, the pistons 100' and 100" are near TC locations in the bore and the combustion chamber 150 is near minimum volume. With reference to FIGS. 5A-5C, as the pistons approach each other at minimum volume, squish motion from between the peripheries of the piston end into the combustion chamber becomes stronger. This squish flow preferentially separates more where the bowl profiles are deeper (123' and 123") as compared to the shallower regions of the bowls (A' and A"). This preferential flow separation sets up a rotational structure 176 circulating around the combustion chamber centerline CC. As can be seen, the rotational structure circulates transversely to the swirl axis, which is generally collinear with the cylinder axis 152: the structure 176 is therefore tumble. The strength of this tumble motion increases as the disposition of the deepest portions of the opposed bowls increases. The generation of this tumble motion is useful to ensure the diffusion plumes resulting from ignition of the fuel sprays emanating from the opposing injectors are centered in the combustion chamber, thus minimizing heat rejection to the combustion chamber walls.

    [0025] Tumble motions 178 are also set up in the orthogonal cut plane shown in FIG. 5D. These tumble motions may result from a number of sources, such as interaction of swirl and squish motions, residual tumble in the cylinder from the scavenging process, and the interactions of the charge motion with fuel sprays. They have less of an effect on the performance and emissions characteristics of the engine, as the dominant factor in this longitudinal section is the momentum arising from fuel injection.

    [0026] It is noted that the deepest parts of the bowls could be offset from the centerline midpoint M. With reference to FIG. 5D, for instance, for each bowl 108' and 108", the deepest part of the bowl may be closer to a respective one of the injectors 165. For example the maximum depth of the bowl 108' may be located between the midpoint M and the left hand injector 165, while the maximum depth of the bowl 108" may be located between the midpoint M and the right hand injector 165. This proximity of the deepest part of the bowl to an injector has the potential for benefits with respect to reducing plume impingement on the bowls early in the combustion process and minimizing heat rejection to the bowl trench regions later in the combustion process. Reducing heat rejection to the bowl trench regions may further reduce coolant flow rates, thereby improving engine brake specific fuel consumption.

    [0027] Although principles of piston and combustion chamber constructions have been described with reference to presently preferred embodiments, it should be understood that various modifications can be made without departing from the described principles. Accordingly, the scope of patent protection accorded to these principles is limited only by the following claims.


    Claims

    1. A two-stroke cycle, compression ignition, opposed-piston engine including at least one cylinder with a bore, piston-controlled exhaust and intake ports near respective ends of the cylinder, and a pair of pistons disposed in opposition in the bore, each piston comprising:

    a flat end surface (108) with an elongated, concave bowl (120) formed therein to define a combustion chamber with an elongated bowl formed in a flat end surface of an opposing piston; wherein

    the flat end surface (108) meeting a piston sidewall at a peripheral edge (110) having a circular shape that is centered on a longitudinal axis (112) of the piston (100) and that is disposed at a single longitudinal level of the piston;

    a pair of notches (118) formed in the end surface and positioned in opposition on the peripheral edge, in alignment with an end surface diameter (122);

    the concave bowl having an oblong shape that is elongated along the end surface diameter, between the notches;

    the concave bowl being flanked on either side by flat end surface portions (108a and 108b) that extend to the peripheral edge;

    the concave bowl having opposing sidewalls (123 and 124) and a curved bottom portion (125) which connects the sidewalls smoothly in a vertical section; and,

    a maximum depth (Dmax) of the bowl being the maximum distance between the curved bottom portion (125) and an end surface plane (PES), the plane (PES) intersecting the piston longitudinal axis and being positioned at the single longitudinal level, the maximum depth (Dmax) of the bowl being offset in an orthogonal direction from a longitudinal cut plane (PL), the plane (PL) containing the piston's longitudinal axis and the diameter (122), the planes (PL) and (PES) being mutually orthogonal, the engine further including

    a combustion chamber with an elongated, rotationally skewed shape formed between the flat end surfaces of the pistons when the pistons are near top center locations in the bore;

    two fuel injectors disposed in diametrical opposition and in alignment with a centerline of the combustion chamber;

    in a first longitudinal section, the combustion chamber having a rotationally skewed shape that is symmetrical with respect to the combustion chamber centerline; and,

    in a second longitudinal section that is orthogonal to the first longitudinal section, the combustion chamber having an elongated shape with opposite end portions that taper along the combustion chamber centerline toward the fuel injectors.


     
    2. The opposed-piston engine of claim 1, in which each fuel injector is constructed to emit a fuel spray with three or four plumes.
     
    3. A method for operating a two-stroke cycle, compression ignition engine according to claim 1, by:

    introducing swirling charge air into the cylinder between end surfaces of the pistons;

    moving the pistons toward each other in a compression stroke; and,

    forming a combustion chamber between end surfaces of the pistons, the combustion chamber having:

    a rotationally skewed shape in a first longitudinal section that is symmetrical with respect to the combustion chamber centerline; and,

    an elongated shape in a second longitudinal section that is orthogonal to the first longitudinal section with opposite end portions that taper along the combustion chamber centerline toward the fuel injectors; and,

    injecting opposing fuel sprays into swirling charge air in the combustion chamber through the opposing openings.


     
    4. The method of claim 3, wherein each spray pattern has either three plumes or four plumes.
     


    Ansprüche

    1. Zweitakt-Gegenkolbenmotor mit Kompressionszündung, aufweisend mindestens einen Zylinder mit einer Bohrung, eine kolbengesteuerten Abluft- und einer Ansaugöffnung nahe jeweiligen Enden des Zylinders, und ein Paar Kolben, die in der Bohrung einander gegenüberliegend angeordnet sind, wobei jeder Kolben umfasst:

    eine flache Endfläche (108) mit einer darin ausgebildeten langgestreckten, konkaven Wanne (120) zum Definieren einer Verbrennungskammer mit einer langgestreckten Wanne, die in einer flachen Endfläche eines gegenüberliegenden Kolbens gebildet ist; wobei

    die flache Endfläche (108) an einer Außenkante (110) mit kreisförmiger Form, die an einer Längsachse (112) des Kolbens (100) zentriert ist und auf einer einzelnen Höhe in der Längsrichtung des Kolbens angeordnet ist, auf eine Seitenwand des Kolbens trifft;

    ein Paar Kerben (118) in der Endfläche ausgebildet und einander gegenüberliegend an der Außenkante positioniert sind, ausgerichtet auf einen Durchmesser (122) der Endfläche;

    die konkave Wanne eine längliche Form aufweist, die entlang des Durchmessers der Endfläche zwischen den Kerben langgestreckt ist;

    die konkave Wanne an jeder Seite von flachen Endflächenabschnitten (108a und 108b), die sich zur Außenkante erstrecken, flankiert ist;

    die konkave Wanne gegenüberliegende Seitenwände (123 und 124) und einen gekrümmten Bodenabschnitt (125) aufweist, der die Seitenwände in einem vertikalen Schnitt glatt verbindet; und

    eine Maximaltiefe (Dmax) der Wanne der Maximalabstand zwischen dem gekrümmten Bodenabschnitt (125) und einer Endflächenebene (PES) ist, wobei die Ebene (PES) die Längsachse des Kolbens schneidet und auf der einzelnen Höhe in der Längsrichtung positioniert ist, wobei die Maximaltiefe (Dmax) der Wanne in einer orthogonalen Richtung von einer Längsschnittebene (PL) versetzt ist, wobei die Ebene (PL) die Längsachse des Kolbens und den Durchmesser (122) enthält, wobei die Ebenen (PL) und (PES) zueinander orthogonal sind,

    wobei der Motor ferner aufweist:

    eine Verbrennungskammer mit einer langgestreckten, in Drehrichtung abgeschrägten Form, die zwischen den flachen Endflächen der Kolben gebildet ist, wenn sich die Kolben in der Nähe von oberen mittigen Positionen in der Bohrung befinden;

    zwei Kraftstoffeinspritzdüsen sind diametral gegenüberliegend und auf eine Mittellinie der Verbrennungskammer ausgerichtet angeordnet;

    in einem ersten Längsschnitt weist die Verbrennungskammer eine in Drehrichtung abgeschrägte Form auf, die in Bezug auf die Mittellinie der Verbrennungskammer symmetrisch ist; und

    in einem zweiten Längsschnitt, der zu dem ersten Längsschnitt orthogonal ist, weist die Verbrennungskammer eine langgestreckte Form mit gegenüberliegenden Endabschnitten auf, die sich entlang der Mittellinie der Verbrennungskammer hin zu den Kraftstoffeinspritzdüsen verjüngen.


     
    2. Gegenkolbenmotor nach Anspruch 1, wobei jede Kraftstoffeinspritzdüse zum Abgeben eines Kraftstoffstrahls mit drei oder vier Rauchfahnen konstruiert ist.
     
    3. Verfahren zum Betreiben eines Zweitaktmotors mit Kompressionszündung nach Anspruch 1 durch:

    Einleiten von wirbelnder Ladeluft in den Zylinder zwischen Endflächen der Kolben;

    Bewegen der Kolben zueinander in einem Kompressionshub; und

    Bilden einer Verbrennungskammer zwischen Endflächen der Kolben, wobei die Verbrennungskammer aufweist:

    eine in Drehrichtung abgeschrägte Form in einem ersten Längsschnitt, die in Bezug auf die Mittellinie der Verbrennungskammer symmetrisch ist; und

    eine langgestreckte Form in einem zweiten Längsschnitt, der zu dem ersten Längsschnitt orthogonal ist, mit gegenüberliegenden Endabschnitten, die sich entlang der Mittellinie der Verbrennungskammer hin zu den Kraftstoffeinspritzdüsen verjüngen; und

    Einspritzen von entgegengesetzten Kraftstoffstrahlen in wirbelnde Ladeluft in der Verbrennungskammer durch die gegenüberliegenden Öffnungen.


     
    4. Verfahren nach Anspruch 3, wobei jedes Strahlmuster entweder drei Rauchfahnen oder vier Rauchfahnen hat.
     


    Revendications

    1. Moteur à pistons opposés, à allumage par compression, à deux temps, comprenant au moins un cylindre avec un alésage, des orifices d'échappement et d'admission commandés par piston près d'extrémités respectives du cylindre, et une paire de pistons disposés en opposition dans l'alésage, chaque piston comprenant :

    une surface d'extrémité plate (108) avec une auge concave allongée (120) formée à l'intérieur de celle-ci pour définir une chambre de combustion avec une auge allongée formée dans une surface d'extrémité plate d'un piston opposé ;

    la surface d'extrémité plate (108) rencontrant une paroi latérale de piston au niveau d'un bord périphérique (110) ayant une forme circulaire qui est centrée sur un axe longitudinal (112) du piston (100) et qui est disposé à un niveau longitudinal unique du piston ;

    une paire d'encoches (118) formées dans la surface d'extrémité et positionnées en opposition sur le bord périphérique, en alignement avec un diamètre de surface d'extrémité (122) ;

    l'auge concave ayant une forme oblongue qui est allongée le long du diamètre de surface d'extrémité, entre les encoches ;

    l'auge concave étant encadrée sur chaque côté par des parties de surface d'extrémité plates (108a et 108b) qui s'étendent sur le bord périphérique ;

    l'auge concave ayant des parois latérales opposées (123 et 124) et une partie inférieure incurvée (125) qui relie les parois latérales de manière lisse dans une section verticale ; et

    une profondeur maximale (Dmax) de l'auge étant la distance maximale entre la partie inférieure incurvée (125) et un plan de surface d'extrémité (PES), le plan (PES) coupant l'axe longitudinal de piston et étant positionné au niveau longitudinal unique, la profondeur maximale (Dmax) de l'auge étant décalée dans une direction orthogonale par rapport à un plan de coupe longitudinal (PL), le plan (PL) contenant l'axe longitudinal du piston et le diamètre (122), les plans (PL) et (PES) étant mutuellement orthogonaux,

    le moteur comprenant en outre :

    une chambre de combustion avec une forme allongée, inclinée en rotation formée entre les surfaces d'extrémité plates des pistons lorsque les pistons sont proches d'emplacements centraux supérieurs dans l'alésage ;

    deux injecteurs de carburant disposés en opposition diamétrale et en alignement avec une ligne centrale de la chambre de combustion ;

    dans une première section longitudinale, la chambre de combustion ayant une forme inclinée en rotation qui est symétrique par rapport à la ligne centrale de chambre de combustion ; et

    dans une seconde section longitudinale qui est orthogonale à la première section longitudinale, la chambre de combustion ayant une forme allongée avec des parties d'extrémité opposées qui s'effilent le long de la ligne centrale de chambre de combustion vers les injecteurs de carburant.


     
    2. Moteur à pistons opposés selon la revendication 1, dans lequel chaque injecteur de carburant est construit pour émettre un jet de carburant avec trois ou quatre panaches.
     
    3. Procédé faire fonctionner d'un moteur à allumage par compression, à deux temps selon la revendication 1, consistant à :

    introduire de l'air de suralimentation tourbillonnant dans le cylindre entre des surfaces d'extrémité des pistons ;

    rapprocher les pistons l'un de l'autre dans un cycle de compression ; et

    former une chambre de combustion entre des surfaces d'extrémité des pistons, la chambre de combustion ayant :

    une forme inclinée en rotation dans une première section longitudinale qui est symétrique par rapport à la ligne centrale de chambre de combustion ; et

    une forme allongée dans une seconde section longitudinale qui est orthogonale à la première section longitudinale avec des parties d'extrémité opposées qui s'effilent le long de la ligne centrale de chambre de combustion vers les injecteurs de carburant ; et

    injecter des jets de carburant opposés dans l'air de suralimentation tourbillonnant dans la chambre de combustion à travers les ouvertures opposées.


     
    4. Procédé selon la revendication 3, dans lequel chaque motif de jet a soit trois soit quatre panaches.
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description